Patent Description:
Operating rotary engines burning gasoline may present challenges under lean conditions since spark ignition typically requires a homogeneous mixture of fuel and air near stoichiometric conditions in order to have sufficient combustion stability. Typically, the fuel and air are premixed before being injected into the combustion chambers. Some rotary engines may use heavy fuel. However, these heavy fuels may be less environmentally friendly. Improvements are therefore sought. An example of a dual fuel rotary engine is shown in <CIT>.

In one aspect of the present invention, there is provided a rotary engine, comprising: an outer body defining a rotor cavity; a rotor rotatable within the rotor cavity and in sealing engagement with walls of the outer body and defining at least one chamber of variable volume in the rotor cavity; a pilot subchamber defined by the outer body, the pilot subchamber having an outlet in fluid flow communication with the rotor cavity; a main fuel source of a heavy fuel; an alternative fuel source of an alternative fuel different from the heavy fuel; a main injector having a tip in fluid communication with the rotor cavity at a location spaced apart from the outlet of the pilot subchamber, the main injector selectively fluidly connectable to the main fuel source or to the alternative fuel source; and a controller having a processing unit and a computer-readable medium having instructions stored thereon executable by the processing unit to cause the processing unit to: determine that the rotary engine is in a vicinity of a city or an airport; and upon determining that the rotary engine is in the vicinity of the city or the airport, operate the main injector in a first configuration in which the main injector fluidly connects the alternative fuel source to the rotor cavity while disconnecting the main fuel source from the rotor cavity.

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

An inner body or rotor <NUM> is received within the internal cavity <NUM>, with the geometrical axis of the rotor <NUM> being offset from and parallel to the axis of the outer body <NUM>. The rotor <NUM> has axially spaced end faces <NUM> adjacent to the side housings <NUM>, and a peripheral face <NUM> extending therebetween. The peripheral face <NUM> defines three circumferentially-spaced apex portions <NUM> (only one of which is shown), and a generally triangular profile with outwardly arched sides. The apex portions <NUM> are in sealing engagement with the inner surface <NUM> of the rotor housing <NUM> to form three rotating working chambers <NUM> (only two of which are partially shown on <FIG>) between the rotor <NUM> and outer body <NUM>. A recess <NUM> may be defined in the peripheral face <NUM> of the rotor <NUM> between each pair of adjacent apex portions <NUM>, to form part of the corresponding chamber <NUM>. In some embodiments, the recess <NUM> may be omitted.

The working chambers <NUM> are sealed. Each rotor apex portion <NUM> has an apex seal <NUM> extending from one end face <NUM> to the other and protruding radially from the peripheral face <NUM>. Each apex seal <NUM> is biased radially outwardly against the inner surface <NUM> of the rotor housing <NUM> through a respective spring. An end seal <NUM> engages each end of each apex seal <NUM>, and is biased against the respective side housing <NUM> through a suitable spring. 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. A spring urges each face seal <NUM> axially outwardly so that the face seal <NUM> projects axially away from the adjacent rotor end face <NUM> into sealing engagement with the adjacent side housing <NUM> of the internal cavity <NUM>. Each face seal <NUM> is in sealing engagement with the end seal <NUM> adjacent each end thereof.

Although not shown in <FIG>, the rotor <NUM> is journaled on an eccentric portion of a shaft and includes a phasing gear co-axial with the rotor axis, which is meshed with a fixed stator phasing gear secured to the outer body co-axially with the shaft. The rotor <NUM> rotates the shaft and the meshed gears guide the rotor <NUM> to perform orbital revolutions within the internal cavity <NUM>. The shaft performs three rotations for each orbital revolution of the rotor <NUM> in the internal cavity <NUM>. Oil seals are provided around the phasing gear to prevent leakage flow of lubricating oil radially outwardly thereof between the respective rotor end face <NUM> and outer body side housing <NUM>.

At least one inlet port (not shown in <FIG>) is defined through one of the side housings <NUM> or the rotor housing <NUM> for admitting air (atmospheric or compressed via a compressor) into one of the working chambers <NUM>, and at least one exhaust port (not shown in <FIG>) is defined through one of the side housings <NUM> or the rotor housing <NUM> for discharge of the exhaust gases from the working chambers <NUM>. The inlet and exhaust ports are positioned relative to each other and relative to the ignitor and fuel injectors (further described below) such that during each revolution of the rotor <NUM>, each chamber <NUM> moves around the internal cavity <NUM> with a variable volume 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.

In a particular embodiment, these ports are arranged such that the rotary engine <NUM> operates under the principle of the Miller or Atkinson cycle, with its volumetric compression ratio lower than its volumetric expansion ratio. In another embodiment, the ports are arranged such that the volumetric compression and expansion ratios are equal or similar to one another.

