Technical field

The present invention relates to a carrying out a method of compression cycle in a two-rotor, tooth, and screw compressor, which comprises suction of gas into the working space, an operation of poly tropic compression of the gas in the working space, and an operation of discharging the compressed gas from the working space into the discharge space. The invention further relates to a compressor for carrying out this method.

Background of the Invention

In the known two-rotor compressors, the gas compression is effected by feeding compressed gas from the adjacent working space of the second rotor and from the discharge line, i.e. including the discharge throat, into the working space in addition to the sucked-in gas, which is the so- called external compression.

Therefore, virtually all the compressed gas is fed into the working space through the same path through which it is discharged.

In comparison with the individual working spaces between the teeth of the compressor rotors, the volume of the discharge line is so large that after mixing, the gas pressure in the connected working space is basically identical to the pressure in the discharge line. Therefore, the compression ratio of poly tropic compression prior to the discharge of the gas from the working space and its contribution to the total compression is negligible. The theoretical pressure diagram in each working space is therefore almost rectangular in shape.

A similar result is obtained by compressing the gas in the known two-rotor compressors, in which the compressed gas is fed from both the adjacent working space of the second rotor and, mainly, the compressed gas is fed through a pressurizing line, sometimes cooled, after it is piped away from the discharge line, i.e. through a different path than how the discharge of gas from the working space into the discharge space is carried out. The compression ratio of poly tropic compression prior to the discharge of the gas from the working space and its contribution to the total compression is also negligible here.

In conventional two-rotor compressors, where the path for discharging compressed gas from the working space into the discharge space simultaneously serves as a path for feeding the compressed gas from the discharge space into the working space to compress the sucked-in gas, the two operations overlap, taking place simultaneously during the discharge stroke phase, i.e. during the reduction of the connected working space.

A disadvantage of this method of compressing the gas and of this embodiment of the compressor is also that the sucked-in gas is compressed by the hot gas from the discharge space, i.e. from the discharge throat and the discharge line, resulting in an elevated temperature of the discharged gas.

Certain types of these compressors, see patents GB 2157370, US 4215977, are, for the purpose of partially reducing pulsations, noise, and temperature, provided with internal grooves in the compressor cylinder or external ducts feeding gas from the discharge throat back into the compressor working space to partially or completely pre-compress the sucked-in gas before direct connection of the working space to the discharge throat and full compression of the sucked-in gas occur.

However, the opening of these grooves or ducts is opened into the working space even in the phase where the working space is connected to the discharge throat. Hence, the said grooves and ducts alternately serve both to compress the sucked-in gas and to discharge the gas, therefore, within them and within the discharge space, gas is constantly forced to flow alternately into and out of the compressor, which still requires increased energy consumption. The problem of compressing the sucked-in gas by hot compressed gas from the discharge throat space remains unsolved here too.

Many known two-rotor compressor solutions, see patents GB 1350636, US 5090879, US 6312240, GB 625490, WO 2015066479, are provided with a pair of lines through which the compressed air from the discharge line is fed from the side of the body into the working space to pre-compress the sucked in air, i.e., laterally pressurize it.

The solution of patent US 1746885 comprises a two-rotor, Roots compressor with a discharge valve, which is force-controlled according to the position of the rotor teeth, therefore, the maximum compression ratio is fixed here. In addition, the discharge valve is located downstream of the compressor discharge throat. The differentiation of paths for feeding compressed gas into the working space and for discharging the compressed gas from the working space to the discharge space is realized only inconsistently, namely by feeding the compressed gas into the working space of the first rotor not only from the working space of the second rotor but also from a portion of the discharge space, i.e. from the discharge throat, and is therefore largely fed through the same path through which it is discharged. The contribution of polytropic compression is therefore small here.

An automatic discharge valve is normally located in the discharge line, working as a check valve with the purpose to prevent the compressed gas from returning to the compressor, particularly when it is shut down. It contains relatively large inertia masses and is usually located downstream of the compressor discharge throat, meaning the volume of gas in the space from the working space boundary to the discharge valve may be many times greater than the volume of discharged gas in the working space itself, that is why it has virtually no positive effect on the efficiency of the compression cycle in the compressor.

U.S. pat. no. 3058652 includes a two-rotor, Roots compressor solution with a discharge valve for each rotor, wherein these valves extend significantly into the compressor working space and are force-controlled from the rotor shafts. Although polytropic compression takes place in the compressor, it does not take place within the entire compressor operating range but only within the fixed compression ratio with the possibility of automatic (and, therefore, also force- controlled) opening of the valves at a lower network pressure than that corresponding to the fixed compression ratio. When a situation arises in which the gas pressure in the discharge line needs to be maintained higher than the gas pressure in the compressor working space, after the connection of the working space to the discharge line, a shock external compression of the gas in the working space by the compressed gas from the discharge space necessarily occurs.

In piston compressors, at the top dead center of the piston in the loss space under the suction and the discharge valve, a portion of the gas remains that is not discharged by the discharge valve to the discharge space and expands polytropically during the return movement of the piston, thereby utilizing the energy of the compressed gas from the loss space but reducing the degree of filling of the working space with the sucked-in gas. Only after the gas pressure has been reduced by expanding from the loss space below the suction pressure value, the automatic suction valve opens and the working space fills with gas.

Tooth compressors or screw compressors have two rotors with two or more teeth and have individual working spaces delimited by the inner contour of the compressor body and the gaps between adjacent teeth of the intermeshed rotors. The intermeshing of the rotors creates one common working space from each interconnected pair of working spaces of the first and the second rotor. At the connection point of the suction and the discharge throat, the inner contour of the compressor body is interrupted and the rotor working spaces are opened for suction or discharge of gas.

In case of a tooth compressor, the discharge port is located axially, in case of a screw compressor, it is usually located radially, axially, or in combination.

These tooth or screw compressors are formed with a constant fixed, i.e. built-in, compression ratio, i.e. after suction, the gas is compressed polytropically in the working space of the intermeshed rotating rotors until the compressor working space is connected to the discharge throat space, wherein the relative positions of these spaces are fixed in the given compressor.

Ideally, at the time of connection of these spaces, the pressure in the compressor working space should be the same as the pressure in the discharge space, i.e. the discharge throat and the discharge line, and theoretically, the discharge of gas into the discharge line should continue incessantly.

In practice, however, the pressure in the discharge space is usually different from that in the working space, and gas mixing in these spaces occurs first.

If the gas pressure in the discharge space needs to be kept even slightly higher than the gas pressure in the compressor working space, a shock external compression occurs, i.e. the gas in the working space is compressed by the gas from the discharge space. Conversely, if the gas pressure in the discharge space is lower than the gas pressure in the compressor working space, throttling, i.e., a shock expansion of the gas in the compressor working space to the pressure value in the discharge space, occurs. These phenomena reduce the compression cycle efficiency. It is only after this mixing that the compressed gas is discharged into the discharge line.

In two-rotor, tooth, and screw compressors, the compression cycle efficiency is also impaired by the fact that a portion of the compressed gas is, due to the imperfect shape of the teeth, released at the end of the discharge between the rotors from the discharge side to the suction side of the compressor working spaces.

In case of certain screw compressors, the fixed compression ratio may be mechanically adjusted to a large extent by means of a sliding regulation slider on the discharge side, thereby minimizing the degree of external compression at varying network pressure values.

