Patent Application
20140158084
This patent disclosure relates generally to internal combustion engines and, more particularly, to internal combustion engines that are configured to operate on a six-stroke internal combustion cycle.
Internal combustion engines operating on a six-stroke cycle are generally known in the art. In a six-stroke cycle, a piston reciprocally disposed in a cylinder moves through an intake stroke from a top dead center (TDC) position to a bottom dead center (BDC) position to admit air or an air mixture that includes fuel and/or recirculated exhaust gas into the cylinder. During a compression stroke, the piston moves towards the TDC position to compress the air mixture. During this process, an initial or additional fuel charge may be introduced to the cylinder by an injector. Ignition of the compressed mixture increases the pressure in the cylinder and forces the piston towards the BDC position during a first power stroke. In accordance with the six-stroke cycle, the piston performs a second compression stroke in which it recompresses the combustion products remaining in the cylinder after the first combustion or power stroke. During this recompression, any exhaust valves associated with the cylinder remain generally closed to assist cylinder recompression. Optionally, a second fuel charge and/or additional air may be introduced into the cylinder during recompression to assist igniting the residual combustion products and produce a second power stroke. Following the second power stroke, the cylinder undergoes an exhaust stroke when the exhaust valve or valves open to permit the substantial evacuation of combustion products from the cylinder. One example of an internal combustion engine configured to operate on a six-stroke engine can be found in U.S. Pat. No. 7,418,928. This disclosure relates to a method of operating an engine that includes compressing part of the combustion gas after a first combustion stroke of the piston as well as an additional combustion stroke during a six-stroke cycle of the engine.
Some possible advantages of the six-stroke cycle over the more common four-stroke cycle can include reduced emissions and improved fuel efficiency. For example, the second combustion event and second power stroke can provide for a more complete combustion of soot and/or fuel that may remain in the cylinder after the first combustion event. Although the six-stroke method provides some advantages, its implementation with other technologies and its compatibility with other technologies has not yet been entirely understood.
In one aspect, the disclosure describes an internal combustion engine system operating on a six-stroke cycle including an engine. The engine includes a combustion chamber including a piston reciprocally disposed in a cylinder to move between a top dead center position and a bottom dead center position. The combustion chamber further includes an exhaust valve adapted to open and close to selectively expel exhaust gasses from the combustion chamber during an exhaust stroke, and a blowdown exhaust valve adapted to open and close to selectively expel blowdown exhaust gasses from the combustion chamber during a recompression stroke. The engine system also includes an intake line communicating with the engine that directs air into the combustion chamber, and an exhaust line communicating with the engine to direct exhaust gasses from combustion chamber when the exhaust valve is open. The engine system includes a blowdown exhaust line communicating with the engine and the intake line that directs blowdown exhaust gasses out of the combustion chamber to the intake line. The blowdown exhaust gasses are expelled through the blowdown exhaust valve during the recompression stroke, and exhaust gasses are expelled through the exhaust valve during the exhaust stroke.
In another aspect, the disclosure describes a method of reducing emissions from an internal combustion engine operating a six-stroke cycle. The method includes introducing air from an intake line into a combustion chamber of the internal combustion engine during an intake stroke, and compressing the air in the combustion chamber during a first compression stroke. The method also includes introducing a first fuel charge into the combustion chamber during the first compression stroke to form a compressed fuel and air mixture, and combusting the compressed fuel and air mixture in the combustion chamber at the completion of the first compression stroke, thereby expanding the fuel and air mixture during a first power stroke and resulting in intermediate combustion products within the combustion chamber. The method includes compressing at least part of the intermediate combustion products within the combustion chamber during a second compression stroke. The method also includes opening a blowdown exhaust valve to expel at least a portion of the intermediate combustion products as blowdown exhaust gasses from the combustion chamber between commencement of the first power stroke and completion of the second compression stroke. The method includes directing at least a portion of the blowdown exhaust gasses through a blowdown exhaust line and into the intake line. The method includes combusting the compressed fuel and air mixture in the combustion chamber at the completion of the second compression stroke, thereby expanding the fuel and air mixture during a second power stroke and resulting in second combustion products within the combustion chamber. The method also includes opening an exhaust valve to expel at least a portion of the second combustion products from the combustion chamber into an exhaust line as exhaust gasses between commencement of the second power stroke and the completion of an exhaust stroke.
