Engine control system having fuel-based adjustment

A control system for an engine having a cylinder is disclosed having an engine valve configured to affect a fluid flow of the cylinder, an actuator configured to move the engine valve, and an in-cylinder sensor configured to generate a signal indicative of a characteristic of fuel entering the cylinder. The control system also has a controller in communication with the actuator and the sensor. The controller is configured to determine the characteristic of the fuel based on the signal and selectively regulate the actuator to adjust a timing of the engine valve based on the characteristic of the fuel.

TECHNICAL FIELD

The present disclosure is directed to an engine control system and, more particularly, to an engine control system having fuel-based adjustment.

BACKGROUND

Combustion engines are often used for power generation applications. These engines can be gaseous-fuel driven and implement lean burn, during which air/fuel ratios are higher than in conventional engines. For example, these gas engines can admit about 75% more air than is theoretically needed for stoichiometric combustion. Lean-burn engines increase fuel efficiency because they utilize homogeneous mixing to burn less fuel than a conventional engine and produce the same power output.

One shortcoming of heavy duty natural gas engines is that they may not be able to operate using a wide range of fuel variants such as, for example, fuels having a wide range of varying methane numbers. Engine parameters such as, for example, compression ratio may limit the range of fuel that heavy duty natural gas engines may use, thereby limiting the applications for which a given engine may be used.

A natural gas engine system is described in European patent application publication EP 0 945 606 A2 (the '606 publication), by Kawamura. The '606 publication discloses an engine system having a turbocharger, and valve controllers for varying a timing of intake valves of an engine cylinder, to vary an effective compression ratio. The '606 publication also discloses temperature sensors for sensing a temperature of the intake air and combustion chamber walls. A controller unit controls the valve controllers based on input from the temperature sensors.

Although the engine system of the '606 publication may vary intake valve timing based on a sensed temperature, it fails to adjust engine operation based on fuel composition. Therefore, the engine system of the '606 publication may fail to increase the range of fuel variants that can be used in the engine.

The present disclosure is directed to overcoming one or more of the shortcomings set forth above and/or other deficiencies in existing technology.

SUMMARY OF THE DISCLOSURE

In accordance with one aspect, the present disclosure is directed toward a control system for an engine having a cylinder. The control system includes an engine valve configured to affect a fluid flow of the cylinder, an actuator configured to move the engine valve, and an in-cylinder sensor configured to generate a signal indicative of a characteristic of fuel entering the cylinder. The control system also includes a controller in communication with the actuator and the sensor. The controller is configured to determine the characteristic of the fuel based on the signal and selectively regulate the actuator to adjust a timing of the engine valve based on the characteristic of the fuel.

According to another aspect, the present disclosure is directed toward a method of operating an engine. The method includes directing a premixed air/fuel mixture into a cylinder of the engine and sensing a parameter indicative of a characteristic of a fuel within the premixed air/fuel mixture as the premixed air/fuel mixture enters the cylinder. The method also includes selectively adjusting engine valve timing of the engine based on the characteristic.

DETAILED DESCRIPTION

FIG. 1illustrates a generator set (genset)10having a prime mover12coupled to mechanically rotate a generator14that provides electrical power to an external load (not shown). Generator14may be, for example, an AC induction generator, a permanent-magnet generator, an AC synchronous generator, or a switched-reluctance generator. In one embodiment, generator14may include multiple pairings of poles (not shown), each pairing having three phases arranged on a circumference of a stator (not shown) to produce an alternating current with a frequency of about 50 and/or 60 Hz. Electrical power produced by generator14may be directed for offboard purposes to the external load.

Prime mover12may include an engine system100, as illustrated inFIG. 2. Engine system100may include an engine105, a variable valve actuation system110, an intake system115, an exhaust system120, and a control system125. Intake system115may deliver air and/or fuel to engine105, while exhaust system120may direct combustion gases from engine105to the atmosphere. Variable valve actuation system110may vary a valve timing of engine105to affect fluid flow of engine105. Control system125may control an operation of variable valve actuation system110, intake system115, and/or exhaust system120.

Engine105may be a four-stroke diesel, gasoline, or gaseous fuel-powered engine. As such, engine105may include an engine block130at least partially defining a plurality of cylinders135(only one shown inFIG. 2). In the illustrated embodiment ofFIG. 1, engine105is shown to include six cylinders135. However, it is contemplated that engine105may include a greater or lesser number of cylinders135and that cylinders135may be disposed in an “in-line” configuration, a “V” configuration, or in any other suitable configuration.