In terms of energy efficiency of the compression cycle, external compression is, in general, considerably less preferred than internal polytropic compression. Another disadvantage of the methods of compressing gas and embodiments of compressors with shock external compression during discharge and release of compressed gas into suction is that not only in the working space but also in the discharge line, particularly in the discharge throat, noisy pulsations - a violent, shock alternation of flow direction and thus a strong gas swirling - occur, which are associated with significant energy losses, which also cause higher temperature of the discharged gas than that which corresponds to the theoretical compression.

The price for the relative simplicity of the compression method, i.e. achieving the resulting pressure with external compression or a built-in compression ratio, is a reduced economy of compression in these compressors or a limited possibility of changing the pressure level in a network of appliances.

The main object of the invention is to reduce the energy consumption of the compression cycle in said compressors.

Summary of the Invention

The invention achieves this object with a method of carrying out a compression cycle in a two- rotor, tooth, and screw compressor that comprises suction of gas into the working space, an operation of poly tropic compression of the gas in the working space, and an operation of discharging the compressed gas from the working space into the discharge space, wherein the gas is guided in these operations through certain paths, characterized that at least a portion of the gas compression in the working space prior to the discharge is carried out polytropically with a compression ratio that varies according to the gas pressure in the discharge space.

There is no external compression by the gas from the discharge space in any event - during compression, backflow of the compressed gas from the discharge space into the working space is prevented by a discharge line and a discharge throat.

Preferably, in a tooth or a screw compressor, compression of gas in the working space is carried out polytropically with a compression ratio that

varies over the entire compressor operating range according to the gas pressure in the discharge space or

is fixed or adjustable in the first portion of the compressor operating range, and

in the next portion of the compressor operating range, it varies according to the gas pressure in the discharge space.

According to the invention, at least a portion of the compression in the compressor is effected by compressing the sucked-in gas by reducing the enclosed working space, i.e. generally polytropically, with a compression ratio that varies according to the gas pressure in the discharge space. Depending on the embodiment of the compressor, this occurs continuously and almost immediately.

The compressor operating range is the range of pressures for which the compressor is built.

This polytropic compression of the gas in the first variant, e.g. in a tooth or screw compressor, occurs in such a way that the whole poly tropic compression takes place according to the gas pressure in the discharge space, which is a preferred option for conditions where the pressure in the discharge space is variable and it cannot be guaranteed that it will not fall below a certain value.

In the following variant, e.g. in a tooth or screw compressor again, a portion of the polytropic compression is effected such that the first portion of the compression occurs with a constant or adjustable fixed compression ratio and the rest of the polytropic compression occurs according to the gas pressure in the discharge space, which is a preferred option for conditions where the pressure in the discharge space is variable and is higher than what correspond to a constant or adjustable fixed compression ratio.

Preferably, in a tooth or screw compressor, a portion of compression of the sucked-in gas in the working space may be carried out by feeding the compressed gas directly into the working space, through a path different from the path for discharging the compressed gas from the working space into the discharge space.

Preferably, e.g. in a two-rotor compressor, the first portion of compression of the sucked-in gas in the working space is carried out by feeding the compressed gas directly into the working space through a different path than the path for discharging the compressed gas from the working space into the discharge space, and the subsequent compression of the gas in the working space prior to the discharge is carried out polytropically with a compression ratio that varies according to the gas pressure in the discharge space, over the entire compressor operating range.

Feeding the compressed gas directly into the working space through a different path than the path for discharging the compressed gas from the working space into the discharge space is also referred to as pressurization.

If the compressed gas is fed directly into the working space through a different path than the path for discharging the compressed gas from the working space into the discharge space, it means that the compressed gas is fed into the working space through any path except for the path back from the discharge space, i.e. not only from the discharge line but also not from the discharge throat.

Feeding the compressed gas back from the discharge space directly into the working space refers to feeding the compressed gas directly into the working space through the same path as the path for discharging the compressed gas from the working space into the discharge space. The path for discharging the compressed gas from the working space into the discharge space comprises not only the discharge line but also the discharge throat.

The pressure of the compressed gas fed directly into the working space must be higher than the pressure of the gas in the working space.

It follows from the nature of the invention that the compressed gas (i.e., pressurizing gas) used for feeding directly into the working space for the purpose of compressing the gas already present in that space may be taken from the given compressor's own discharge space, or it may be supplied from an external source, and obtaining a gas mixture may, for example, serve a technological purpose. It is also clear from the nature of the invention that preferably, the compression cycle may also be used in underpressure operation. If the working gas is air, it may be compressed to atmospheric pressure level and the discharge space may be the ambient atmosphere.

Preferably, the compressed gas may be cooled prior to being fed into the working space. At least the portion of the discharged gas that is used to compress the sucked-in gas is, according to the invention, first cooled and only then fed into the working space. This reduces the discharged gas temperature and the compressor temperature. Cooling increases the density of the gas used to compress (pressurize) the sucked-in gas, which somewhat increases the energy consumption of the compression cycle.

However, the heat obtained by cooling the compressed gas fed into the compressor working space may be preferably used for practical purposes, preferably for heating and/or conversion to electricity, thereby reducing the total energy consumption of the compressor.

Preferably, the flow rate of the compressed gas fed into the working space may be regulated. By varying the suction volume and the overpressure of the gas, by regulating the flow rate of the compressed gas fed into the working space according to the invention, the refilling (pressurization) of the working space with the compressed gas may be adjusted in such a way so as to be distributed over period of time as long as possible.

Accumulation of discharged gas may be an advantage to further reduce pressure and flow rate unevenness.

The differentiation of paths for feeding the compressed gas directly into the working space and for discharging the compressed gas from the working space may be preferably realized in case of two-rotor, tooth, and screw compressors in such way that the compressed gas is fed into the working space of the first rotor through a separate external path and/or from the adjacent working space of the second rotor.

In a two-rotor compressor, in the discharge throat area, compressed gas from the working space of the second rotor is fed into the working space of the given rotor after the previous compression cycle.

If compressed gas from the discharge space is used for the pressurization, the discharge and pressurizing line, including any air tanks and heat exchangers, are substantially larger in volume than the volume of a single compressor working space, and, in addition, in case of a two-rotor compressor, the gas loss in the discharge line is compensated by the supply of gas from the working space of the second rotor. With pressurization, compression of the sucked-in gas may be achieved practically to the pressure value in the discharge line.

The invention also relates to a two-rotor, tooth, and screw compressor comprising a path for sucking gas into the working space and a path for discharging compressed gas from the working space, characterized in that the path for discharging the compressed gas from the working space is separated from the working space by at least one discharge valve.

Preferably, the compressor also comprises a path for feeding the compressed gas that leads directly to the working space and that is different from the path for discharging the compressed gas from the working space. The invention also relates to a two-rotor or tooth compressor, which is characterized in that the path for discharging the compressed gas from the working space is separated from the working space by at least one forced-controlled discharge regulation slider to adjust, regulate the built-in compression ratio. Preferably, the slider will be located axially, from the side of the compressor body, where the planar surface allows a simpler solution for sliding the closure plate and reducing the loss space.

In a two-rotor, tooth, and screw compressor according to the invention, the path for sucking gas into the working space, i.e. the suction line and the suction throat, may preferably be separated from the working space by at least one suction valve.

