System and method for detection of changes to compression ratio and peak firing pressure of an engine

A system includes a cylinder, a piston, a sensor configured to detect vibrations of the cylinder, piston, or both that correspond with varying pressures within the cylinder, and a controller coupled to the sensor. The controller is configured to receive a first signal from the sensor corresponding with first vibrations of the cylinder and to deduce from the first signal a first operating value of a parameter indicative of peak firing pressure at a first time, to compare the first operating value with a baseline value of the parameter indicative of peak firing pressure to detect a change in peak firing pressure, to receive a second signal from the sensor corresponding with second vibrations of the cylinder and to deduce from the second signal a second operating value of the parameter indicative of peak firing pressure at a second time, and to compare the second operating value with the baseline value to confirm the change in peak firing pressure.

BACKGROUND

The subject matter disclosed herein relates to reciprocating engines and, more specifically, to monitoring and control of parameters of the engine

Combustion engines typically combust a carbonaceous fuel, such as natural gas, gasoline, diesel, and the like, and use the corresponding expansion of high temperature and pressure gases to apply a force to certain components of the engine, e.g., piston disposed in a cylinder, to move the components over a distance. Each cylinder may include one or more valves that open and close correlative with combustion of the carbonaceous fuel. For example, an intake valve may direct an oxidizer such as air into a combustion chamber of the cylinder, while a fuel injector may inject fuel into the combustion chamber of the cylinder. The fuel and air then mix and combust in the combustion chamber to generate combustion fluids, e.g., hot gases, which may then be directed to exit the combustion chamber of the cylinder via an exhaust valve. Accordingly, the carbonaceous fuel is transformed into mechanical motion, useful in driving a load. For example, the load may be a generator that produces electric power.

In order to control efficiency and/or performance of the engine, the fuel-air mixture is ignited when the piston is at a particular location in the cylinder. Unfortunately, ignition or timing of the ignition of the fuel-air mixture may become inaccurate over time. Inaccurate ignition may result in a change (e.g., a rise or fall) in peak firing pressure, thereby reducing an efficiency and/or performance of the engine. Likewise, an increase in compression ratio and/or peak firing pressure may cause detonation (e.g., pre-ignition, knocking, or pinging) of the fuel-air mixture in the combustion chamber, which also reduces an efficiency and/or performance of the engine. Accordingly, it may be beneficial to improve detection of ignition processes in reciprocating engines.

BRIEF DESCRIPTION

In a first embodiment, a reciprocating engine system includes a cylinder, a piston disposed within the cylinder, a sensor disposed proximate to the cylinder and configured to detect vibrations of the cylinder, piston, or both that correspond with varying pressures within the cylinder, and a controller communicatively coupled to the sensor. The controller is configured to receive a first signal from the sensor corresponding with first vibrations of the cylinder and to deduce from the first signal a first operating value of a parameter indicative of peak firing pressure at a first time, to compare the first operating value with a baseline value of the parameter indicative of peak firing pressure to detect a change in peak firing pressure, to receive a second signal from the sensor corresponding with second vibrations of the cylinder and to deduce from the second signal a second operating value of the parameter indicative of peak firing pressure at a second time, and to compare the second operating value with the baseline value to confirm the change in peak firing pressure.

In a second embodiment, a method includes detecting, via knock sensors, first vibrational profiles of corresponding cylinders of a reciprocating engine over a first combustion cycle, and a second vibrational profiles of the corresponding over a second combustion cycle, wherein the first and second vibrational profiles are indicative of corresponding first and second pressures within the corresponding cylinders over the first and second combustion cycles, respectively. The method also includes receiving, via a controller, first signals and second signals from the knock sensors that correspond with the first and second vibrational profiles, respectively. The method also includes determining, via the controller, first operating values of a parameter indicative of peak firing pressure from the first signals, and second operating values of the parameter indicative of peak firing pressure from the second signals. Further, the method includes comparing, via the controller, the first operating values with a baseline value of the parameter indicative of peak firing pressure to determine a change in peak firing pressure in one or more cylinders of the corresponding cylinders. Further still, the method includes comparing, via the controller, the second operating values with the baseline value of the parameter indicative of peak firing pressure to confirm the change in peak firing pressure in the one or more cylinders of the corresponding cylinders.