A piston140may be slidably disposed within each cylinder135, so as to reciprocate between a top-dead-center (TDC) position and a bottom-dead-center (BDC) position during an intake stroke, a compression stroke, a combustion or power stroke, and an exhaust stroke. Returning toFIG. 2, pistons140may be operatively connected to a crankshaft145via a plurality of connecting rods150. Crankshaft145may be rotatably disposed within engine block130, and connecting rods150may connect each piston140to crankshaft145so that a reciprocating motion of each piston140results in a rotation of crankshaft145. Similarly, a rotation of crankshaft145may result in a sliding motion of each piston140between the TDC and BDC positions. As shown in the lower portion of the graph ofFIG. 3, piston140may move through the intake stroke from the TDC position (crank angle of about 0 degrees) to the BDC position (crank angle of about 180 degrees) to draw air and/or fuel into the respective cylinder135. Piston140may then return to the TDC position (crank angle of about 360 degrees), thereby compressing the air/fuel mixture during the compression stroke. The compressed air/fuel mixture may ignite, causing piston140to move back to the BDC position (crank angle of about 540 degrees) during the power stroke. Piston140may then return to the TDC position (crank angle of about 720 degrees) to push exhaust gas from cylinder135during the exhaust stroke.

One or more cylinder heads155may be connected to engine block130to form a plurality of combustion chambers160. As shown inFIG. 1, cylinder head155may include a plurality of intake passages162and exhaust passages163integrally formed therein. One or more intake valves165may be associated with each cylinder135and movable to selectively inhibit flow between intake passages162and combustion chambers160. One or more exhaust valves170may also be associated with each cylinder135and movable to selectively inhibit flow between combustion chambers160and exhaust passages163. Additional engine components may be disposed in cylinder head155such as, for example, a plurality of sparkplugs172that ignite an air/fuel mixture in combustion chambers160.

Combustion pressures may vary between different cylinders135and between different combustion cycles of a single cylinder135during engine operation. Combustion pressures may vary between cylinders135, for example, because of an uneven distribution of the air/fuel mixture delivered to the plurality of cylinders135via intake valve165. Combustion pressures may vary between combustion cycles of the same cylinder135, for example, because varying amounts of the delivered air/fuel mixture may be combusted in a given combustion cycle, thereby leaving some of the air/fuel mixture behind within cylinder135. This residual air/fuel mixture may affect the combustion pressure of a subsequent combustion cycle. For example, variation between combustion cycles may occur because of strong or weak combustion events.

A strong combustion event may occur within a given cylinder135when substantially all of the air/fuel mixture trapped within cylinder135is fully combusted, resulting in a combustion pressure that may be higher than an average peak cylinder pressure. But, because substantially all of the air/fuel mixture within that cylinder135may be combusted during the strong combustion event, the combustion cycle immediately following the strong combustion event may be relatively weak within the same cylinder135. That is, because there may be less residual air/fuel mixture than in a typical combustion cycle, the cylinder pressure within that cylinder135during the subsequent combustion cycle may have a pressure lower than the average peak cylinder pressure, varying significantly from the high combustion pressure of the previous cycle.

A weak combustion event may have an opposite effect, but also cause a significant pressure variation between combustion cycles. Specifically, during a weak combustion event, there may be significant pockets of the air/fuel mixture within cylinder135that do not combust, resulting in a combustion pressure that may be lower than an average peak cylinder pressure. Because there may be a significant amount of residual air/fuel mixture within cylinder135from the previous cycle, when additional air/fuel mixture is normally admitted for the subsequent cycle, there may be much more of the air/fuel mixture trapped within cylinder135than desired. As a result, the combustion pressure during the subsequent combustion cycle may be higher than the average peak cylinder pressure, resulting in a significant pressure variation between combustion cycles.

