Patent Description:
Performance of aircraft engines during start-up are not as good as during steady state operation because the various engine components and fluids are not at their optimal operational temperatures. After the aircraft engine is shutdown, a substantial amount of time lapses before the engine cools down. Moreover, it is a constant challenge to provide sufficient cooling to the hot components of an aircraft engine. Improvements are therefore suitable.

<CIT> discloses an engine assembly according to the preamble of claim <NUM>, and a method according to the preamble of claim <NUM>.

<CIT> discloses a method and system for managing heat flow in an engine.

According to a first aspect, there is provided an engine assembly for an aircraft as set forth in claim <NUM>.

According to a further aspect, there is provided a method as set forth in claim <NUM>.

Referring to <FIG>, a rotary internal combustion engine <NUM> known as a Wankel engine is schematically shown. The rotary engine <NUM> comprises an outer body <NUM> having axially-spaced end walls <NUM> with a peripheral wall <NUM> extending therebetween to form a rotor cavity <NUM>. The inner surface of the peripheral wall <NUM> of the cavity <NUM> has a profile defining two lobes, which is preferably an epitrochoid.

An inner body or rotor <NUM> is received within the cavity <NUM>. The rotor <NUM> has axially spaced end faces <NUM> adjacent to the outer body end walls <NUM>, and a peripheral face <NUM> extending therebetween. The peripheral face <NUM> defines three circumferentially-spaced apex portions <NUM>, and a generally triangular profile with outwardly arched sides <NUM>. The apex portions <NUM> are in sealing engagement with the inner surface of peripheral wall <NUM> to form three rotating combustion chambers <NUM> between the inner rotor <NUM> and outer body <NUM>. The geometrical axis of the rotor <NUM> is offset from and parallel to the axis of the outer body <NUM>.

The combustion chambers <NUM> are sealed. In the embodiment shown, each rotor apex portion <NUM> has an apex seal <NUM> extending from one end face <NUM> to the other and biased radially outwardly against the peripheral wall <NUM>. An end seal <NUM> engages each end of each apex seal <NUM> and is biased against the respective end wall <NUM>. Each end face <NUM> of the rotor <NUM> has at least one arc-shaped face seal <NUM> running from each apex portion <NUM> to each adjacent apex portion <NUM>, adjacent to but inwardly of the rotor periphery throughout its length, in sealing engagement with the end seal <NUM> adjacent each end thereof and biased into sealing engagement with the adjacent end wall <NUM>. Alternate sealing arrangements are also possible.

Although not shown in the Figures, the rotor <NUM> is journaled on an eccentric portion of a shaft such that the shaft rotates the rotor <NUM> to perform orbital revolutions within the stator cavity <NUM>. The shaft rotates three times for each complete rotation of the rotor <NUM> as it moves around the stator cavity <NUM>. Oil seals are provided around the eccentric to impede leakage flow of lubricating oil radially outwardly thereof between the respective rotor end face <NUM> and outer body end wall <NUM>. During each rotation of the rotor <NUM>, each chamber <NUM> varies in volumes and moves around the stator cavity <NUM> to undergo the four phases of intake, compression, expansion and exhaust, these phases being similar to the strokes in a reciprocating-type internal combustion engine having a four-stroke cycle.

The engine includes a primary inlet port <NUM> in communication with a source of air, an exhaust port <NUM>, and an optional purge port <NUM> also in communication with the source of air (e.g. a compressor) and located between the inlet and exhaust ports <NUM>, <NUM>. The ports <NUM>, <NUM>, <NUM> may be defined in the end wall <NUM> of in the peripheral wall <NUM>. In the embodiment shown, the inlet port <NUM> and purge port <NUM> are defined in the end wall <NUM> and communicate with a same intake duct <NUM> defined as a channel in the end wall <NUM>, and the exhaust port <NUM> is defined through the peripheral wall <NUM>. Alternate configurations are possible.

