AXIAL FLOW TURBINE FOR ORGANIC RANKINE CYCLE

FIELD OF THE INVENTION

[0001] The present invention relates to an axial flow turbine in the field of power generation. The present invention specifically relates to an improved axial flow turbine with converging diverging nozzle for generating power using low grade heat from bio-mass, solar collectors and gas engine exhaust.

BACKGROUND OF THE INVENTION

[0002] Generally, utilization of heat from lower temperature resources such as bio-mass, solar collectors and gas engine exhausts are well known. As the population is ever increasing, there is a great demand for renewable sources of energy and other alternative sources of energy. Solar collectors are presently used at various households as water heaters for residential purposes and for steam generation to drive turbines and produce electricity. Typically, steam turbines require superheated steam in excess of 400F. Organic fluids such as R245fa require much lower temperatures, 200F. The present invention uses a turbine to generate power with an organic fluid at lower temperatures.

[0003] Conventionally, radial inflow turbines are used with organic fluids for generation of power. However, the disadvantage in such radial inflow turbines is that metallic particles from evaporator or turbine housing get trapped between the turbine wheel and the nozzle block. The trapped particle bounces back and forth resulting in erosion of the wheel.

[0004] Therefore, it is desirable to provide and develop an alternate and improved axial flow turbine for generating power using low grade heat, which is capable to address and overcome the abovementioned disadvantages of conventional radial inflow turbines.

SUMMARY OF THE INVENTION

[0005] Accordingly, it is an object of the present invention to provide a axial flow turbine to generate power using an organic fluid at low temperatures.

[0006] It is another object of the present invention to provide combined hot water and power.

[0007] In accordance with one aspect, the present invention, which achieves the objectives, relates to an axial flow turbine for generating power using an organic fluid at lower temperatures. The axial flow turbine is provided with converging-diverging nozzle such that the high pressure gas is converted to a low pressure high velocity gas by converting the steam's static pressure energy into kinetic energy to drive the turbine rotor. A turbine is associated in such a way that the turbine is operated and driven by extracting thermal energy of the low pressure high velocity gas. An electrical generator is coupled to the turbine such that the electrical generator is operated and driven by rotary motion of the turbine to produce electric power.

[0008] In accordance with another aspect, the present invention, which
achieves the objectives, relates to a system for obtaining both power and hot water output, wherein the high velocity gas (approximately 60 degree Celsius) exit from the turbine can be used for heating the water for domestic purposes and thus the system acts as a combined power and hot water system.

[0009] Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same.

[0011] FIG. 1 shows a cross section of the turbine generator, in accordance with an exemplary embodiment of the present invention.

[0012] FIG. 2 is a solid model cross section of the turbine generator

[0013] FIG. 3 depicts a turbine wheel

[0014] FIG. 4 shows a nozzle block

[0015] FIG. 5 shows a nozzle block cross section

[0016] FIG. 6 depicts a nozzle insert

[0017] FIG. 7 shows a turbine assembly with turbine wheel

[0018] FIG. 8 illustrates a schematic diagram depicting a combined hot water and power generation system using organic fluid, in accordance with an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention describes about an axial flow turbine to generate power using an organic fluid as a working fluid at low temperatures and also to provide combine hot water and power.

[0020] Referring to FIG. 1, a cross section of the turbine generator for generating power with organic fluid as a working fluid is illustrated, in accordance with an exemplary embodiment of the present invention. The present invention relates to an improved axial flow turbine for generating power using low grade heat from bio-mass, solar and gas engine exhaust. The turbine generator comprises a turbine inlet, nozzle housing, turbine wheel, high speed generator, bearings and balancing disks. By using these components and scalability, the turbine generator produces greater thermal efficiency and a significant amount of electrical power is generated.

[0021] In the present invention, high pressure (180 psia) gas at approximately 210F enters the turbine. A set of converging diverging nozzles is provided in the axial flow turbine as shown in FIG. 6. The high pressure gas is accelerated through these set of converging diverging nozzles which is assembled in the housing for producing low pressure high velocity gas. FIG. 4 and FIG. 5 depict the nozzle block and nozzle block cross section. Two converging nozzles are placed around the turbine rotor circumference to balance the driving forces. The converging diverging nozzle is an orifice having a throat area which narrows from inlet to outlet and converts the static pressure energy into kinetic energy to drive the turbine rotor. As the organic fluid travels from inlet to outlet, its pressure decreases and the velocity increases as it moves through the narrowing path. The velocity of the organic fluid is maximum and the pressure is at a minimum where the cross-sectional area is least. The pressure therefore decreases through the turbine. The low pressure high velocity gas impinges on the turbine wheel and the energy is transferred to the wheel which drives the generator shown in FIG. 1 for generating power. The turbine extracts thermal energy from low pressurized high velocity gas and converts it into rotary motion. The energy is thereby extracted from the fluid and the pressure and temperature drop through the turbine. The turbine is coupled to the generator in such a way that the generator can be driven by the rotary motion of the turbine wheel to generate electricity power, which can be used in the residential and commercial complexes. The generator could be either an induction, permanent magnet or switch reluctant type. For 25 KW power output using R245fa organic fluid, the turbine speeds at 15800 rpm for maximum efficiency. Hereafter, the working fluid is referred as organic fluid, for the purpose of explanation. The organic fluid R245fa is a low pressure refrigerant and renders favorable performance in the present invention for greater output of electric power, which increases the overall efficiency of the turbine.