Detonation (i.e., knock) is an abnormal form of combustion that may be caused by cycle-to-cycle pressure variations. Detonation may cause components of engine105to fail such as, for example, a head gasket. Detonation may occur when excessive pressure within cylinder135(e.g., during a combustion cycle following a weak combustion event) causes the air/fuel mixture to autoignite. Autoignition may result in multiple pockets of simultaneous combustion within combustion chamber160instead of singular combustion. The multiple pockets of combustion can collide with each other with significant force, causing a rapid rise in cylinder pressure and a metallic pinging (i.e., knocking). The detonation forces may subject engine components to overloading, and continued detonation may reduce a service life of engine105.

Engine105may include a plurality of valve actuation assemblies175that affect movement of intake valves165and/or exhaust valves170to help minimize engine knock. Each cylinder135may have an associated valve actuation assembly175. Referring back toFIG. 2, each valve actuation assembly175may include a rocker arm180connected to move a pair of intake and/or exhaust valves165,170via a bridge182. Rocker arm180may be mounted to cylinder head155at a pivot point185, and connected to a rotating camshaft200by way of a push rod190. Camshaft200may be operatively driven by crankshaft145, and may include a plurality of cams195that engage and move push rods190.

As pistons140move through the four stokes of the combustion cycle (i.e., intake, compression, power, and exhaust), crankshaft145may cyclically drive each valve actuation assembly175to move intake valves165and/or exhaust valves170. As shown inFIG. 3, valve actuation assembly175may cause intake valves165to open during the intake stroke of piston140. Actuation of intake valves165may generally follow profile201shown in the upper portion of the graph ofFIG. 3. Intake valve165may open during the intake stroke, for example, at a crank angle of about 690° to about 0°, and may close at a crank angle of about 210°. Intake valves165may displace from a closed position to a maximum open position, during which the air/fuel mixture may be admitted into combustion chamber160.

A pressure profile of cylinder135may substantially match a desired profile203during typical combustion events, as shown in the lower portion of the graph ofFIG. 3. During a typical combustion event, a pressure within cylinder135may reach a peak at a crank angle of between about 360° to about 375° (i.e., at the end of the compression and beginning of the power strokes). Also, during the compression stroke of a typical combustion event, a rate of the pressure rise within cylinder135(i.e., a rise-rate of the pressure) may substantially match the slope of desired profile203(i.e., when a strong or weak combustion event does not occur). Desired profile203illustrates a desired combustion state free from significant detonation, where there is singular combustion of a desired magnitude.

An undesired profile208, shown inFIG. 3, illustrates a combustion state in which multiple pockets of combustion occur and/or the pressure rise-rate is greater than desired and detonation is likely. The peak cylinder pressure during detonation may be reached earlier than TDC (i.e., during the compression stroke), which is undesirable for maximum efficiency, and have a peak higher than desired. Another undesired profile206, shown inFIG. 3, illustrates a combustion state in which weak combustion occurs. Weak combustion may occur when a pressure rise-rate within cylinder135is less than a desired pressure-rise rate (i.e., less than that of profile203) and/or a peak thereof is lower than desired. Profiles203,206, and208are illustrative only, and may vary based on engine operation such as, for example, based on valve timing.

Varying a closing of intake valve165may change the pressure profile within cylinder135(i.e., a rise-rate and/or a magnitude of the pressure). As shown by a family of curves207inFIG. 3, a closing of intake valve165may be selectively varied during the intake and/or the compression strokes by any appropriate amount. When intake valve165is closed within the family of curves207, intake valve165may be selectively advanced and/or retarded. When intake valve165is advanced within the family of curves207(i.e., the closing is adjusted to be further away from profile201), less air/fuel mixture may be trapped within cylinder135, resulting in a decrease in pressure rise-rate and/or pressure magnitude within cylinder135. When intake valve165is retarded within the family of curves207(i.e., the closing is adjusted toward profile201), more air/fuel mixture may be trapped within cylinder135, resulting in an increase in pressure rise-rate and/or pressure magnitude within cylinder135. Intake valve165may also be selectively varied during the intake and/or the compression strokes by any appropriate amount within a family of curves209, shown inFIG. 3. When intake valve165is closed within the family of curves209, the closing may be selectively advanced and/or retarded. When intake valve165is retarded within the family of curves209(i.e., the closing moves further away from profile201), less air/fuel mixture may be trapped within cylinder135, resulting in a decrease in pressure rise-rate and/or pressure magnitude within cylinder135. When intake valve165is advanced within the family of curves209(i.e., the closing moves toward profile201), more air/fuel mixture may be trapped within cylinder135, resulting in an increase in pressure rise-rate and/or pressure magnitude within cylinder135. Intake valve165may be varied by an amount that substantially correlates to a comparison of an actual or anticipated pressure profile with the desired profile203. Intake valve165may be varied by a greater or lesser amount, as required, to regulate the fluid flow to cylinder135and thereby bring the combustion profile within cylinder135toward the desired profile203.

