WO2015147744A1

WO2015147744A1 - A vane-slot mechanism for a rotary vane machine

Info

Publication number: WO2015147744A1
Application number: PCT/SG2015/000087
Authority: WO
Inventors: Kuan Thai AW; Alison Subiantoro; Kim Tiow Ooi
Original assignee: Nanyang Technological University
Priority date: 2014-03-28
Filing date: 2015-03-23
Publication date: 2015-10-01

Abstract

A vane-slot mechanism for a rotary vane machine having a rotor configured to relatively rotate within a cylinder, the vane-slot mechanism comprising: a slot provided on one of: the rotor and the cylinder; a vane provided on the other of: the rotor and the cylinder, the vane configured to slidably and rotatably engage the slot; smooth side surfaces provided on and integral with one of: the slot and the vane; and smooth radiused edges provided on and integral with the other of: the slot at an opening of the slot and the vane at a free end of the vane; wherein one of the smooth radiused edges engages one of the smooth side surfaces with a line contact during operation of the vane-slot mechanism. "

Description

A VANE-SLOT MECHANISM FOR A ROTARY VANE MACHINE

FIELD OF THE INVENTION

This invention relates to a vane-slot mechanism for a revolving vane machine, and in particular to a rotary compressor or expander which has a rotor eccentrically mounted within a cylindrical housing and having a vane mounted in a slot provided either on the rotor or on the cylinder.

BACKGROUND OF THE INVENTION

A typical vane and slot mechanism consists of a rotor, a cylinder and a relatively thin vane oscillating in and out of its slot during operation. In a configuration known as a fixed-vane revolving-vane configuration as shown in Figs. 1a and 1b (prior art), a slot 18 with convex sides 60 or a vane bushing component 62 can be introduced to accommodate swivelling of the vane 12 in its oscillatory motion. Having the slot 18 with convex sides 60 involves fewer components than having the bushing 62 but the slot geometry as can be seen in Fig. 1a is impractical to manufacture in reality due to machining tolerances. Moreover, it requires the two side surfaces of the vane 12, the two slot surfaces 60 in contact with the vane 12, and the end faces 28, 54 to be smooth. Compared to the slot mechanism in Fig. 1a (prior art), the bush mechanism in Fig. 1b (prior art) is more practical to manufacture and is currently employed in revolving vane and swing compressor mechanisms. However, it requires additional components of the two bushes 62. It also requires more smooth surfaces, including the two side surfaces of the vane 12, the two surfaces of the bushes in contact with the vane (2 surfaces), the curved surfaces of the bushes 62 in contact with the slot 18, the two curved surfaces of the slot 18 in contact with the bushes 62 as well as the endfaces 28, 54.

As it is costly to manufacture smooth surfaces, the more smooth surfaces are required the higher the cost of the mechanism. There is thus a demand for an efficient vane and slot mechanism that is more cost effective and also time effective to produce.

SUMMARY OF INVENTION

The present application discloses a novel vane-slot mechanism that is simpler and more economical than existing mechanisms. The mechanism design comprises a tapered vane or slot with a tapered design (inwards or outwards) in which the vane has a single pivoting point

l contact with the slot. The design is configured for minimising the peak torque demand of the rotation, hence saving energy. The proposed design reduces manufacturing cost of the vane and slot mechanism in rotary vane machines by reducing the design requirements of the rotary vane machines, reducing the number of steps in the manufacturing processes and reducing the number of components of the mechanism. In addition, the new design can also improve machine performance in some applications.

According to a first aspect, there is provided a vane-slot mechanism for a rotary vane machine having a rotor configured to relatively rotate within a cylinder, the vane-slot mechanism comprising: a slot provided on one of: the rotor and the cylinder; a vane provided on the other of: the rotor and the cylinder, the vane configured to slidably and rotatably engage the slot; smooth side surfaces provided on and integral with one of: the slot and the vane; and smooth radiused edges provided on and integral with the other of: the slot at an opening of the slot and the vane at a free end of the vane; wherein one of the smooth radiused edges engages one of the smooth side surfaces with a line contact during operation of the vane-slot mechanism.