The valve in the compressor according to the invention may be force-controlled or automatic.

The valve is force-controlled if the movement of the valve plate is preferably mechanically, preferably electronically, derived from the movement of the rotors, wherein it is controlled so that over the entire compressor operating range, the compressed gas is not fed through the valve back into the working space from the discharge space.

By means of a force-controlled discharge valve or discharge slider, preferably a regulation one, preferably a sliding one, the fixed, built-in compression ratio may be adjusted, regulated to a large extent for the purpose of minimizing external compression and thereby ensuring economical operation of the compressor even at varying network pressure values.

The valve is automatic when the valve plate is actuated directly by the difference in gas pressure, preferably against the force of the spring.

Within this basic setting, a finer optimization of the opening and closing of the valve may be carried out by secondary regulation, preferably according to the instantaneous pressure ratios in the gas network.

Analogically, these principles apply to the slider as well.

By separating the working space from the discharge space by means of an automatic discharge valve, the backflow of compressed gas from the discharge space into the working space, i.e. the external compression of the gas in the compressor working space, is prevented very efficiently.

It is necessary to overcome not only the pressure of the gas in the discharge space but also the resistance of the discharge valve or the slider by poly tropic compression, and only then may the gas be discharged from the working space into the discharge space, i.e. into the discharge throat and then into the discharge line.

It is clear from the nature of the invention that the location of the discharge valve in the discharge throat must be in the immediate vicinity of the outer boundary of the working space, not beyond the flange of the discharge throat.

However, for design reasons, there is always a certain necessary size of the loss space in the case of every valve. In this regard, rotors with a smaller number of teeth are preferred in the case of a two-rotor compressor, therefore, two-teeth rotors are the most preferred, since this reduces the size of the loss space under the discharge valve relative to the size of the connected working space of the rotors.

These adjustments reduce the value of the resulting mixing pressure after the working spaces with the sucked-in and compressed gas have been connected, thereby increasing the contribution of poly tropic compression to the overall compression and thereby improving the energy efficiency of the compression cycle.

In compressor valves, it is necessary to take into account the aerodynamic and other losses caused, for example, by the automatic valves, depending on their shape, the force of the closing springs and due to the inertia of the moving portions as well as the compressor speed. In this respect, forced-controller valve or regulation slider usually cause smaller losses but at the cost of a complex and expensive mechanism to ensure their operation.

The design of the valve may be based on the known prior art design present in high-speed compressors, however, in the two-rotor, tooth, and screw compressor according to the invention, considerably less space is available for the placement of the discharge valve and the rotary valves are also subjected to centrifugal force.

The suction valve is located in the suction port, the discharge valve is located in the discharge port.

It is clear from the nature of the invention that the valve or regulation slider is located in the port directly on the boundary of the compressor working space.

Placing the valve in the port as close to the working space as possible reduces the loss space.

Preferably, the path for sucking or discharging gas is separated from the working space by at least two valves, preferably functionally independent of one another.

Preferably, the valves are arranged side by side in such manner that at least one valve is located above each rotor in each half of the throat cross-section, preferably, an equal number of valves is located in each half of the cross-section, in the rectangular cross-section of the compressor throat, it may be preferred if the valves are shifted relative to each other in the direction of the longitudinal axis of the compressor.

The valve preferably comprises at least two portions functionally independent of one another, which preferably comprise valve plates, preferably the valve plates being pivotable.

The valve plates may be reinforced by longitudinal undulations and a raised rim circumferentially to increase the rigidity of the shape.

Increasing the number of valves together with reducing their dimensions reduces gas discharge or suction unevenness and minimizes losses caused by gas ingressing through the gaps between the valves and rotor teeth.

In the compressor according to the invention, the discharge valve is preferably arranged such that its contour surface on the side of the working space of the rotors forms an equidistant to the peripheral rotary surface of the rotors, as well as an equidistant valve.

Preferably, the design of the valve in the compressor may be such that the clearance between the valve and the rotors is of the same order as the clearance between the compressor body and the rotors.

In the valve space, losses caused by compressed gas ingress due to clearance around the rotor teeth are minimized and are of the same order, i.e. comparable to the losses in the other space between the compressor body and the rotors, which has the preferred result of not only reducing the loss space under the valve but also, in another effect, allowing the reduction of the energy consumption of the compression cycle.

Preferably, the location of the discharge valves in the discharge throat may be curved along the compression path of the working space.

This limits the fixed portion of the compression ratio to a minimum and the compressor may continuously adapt to almost any change in the network pressure ratios while maintaining polytropic compression.

Similarly, the location of the suction valves in the suction throat may be curved along the suction path of the working space to ensure the best possible suction continuity.

Thus, in the compression cycle, the pressure energy of the portion of the compressed gas that is, at the end of a discharge due to the imperfect shape of the compressor rotor teeth, transferred between the rotors from the discharge side to the suction side of the compressor working spaces may be utilized.

If an automatic suction valve is used, the suction of gas into the tooth compressor may take place in the following way:

- the suction throat is interconnected to the compressor working space, the rotation of the rotors increases the volume of the working space, the suction valve is opened by the underpressure in the working space, and gas is sucked into the working space,

- the subsequent enclosed working space formed between the teeth of the rotors and containing the remaining portion of the compressed gas that has not been discharged into the discharge space approaches the suction throat by rotation of the rotors,

- by rotating the rotors, this subsequent enclosed working space opens, the remaining portion of the compressed gas is suddenly mixed with the sucked-in gas in the connected working space under the suction valve,

- when the compressed gas is mixed with the sucked-in gas, the pressure in the connected working space increases and, due to the increased pressure against the gas in the suction throat, the suction valve closes automatically,

- the rotation of the rotors causes the volume of the working space to increase and the gas in this space expands polytropically,

- further rotation of the rotors causes the volume of the working space to increase and the suction valve is automatically opened by the created underpressure and the suction of gas into the working space continues.

Preferably, the suction port with the suction valve is moved into the working space area where the pressure in the working space is equal to the pressure in the suction space after expansion of the released compressed gas. This reduces the risk of the compressed air expanding into the suction space.

The discharge or suction ports are preferably located axially from the side of the compressor body so that the discharge or suction is directed parallel to the rotation axis of the rotors.

If the valve is partially or completely covered by a rotor tooth when the rotor is rotating, the equilibrium of forces acting on the valve plate changes and the automatic valve closes partially or completely. Thus, the stable valve opens and closes each time it is covered with a rotor tooth.

This disadvantage is solved by the preferred arrangement of the compressor where the discharge and/or suction valves are connected to the rotor so that they rotate together with it, i.e. at least one separate discharge and/or suction valve is permanently available for each working space between the teeth. The valves are not overlapped by the rotor teeth, and each valve carries out one opening and closing cycle at each rotor revolution.

For design reasons, the sidewall on the discharge and suction side of the compressor may be provided with rotary valves always in the case of only one of the rotors. However, this is not an obstacle to functionality, since the interconnected working spaces of both rotors form a common working space, and therefore, in the case of the second rotor, the sidewall may be provided with only stable valves. Further embodiment variants result from the possibility that the sidewall on the suction side need not be provided with any suction valves, only with suction ports, and that the sidewall on the discharge side need not, in the case of the second rotor, be provided with any discharge valves, only with the discharge ports.