For example, when profile208is detected within cylinder135, the closing of intake valve165may be advanced within the family of curves207or retarded within the family of curves209to decrease the magnitude and pressure rise-rate within cylinder135toward desired profile203. The closing of intake valve165may thereby be adjusted away from a profile of intake valve165having a timing that has not been varied (i.e., away from unadjusted profile201) when the pressure within cylinder135is higher than a desired pressure. In contrast, when profile206is detected within cylinder135, the closing of intake valve165may be retarded within the family of curves207or advanced within the family of curves209to increase the magnitude and pressure rise-rate within cylinder135toward desired profile203. The closing of intake valve165may thereby be adjusted toward a profile of intake valve165having a timing that has not been varied (i.e., toward unadjusted profile201) when the pressure within cylinder135is lower than a desired pressure.

The timing of intake valve165may be adjusted based on detonation detection, a strong combustion detection, and/or a weak combustion detection (i.e., based on a measured rise-rate, a number of combustion pressure peaks, a magnitude of the peak, and/or an angular location of the peak). As shown in profile208ofFIG. 3, detonation caused by autoignition may cause a slope of the pressure rise-rate in cylinder135to increase sharply, and the peak cylinder pressure may be reached before TDC of the compression stroke. Similarly, detonation caused by multiple combustion pockets may be observed as a plurality of sharp rises and/or drops in the pressure rise-rate. In profile208, the pressure rise rate may sharply increase and/or decrease in an irregular pattern. The closing of intake valve165may be adjusted to reduce the likelihood and/or magnitude of detonation, and to create a balance between strong and weak combustion events. The timing of intake valve165may also be adjusted based on a detection of fuel quality. A low fuel quality (i.e., a fuel having a low methane number) may be more prone to detonation (i.e., profile208), requiring valve timing to be adjusted. A high quality fuel such as, for example, a detonation-resistant pipeline gas may also require valve timing to be adjusted. It is also contemplated that the timing of intake valve165may be adjusted based on other parameters such as, for example, ambient air conditions including humidity and altitude.

It is contemplated that an opening of exhaust valve170may also or alternatively be advanced or retarded by variable valve actuation device202. As illustrated inFIG. 3, an opening of exhaust valve170may be selectively advanced or additionally opened during portions of the compression and/or power strokes. Because more air/fuel mixture may escape from cylinder135during the compression and/or power strokes when the opening of exhaust valve170is advanced or during an additional opening, the amount of trapped mass within cylinder135may decrease, thereby decreasing a combustion pressure or a rise-rate, and/or the angular location of peaks within cylinder135may shift. The opening of exhaust valve170may also be selectively retarded during portions of the compression and/or power strokes. Because less air/fuel mixture may escape from cylinder135when the opening of exhaust valve170is retarded, the amount of trapped mass within cylinder135may increase, thereby increasing a combustion pressure, a rise-rate, and/or shifting the angular location of peaks within cylinder135.

Variable valve actuation system110may include a plurality of variable valve actuation devices202configured to adjust timings of intake valves165and/or exhaust valves170to reduce effects of detonation, strong combustion events, and/or weak combustion events. As shown inFIGS. 1 and 2, variable valve actuation device202may be attached to and/or enclosed by a valve housing205of engine105. Each cylinder135may have an associated variable valve actuation device202. Variable valve actuation device202may selectively adjust an opening timing, closing timing, and/or lift magnitude of intake valves165and/or exhaust valves170. Variable valve actuation device202may be any suitable device for varying a valve timing such as, for example, a hydraulic, pneumatic, or mechanical device.