Still referring to <FIG>, a pilot cavity is defined in the outer body <NUM>, for pilot fuel injection and ignition. In the embodiment shown example, the pilot cavity is in the form of a pilot subchamber <NUM>, provided in an insert <NUM> received in a corresponding insert opening defined through the rotor housing <NUM> of the outer body <NUM> and in communication with the internal cavity <NUM>, for pilot fuel injection and ignition. The pilot subchamber <NUM> is thus located radially outwardly of the inner surface <NUM> of the rotor housing <NUM>. In a particular embodiment, the insert <NUM> is made of a material having a greater heat resistance than that of the rotor housing <NUM>, which may be made for example of aluminium. For example, the insert <NUM> may be made of an appropriate type of ceramic or of an appropriate type of super alloy such as a Nickel based super alloy. Other configurations are also possible, including configurations where the pilot cavity (e.g. pilot subchamber <NUM>) is defined directly in the outer body <NUM>, for example in the rotor housing <NUM>.

The pilot subchamber <NUM> is in communication with the internal cavity <NUM>. In the embodiment shown, the pilot subchamber <NUM> has a circular cross-section; alternate shapes are also possible. The pilot subchamber <NUM> communicates with the internal cavity <NUM> through at least one opening or outlet <NUM>, and has a shape forming a reduced cross-section adjacent the opening outlet <NUM>, such that the outlet <NUM> defines a restriction to the flow between the pilot subchamber <NUM> and the internal cavity <NUM>. The outlet <NUM> may have various shapes and/or be defined by multiple holes.

The insert <NUM> and/or rotor housing <NUM> have an ignitor elongated hole <NUM> defined therein, also in communication with the pilot subchamber <NUM>. An ignitor <NUM> or ignition element is received and retained within the corresponding hole, with the tip of the ignitor <NUM> communicating with the pilot subchamber <NUM>, for example by having the ignitor <NUM> extending outside of the pilot subchamber <NUM> and the ignitor elongated hole communicating with the pilot subchamber <NUM> through an opening or passage <NUM> aligned with the ignitor tip. In the embodiment shown, the ignitor <NUM> is a glow plug. Alternate types of ignitors <NUM> which may be used include, but are not limited to, plasma ignition, laser ignition, spark plug, microwave, etc..

A volume of the pilot subchamber <NUM> may range from <NUM>% to <NUM>% of a total engine volume as described in <CIT>.

The rotor housing <NUM> has a pilot injector elongated hole <NUM> defined therethrough in proximity of the pilot subchamber <NUM>, and in communication with the pilot subchamber <NUM>. A pilot fuel injector, referred to below as a pilot injector <NUM>, is received and retained within the corresponding hole <NUM>, with the tip <NUM> of the pilot injector <NUM> in communication with the pilot subchamber <NUM>.

The rotor housing <NUM> also has a main injector elongated hole <NUM> defined therethrough, in communication with the internal cavity <NUM> and spaced apart from the pilot cavity and pilot injector <NUM>. A main fuel injector, referred to below as a main injector <NUM>, is received and retained within this corresponding hole <NUM>, with the tip <NUM> of the main injector <NUM> communicating with the internal cavity <NUM> at a point spaced apart from the communication between the outlet <NUM> of the pilot subchamber <NUM> and internal cavity <NUM>. The main injector <NUM> is located rearward of the outlet <NUM> with respect to the direction R of the rotor rotation and revolution, i.e. upstream from the outlet <NUM> between the pilot subchamber <NUM> and working chambers <NUM>, and is angled to direct fuel forwardly into each of the rotating chambers <NUM> sequentially with a tip hole configuration designed for an adequate spray.

The pilot injector <NUM> and main injector <NUM> inject fuel, which in a particular embodiment is heavy fuel e.g. diesel, kerosene (jet fuel), equivalent biofuel, etc. into the chambers <NUM>. Alternatively, the fuel may be any other adequate type of fuel suitable for injection as described, including non-heavy fuel such as for example gasoline or liquid hydrogen fuel. In a particular embodiment, the pilot injector <NUM> and main injector <NUM> deliver the same type of fuel, for example from a common fuel source; alternately, the pilot injector <NUM> and main injector <NUM> may deliver different type of fuel.

The pilot subchamber <NUM> may help create a stable and powerful ignition zone to ignite the overall lean working chamber <NUM> to create the stratified charge combustion. The pilot subchamber <NUM> may improve combustion stability, particularly but not exclusively for a rotary engine which operates with heavy fuel below the self-ignition of fuel. The insert <NUM> made of a heat resistant material may advantageously create a hot wall around the pilot subchamber <NUM> which may further help with ignition stability.