The smooth side surfaces may be provided on and integral with the vane, wherein the smooth radiused edges are provided on and integral with the slot, and wherein side surfaces of the slot converge towards the opening of the slot. The side surfaces of the vane may converge towards the free end of the vane.

Alternatively, the smooth side surfaces may be provided on and integral with the slot, wherein the smooth radiused edges are provided on and integral with the vane, and wherein side surfaces of the vane diverge towards the free end of the vane.The side surfaces of the slot may converge towards the opening of the slot.

Length L_v of the vane may satisfy 3(r_c - r_r ) > L_v > l{r_c - r_r ) , where r_c is radius of an inner wall of the cylinder and r_r is radius of an outer wall of the rotor.

Length L_s of the slot may satisfy 1 ,5L_V > L_S > L_V , where L_v is length of the vane.

Width w_os of the slot may satisfy 1.5w_v > w_as > w_v , where w_v is a greatest width of the vane. The vane may be attached to the rotor and an angle Θ between a side surface of the vane and a side surface of the slot when a central longitudinal axis of the vane is parallel to a central longitudinal axis of the slot may satisfy

where r_c is radius of an inner wall of the cylinder and r_r is radius of an outer wall of the rotor

The vane may be attached to the cylinder and an angle Θ between a side surface of the vane and a side surface of the slot when a central longitudinal axis of the vane is parallel to a central longitudinal axis of the slot may satisfy

Θ may satisfy 1⁰ > Θ > 45° when 0.65 < < 0.98.

r

BRIEF DESCRIPTION OF FIGURES

In order that the invention may be fully understood and readily put into practical effect there shall now be described by way of non-Umitative example only exemplary embodiments of the present invention, the description being with reference to the accompanying illustrative drawings.

Fig. 1a (prior art) is a schematic illustration of a first prior art mechanism.

Fig. 1 b (prior art) is a schematic illustration of a second prior art mechanism.

Fig. 2a is a schematic illustration of a first exemplary embodiment of the vane-slot mechanism of the present invention with the vane provided on the rotor and the slot provided in the cylinder.

Fig. 2b is a schematic illustration of the first exemplary embodiment of the vane-slot mechanism of the present invention with the vane provided on the cylinder and the slot provided in the rotor. Figs. 3a to 3e are schematic illustration of five different embodiments of the vane-slot mechanism of the present invention.

Fig. 4a is a schematic illustration of a second exemplary embodiment of the vane-slot mechanism of the present invention with the vane provided on the cylinder and the slot provided in the rotor.

Fig. 4b is a schematic illustration of the second exemplary embodiment of the vane-slot mechanism of the present invention with the vane provided on the rotor and the slot provided in the cylinder.

Fig. 5 is a schematic illustration of the vane of the second exemplary embodiment of the vane-slot mechanism of the present invention.

Fig. 6a is a schematic illustration of a third exemplary embodiment of the vane-slot mechanism of the present invention with the vane provided on the rotor and the slot provided in the cylinder.

Fig. 6b is a schematic illustration of the third exemplary embodiment of the vane-slot mechanism of the present invention with the vane provided on the cylinder and the slot provided in the rotor.

Fig. 7 is a schematic illustration of a change in resultant force direction using a converging vane of the third exemplary embodiment of the vane-slot mechanism.

Fig. 8a is a schematic illustration of a fourth exemplary embodiment of the vane-slot mechanism of the present invention with the vane provided on the rotor and the slot provided in the cylinder.

Fig. 8b is a schematic illustration of the fourth exemplary embodiment of the vane-slot mechanism of the present invention with the vane provided on the cylinder and the slot provided in the rotor.

Fig. 9 is a schematic illustration of a change in resultant force direction using a diverging vane of the fourth exemplary embodiment of the vane-slot mechanism.

Fig. 10 is a graph showing effects of vane side tapering angle to compressor torque.

