Systems and procedures for diagnosing an engine

Abstract

A method for a reciprocating engine (110) functionally connected to a generator (120), comprising the step of diagnosing the state of the engine (110) by comparing an estimated engine torque profile generated by combustion in the engine (110) with an expected engine torque profile, wherein the estimated engine torque profile generated by combustion in the engine (110) is derived from an electromagnetic torque of the generator (120) and an inertial torque of the reciprocating engine (110), and wherein the electromagnetic torque is derived from at least one electrical parameter associated with the generator (120), characterized in that the at least one electrical parameter is derived from at least one of the voltages of a DC link (171), a current of a DC link (171), a field voltage of the generator (120), or a field current of the generator (120).includes an output voltage of the generator (120) and an output current of the generator (120).

Description

AREA

[0001] Embodiments of the subject matter described herein relate to systems and methods for diagnosing an engine. BACKGROUND

[0002] Engine components can deteriorate in various ways during operation. For example, an engine cylinder in an engine may begin misfiring due to a worn spark plug. One way to detect engine deterioration is by monitoring engine speed. Diagnostic routines can monitor whether engine speed contributions rise above a threshold and generate diagnostic codes or other indications that require service, reduction in engine power, or engine shutdown. However, the inventors herein have recognized that engine speed analysis is often insufficient to thoroughly diagnose an engine problem.

[0003] The following is known from the state of the art: US 2011 / 0 153 128 A1 determines a net torque of a motor depending on a generator. US 5 461 289 A uses a control unit to record a torque curve of an engine as a function of the current of the generator arrangement as a function of the instantaneous angular position of the crankshaft and diagnoses operating errors and / or the condition of the engine as a function of the torque curve. EP 1 143 134 A1 records a reaction torque of a motor generator that functions as an engine in a car. US 5 056 487 A compares a torque curve for an irregular combustion condition with a torque curve for a normal combustion condition of an engine.

[0004] The task is to improve the analysis of engine speed.

[0005] This object is achieved by the features of the independent patent claims. Advantageous developments of the invention are described in the subclaims.

[0006] In one embodiment, a method for a reciprocating engine operatively connected to a generator is described. The method includes diagnosing a condition of the engine by comparing an estimated combustion-induced engine torque profile with an expected engine torque profile.

[0007] In one embodiment, a method for a reciprocating engine operatively connected to a generator is described. The method includes diagnosing an in-cylinder pressure profile of the engine by comparing an estimated combustion-induced engine torque profile with an expected engine torque profile.

[0008] In one embodiment, a vehicle system is described. The vehicle system includes an engine, a generator operatively connected to the engine, at least one sensor for measuring at least one electrical parameter associated with the generator during operation, a sensor for measuring the speed of a rotating shaft of the engine, and a controller. The controller includes instructions configured to sample and transform at least one electrical parameter into an electromagnetic torque profile, to sample and transform the speed of the rotating shaft into an inertial torque profile, and to estimate a combustion-induced engine torque profile from the electromagnetic torque profile and the inertial torque profile.

[0009] In one embodiment, a test kit is provided. The test kit includes a controller operable to determine a state of a reciprocating engine operatively connected to a generator based on a comparison of an estimated combustion-induced engine torque profile with an expected engine torque profile.

[0010] This brief description of the invention is provided to introduce a selection of concepts in a simplified form that are further described herein. This brief description is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all of the disadvantages identified in any part of this description. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The invention will be understood by reading the following description of non-limiting examples with reference to the accompanying drawings, in which: Fig. 1 is an illustration of an example embodiment of a vehicle system (e.g., a locomotive system) having an engine and a generator (alternator), depicted herein as a rail vehicle configured to travel on rails by means of a plurality of wheels; Fig. 2 an illustration of an example embodiment of the engine and generator functionally connected to various auxiliary units and traction motors of Fig. 1 is; Fig. 3 is an illustration of an example embodiment of how to estimate a combustion-induced engine torque profile from engine speed and generator electrical parameters; Fig. 4 is an illustration of an example embodiment of how to convert electrical parameters of the generator into an electromagnetic torque profile; Fig. 5 is an illustration of an example embodiment of how to generate an inertia torque profile from the speed of the motor; Fig. 6 is an illustration of an example embodiment of how the combustion-induced engine torque profile is estimated; Fig. 7 is an illustration of an example embodiment of how a torque comparison process is used to diagnose a condition of an engine; and Fig. Figure 8 is an illustration of example embodiments of how to generate the frequency content of a time-domain torque profile that can be used for engine diagnostics. DETAILED DESCRIPTION