In a particular embodiment, the rotary engine <NUM> is operated in accordance with the following. A pilot quantity of fuel is delivered into the pilot subchamber <NUM> and ignited within the pilot subchamber <NUM>, and a main quantity of fuel is delivered into the working chambers <NUM> downstream of their communication with the pilot subchamber <NUM>. When the rotary engine <NUM> operates at maximum load, both the pilot quantity and the main quantity may correspond to a maximum pilot and main injection fuel flow, respectively. However, when the rotary engine <NUM> operates at part load, some of the pilot and/or main injections are reduced or skipped, so as to reduce the fuel consumption, noise and/or vibrations on the rotary engine <NUM>. Accordingly, one or both of the pilot and main quantity is varied between successive rotations of the shaft, i.e. between successive working chambers <NUM> (since the shaft performs three rotations for each complete revolution of the rotor <NUM>, each shaft rotation corresponds to fuel injection in one of the working chambers <NUM>). For example, the pilot and/or main injection quantity may be zero (skipped injection) for at least one of the successive rotations of the shaft, and greater than zero (e.g., maximum value) for at least another one of the successive rotations of the shaft.

Various injection patterns may be used to vary the quantity of fuel injected by the pilot and/or main injector(s) <NUM>, <NUM> between the successive rotations of the shaft. In a particular embodiment, the injection pattern is repeated for each set of first, second and third successive rotations of the shaft, and accordingly each of the three working chambers <NUM> has its particular injection conditions. For example, for the first shaft rotation (first working chamber <NUM>), the main quantity is zero and the pilot quantity is greater than zero, i.e. the main injection is skipped while a pilot injection is performed; for the second rotation (second working chamber <NUM>), the main and pilot quantities are both zero, i.e. both the main and pilot injections are skipped; and for the third rotation (third working chamber <NUM>), the main and pilot quantities are both greater than zero, i.e. a pilot and main injections are both performed.

In the present embodiment, a distance between the tip of fuel injector <NUM> and the pilot subchamber <NUM> is less than a distance between two adjacent apexes <NUM> of the rotor <NUM>. This may ensure that both of the tip of the main injector <NUM> and the outlet <NUM> of the pilot subchamber <NUM> are simultaneously in fluid flow communication with a common one of the combustion chambers <NUM>. More specifically, the fuel injected in the pilot subchamber <NUM> may be used to ignite the fuel injected into the combustion chamber <NUM>. Thus, upon ignition of the fuel in the pilot subchamber <NUM>, the ignited fuel flows out of the pilot subchamber <NUM> via the outlet <NUM> to reach the combustion chamber <NUM> thereby igniting the fuel received therein. This configuration may allow the use of two different types of fuel each having their respective advantages.

Still referring to <FIG>, the pilot injector <NUM> and the main injector <NUM> may both be fluidly connected to a main fuel source S1 and an alternative fuel source S2 and may both be operable to inject a selected one of a main fuel from the main fuel source S1 and an alternative fuel from the alternative fuel source S2. The pilot injector <NUM> and the main injector <NUM> are operatively connected to a controller <NUM> operable to determine which of the main fuel and the alternative fuel to use. More detail about this are presented below. The pilot injector <NUM> and the main injector <NUM> may be each be fluidly connected to both of the main fuel source S1 and the alternative fuel source S2. The pilot injector <NUM> has a first configuration in which the pilot injector <NUM> fluidly connects the main fuel source S1 to the pilot subchamber <NUM> while fluidly disconnecting the alternative fuel source S2 from the pilot subchamber <NUM>. The pilot injector <NUM> has a second configuration in which the pilot injector <NUM> fluidly connects the alternative fuel source S2 to the pilot subchamber <NUM> while fluidly disconnecting the main fuel source S1 from the pilot subchamber <NUM>. The main injector <NUM> has a first configuration in which the main injector <NUM> fluidly connects the main fuel source S1 to the combustion chamber <NUM> while fluidly disconnecting the alternative fuel source S2 from the combustion chamber <NUM>. The main injector <NUM> has a second configuration in which the main injector <NUM> fluidly connects the alternative fuel source S2 to the combustion chamber <NUM> while fluidly disconnecting the main fuel source S1 from the combustion chamber <NUM>. As aforementioned, outlet(s) defined by a tip of the pilot injector <NUM> is(are) in fluid communication with the combustion chamber <NUM> through the pilot subchamber <NUM>, and outlet(s) defined by a tip of the main injector <NUM> is(are) in fluid communication with the combustion chamber <NUM> independently of the pilot subchamber <NUM>. In other words, the main injector <NUM> injects fuel into the combustion chamber <NUM> while bypassing the pilot subchamber <NUM>.