In a particular embodiment, fuel such as kerosene (jet fuel) or other suitable fuel is delivered into the chamber <NUM> through a fuel port (not shown) such that the chamber <NUM> is stratified with a rich fuel-air mixture near the ignition source and a leaner mixture elsewhere, and the fuel-air mixture may be ignited within the housing using any suitable ignition system known in the art (e.g. spark plug, glow plug). In a particular embodiment, the rotary engine <NUM> operates under the principle of the Miller or Atkinson cycle, with its compression ratio lower than its expansion ratio, through appropriate relative location of the primary inlet port <NUM> and exhaust port <NUM>.

Referring now to <FIG>, an engine assembly is generally shown at <NUM>. The engine assembly <NUM> may be an auxiliary power unit of an aircraft. The engine assembly <NUM> includes an internal combustion engine <NUM>, which may be the rotary engine <NUM> described herein above with reference to <FIG>. Alternatively, the internal combustion engine <NUM> may be any suitable engine. The internal combustion engine <NUM> may be a reciprocating engine, such as a piston engine. In a particular embodiment, the internal combustion engine <NUM> may be part of an engine system being a compound cycle engine system or compound cycle engine such as described in <CIT> or as described in <CIT>, or as described in <CIT>, or as described in<CIT>.

The internal combustion engine <NUM> is fluidly connected to an engine inlet <NUM>, which is fluidly connected to an environment E outside the engine assembly <NUM>.

In the embodiment shown, the engine assembly <NUM> includes a gearbox <NUM> in driving engagement with the internal combustion engine <NUM>. More specifically, the internal combustion engine <NUM> has an engine shaft 110a that is connected to an input 112a of the gearbox <NUM>. The gearbox <NUM> may be connected to a plurality of components to transmit a rotational input from the engine shaft 110a. The gearbox <NUM> may create a rotational speed ratio between its input 112a and its output 112b.

In the embodiment shown, the engine assembly <NUM> includes a heat management system <NUM>. The heat management system <NUM> includes a coolant circuit <NUM> configured for circulating a liquid coolant. The coolant circuit <NUM> is in heat exchange relationship with the internal combustion engine <NUM>. In a particular embodiment, the internal combustion engine <NUM> includes a housing, such as the peripheral wall <NUM> of the rotary engine of <FIG>, that defines conduits therein; the conduits being fluidly connected to the coolant circuit <NUM>. The liquid coolant might be able to cool the internal combustion engine <NUM> by picking up heat from its housing, via convection. Consequently, a temperature of the liquid coolant increases following its passage through the housing.

For inducing a flow of the liquid coolant within the coolant circuit <NUM>, the engine assembly <NUM> includes a pump <NUM> fluidly connected to the coolant circuit <NUM>. The pump <NUM> may be drivingly engaged by the internal combustion engine <NUM> and/or by an electric motor <NUM>, which is powered by a power source S. In a particular embodiment, the power source S is a battery <NUM>. Alternatively, the power source S may be a generator drivingly engaged by either the internal combustion engine <NUM> or by another engine of an aircraft containing the engine assembly <NUM>.

In the embodiment shown, the heat management system <NUM> includes an expansion tank <NUM> fluidly connected to the coolant circuit <NUM>. The expansion tank <NUM> may be pressurized at a given pressure, which may be <NUM> PSI (<NUM>. 3kPa), and may be used for catering for thermal-induced volume variations of the liquid coolant.

In certain situations, it might be useful to circulate the liquid coolant in the coolant circuit <NUM> when the internal combustion engine <NUM> is powered off, shutdown, or off. Herein, by being powered off, shutdown, or off implies that the internal combustion engine does not induce rotation of the engine shaft 110a. In other words, by being powered off, shutdown, or off, there is no combustion occurring in the combustion chamber(s) of the internal combustion engine <NUM>.