In a third embodiment, a non-transitory computer readable medium comprising executable instructions that, when executed, cause a processor to: receive, from a knock sensor, a first signal indicative of first vibrations within a cylinder that correspond with a first range of pressures within the cylinder, receive, via the knock sensor, a second signal indicative of second vibrations within the cylinder that correspond with a second range of pressures within the cylinder, and deduce a first value of a parameter indicative of peak firing pressure from the first signal and a second value of the parameter indicative of peak firing pressure from the second signal. Further, the instructions, when executed, cause the processor to compare the second value with the first value to detect a rise in peak firing pressure.

DETAILED DESCRIPTION

The present disclosure is directed to reciprocating engines and, more specifically, to detection of changes (e.g., increase or decreases) in compression ratio and/or peak firing pressure using a sensor, such as a knock sensor, and a controller. For example, the reciprocating engine, which will be described in detail below with reference to the figures, includes a cylinder and a piston disposed within the cylinder (or multiple cylinders, each having a corresponding piston disposed within the cylinder). The reciprocating engine includes an internal combustion engine, such as a spark ignition engine or compression-ignition engine (e.g., a diesel engine) The reciprocating engine includes an ignition feature that ignites a fuel-oxidant (e.g., fuel-air) mixture within a combustion chamber proximate to the piston (e.g., within the cylinder and above the piston). The hot combustion gases generated from ignition of the fuel-air mixture drive the piston within the cylinder. In particular, the hot combustion gases expand and exert a pressure against the piston that linearly moves the position of the piston from a top portion to a bottom portion of the cylinder during an expansion stroke. The piston converts the pressure exerted by the hot combustion gases (and the piston's linear motion) into a rotating motion (e.g., via a connecting rod coupled to, and extending between, the piston and a crankshaft) that drives one or more loads, e.g., an electrical generator.

Generally, the reciprocating engine includes an ignition feature or mechanism (e.g., a spark plug) that ignites the fuel-air mixture within the combustion chamber as the piston moves upwardly toward the top portion of the cylinder. For example, the spark plug may ignite the fuel-air mixture when the crank angle of the crankshaft is approximately 5-35 degrees from top dead center (TDC), where TDC is a “highest” position of the piston within the cylinder. Improved timing of the ignition may improve performance of the reciprocating engine. For example, poor timing of the ignition may cause pre-ignition (e.g., engine knocking, pinging), which describes a condition in which pockets of the fuel-air mixture combust outside an envelope of a primary combustion front. Pre-ignition may significantly reduce recovery of work (e.g., by the piston) from the expanding combustion gases.

Thus, in accordance with the present disclosure, a knock sensor (or other sensor suitable for measuring vibration and/or acoustics) is included in, or proximate to, each cylinder of the reciprocating engine and may be communicatively coupled to a controller. As used herein, the term knock sensor may include any suitable vibration sensor, acoustic sensor, or other sensor, or a combination thereof, which may or may not be used to detect knock in the engine. Furthermore, any discussion of vibration or sensor measurements, data analysis, determination of engine parameters (e.g., peak firing pressure and compression ratio), and associated controls is also intended to cover the same using acoustics sensor measurements, and vice versa. The knock sensor detects, for example, vibrations of the cylinder corresponding with varying pressures within the cylinder, and the controller converts a vibrational (e.g., sound) profile of the cylinder, provided via a signal by the knock sensor, into useful parameters for determining combustion conditions (e.g., pressure conditions) in the cylinder. For example, the knock sensor detects vibrations in, or proximate to, the cylinder, and communicates the signal indicative of the vibrational profile (e.g., graph) to the controller. The controller converts the signal indicative of the vibrational profile to a parameter indicative of pressure within the cylinder. Further, peak firing pressure may be deduced from the signal, where peak firing pressure describes a maximum pressure exerted by the expanding combustion gases on the piston during each expansion stroke. The parameter indicative of pressure within the cylinder (e.g., peak firing pressure) may be a position of the piston within the cylinder (e.g., measured in crank angles at, for example, the time of ignition), a speed (e.g., maximum speed) of the piston within the cylinder, an acceleration (e.g., maximum acceleration) of the piston within the cylinder, or a pressure (e.g., maximum pressure or peak firing pressure) within the cylinder. In other words, operating or actual peak firing pressure may be determined from any one of these parameters (e.g., position, speed, acceleration, or pressure).

Generally, a baseline peak firing pressure is determined for the reciprocating engine by the manufacturer before installation and operational use. To determine a baseline peak firing pressure, the engine system may be operated to peak firing pressure and data captured via the sensor(s) may be logged. The logged data may then be processed into one or more curves or graphs. For example, noise level as a function of time may be used as one of the curves, as well as noise frequency, noise phase, noise amplitude, and so on. Such curve(s) are then considered baseline curves representative of the peak firing pressure. It should be noted, however, that the curves may be determined without generating a visual representation (e.g., a graph) of each curve.