In yet another embodiment, the disclosure describes a machine that includes an engine. The engine includes a combustion chamber that includes a piston reciprocally disposed in a cylinder to move between a top dead center position and a bottom dead center position. The combustion chamber further includes an exhaust valve adapted to open and close to selectively expel exhaust gasses from the combustion chamber during an exhaust stroke, and a blowdown exhaust valve adapted to open and close to selectively expel blowdown exhaust gasses from the combustion chamber during a recompression stroke. The engine also includes an intake line communicating with the engine that directs air into the combustion chamber. The engine includes an exhaust line communicating with the engine to direct exhaust gasses from combustion chamber when the exhaust valve is open, and a blowdown exhaust line communicating with the engine and the intake line that directs exhaust gasses out of the combustion chamber to the intake line. The blowdown exhaust gasses are expelled through the blowdown exhaust valve during the recompression stroke, and exhaust gasses are expelled through the exhaust valve during the exhaust stroke.
This disclosure relates generally to an internal combustion engine and, more particularly, to one adapted to perform a six-stroke cycle for reduced emissions and improved efficiencies. Internal combustion engines burn a hydrocarbon-based fuel or another combustible fuel to convert the potential or chemical energy therein to mechanical power. In one embodiment, the disclosed engine may be a compression ignition engine, such as a diesel engine, in which a mixture of air and fuel is compressed in a cylinder to raise the pressure and temperature of the mixture to a point of at which auto-ignition or spontaneous ignition occurs. Compression ignition engines typically lack sparkplugs, which are typically associated with cylinders of gasoline burning engines. In the present disclosure, the utilization of different fuels such as gasoline and different ignition methods, for example, use of diesel as a pilot fuel to ignite gasoline or natural gas, are contemplated and fall within the scope of the disclosure.
Now referring to
To supply the fuel that the engine 102 burns during the combustion process, a fuel system 110 is operatively associated with the engine system 100. The fuel system 110 includes a fuel reservoir 112 that can accommodate a hydrocarbon-based fuel such as liquid diesel fuel. Although only one fuel reservoir is depicted in the illustrated embodiment, it will be appreciated that in other embodiments additional reservoirs may be included that accommodate the same or different types of fuels that may also be burned during the combustion process. Because the fuel reservoir 112 is often situated in a remote location with respect to the engine 102, a fuel line 114 can be disposed through the engine system 100 to direct the fuel from the fuel reservoir to the engine. To pressurize the fuel and force it through the fuel line 114, a fuel pump 116 can be disposed in the fuel line. An optional fuel conditioner 118 may also be disposed in the fuel line 114 to filter the fuel or otherwise condition the fuel by, for example, introducing additives to the fuel, heating the fuel, removing water and the like.
To introduce the fuel to the combustion chambers 106, the fuel line 114 may be in fluid communication with one or more fuel injectors 120 that are associated with the combustion chambers. In the illustrated embodiment, one fuel injector 120 is associated with each combustion chamber but in other embodiments different numbers of injectors might be included. Additionally, while the illustrated embodiment depicts the fuel line 114 terminating at the fuel injectors, the fuel line may establish a fuel loop that continuously circulates fuel through the plurality of injectors and, optionally, delivers unused fuel back to the fuel reservoir 112. The fuel injectors 120 can be electrically actuated devices that selectively introduce a measured or predetermined quantity of fuel to each combustion chamber 106. In other embodiments, introduction methods other than fuel injectors, such as a carburetor or the like, can be utilized.
To supply the air that is combusted with the fuel in the combustion chambers 106, a hollow runner or intake manifold 130 can be formed in or attached to the engine block 104 such that it extends over or proximate to each of the combustion chambers. The intake manifold 130 can communicate with an intake line 132 that directs air to the internal combustion engine 102. Fluid communication between the intake manifold 130 and the combustion chambers 106 can be established by a plurality of intake runners 134 extending from the intake manifold. One or more intake valves 136 can be associated with each combustion chamber 106 and can open and close to selectively introduce the intake air from the intake manifold 130 to the combustion chamber. While the illustrated embodiment depicts the intake valves at the top of the combustion chamber 106, in other embodiments the intake valves may be placed at other locations such as through a sidewall of the combustion chamber. To direct the exhaust gasses produced by combustion of the air/fuel mixture out of the combustion chambers 106, an exhaust manifold 140 communicating with an exhaust line 142 can also be disposed in or proximate to the engine block 104. The exhaust manifold 140 can communicate with the combustion chambers 106 by exhaust runners 144 extending from the exhaust manifold 140. The exhaust manifold 140 can receive exhaust gasses by selective opening and closing of one or more exhaust valves 146 associated with each chamber.
