Open brayton bottoming cycle and method of using the same

1. An open brayton bottoming cycle comprising:

a heat exchanger configured to receive exhaust heat from an engine and supply at least a portion of the exhaust heat to an expander using a fluid, the expander having an inner rotor configured to spin inside an outer rotor;

a compressor having an inner rotor configured to spin inside an outer rotor, the compressor configured to supply compressed fluid to the heat exchanger, a shaft of the expander connected to the compressor;

a motor/generator component configured to initially be activated as a motor and then as speed increases, re-configure to become a generator that receives energy from the shaft of the expander;

a valve configured to supply fluid to the compressor and to trip when the motor/generator component trips and further configured to be throttled when less power is desired; and

a water injector configured to supply a modulated water flow to the compressor, the modulated water flow modulating a volume entering the heat exchanger and the expander,

wherein each of the compressor and expander have an isentropic efficiency greater than between 80 and 95 percent and the compressor tolerates a presence of water in the fluid.

2. The open brayton bottoming cycle of claim 1 , further comprising an intercooler configured between a first stage and a second stage of the compressor, the intercooler configured to cool the fluid and the water.

3. An open brayton bottoming cycle comprising:

a heat exchanger configured to receive exhaust heat from a heat source and supply at least a portion of the exhaust heat to an expander using a fluid;

a compressor configured to supply compressed fluid to the heat exchanger;

a valve configured to supply fluid to the compressor and to trip when a motor/generator component trips and further configured to be throttled when less power is desired; and

a water injector configured to supply a water flow to the compressor;

wherein the expander has a shaft connected to the compressor and configured to supply energy to the compressor,

wherein the heat source is not configured to burn fuel to drive the shaft; and

wherein at least one of the compressor and the expander comprises a gerotor having an isentropic efficiency between 80 and 95 percent at a power rating below 500 kilowatts.

4. The open brayton bottoming cycle of claim 3 , further comprising a motor/generator component configured to initially be activated as a motor and then as speed increases, re-configure to become a generator that receives energy from the shaft of the expander.

5. The open brayton bottoming cycle of claim 3 , further comprising an intercooler configured between a first stage and a second stage of the compressor, the intercooler configured to cool the fluid.

6. The open brayton bottoming cycle of claim 3 , further comprising an intercooler configured between a first stage and a second stage of the compressor, the intercooler configured to cool the water flow.

7. The open brayton bottoming cycle of claim 3 , wherein the water flow comprises hot water.

8. The open brayton bottoming cycle of claim 3 , further comprising a modulator configured to modulate a volume of the water flow entering the heat exchanger and the expander.

9. The open brayton bottoming cycle of claim 3 , wherein the heat source comprises an engine and the heat comprises exhaust heat from the engine.

10. An open brayton bottoming cycle method comprising:

receiving, using a heat exchanger, exhaust heat from a heat source, the heat exchanger supplying at least a portion of the heat to an expander using a fluid;

supplying, using a compressor, compressed fluid to the heat exchanger; and

supplying energy to the compressor using the expander,

tripping a valve when a motor/generator component trips, the valve throttled when less power is desired, wherein the valve is configured to supply fluid to the compressor; and

supplying a water flow to the compressor using a water injector;

wherein the heat source is not configured to burn fuel to drive a shaft connected to the compressor or expander; and

wherein at least one of the compressor or the expander comprises a gerotor having an isentropic efficiency greater than between 80 and 95 percent at a power rating below 500 kilowatts.

11. The open brayton bottoming cycle method of claim 10 , further comprising initially activating the motor/generator as a motor and then as speed increases, re-configuring the motor/generator as a generator that receives energy from the shaft of the expander.

12. The open brayton bottoming cycle method of claim 10 , further comprising cooling the fluid using an intercooler configured between a first stage and a second stage of the compressor.

13. The open brayton bottoming cycle method of claim 10 , further comprising cooling the water flow using an intercooler configured between a first stage and a second stage of the compressor.

14. The open brayton bottoming cycle method of claim 10 , further comprising modulating a volume of the water flow entering the heat exchanger and the expander.