While in one embodiment the baseline peak firing pressure may be determined, e.g., in a factory before the reciprocating engine is installed for normal use, in another embodiment the baseline peak firing pressure may be determined in situ after delivery of the engine to the customer. The reciprocating engine may be operated to achieve baseline peak firing pressure during each expansion stroke. For example, an increase in operating peak firing pressure above the baseline peak firing pressure may result in engine knocking (e.g., local pockets of combustion outside the primary combustion front) that reduces an efficiency of the reciprocating engine, as the piston may be unable to efficiently recover work from the expanding combustion gases.

Accordingly, as previously described, the knock sensor transmits a signal indicative of vibration of the cylinder (or piston within the cylinder) to the controller, and the controller converts the signal into one or more of the parameters indicative of peak firing pressure (e.g., position, speed, acceleration, or pressure). The controller may determine an actual value (e.g., operating value) of the parameter indicative of peak firing pressure and compare the actual value with the value of the baseline peak firing pressure (or parameter indicative of peak firing pressure). For example, the controller may first determine the operating peak firing pressure from the parameter indicative of peak firing pressure, and may then compare the operating peak firing pressure with the baseline peak firing pressure. Alternatively, the controller may convert the baseline peak firing pressure into a baseline parameter indicative of peak firing pressure and compare the baseline parameter indicative of peak firing pressure with the actual parameter indicative of peak firing pressure. In either embodiment, the controller may determine if the operating peak firing pressure exceeds the baseline peak firing pressure by more than a pre-determined cut-off factor (or threshold value). For example, the operating peak firing pressure of the cylinder may fluctuate slightly over time, so a cut-off factor may be introduced into the comparison to compensate for slight fluctuations in pressure. If the actual peak firing pressure exceeds the baseline peak firing pressure plus cut-off factor, the knock sensor may take another reading and transmit the reading to the controller, thereby enabling the controller to compare a second reading with the baseline peak firing pressure and cut-off factor to confirm the rise in peak firing pressure. Further, in some embodiments, the controller may compare the second reading with the first reading to determine if the peak firing pressure has increased even more since the first reading (e.g., by determining a rate of change or slope between readings). Other control logic may also be employed, and will be described in detail below with reference to the figures.

Turning to the drawings,FIG. 1illustrates a block diagram of an embodiment of a portion of an engine driven power generation system8. As described in detail below, the system8includes an engine10(e.g., a reciprocating internal combustion engine) having one or more combustion chambers12(e.g., 1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 14, 16, 18, 20, or more combustion chambers12). An air supply14is configured to provide a pressurized oxidant16, such as air, oxygen, oxygen-enriched air, oxygen-reduced air, or any combination thereof, to each combustion chamber12. The combustion chamber12is also configured to receive a fuel18(e.g., a liquid and/or gaseous fuel) from a fuel supply19, and a fuel-air mixture ignites and combusts within each combustion chamber12. The hot pressurized combustion gases cause a piston20adjacent to each combustion chamber12to move linearly within a cylinder26and convert pressure exerted by the gases into a rotating motion, which causes a shaft22to rotate. Further, the shaft22may be coupled to a load24, which is powered via rotation of the shaft22. For example, the load24may be any suitable device that may generate power via the rotational output of the system10, such as an electrical generator. Additionally, although the following discussion refers to air as the oxidant16, any suitable oxidant may be used with the disclosed embodiments. Similarly, the fuel18may be any suitable gaseous fuel, such as natural gas, associated petroleum gas, propane, biogas, sewage gas, landfill gas, coal mine gas, for example.