In one example, variable valve actuation device202may be operatively connected to rocker arm180, intake valve165, and/or exhaust valve170to selectively disconnect a movement of intake and/or exhaust valves165,170from a movement of rocker arm180. For example, variable valve actuation device202may be selectively operated to supply hydraulic fluid, for example, at a low or a high pressure, in a manner to resist closing of intake and/or exhaust valves165,170. That is, after valve actuation assembly175is no longer holding intake valve165and/or exhaust valve170open, the hydraulic fluid in variable valve actuation device202may hold intake valve165and/or exhaust valve170open for a desired period. Similarly, the hydraulic fluid may be used to advance a closing of intake valve165and/or exhaust valve170so that intake valve165and/or exhaust valve170closes earlier than the timing affected by valve actuation assembly175. Alternatively, intake and/or exhaust valves165,170may be moved solely by variable valve actuation device202without the use of cams and/or rocker arms, if desired.

Variable valve actuation device202may selectively advance or retard a closing of intake and/or exhaust valves165,170during the different strokes of engine105. Intake valve165may be closed early, for example, at a crank angle of between about 180° and about 210°. Control system125may also control variable valve actuation device202to retard a closing of intake valve165. Intake valve165may be closed, for example, at a crank angle of between about 210° and about 300°. Exhaust valve170may be varied to open at a crank angle of between about 510° and about 570° and may be varied to close at a crank angle of between about 700° and about 60°. Exhaust valve170may also be opened at a crank angle of about 330° and closed at a crank angle of about 390°. Control system125may control each variable valve actuation device202to vary the valve timing of each cylinder135independently of the valve timing of any other cylinder135. Control system125may thereby independently control a throttling of each cylinder135solely by varying a timing of intake valves165and/or exhaust valves170.

Referring back toFIG. 2, intake system115may direct air and/or fuel into combustion chambers160, and may include a single fuel injector210, a compressor215, and an intake manifold220. Compressor215may compress and deliver an air/fuel mixture from fuel injector210to intake manifold220.

Compressor215may draw ambient air into intake system115via a conduit225, compress the air, and deliver the compressed air to intake manifold220via a conduit230. This delivery of compressed air may help to overcome a natural limitation of combustion engines by eliminating an area of low pressure within cylinders135created by a downward stroke of pistons140. Therefore, compressor215may increase the volumetric efficiency within cylinders135, allowing more air/fuel mixture to be burned, resulting in a larger power output from engine105. It is contemplated that a cooler for further increasing the density of the air/fuel mixture may be associated with compressor215, if desired.

Fuel injector210may inject fuel at a low pressure into conduit225, upstream of compressor215, to form an air/fuel mixture. Fuel injector210may be selectively controlled by control system125to inject an amount of fuel into intake system115to substantially achieve a desired air-to-fuel ratio of the air/fuel mixture. Variable valve actuation device202may vary a timing of intake valves165and/or exhaust valves170to control an amount of air/fuel mixture that is delivered to cylinders135.

Exhaust system120may direct exhaust gases from engine105to the atmosphere. Exhaust system120may include a turbine235connected to exhaust passages163of cylinder head155via a conduit245. Exhaust gas flowing through turbine235may cause turbine235to rotate. Turbine235may then transfer this mechanical energy to drive compressor215, where compressor215and turbine235form a turbocharger250. In one embodiment, turbine235may include a variable geometry arrangement255such as, for example, variable position vanes or a movable nozzle ring. Variable geometry arrangement255may be adjusted to affect the pressure of air/fuel mixture delivered by compressor215to intake manifold220. Turbine235may be connected to an exhaust outlet via a conduit260. It is also contemplated that turbocharger250may be replaced by any other suitable forced induction system known in the art such as, for example, a supercharger, if desired.

Control system125may include a controller270configured to control the function of the various components of engine system100in response to input from one or more sensors272. Sensors272may be configured to monitor an engine parameter indicative of a pressure within cylinders135(i.e., robustness, pressure, and/or temperature of a combustion event). Each sensor272may be disposed within an associated cylinder135(i.e., in fluid contact with a respective one of combustion chambers160), and may be electrically connected to controller270. Sensor272may be any suitable sensing device for sensing an in-cylinder pressure such as, for example, a piezoelectric crystal sensor or a piezoresistive pressure sensor. Sensors272may measure a pressure within cylinders135during, for example, the compression stroke and/or the power stroke, and may generate a corresponding signal. Sensors272may transfer signals that are indicative of the pressures within cylinders135to controller270.