[0012] Embodiments of the subject matter described herein relate to systems and methods for diagnosing an engine. Test kits for performing the methods are also provided. The engine may be included in a vehicle, such as a locomotive system. Other suitable types of vehicles may include on-road vehicles, off-road vehicles, mining equipment, aircraft, and ships. Further embodiments of the invention may be used for stationary engines, such as wind turbines or power generators. The engine may be a diesel engine or may burn another fuel or a combination of fuels. Such alternative fuels may include gasoline, kerosene, biodiesel, natural gas, and ethanol, as well as combinations of the foregoing. Suitable engines may utilize compression and / or spark ignition. These vehicles may include an engine with components that deteriorate with use.

[0013] Furthermore, embodiments of the subject matter described herein use generator data, such as measured electrical parameters of the generator or generator data derived from the measured electrical parameters (e.g., a derived torque profile) and / or engine parameters (e.g., speed) to diagnose conditions of an engine and to distinguish between conditions and associated engine components.

[0014] An engine may be placed into a specific operating condition or mode when looking for specific types of engine degradation. For example, the engine may be diagnosed during a self-load condition as part of a test procedure, a dynamic brake (dB) test bench condition, or a steady-state monitoring condition. The diagnostic and prognostic techniques discussed herein can be used for trend tracking, cylinder-to-cylinder variation comparison, performance of test procedures, repair confirmation, and repair support. Alternatively, generator and / or motor data may be sampled and analyzed when the engine reaches a specific operating condition or status during normal operation.

[0015] Fig. 1 is an illustration of an example embodiment of a vehicle system 100 (e.g., a locomotive system), depicted herein as a rail vehicle 106 configured to travel on a rail 102 by means of a plurality of wheels 108. As depicted, the rail vehicle 106 includes an engine 110 operatively connected to a generator (alternator) 120. The vehicle 106 also includes traction motors 130 operatively connected to the generator 120 for driving the wheels 108. The vehicle 106 further includes various traction motors 130 operatively connected to the generator 120 or the engine 110 (e.g., the rotatable motor shaft 111, see Fig. 2) auxiliary systems or units connected to perform various functions 140.

[0016] The vehicle 106 further includes a controller 150 for controlling various components associated with the vehicle system 100. In one example, the controller 150 includes a computer control system. In one embodiment, the computer control system is largely software-based and includes a processor, such as processor 512, configured to execute computer-executable instructions. The controller 150 may include multiple engine control units (ECUs), and the controller system may be distributed among each of the ECUs. The controller 150 further includes computer-readable storage media, such as a memory 154, with instructions (e.g., computer-executable instructions) to enable on-board monitoring and control of the rail vehicle operation. The memory 154 may include a volatile and a non-volatile memory area.According to another embodiment, the control device may be hardware-based, for example, using digital signal processors (DSPs) or other hardware logic circuitry to perform the various functions described herein.

[0017] The controller may monitor the control and management of the vehicle system 100. The controller may receive a signal from an engine speed sensor 160 or from various generator sensors 170 to determine operating parameters and operating conditions and adjust various engine actuators 162 accordingly to control the operation of the rail vehicle 106. According to one embodiment, the speed sensor includes a multi-tooth pickup wheel connected to the motor shaft 111 and a reluctance sensor for measuring when a tooth of the pickup wheel passes the reluctance sensor. For example, the controller may receive signals representing various generator parameters from various generator sensors.The generator parameters may include a DC link voltage, a DC link current, a generator field voltage, a generator field current, a generator output voltage, and a generator output current. Additional generator parameters may also be possible according to various embodiments. Accordingly, the controller may control the vehicle system by sending commands to various components such as traction motors, the alternator, cylinder valves, throttle valve, etc. Signals from the generator sensors 170 may be bundled into one or more wiring harnesses to reduce the space allocated for wiring in the vehicle system 100 and to protect the signal wires from abrasion and vibration.