The rotary valves are preferably located in a separate disk that rotates in the sidewall of the compressor and abuts the lateral side of the rotors. Minimum clearance must be maintained between the rotary disk and the sidewall so as to allow rotation of the disk while preventing unwanted ingress of compressed or sucked-in gas.

According to a particular preferred embodiment of the compressor, ports may be created in the sidewall or in the rotary disk in which the valves need not necessarily be located.

Preferably, the rotary valves are designed as vane valves. Preferably, the spring vanes are attached to the rotor on the inner rotation radius and the valve plate on the outer rotation radius to take advantage of the stabilizing effect of the centrifugal force. Preferably, in the case of a given rotor, all of the vanes are made of one piece of material.

The two-rotor, tooth, or screw compressor may preferably be provided with stable deflectors in the discharge throat area to direct the flow of gas exiting the rotating working spaces and the rotating discharge valves into the discharge throat.

Preferably, these deflectors have a rotary design, they are preferably connected to a compressor rotor, they are preferably connected to a rotary disk that carries discharge valves. They direct the gas to flow in the direction opposite to the direction of rotation of the rotor. The gas flow velocity in the deflectors is subtracted from the peripheral velocity of the deflectors, and as a result, the deflectors slow the rotation of the exiting gas in the discharge throat and thus act as blades of a gas axial turbine. The rotary disc with the discharge valves and reflectors thus forms a gas turbine. As a result, a portion of the kinetic energy of the exiting rotating gas is used for conversion into mechanical energy, preferably to drive the compressor, for example, to cover losses from the gas flow in the discharge valves.

The two-rotor, tooth, or screw compressor may also preferably be provided with deflectors in the suction throat space to direct the flow of the sucked-in gas from the suction throat space to the direction of rotation of the rotating working spaces and the rotating suction ports in which the suction valves may be located.

Preferably, these deflectors have a rotary design, preferably are connected to a compressor rotor, preferably are connected to a rotary disk with formed suction ports. The deflectors here have the opposite purpose to the turbine on the discharge side of the compressor - they take up the gas fed by the suction throat, accelerate it, and feed it, push it into the rotating suction ports. Therefore, they act as turbocharger blades. Energy is needed to direct and accelerate gas movement, but the overpressure of the gas at the outlet of the turbocharger may be used for faster, more intense filling, supercharging of the rotating compressor working spaces with the sucked-in gas, and covering losses from gas flow in the suction ports or suction valves.

In general, the deflectors may preferably be tilting to provide optimum flow rate in the event of a change in flow in the case of change in speed, the delivered amount, or the pressure ratios. The deflectors preferably have an aerodynamic profile.

The two-rotor, tooth, or screw compressor according to the invention preferably comprises an external separate pressurizing line, through which compressed gas is fed directly into the working space of the given rotor.

In a two-rotor compressor, it is preferred to have a separate compressed gas supply (pressurizing line) available for each rotor.

Tooth and screw compressors may be provided with one pressurizing line common to both rotors. However, it may be preferred to use a separate pressurizing line for each rotor for the purpose of more accurate filling of the working spaces.

In the two-rotor, tooth, or screw compressor with two- or three-tooth rotors according to the invention, the unevenness of the gas flow, shock phenomena, and the temperature of the discharged gas is reduced, but only partially, as an important feature of the invention, i.e. separating the paths for feeding and discharging the compressed gas, cannot be easily and consistently applied here.

If the paths for discharging and pressurizing the gas are opened into the compressor body too close to each other, i.e. their separation is not performed consistently, then the unevenness of the gas flow, the shock phenomena, and the temperature of the discharged gas is reduced only partially. In the final compression phase, the gas could also tend to flow in the opposite direction, i.e. out of the working space into the pressurizing line.

It is because a relatively large pitch of the working spaces due to a small number of rotor teeth could lead to the gas tending to flow in the opposite direction, i.e. out of the working space into the pressurizing line, in the final compression phase. A relatively small angular distance between the discharge throat and the opening of the path for feeding the compressed gas into the working space in the case of the two- or three-tooth rotors makes it impossible to regulate this feeding of the compressed gas at all or not sufficiently well.

In such case, preferably, at least the backflow of gas in the path for feeding the compressed gas into the working space may be prevented by placing a check valve or a swing check valve in that path, preferably as close to the working space as possible, to minimize the amount of gas whose movement is reversed in this path, but at the expense of losses caused by gas flow resistance.

A preferred embodiment of the invention is such a two-rotor, tooth, or screw compressor whose essence is that the port of the throat for feeding the compressed gas into the working space is at least one tooth pitch of the rotor away from both the suction throat port and the discharge throat port.

The port of the line for feeding the compressed gas directly into the working space is situated here in such a way that it cannot be interconnected by the space between the rotor teeth to either the suction or the discharge port and thus undesired loss gas flow cannot occur.

An external separate path may be created in this compressor for feeding the compressed gas into the working space that is different from the path for discharging the compressed gas from the working space.

Even a compressor having a proper pressurizing throat location preferably also comprises a check valve or a swing check valve located in the pressurizing line as close to the working space as possible to prevent reverse pulsations of gas from the working space into the line if these pulsations are not sufficiently limited by the flow rate regulator itself.

The path for feeding the compressed gas directly into the working space, preferably constituted by the pressurizing throat and the pressurizing line, preferably comprises a cooler and/or a flow rate regulator.

Accordingly, a preferred embodiment of the invention is a two-rotor or screw compressor whose rotors have at least four teeth.

In simplified terms, the compression cycle in this two-rotor compressor with a pressure line and a discharge valve according to the invention occurs, as the rotors gradually rotate, as follows:

1 - gas is sucked into the working space from the suction space,

2 - subsequently, a portion of the cooled discharged gas is fed from the discharge space through a special path (through the pressurizing line) into the working space by regulated throttling, by means of which the sucked-in gas is compressed (pressurized) to a resulting, almost discharge, value (due to the piping away of a portion of the compressed gas to be pressurized, the gas pressure in the discharge line must be slightly reduced),

3 - by rotating the rotors, the supply of the compressed gas through the pressurizing line into the working space is interrupted,

4 - by rotating the rotors, in the area of the discharge throat, the working space of the first rotor containing the sucked-in gas is connected to the working space of the second rotor where there is compressed gas that is discharged into the discharge line,

5 - the gas pressures in the connected working space are equalized, i.e. the sucked-in gas is compressed (pressurized) to the resulting mixture pressure value, while the original compressed gas is throttled to this resulting mixture pressure value,

6 - due to a pressure drop in the connected working space, the discharge valve closes and the previous gas discharge into the discharge line is terminated,

7 - by rotating the rotors, polytropic gas compression to the pressure value in the discharge line occurs in the connected working space due to its reduction, the discharge valve remains closed,

8 - by rotating the rotors, the discharge valve is opened by the overpressure in the connected working space, and by continuous reduction of the connected working space, compressed gas is discharged into the discharge line in an amount corresponding to the gas sucked in and pressurized into the working space of the first rotor;

9 - by rotating the rotors, the next working space of the second rotor is connected to the discharge throat, the discharge valve closes due to the pressure drop in the connected working space and thus the discharge is terminated,

10 - a portion of the discharged gas is cooled and transferred to be re-used for compressing the sucked-in gas in the next compression cycle,

11 - the remaining portion of the discharged gas equal to the sucked in amount is piped away for consumption,

12- after all gas has been discharged, the working space is reconnected to the suction space.