Fig. 11 is a graph showing effects of vane side tapering angle to expander torque. DETAILED DESCRIPTION

Exemplary embodiments of the vane and slot mechanism 10 will be described below with reference to Figs. 2 to 11 in which the same reference numerals are used to denote the same or similar parts of the mechanism 10. In general, the vane-slot mechanism of the present invention 10 comprises a protruding vane 20 that is rigidly fixed to either the rotor 80 or the cylinder 90 of a rotary machine, wherever is appropriate, and a slot 30 is located at either the rotor 80 or the cylinder 90, wherever is appropriate, where the vane 20 moves in and out of the slot 30 during operation. At least one contact edge 22 or 32, which is between a smooth chamfered or radiused surface and a smooth flat surface 24 or 34 , is always maintained between the vane 20 and the slot 30. The vane 20, the slot 30 or both have a tapered geometry with a tapering angle that allows for the swivelling movement of the vane 20. The length of the slot 30 is slightly longer than the vane 20 such that the reciprocating movement of the vane 20 is not obstructed.

Embodiment 1

Illustrations of a first embodiment of the vane-slot mechanism 10 are shown in Fig. 2 and Fig. 3a. In this main embodiment, the vane 20 is rectangular with straight sides 24 and the slot 30 is tapered. The two opening tips or edges 32 of the slot 30 are radiused and smooth. The two side surfaces of the vane 24 are smooth too. The vane 20 is always in contact with one of the slot opening tips or edges 32 during operation. The rotary machine is of the fixed-vane RV machine type.

The vane-slot mechanism 10 of this invention removes the bushing of the prior art mechanism, hence fewer components are involved. The geometry of the slot 30 is simplified for easier manufacturing and the surfaces that must be smooth are reduced to only the sides 24 or 34 of either the vane 20 or the slot 30 respectively (2 surfaces), the contact edges 32 or 22 of the slot 30 or the vane 20 respectively) (2 edges), excluding the endfaces. The overall performance can be improved due to potential reduction of dead volume in some of the variants. The motor size can be reduced due to the potential reduction of compressor peak torque requirement in some of the variants. When used in expander applications, higher peak torque can be produced in some variants for better performance.

Fig. 3 shows five different embodiments of the vane-slot mechanism 10 of the present invention, in which:

• r_c is the radius of the inner wall of the cylinder 90

• r_r is the radius of the outer wall of the rotor 80

• Θ is the "tapering opening angle", which is the angle between the side walls 24 of the vane 20 and the side walls 34 of the slot 30 when the vane 20 and the slot 30 are aligned, that is, when the central longitudinal axis X_v of the vane 20 is parallel to the central longitudinal axis X_s of the slot 30, as shown in Figs. 3a and 3e.

• L_s is the total length of the vane 20

• L_v is the total length of the slot 30

To ensure that the vane-slot mechanism 10 performs well, it is preferred that the following conditions are satisfied:

1. Length of the vane 20 should be at least double that of the difference between the radii of cylinder 90 and rotor 80 of the machine. At the same time, it should not be too long to achieve maximum performance. Therefore, in practice, usually: l{r_c -r_r)> L_v > 2{r_c

2. Length of the slot 30 must be longer than the length of the vane 20 but not too long to minimize dead volume. Therefore, in practice, usually: 1.5L_V > L_s' > L_V

3. Opening width of the slot 30 must be larger than the width of the widest part of the vane 20. In practice, usually: 1.5w_v > w_os > w_v

4. The tapering opening angle Θ must be large enough to ensure smooth operation. In a rotary vane mechanism where the vane 20 is attached to the rotor 80:

In a rotary vane mechanism where the vane 20 is attached to the cylinder 90:

However, at the same time, to achieve maximum performance, Θ must be minimized. It is important to note that there is a design constraint for the ratio between radii of the rotor 80 and the cylinder 90, where it must be more than 0.5 and less than 1.

