GB1561085A

GB1561085A - Hydraulic turbines

Info

Publication number: GB1561085A
Application number: GB39467/75A
Authority: GB
Original assignee: RANKEL TURBINES Ltd
Current assignee: RANKEL TURBINES Ltd
Priority date: 1976-12-23
Filing date: 1976-12-23
Publication date: 1980-02-13

Description

(54) IMPROVEMENTS IN OR RELATING TO HYDRAULIC TURBINES (71) We, RANKEL TURBINES LIMITED a British Company of Rockbourne Mews, Rockbourne Road, Forest Hill, London, S.E.23, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to hydraulic turbines and particularly to hydraulic turbines which are suitable for driving rotatable members, such as compressor rotors, air fans and atomising discs, at high speeds.

In our British Patent Application No.

1409091 and our co-pending British Patent Application 39465/75 (Serial No.l 561 084) we describe a hydraulic turbine in which the turbine rotor is mounted on a shaft which is rotatably located by bearings and means are provided for supplying hydraulic fluid to the turbine as the working fluid therefor, and to the bearings for the lubrication thereof. The particular method of lubricating the bearings which is disclosed in our aforementioned Patent Application is to bleed a quantity of hydraulic fluid from the high pressure supply line to the bearing and to supply the bled hydraulic fluid to the bearings through suitably disposed passages in a bearing housing.The fact that the hydraulic fluid is supplied to the turbine at a very high pressure, however, necessitates that means must be provided to greatly reduce the pressure of the hydraulic fluid bled from the main supply line before it is supplied to the bearings. Such pressure reducing means will usually embody a very small restriction in the bleed line but this creates the problem that the possibility of the bleed line becoming blocked is greatly increased. It is an object of the present invention to provide a method of lubricating the bearings of a hydraulic turbine with hydraulic fluid which overcomes this problem.

According to the invention a hydraulic turbine comprises a shaft, one or more turbine rotors mounted on the shaft and driven by jets of a hydraulic fluid suitable for lubrication, a bearing rotatably mounting the shaft, wherein lubrication of the bearing is effected by a mist or spray of said hydraulic fluid.

The hydraulic fluid mist is preferably generated by directing a jet of high pressure hydraulic fluid at a member, of annular shape, carried by the shaft. The mist generating member must be so disposed that the mist so formed passes into a zone surrounding the bearings, for example, through one or more passages leading to the bearing zone. Whilst a mist generating member may be specifically provided for that purpose it is preferred that one of the turbine rotors be so disposed that the mist which it generates when one or more jets of high pressure hydraulic fluid are applied thereto passes into the bearing zone for the lubrication of the bearings.

In a preferred embodiment of the invention a hydraulic turbine comprises a housing which has a turbine chamber and a bearing chamber, the shaft being rotatably mounted by bearings located within the bearing chamber and having an impulse turbine rotor mounted thereon within the turbine chamber. The shaft passes from the bearing chamber to the turbine chamber through an aperture in the housing which is of larger diameter than the shaft such that an annular space is left between the periphery of the aperture and the shaft. A plurality, preferably four, nozzles are located in the wall of the turbine chamber and are arranged to direct tangential jets of high pressure hydraulic fluid at the turbine rotor.The turbine rotor is so disposed on the shaft that, when the turbine is operating, some of the mist which is generated when the jets of hydraulic fluid strike the turbine rotor passes through the annular space into the bearing chamber, depositing sufficient fluid on the moving surfaces to provide lubrication thereof. Preferably the hydraulic turbine will be so orientated that the shaft is substantially vertical and the bearing chamber is disposed above the turbine chamber. With such an orientation the hydraulic fluid deposited in the bearing chamber will drain back into the turbine chamber for recycling with the remainder of the hydraulic fluid.It is important with such an arrangement, however, to prevent the hydraulic fluid draining from the bearing chamber onto the turbine rotor, which would create fluid drag, and this may be achieved by making the aperture between the bearing and turbine chambers of larger diameter than the turbine rotor, hydraulic fluid therefore dripping from the periphery of the aperture outside the diameter of the rotor.