The system8disclosed herein may be adapted for use in stationary applications (e.g., in industrial power generating engines) or in mobile applications (e.g., in cars or aircraft). The engine10may be a two-stroke engine, three-stroke engine, four-stroke engine, five-stroke engine, or six-stroke engine. The engine10may also include any number of combustion chambers12, pistons20, and associated cylinders (e.g.,1-24). For example, in certain embodiments, the system8may include a large-scale industrial reciprocating engine having 4, 6, 8, 10, 16, 24 or more pistons20reciprocating in cylinders26. In some such cases, the cylinders26and/or the pistons20may have a diameter of between approximately 13.5-34 centimeters (cm). In some embodiments, the cylinders and/or the pistons20may have a diameter of between approximately 10-40 cm, 15-25 cm, or about 15 cm. The system10may generate power ranging from 10 kW to 10 MW. In some embodiments, the engine10may operate at less than approximately 1800 revolutions per minute (RPM). In some embodiments, the engine10may operate at less than approximately 2000 RPM, 1900 RPM, 1700 RPM, 1600 RPM, 1500 RPM, 1400 RPM, 1300 RPM, 1200 RPM, 1000 RPM, 900 RPM, or 750 RPM. In some embodiments, the engine10may operate between approximately 750-2000 RPM, 900-1800 RPM, or 1000-1600 RPM. In some embodiments, the engine10may operate at approximately 1800 RPM, 1500 RPM, 1200 RPM, 1000 RPM, or 900 RPM. Exemplary engines10may include General Electric Company's Jenbacher Engines (e.g., Jenbacher Type 2, Type 3, Type 4, Type 6 or J920 FleXtra) or Waukesha Engines (e.g., Waukesha VGF, VHP, APG, 275GL), for example.

The driven power generation system8may include one or more knock sensors23suitable for detecting engine “knock.” The knock sensors23may be any sensors configured to sense sounds or vibrations caused by the engine10, such as sound or vibration in the cylinders26of the engine10due to detonation, pre-ignition, and or pinging. The knock sensor23is shown communicatively coupled to an engine control unit (ECU)25. During operations, signals from the knock sensor(s)23are communicated to the ECU25to determine if knocking conditions (e.g., pinging) exist. The ECU25may then adjust certain engine10parameters to ameliorate or eliminate the knocking conditions. For example, the ECU25may adjust ignition timing and/or adjust boost pressure to eliminate the knocking. As further described herein, the knock sensor23may additionally derive that certain sounds or vibrations should be further analyzed and categorized to detect, for example, engine conditions (e.g., pre-ignition or pinging).

FIG. 2is a side cross-sectional view of an embodiment of a piston assembly25having a piston20disposed within a cylinder26(e.g., an engine cylinder) of the reciprocating engine10. The cylinder26has an inner annular wall28defining a cylindrical cavity30(e.g., bore). The piston20may be defined by an axial axis or direction34, a radial axis or direction36, and a circumferential axis or direction38. The piston20includes a top portion40(e.g., a top land). The top portion40generally blocks the fuel18and the air16, or a fuel-air mixture32, from escaping from the combustion chamber12during reciprocating motion of the piston20.

As shown, the piston20is attached to a crankshaft54via a connecting rod56and a pin58. The crankshaft54translates the reciprocating linear motion of the piston24into a rotating motion. As the piston20moves, the crankshaft54rotates to power the load24(shown inFIG. 1), as discussed above. As shown, the combustion chamber12is positioned adjacent to the top land40of the piston24. A fuel injector60provides the fuel18to the combustion chamber12, and an intake valve62controls the delivery of air16to the combustion chamber12. An exhaust valve64controls discharge of exhaust from the engine10. However, it should be understood that any suitable elements and/or techniques for providing fuel18and air16to the combustion chamber12and/or for discharging exhaust may be utilized, and in some embodiments, no fuel injection is used. In operation, combustion of the fuel18with the air16in the combustion chamber12cause the piston20to move in a reciprocating manner (e.g., back and forth) in the axial direction34within the cavity30of the cylinder26.

During operations, when the piston20is at the highest point in the cylinder26it is in a position called top dead center (TDC). When the piston20is at its lowest point in the cylinder26, it is in a position called bottom dead center (BDC). As the piston20moves from top to bottom or from bottom to top, the crankshaft54rotates one half of a revolution. Each movement of the piston20from top to bottom or from bottom to top is called a stroke, and engine10embodiments may include two-stroke engines, three-stroke engines, four-stroke engines, five-stroke engine, six-stroke engines, or more.

During engine10operations, a sequence including an intake process, a compression process, a power process, and an exhaust process occurs. The intake process enables a combustible mixture, such as fuel and air, to be pulled into the cylinder26, thus the intake valve62is open and the exhaust valve64is closed. The compression process compresses the combustible mixture into a smaller space, so both the intake valve62and the exhaust valve64are closed. The power process ignites the compressed fuel-air mixture, which may include a spark ignition through a spark plug system, and/or a compression ignition through compression heat. The resulting pressure from combustion then forces the piston20to BDC. The exhaust process typically returns the piston20to TDC while keeping the exhaust valve64open. The exhaust process thus expels the combusted fuel-air mixture (e.g., combustion gases) through the exhaust valve64. It is to be noted that more than one intake valve62and exhaust valve64may be used per cylinder26.