Thus, from the point of view of each working space, two concurrent gas flows intersect in the compressor:

- a continuous flow of sucked-in gas from the suction space through the working space into the discharge space, and

- a flow of gas circulating from the working space into the discharge space and, after possible cooling, back into the working space.

The compression cycle consists of two concurrent partial processes:

a) open process of sucked in (= sent) gas:

- suction at suction pressure,

- compression (pressurization) by mixing with the compressed gas with a pressure increase to the resulting mixing value,

- polytropic compression to the discharge pressure value,

- discharge at discharge pressure value;

(b) closed process of circulating gas:

- cooling of compressed gas,

- throttling by mixing with the sucked-in gas to the resulting mixing value,

- polytropic compression to the discharge pressure value,

- discharge at discharge pressure value.

The compression cycle in the case of a two-rotor compressor with differentiation of paths for feeding compressed gas into the working space and for discharging compressed gas from the working space and with separation of the compressor working space from the discharge throat by the discharge valve according to the invention may preferably be realized such that the compressed gas is fed into the working space of the first rotor only from the working space of the second rotor.

In the discharge throat area, only the working space of the first rotor, where the sucked-in gas with the initial pressure is located, and the working space of the second rotor, where the compressed gas with the outlet pressure is located, are connected. The resulting pressure and temperature after mixing the two amounts of gas in the connected working space are higher than the pressure and temperature of the sucked-in gas but lower than the pressure and temperature of the gas in the discharge line.

It is because of the fact that due to the reduction of gas pressure in the connected working space, the discharge valve blocks the path for discharging gas from the connected working space into the discharge line to prevent backflow of compressed gas from the discharge line into the connected working space.

Therefore, the polytropic compression of this gas mixture must take place in the connected working space up to the pressure level in the discharge line, and only then may the gas continue to be discharged from the working space into the discharge line.

Since approximately half of the gas compression is polytropic, the compression work in this compression cycle is smaller than in the original cycle.

Compressed gas is used to compress the sucked-in gas in the working space of the first rotor, which passes from the adjacent working space of the second rotor by throttling and which thus cannot be cooled externally, which affects the resulting temperature of the discharged gas.

Nevertheless, the unevenness of the gas flow, the shock phenomena, and the energy consumption of the compressor are reduced by this compression cycle according to the invention.

Especially when using an automatic discharge valve in the two-rotor compressor according to the invention, it is achieved that the poly tropic portion of the gas compression in the working space is carried out with a compression ratio which automatically and continuously varies according to the required gas pressure value in the discharge space, and over the entire compressor operating range, the compression is carried out without reverse-feeding the compressed gas into the working space from the discharge space.

In principle, in this two-rotor compressor, the compression cycle occurs as follows:

1 - by rotating the rotors, the working space of the first rotor is increased, this way, gas is sucked into this working space by the suction line,

2 - by rotating the rotors, connection of the working space of the first rotor to the suction line is interrupted,

3 - by rotating the rotors, in the area of the discharge throat, the working space of the first rotor containing the sucked-in gas is connected to the working space of the second rotor where there is compressed gas being discharged into the discharge line,

4 - the gas pressures in the connected working space are equalized, i.e. the sucked-in gas is compressed (pressurized) to the resulting mixture pressure value, while the original compressed gas is throttled to this resulting mixture pressure value,

5 - due to a pressure drop in the connected working space, the discharge valve automatically closes and the previous gas discharge into the discharge line is terminated,

6 - by rotating the rotors, polytropic gas compression to the pressure value in the discharge line occurs in the connected working space due to its reduction, the discharge valve remains closed,

7 - by rotating the rotors, the compressed gas overcomes, by the overpressure, the resistance of the discharge valve, which opens, and by continuous reduction of the connected working space, compressed gas is discharged into the discharge line in an amount corresponding to the gas sucked into the working space of the first rotor,

8 - by rotating the rotors, the next working space of the second rotor is connected to the discharge throat, the discharge valve closes due to the pressure drop in the connected working space and thus the discharge is terminated,

9 - by rotating the rotors, the connection of the working space of the first rotor to the discharge throat is terminated,

10 - by rotating the rotors, the working space of the first rotor connects to the suction line.

Simultaneously with the shift by the tooth pitch, an analogous compression cycle with the gas sucked into the working space of the second rotor occurs in the compressor.

The compression cycle in a two-rotor compressor when using a pair of automatic equidistant discharge valves occurs somewhat differently, fundamentally as follows:

1 - by rotating the rotors, the working space of the first rotor is increased, this way, in the suction throat area, gas is sucked into this working space from the suction line,

2 - by rotating the rotors, connection of the working space of the first rotor to the suction throat is interrupted,

3 - by rotating the rotors, the working space of the first rotor is connected in the discharge throat area to the first discharge valve space,

4 - by rotating the rotors, due to the low pressure (substantially at the suction pressure level), the first discharge valve remains closed in the working space of the first rotor under the first discharge valve after a previous pressure drop in the connected working space,

5 - by rotating the rotors, the working space of the first rotor rotates to the central plane between the valves,

6 - by rotating the rotors, the working space of the first rotor is interconnected to the sucked-in gas and the adjacent working space of the second rotor to the compressed gas, the resulting mixing pressure in the connected working space drops below the output pressure value, and the discharge valve at the second rotor is also closed automatically, the gas discharge into the discharge line is terminated,

7 - by rotating the rotors, polytropic gas compression to the pressure value in the discharge line occurs in the connected working space due to its reduction, both discharge valves remain closed,

8 - by rotating the rotors, the first discharge valve is opened by the overpressure, and by continuous reduction of the connected working space, compressed gas is discharged into the discharge line in an amount corresponding to the gas sucked into the working space of the first rotor,

9 - by rotating the rotors, the working space of the second rotor is rotated to the central plane between the valves,

10 - by rotating the rotors, the working space of the second rotor is connected to the working space of the first rotor, the first discharge valve is closed due to the pressure drop in the connected working space and thus the discharge is terminated,

11 - by rotating the rotors, the connection of the working space of the first rotor to the discharge throat is terminated,

12 - by rotating the rotors, the working space of the first rotor is again connected to the suction throat area.

Simultaneously with the shift by the tooth pitch, an analogous compression cycle with the gas sucked into the working space of the second rotor occurs in the compressor.

In the case of this compressor, the working spaces of both rotors are connected during operation 6, wherein the working space of the first rotor with the sucked-in gas has a full volume, while the working space of the second rotor with the compressed gas is already considerably reduced after the previous discharge. The resulting mixing pressure is therefore lower in the case of this compressor than in the case of a compressor with a single common discharge valve. Thus, the compression ratio during polytropic compression of gas to outlet pressure is higher and the energy efficiency of this compression cycle is also higher. The said effect also depends on the arrangement and design quality of the compressor rotors, it is probably more favorable with a smaller number of rotor teeth.

The method according to the invention may also be used for a piston compressor that comprises a path for feeding compressed gas, which leads directly into the working space and is different from the path for discharging compressed gas from the working space, which is separated from the working space by at least one automatic discharge valve.