In some embodiments, the injectors <NUM>, <NUM> each have two inlets and two outlets for injecting two different fuels. Such an exemplary injector is described below with reference to <FIG>. Alternatively, the injectors <NUM>, <NUM> may have a single outlet and two distinct inlets. The injector may thus be operatable to selectively fluidly connect either one of the two distinct inlets to the single outlet. In other words, in some engine configurations, the injector may not need to distinct outlets.

Referring now to <FIG>, a rotary engine in accordance with another embodiment is shown at <NUM>. For the sake of conciseness, only features differing from the rotary engine <NUM> described above with reference to <FIG> are described below.

In the embodiment shown, the main injector <NUM> of the rotary engine <NUM> is spaced further away from the outlet <NUM> of the pilot subchamber <NUM>. The outer body <NUM> of the rotary engine <NUM> defines an intake 110A and an exhaust 110B. The intake 110A is located downstream of the exhaust 110B relative to the direction of rotation R of the rotor <NUM>. The intake 110A is in fluid communication with an air source, such as ambient air, or a compressor, for injecting air into the combustion chamber <NUM>. The exhaust 110B is used for expelling combustion gases out of the combustion chamber <NUM>. In some embodiments, the exhaust 110B is fluidly connected to a turbine that extract energy from the combustion gases. The turbine may drive a shaft that may be drivingly engaged to the shaft of the rotary engine <NUM> to compound power therewith.

A distance, about a circumference of the rotor housing <NUM>, between the outlet <NUM> of the pilot subchamber <NUM> and the tip of the main injector <NUM> may be greater than a distance between adjacent apexes of the rotor <NUM>. Put differently, the main injector <NUM> may be located closer to the intake 110A than the pilot subchamber <NUM>. This may allow the injection of fuel into the combustion chamber <NUM> before a volume of the combustion chamber <NUM> starts to decrease for compressing the air. This may allow a better mixing of the fuel with the air before ignition. This may change the combustion mode from a diffusion type flame to a premixed flame. In other words, the rotary engine <NUM> may use an indirect injection rather than a direction injection as for the rotary engine <NUM> of <FIG>. This configuration may allow more time for mixing the fuel with an oxidizer (e.g., oxygen). In an indirect injection, the fuel is mixed with air prior to being injected in to the combustion chamber. Therefore, a mixture of air and fuel is injected in the combustion chamber via the intake 110A (<FIG>). Hence, the main injector <NUM> may have its tip in fluid communication with a conduit that has an outlet fluidly connected to the intake 110A.

Referring now to <FIG>, a rotary engine in accordance with another embodiment is shown at <NUM>. For the sake of conciseness, only features differing from the rotary engine <NUM> of <FIG> are described below.

In the embodiment shown, the main injector <NUM> is a single injector. The rotary engine <NUM> is thus devoid of the pilot injector <NUM>. In other words, the fuel received into the pilot subchamber <NUM> is provided by the main injector <NUM>. The main injector <NUM> is fluidly connected to both of the main fuel source S1 and the alternative fuel source S2.

The outer body <NUM> of the rotary engine <NUM> defines a passage <NUM> therein. The passage <NUM> is located radially outwardly of the inner surface <NUM> of the rotor housing <NUM>. The passage <NUM> may be sub-divided into a plurality of sub-passages. The passage <NUM> fluidly connects the main injector elongated hole <NUM> to the pilot subchamber <NUM>. The passage <NUM> has a passage inlet 39A in fluid flow communication with one of outlets of the main injector <NUM> and a passage outlet 39B in fluid communication with the pilot subchamber <NUM>. The passage outlet 39B opens to the pilot subchamber <NUM>. As shown in <FIG>, the passage outlet 39B opens to the pilot subchamber <NUM> at a location spaced apart from the outlet <NUM> of the pilot subchamber <NUM> via which the fuel injected in the pilot subchamber <NUM> reaches the combustion chambers <NUM>. In other words, the passage <NUM> is separated from the internal cavity <NUM> of the rotary engine <NUM>. By being "separated", it is implied that the passage <NUM> is free of intersection with the internal cavity <NUM> or combustion chamber <NUM> of the rotary engine <NUM>. The passage <NUM> therefore provides a fluid communication from the one of the outlets of the main injector <NUM> to the pilot subchamber <NUM> without passing by the internal cavity <NUM>.