In the embodiment shown, the pump <NUM> is selectively drivingly engaged by the internal combustion engine <NUM> or the electric motor <NUM>. In the depicted embodiment, the pump <NUM> is drivingly engaged by the internal combustion engine via the gearbox <NUM>.

To allow the pump <NUM> to be engaged by the electric motor <NUM>, the engine assembly <NUM> includes a clutch <NUM> having an input 124a being in driving engagement with the internal combustion engine <NUM> via the gearbox <NUM> and an output 124b being in driving engagement with the pump <NUM>. The clutch <NUM> is operable in a first configuration in which the input 124a is in driving engagement with the output 124b and a second configuration in which the input 124a is disengaged from the output 124b. Consequently, in the first configuration, the internal combustion engine <NUM> drives the pump <NUM> and, in the second configuration, the internal combustion engine <NUM> is disengaged from the pump <NUM>. By being in the second configuration, the clutch <NUM> allows the electric motor <NUM> to drive the pump <NUM> without having to overcome a load created by the internal combustion engine <NUM> being off.

In a particular embodiment, the clutch <NUM> is a sprag clutch. In the sprag clutch, the input 124a drivingly engages the output 124b if the input 124a rotates at a greater speed than that of the output 124b and allows the output 124b to rotate independently of the input 124a if the output 124b rotates at a speed greater than that of the input 124a.

The heat management system <NUM> further includes a heat sink <NUM> in heat exchange relationship with the coolant circuit <NUM>. In the embodiment shown, the heat sink <NUM> includes a heat exchanger <NUM>. The heat generated by said engine <NUM> has to be dissipated in the environment E. The heat exchanger <NUM> might be used for that purpose.

More specifically, and in the embodiment shown, the heat exchanger <NUM> includes at least one first conduit 128a and at least one second conduit 128b in heat exchange relationship with the at least one first conduit 128b. The at least one first conduit 128a is fluidly connected to the coolant circuit <NUM> and the at least one second conduit 128b is fluidly connected to the environment E. A blower B may be used to induce a flow of air from the environment E through the at least one second conduit 128b of the heat exchanger <NUM>. In a particular embodiment, the blower B may be replaced by a scoop located on an external surface of the aircraft. A temperature of the air in the environment E is usually lower than a temperature of the liquid coolant that picked up heat from the internal combustion engine <NUM>. Consequently, a heat transfer occurs from the liquid coolant to the environment E within the heat exchanger <NUM>.

Managing heat of the internal combustion engine <NUM> is always a challenge. Therefore, it might be advantageous to help the heat exchanger <NUM> in dissipating the heat generated by combustion occurring in the combustion chamber(s) of the internal combustion engine <NUM>.

In the embodiment shown, the heat sink <NUM> further includes at least one component <NUM> of the engine assembly <NUM>. The component <NUM> is thermally disconnected from the heat exchanger <NUM>. Herein, thermally disconnected implies that the component <NUM> does not rely on the heat exchanger for being cooled. Stated otherwise, the component <NUM>, contrary to the internal combustion engine <NUM>, is not liquid cooled. Again, in other words, when the internal combustion engine <NUM> is on and combustion occurs in the chamber(s), a temperature of said engine <NUM>, more specifically of the liquid coolant exiting said engine <NUM>, is greater than that of the component <NUM>. Hence, a heat transfer might occur from the liquid coolant that has been heated by the internal combustion engine <NUM> to the component <NUM>. The at least one main component <NUM> has a main function that is different than exchanging heat. That is, the main purpose of the inclusion of the at least one component <NUM> in the engine assembly is to carry a function that is not related to cooling/heating.

The component <NUM> may then dissipate the heat it received from the internal combustion engine <NUM> via the liquid coolant to the environment E. In a particular embodiment, the component <NUM> is air cooled by ambient air circulating within a compartment of the aircraft containing the engine assembly <NUM>. In a particular embodiment, the compartment is an APU compartment of the aircraft.

