Liquid machine

Technical Field

The invention concerns a liquid machine comprising a stator in which an elongated rotor of a rotationally symmetrical shape is installed by a rigid shaft in a turning way and between the stator and the rotor there is a coaxial channel that has the shape of a diffuser in at least a part of its length and the stator is equipped with at least one tangentially connected liquid inlet and at least one liquid outlet while the liquid outlet is positioned in a distance from the liquid inlet in the direction of the rotor axis

Background Art

Liquid machines consisting of a stator in which a rotor with blades is installed in a turning way are commonly known from the state of the art. The driving medium may be gas or liquid or their mixture. The driving medium flows through the stator and turns the rotor by applying its force on the blades of the rotor. To optimise use of energy designers endeavour to minimise the gap between the tips of the rotor blades and the inner wall of the stator. If the gap between the rotor blades and the inner wall of the stator is too big, the energy of the working media is not used in an optimum way.

Further, bladeless liquid machines are known. E.g. author's certificate no. 941 665 of the former USSR describes a hydro-motor which consists of a rectification channel in which a confusor is arranged. In the axis of the confusor a ball-shaped rotor is installed on a shaft. The rotor is connected to a starting motor.

At the start the starting motor is first used to rotate the shaft and the ball rotor. The flow of liquid that passes around the ball in the confusor from all sides is set in motion this way. The flow of liquid rotating in the confusor then maintains rotation of the ball rotor as a result of friction between the liquid and the surface of the ball rotor.

However, a disadvantage of this design is that the rotor cannot be set in motion without an auxiliary starting motor.

Another author's certificate no. 1701971 of the former USSR deals with a similar hydro-motor where the starting motor is replaced with screw blades installed in the confusor.

Also, in the case of this design the hydro-motor cannot be put in operation without auxiliary starting equipment consisting in screw blades in this case.

The Czech patent no. 295305 called "Bladeless liquid machine" and the international application no. PCT/CZ2005/000029, the disclosure of which is incorporated by reference, deals with a liquid machine comprising a stator in which a bladeless rotor of a rotationally symmetrical shape is installed and between the stator and the rotor there is a coaxial channel. The stator is equipped with at least one liquid inlet and at least one liquid outlet while the liquid outlet is positioned in a distance from the liquid inlet in the direction of the axis of the bladeless rotor. The liquid inlet is connected tangentially to the stator and the coaxial channel has the shape of a diffuser in at least a part of its length.

A liquid machine designed this way does not need any auxiliary starting drive and in spite of this the rotor can be mounted in a simple way. However, measurements have shown that in some regimes the laminar flow on the rotor surface, and consequently the boundary- layer which transfers kinetic energy from the working medium onto the rotor may get detached, which results in decreased performance of the liquid machine.

The aim of this technical design is to modify the structure of the liquid machine based on the Czech patent no. 295305 and the international application no. PCT/CZ2005/000029 in such a way as to prevent boundary-layer separation on the rotor surface.

Disclosure of Invention

The above mentioned aim is achieved with a liquid machine comprising a stator in which an elongated rotor of a rotationally symmetrical shape is installed by a rigid shaft in a turning way and between the stator and the rotor there is a coaxial channel that has the shape of a diffuser in at least a part of its length and the stator is equipped with at least one tangentially connected liquid inlet and at least one liquid outlet while the liquid outlet is positioned in a distance from the liquid inlet in the direction of the rotor axis. The stator is equipped with whirling surfaces.

The advantage of a liquid machine based on this invention is that the applied whirling surfaces prevent boundary-layer separation and this way they improve transfer of energy between the liquid and the rotor. The whirling surfaces stabilise flow in the coaxial channel with the diffuser shape, which has a positive impact on efficiency of the machine. The smooth part of the rotor fulfils the function of a liquid distributor at the same time.

In order to find the optimum position of the stator in the rotor in all working regimes it is advantageous if the rotor in installed in an axially adjustable position in the stator.

In a beneficial version the whirling surfaces comprise of protrusions arranged along the perimeter of the rotor with certain intervals after each other.

The protrusion can be arranged both transversally with regard to the rotor shaft and substantially in parallel with the rotor shaft.

In another version the whirling surfaces comprise of a helix arranged on the rotor surface.

The whirling surfaces may also comprise of a blade wheel installed on the rotor surfaces and/or a separate blade wheel installed behind the rotor.

The separate blade wheel may be advantageously installed in an axially adjustable position on the common shaft with the rotor.

Brief Description of Drawings

The invention will be described in a more detailed way with the use of figures that show a schematic representation of a liquid machine based on the invention and sample versions of the whirling surfaces. Fig. 1 and 2 present whirling surfaces comprising of protrusions arranged transversally to the rotor axis. Fig. 3 shows protrusions arranged substantially in parallel to the rotor axis. In Fig. 4 there are whirling surfaces with the shape of a helix while in Fig. 5 the whirling surfaces have the shape of protrusions on the rotor front. Fig. 6, 7 and 8 show whirling surfaces in the form of various designs of blade wheels.

Modes for Carrying Out the Invention

In sample embodiments shown in Figs. 1 to 8 the liquid machines have the same basic design and they are only differentiated by the design of the whirling surfaces 10. All the presented versions have a stator 1 whose inner diameter gets narrower in the liquid flow direction. In the stator 1 an elongated rotor 2 of a rotationally symmetrical shape is mounted on a rigid shaft 3. With the exception of the whirling surfaces .10 described below the surface of the rotor 2 is smooth. Between the stator 1 and rotor 2 there is a coaxial channel 7 ensuring free flow of liquid. The shaft 3 is mounted in both ends of the stator 1 in moving devices 9 allowing to adjust the position of the rotor 2 in the stator X. The moving devices 9 at the same time fulfil the function of turning bearing mounting of the shaft 3. As a moving device 9 any known mechanism can be used. For the design of moving device 9 no protection is sought and this is why it is not described in a detailed way.