[0018] The control device may include on-board electronic diagnostics for recording operating characteristics of the engine. Operating characteristics may include, for example, measurements from sensors 160 and 170. In one embodiment, the operating characteristics may be stored in a database in memory 154. In one embodiment, current operating characteristics may be compared to previous operating characteristics to determine trends in engine behavior.

[0019] The controller may include on-board electronic diagnostics for identifying and recording potential degradation and failures of components of the vehicle system 100. For example, when a potentially degraded component is identified, a diagnostic code may be stored in memory 154. In one embodiment, a unique diagnostic code may correspond to each type of degradation that can be identified by the controller. For example, a first diagnostic code may indicate a problem with cylinder 1 of the engine, and a second diagnostic code may indicate a problem with cylinder 2 of the engine.

[0020] The control device may be further linked to a display device 180, such as a diagnostic interface display device, that provides a user interface for the locomotive operating and maintenance crews. The control device may control the engine in response to user input via user input controls 182 by sending a command to adjust various engine actuators 162 accordingly. Non-limiting examples of user input controls 182 may include a throttle control device, a brake control device, a keypad, and a power switch. Furthermore, operating characteristics of the engine, such as diagnostic codes corresponding to degraded components, may be reported to the operating and / or maintenance crews via the display device 180.

[0021] The vehicle system may include a communications system 190 connected to the control device. In one embodiment, the communications system 190 may include a radio device and an antenna for sending and receiving voice and data messages. For example, data communication may occur between the vehicle system and a control center of a railroad company, another locomotive, a satellite, and / or a wayside device such as a rail switch. For example, the control device may estimate geographical coordinates of the vehicle system using signals from a GPS receiver. As another example, the control device may transmit operating characteristics of the engine to the control center via a message sent from the communications system 190.In one embodiment, a message may be transmitted through the communication system 190 to the command center when a degraded component of the engine is detected and the vehicle system may be scheduled for maintenance.

[0022] Fig. Figure 2 is an illustration of an example embodiment of the engine 110 and the generator 120 of Figure 10 operatively connected to various auxiliary units 140 (141, 142, 143, 144) and to the traction motors 130. Fig. 1. The various mechanical auxiliaries 144 may be operatively connected to and driven by the rotating motor shaft 111. Further auxiliaries 140 are driven by the generator 120 via a rectifier 210, which generates a DC link voltage for power regulator 230. Examples of such auxiliaries include a fan 141, a compressor 142, and a radiator fan 143. The traction motors 130 are driven by the generator 120 via the rectifier 210, which generates a DC link voltage at an inverter 220. Such auxiliaries 140, traction motors 130, and their implementations are well known in the art. According to certain embodiments, the generator 120 may actually be just one or more generators, such as: B. a main generator for driving the traction motors 130 and an auxiliary generator for operating part of the auxiliary units 140.Further examples of auxiliary units include turbochargers, pumps and engine cooling systems.

[0023] The speed sensor 160 measures the speed of the rotating shaft 111 of the motor during operation. The DC link sensor 171 is a generator sensor and can measure a DC link voltage, a DC link current, or both according to various embodiments. The field sensor 172 is a generator sensor and can measure the generator field current, the generator field voltage, or both according to various embodiments. According to various embodiments, generator sensors 173 and 174 are provided for measuring the armature output voltage and the generator current, respectively. Suitable commercially available sensors can be selected based on application-specific parameters.

[0024] According to various embodiments, the control device 150 may be operated to report a degraded engine condition, for example, via the communication system 190. Furthermore, according to various embodiments, the control device includes instructions configured to adjust an engine operating parameter based on the diagnosed condition.