[0022] The nozzle housing is made out of Aluminium and has a 10 holes drilled at angle to route the organic fluid from the inlet to the turbine. The expansion ratio of the organic fluid is from 185 psia to 25 psia and requires a converging-diverging nozzle. The organic fluid is accelerated through the converging-diverging nozzle in a direction such that it is configured to optimize its performance with the turbine wheel. To facilitate manufacturability and assembly, the nozzle as shown in FIG. 6 is a separate piece inserting into the nozzle housing (FIG. 4 and 5).

[0023] A turbine wheel is provided with blades arranged circumferentially which turns the generator. The mean blade speed of the wheel is 0.5 the spouting or jet velocity to give optimum performance. Turbine is mounted on the shaft with a shrink fit. The turbine wheel is also provided with puller holes for assembly and disassembly from the shaft. The outside diameter of the blades is mounted with a ring in order to avoid tip leakage. The turbine wheel is made of Aluminium.

[0024] A high speed two-pole induction generator is used in the prototype.
The rotor is mounted on the shaft with shrink fit. Two disks are provided for balancing the rotor. The disks can be integral part of the rotor end rings.

[0025] The turbine and generator operate at very high speeds for efficient energy conversion. The rotor is therefore supported by refrigerant lubricated ceramic ball bearings for organic fluid application. For air as motive fluid, grease packed sealed ceramic hybrid bearings are used. These bearings provide trouble-free performance at high operating speeds. A layer of grease or refrigerant lubricant separates the dynamic and static components.

[0026] The generator is connected to the grid through a drive that converts the high frequency power to the required 60 Hz or 50 Hz in many countries

[0027] FIG. 8 illustrates a two stage version of the turbine to provide combined power and hot water. The figure is a schematic diagram depicting combined hot water and power generation using low grade heat, in accordance with an exemplary embodiment of the present invention. One variation is that valve 2 is closed and valve 1 is open, in order to obtain maximum power output. Another variation is to close valve 1 and open valve 2, in order to obtain power and hot water output. In the second variation, the check valve 3 ensures that the flow does not go back when operating in combined mode. After power generation, the high velocity gas (approximately 60 degree Celsius) exit from the turbine can be used for heating the water for domestic purposes, and thus the system acts as a combined power and hot water system.

[0028] Another variation of the turbine construction is use of grease lubricated sealed ceramic bearings. This construction is used for generating power with compressed air or nitrogen.

[0029] The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.

[0030] Other modifications will be apparent to those skilled in the art and, therefore, the invention is defined in the claims.

We Claim:

1. An axial flow turbine, comprising:
a turbine inlet through which high pressure gas enters the turbine;

a set of converging diverging nozzle, such that the high pressure gas is converted to a low pressure high velocity gas by converting the steam's static pressure energy into kinetic energy;

a turbine wheel with blades arranged circumferentially and mounted on the shaft with a shrink fit which extracts thermal energy of the low pressure high velocity gas and drives the generator;

bearings to support the turbine wheel rotor which rotates at high operating speed; two balancing disks for balancing the turbine wheel rotor;

coupled to an electrical generator such that said electrical generator is operated and driven by rotary motion of said turbine to produce electric power.

2. An axial flow turbine of claim 1, wherein the mean blade speed of turbine wheel is preferably 0.5 times the spouting or jet velocity.

3. An axial flow turbine of claim 1, wherein a ring is mounted on the outside diameter of the blades to avoid tip leakage.

4. An axial flow turbine of claim 1, further comprising three valves to switch between two modes, namely, maximum power output mode and combined mode of power and hot water output.

5. An axial flow turbine of claim 1, wherein a high pressure gas enters the turbine, preferably at a temperature of 210 degree Fahrenheit with a pressure of 180 psia.

6. An axial flow turbine of claim 1, wherein the turbine wheel is provided with puller holes for assembly and disassembly from the shaft.

7. An axial flow turbine of claim 1, wherein the rotor is supported by refrigerant lubricated ceramic ball bearings for organic fluid application.

8. An axial flow turbine of claim 1, wherein the rotor is supported by grease packed sealed ceramic hybrid bearings when air is used as motive fluid.

9. An axial flow turbine of claim 1, wherein the generator coupled to the turbine may be induction, permanent magnet or switch reluctant type.