DESCRIPTION

Field of application

The present invention refers to an endothermic rotary engine, intended for use in traction means for road, sea or air or in cogeneration systems.

Prior art

The most widely used type of combustion turbine is the one used in gas cogeneration plants or as turbojet in the field of aeronautics, and they are defined as "constant-pressure or isobaric turbines" invented by George Brayton in 1872; they consist of a turbocharger in which air is compressed in a combustion chamber to which fuel is added. The force produced by the combustion of the gas causes the rotation of a turbine or turboexpander applied to the same drive shaft as the one that drives the turboccharger.

Another type of combustion turbine is the one invented by Hans Holzwarth in 1908, which consists of a "constant-volume or isochoric turbine" or combustion turbine, which differs in the inclusion of an intake valve to let turbocharged air into the compression chamber, an exhaust valve between the chamber and the turboexpander and an ignition system to ignite the fuel mixture in synchronicity with the opening and closing of the valves.

This type of turbine is the outcome of a difficult and complex production process due to the difficulty of having to synchronise the steps of opening and closing the valves contemporaneously with the combustive ignition and due to problems of fluid-dynamic flow that are hard to overcome. As a result of this constructive complexity this type of turbine exists only in theory, never having reached the stage of industrial realization, despite the research and attempts at creating a functioning product over more than thirty years.

As a result of these difficulties all attempts at industrial application of the functional principle of the constant-volume turbine have been unsuccessful, in particular in the field of endothermic combustion engines.

However, the constant-volume turbine presents considerable advantages over the constant-pressure turbine: it is not very susceptible to the initial amount of compression of the air, so that only a small force is needed to activate a turbocompressor, needing only a fan to guarantee the exchange of air or the flushing of the chamber; it behaves in much the same way as a combustion motor, with a thermodynamic cycle that is very similar to the Otto cycle, and in any case definitely more efficient in yield than either the Brayton or the Otto cycle.

It would therefore be desirable to have an endothermic engine with industrial applicability based on the funtional principle of the constant-volume turbine.

The prior art document FR -A - 801 662 describes an engine with a rotor having blades of decreasing volume.

SUBJECT OF THE INVENTION

The main objective of what constitutes the subject of the present invention is therefore to design an endothermic rotary engine based on the funtional principle of the a constant-volume turbine or a combustion turbine, able to overcome the drawbacks of the prior art.

Within the scope described above one of the aims is to create an endothermic rotary engine based on the funtional principle of the constant-volume turbine, with large-scale industrial applicability, and thus able to be used for land, sea and air traction means, for cogeneration systems or for industrial uses.

Another aim of the present invention is that of designing an endothermic rotary engine that can be manufactured industrially, of limited constructive complexity and with a relatively easy set-up but at the same time able to ensure optimal functionality and a high level of reliability.

Yet another aim is that of making an endothermic rotary engine that is extremely compact but able at the same time to produce high values of power and torque at a relatively low fuel consumption.

A further aim is that of making an endothermic rotary engine that delivers the objectives and aims described above at competitive costs and that can be obtained by means of existing machinery, plants and tools.

The objective and aims described above, as well as others that will become clear in what follows, can be obtained by an endothermic rotary engine as defined in claim 1.

BRIEF DESCRIPTION OF THE FIGURES

Further characteristics and advantages that can be obtained by means of an endothermic rotary engine according to the present invention, based on the functional principle of a constant-volume turbine, will become clear from the following description of a number of particular, but not exclusive, embodiments given by way of non-limiting examples with reference to the following figures:

- figure 1 shows a schematic overview of the operation of a constant-volume turbine of the prior art;

- figures 2A and 2B respectively show a cross section and a perspective view of an endothermic rotary engine in accordance with the present invention;

- figures 3A - 3C respectively show a perspective overview, an enlargement and a cross section of the engine rotor of figures 2A and 2B;

- figure 4 shows a cross section of an alternative embodiment of the rotor;

- figure 5 shows an exploded view of the rotor and the parts connected to it of the endothermic rotary engine according to the present invention;

- figures 6A and 6B respectively show a view that illustrates the internal parts and a perspective view of a fixed part comprising the combustion chamber and the exhaust, able to be coupled with the rotor of the endothermic rotary engine of the present invention;

- figures 7A - 7D show a schematic cross section of a respective step in the operation of the endothermic rotary engine according to the present invention;

- figure 8 shows an embodiment of the endothermic rotary engine with three combustion chambers;