Of course, the rotor 2 does not only have to have the shape of a truncated cone as shown in the sample versions in Figs. 1 to 8. The only condition is that the rotor shape must be rotationally symmetrical.

The term "rotor of a rotationally symmetrical shape" means for the purposes of this invetion an elongated body whose axis of rotation is its axis of symmetry at the same time, i.e. on all planes passing through the axis of symmetry the section of the rotor always has the same shape. Naturally, the forming curve whose rotation determines the shape of the outer surface of the rotor can in fact have any shape.

However, the stator 1 - rotor 2 assembly must always be shaped in such a way that the coaxial channel 7 can form a diffuser in at least a part of its length.

The stator 1 is equipped with a tangentially connected liquid inlet 8 at one end and a liquid outlet 5 at the other end. It is obvious that there may be several liquid inlets 8 as well as liquid outlets 5. In the basic version shown in Figs. 1 to 8 there is one liquid inlet 8 comprising of a tangentially connected nozzle (not shown) while there are several liquid outlets 5.

The rotor 2 with the shape of a truncated cone is installed in the stator 1 in such a way that the biggest diameter of the rotor 2 is at the side of the liquid inlet 8 and the smallest diameter of the rotor 2 is at the side of the liquid outlet 5.

In the sample version presented in Fig. 1 along the perimeter of the rotor 2 whirling surfaces 10 in the form of protrusions H positioned in certain intervals after each other are arranged transversally to the axis of the shaft 3 of the rotor 2. The whirling surfaces 10 are only provided in one place of the otherwise smooth surface of the elongated rotor 2.

In this version the protrusions H have a constant thickness, but in the version presented in Fig. 2 the protrusions H may also have another shape, e.g. the displayed shape of a wedge widening or narrowing in the spiral flow direction in the stator 1.

In the sample version shown in Fig. 3 the whirling surfaces 10 also have the shape of protrusions H arranged in intervals after each other along the perimeter of the

rotor 2, but as Fig. 3 makes clear, the protrusions are actually arranged in parallel with the shaft 3 of the rotor 2.

In the version presented in Fig. 4 the whirling surfaces 10 form a continuous helix 12 with variable elevation where at the side of the bigger diameter of the rotor 2 the distances between the peaks of the helix 12 are the highest and at the opposite side they are the lowest.

Fig. 5 presents a sample version of the liquid machine whose whirling surfaces 10 have the shape of elongated protrusions H with a constant thickness that are positioned on the front surface of the rotor 2 in a radial way.

The whirling surfaces JK) in the version shown in Fig. 6 have the form of a blade wheel 4 positioned in one place of the otherwise smooth surface of the rotor 2.

The whirling surfaces 10 in the version shown in Fig. 7 have the form of a separate blade wheel 6 positioned behind the rotor 2 from the point of view of liquid flow through the stator ±. Similarly to the rotor 2 the separate blade wheel 6 may be equipped with a moving device 9 designed to adjust the position of the blade wheel 6 on the shaft 3. The separate blade wheel 6 may rotate independently of the rotation of the rotor 2L

Fig. 8 shows a combination of versions presented in Fig. 6 and 7. The whirling surfaces 10 comprise of both a blade wheel 4 positioned in one place of the otherwise smooth surface of the rotor 2 and a separated blade wheel 6 installed behind the rotor 2.

The function of all the versions presented in figs. 1 to 8 is analogous. Pressurised liquid brought to the stator 1 through the liquid inlet 8 moves on a tangential path along the inner wall of the stator 1 while it gradually enters the coaxial channel 7 between the stator 1 and rotor 2, turns the rotor 2 and finally leaves the stator 1 through the liquid outlets 5. In the coaxial channel 7 with the shape of a diffuser boundary layers are created that turn the rotor 2.

The liquid flow between the surface of the rotor 2 and the inner wall of the stator 1 is mathematically modelled by the system of equations for viscous compressible flow that consists of the equation of continuity, Navier-Stokes equations and the energy equation. These equations result from the laws of conservation of continuity, motion and energy.

For three-dimensional flow this system can be described as follows:

For symmetrical three-dimensional flow this system can be described as follows:

The whirling surfaces IiO based on this invention stabilise the laminar flow on the surface of the rotor 2 and prevent boundary-layer separation, which improves the performance. This is also supported by the combination of the whirling surfaces 10 with the smooth part of the rotor 2, which fulfils the function of a distributor.

During practical tests efficiency of a liquid machine with whirling surfaces 10 in accordance with Fig. 1 was compared with efficiency of a liquid machine without whirling surfaces on the rotor.

The stator 1 had the biggest inner diameter of 50 mm and the smallest inner diameter of 31 mm. Rotor 2_with the shape of a truncated cone had the biggest diameter of 48 mm, the smallest diameter of 20 mm and the length of 84 mm. The medium used was pressurised air from a pressure vessel in which the pressure was maintained in the range between 230 and 290 kPa. In the case of the rotor 2 without whirling surfaces 10 with the use of liquid flow control not shown here the speed of the rotor 2 between 3870 and 4960 rpm was achieved and the performance in the range of 115 to 185 W. After installation of a rotor 2 with the

same dimensions but with whirling surfaces .10 in accordance with Fig. 1 the performance increased by 8.5%.

During the measurement air was used as the driving medium, but in general any liquid can be used.