The hydraulic turbine according to the invention is particularly suitable for driving rotatable members such as compressor rotors, air fans and atomising discs, at high rotational speeds and in this context it is important that sufficient hydraulic fluid be deposited on the bearing surfaces to produce some fluid damping of any unwanted vibrations which may be created.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a vertical cross-section through a compressor and hydraulic turbine drive unit with a hydraulic turbine according to the invention, Figure 2 is a cross-section along the line A-A of Figure 1, Figure 3 is an axial view of a turbine wheel, Figure 4 is a cross-section along the line B-B of Figure 3, Figure 5 is a cross-section through a turbine blade along the line C - C of Figure 4, Figure 6 is an axial view of an alternative turbine wheel, Figure 7 is a cross-section along the line D - D of Figure 6, Figure 8 is an axial view of a further alternative turbine wheel, Figure 9 is a radial view of the turbine wheel shown in Figure 8, Figure 10 is a diagrammatic representation of a hydraulic fluid supply, Figure 11 is a diagrammatic representation of the co-operative operation of a hydraulic turbine nozzle control circuit and variable attitude swirl vanes in the compressor inlet, and Figure 12 is a cross-section through the compressor inlet along the line E - E of Figure 11.

Referring firstly to Figures 1 and 2, the housing of the compressor and hydraulic turbine drive unit comprises a turbine casing 1, a coverplate 2 secured to the turbine casing 1, a bearing housing 3, a compressor base plate 4 and compressor casing 5. The base plate 4 and the bearing housing 3 are secured to the coverplate 2 by screws 6 (only one of which is shown) and the compressor casing 5 is secured to the compressor base plate 4 by screws 7 and washers 8.

A shaft 9 is vertically disposed in the housing and is rotatably mounted in bearings 10 carried by the bearing housing 3. A compressor rotor 11 is mounted on the uppermost end of the shaft 9 and is secured in position by a nut 12 screwed on the end of the shaft. The compressor rotor 11 is rotatable within a compressor chamber 13 which has an axial inlet 14, provided with adjustable guide vanes 15, and a tangential outlet 16.

The lowermost end of the shaft 9 carries two impulse hydraulic turbine wheels 17 which are axially separated by a spacer 18 and are secured to the shaft by a nut 19 screwed on the end of the shaft 9. The turbine wheels are rotatable in a turbine chamber 20 and each has four associated tangential hydraulic feed nozzles 21 which are located at equal circumferential spacings in the wall of the turbine casing 1. The base of the casing 1 is provided with an aperture 22 through which hydraulic fluid may drain from the turbine chamber 20 for return to a hydraulic fluid reservoir. The hydraulic feed pipe to each nozzle is provided with a solenoid operated valve, not shown, which allows the selective cut-out of the nozzles in response to the power output required for the compressor as hereinafter described.

Attention is drawn to our British Specification No.l 561 084 (Application No.39466/75) which is directed to this feature.

The bearings 10 are lubricated by mist or spray of the fluid from the turbine rotors.

The mist or spray enters the bearing chamber through an aperture 24 in the coverplate 2. This aperture has a diameter greater than that of the turbine rotors.

Hydraulic fluid drains from the bearing housing 3 into the turbine chamber 20 through the aperture 24. A deflection plate 25 is mounted between the bearing housing 3 and the compressor base plate 4 and acts to deflect lubricant discharged from the bearings 10 away from an oil seal 26 carried by a hardened steel sleeve 32 which prevents ingress of the lubricant into the compressor chamber 13.

The configuration of the turbine wheel 17 can be seen in Figures 3, 4 and 5 from which it will be seen that each turbine blade 33 has two cup-like depressions 34 formed in the face thereof. An alternative turbine wheel shown in Figure 6 and 7 is basically the same as the turbine wheel 17 but differs in that each turbine blade 36 is inclined in the direction of rotation. A still further alternative turbine blade shown in Figures 8 and 9 is of a different basic configuration in that the blades 36 are formed by the serrated circumference of the turbine wheel and each blade 36 is provided with a single trough-shape depression 37. It should be understood that the above-described alternative turbine wheel configurations are described purely by way of example and other configurations may be used.

The compressor and hydraulic turbine drive unit is preferably mounted directly on to a hydraulic fluid reservoir tank 27, as shown in Figure 10.