- figures 9A and 9B respectively show a cross section and a perspective view of an alternative embodiment of the rotor of the endothermic rotary engine.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 shows a schematic overview of the operation of a constant-volume turbine of the prior art, in which a turbocharger 1 sucks in and compresses the air in an intake conduit 2 inside of which the intake valve 3 is located. The pressurized air flows into a combustion or ignition chamber 4 in the form of a closed container that the fuel is led into and that is associated with an ignition system 5. The combusted gas formed after ignition passes through the exhaust conduit 6, controlled by an exhaust valve 7, and arrive at a turboexpander 8. At the moment of combustion the intake valve 3 closes whereas the exhaust valve 7 opens and the combusted gas is made to flow towards the turboexpander 8 which, through a rotating drive shaft, drives the turbocharger 1. The part delineated by the dashed line square in the schematic of figure 1 and comprising the exhaust valve 7 and the turboexpander 8, is played in the present invention by a single component called the "expansion - exhaust - chamber blocking" rotor.

In figures 2A and 2B an endothermic rotary engine in accordance with the present invention is shown. The engine 10 comprises an "expansion - exhaust - chamber blocking" rotor 1 1 , referred to in the following as rotor 1 1 for the sake of simplicity, and a stator forming a fixed part 20. The fixed part 20 comprises a combustion chamber 21 having an intake conduit 22 for combusted gas and an exhaust conduit 30 for combusted gas.

The rotor 1 1 is connected to the fixed part 20 in order to be in communication on the one hand with the combustion chamber 21 through the intake conduit 22 and on the other hand with the exhaust conduit 30.

In accordance with the present invention, the rotor 1 1 comprises an expansion section 1 1a, a valve section l ib and an exhaust section 1 1c.

The expansion section 1 1a comprises a plurality of expansion chambers 12 separated from each other by radial blades 13; the valve section l ib comprises a continuous circular surface 14 that is able to block the intake conduit 22, and lastly the exhaust section 1 1c is shaped in such a way that it places the intake conduit 22 in direct communication with the exhaust conduit 30. The expansion section 1 1a, the valve section l i b and the exhaust section 1 1c are located consecutively - in the direction of rotation of the rotor 1 1 - along the external circular surface of the rotor 1 1. The expansion chambers 12 all have equivalent volumes.

In accordance with a preferred embodiment of the present invention, the rotor 1 1 is formed by a toroidal body along the circumferance of which the following are located (in a clockwise direction looking at the figures): the expansion section 1 1a comprising the chambers 12 separated by blades 13; the valve section l i b formed by a sector having a circular surface - continuous and smooth or lightly tooled - that is axial to the rotor's rotational axis and that represents the rotating and blocking valve section of the combustion chamber 21 ; and the exhaust section 1 1c consisting of a recess 15 of sufficient radial and angular extension and shape to place the combustion chamber 21 in communication with the exhaust conduit 30.

According to an alternative embodiment (fig.4), the exhaust section 1 1c is made with exhaust section blades 16 having a radial extension that is less than that of the blades 13 of the expansion section 1 1a.

The radial extension, size and volume of the different blades 13 of the expansion section 1 1a are constant and identical; in this manner the chambers 12 substract an identical amount of combusted gas from the combustion chamber along the whole of the rotor sector taken up by the expansion section 1 1a.

The endothermic rotary engine that is the subject of the present invention is based on the functional principle of the constant- volume turbine or combustion turbine, in which the combustion chamber 21 is connected to a rotor 1 1 having blades 13 that are able to contain the pressure of the combusted gas produced during combustion and to transform this into a rotary motion.

In the contact area between the fixed part 20 and the rotor 1 1 the combusted gas has to be sealed in when passing from the combustion chamber 21 to the expansion chambers 12, which, when pushed and made to rotate, bring the gas to the exhaust conduit 30.

This seal must be ensured both tangentially along the circular peripheral edge of the rotor 1 1 and laterally on the sides of the rotor 1 1.

Taking as point of reference the direction of rotation of the rotor rotor 1 1 (clockwise in the illustrated example), the seal between fixed part 20 and rotor 1 1 extends anteriorly and posteriorly to the intake conduit 22 until it arrives at and continues beyond (posteriorly) the gas exhaust conduit 30.

In practice this seal area has to ensure the best possible seal of the combusted gas in order to prevent the gas from flowing away either laterally or tangengially to the blades 13, and allow the gas to expand and flow away exclusively through the rotation of the blades 13 of the rotor 1 1. In the following we will describe the seal area in greater detail.