[0025] Fig. 3 is an illustration of an example embodiment of a method 300 for estimating a combustion torque profile of an engine from engine speed and generator electrical parameters. In step 310, the engine speed signal is sampled by controller 150 (e.g., using speed sensor 160). In step 320, the engine's inertial torque profile is estimated from the engine speed. In step 330, a generator current and / or voltage are sampled by controller 150 (e.g., using generator sensors 170). In step 340, the sampled current and / or voltage are passed through an alternator model. In step 350, an electromagnetic torque profile of the alternator is estimated from the output of the alternator model.In step 360, the inertial torque profile is modified using the electromagnetic torque profile to generate a combustion torque profile of the engine. In step 370, the combustion torque profile is compared to an output characteristic or expected engine torque profile.

[0026] Fig. Figure 4 is an illustration of an example embodiment of how to convert electrical parameters of the generator into an electromagnetic torque profile. A DC link voltage and a generator field current (e.g., measured by generator sensors 171 and 172) are fed into a three-phase generator model 410 implemented in the controller 150, which includes a reverse model 420 of a rectifier 210 and a model 430 of a generator 120. The rectifier may be a diode rectifier, a phase-controlled rectifier, or a pulse-width modulation (PWM) rectifier according to various embodiments. According to an alternative embodiment, instead of a rectifier, an AC load may be connected and modeled in reverse, directly or indirectly via controlled power electronics devices.

[0027] The reverse model 420 estimates the generator output voltage from the DC link voltage. Likewise, the generator model 430 estimates the generator output current from the field current. The generator output current and voltage are fed into an electromagnetic torque estimation process 440 implemented in the controller 150. The electromagnetic torque estimation process 440 uses the generator output voltage and current along with an indication of the motor speed to estimate an electromagnetic torque profile. An indication of the motor speed is used to tell the torque estimation model 440 where the harmonic frequencies of interest are located. The motor speed from the speed sensor 160 can be used as an input signal, or the frequency content (e.g., the sixth harmonic) from the rectifier 210 (e.g.,the frequency content of the DC link voltage signal) can be used as an indication of the motor speed.

[0028] Accordingly, an electromagnetic torque profile associated with the generator can be derived from the DC link voltage and the generator field current. Alternatively, the DC link current and the generator field voltage could be used with appropriate models to estimate the generator output current from the DC link current and the generator output voltage from the generator field voltage. If the generator output voltage and current are already available to the controller 150 (due to such sensors on the generator), the reverse model 420 and the generator model 430 can be bypassed. Furthermore, if a less accurate estimation of the torque profile is acceptable, only one of the parameters (DC link voltage, generator field current, generator field voltage, generator output current, generator output voltage) can be used instead of both to estimate a torque profile.

[0029] In one embodiment, the controller implements an inertia torque estimation process. Fig. 5 is an illustration of an example embodiment of how to generate an inertial torque profile from the engine speed using an inertial torque profile estimation process 510 of the controller 150. The engine inertial torque profile may be estimated from the engine speed by sampling the measured engine speed (e.g., from speed sensor 160) over time, deriving acceleration components (considering the derivative of the speed with respect to time) from the measured speed at predetermined characteristic frequencies, and combining the acceleration components to determine the inertial torque profile.

[0030] Fig. Figure 6 is an illustration of an example embodiment of how a combustion torque profile of the engine is estimated. The controller 150 implements a motor torque estimation process 610 that compensates the electromagnetic torque profile of the generator with the inertial torque profile of the motor with the given speed fluctuations to obtain an accurate combustion torque profile at the engine end. As shown in Fig. 7, the controller 150 implements a torque profile comparison process 710 to compare the estimated combustion torque profile of the engine with an expected measurement baseline torque profile. In one embodiment, a template comparison or signature comparison algorithm is used to perform the comparison. A particular deviation from a measurement baseline torque profile may correspond to a particular degradation of an engine component (e.g., which power assembly component of the engine has failed). According to one embodiment, the estimated combustion torque profile is indicative of an in-cylinder pressure profile of the engine. Therefore, the method 300 enables accurate prediction of in-cylinder pressure profiles of engines using existing engine and generator sensors.

[0031] According to one embodiment, the reciprocating engine may first be brought into a specified operating state or mode before executing the combustion torque estimation process 300. According to another embodiment, the combustion torque estimation process 300 is not executed until the engine reaches a predetermined operating state, status, or mode during normal operation, triggering the controller to perform the torque estimation process and a subsequent comparison of the estimated torque profile with the measured baseline torque profile.