A hydraulic pump 28 driven by an electric motor 29 draws hydraulic fluid through a filter 30 from the tank 27 and delivers it through a pressure regulating valve 31 to the nozzles 21. A pressure regulating valve is not necessarily essential and it will usually be used only where a variation in pressure is required or where the full output from the pump 28 is not required. The aperture 22 in the turbine casing 1 is aligned with a similar aperture in the tank 27 and hydraulic fluid drains directly from the turbine chamber 20 into the tank 27. Figures 11 and 12 illustrate diagrammatically a control circuit for the nozzles adapted to act co-operatively with the swirl guide vanes 15 disposed in the inlet to the compressor.As the required flow rate through the compressor varies, the swirl vanes 15 are rotated to adopt an attitude which optimises the efficiency of the compressor at the flow rate required. The attitude of the swirl vanes 15 is altered quite simply by a control rod 38 which in moving linearly rotates one of the swirl vanes directly through a lever 39 and rotates the other swirl vanes indirectly through rods 40 and levers 41 actuated by the lever 39. The control rod 38 is provided with a cam surface 42 which is adapted to contact and operate three switches 43, 44 and 45 which are in turn adapted to actuate solenoid operated valves 46, 47 and 48 respectively.

The nozzles 21 of the turbine are arranged in pairs, each pair being constituted by a nozzle associated with each of the two turbine wheels, and the cam 42 and the switches 43, 44 and 45 are arranged such that the switches operate solenoid operated valves 46, 47 and 48 in turn to terminate the hydraulic supply to two, four and six nozzles respectively in response to the flow rate through the compressor as determined by the attitude of the swirl vanes 15. If the efficiency of the compressor remained constant over the range of flow rates required, the nozzles 21 would be progressively closed in a linear relationship with the flow rate, so that, for example, at a 50% reduction of flow rate, four nozzles would be closed reducing the power output of the turbine by 50% and keeping the speed of rotation of the compressor rotor substantially constant.In practice, however, the efficiency of the compressor will normally fall as the flow rate is reduced and this necessitates an increase in the speed of rotation of the compressor rotor and hence the nozzles 21 would require switching in a non-linear relationship to the compressor flow rate in order to match the power output of the turbine to the required speed of rotation. An additional or alternative means of increasing the speed of rotation of the compressor rotor is to increase the hydraulic pressure and this is conveniently achieved by selecting the power of the electric motor 29 such that as the hydraulic flow rate through the pump 28 decreases, due to the closing of some of the nozzles 21, the delivery pressure increases by an amount sufficient to increase the speed of rotation of the turbine by the required amount.The pump will usually be provided with a pressure no lower than the pressure corresponding to the maximum required speed of rotation of the turbine.

The compressor and hydraulic turbine drive unit constructed as hereinbefore described is readily adaptable to cover a range of capacities. For example the fitting of a compressor with a different capacity to the unit necessitates the replacement of the compressor rotor 11, the compressor base plate 4 and the compressor housing 5. The turbine must be matched to the requirements of the compressor fitted and this can be achieved by fitting tips for the nozzles 21 with an appropriate size aperture. The nozzles aperture size will have to be within predetermined limits and, for example, with a hydraulic pressure of 1750 pounds per square inch will typically be between one millimeter (below which spray is likely to occur) and two and half millimeters (above which it is difficult to accommodate a regular flow pattern around the turbine blades).Furthermore for the smaller capacity compressors it will usually be possible to utilise just one of the two turbine wheels and therefore the possible range extends from a turbine with a single turbine wheel and four nozzles with one millimeter apertures to a turbine with two turbine wheels and a total of eight nozzles with two and half millimeter apertures.

The hydraulic turbine may be powered by any commercially available hydraulic fluid and we have found that most of such fluids can be utilised to lubricate the bearings of the unit.

The afore-described rotary compressor and hydraulic turbine drive unit is particularly suitable for use in refrigeration equipment and, purely by way of example, the following are design parameters of a typical unit for use with dichlorodifluoromethane refrigerant fluid to cover a capacity range of about 10 to 90 tons of refrigeration: (i) Compressor rotor diameter: between 70mm and 140mm.

(ii) Hydraulic pressure: 123 kilograms per square centimeter.

(iii) Turbine pitch circle diameter: 32mm.

It is advantageous to use the refrigerant fluid, where suitable for the purpose, as the hydraulic fluid and the lubricant for the bearings and thus have a single fluid used throughout the unit.

