Patent Description:
Liquid cooled internal combustion engines can reject a significant portion of the heat generated by the fuel to a coolant as intermediate fluid. In applications with increased power density requirements, the inlet pressure to the internal combustion engine is increased with a boost compressor. To satisfy adequate combustion of the fuel in the internal combustion engine and reduce the risk of auto-ignition of the fuel, either directly injected or premixed, an intercooler may be used to cool the air from the boost compressor before it enters the internal combustor engine. For an improved combustion of the fuel in the internal combustion engine, the inlet pressure is cooled by the coolant prior to entering the internal combustion engine.

In a known configuration, the intercooler may be part of a circuit performing two heat-exchange steps. In a first step, hot pressurized air rejects its heat to the coolant via an air-to-liquid heat exchanger. In a second step, the coolant is circulated to another liquid-to-air heat exchanger, to reject the heat to the outside air. In hot days, the coolant temperature may be too high to sufficiently reduce the temperature of pressurized air, i.e., in the case where the maximum acceptable pressurized air temperature which can enter the internal combustion engine is at a similar level as that of the temperature of the coolant.

<CIT> discloses a cooling system comprising a fluid circuit having an intercooler, a main cooler and a precooler, the intercooler configured for receiving coolant and configured for heat exchange relation between the coolant and engine compressed air, the main cooler configured for receiving the coolant from the intercooler and the internal combustion engine and configured for selectively delivering a first portion of the coolant from the main cooler to the precooler, the precooler configured to deliver a flow of the coolant to the intercooler and the main cooler and the precooler configured for cooling the coolant by heat exchange with at least one cooling flow, a bypass valve in fluid communication with the fluid circuit downstream of the main cooler and upstream of the precooler and the intercooler relative to a flow direction of the first portion of the coolant to selectively bypass the precooler and to provide direct fluid communication from the main cooler to the intercooler.

<CIT> discloses a coumpound cycle engine.

<CIT> discloses an adaptive EGR cooling system, <CIT> discloses engine cooling and exhaust gas temperature controls for diesel after-treatment regeneration, and <CIT> discloses a system for ingesting thermal energy for a vehicle motor.

The present invention provides a compound cycle engine as set forth in claim <NUM>.

Referring to <FIG>, a compound cycle engine <NUM> (which is outside the wording of the claims) is schematically shown. The compound cycle engine <NUM> can be used in applications such as aircraft engines (e.g., gas turbine engines) and Auxiliary Power Units (APU). The compound cycle engine <NUM> includes an internal combustion engine <NUM> having one or more rotary unit(s) to drive a common load. In the depicted embodiment, the common load includes an output shaft <NUM> which may be for example connected to a rotary unit such as a propeller or impeller of an aircraft through a reduction gearbox <NUM> and to which the rotary unit is engaged. The compound cycle engine <NUM> may also include a turbocharger <NUM> formed by a compressor <NUM> and a turbine <NUM> which are drivingly interconnected by a shaft <NUM>. The compressor <NUM> of the turbocharger <NUM> compresses the air before the air enters the internal combustion engine <NUM> as pressurized or compressed air 20A. In a particular embodiment, the internal combustion engine <NUM> is a Wankel engine.

The compound cycle engine <NUM> may include a blower <NUM> to circulate a cooling flow along a path of a duct <NUM> of the compound cycle engine <NUM>. The cooling flow can be cooling air or any other suitable cooling fluids, including liquid and/or gaseous coolants. In the embodiment shown, the cooling air circulating within the duct <NUM> flows along an airflow path <NUM>. In a particular embodiment, the blower <NUM> circulates ambient air in the duct <NUM>. A louver system <NUM> is mounted to an inlet <NUM> of the duct <NUM> to control an opening of the inlet <NUM> where the cooling air is drawn into the duct <NUM>. In a particular embodiment, the louver system <NUM> partially closes the opening, for example, when the compound cycle engine <NUM> is operated in flight conditions and opens the opening when the aircraft is on the ground. In the depicted embodiment, an oil cooler <NUM> is mounted inside the duct <NUM> and is fluidly connected with the internal combustion engine <NUM>. The oil cooler <NUM> receives oil from the internal combustion engine <NUM> and cools the oil when circulating the oil in heat exchange relation with the airflow path <NUM>, in a liquid-to-air heat exchanger.