In the embodiment shown, the at least one component <NUM> includes two components being the gearbox <NUM> and the engine inlet <NUM>. The at least one component <NUM> may be either of the gearbox <NUM>, the engine inlet <NUM>, a compressor, a turbine, and so forth. In the embodiment shown, the component <NUM> is operatively connected to the internal combustion engine <NUM>. It is understood that the component <NUM> need not be operatively connected to the internal combustion engine <NUM>. The component <NUM> may be any other component of the aircraft. For instance, the component <NUM> may be an engine starter, a generator, a load compressor, an air filter, an actuators, a valve, any component having at least one moveable part, a Line Replacement Unit (LRU), and so on. In a particular embodiment, having the at least one component <NUM> being the engine inlet <NUM> allows to de-ice, or prevent ice from accumulating on, said inlet <NUM>. All of the above listed possibilities of the at least one component <NUM> have a main function that differs from thermal exchange. For instance, the main function of the engine starter is to start the engine, that of the generator is to produce electricity, that of the load compressor is to compress air for a cabin of an aircraft equipped with the engine assembly, that of the actuators is to move another component, that of the valve is to allow or block fluid communication between two components, that of the compressor is to compress air before it is fed to the combustion engine, that of the turbine is to extract energy from combustion gases exiting the combustion engine.

In the embodiment shown, the coolant circuit <NUM> includes a conduit 116a that is in heat exchange relationship with the at least one component <NUM>. The conduit 116a may be in contact with the component <NUM> such that the conduit 116a is conductively thermally connected with the component <NUM>. Herein, conductively thermally connected implies that heat is transferred between the conduit 116a and the component <NUM> via conduction. The conduit 116a is wrapped around the component <NUM>. The conduit 116a may be simply in contact with the component <NUM> or secured thereto with any suitable mean, such as by welding. Alternatively, or in combination, channels may be defined in the component <NUM> for fluidly receiving the liquid coolant. Stated otherwise, cooling chambers and channels may be located around the component <NUM>.

In a particular embodiment, the conduit 116a is selectively connected to a remainder of the coolant circuit <NUM>. In other words, a valve <NUM> may be located on the coolant circuit <NUM>. The valve <NUM> may be operated in a first mode in which it allows the liquid coolant to circulate within the conduit 116a and a second mode in which it prevents the liquid coolant to flow within the conduit 116a. This might allow to selectively use the component <NUM> to help the heat exchanger <NUM> in dissipating the heat generated by the internal combustion engine <NUM> when needed. Having the ability to fluidly disconnect the conduit 116a from the remainder of the coolant circuit <NUM> might allow the pump to consume less energy because it does not have to overcome a pressure drop that might occur by circulating the liquid coolant within the conduit 116a.

In some flight phases, the internal combustion engine <NUM> has to be powered on after being exposed to very cold ambient temperatures for prolonged time. It might be advantageous to warm-up certain components of the engine assembly <NUM> prior to starting the internal combustion engine <NUM>. More specifically, if the engine assembly <NUM> is an APU, the internal combustion engine <NUM> is off for substantially a whole of a cruise phase. When shifting to an approach phase prior to landing, power to main engines of the aircraft is reduced and, consequently, they might not be able to provide all the electricity and compressed air required by the aircraft. Then, the APU is powered on to generate that electricity and compressed air that was previously generated by the main engines during cruise. However, starting the engine <NUM> in such cold operating conditions might require a relatively long warm up period during which efficiency of the engine assembly <NUM> is less than its nominal, or steady state efficiency. This might imply that the internal combustion engine <NUM> consumes more fuel during the warm up phase than during a steady state operation phase. It might be advantageous to reduce a duration of the warm up phase to reduce fuel consumption of the engine <NUM>.