The depicted engine10also includes a crankshaft sensor66, the knock sensor23, and the engine control unit (ECU)25, which includes a processor72and memory74. The crankshaft sensor66senses the position and/or rotational speed of the crankshaft54. Accordingly, a crank angle or crank timing information may be derived. That is, when monitoring combustion engines, timing is frequently expressed in terms of crankshaft54angle, which is correlative to time. For example, a full cycle of a four stroke engine10may be measured as a 720° cycle over a period of time. The knock sensor23may include one or more of a Piezo-electric accelerometer, a microelectromechanical system (MEMS) sensor, a Hall effect sensor, a magnetostrictive sensor, and/or any other sensor designed to sense vibration, acceleration, sound, and/or movement. In other embodiments, sensor23may not be a knock sensor in the traditional sense, but any sensor that may sense vibration, pressure, acceleration, deflection, or movement, and may not be used to detect engine “knock.”

Because of the percussive nature of the engine10, the knock sensor23may be capable of detecting signatures even when mounted on the exterior of the cylinder26. However, the knock sensor(s)23may be disposed at various locations in or about each cylinder26. Additionally, in some embodiments, a single knock sensor23may be shared, for example, with one or more adjacent cylinders26. In other embodiments, each cylinder26may include one or more knock sensors23. The crankshaft sensor66and the knock sensor23are shown in electronic communication with the engine control unit (ECU)25. The ECU25includes the processor72and the memory74. The memory74may store computer instructions that may be executed by the processor72. The ECU25monitors and controls and operation of the engine10, for example, by adjusting combustion timing, valve62,64, timing, adjusting the delivery of fuel and oxidant (e.g., air), and so on.

Advantageously, the techniques described herein may use the ECU25to receive data from the knock sensor23. The ECU25may then go through the process of analyzing the data to determine operating conditions of the engine10. For example, the ECU25may characterize the data received from the knock sensor23, as described in more detail below. By providing for signature analysis, the techniques described herein may enable a more optimal and a more efficient operation and maintenance of the engine10.

In accordance with present embodiments, the knock sensor23, in particular, may be utilized to detect vibrations, sound, or acceleration associated with movement of the piston20within the cylinder26. The profile (e.g., vibration profile, acoustic profile, or both) detected by the knock sensor23may be converted by the knock sensor23or by the ECU25into a parameter indicative of pressures within the cylinder26(e.g., including the peak firing pressure or compression ratio). The parameter indicative of pressure (e.g., including the peak firing pressure or compression ratio) may be analyzed by the ECU25via control logic implemented on the ECU25to determine peak firing pressure (e.g., the maximum pressure value in the profile), and to determine if the peak firing pressure has increased beyond a desirable amount, which may indicate pre-ignition conditions, as explained above, or may indicate (e.g., predict) that the engine10is approaching pre-ignition conditions. It should be noted that the description of vibration herein is intended to also cover acoustic measurements, light measurements, acceleration measurements, or a combination thereof, or any other suitable measurement(s).

For example, a flow diagram of an embodiment of a process200suitable for detecting a change (e.g., a rise) in peak firing pressure in the reciprocating engine10is shown inFIG. 3. The process200may be implemented as computer code or executable instructions stored in the memory74and executable via the processor72. In the illustrated embodiment, the process200includes determining a baseline value Xb, where X is a value of a parameter indicative of peak firing pressure (block202). The baseline value Xbof the parameter indicative of peak firing pressure may be determined from data received from the knock sensor23(and in some embodiments, only from data received from the knock sensor23), and may be associated with any of the following: 1) a position of the piston20within the cylinder26; 2) a speed of the piston20within the cylinder26; 3) an acceleration of the piston20within the cylinder26; 4) a pressure within the cylinder26; or 5) a combination thereof. Further, the baseline value Xbmay be measured (e.g., detected, deduced, determined, or estimated) at a particular moment in time when the engine10is operating, e.g., at the time the ignition mechanism (e.g., spark plug) ignites the fuel-air mixture to generate the hot combustion gases. Alternatively, the baseline value Xbmay be a maximum value detected over a period of time (e.g., over one stroke of the piston20within the cylinder26), or deduced from values detected over the period of time (e.g., by determining the maximum value). For example, in some embodiments, Xbmay be determined by analyzing only the data provided by the knock sensor23(e.g., vibrations or sound within the cylinder26).