The particular configuration of the rotor 1 1 according to the present invention allows it to perform three functions.

A first function of the rotor is called expansion and is defined as the expanding component of the rotor, during which the pressure produced by the combusted gas created in the combustion chamber 21 acts on the blading 13 applied peripherically on the rotor 1 1 in the expansion section 1 1a, thereby causing the rotor 1 1 to rotate around its rotational axis. In this manner the combusted gas can expand, exerting a force on each of the blades 13 proportional to the existing pressure of the combustion chamber 21.

A second function of the rotor is called the exhaust, defined as the exhaust section component of the rotor, in which on a portion 1 1c of the rotor 1 1 there is an appropriate worked area 15 that recalls a blade of elongated form, such that it places in communication the combustion chamber 21 and the exhaust conduit 30, allowing the residual combusted gas to be flushed from the combustion chamber. As we have seen above, this aim can be obtained also by predisposing some of the last blades 16 with a radial extension that is smaller than that of the blades of the expansion section 1 1a.

A third function of the rotor is called the rotating valve blocking the combustion chamber 2 1 , defined also as the blocking component of the combustion chamber, represented by the smooth circular portion 14 of the rotor 1 1 , configured to allow the intake conduit 22 of the combustion chamber 21 to be blocked and to allow the chamber 21 to be filled with combustive agent and fuel.

In order to ensure the seal between the fixed part 20 and the rotor 1 1 it is expedient to make the components of a ceramic material, but the possibility of metal is not excluded. As a matter of fact the ceramics of today offer characteristics of mechanical resistance, wear resistance and thermal shock resistance that are extremely high and combined with an extremely small thermal expansion. Another advantage of ceramic materials is the possibility of making the components by means of casting or compression at ambient temperatures with subsequent further production, rectification, addition of surface layers, with lacquers or ceramic-metallic compound materials and many other methods to obtain a perfect arrangement between fixed and rotating surfaces without having to resort to the use of lubrification during operation.

As illustrated in figure 3A, each blade 13 obtained in the expansion sector 1 1a of the rotor 1 1 has such a configuration that it ensures that the gas is adequately sealed and contained during the rotation of the rotor 1 1.

In particular, each blade 13 delimiting the chambers 12 has a thickness that is suitable and sufficient to ensure a correct seal and containment of the gas.

In the illustrated example the volume of each chamber 12 is delimited posteriorly by a convex wall 12a, anteriorly by an anterior wall 12b opposite the convex wall 12a and arranged in such a manner that it is hit by the flow of combusted gas exiting from the intake conduit 22; on the bottom by a bottom wall 12c, which connects the convex wall 12a with the anterior wall 12b, and laterally by two opposite lateral walls 12d. Clearly the walls that delimit each of the chambers 12 form the blades 13 of the expansion section 1 la of the rotor 1 1.

The anterior wall 12b placed anteriorly is preferably of a straight type, but it can also be slightly concave.

The lateral walls 12d are formed by two opposite annular flanges 19 to form the sides of the rotor 1 1.

Fig. 3B illustrates an enlarged detail of the rotor 1 1 of figure 3A, highlighting the expansion chamber 12 delimited by the blades 13. The free volume of each chamber 12 is given by the product of the area of the lateral wall 12d and the size W (taken along the rotational axis) of the chamber 12 itself. This free volume is occupied by the combusted gas coming from the combustion chamber 21. It will be evident that an increase in the convex curvature of the posterior wall 12a will influence the free volume of the chamber 12 and therefore the quantity of gas that can be contained and transported during the rotation of the rotor 1 1. On the anterior wall 12b of the chamber 12 the combusted gas will exert pressure, causing a pushing force that is proportional to the pressure of the gas and to the surface of the anterior wall 12b itself.

Also in fig. 3B a constructive detail of the rotor 1 1 is highlighted, wherein the annular flanges 19 that form the sides of the rotor 1 1 have a bevel 17 along the outermost edge and an annular flared surface 18 along the outermost portion of the rotor 1 1. Preferably the flared surface has an incline angle a between 1 ° and 5°.

The aim of the bevel 17 and the flared surface 18 is to have a better coupling between the rotor 1 1 and the fixed part 20, in order to ensure an optimal seal.