In the embodiment shown, the engine assembly <NUM> includes a heat source <NUM> being in heat exchange relationship with the coolant circuit <NUM> for heating the liquid coolant circulating therethrough and, as will be discussed below, for heating the component <NUM> prior to powering on the engine <NUM>. The heat source <NUM> may be an electric heater operatively connected to the power source S. The heat source <NUM> may be another heat exchanger of the aircraft. Any suitable heat source may be used without departing from the scope of the present disclosure.

In some other flight phases, the internal combustion engine <NUM> has to be powered off. However, when the internal combustion engine <NUM> has been operating for a prolonged amount of time, it might be very hot. It might be advantageous to continue circulating the liquid coolant to cool down the internal combustion engine <NUM> after it has been powered off.

In the embodiment shown, after the internal combustion engine <NUM> has been powered off, the pump <NUM> may continue to be operated using the electric motor <NUM>. Continuing to circulate the liquid coolant after the engine <NUM> is powered off might decrease a cool down time compared to a configuration in which the liquid coolant stops circulating in the coolant circuit after the engine <NUM> is shut down. Dissipating the heat via both of the component <NUM> and the heat exchanger <NUM> might decrease the cool down time compared to a configuration in which only the heat exchanger <NUM> is used to dissipate the heat of the internal combustion engine <NUM>. In a particular embodiment, decreasing the cool down time increases a lifetime of the engine. Decreasing the cool down time might allow to reduce the fuel consumption because the engine does not have to run for as long for achieving the same decrease in temperature.

For operating the heat management system <NUM>, the liquid coolant is circulated. Heat is transferred from the internal combustion engine <NUM> to the liquid coolant. The heat is transferred from the liquid coolant to the environment E outside the engine assembly <NUM> via both of the heat exchanger <NUM> and the component <NUM> that is thermally disconnected from the heat exchanger <NUM>.

In the embodiment shown, transferring the heat to the environment E via the component <NUM> includes transferring heat to the gearbox <NUM> of the engine assembly <NUM>. In the embodiment shown, transferring the heat to the environment E via the component <NUM> includes transferring the heat to the component <NUM> which is operatively connected to the internal combustion engine <NUM>.

In the depicted embodiment, circulating the liquid coolant includes actuating the pump <NUM> with one of the electric motor <NUM> and the engine shaft 110a of the internal combustion engine <NUM>. Actuating the pump with the electric motor <NUM> may include disengaging the engine shaft 110a from the pump <NUM>.

Referring now to <FIG>, a control system for controlling the heat management system <NUM> is generally shown at <NUM>. The control system <NUM> includes a controller <NUM> including a processor <NUM> and a computer readable medium <NUM> operatively connected to the processor <NUM> and having stored thereon instructions executable by the processor <NUM> for controlling the heat management system <NUM>. As shown, the controller <NUM> is operatively connected to an aircraft bus <NUM>, which may be a 28V bus.

The controller <NUM> is configured for determining that the internal combustion engine <NUM> of the engine assembly <NUM> is off, circulating the liquid coolant in the coolant circuit <NUM> for heating the liquid coolant, and circulating the heated liquid coolant toward the at least one component <NUM> being thermally disconnected from the heat exchanger <NUM> of the engine assembly <NUM> for transferring heat from the heated liquid coolant to the at least one component <NUM>.

In a particular embodiment, determining that the internal combustion engine <NUM> is off includes determining that the internal combustion engine <NUM> is cold. In such a case, heating the liquid coolant includes heating the liquid coolant with the heat source <NUM>. The heated liquid coolant may then be used for heating the engine <NUM> and the component <NUM>.

In a particular embodiment, determining that the internal combustion engine <NUM> is off includes determining that the internal combustion engine <NUM> is hot, or above a given temperature. In such a case, heating the liquid coolant includes transferring heat from the internal combustion engine <NUM> to the liquid coolant.

In a particular embodiment, determining that the internal combustion engine <NUM> is off further includes determining that the engine assembly <NUM> is below a given temperature. Alternatively, determining that the internal combustion engine <NUM> is off further includes determining that a flight phase of the aircraft is an approach phase and that the engine <NUM> needs to be started.