The path for feeding the compressed gas directly into the working space, i.e. the compressor cylinder, which is different from the path for discharging the compressed gas from the working space, preferably opens into the cylinder at the bottom dead center of the piston. The cylinder is provided here with at least one pressurizing port which is uncovered and concealed by the piston, i.e. opened and closed.

Although the piston compressor according to the invention cannot carry out compression more efficiently than a conventional piston compressor, its use is preferred for other purposes - for example, by changing the position of the opening of the line for feeding compressed gas relative to the dead centers of the compressor or by regulating the flow rate and cooling the fed compressed gas, it may be used to simulate and examine the various variants of the compression cycle according to the invention in view of the fundamental similarity of this compressor to the two-rotor compressors according to the invention. The discharge valve may be of any embodiment.

This compressor is suitable for the simulation and examination of the compression cycle according to the invention particularly for the following reasons:

- thermodynamic changes of component, partial semiparallel gas circulations that accumulate in a two-rotor compressor in a small space in the space between the teeth and occur simultaneously for a very short period of time both for design reasons and due to high speed may occur in the compressor in question in a considerably slower manner, therefore, they may be examined (defined, set, tracked, and evaluated) much more precisely, especially if the compressor is a slow-running one,

- the interconnection of individual portions of the compressor may easily be changed for the purpose of simulating the proposed variants of the compressors and their corresponding compression cycles,

- the level of wear, in particular the compressor leakage, may also be easily simulated, which allows to realistically approximate the two-rotor compressor operating conditions in terms of volume and mechanical efficiency.

Advantages of the invention:

- unwanted external gas compression and its negative consequences, i.e. gas flow unevenness, discharged gas temperature, and noise, may be reduced in compressors,

- the built-in portion of the compression ratio may be limited in compressors,

- compressors may continuously adapt to almost any change in network pressure ratios while maintaining polytropic compression,

- the energy consumption of compressors may be reduced, - individual compressors may be usable for a larger range of operating gas pressures, thereby limiting their product range.

Brief Description of Drawings

The invention will be clarified in more detail using the example embodiments according to the appended drawings:

Fig. 1 shows a diagram of a two-rotor compressor with a discharge valve,

Fig. 2 shows a p-V diagram of a theoretical compression cycle of a two-rotor compressor with a discharge valve,

Fig. 3 shows two diagrams of a two-rotor compressor with an equidistant discharge valve,

Fig. 4 shows a p-V diagram of a theoretical compression cycle of a two-rotor compressor with an equidistant discharge valve,

Fig. 5 shows a diagram of a prior art two-rotor compressor with pressurization and a discharge valve,

Fig. 6 shows a diagram of a two-rotor compressor with rotary discharge valves,

Fig. 7 shows a diagram of a two-rotor compressor assembly with pressurization and a discharge valve,

Fig. 8 shows a diagram of a sidewall of a screw compressor with stable discharge valves,

Fig. 9 shows a diagram of a screw compressor with stable and rotary valves,

Fig. 10 shows a diagram of a screw compressor with pressurization,

Fig. 11 shows a diagram of a screw compressor assembly with pressurization,

Fig. 12 shows a diagram of a tooth compressor with stable suction and discharge valves,

Fig. 13 shows a diagram of a tooth compressor with stable suction valves and rotary discharge valves,

Fig. 14 shows a diagram of a tooth compressor with a suction valve and stable discharge valves, Fig. 15 shows a diagram of a tooth compressor with rotary suction and discharge valves,

Fig. 16 shows a diagram of a piston compressor assembly with pressurization,

Fig. 17 shows a diagram of a cylinder with pressurizing ports.

Example embodiments of the invention

Fig. 1 shows a diagram of a two-rotor compressor with a discharge valve. A discharge valve 13b is located in the discharge throat 6 to prevent the reverse ingress of compressed air from the discharge throat 6 into the connected working space 3. The valve 13b has two thin pivotable plates 15b, which are pushed into the closed position by the force of overpressure of air from the discharge throat 6 and by the force of the spring 16b and tilted by the overpressure of air from the connected working space 3 against the force of the spring 16b. In position A, the discharge valve 13b is shown in the closed position, in position B, it is shown in the open position.

The pivotable plates 15b of the valve 13b extend as deeply into the discharge throat 6 as possible, close to the rotating teeth of the rotors 2a, 2b, thereby reducing the loss space under the discharge valve 13b, and are located obliquely to the air flow from the connected working space 3 into the discharge throat 6, thereby reducing aerodynamic drag. Although the two pivotable plates 15b of the valve 13b are functionally independent of one another, they open and close simultaneously during the compression cycle due to the relatively large loss space under the valve 13b. In the area of the discharge throat 6, connection of the working space 3a of the left rotor 2a containing the sucked in air to the adjacent working space 3b of the right rotor 2b containing the compressed air occurs. At the moment of the pressure drop during the mixing of the contents in the connected working space 3, the discharge valve 13b is closed by the overpressure from the discharge throat 6 and by the force of the spring 16b. By rotating the rotors 2a. 2b, polytropic compression occurs in the connected working space 3 due to the reduction of this connected working space 3 to the pressure value in the discharge throat 6, further rotation of the rotors 2a, 2bcauses the discharge valve 16b to open by the overpressure from the connected working space 3, and the compressed air corresponding to the sucked in amount is discharged into the discharge throat 6. This process proceeds analogously alternately with the working spaces 3a. 3b of the left rotor 2a and the right rotor 2b.

Fig. 2 shows a p-V diagram of a theoretical compression cycle of an air two-rotor compressor with a discharge valve 13b of Fig. 1. The theoretical compression cycle may be described by the following sequence of thermodynamic changes:

1-2 ... suction of cold air from the atmosphere into the working space 3a of the left rotor 2a from volume Vi to volume V2 at a constant pressure pi,

2-3 ... mixing the sucked in air at pressure pi with compressed air from the working space 3b of the right rotor 2b and from the loss space under the discharge valve 13b at pressure p4 to the resulting air mixing pressure p3 at a constant volume V2 of the connected working space 3;

3-4 ... polytropic air compression in the connected working space 3 from pressure p3 and volume V2 to pressure p4 and volume V4,

4-5 ... discharging compressed air from the connected working space 3 from volume V4 to volume Vi at a constant pressure p4,

5 - 1 ... throttling the compressed air from pressure p4 to the level of atmospheric pressure pi at a constant volume Vi.

With the size of the loss space of 10% of one working space 3, the mixing pressure p3 reaches about 52% of the difference between the pressure p4 = 0.24 MPa of the compressed air and the pressure pi = 0.1 MPa of the sucked in air. Theoretically, the saving of work is 11.4% here compared to the compression cycle of a conventional two-rotor compressor.

Fig. 3 shows two diagrams of a two-rotor compressor with an equidistant discharge valve 16b that prevents the compressed air from ingressing from the discharge throat 6 into the common working space 3. The valve 16b comprises two portions functionally independent of one another, has two thin pivotable plates 15b, which are pushed into the closed position by the force of overpressure of air from the discharge throat 6 and by the force of the spring 16b and tilted by the overpressure of air from the common working space 3 against the force of the spring 16b. The pivotable plates 15b open and close simultaneously or alternately depending on the overpressure in the area of the given pivotable plate 15b, since they are designed such that the clearance V2 between the pivotable plates 15b and the rotors 2a. 2b is of the same order as the clearance VI between the blower body 1 and the rotors. 2a. 2b. The loss space under this valve 16b is therefore substantially smaller than in the case of the embodiment of Fig. 1.