When the ratio is less than 0.5, particularly when the vane 20 is fixed to the cylinder 90, the slot 30 will need to be longer than the diameter of the rotor 80, resulting in an impossible design. When the vane 20 is fixed to the rotor 80, the slot 30 at the cylinder 90 will be too long. Therefore, in practice, the lower limit of the ratio is at least 0.65. Here at this ratio, when the slot 30 is located at the rotor 80, the slot 30 is about the same length as the radius of the rotor 80. At the other end, the ratio must be less than 1 for working chambers to exist. A ratio that is too close to 1 is also not desirable as a bulky rotor 80 is needed, resulting in a high material cost. Therefore, in practice, the upper limit of the ratio between radii of the rotor 80 and the cylinder 90 is usually around 0.98.

From these limits, the practical range of the tapering opening angle is: 1 ° > Θ > 45°

Embodiment 2

In a second embodiment of the mechanism as shown in Figs. 4 and 5, the slot 30 is rectangular with straight sides 34 while the vane 20 is tapered. The smooth radiused surfaces or edges 22 are located at the tip or free end of the vane 20, instead of the slot 30 of the first embodiment. The straight walls or sides 34 of the slot 30 are smooth. During operation, at least one of the vane tips or radiused edges 22 at the free end of the vane 20 is in contact with the slot wall 34.

Due to the different contact point location of the second embodiment compared to the first embodiment, the constraints of the tapering opening angle, Θ, is modified to:

In practice, however, the range of the tapering opening angle Θ is also between 1 ° and 45°. Below 1 °, the mechanism 10 may not work. Above 45°, there will be too much dead volume in the machine. In addition, there is a fixed taper height t in which the vane 20 then straightens into a rectangular profile as shown in Fig. 5. The height of the taper L_w should not exceed the width w_v of the vane tip or free end.

L _vt < w_v

The second embodiment has the advantage of less dead volume in the slot 30 as compared to the other embodiments. This will result in better volumetric efficiency of the machine. It is noted that in the second embodiment, the profile or side walls 34 of the slot 30 can also be tapered as shown in Fig. 3c.

Embodiment 3

In the third embodiment as shown in Figs. 6 and 7, both the vane 20 and the slot 30 are tapered. The vane 20 is of a converging geometry where the base of the vane 20 is wider than its tip or free end. In its extreme case, the tip or free end can be pointed resulting in a triangular vane profile. The two opening tips or edges 32 of the slot 30 are radiused and smooth, similar to the slot 30 of the first embodiment. The two side surfaces 2 vane 20 are smooth too. The vane 20 is always in contact with one of the slot opening tips or edges 32 during operation.

This vane geometry causes the direction of the resultant force acting on the vane 20 to be pointing closer to the center of rotation C of the driving component, as illustrated in Fig. 7 in which the vane 20 is attached to a driven rotor 80. The result is a change of moment arm from U to L₂. It is noted that L₂ is usually shorter than U, hence a lower torque is obtained.

This is beneficial for most compressor applications as it allows for a smaller motor size.

Another advantage of this vane geometrical profile is the narrower slot size requirement as compared to what a rectangular vane 20 like in the first embodiment needs. A smaller slot 30 is desirable to minimize the dead volume of the mechanism. In addition, a smaller slot 30 provides more freedom in the optimization of the designs of the various components.

Embodiment 4 In this embodiment, both the vane 20 and the slot 30 are tapered. However, the vane 20 is of the diverging geometry where the base of the vane 20 is narrower than the tip or free end of the vane 20. The two opening tips or edges 32 of the slot 30 are radiused and smooth, similar to the slot 30 of the first and third embodiments. The two side surfaces 24 of the vane 20 are smooth too. The vane 20 is always in contact with one of the slot opening tips or edges 32 during operation.

With a diverging vane 20, the direction of the resultant force acting on the vane 20 is different from the one with a rectangular vane 20, as shown in Fig. 9. It is now pointing further away from the center of rotation C of the driving component (for example the rotor 80 as shown in Fig. 9), changing the moment arm from L_r to L₃. In most cases, when the inclination angles of the vane sides 24 are small, L₃ is longer than resulting in a higher torque. This is usually not desirable for compressor applications but is desirable for expanders. However, a diverging vane 20 requires a larger slot 30 as compared to a rectangular vane 20 of the first embodiment, which usually results in more dead volume. Moreover, the reliability of the vane 20 is challenged because of the high stress at the narrowed base of the vane 20.