The baseline value Xbis generally deduced by the ECU25from a vibrational profile measured by the knock sensor23(where the vibrations correspond with, e.g., pressures in the cylinder26), as described below. For example, the knock sensor23detects vibrations in the cylinder26and communicates the vibrations to the ECU25via a signal for processing. The vibrations may be indicative of a range of various pressures (or of parameters related to pressure) within the cylinder26, and the knock sensor23may detect the vibrations indicative of the range of various pressures (or parameters related to pressure) over, for example, a period of time The ECU25may evaluate the range of pressures (or the range of the parameter related to pressure) to determine peak firing pressure (e.g., the highest pressure). In other words, in some embodiments, the ECU25may determine the peak firing pressure (or parameter indicative of peak firing pressure) by analyzing only data received from the knock sensor23(e.g., without analyzing data received from the crankshaft sensor66).

The knock sensor23may detect the vibrations during a baselining process in a factory (e.g., before the engine10is operating in normal conditions), thereby enabling the baseline value Xbto reflect factory performance (e.g., ideal performance) of the engine10. After receiving the signal from the knock sensor23(e.g., the signal indicative of the vibrations detected by the knock sensor23), the ECU25may process the signal to deduce the baseline value Xbof the parameter indicative of peak firing pressure (e.g., in accordance with the description above) from the vibrations detected by the knock sensor23and transmitted, via the signal, to the ECU25. It should be noted, however, that the knock sensor23, in some embodiments, may deduce and convert the detected vibrations to the baseline value Xbdirectly, and communicate the baseline value Xbto the ECU25, via a signal, for further processing.

In either embodiment, the process200also includes deriving a cutoff factor F of the parameter indicative of peak firing pressure (block204). The cutoff factor F an added value added to the baseline value Xbof the parameter indicative of peak firing pressure to derive an appropriate range of operating peak firing pressures that the engine10may experience under normal conditions. In some embodiments, the cutoff factor F may be a multiplier (e.g., 1.01Xb, 1.1Xb, 1.2Xb, 1.3Xb, and so on and so forth). Generally, the operating peak firing pressure of an operating cylinder26or cylinders26of the engine10may fluctuate slightly (e.g., within the cutoff factor F) over time due to a number of different factors. For example, external temperature may affect operating conditions of the engine10and, thus, may affect the operating peak firing pressure within the cylinder26of the engine10. Additionally, the peak firing pressure may fluctuate slightly as a normal (e.g., small) amount of oil or other contaminants have created coke or other deposits on the inside of the cylinder26. However, if operating peak firing pressure exceeds the baseline value Xbplus the cutoff factor F, the engine10may be operating with excess peak firing pressure, indicating that operating conditions are not ideal (e.g., abnormal or large amounts of oil or other contaminants have created undesired coating on the inside of the cylinder26). Operating peak firing pressures exceeding a baseline peak firing pressure plus a cutoff factor of the baseline peak firing pressure may reduce an efficiency of the engine10, and may indicate that pre-ignition conditions are occurring or about to occur.

To determine if operating peak firing pressures are too high (e.g., outside the appropriate range), the ECU25may instruct the knock sensor23to measure (e.g., detect) vibrations of the cylinder26during operation of the engine10. The knock sensor23may transmit the vibrational profile to the ECU25via one or more signals, as previously described, and the ECU25may deduce from the signal(s) a first operating value Xtiof the parameter indicative of peak firing pressure at time ti(block206). In some embodiments, as previously described, the knock sensor23directly converts the vibration measurements taken by the knock sensor23and deduces the first operating value Xtiof the parameter indicative of peak firing pressure, and communicates the first operating value Xtito the ECU25via a signal.

The ECU25then compares the first operating value Xtiwith the baseline value Xband the cutoff factor F to determine if a change (e.g., a rise or fall) in peak firing pressure has occurred (block208). For example, if the ECU25determines that the first operating value Xtiof the parameter indicative of peak firing pressure is less than the baseline value Xbof the parameter indicative of peak firing pressure plus the cutoff factor F, the peak firing pressure has not risen beyond the appropriate range (e.g., defined by the cutoff factor F) and the process200repeats starting with block206.