Based on the signals, controller270may determine a combustion profile for each cylinder135. The combustion profile may be a measurement of how the combustion pressure within cylinder135changes during a combustion cycle and from cycle to cycle. The combustion profile may be a continuous indication of combustion pressure within each cylinder135and may be used to predict, for example, whether strong, weak, or normal combustion will occur in a subsequent combustion event. Controller270may monitor the signals over time to determine a pressure rise-rate within cylinder135, a number of pressure peaks during a single cycle, a magnitude of the peaks, and/or an angular location of the peaks. Controller270may then relate this information to the amount of the air/fuel mixture in cylinder135at any given time to thereby determine a combustion pressure profile of cylinder135.

Controller270may then compare the pressure profiles of each cylinder135to a desired profile. In one example, the desired profile may be a profile that is predetermined such that balancing between cylinders135may be achieved. That is, the profile of one cylinder135may be compared with the profile of other cylinders135of engine105. In another example, the desired profile may be a fixed base profile that may correspond to a given engine rating. In one embodiment, the desired profiles may be stored within a map of controller270. Based on a comparison of the monitored profile with the desired profile, controller270may make adjustments to the timings of valves165,170.

For example, controller270may compare the pressure rise-rate of one cylinder135to profiles203. If the monitored pressure rise-rate substantially matches that of profile203, then controller270may determine that cylinder135has a desired combustion profile. If the pressure rise-rate substantially matches that of profile208, then controller270may determine that cylinder135has a combustion profile with a rapid pressure rise-rate and/or multiple combustion pockets, indicating the possibility of detonation.

Controller270may also utilize the signal input from sensors272to determine an amount of air/fuel mixture remaining in cylinders135. For example, controller270may determine, based on the monitored combustion profile, that a strong or weak combustion event has occurred in a given cylinder135during a given combustion cycle. A combustion profile indicating strong combustion may be a profile having a higher average pressure, peak pressure, or rise-rate than that of profile203(i.e., profile208). A strong combustion cycle may indicate to controller270that there is less residual air/fuel mixture remaining in cylinder135than desired. A combustion profile indicating weak combustion (i.e., profile206) may have an average pressure, peak pressure, or pressure rise-rate that is substantially lower than that of profile203. A weak combustion cycle may indicate to controller270that there is more residual air/fuel mixture remaining in cylinder135than desired.

Controller270may also relate the signal from sensors272to a characteristic of a fuel such as fuel type and/or fuel quality. Controller270may input the signal from sensors272as data into an algorithm that determines fuel type and/or fuel quality as a function of cylinder pressure. Using the algorithm, controller270may determine fuel attributes such as methane number. Methane number is indicative of a detonation-resistance of a fuel, and is thereby indicative of fuel type and/or fuel quality. Engine105may be configured to operate using a desired fuel composition having a desired fuel type and/or quality and a corresponding desired methane number that results in desired combustion (i.e., profile203). Controller270may relate the signal from sensors272to the desired cylinder pressure (i.e., profile203) associated with the desired fuel type and/or fuel quality. It is also contemplated, as an alternative to the pressure measurement of step300, that the fuel type and/or quality may be provided to controller270as a preprogrammed value or as an input provided by an operator.

Based on the determined fuel type and/or quality, controller270may make an appropriate adjustment to engine105. Specifically, controller270may control variable valve actuation device202to selectively advance and/or retard intake and/or exhaust valves165,170of cylinders135. For example, controller270may advance a closing of intake valves165and/or retard an opening of exhaust valves170when the fuel quality is higher than the desired fuel quality. Controller270may retard a closing of intake valves165and/or advance an opening of exhaust valves170when the fuel quality is lower than the desired fuel quality. Controller270may selectively advance and/or retard intake valves165during, for example, an intake stroke, and/or selectively advance or retard exhaust valve170during the compression and/or power strokes. Controller270may selectively advance and/or retard intake and/or exhaust valves165,170based on, for example, sensor input measured during a stroke of a subsequent engine cycle or sensor input measured during the same stroke as the advancing and/or retarding.

Controller270may be any type of programmable logic controller known in the art for automating machine processes, such as a switch, a process logic controller, or a digital circuit. Controller270may serve to control the various components of engine system100. Controller270may be electrically connected to the plurality of variable valve actuation devices202via a plurality of electrical lines275. Controller270may also be electrically connected to the plurality of sensors272via a plurality of electrical lines280. Controller270may be electrically connected to variable geometry arrangement255via an electrical line285. It is also contemplated that controller270may be electrically connected to additional components and sensors of engine system100such as, for example, an actuator of fuel injector210, if desired.