Referring now to <FIG>, an injector <NUM>, which may correspond to any of the pilot injector <NUM> or the main injector <NUM> of <FIG>, is shown. Both of the pilot and main injectors may be a dual-needle injector as shown in <FIG>. The injector <NUM> is referred to as a dual-needle injector. The injector <NUM> has a main body <NUM> enclosing a needle assembly comprising an inner needle <NUM> and an outer needle <NUM>. The outer needle <NUM> is hollow and the inner needle <NUM> is received within the outer needle <NUM>. One or more actuator(s) <NUM> are engaged to the inner needle <NUM> and the outer needle <NUM> to control their axial motion relative to a central axis A1 and relative to the main body <NUM>. The one or more actuator(s) <NUM> may be electronically controlled and operatively connected to a controller <NUM>. The one or more actuator(s) <NUM> may be solenoid, fuel-draulic actuators, hydraulic actuators, pneumatic actuators and so on. The injector <NUM> has a tip defined by the outer needle <NUM>. The outer needle <NUM> defines a first outlet <NUM> of the injector <NUM> whereas the main body <NUM> defines a second outlet <NUM> of the injector <NUM>. The first outlet <NUM> and the second outlet <NUM> are spaced apart from one another and may output fuel at different directions. In the present embodiment, the second outlet <NUM> injects fuel in a direction having a radial component relative to the central axis A1 if the injector <NUM>. The first outlet <NUM> is defined by one or more aperture(s) and the second outlet <NUM> is defined by one or more aperture(s). It will be appreciated that any injector able to inject two different fuels via two different outlets may be used without departing from the scope of the present disclosure.

The first outlet <NUM> and the second outlet <NUM> are separated and distinct from one another. Put differently, fuel may be injected via the first outlet <NUM> while the second outlet <NUM> remains closed. Similarly, fuel may be injected via the second outlet <NUM> while the first outlet <NUM> remains closed. In some cases, fuel may be injected simultaneously by both of the first outlet <NUM> and the second outlet <NUM>. The fuel(s) flow through the injector <NUM> along respective flow paths that remain independent until they are outputted via the first outlet <NUM> and the second outlet <NUM>. Herein, the expression "independent" implies that the fuels are not mixed within the injector <NUM>. The fuels remain isolated and separated from one another.

The fuel injector <NUM> has a first inlet <NUM> fluidly connected to the first outlet <NUM> and a second inlet <NUM> fluidly connected to the second outlet <NUM>. The injector <NUM> may have a first configuration in which the first inlet <NUM> is fluidly connected to the first outlet <NUM> while the second inlet <NUM> is fluidly disconnected from the second outlet <NUM>; a second configuration in which the first inlet <NUM> is fluidly disconnected from the first outlet <NUM> and in which the second inlet <NUM> is fluidly connected to the second outlet <NUM>, a third configuration in which the first inlet <NUM> is fluidly connected to the first outlet <NUM> and in which the second inlet <NUM> is fluidly connected to the second outlet <NUM>, and a fourth configuration in which both of the first inlet <NUM> and the second inlet <NUM> are fluidly disconnected from their respective first outlet <NUM> and the second outlet <NUM>.

Referring to <FIG>, in the embodiment shown, the first outlet <NUM> may be aligned with a port defined through the outer body <NUM> (e.g., rotor housing <NUM>) for injecting fuel directly into the combustion chambers <NUM> while bypassing the pilot subchamber <NUM>. The second outlet <NUM> may be aligned with the passage <NUM> defined by the outer body <NUM>. The rotary engine <NUM> therefore defines two parallel flow paths from the injector <NUM> to the internal cavity <NUM>. A first flow path extends from the first outlet <NUM> of the injector <NUM> directly to the internal cavity <NUM> while bypassing the pilot subchamber <NUM>. A second flow path extends from the second outlet <NUM> of the injector <NUM> to the internal cavity <NUM> through the pilot subchamber <NUM>.

Typically, heavy fuels are used. However, environmental concerns may require a reduction of these heavy fuels. The rotary engine <NUM> of the present disclosure may therefore use an alternative "greener" fuel, such as gasoline, hydrogen, liquefied natural gas, ammonia, sustainable fuel for aviation (SAF), and so on in conjunction with a heavy fuel, such as diesel, jet fuel, and so on. The SAF may include fuels derived from food waste (e.g., non-fossil fuels). In other words, the fuel injector <NUM> receives a main fuel from the main fuel source S1 and an alternative fuel from the alternative fuel source S2. The alternative fuel may be injected directly into the combustion chamber <NUM> via the first outlet <NUM> while bypassing the pilot subchamber <NUM> and the main fuel may be injected into the pilot subchamber <NUM> via the first outlet <NUM>. Although the alternatives fuels may be less polluting, they are less suited for auto-ignition. Herein, the expression "auto-ignition" means that a fuel is able to self-ignite, by one or more of temperature and pressure, without requiring an external input of energy, such as via an igniter. The heavy fuels are typically able to auto-ignite. Consequently, the main fuel may have a first energy requirement to ignite that is less than a second energy requirement to ignite of the alternative fuel. The main fuel may have a first cetane number greater than a second cetane number of the alternative fuel. The alternative fuel may be gasoline, hydrogen, liquefied natural gas, ammonia and so on while the main fuel may be a heavy fuel, such as diesel, jet fuel, and so on.