The effects of the vane side tapering angles to the torque requirement of a RV compressor are shown in Fig. 10, in which positive angle refers to a converging vane (embodiment 3) while a negative angle refers to a diverging vane (embodiment 4). The graphs are obtained from a RV compressor with a 29 mm rotor radius, a 33.3 mm cylinder radius and a 49.5 compressor length. The narrowest part of the vane 20 (that is, the tip or free end of a converging vane or the base of diverging vane) is maintained at 0.5 mm. It can be observed that the converging vane 20 of the third embodiment is suitable to be used for compressors. It reduces the peak torques which also lightens the torque demand at the motor. The reduction can be up to 25% (from 8 Nm to 6 Nm), depending on the tapering angle. This reduction in peak torque demand results in less stringent motor requirement, allowing the use of smaller motors than normal compressor. On the other hand, a diverging vane is not preferred to be used for compressors, as it increases the peak torques.

Fig. 11 shows the effects of the vane side tapering angles to the torque production of a RV expander in which positive angle refers to a converging vane and negative angle refers to a diverging vane. The data is obtained from a RV expander with a 29 mm rotor radius, a 33.3 mm cylinder radius and a 49.5 compressor length. The narrowest part of the vane 20 (that is the tip or free end of a converging vane or the base of diverging vane) is maintained at 0.5 mm. It can be seen that unlike the case with compressors, a diverging vane 20 of the second or fourth embodiment is preferred for expanders, instead of the converging vane 20. This is because unlike a compressor, higher torque is desired with an expander. The increase in the peak torque production of a RV expander can be as high as 25% (from 4 Nm to 5 Nm), depending on the tapering angle.

One of the most attractive application possibilities of the vane-slot mechanism 10 of this invention is that when the compressor and the expander are coupled properly, their respective peak torques coincide and hence cancel each other out. From the data in Figs. 0 and 11 , the system peak torque demand can be reduced by more than 85% (from about 8 Nm to 1 Nm) in this case.

In conclusion, the proposed simplified vane-slot mechanism 10 of the present invention should preferably be configured as follows:

• A vane 20 of length at least double the difference between the radii of the cylinder 90 and rotor 80 of the machine, but at the same time, less than thrice of this difference so as not to impede machine operation. 3(r_c - r_r ) > L_v > 2(r_c - r_r )

• A slot 30 of length longer than the vane 20 so as to accommodate the vane 30, at the same time, it should not be too long until too much dead volume is created. l.5L_v > L_s > L_v

• A slot 30 of width wider than the widest part of the vane 20 so as to accommodate the vane 20. \ .5w_v > w_os > w_v

• The profile of the vane 20 or slot 30 or both can be tapered. This tapering opening angle, Θ must be large enough to ensure smooth operation.

• In a rotary vane mechanism where the vane 20 is attached to the rotor 80:

• In a rotary vane mechanism where the vane 20 is attached to the cylinder 90:

· The typical range of Θ would be P > Θ > 45° corresponding to the rotor 80 to cylinder 90 radius ratio of range 0.65 and 0.98, that is, when 0.65 < ≤ 0.98 .

f c,

• The vane 20 and slot 30 require two surfaces and two edges to have a smooth finishing for contact.