In a particular embodiment, the compound cycle engine <NUM> includes a cooling system <NUM> to cool the compressed air exiting or leaving the compressor <NUM> before the compressed air enters the internal combustion engine <NUM>. The cooling system <NUM> maintains a temperature of the compressed air below a predetermined temperature to satisfy adequate combustion of fuel in the internal combustion engine <NUM> and to reduce the risk of an undesirable auto-ignition of the fuel. In a particular embodiment, the predetermined temperature is <NUM> degrees Celsius. In the depicted embodiment, the cooling system <NUM> may also cool the internal combustion engine <NUM> by circulating coolant in the internal combustion engine <NUM>. The internal combustion engine <NUM> rejects heat generated from the fuel combustion to the coolant of the cooling system <NUM>. Thus, the internal combustion engine <NUM> can incorporate a "heat exchanger" for the purposes of its interaction with the cooling system <NUM>. In a particular embodiment, the coolant includes a mixture of water and an anti-freeze substance. The anti-freeze substance can be any suitable substance such as propylene glycol.

In the depicted embodiment, the cooling system <NUM> has a fluid circuit <NUM> to circulate the coolant between heat exchangers 42A, 42B and 42C of the compound cycle engine <NUM>. The fluid circuit <NUM> can be referred to as a "cooling circuit". The fluid circuit <NUM> fluidly connects the heat exchangers 42A, 42B and 42C with fluid transfer passageways <NUM> to provide fluid communication between the heat exchangers 42A, 42B, 42C. A "direct communication", or "direct fluid communication", between two heat exchangers indicates that a fluid transfer passageway of the fluid circuit <NUM> extends between the two heat exchangers without passing through another, e.g. third, heat exchanger. Heat exchanger 42A provides cooling to the compressed air and heat exchangers 42B and 42C provide cooling to the coolant circulating in the fluid circuit <NUM>.

The cooling system <NUM> includes an intercooler 42A fluidly connected to the compressor <NUM> and to the internal combustion engine <NUM> through an air circuit <NUM>, such that the compressed air exiting the compressor <NUM> passes through the intercooler 42A before entering the internal combustion engine <NUM>. In the embodiment shown, the intercooler 42A is an air-to-liquid heat exchanger. The compressed air passes through the intercooler 42A through an air inlet and exits the intercooler through an air outlet. The intercooler 42A is also fluidly connected to the fluid circuit <NUM> to circulate the coolant within the intercooler 42A in heat exchange relation with the compressed air. In a particular embodiment, the coolant enters the intercooler 42A through a coolant inlet, circulate through the intercooler 42A and exits the intercooler 42A through a coolant outlet.

The cooling system <NUM> further include a main cooler 42B and a precooler 42C to cool the coolant circulating in the fluid circuit <NUM> to a desired temperature. In normal operation, the cooling system <NUM> maintains a temperature of the coolant entering the intercooler 42A at a lower temperature than the temperature of the compressed air, to cool the compressed air before it enters the internal combustion engine <NUM>. In the embodiment shown, the main cooler 42B and precooler 42C are air-to-liquid heat exchangers. These two coolers 42B, 42C can be disposed within the duct <NUM> across the airflow path <NUM> to circulate the coolant therein in heat exchange relation with air of the airflow path <NUM> to cool the coolant. The speed of the blower <NUM> can be changed to vary the flow of the air within the airflow path <NUM> and consequently vary the amount of heat removed from the coolant, based on cooling requirements.

The main cooler 42B is in fluid communication with the intercooler 42A through the fluid circuit <NUM> to receive the coolant from the intercooler 42A. In the embodiment shown, the main cooler 42B is in direct communication with the intercooler 42A through fluid transfer passageway <NUM>. The main cooler 42B is also in fluid communication with the internal combustion engine <NUM> to receive the coolant from the internal combustion engine <NUM> and to selectively deliver the coolant back to the internal combustion engine <NUM>. In the depicted embodiment, the main cooler 42B is in direct communication with the internal combustion engine <NUM> through fluid transfer passageway <NUM> to supply the internal combustion engine <NUM> with the cooled coolant. The internal combustion engine <NUM> is also in direct communication with the main cooler 42B through fluid transfer passageway <NUM> to deliver the heated coolant to the main cooler 42B. The main cooler 42A has respective inlets and outlets to fluidly communicate with the internal combustion engine <NUM> through the fluid transfer passageways <NUM>, <NUM>.