In a particular embodiment, the controller <NUM> is operatively connected to at least one sensor <NUM>. As shown in <FIG>, the at least one sensor <NUM> includes a coolant temperature sensor 216a and a coolant pressure sensor 216b both of which may be operatively connected to an engine control unit (ECU) <NUM>. As shown, the engine control unit <NUM> is operatively connected to the controller <NUM>. The coolant temperature sensor 216a may be used for monitoring a temperature of the component <NUM> whereas the coolant pressure sensor 216b may be used for monitoring a pressure of the coolant. The controller <NUM> may start the circulation of the liquid coolant and the actuation of the heat source <NUM> to warm the component <NUM> if one or both of the monitored temperature and the monitored pressure reaches a respective given threshold.

As illustrated on <FIG>, the engine control unit <NUM> is operatively connected to the power source S. As shown, the controller <NUM> is operatively connected to the power source S via the engine control unit <NUM>.

The valve <NUM> is operatively connected to the engine control unit <NUM> and to the controller <NUM>. In other words, the valve <NUM> is operatively connected to the controller <NUM> via the engine control unit <NUM>. In the embodiment shown, the pump <NUM> is electrically driven to turn ON/OFF pumping at any time to warm up or cool down the hardware (e.g., engine <NUM>) when the engine <NUM> is shut down. The valve, or control valve, <NUM> may offer the possibility to allow the coolant fluid to flow as needed in specific engine modules before engine start, in operation and after shutdown. Depending of the temperature and pressure of the coolant and the engine state, the ECU <NUM> might have a logic to open up the required cooling channels. Multiple temperature sensing points may be used.

In one embodiment, the control system <NUM> may monitor critical components temperature during flight and turn ON the pump <NUM> as needed to warm up.

In a particular embodiment, depending of the application, the cooling pump <NUM> can be driven with a direct mechanical driving shaft that takes over the electrical motor <NUM> when the engine <NUM> is started using the sprag clutch <NUM> to engage and disengaged the driving shaft.

In a particular embodiment, having the ability to warm up or cool down components, such as the gearbox <NUM>, the engine inlet <NUM>, and the engine <NUM> itself while said engine <NUM> is powered off might allow the reduction of the cool down time after shutting down the engine <NUM>, which might allow for fuel savings. It might allow to decrease a time to warm up the engine <NUM> before it is started. It might decrease thermal stress and the wear of mechanical components of the engine (e.g., gears, bearings, etc) when starting the engine <NUM>. It might reduce a drag and improve lubrication of components of the engine during the warming up. This system <NUM> may be a single system to warm up and/or cool down the different engine systems such as the gearbox, the housing of the engine <NUM> and so on.

Claim 1:
An engine assembly (<NUM>) for an aircraft, the engine assembly (<NUM>) comprising a combustion engine (<NUM>; <NUM>) including a coolant circuit (<NUM>) in heat exchange relationship with a heat sink (<NUM>), the heat sink (<NUM>) including a heat exchanger (<NUM>) and at least one further component of the engine assembly (<NUM>), the at least one further component (<NUM>) having a main function that differs from thermal exchange, wherein the coolant circuit (<NUM>) comprises a conduit (116a) in heat exchange relationship with the at least one further component (<NUM>), characterised in that:
the conduit (116a) is wrapped around the at least one further component (<NUM>); and
the conduit (116a) is selectively connectable to a remainder of the coolant circuit (<NUM>) via a valve (<NUM>) located on the coolant circuit (<NUM>), the valve (<NUM>) having a first mode in which the valve allows the liquid coolant to circulate within the conduit (116a) and a second mode in which the valve prevents the liquid coolant to flow within the conduit (116a), the valve (<NUM>) configured to selectively use the at least one further component (<NUM>) to help the heat exchanger (<NUM>) in dissipating the heat generated by the combustion engine (<NUM>, <NUM>) when needed.