• The resulting vane and slot mechanism 10 would have only a single line of contact between the vane 20 and the slot 30

The simplified vane and slot mechanism 10 boasts two significant advantages over existing designs for revolving vane machines. These include: • reduction in manufacturing costs by reducing the design requirements, number of manufacturing processes and the components required

• improvement in machine performance (application dependent) Furthermore, these proposed mechanisms are readily adaptable for existing rotary vane machines, such as revolving vane and swing piston mechanisms in which the world rotary vane compressor market for air conditioning amounted to 126.5 million units in 2013 and this market is projected to grow by 10.7% annually [6], Whilst there has been described in the foregoing description exemplary embodiments of the present invention, it will be understood by those skilled in the technology concerned that many variations in details of design, construction and/or operation may be made without departing from the present invention. For example, although the vanes as shown have straight or flat surfaces on the sides of the vanes, they can also have curved surfaces on the sides of the vanes. The tapering angles of both sides of the vane or slot do not have to be equal as long as the requirements or conditions for the tapering opening angle Θ described above are satisfied.

References

1. Ooi KT, Teh YL, 2010, Revolving vane compressor and method for its manufacture, Patent No. US 20100310401 A1.

2. Ooi KT, Teh YL, 2012, Revolving vane compressor, Patent No. US 8206140 B2.

3. Subiantoro A, Yap KS, Ooi KT, 2013, Revolving vane expander, Patent No. US 20130045124 A1.

4. International Organization of Motor Vehicle Manufacturers, Production Statistics - 20 3, http://www.oica.net/category/production-statistics/

5. Sanden Corporation, Company Profile - Business Summary,

https://www.sanden.co.jp/english/company/business.html

6. Japan Air Conditioning, Heating and Refrigeration News, Serial no. 541 -S, Feb 25 2014, http://www.ejarn.com

Claims

1. A vane-slot mechanism for a rotary vane machine having a rotor configured to relatively rotate within a cylinder, the vane-slot mechanism comprising:

a slot provided on one of: the rotor and the cylinder;

a vane provided on the other of: the rotor and the cylinder, the vane configured to slidably and rotatably engage the slot;

smooth side surfaces provided on and integral with one of: the slot and the vane; and smooth radiused edges provided on and integral with the other of: the slot at an opening of the slot and the vane at a free end of the vane;

wherein one of the smooth radiused edges engages one of the smooth side surfaces with a line contact during operation of the vane-slot mechanism.

2. The vane-slot mechanism of claim 1 , wherein the smooth side surfaces are provided on and integral with the vane, wherein the smooth radiused edges are provided on and integral with the slot, and wherein side surfaces of the slot converge towards the opening of the slot.

3. The vane-slot mechanism of claim 2, wherein side surfaces of the vane converge towards the free end of the vane.

4. The vane-slot mechanism of claim 1 , wherein the smooth side surfaces are provided on and integral with the slot, wherein the smooth radiused edges are provided on and integral with the vane, and wherein side surfaces of the vane diverge towards the free end of the vane.

5. The vane-slot mechanism of claim 4, wherein the side surfaces of the slot converge towards the opening of the slot.

6. The vane-slot mechanism of any preceding claim, wherein length L_v of the vane satisfies 7>(r_c ~ r_r ) > L_v > 2(r_c - r_r ) , where r_c is radius of an inner wall of the cylinder and r_r is radius of an outer wall of the rotor.

7. The vane-slot mechanism of any preceding claim, wherein length L_s of the slot satisfies 1.5L_V > L_s > L_v , where L_v is length of the vane.

8. The vane-slot mechanism of any preceding claim, wherein width w_os of the slot satisfies 1.5w_v > w_os > w_v , where w_v is a greatest width of the vane.

9. The vane-slot mechanism of any preceding claim, wherein the vane is attached to the rotor and an angle Θ between a side surface of the vane and a side surface of the slot when a central longitudinal axis of the vane is parallel to a central longitudinal axis of the slot satisfie

where r_c is radius of an inner wall of the cylinder and r_r is radius of an outer wall of the rotor r_c .

10. The vane-slot mechanism of any one of claims 1 to 8, wherein the vane is attached to the cylinder and an angle Θ between a side surface of the vane and a side surface of the slot when a central longitudinal axis of the vane is parallel to a central longitudinal axis of the slot satisfies

1 1. The vane-slot mechanism of claim 9 or claim 10, wherein Θ satisfies 1⁰ > Θ > 45° when 0.65 0.98 .