Power generating system for a gas turbine engine comprising a compressor bleed air to exhaust heat exchanger

A gas turbine engine comprising:

• a low-pressure (LP) compressor having an LP compressor bleed air passage;
• a high-pressure (HP) compressor having an HP compressor bleed air passage;
• a combustor;
• a turbine section;
• an exhaust section;
• and
• a power generating system including (a) an LP compressor bleed air duct receiving a flow of bleed air from the LP compressor bleed air passage, (b) a heat exchanger arranged within the exhaust section and having a heat exchanger inlet arranged in fluid communication with the LP compressor bleed air duct, and a heat exchanger outlet, the heat exchanger inlet receiving the flow of the bleed air from the LP compressor bleed air duct and providing the flow of the bleed air to flow through the heat exchanger, the heat exchanger receiving a flow of combustion gases from the turbine section, the combustion gases flowing through the heat exchanger and heating the flow of bleed air flowing therethrough to increase a temperature of the flow of the bleed air to generate a flow of heated bleed air, (c) a cooled cooling air heat exchanger arranged in fluid communication with the heat exchanger to receive the flow of the heated bleed air from the heat exchanger, (d) an HP compressor bleed air duct arranged in fluid communication with the cooled cooling air heat exchanger and arranged in fluid communication with the HP compressor bleed air passage, the HP compressor bleed air duct providing a flow of HP compressor bleed air from the HP compressor bleed air passage to the cooled cooling air heat exchanger to further increase a temperature of the heated bleed air to generate an additionally heated bleed air, the additionally heated bleed air being provided from the cooled cooling air heat exchanger to the heat exchanger;
• (e) a power turbine feed duct arranged in fluid communication with the heat exchanger outlet and to receive the flow of the additionally heated bleed air from heat exchanger outlet, (f) a power turbine having a power turbine inlet arranged in fluid communication with the power turbine feed duct and to receive the flow of the additionally heated bleed air from the power turbine feed duct, the flow of the additionally heated bleed air flowing through the power turbine to drive rotation of the power turbine, and (g) a generator connected to the power turbine and driven by the power turbine to generate power.

A method of generating auxiliary power in a gas turbine engine, the gas turbine engine including (a) a low-pressure (LP) compressor having an LP compressor bleed air passage, (b) a high-pressure (HP) compressor having an HP compressor bleed air passage, (c) a combustor, (d) a turbine section, (e) an exhaust section, and (f) a power generating system, the power generating system including (i) an LP compressor bleed air duct arranged in fluid communication with the LP compressor bleed air passage, (ii) a heat exchanger arranged within the exhaust section and having a heat exchanger inlet arranged in fluid communication with the LP compressor bleed air duct, and a heat exchanger outlet, (iii) a cooled cooling air heat exchanger arranged in fluid communication with the heat exchanger, (iv) an HP compressor bleed air duct arranged in fluid communication with the cooled cooling air heat exchanger and arranged in fluid communication with the HP compressor bleed air passage, (v) a power turbine feed duct arranged in fluid communication with the heat exchanger outlet, (vi) a power turbine having a power turbine inlet arranged in fluid communication with the power turbine feed duct, and (vii) a generator connected to the power turbine to be driven by the power turbine to generate power, the method comprising:

• operating the gas turbine engine (1) to cause in an inlet airflow to the gas turbine engine to flow through the LP compressor and the HP compressor, (2) to provide a compressed airflow from the HP compressor to the combustor, (3) to generate combustion gases within the combustor, (4) to provide the combustion gases from the combustor to the turbine section, and (5) to provide the combustion gases from the turbine section to the exhaust section and to flow through the heat exchanger;
• providing a flow of bleed air from the LP compressor bleed air passage to the LP compressor bleed air duct and to the heat exchanger inlet;
• heating, by the combustion gases flowing through the heat exchanger, the flow of bleed air flowing through the heat exchanger to increase a temperature of the flow of the bleed air to generate a flow of a heated bleed air;
• providing the flow of the heated bleed air from the heat exchanger to the cooled cooling air heat exchanger, and providing a flow of the HP compressor bleed air via the HP compressor bleed air duct to the cooled cooling air heat exchanger;
• heating, by the flow of the HP compressor bleed air in the cooled cooling air heat exchanger, the flow of the heated bleed air to generate an additionally heated bleed air, and providing a flow of the additionally heated bleed air from the cooled cooling air heat exchanger to the heat exchanger;
• providing the flow of the additionally heated bleed air to flow out of the heat exchanger outlet to the power turbine feed duct and to the power turbine;
• and
• causing the power turbine to rotate by the additionally heated bleed air flowing through the power turbine, and the generator generating power by the rotation of the power turbine.