Figure 5 shows an example embodiment of the rotor 1 1 comprising two annular lateral flanges 19 to form the sides of the rotor and the lateral walls 12d of the chambers 12, each annular flange 19 has the flared surface 18 and the bevel 17; the central part of the rotor 1 1 is formed by an annular body 1 1 1 onto which the blades 13 are applied. This annular body 1 1 1 is placed between the two flanges 19, while two crowns 40 are mounted on the inside to allow the coolant of the rotor 1 1 to pass through.

All of these components of the rotor 1 1 are preferably made of a ceramic material by means of casting or extrusion.

Figures 6A and 6B show the fixed part 20 of the engine according to the present invention. This is to show how this fixed part 20 can be made as a single ceramic block inside of which parts of the combustion chamber 21 and the intake conduit 22 are made. The fixed part further comprises a tangential sealing surface anterior to the combustion chamber 201 , a tangential sealing surface posterior to the combustion chamber 202, a tangential sealing surface posterior to the exhaust section 203 and a lateral sealing surface 204. On the fixed part the following components are mounted: a connector of the external exhaust section 31 communicating with the exhaust conduit 30, one or more spark plugs 50 placed in the combustion chamber 21 , an anterior part of the combustion chamber 205, preferably made of metal and attached to the fixed part in order to create the whole of the combustion chamber 21 , a combustive agent supply valve 206, one or more fuel injectors 207 and a pressurized air intake conduit 208.

The combustion chamber 21 could also be made entirely in the fixed part 20.

The pressurized air will be supplied by machinery outside of the engine, actuated either by the engine itself or by external means known in the field.

The lateral sealing surface 204 comprises a flared wall 204a and a bevel 204b configured to be tightly coupled with the flared surface 18 and the bevel 17 of the annular flange 19 respectively, to ensure the presence of the seal.

Preferably, as can be seen in the figures, the intake conduit 22 is placed in a direction that is substantially tangential to the rotor 1 1 , in order to have the combusted gas hit the anterior surface of the anterior wall 12b of the blade 13 in an orthogonal manner, making the rotor turn in a clockwise direction, in the illustrated example. Figure 2A shows in particular how on the anterior sealing surface of the chamber 201 some of the blades 13 contribute to the creation of a tangential and lateral seal in such a way that the outflow of combusted gas in a counter-clockwise and therefore counter-rotational direction is prevented. The precision of the match between the fixed part and the rotating part (the rotor) - and therefore the relative precision of the gas seal - and the rotational velocity of the rotor, which causes a fluidodynamic motion of the residual gas inside the chambers 12, contribute to the prevention of this outflow.

Each blade 13 with its radial peripheral surface (the apex of the blade) creates a seal with the tangential sealing surface anterior to the combustion chamber 201. The extension of the posterior tangential seal of the combustion chamber 202 (Fig. 6A) should have such an angular extension that at least one blade 13 is always up against it in order to have the pressure of the combusted gas act upon the blades 13 with the gas being unable to flow away towards the exhaust conduit 30.

Figures 7 A - 7D schematically show the representative steps of the operation of the endothermic rotary engine according to the present invention.

Figure 7 A shows the expansion step; in this step the pressurized combusted gas impacts the blades 13, which are made to rotate. The tangential sealing surface anterior to the combustion chamber 201 and the tangential sealing surface posterior to the combustion chamber 202 as well as the lateral sealing surface 204, impede the combusted gas from escaping from the chambers 12 up to the exhaust conduit 30 from where it exits just before the blades 13 reach the tangential sealing surface posterior to the exhaust section 203. In fig.7B the operation of the engine is shown during the step of the exhaust section in which the portion of the exhaust section 1 lc of the rotor 1 1 places the combustion chamber 21 in communication with the exhaust conduit 30 allowing the residual combusted gas to be drained away.

Fig.7C shows the operation of the engine in the step of the blocking of the combustion chamber by the valve section l ib of the rotor 1 1. In this step the valve section l i b seals the combustion chamber 22 with the help of the tangential sealing surfaces anterior and posterior to the combustion chamber 201 , 202, the combustive agent supply valve 206 opens and allows the pressurized air present in the conduit 208 to enter. Contemporaneously the injector 207 delivers the necessary quantity of fuel.

Fig.7D shows the engine during the ignition step, during which the rotor presents itself with its expansion section in communication with the combustion chamber 22. The spark plug 50 produces a spark, with a particular anticipation in ignition, with causes the mixture of fuel/ combustive agent to explode and the combusted gas this produces impacts the blades 13 of the rotor 1 1.