In the left diagram, the right pivotable plate 15b is in the closed position, the left pivotable plate 15b is in the open position, the compressed air is discharged into the discharge throat 6. The tooth of the right rotor 2b is oriented to the central plane of the valve 16b. By rotating the rotors 2a, 2b, connection of the adjacent working spaces 3a, 3b of both rotors 4a and 4b occurs. At the moment of the pressure drop during the mixing of the contents in the connected working space 3, the left pivotable plate 15b is closed by the overpressure from the discharge throat 6 and by the force of the spring 16b. The pressure drop here is higher than when the working spaces 3a, 3b of the compressor of Fig. 1 are connected because the working space 3a of the left rotor 2a containing the compressed air is about one third smaller in the given position than the working space 3b of the right rotor 2b containing the sucked-in gas and also because the loss space under the discharge valve 16b is relatively small. By rotating the rotors 2a. 2b, polytropic compression occurs in the connected working space 3 due to the reduction of this connected working space 3 to the pressure value in the discharge throat 6, further rotation of the rotors 2a. 2bcauses the right pivotable plate 15b to open by the overpressure from the connected working space 3, and the compressed air corresponding to the sucked in amount is discharged into the discharge throat 6.

The right diagram shows the situation after the discharge has been terminated. This process proceeds analogously alternately with the working spaces 3a. 3b of the left rotor 2a and the right rotor 2b.

Fig. 4 shows a p-V diagram of a theoretical compression cycle of an air two-rotor compressor provided with an equidistant discharge valve 16b with the minimum clearance V2 of Fig. 3. The theoretical compression cycle may be described by the following sequence of thermodynamic changes:

1-2 ... suction of cold air from the atmosphere into the working space 3b of the right rotor 2b from volume Vi to volume V2 at a constant pressure pi,

2-3 ... mixing the sucked in air at pressure pi with compressed air from the working space 3a of the left rotor 2a and from the loss space under the discharge valve 16b at pressure p4 to the resulting air mixing pressure p3 at a constant volume V2 of the connected working space 3;

3-4 ... polytropic air compression in the connected working space 3 from pressure p3 and volume V2 to pressure p4 and volume V4,

4-5 ... discharging compressed air from the connected working space 3 from volume V4 to volume Vi at a constant pressure p4,

5 - 1 ... throttling the compressed air from pressure p4 to the level of atmospheric pressure pi at a constant volume Vi.

If the size of the loss space is 2% of one working area 3a or 3b and the volume

V1-V0 of the working space 3a of the left rotor 2a is about 65% of the volume V2-V1 of the working space 3b of the right rotor 2b at the time of connection of these spaces 3a, 3b, the mixing pressure p3 will amount to about 40% of the difference between the pressure p4 = 2.4 MPa of the compressed air and the pressure pi = 0.1 MPa of the sucked in air. Theoretically, the saving of work is 14.8% here compared to the compression cycle of a conventional two-rotor compressor. This compression cycle is therefore 30% more energy efficient compared to the compression cycle of Fig. 6 because polytropic compression starts from a lower mixing pressure

P3.

Fig. 5 shows a diagram of a two-rotor rotary air compressor with pressurization. A total of 8 working spaces 3a, 3b are formed between the teeth of the pair of four-tooth rotors 2a, 2b and the compressor housing 1. The space between the discharge throat 6 port and the pressurizing throat 7a or 7b port is delimited by the angle a, which is about 92° here, which is greater than the angle of 90° formed by the teeth of the rotors 2a, 2b. The same ratios also apply to the space between the port of the suction throat 4 and the port of the pressurizing throat 7a or 7b. The port of the pressurizing port 7a or 7b for feeding compressed air into the working space 3a or 3b is therefore more than one tooth pitch of the rotor 2a, 2b away from the port of the suction throat 4 and the port of the discharge throat 6. This ensures that the compressed air cannot ingress through the working space 3a or 3b between the teeth of the rotor 2a, 2b from the pressurizing throat 7a or 7b into the suction throat 4 or from the discharge throat 6 into the pressurizing throat 7a or 7b.

Fig. 6 shows a diagram of a two-rotor compressor with rotary discharge valves. In the rear sidewall of the compressor, the rotary disk 18a, in which the automatic discharge valves 14b are seated, is connected to the left rotor 2a, and in the front sidewall of the compressor, the rotary disk 18b, in which the automatic discharge valves 14b are seated, is connected to the right rotor 2b. The suction throat 4 is common to both of the rotors 2a, 2b. Gas is sucked through the suction throat 4 into the working spaces 3a of the left rotor 2a and the working spaces 3a of the right rotor 2a. In the upper portion of the compressor in the common working space 3, the gas is poly tropically compressed and discharged through the discharge valves 14b into the discharge throat 6.

Fig. 7 shows a diagram of a two-rotor rotary air compressor assembly with pressurization and a discharge valve. By rotating the rotors 2a, 2b, air is sucked through the suction throat 4 into the working spaces 3a, 3b, by further rotation of the rotors 2a, 2b, it is transported to the pressurizing throats 7a, 7b, where the sucked in air is compressed by cooled pressurizing air from the pressurizing line 9a, 9b. The resulting amount of air in the working spaces 3a, 3b is, by further rotation of the rotors 2a, 2b, transported to the discharge throat 6, and from there, it is discharged through the discharge valve 13 into the discharge line 8. Compressed air is transported for consumption in an amount corresponding to the sucked in amount. Off of the discharge line 8, the pressurizing line 9a, 9b branches, through which the circulating portion of the compressed air is transferred to the coolers 10a, 10b and further through the regulation fittings 11a, l ib to the pressurizing throats 7a, 7b and the working spaces 3a, 3b for compressing the sucked in air in the next compression cycles.

Fig. 8 shows a diagram of a sidewall of a screw compressor with stable automatic discharge valves. The sidewall 17b on the discharge side of the compressor is provided with 15 stable discharge valves 13b of circular shape of two sizes and 2 discharge valves 13b of rectangular shape of uniform size. By gradually opening and closing the valves 13b during rotation of the rotors 2a, 2b, pressure fluctuations in the working spaces between the teeth are minimized. The sidewall 17b is provided with discharge valves 13b in the lower half only partially, that is why the basic portion of the compression ratio in the compressor is fixed and only the next compression takes place with a compression ratio that depends on the instantaneous gas pressure in the discharge space.

Fig. 9 shows a diagram of a screw compressor with stable and rotary valves. Rotary disks 18a, 18b are located in the sidewalls 17a, 17b at the lower rotor 2b on both the suction and the discharge side, wherein the automatic discharge valves 14b are seated on the discharge side in the rotary disk 18b. On the discharge side of the compressor, a turbine 19 is connected to the rotary disk 18b that uses the kinetic energy of the compressed gas exiting the rotating discharge valves 14b and slows the rotation, swirling of gas in the discharge throat 6b. On the suction side of the compressor, a turbocharger 20 is connected to the rotary disk 18a that directs the gas sucked from the suction throat 4a and pushes it into the suction ports 5a in the rotary disk 18a and further into the working spaces. In the sidewall 17a on the suction side of the upper rotor 2a, automatic suction valves 13a are located, which, by the underpressure in the working spaces during the suction phase, allow air to be sucked in from the suction throat 4. If the suction turbocharger 20 causes overpressure in the working spaces during suction, the automatic suction valves 13a will prevent unwanted leakage of compressed air from the working spaces through the upper rotor 2a into the suction throat 4.