Still referring to <FIG>, the controller <NUM> is operable to cause the injector <NUM> to inject the alternative fuel in the at least one chamber <NUM> via one of the outlets of the injector <NUM>; and to ignite the alternative fuel received in the at least one chamber <NUM> by injecting the main fuel into the pilot subchamber <NUM> via the other of the outlets of the injector <NUM>. In the present embodiment, the controller <NUM> causes the injection of the main fuel into the pilot subchamber <NUM> before a volume of the at least one chamber <NUM> reaches a minimum volume. This is such that the main fuel is subjected to a compressive force as the rotor <NUM> rotates to decrease the volume of the combustion chamber <NUM>, which in this case encompasses the volume of the pilot subchamber <NUM>, to the minimal volume to cause auto-ignition of the main fuel. The ignited main fuel will then exit the pilot subchamber <NUM> via the outlet <NUM> of the pilot subchamber <NUM> to reach the combustion chamber <NUM> thereby igniting the alternative fuel received therein. Ignition of the alternative fuel may thus rely on the auto-ignition of the main fuel. In some cases, an igniter may be provided to ignite the main fuel. The engines <NUM>, <NUM>, <NUM> may be devoid of an igniter having a tip directly exposed to the rotor cavity <NUM> independently of the pilot subchamber <NUM>.

Referring to <FIG>, the controller <NUM> is operatively connected to the injector(s) to inject a selected one of the main fuel from the main fuel source S1 and the alternative fuel from the alternative fuel source S2. The controller <NUM> is therefore configured to determine that the rotary engine <NUM>, <NUM>, <NUM> is in a vicinity of a city or an airport; and upon determining that the rotary engine is in the vicinity of the city or the airport, operate the main injector <NUM> in a first configuration in which the main injector <NUM> fluidly connects the alternative fuel source S2 to the rotor cavity while disconnecting the main fuel source S1 from the rotor cavity. In this embodiment, the main fuel of the main fuel source S1 is a heavy fuel, such as diesel or jet fuel and the alternative fuel of the alternative fuel source S2 may be a more environmentally friendly fuel such as, for instance, gasoline, ammonia, liquefied natural gas, and so on. Therefore, the controller <NUM> may determine that the rotary engine <NUM>, <NUM>, <NUM>, or an aircraft equipped with said engine, is proximate a city or an airport and that pollution is to be reduced proximate these locations.

Herein, the expression "vicinity" implies that one or more of a ground distance between the aircraft or rotary engine is below from about <NUM> to about <NUM> kilometers and an altitude of the aircraft is below about <NUM> feet. Herein, the expression "about" implies variations of plus or minus <NUM>%.

The controller <NUM> may further determine that the rotary engine <NUM>, <NUM>, <NUM> is outside the vicinity of a city or an airport; and upon determining that the rotary engine is outside the vicinity of the city or the airport, operate the main injector <NUM> in a second configuration in which the main injector <NUM> fluidly connects the main fuel source S1 to the rotor cavity while disconnecting the alternative fuel source S2 from the rotor cavity. Thus, when the rotary engine or aircraft is further away from these locations, the heavy fuel, which may be less environmentally friendly, but which may provide a more efficient combustion, may be used instead.

In the embodiments of <FIG> and <FIG>, the pilot injector <NUM> may also be used to inject a selected one of the main fuel and the alternative fuel. The controller <NUM> may determine that a temperature of the rotary engine; operate the pilot injector in a first configuration in which the pilot injector <NUM> fluidly connects the main fuel source S1 to the pilot subchamber <NUM> while disconnecting the alternative fuel source S2 from the pilot subchamber <NUM> when the temperature is below a temperature threshold; and operate the pilot injector <NUM> in a second configuration in which the pilot injector <NUM> fluidly connects the alternative fuel source S2 to the pilot subchamber <NUM> while disconnecting the main fuel source S1 from the pilot subchamber <NUM> when the temperature is above the temperature threshold.

In fact, when the rotary engine is cold, that is, when its temperature is below the temperature threshold, conditions in the pilot subchamber <NUM> may be less suitable for ignition. In such cases, the heavy fuel, which is more suitable for auto-ignition, may be used. Once the rotary engine has warmed up and its temperature is above the temperature threshold, the second or alternative fuel may be used instead.