From a thermodynamic point of view the rotary engine of the present invention, although based on the principle of the constant- volume turbine, differs from the system invented by Hans Holzwarth and mentioned in the introductory part of the present description. In fact the fluidodynamic behaviour of the rotor 1 1 according to the present invention is different from that of a classic turboexpander, which works at a constant pressure, as the gradual movement of the rotor is substantially more comparable to the lowering of a piston in an alternative engine than the movement of a conventional open-chamber turbine. The resultant thermodynamic cycle in fact proves to be superimposable on the Nikolaus Otto cycle.

With the above engine configuration it is possible to obtain a combustion for each revolution of the crankshaft, and the system can therefore be compared to a alternative two-stroke engine.

Fig. 8 shows an endothermic rotary engine according to the present invention consisting of three combustion chambers held in position by apposite circular plates 300. The rotor 1 1 is of the type described above.

Figures 9A and 9B show a variant of the engine rotor according to the present invention wherein the whole of the expansion section 1 1a, valve section l ib and exhaust section 1 1c is doubled on the same rotor. In the case of rotors of greater dimensions the different sections can be tripled, etc..

From the above it will be clear that the present invention obtains the aims and advantages discussed at the beginning: this design for an endothermic rotary engine includes a new kind of combustion chamber and a three-stage rotor that is able to overcome the drawbacks of the prior art.

We point out in particular that the endothermic rotary engine based on the functional principle of the constant-volume turbine according to the present invention is able to be applied industrially at a large scale, and therefore suitable for use in traction means for road, sea or air or in cogeneration systems.

In fact the engine is of reduced constructive complexity and relatively easy to set up, having substituted the intake and exhaust valve system of the combustion chamber known from the prior art, which brought with it considerable difficulty in synchonisation and great drawbacks in fluidodynamic flow, with a rotary system that is easy to set up and synchronise and that is able to ensure optimal operation and a high level of reliability for the engine.

Moreover, a single rotary engine or engine unit made according to the present invention can occupy, in terms of thickness, a space that is very limited and on average of little more than 10 cm, independently from the rotor's diameter, thereby obtaining a system that is extremely compact and occupying only a small amount of space.

The present invention further makes it possible to assemble several engine units in a modular manner in a very simple fashion and with only a small number of additional parts, in order to obtain an engine group of increasing power. It only needs the addition of an electronic control panel that is programmed with the number of combustion chambers and the extent of their phase displacement to allow the engine to be operated.

The engine according to the present invention is also particularly advantagious for the application in traction means for the road in that in stages where the accelerator is released, all the combustion chambers can remain inactive, without the need for the engine to retain a "minimal" supply to maintain ignition, to return to operation without any mechanical jolts or drive variations as soon as the accelator is again depressed lightly. The present engine in fact does not cause so-called "engine braking". It is possible to have a connection of the rotary engine to an electrical motor that can act as brake and/or braking engine, able to supply electrical power to accumulate during slowdown and braking without having to use the clutch, with the rotary engine running idle, to then start up again immediately on acceleration. Also restarting a stopped engine is much simpler as the starter motor, which does not have to overcome any compression, can restart the engine without any difficulty. A further advantage is that whereas an alternative engine has to be kept at 800- 1000 rpm in order to be self-sustaining and remain running, the engine according to the present invention can also operate with very few rounds per minute as long as the pressure of the intake air is sufficient to fill the combustion chamber.

Naturally the performance of the engine can be increased further by applying turbochargers to the engine's exhausts.

A further advantage is the fact that the engine, even if it can reach high rotational speeds, will supply the highest amount of torque at low rotational speeds with a resultant reduction in consumption, in particular when used for motor vehicle traction.

As far as the field of cogeneration is concerned, given the low manufacturing cost, the simplicity of operation, the silence and the small volume required by an engine made according to the present invention, it is possible to imagine a new cogeneration system, which could be defined nano-cogeneration, consisting of small units of this type of engine for domestic use to substitute the gas burners of current heaters; the gas that normally supplies the burner would instead be used to actuate the engine according to the invention to produce electricity, with the advantage that this engine is simple in terms of construction, reliable and modest in size.

Naturally the present invention is subject to numerous applications, modifications or variations, without falling outside of the scope of protection as defined by the enclosed claims.

Furthermore the materials and tools used to realize the present invention, as well as the shapes and sizes of the separate components, can be those most suitable for specific needs.