To actuate the intake valves 136 and the exhaust valves 146, the illustrated embodiment depicts an overhead camshaft 148 that is disposed over the engine block 104 and operatively engages the valves, but other valve activation arrangements and structures can be used. As will be familiar to those of skill in the art, the camshaft 148 can include a plurality of eccentric lobes disposed along its length that, as the camshaft rotates, cause the intake and exhaust valves 136, 146 to displace or move up and down in an alternating manner with respect to the combustion chambers 106. The placement or configuration of the lobes along the camshaft 148 controls or determines the gas flow through the internal combustion engine 102. In an embodiment, the camshaft 148 can be configured to selectively control the relative timing and the duration of the valve opening and closing events through a process referred to as variable valve timing. Various arrangements for achieving variable valve timing are known. In one embodiment, contoured lobes formed on the camshaft 148 are manipulated to alter the timing and duration of valve events by moving the camshaft along its axis to expose the valve activators to changing lobe contours. To implement these adjustments in the illustrated embodiment, the camshaft 148 can be associated with a camshaft actuator 149. As is known in the art, other methods exist for implementing variable valve timing such as additional actuators acting on the individual valve stems and the like.
To assist in directing the intake air to and exhaust gasses from the internal combustion engine 102, the engine system 100 can include a turbocharger 150. The turbocharger 150 includes a compressor 152 disposed in the intake line 132 that compresses intake air drawn from the atmosphere and directs the compressed air to the intake manifold 130. Although a single turbocharger 150 is shown, more than one such device connected in series and/or in parallel with another can be used. To power the compressor 152, a turbine 156 can be disposed in the exhaust line 142 and can receive pressurized exhaust gasses from the exhaust manifold 140. The pressurized exhaust gasses directed through the turbine 156 can rotate a turbine wheel having a series of blades thereon, which powers a shaft that causes a compressor wheel to rotate within the compressor housing.
To filter debris from intake air drawn from the atmosphere, an air filter 160 can be disposed upstream of the compressor 152. In some embodiments, the engine system 100 may be open-throttled wherein the compressor 152 draws air directly from the atmosphere with no intervening controls or adjustability. In such systems, engine speed is primarily controlled by the amount of and timing at which fuel is introduced to the combustion chambers. However, in other embodiments, to assist in controlling or governing the amount of air drawn into the engine system 100, an adjustable governor or intake throttle 162 can be disposed in the intake line 132 between the air filter 160 and the compressor 152 to provide a means of controlling the air intake of the engine, but other means, such as by use of variable valve timing, can be used for this purpose. Because the intake air may become heated during compression, an intercooler 166 such as an air-to-air heat exchanger can be disposed in the intake line 132 between the compressor 152 and the intake manifold 130 to cool the compressed air.
To reduce emissions and assist adjusted control over the combustion process, the engine system 100 can mix the intake air with a portion of the exhaust gasses drawn from the exhaust system of the engine through a system or process called exhaust gas recirculation (EGR). The EGR system forms an intake air/exhaust gas mixture that is introduced to the combustion chambers. In one aspect, addition of exhaust gasses to the intake air displaces the relative amount of oxygen in the combustion chamber during combustion that results in a lower combustion temperature and reduces the generation of nitrogen oxides. Two exemplary EGR systems are shown associated with the engine system 100 in
In the first embodiment, a high-pressure EGR system 170 operates to direct high-pressure exhaust gasses to the intake manifold 130. The high-pressure EGR system 170 includes a high-pressure EGR line 172 that communicates with the exhaust line 142 downstream of the exhaust manifold 140 and upstream of the turbine 156 to receive the high-pressure exhaust gasses being expelled from the combustion chambers 106. The system is thus referred to as a high-pressure EGR system 170 because the exhaust gasses received have yet to depressurize through the turbine 156. The high-pressure EGR line 172 is also in fluid communication with the intake manifold 130. To control the amount or quantity of the exhaust gasses combined with the intake air, the high-pressure EGR system 170 can include an adjustable EGR valve 174 disposed along the high-pressure EGR line 172. Hence, the ratio of exhaust gasses mixed with intake air can be varied during operation by adjustment of the adjustable EGR valve 174. Because the exhaust gasses may be at a sufficiently high temperature that may affect the combustion process, the high-pressure EGR system can also include an EGR cooler 176 disposed along the high-pressure EGR line 172 to cool the exhaust gasses.