Controller270may include input arrangements that allow it to monitor signals from the various components of engine system100such as sensors272. Controller270may rely upon digital or analog processing of input received from components of engine system100such as, for example, sensors272and an operator interface. Controller270may utilize the input to create output for controlling engine system100. Controller270may include output arrangements that allow it to send output commands to the various components of engine system100such as variable valve actuation devices202, variable geometry arrangement255, fuel injector210, and/or an operator interface.

Controller270may have stored in memory one or more engine maps and/or algorithms. Controller270may include one or more maps stored within an internal memory, and may reference these maps to determine a required change in engine operation, a modification of an engine parameter required to affect the required change in engine operation, and/or a capacity of engine105for the modification. Each of these maps may include a collection of data in the form of tables, graphs, and/or equations.

Controller270may have stored in memory algorithms associated with determining required changes in engine operation based on engine parameters such as, for example, combustion pressure. For example, controller270may include an algorithm that performs a statistical analysis of the combustion pressures within the plurality of cylinders135from combustion cycle to combustion cycle. Based on input received from sensors272, the algorithm determines an average cylinder pressure per combustion cycle. The algorithm may then determine the statistical deviation of the combustion pressure of each cylinder135from the average combustion pressure. Using the statistical deviation, the algorithm may identify which cylinder pressures are required to be increased or decreased to reduce the variation in pressure. The algorithm may perform a similar statistical analysis of pressure variation between combustion cycles (i.e., as a function of time), to identify which cylinders135have combustion pressures that should be increased or decreased in subsequent combustion cycles.

INDUSTRIAL APPLICABILITY

The disclosed engine control system may be used in any machine having a combustion engine where consistent operation thereof is a requirement. For example, the engine control system may be particularly applicable to gaseous-fuel driven engines utilized in electrical power generation applications. Operation of genset10will now be described.

Engine105may combust fuel of a desired fuel quality having a desired methane number, which may result in normal combustion (i.e., profile203in the lower portion ofFIG. 3). During normal combustion events, pistons140may move through the four strokes of the combustion cycle. The movement of pistons140drives the actuation of intake valves165and exhaust valves170via valve actuation assembly175. Profile203, shown in the lower portion ofFIG. 3, may occur during normal combustion within cylinder135.

Engine105may also combust fuel having a quality that is higher than the desired fuel quality (i.e., fuel having a methane number that is higher than the desired methane number). When the fuel quality is higher than the desired fuel quality, the closing of intake valve165may be retarded within the family of curves207or advanced within the family of curves209to increase an amount of trapped mass within cylinder135(i.e., adjusted toward unadjusted profile201of intake valve165having a timing that has not been varied). Controller270may simultaneously control variable geometry arrangement255to increase an orifice size of turbine235. The increased orifice size reduces a speed of rotation of turbine235, which decreases a pressure of the charge air (i.e., the amount of boost) provided by compressor215to intake manifold220. Controller270may thereby control intake valve165and turbocharger250to substantially maintain an effective compression ratio of cylinder135when fuel quality is higher than the desired fuel quality.

Engine105may also combust fuel having a quality that is lower than the desired fuel quality (i.e., having a methane number that is lower than the desired methane number). When the fuel quality is lower than the desired fuel quality, the closing of intake valve165may be advanced within the family of curves207or retarded within the family of curves209to decrease an amount of trapped mass within cylinder135(i.e., adjusted away from unadjusted profile201of intake valve165having a timing that has not been varied). Controller270may simultaneously control variable geometry arrangement255to decrease an orifice size of turbine235. The decreased orifice size increases a speed of rotation of turbine235, which increases a pressure of the charge air (i.e., the amount of boost) provided by compressor215to intake manifold220. Controller270may thereby control intake valve165and turbocharger250to lower an effective compression ratio of cylinder135when fuel quality is lower than the desired fuel quality.

Engine system100may adjust the operation of engine105based on fuel composition. Controller270may control a closing of intake valve165and an operation of turbocharger250to adjust the effective compression ratio of cylinders135. Engine system100may thereby increase the range of varying compositions of fuel that can be used in engine105, allowing engine105to be readily adaptable to various applications requiring fuel compositions of varying quality.