However, if the ECU25determines that the first operating value Xtiof the parameter indicative of peak firing pressure is greater than the baseline value Xbof the parameter indicative of peak firing pressure plus the cutoff factor F, a substantial rise in peak firing pressure has been detected in the cylinder26. To confirm the increase in peak firing pressure, the process200includes determining a second operating value Xtiiof the parameter indicative of peak firing pressure using the knock sensor23at time tii(block210). For example, the ECU25instructs the knock sensor23to detect or measure vibrations of the piston20and/or cylinder26. The second measurement (e.g., vibrational profile) by the knock sensor23is derived (e.g., via conversion from the vibration profile to the second operative value Xtii) in the same manner as the first measurement, but after the first measurement. The ECU25then compares the second operating value Xtiiwith the baseline value Xbplus the cutoff factor F (block212). For example, the ECU25determines if the second operating value Xtiiof the parameter indicative of peak firing pressure is less than or greater than the baseline value Xbplus the cutoff factor F. If the second operating value Xtiiis greater than the baseline value Xbplus the cutoff factor F, the rise in peak firing pressure in the cylinder26is confirmed (block214). Once the rise in peak firing pressure is confirmed in accordance with the above description, the engine10may automatically shut off, the offending cylinder26of the engine10may be shut off, or the ECU25may indicate the rise in peak firing pressure to an operator. For example, the ECU25may instruct a light, a sound, a gauge, or some other signal to activate upon confirmation of the rise in peak firing pressure.

In some embodiments, it may be beneficial to use other control logic implemented on the ECU25, based on the same measurements described in the process200, to determine rises in peak firing pressure during operation of the engine10. For example, a process flow diagram of an embodiment of a process300suitable for detecting incremental rises in peak firing pressure in the reciprocating engine10is shown inFIG. 4.

In the illustrated embodiment ofFIG. 4, blocks302,304,306,308, and310of the process300may correspond with blocks202,204,206,208, and210of the process200ofFIG. 3described above. The process300may be implemented as computer code or executable instructions stored in the memory74and executable via the processor72. For example, if the first operating value Xtiof the parameter indicative of peak firing pressure detected by the knock sensor23at time ti(e.g., directly or indirectly detected, as set forth above) is greater than the baseline value Xbplus the cutoff factor F (e.g., as determined by the ECU25), the second operating value Xtiiof the parameter indicative of peak firing pressure is detected at time tiiand deduced by the knock sensor23and the ECU25(e.g., directly or indirectly detected, as set forth above). However, in the process300ofFIG. 4, the second operating value Xtiiis compared, via the ECU25, directly with the first operating value Xti(block312). If the second operating value Xtiiis greater than the first operating value Xti, the rise in peak firing pressure is confirmed (block314). Further, the rise in peak firing pressure may be considered an incremental rise (e.g., a series of rises), in that the first operating value Xtiindicated a rise over the baseline value Xbplus cutoff factor F, and the second operating value Xtiiindicates a rise over even the first operating value Xti. Incremental rises (e.g., rises in a series) may indicate that the peak firing pressure is rising quickly and/or consistently. Accordingly, the engine10may be shutoff (e.g., by the ECU25), one or more cylinders26of the engine10may be shut off (e.g., by the ECU25), the ECU25may initiate a corrective action to remedy the change (e.g., rise) in peak firing pressure, and/or the ECU25may indicate the quick and/or consistent rise in peak firing pressure to the operator. For a series of incremental rises in peak firing pressure, the response by the engine10may, in some embodiments, be more substantial (e.g., engine shut down) than detecting and confirming a single rise in peak firing pressure as described with reference to process200.

In still further embodiments, it may be beneficial to combine various control logic implemented on the ECU25and described above for robust detection of rises or changes in peak firing pressure. In other words, it may be beneficial to confirm that the peak firing pressure has risen above the cutoff threshold (e.g., as defined by the baseline value and the cutoff factor F) via comparison of the cutoff threshold with multiple data points measures (e.g., detected) by the knock sensor, in addition to comparing the multiple data points (e.g., Xtiand Xtii) with each other. For example, a process flow diagram of an embodiment of a process400of confirming an increase in peak firing pressure in addition to detecting incremental rises in peak firing pressure is shown inFIG. 5.

In the illustrated embodiment, blocks402,404,406,408,410, and412may correspond with blocks202,204,206,208,210, and212of the process200ofFIG. 3described above. Further, block414may correspond with block312in the process300ofFIG. 4. For example, process400may correspond with process200through blocks212and412, respectively. The process400may be implemented as computer code or executable instructions stored in the memory74and executable via the processor72.