In the second embodiment, a low-pressure EGR system 180 directs low-pressure exhaust gasses to the intake line 132 before it reaches the intake manifold 130. The low-pressure EGR system 180 includes a low-pressure EGR line 182 that communicates with the exhaust line 142 downstream of the turbine 156 so that it receives low-pressure exhaust gasses that have depressurized through the turbine. The low-pressure exhaust gasses are delivered to the engine intake system upstream of the compressor 152 so they can mix and be compressed with the incoming air. The system is thus referred to as a low-pressure EGR system because it operates using depressurized exhaust gasses. To control the quantity of exhaust gasses re-circulated, the low-pressure EGR line 182 can also include an adjustable EGR valve 184.
To further reduce emissions generated by the combustion process, the engine system 100 can include one or more after-treatment devices disposed along the exhaust line 142 that treat the exhaust gasses before they are discharged to the atmosphere. One example of an after-treatment device is a diesel particulate filter (DPF) 190 that can trap or capture particulate matter in the exhaust gasses. As the DPF becomes filled with particulate matter, it undergoes a process known as regeneration in which the particulate matter is oxidized. Regeneration may be done either passively or actively. Passive regeneration utilizes heat inherently produced by the engine to burn or incinerate the captured particulate matter. Active regeneration generally requires higher temperature and employs an added heat source such as a burner to heat the DPF. Another after-treatment device that may be included with the engine system is a selective catalytic reduction (SCR) system 192. In an SCR system 192, the exhaust gasses are combined with a reductant agent such as ammonia or urea and are directed through a catalyst that chemically converts or reduces the nitrogen oxides in the exhaust gasses to nitrogen and water. To provide the reductant agent, a separate storage tank 194, which is placed in fluid transfer with the SCR catalyst, may be associated with the SCR system. A diesel oxidation catalyst 196 is a similar after-treatment device that includes metals such as palladium and platinum that can act as catalysts to convert hydrocarbons and carbon monoxide in the exhaust gasses to carbon dioxide. Other types of catalytic converters, three way converters, mufflers and the like can also be included as possible after-treatment devices.
Reduction of emissions generated by the combustion process and a means to control the peak cylinder pressure, and thus the power generated by the second combustion stroke, can also be achieved by including a blowdown exhaust recirculation system 301.
In
One or more blowdown exhaust valves 310 can be associated with each combustion chamber 306 and can open and close to selectively expel blowdown exhaust gasses from the combustion chamber to the blowdown exhaust line 305. Thus, two separate paths for exhaust gas from the cylinders are created—the main path for exhaust gas passing through the exhaust valves 146, and a parallel path for blowdown exhaust gas passing through the blowdown exhaust valves 310. The blowdown exhaust line 305 directs the blowdown exhaust gasses into the intake manifold 130 for re-introduction into the combustion chamber 306.
Returning now to
For example, to monitor the pressure and/or temperature in the combustion chambers 106, the controller 200 may communicate with chamber sensors 210 such as a transducer or the like, one of which may be associated with each combustion chamber 106 in the engine block 104. The chamber sensors 210 can monitor the combustion chamber conditions directly or indirectly, for example, by measuring the backpressure exerted against the intake or exhaust valves, or other components that directly or indirectly communicate with the combustion cylinder such as glow plugs. During combustion, the chamber sensors 210 and the controller 200 can indirectly measure the pressure in the combustion chamber 106. The controller can also communicate with an intake manifold sensor 212 disposed in the intake manifold 130 and that can sense or measure the conditions therein. To monitor the conditions such as pressure and/or temperature in the exhaust manifold 140, the controller 200 can similarly communicate with an exhaust manifold sensor 214 disposed in the exhaust manifold 140. From the temperature of the exhaust gasses in the exhaust manifold 140, the controller 200 may be able to infer the temperature at which combustion in the combustion chambers 106 is occurring.
To measure the flow rate, pressure and/or temperature of the air entering the engine, the controller 200 can communicate with an intake air sensor 220. The intake air sensor 220 may be associated with, as shown, the intake air filter 160 or another intake system component such as the intake manifold. The intake air sensor 220 may also determined or sense the barometric pressure or other environmental conditions in which the engine system is operating.
For controlling the combustion process, the controller 200 can communicate with injector controls 230 that can control the fuel injectors 120 operatively associated with the combustion chambers 106. The injector controls 230 can selectively activate or deactivate the fuel injectors 120 to determine the timing of introduction and the quantity of fuel introduced by each fuel injector, for example, by further monitoring and control of the injection pressure of fuel provided to the fuel injectors 120. Regarding control of valve timing, the controller 200 can also communicate with a camshaft control 232 that is operatively associated with the camshaft 148 and/or camshaft actuator 149 to control the variable valve timing, when such a capability is used.