The controller <NUM> may determine that the rotary engine or aircraft is proximate the city or airport by determining that an altitude of the rotary engine or aircraft is below an altitude threshold, by determining that GPS coordinates of the rotary engine that indicate that a distance between the rotary engine or aircraft and the city or the airport is below a distance threshold, and/or by determining that a flight phase of the rotary engine corresponds to taxi, takeoff, climb, approach, or landing. Sensors, such as a temperature sensor, a pressure sensor, a speed sensor may be used to determine the flight phase. For instance, if the ambient temperature is below an ambient temperature threshold, this may imply that the aircraft is flying at a high altitude. The pressure sensor may determine the ambient pressure. If this ambient pressure is below an ambient pressure sensor, this may imply that the aircraft is flying at a high altitude. The speed sensor may determine a travel speed of the aircraft. If this travel speed is above a speed threshold, this may imply that the aircraft is flying at a high altitude during a cruise phase.

Referring now to <FIG>, a method of supplying fuel to the rotary engine <NUM> of <FIG> is shown at <NUM>. The method <NUM> includes injecting a first fuel from a first outlet of the fuel injector <NUM> into the rotor cavity <NUM> while bypassing the pilot subchamber <NUM> at <NUM>; and injecting a second fuel from a second outlet of the fuel injector <NUM> into the rotor cavity <NUM> through the pilot subchamber <NUM>. In the embodiment shown, the injecting of the second fuel at <NUM> includes injecting the second fuel into the pilot subchamber <NUM> via the passage <NUM> defined by the outer body <NUM>. The injecting of the first fuel at <NUM> may include injecting the first fuel into two or more injection sequences. For instance, a first portion of the first fuel may be injected at a first position of the rotor. Then, no first fuel is injected as the rotor moves from the first position to a second position. A second portion of the first fuel may be injected while the rotor moves away from the second position. These injection sequences may be used to inject the fuel into the same combustion chamber at distinct intervals to create a stratification of the mixture of air and fuel in said combustion chamber. The same may apply to the injecting of the second fuel at <NUM>.

The injecting of the first fuel at <NUM> and the injecting of the second fuel at <NUM> includes injecting the second fuel being different from the first fuel. The injecting of the first fuel and the injecting of the second fuel may include injecting the first fuel having a first energy requirement to ignite being greater than a second energy requirement of the second fuel. The injecting of the first fuel and the injecting of the second fuel may include injecting the first fuel having a first cetane number being less than a second cetane number of the second fuel. The injecting of the first fuel and the injecting of the second fuel may include injecting gasoline as the first fuel and injecting a heavy fuel as the second fuel. The injecting of the first fuel and the injecting of the second fuel includes injecting hydrogen as the first fuel and injecting a heavy fuel as the second fuel.

In the embodiment illustrated, the injecting of the second fuel from the second outlet of the fuel injector <NUM> at <NUM> includes injecting the second fuel before a volume of at least one chamber <NUM> reaches a minimum volume, and auto-igniting the second fuel by compressing the second fuel with the rotor <NUM>.

Referring now to <FIG>, a method of supplying fuel to the rotary engines <NUM>, <NUM>, <NUM> of <FIG> is shown at <NUM>. The method <NUM> includes determining a position of the rotary engine <NUM>, <NUM>, <NUM> relative to a city or an airport at <NUM>; injecting a heavy fuel in the rotor cavity <NUM> via a fuel injector when the position of the rotary engine is outside a vicinity of the city or the airport at <NUM>; and injecting an alternative fuel different than the heavy fuel in the rotor cavity via the fuel injector when the position of the rotary engine is in the vicinity of the city or the airport at <NUM>.

The method <NUM> may include determining a temperature of the rotary engine; and injecting the heavy fuel in the pilot subchamber <NUM> via the pilot injector <NUM> when the temperature is below a temperature threshold. The method may further include injecting the alternative fuel in the pilot subchamber <NUM> via the pilot injector <NUM> when the temperature is above the temperature threshold.

In the embodiment shown, the determining of the position of the rotary engine includes determining one or more of an altitude of the rotary engine being below an altitude threshold, GPS coordinates of the rotary engine indicative that a distance between the rotary engine and the city or the airport is below a distance threshold, and a flight phase of the rotary engine corresponding to taxi, takeoff, climb, approach, or landing.

As mentioned above, a first energy requirement to ignite the alterative fuel may be greater than a second energy requirement to ignite the main fuel. The alternative fuel may have a first cetane number being less than a second cetane number of the main fuel. The alternative fuel may gasoline, hydrogen, liquefied natural gas, ammonia, and the heavy fuel may be diesel or jet fuel.