The precooler 42C is in fluid communication with the main cooler 42B to selectively receive a portion of the coolant exiting the main cooler 42B. For example, in certain operating conditions, no coolant is delivered from the main cooler 42B to the precooler 42C. In a particular embodiment, a remainder of the coolant exiting the main cooler 42B is received by the internal combustion engine <NUM>. In another embodiment, another portion of the coolant exiting the main cooler 42B is delivered to the internal combustion engine <NUM>. The proportion of the coolant sent to the internal combustion engine <NUM> versus the coolant sent to the precooler 42C can be adjusted based on ambient conditions and power requirements of the compound cycle engine <NUM>. The portion of the coolant exiting the main cooler 42B and entering the precooler 42C is further cooled in the precooler 42C, separately from the main cooler 42B. This portion of the coolant is thus cooled in a first step by the main cooler 42B and consecutively cooled in a second step by the precooler 42C. The precooler 42C is in direct communication with the main cooler 42B through fluid transfer passageway <NUM>. The precooler 42C has respective inlets and outlets to fluidly communicate with the main cooler 42B through the fluid transfer passageway <NUM>.

In the embodiment shown, the fluid transfer passageway <NUM> passes through a control valve <NUM> downstream of the main cooler 42B and upstream of the precooler 42C relative to a direction of the coolant exiting the main cooler 42B. The control valve <NUM> controls a flow of the portion of the coolant entering the precooler 42C.

In the embodiment shown, the control valve <NUM> is adapted to receive a signal <NUM> representative of the temperature of the compressed air exiting the intercooler 42A to determine a flow rate of coolant entering the precooler 42C. Any suitable temperature sensor can be used to measure the temperature of the compressed air exiting the intercooler 42A. On hot or warmer days, higher flow rates of coolant entering the precooler 42C may be required to adequately cool the compressed air entering the intercooler 42A. As such, all of the coolant exiting the main cooler 42B may be delivered to the precooler 42C.

Consequently, the precooler 42C is in fluid communication with the intercooler 42A to deliver the coolant from precooler 42C to the intercooler 42A. In the depicted embodiment, the precooler 42C is in direct communication with the intercooler 42A through fluid transfer passageway <NUM>. This configuration can allow a flow of the coolant entering the intercooler 42A to be equal to the flow of the coolant entering the precooler 42C. Consequently, the flow of the coolant entering the intercooler 42A can be adjusted by adjusting the flow of the coolant entering the precooler 42C via the control valve <NUM>. The precooler 42C has respective inlets and outlets to fluidly communicate with the intercooler 42A through the fluid transfer passageway <NUM>.

The cooling system <NUM> includes a pump <NUM> in fluid communication with the fluid circuit <NUM> to pump the coolant at an increased pressure and to circulate the coolant along the fluid circuit <NUM>. The pump <NUM> is located downstream of the main cooler 42B relative to the direction of the coolant exiting the main cooler 42B. In an alternate embodiment, the pump <NUM> is located at any other suitable location within the fluid circuit <NUM> or the internal combustion engine <NUM>.

In a particular embodiment, for example on cooler days, a portion of the coolant exiting the main cooler 42B is directed to the intercooler 42A and a remainder of the coolant exiting the main cooler 42B is directed to the internal combustion engine <NUM>. The cool ambient air may be sufficient to cool the coolant within the main cooler 42B to the desired temperature. On warmer days, the ambient air may be too warm to adequately and efficiently cool the coolant within the main cooler 42B to the desired temperature, thus a portion of the coolant exiting the main cooler 42B is directed to the precooler 42C so that the coolant is cooled twice before it enters the intercooler 42A to enable cooling the compressed air temperature coming out of the intercooler 42A to an acceptable level. This arrangement can be well suited for conditions of high temperature on the ground.