In the sidewall 17b at the upper rotor 2a on the discharge side, a stable automatic valve 13b is located that opens into a common discharge throat 6b. By optimizing the size and number of the discharge valves 13b, 14b at both rotors 2a, 2b, it is possible to further reduce the unwanted leakage of compressed air from the discharge side of the working spaces to the suction side of the working spaces. The compressor may perform compression at virtually the entire overpressure working range with a compression ratio that automatically adapts to the instantaneous gas pressure in the discharge space.

Fig. 10 shows a diagram of a screw compressor with pressurization. The port of any pressurizing throat 7a, 7b is more than one tooth pitch 2J_, 22 of the rotor 2a, 2b away from the discharge port 5b of the discharge throat 6. There are no discharge valves located in the discharge ports 5b. The compressor performs basic compression with a built-in compression ratio and further increases the pressure to a value practically equal to that in the discharge throat 6, and may be carried out in the discharge line by pressurizing with compressed gas fed through the pressurizing throat 7a, 7b from the discharge line for possible cooling in a cooler.

Fig. 11 is a diagram of an air screw compressor assembly with pressurization. By rotating the rotors 2a, 2b, air is sucked through the suction throat 4 into the working spaces 3a, 3b, by further rotation of the rotors 2a, 2b, it is poly tropically compressed to a basic pressure corresponding to the built-in compression ratio and transported to the pressurizing throats 7a, 7b, where the air is then compressed by cooled pressurizing air from the pressurizing line 9a, 9b, in which the air pressure is higher than the basic pressure in the compressor. The resulting amount of air in the working spaces 3a, 3b is, by further rotation of the rotors 2a, 2b, transported through the automatic discharge valves 13b to the discharge throat 6 and from there into the discharge line 8. Compressed air is transported for consumption in an amount corresponding to the sucked in amount. Off of the discharge line 8, the pressurizing line 9a, 9b branches, through which the circulating portion of the compressed air is transferred to the coolers 10a, 10b and further through the regulation fittings 11a, l ib to the pressurizing throats 7a, 7b and to the working spaces 3a, 3b for compressing the sucked in air in the next compression cycles. Since the discharge valves 13b are automatic, the interconnection of the pressurizing throat 7a, 7b and the discharge throat 6 will be prevented for both rotors 2a, 2b, even if their peripheral or angular distance is smaller than the tooth pitch of the rotors 2a, 2b.

Fig. 12 shows a diagram of a tooth compressor with stable suction and discharge valves. In the compressor, the working spaces 3 are defined by the teeth of the rotors 2a, 2b and the compressor body 1. On the side of the left rotor 2a, three stable forced-controlled suction valves 12a are axially located in the suction throat 4, on the side of the right rotor 2b, four stable discharge valves 12b, also forced-controlled, are located in the discharge throat 6. Two compression cycles take place during one revolution of the rotors 2a, 2b. The figure shows a situation where the enclosed working space 3 between the teeth of the rotors 2a, 2b containing partially compressed gas from the initial compression phase is approaching the suction valves 12a, where the gas suction occurs by rotating the rotors 2a, 2b. This shows that during a compression cycle in the case of a tooth compressor, a relatively large amount of compressed gas is released from the discharge side of the working spaces to the suction side of the working spaces and that by using the suction valves 12a according to the invention, the efficiency of the compression cycle may be increased by using the pressure energy of the released compressed gas. The discharge valves 12b are forced-controlled with secondary regulation as a function of the pressure in the discharge space such that over the entire operating range of the compressor, compression is carried out without feeding the compressed gas from the discharge space back into the working space 3.

Fig. 13 shows a diagram of a tooth compressor with stable suction valves and rotary discharge valves. The two automatic rotary discharge valves 14b are connected to the right rotor 2b in such a way that they rotate together with it so that the two working spaces 3 between the teeth are permanently assigned to a separate rotary discharge valve 14b. The left rotor 2a is provided with three automatic stable suction valves 13a. The figure shows a situation where compression or gas discharge by the discharge valve 14b at the right rotor 2b (depending on the pressure level in the discharge space) is in progress in the lower portion of the compressor, while in the upper portion of the compressor, suction of gas by the suction valves 13a at the left rotor 2a is occurring.

Fig. 14 shows a diagram of a tooth compressor with a suction valve and stable discharge valves. In the upper portion of the compressor, in the suction throat 4, an automatic suction valve 13a is placed, comprising two thin plates 15b and two springs 16b. On the side of the right rotor 2b, four stable automatic discharge valves 13b are located in the discharge throat 6.

Fig. 15 shows a diagram of a tooth compressor with rotary suction and discharge valves.

In the rear sidewall of the compressor, the rotary disk 18a, in which four automatic suction valves 14a are seated, is connected to the left rotor 2a, and in the front sidewall of the compressor, the rotary disk 18b, in which two automatic discharge valves 14b are seated, is connected to the right rotor 2b. The figure illustrates a situation where in the upper portion of the compressor, gas is sucked through two suction valves 14a from the suction space into the working space 3, and in the lower portion of the compressor, the gas is discharged by the discharge valve 14b from the working space 3 into the discharge space following the polytropic compression.

Fig. 16 shows a diagram of an air piston compressor assembly with pressurization. The working space 3 is delimited here by a cylinder 23 and a piston 24. Air is sucked by suction valve 13a into the cylinder 23 by the movement of the piston 24 from top dead center 26 to the bottom dead center 27. At the level of the bottom dead center 27, the piston exposes the pressurizing ports 5c through which cooled compressed air enters the cylinder 23 in a regulated manner. At the same time, it is throttled first to the value of the sucked in air pressure, and gradually, the pressure in the working space 3 of the cylinder 23 increases up to the value of pressure in the discharge line 8. By the movement of the piston 24 to the top dead center 26, the pressurizing ports 5c are first covered by the piston 24, then follows polytropic compression, during which the air pressure in the cylinder 23 rises to a value slightly above the pressure in the discharge line 8 (to overcome the resistance and inertia of the discharge valve 13b), thereby opening the discharge valve 13b and discharging the entire amount of air from the cylinder 23 into the discharge line 8. Off of the discharge line 8, a pressurizing line 9 branches through which a portion of the compressed air is transferred to the cooler 10 and further through the regulation fitting IT to the cylinder 23 for compressing the sucked in air in the next compression cycle. The air pressure in the discharge line 8 is stabilized by means of an air tank 25.

Fig. 17 shows a diagram of the cylinder 23 with the pressurizing ports 5c. In the area of the bottom dead center 27 of the piston 24, 6 pressurizing ports 5c having dimensions of 12 x 30 mm are milled along the circumference of the cylinder 23 with a diameter of f 100 mm. The cross- section of the ports 5c is chosen rectangular to reduce the portion of the stroke height of the piston 24 set aside for pressurizing in favor of the stroke height set aside for suction and for discharge.