Bottoming cycle for waste heat recovery and engine cooling
A gas turbine engine assembly includes a core engine that includes a core flow path where a core airflow is compressed in a compressor section, communicated to a combustor section, mixed with fuel and ignited to generate an exhaust gas flow that is expanded through a turbine section. The turbine section is coupled to drive the compressor section through an engine drive shaft. A tap is at a location up stream of the combustor section for drawing a bleed airflow. A bleed air heat exchanger places the bleed airflow in thermal communication with an auxiliary flow for heating the bleed airflow. An exhaust heat exchanger is configured to transfer thermal energy from the exhaust gas flow into the bleed airflow.
1. A gas turbine engine assembly comprising:
a core engine including a core flow path where a core airflow is compressed in a compressor section, communicated to a combustor section, mixed with fuel and ignited to generate an exhaust gas flow that is expanded through a turbine section, wherein the turbine section is coupled to drive the compressor section through an engine drive shaft;
a tap at a location up stream of the combustor section for drawing a bleed airflow;
a bleed air heat exchanger placing the bleed airflow in thermal communication with an auxiliary flow for heating the bleed airflow, wherein the auxiliary flow comprises a flow at an elevated temperature that is greater than the bleed airflow and is communicated to an environmental control system after the bleed air heat exchanger;
an exhaust heat exchanger configured to transfer thermal energy from the exhaust gas flow into the bleed airflow; and
a first control device configured to control flow of the bleed airflow from the tap to the bleed air heat exchanger and a controller programmed to control operation of the first control device in response to a control input, wherein the control input is indicative of an engine operating condition.
2. The gas turbine engine as recited in claim 1 , including a power turbine including an inlet receiving a heated bleed airflow, wherein the power turbine is mechanically coupled to the engine drive shaft.
3. The gas turbine engine as recited in claim 2 , including a gearbox coupling the power turbine to the engine drive shaft.
4. The gas turbine engine as recited in claim 2 , wherein the compressor section includes a low pressure compressor coupled to a low pressure turbine section by the engine drive shaft.
5. The gas turbine engine as recited in claim 2 , wherein the compressor section includes a high pressure compressor coupled to a high pressure turbine section by the engine drive shaft.
6. The gas turbine engine as recited in claim 1 , wherein the compressor section includes a low-pressure compressor disposed upstream of the combustor section and the tap is located downstream of the low-pressure compressor and upstream of the combustor section.
7. The gas turbine engine assembly as recited in claim 1 , including an environmental control system receiving the auxiliary flow exhausted from the bleed air heat exchanger.
8. The turbine engine as recited in claim 1 , wherein the controller is further programmed to control a power turbine to supplement engine operation by supplying power to the engine drive shaft.
9. A waste heat recovery system for a gas turbine engine, the waste heat recovery system comprising:
a first tap drawing bleed airflow from a core flow path up stream of a combustor section of the gas turbine engine;
a bleed air heat exchanger placing the bleed airflow in thermal communication with an auxiliary flow for heating the bleed airflow, wherein the auxiliary flow comprises a flow at an elevated temperature that is greater than the bleed airflow and is communicated to an environmental control system after the bleed air heat exchanger; and
an exhaust heat exchanger configured to transfer thermal energy from the exhaust gas flow into the bleed airflow; and
a power turbine including an inlet receiving a heated bleed airflow, wherein the power turbine is configured to generate a mechanical power output;
a first control device configured to control flow of the bleed airflow from the first tap to the bleed air heat exchanger; and
a controller programmed to control operation of the first control device in response to a control input.
10. The waste heat recovery system as recited in claim 9 , including an auxiliary system receiving the auxiliary flow exhausted from the bleed air heat exchanger.
11. The waste heat recovery system as recited in claim 10 , including a coolant loop system with a coolant heat exchanger that places a coolant flow in thermal communication with the bleed airflow.
12. The waste heat recovery system as recited in claim 9 , further comprising a gearbox coupled to the power turbine and configured to supplement power to an engine shaft of a core engine.
13. A method of operating a gas turbine engine assembly comprising:
generating an exhaust gas flow by igniting a fuel mixed with a core airflow in a core engine, wherein the core engine includes a compressor section coupled to a turbine section through an engine shaft;
communicating a portion of the core airflow as a bleed airflow through a tap located upstream of a combustor section;
heating the bleed airflow with an auxiliary flow for an auxiliary system within a bleed air heat exchanger, wherein the auxiliary flow comprises a flow at an elevated temperature that is greater than the bleed airflow and is communicated to an environmental control system after the bleed air heat exchanger;
heating bleed airflow in an exhaust heat exchanger in thermal communication with the combusted gas flow; and
generating shaft power by expanding at least a portion of heated bleed airflow through a power turbine;
coupling the engine shaft to the power turbine and applying a drive input to the engine shaft with the power turbine.
14. The method as recited in claim 13 , including transferring thermal energy from the exhaust gas flow through a coolant loop to the bleed air flow.
15. The method as recited in claim 13 , further comprising providing a gearbox coupling the power turbine to the engine shaft and preventing back driving of the power turbine by the engine shaft.
16. The method as recited in claim 13 , further comprising controlling the bleed airflow with a first control device configured to control flow of the bleed airflow from the tap to the bleed air heat exchanger and a controller programmed to control operation of the first control device in response to a control input, wherein the control input is indicative of an engine operating condition.