In embodiments having an intake throttle 162, the controller 200 can communicate with a throttle control 240 associated with the throttle and that can control the amount of air drawn into the engine system 100. Alternatively, the amount of air used by the engine may be controlled by variably controlling the intake valves in accordance with a Miller cycle, which includes maintaining intake valves open for a period during the compression stroke and/or closing intake valves early during an intake stroke to thus reduce the amount of air compressed in the cylinder during operation. The controller 200 can also be operatively associated with either or both of the high-pressure EGR system 170 and/or the low-pressure EGR system 180. For example, the controller 200 is communicatively linked to a high-pressure EGR control 242 associated with the adjustable EGR valve 174 disposed in the high-pressure EGR line 182. Similarly, the controller 220 can also be communicatively linked to a low-pressure EGR control 244 associated with the adjustable EGR valve 184 in the low-pressure EGR line 182. The controller 220 can thereby adjust the amount of exhaust gasses and the ratio of intake air/exhaust gasses introduced to the combustion process.
The engine system 100 can operate in accordance with a six-stroke combustion cycle in which the reciprocal piston disposed in the combustion chamber makes six or more strokes between the top dead center (TDC) position and bottom dead center (BDC) position during each cycle. A representative series of six strokes and the accompanying operations of the engine components associated with the combustion chamber 106 are illustrated in
The strokes are performed by a reciprocal piston 250 that is slidably disposed in an elongated cylinder 252 bored into the engine block. One end of the cylinder 252 is closed off by a flame deck surface 254 so that the combustion chamber 106 defines an enclosed space between the piston 250, the flame deck surface and the inner wall of the cylinder. The reciprocal piston 250 moves between the TDC position where the piston is closest to the flame deck surface 254 and the BDC position where the piston is furthest from the flame deck surface. The motion of the piston 250 with respect to the flame deck surface 254 thereby defines a variable volume 258 that expands and contracts.
Referring to
As illustrated in
Referring to
In reference to the embodiment illustrated in
When the piston 250 reaches the TDC position shown in
The quantity of the second fuel charge 264 introduced to the cylinder, in conjunction with oxygen that may remain within the cylinder, can be selected such that stoichiometric or near stoichiometric conditions for combustion are provided within the combustion chamber 106. At stoichiometric conditions, the ratio of fuel to air is such that substantially the entire second fuel charge will react with all the remaining oxygen in the combustion products 262. When the piston 250 is at or near the TDC position and combustion chamber 106 reaches the second maximum pressure 288, the second fuel charge 264 and the previous combustion products 262 may spontaneously ignite. Referring to
The second combustion event can further incinerate the unburned combustion products from the initial combustion event such as unburned fuel and soot. The quantity or amount of hydrocarbons in the resulting second combustion products 266 remaining in the cylinder 252 may also be reduced. Referring to
In a second compression stroke, the piston 350 can compress the combustion products 362 in the combustion chamber 306. During the second compression stroke, the blowdown exhaust valve 310 can open to expel a portion of the combustion products 362 as blowdown exhaust gasses. The blowdown exhaust line 305 directs the blowdown exhaust gasses into the intake manifold 130, the intake line 132, the high-pressure EGR line 172, or any other entry point in the engine system 300 to allow reintroduction of the blowdown exhaust gasses into the combustion chamber 306. Once the piston 350 reaches the TDC position, additional fuel can be introduced into the combustion chamber 306 to mix with the remaining combustion products 362. The compressed air/fuel/combustion product mixture combusts, forcing the piston 350 towards the BDC position during a second power stroke. During the exhaust stroke, the exhaust valves 146 open expelling a portion of the combustion products 362 from the combustion chamber 306 as exhaust gasses.
The industrial application for the apparatus and methods of a six-stroke engine system with blowdown exhaust system as described herein should be readily appreciated from the foregoing discussion. The present disclosure is applicable to any type of machine utilizing an internal combustion engine performing a six-stroke combustion cycle. It may be particularly useful in increasing efficiency of machines with six-stroke internal combustion engines.