After the ECU25(e.g., controller) confirms that the peak firing pressure has risen by comparing the second operating value Xtiiwith the baseline value XBplus the cutoff factor F (block412), a range of pressures including the second operating value Xtiiis detected (via vibration detection by the knock sensor23), deduced (via conversion of the vibration to the second operating value Xtiiof the parameter indicative of peak firing pressure), and compared with the first operating value Xti, as described with reference to process300(block414). If the second operating value Xtiiexceeds the first operating value Xti, an incremental rise (e.g., a series of rises) is confirmed (block416). If the second operating value Xtiidoes not exceed the first operating value Xti, the incremental rise or series of rises is not confirmed, but the rise in peak firing over the baseline value XBplus cutoff factor F (e.g., from block412) is confirmed (block418). As previously described, the response of the engine10to the two conditions in blocks416and418may be different. For example, if the peak firing pressure has risen incrementally or in a series, as described in block416, the engine10may shut down, a remedial control action may be initiated by the ECU25, or the ECU25may alert an operator with a first indicator (e.g., viewable gauge, lights, audible horn, and so on). If the peak firing pressure has not rise incrementally or in a series, but has been confirmed above the baseline value XBplus cutoff factor F, as described in block418, the engine10may alert the operator with a second indicator that indicates a less substantial problem than the first indicator.

In still other embodiments, it may be beneficial to compare results, via the ECU25, of multiple cylinders26across the engine10. Comparing the results may be beneficial, e.g., in determining causes of a change (e.g., rise) in peak firing pressure. For example, a flow diagram of an embodiment of a process500suitable for detecting a local or global rise in peak firing pressure across one or more cylinders26of the reciprocating engine10ofFIG. 1is shown inFIG. 6. In the illustrated embodiment, blocks502and504correspond with blocks202and204inFIG. 3. The process500also includes determining the operating value Xtiat a first time tiusing knock sensors23for each cylinder26of the engine10(e.g., where the engine10includes multiple cylinders26), in accordance with the descriptions above (block506). Each operating value Xtimay be stored in an array of operating values Xtifor the specified time ti. The process500also includes determining, for each cylinder26, if Xtiis greater than the baseline value XBplus the cutoff factor F (block508) to determine a change (e.g., rise) in peak firing pressure. A separate array may be generated indicating which cylinders26included changes (e.g. rises) over the baseline value XB. Although not shown in the illustrated embodiment, it should be noted that second operating values Xtiimay be determined in accordance with previous descriptions to confirm the change (e.g., rise) in peak firing pressures.

After changes (e.g., rises) in peak firing pressure are determined or confirmed for various ones of the cylinders26of the engine10, the ECU25may determine a ratio R of the total number of changes (e.g., rises) in peak firing pressure across the plurality of cylinders26(or, put differently, the total number of cylinders26in which changes [e.g., rises] in peak firing pressure were detected or confirmed) divided by the total number of cylinders26in the engine10(or the total number of cylinders26tested via the process500) (block510). A cutoff ratio Rcmay also be derived (e.g, by the ECU25) (block512). The ratio R may be compared with the cutoff ratio Rcto determine if the ratio R is larger than or smaller than the cutoff ratio Rc(block514).

If the ratio R is larger than the cutoff ratio Rc, the ECU25may confirm that the change(s) (e.g., rise(s)) in peak firing pressure(s) are a global concern of the engine10(block516). If the ratio R is not larger than (e.g., equal to or less than) the ratio cutoff Rc, the ECU25may confirm that the change(s) (e.g., rise(s)) in peak firing pressure(s) are a local concern of the offending cylinders26(block518). For example, a global concern may indicate that a condition affecting all (or a larger enough number) of the cylinders26may be causing the rises in peak firing pressure. Global concerns may include, but are not limited to, problems with a fuel being supplied to the cylinders26. A local concern may indicate that a condition affecting one or a small subset of the cylinders26may be causing the rises in peak firing pressure. Local concerns may include, but are not limited to, defects in the offending cylinder(s)26. The ECU25may employ different responses to local and global concerns. For example, the ECU25may shut off the entire engine10if a global concern is detected, but may only alert an operator if local concerns are detected.

In general, systems and methods in accordance with the present disclosure detect changes (e.g., rises) in peak firing pressure (or compression ratio) of a reciprocating engine to determine if the engine is approaching or has reached pre-ignition (e.g., engine knocking) conditions. The systems and methods utilize detection of vibrations of a cylinder of the engine or of a piston with the cylinder, conversion of the vibration profiles (e.g., graphs) to one or more values indicative of peak firing pressure, and comparison of the values with each other or with a baseline value to determine rises in peak firing pressure (or compression ratio). By implementing various control logic on a controller (e.g., engine control unit (ECU)) and utilizing the control logic to compare the various values detected by the knock sensor, pre-ignition conditions or potential pre-ignition conditions can be communicated to an operator, such that the operator may intervene and remedy the problem.