Referring to <FIG>, the compound cycle engine <NUM> is schematically shown according to an alternate embodiment. Due to a similarity in components between the engine <NUM> of <FIG> and engine <NUM> of <FIG>, like components will bear like reference numerals. According to the invention, the cooling system <NUM> includes a bypass valve <NUM> in fluid communication with the main cooler 42B and in fluid communication with the precooler 42C. The bypass valve <NUM> is located downstream of the main cooler 42B and located upstream of the precooler 42C relative to the direction of the coolant exiting the main cooler 42B. The bypass valve <NUM> directly interconnects the fluid transfer passageway <NUM> with the fluid transfer passageway <NUM> to selectively bypass the precooler 42C and to direct a selected portion of the coolant exiting the main cooler 42B directly to the intercooler 42A.

The cooling system <NUM> may also include a regulating valve <NUM> in fluid communication with and downstream of the intercooler 42A relative to a direction of the coolant exiting the intercooler 42A to regulate a flow of the coolant directly downstream of the intercooler 42A. The regulating valve <NUM> may be used to control the amount of coolant passing through the intercooler 42A versus the amount of coolant fed to the engine <NUM>. The regulating valve <NUM> may cause a flow restriction to limit the amount of coolant passing through the intercooler 42A.

The cooling system <NUM> may also include a bypass valve <NUM> downstream of the intercooler 42A to selectively bypass the main cooler 42B and to deliver at least a portion of the coolant directly downstream of the main cooler 42B and/or to the internal combustion engine <NUM>.

In a particular embodiment, the coolant is circulated in the cooling system <NUM>, <NUM> by directing the coolant from the internal combustion engine <NUM> after absorbing heat therefrom to the main cooler 42B for the coolant to release heat to the air of the airflow path; directing a portion of the coolant exiting the main cooler 42B to the precooler 42C for the portion of the coolant to further release heat to the air of the airflow path, while directing the remainder of the coolant exiting the main cooler 42B to the internal combustion engine <NUM>; directing the portion of the coolant from the precooler 42C to the intercooler 42A to cool the compressed air within the intercooler 42A upon circulating the coolant in heat exchange relation with the compressed air; and directing the coolant from the intercooler 42A to the main cooler 42B. In an alternate embodiment, another portion of the coolant exiting the main cooler 42B is directed to the intercooler 42A. In yet an alternate embodiment, another portion of the coolant exiting the main cooler 42B is directed to the internal combustion engine <NUM>.

In a further alternate embodiment, a flow of each portion of the coolant exiting the main cooler 42B is determined based on the temperature of the compressed air exiting the intercooler 42A and optionally based on the ambient temperature.

Claim 1:
A compound cycle engine (<NUM>) comprising:
an internal combustion engine (<NUM>);
a compressor (<NUM>) having compressed air (20A) delivered to the internal combustion engine (<NUM>);
a cooling system (<NUM>;<NUM>) comprising:
a fluid circuit (<NUM>) having an intercooler (42A), a main cooler (42B) and a precooler (42C), the intercooler (42A) configured for receiving coolant and configured for heat exchange relation between the coolant and engine compressed air (20A), the main cooler (42B) configured for receiving the coolant from the intercooler (42A) and the internal combustion engine (<NUM>), and configured for selectively delivering a first portion of the coolant from the main cooler (42B) to the precooler (42C), the precooler (42C) configured to deliver a flow of the coolant to the intercooler (42A), and the main cooler (42B) and the precooler (42C) configured for cooling the coolant by heat exchange with at least one cooling flow; and
a bypass valve (<NUM>) in fluid communication with the fluid circuit downstream of the main cooler (42B) and upstream of the precooler (42C) and the intercooler (42A) relative to a flow direction of the first portion of the coolant to selectively bypass the precooler (42C) and to provide direct fluid communication from the main cooler (42B) to the intercooler (42A);
a duct (<NUM>) receiving the main cooler (42B) and the precooler (42C), the duct (<NUM>) including a blower (<NUM>) to circulate the at least one cooling flow in heat exchange relation with the coolant in the main cooler (42B) and the precooler (42C); and
an oil cooler (<NUM>) disposed in the duct (<NUM>) and in fluid communication with oil from the internal combustion engine (<NUM>), the oil cooler (<NUM>) configured for heat exchange relation between the oil and the at least one cooling flow to cool the oil.