Utilizing the apparatus taught in this disclosure can increase the efficiency of the engine 302 by reducing the pressure in the engine's combustion chambers during the second compression stroke of the piston. Referring to
The relationship between efficiency and the amount of blowdown gasses expelled is generally inversely related such that expelling large amounts of combustion products 362 from the variable volume 358 results in relatively greater efficiency, while expelling small amounts of or no combustion products results in relatively lower increased efficiency. Another benefit of reducing the amount of material to compress within the variable volume 358 is reduction of the peak cylinder pressure experienced in the combustion chamber 306 during the second compression stroke and the resulting forces applied to the engine 302 components such as the piston 350, the cylinder 352, and other components.
In addition to increasing efficiency, the disclosed engine system can also redirect or re-circulate the blow-down gasses through another combustion cycle in the combustion chambers to further reduce emissions in a manner similar to that provided by the described six-stroke cycle. As disclosed herein, the blowdown exhaust recirculation system 301 can include recirculation of the blowdown exhaust gasses expelled from the combustion chamber 306 back into the intake manifold 130. In such an engine system 300, efficiency can be increased by expelling at least a portion of the combustion products 362 from the variable volume 358 during the second compression stroke when the blowdown exhaust valve 310 opens. Rather than release the combustion products 362 directly into the atmosphere, however, the blowdown exhaust line 305 can direct the blowdown exhaust gasses back into the intake manifold 130. Once the combustion products 362 circulate back into the intake manifold 130, they mix with air and other materials taken into the intake manifold from the intake line 132 or exhaust gasses introduced into the intake manifold through the high pressure EGR line 172.
The combustion products 258 can be re-introduced into the combustion chamber 306 through the intake valves 136 for compression and combustion either during the first power stroke or second power stroke. The blowdown exhaust recirculation system 301 disclosed herein, therefore, can increase engine 302 efficiency by expelling combustion products 362 from the variable volume 358 between the first and second power strokes, but does so while minimizing emissions produced by the engine because the blowdown exhaust gasses are recirculated back into the combustion chamber 306 and re-combusted. The disclosed system seeks to balance efficiency and improved emissions reduction.
The illustrated method also includes sensing or otherwise measuring a second engine parameter at 506. The controller 200 can then compare the second engine parameter setpoint to the measured second engine parameter and comparing the measured second engine parameter with the calculated second engine parameter setpoint at 508. Based on the difference between the second engine parameter setpoint and the measured second engine parameter, the controller 200 can adjust the blowdown exhaust valve 310 in a manner to affect a change in the second engine parameter at 510 and bring it generally in accord with the second engine parameter setpoint for the determined first engine parameter. The controller 200 can optimize the combustion conditions within the combustion chamber 306 based on pre-determined optimization protocols based on the first engine parameter or other engine system parameters.
By way of example, the first engine parameter can be the engine speed and the second engine parameter can be the peak cylinder pressure. In such embodiments, the controller 200 determines the engine speed, then determines the peak cylinder pressure setpoint based on the engine speed. The peak cylinder pressure setpoint is a pre-determined target peak cylinder pressure for the particular engine speed. Through sensors or other known means of acquiring the peak cylinder pressure, the controller 200 takes a measurement of the actual peak cylinder pressure. The controller 200 then compares the measured peak cylinder pressure to the peak cylinder pressure setpoint and adjusts the blowdown exhaust valve 310 to bring the actual peak cylinder pressure to a value nearer to the value of the peak cylinder pressure setpoint.
One way to change the peak cylinder pressure can be varying the time or duration for which the blowdown exhaust valve 310 remains open during the second compression stroke. Generally, the longer the blowdown exhaust valve 310 remains open during the second compression stroke, the lower the peak cylinder pressure will be during the second power stroke. The peak cylinder pressure is lower because more combustion products 362 are expelled out of the variable volume 358 Thus, if the measured peak cylinder pressure is greater than the peak cylinder pressure setpoint, the controller 200 can control the blowdown exhaust valve 310 to remain open for a longer period of time to expel more combustion products 362 and decrease the peak cylinder pressure. Conversely, if the measured peak cylinder pressure is less than the peak cylinder pressure setpoint, the controller 200 can control the blowdown exhaust valve 310 to remain open for a shorter period of time to expel fewer combustion products 362 and increase the peak cylinder pressure.
The illustrated method can be repeated for as long as the engine 302 is operating or for a selected range of engine parameters calculated to optimize efficiency and emissions, as well as to ensure that the engine components operate reasonably within pre-determined mechanical stress levels.
The apparatus and methods described herein can be adapted to a large variety of machines. For example, various types of industrial machines, such as off-highway trucks, backhoe loaders, compactors, feller bunchers, forest machines, industrial loaders, wheel loaders and many other machines can benefit from the methods and systems described.
It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated.
Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.