In the embodiment of <FIG>, the method includes injecting the alternative fuel or the main fuel in the pilot subchamber <NUM> with the pilot fuel injector <NUM> via the passage <NUM> defined by the outer body <NUM>.

With reference to <FIG>, an example of a computing device <NUM> is illustrated. For simplicity only one computing device <NUM> is shown but the system may include more computing devices <NUM> operable to exchange data. The computing devices <NUM> may be the same or different types of devices. The controller <NUM> may be implemented with one or more computing devices <NUM>. Note that the controller <NUM> can be implemented as part of a full-authority digital engine controls (FADEC) or other similar device, including electronic engine control (EEC), engine control unit (ECU), electronic propeller control, propeller control unit, and the like. In some embodiments, the controller <NUM> is implemented as a Flight Data Acquisition Storage and Transmission system, such as a FAST™ system. The controller <NUM> may be implemented in part in the FAST™ system and in part in the EEC. Other embodiments may also apply.

The processing unit <NUM> may comprise any suitable devices configured to implement the method described herein such that instructions <NUM>, when executed by the computing device <NUM> or other programmable apparatus, may cause the functions/acts/steps performed as part of the methods as described herein to be executed.

The methods and systems for supplying fuel described herein may be implemented in a high level procedural or object oriented programming or scripting language, or a combination thereof, to communicate with or assist in the operation of a computer system, for example the computing device <NUM>. Alternatively, the methods and systems for supplying fuel may be implemented in assembly or machine language. The language may be a compiled or interpreted language. Program code for implementing the methods and systems for supplying fuel may be stored on a storage media or a device, for example a ROM, a magnetic disk, an optical disc, a flash drive, or any other suitable storage media or device. The program code may be readable by a general or special-purpose programmable computer for configuring and operating the computer when the storage media or device is read by the computer to perform the procedures described herein. Embodiments of the methods and systems for supplying fuel may also be considered to be implemented by way of a non-transitory computer-readable storage medium having a computer program stored thereon. The computer program may comprise computer-readable instructions which cause a computer, or more specifically the processing unit <NUM> of the computing device <NUM>, to operate in a specific and predefined manner to perform the functions described herein, for example those described in the method <NUM>.

It is noted that various connections are set forth between elements in the preceding description and in the drawings. It is noted that these connections are general and, unless specified otherwise, may be direct or indirect and that this specification is not intended to be limiting in this respect. A coupling between two or more entities may refer to a direct connection or an indirect connection. An indirect connection may incorporate one or more intervening entities. The term "connected" or "coupled to" may therefore include both direct coupling (in which two elements that are coupled to each other contact each other) and indirect coupling (in which at least one additional element is located between the two elements).

It is further noted that various method or process steps for embodiments of the present disclosure are described in the following description and drawings. The description may present the method and/or process steps as a particular sequence. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited to the particular sequence of steps described. As one of ordinary skill in the art would appreciate, other sequences of steps may be possible. Therefore, the particular order of the steps set forth in the description should not be construed as a limitation.

Claim 1:
A rotary engine, comprising:
an outer body (<NUM>) defining a rotor cavity (<NUM>);
a rotor (<NUM>) rotatable within the rotor cavity (<NUM>) and in sealing engagement with walls of the outer body (<NUM>) and defining at least one chamber (<NUM>) of variable volume in the rotor cavity (<NUM>);
a pilot subchamber (<NUM>) defined by the outer body (<NUM>), the pilot subchamber (<NUM>) having an outlet (<NUM>) in fluid flow communication with the rotor cavity (<NUM>);
a main fuel source (S1) of a heavy fuel;
an alternative fuel source (S2) of an alternative fuel different from the heavy fuel;
a main injector (<NUM>) having a tip in fluid communication with the rotor cavity (<NUM>) at a location spaced apart from the outlet (<NUM>) of the pilot subchamber (<NUM>), the main injector (<NUM>) selectively fluidly connectable to the main fuel source (S1) or to the alternative fuel source (S2); and
a controller (<NUM>) having a processing unit (<NUM>) and a computer-readable medium having instructions stored thereon executable by the processing unit (<NUM>) to cause the processing unit (<NUM>) to:
determine that the rotary engine (<NUM>, <NUM>, <NUM>) is in a vicinity of a city or an airport; and
upon determining that the rotary engine (<NUM>, <NUM>, <NUM>) is in the vicinity of the city or the airport, operate the main injector (<NUM>) in a first configuration in which the main injector (<NUM>) fluidly connects the alternative fuel source (S2) to the rotor cavity (<NUM>) while disconnecting the main fuel source (S1) from the rotor cavity (<NUM>).