Whilst the invention has been described above with reference to a centrifugal compressor it should be understood that the invention is not limited thereto. A hydraulic turbine according to the invention could be used, for example, to drive an axial compressor, an air fan, and a rotating disc of an atomiser. Such a hydraulic turbine is applicable, inter alia, to equipment for movement of air and other fluids, vacuum cleaning and the conveying of particulate materials.

WHAT WE CLAIM IS: 1. An hydraulic turbine comprising a shaft, one or more turbine rotors mounted on the shaft and driven by jets of an hydraulic fluid suitable for lubrication, a bearing rotatably mounting the shaft, wherein lubrication for the bearing is provided by a mist or spray of said hydraulic fluid.

2. A turbine as claimed in claim 1, wherein the mist or spray generated by the turbine is caused to lubricate the bearing.

3. A turbine as claimed in claim 1, wherein the mist or spray is generated by directing a jet of the fluid on to an annular member on the shaft.

4. An hydraulic turbine as claimed in claim 2, comprising a housing having a turbine chamber and a bearing chamber, the shaft being rotatably mounted by bearings located within the bearing chamber, the shaft passing through an aperture in the housing which is of larger diameter than the shaft such that an annular space is left between the periphery of the aperture and the shaft.

5. A turbine as claimed in claim 4, wherein the shaft is mounted on a vertical axis with the bearing chamber above the turbine chamber.

6. A turbine as claimed in claim 4 or 5, wherein the diameter of the aperture is greater than the turbine rotor.

7. An hydraulic turbine substantially as described with reference to the accompanying drawings.

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Claims

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capacity compressors it will usually be possible to utilise just one of the two turbine wheels and therefore the possible range extends from a turbine with a single turbine wheel and four nozzles with one millimeter apertures to a turbine with two turbine wheels and a total of eight nozzles with two and half millimeter apertures.

The hydraulic turbine may be powered by any commercially available hydraulic fluid and we have found that most of such fluids can be utilised to lubricate the bearings of the unit.

The afore-described rotary compressor and hydraulic turbine drive unit is particularly suitable for use in refrigeration equipment and, purely by way of example, the following are design parameters of a typical unit for use with dichlorodifluoromethane refrigerant fluid to cover a capacity range of about 10 to 90 tons of refrigeration: (i) Compressor rotor diameter: between 70mm and 140mm.

(ii) Hydraulic pressure:

123 kilograms per square centimeter.

(iii) Turbine pitch circle diameter: 32mm.

It is advantageous to use the refrigerant fluid, where suitable for the purpose, as the hydraulic fluid and the lubricant for the bearings and thus have a single fluid used throughout the unit.

Whilst the invention has been described above with reference to a centrifugal compressor it should be understood that the invention is not limited thereto. A hydraulic turbine according to the invention could be used, for example, to drive an axial compressor, an air fan, and a rotating disc of an atomiser. Such a hydraulic turbine is applicable, inter alia, to equipment for movement of air and other fluids, vacuum cleaning and the conveying of particulate materials.

WHAT WE CLAIM IS: 1. An hydraulic turbine comprising a shaft, one or more turbine rotors mounted on the shaft and driven by jets of an hydraulic fluid suitable for lubrication, a bearing rotatably mounting the shaft, wherein lubrication for the bearing is provided by a mist or spray of said hydraulic fluid.
2. A turbine as claimed in claim 1, wherein the mist or spray generated by the turbine is caused to lubricate the bearing.
3. A turbine as claimed in claim 1, wherein the mist or spray is generated by directing a jet of the fluid on to an annular member on the shaft.
4. An hydraulic turbine as claimed in claim 2, comprising a housing having a turbine chamber and a bearing chamber, the shaft being rotatably mounted by bearings located within the bearing chamber, the shaft passing through an aperture in the housing which is of larger diameter than the shaft such that an annular space is left between the periphery of the aperture and the shaft.
5. A turbine as claimed in claim 4, wherein the shaft is mounted on a vertical axis with the bearing chamber above the turbine chamber.
6. A turbine as claimed in claim 4 or 5, wherein the diameter of the aperture is greater than the turbine rotor.
7. An hydraulic turbine substantially as described with reference to the accompanying drawings.