[0032] According to various embodiments, the control device 150 may be operated to report a degraded engine condition, for example, via the communication system 190. Furthermore, according to various embodiments, the control device includes instructions configured to adjust an engine operating parameter based on the diagnosed condition.

[0033] A test kit may be provided which includes a controller operable to determine a condition of a reciprocating engine operatively connected to a generator based on a comparison of an estimated combustion torque profile of an engine with an expected engine torque profile. The kit also includes at least one sensor to measure at least one electromagnetic parameter (e.g., the DC link voltage and / or generator field current) associated with the generator. The controller is operable to communicate with the sensors and sample the electromagnetic parameter over time. The controller is also operable to estimate an electromagnetic torque profile from the electromagnetic parameters. The kit may further include a sensor for measuring a shaft speed of the reciprocating engine.The control device may be operable to communicate with the sensor to sample the shaft speed over time. The control device may further be operable to estimate an inertial torque profile from the shaft speed. The control device may also be operable to estimate the estimated combustion torque profile of the engine from the electromagnetic torque profile and the inertial torque profile.

[0034] Further examples of applications of the systems and methods described herein are now provided. The examples illustrate various approaches for diagnosing and distinguishing between different types of engine degradation based on an engine's combustion torque profile estimated from generator parameters and engine speed.

[0035] The engine may contain multiple cylinders that fire in a predetermined sequence, with each cylinder firing once during a four-stroke or two-stroke cycle. For example, a four-cylinder, four-stroke engine may have a firing sequence of 1-3-4-2, with each cylinder firing once for every two engine revolutions. Thus, the firing frequency of a given cylinder is one-half of the engine's rotational frequency, and the firing frequency of all cylinders is twice the engine's rotational frequency. The engine's rotational frequency may be described as the first engine order. Such a first-order frequency component may appear in the frequency content of the measured generator parameter. The firing frequency of a given cylinder of a four-stroke engine may be described as half the engine order, where the half engine order is one-half of the engine's rotational frequency.Such a half-order frequency component may appear in the frequency content of the measured generator parameter.

[0036] Another example of a four-stroke engine, a twelve-cylinder engine, may have a firing sequence of 1 - 7 - 5 - 11 - 3 - 9 - 6 - 12 - 2 - 8 - 4 - 10, with each cylinder firing once for every two engine revolutions. Thus, the firing frequency of a given cylinder is one-half of the engine's rotation frequency, and the firing frequency of all cylinders is six times the engine's rotation frequency. As an example of a two-stroke engine, a twelve-cylinder engine may have a firing sequence of 1 - 7 - 5 - 11 - 3 - 9 - 6 - 12 - 2 - 8 - 4 - 10, with each cylinder firing once for every engine revolution. Thus, the firing frequency of a given cylinder is the engine's rotation frequency, and the firing frequency of any cylinder is twelve times the engine's rotation frequency. Again, these frequency components may appear in the frequency content of the measured generator parameter.

[0037] For example, the engine may be a four-stroke engine operating at 1050 rpm. Thus, the first motor order is at 17.5 Hz and the half motor order is at 8.75 Hz. The DC link voltage may change at a periodic frequency as the motor shaft 111 rotates during operation. For example, the frequency content of the DC link voltage may contain a frequency component at the first motor order frequency. In other words, the peak magnitude of the frequency content may appear at the first order frequency component. The DC link voltage may also contain frequency content at other harmonics of the first order frequency, such as a second order frequency (twice the motor frequency), a third order frequency (triple the motor frequency), etc. Likewise, the DC link voltage may contain frequency content at frequencies lower than the first order frequency, such asat half order frequency (half motor frequency).

[0038] In one embodiment, a degraded cylinder of a four-stroke engine may be detected based on a comparison of the estimated combustion torque profile of the engine with an expected or measured baseline torque profile of the engine. Detecting a degraded cylinder where the other cylinders of the engine are better (or less degraded) may have a more consistent torque profile than if multiple cylinders of the engine are degraded. For example, a degraded cylinder may be identified by comparing a portion of the estimated combustion torque profile with the same portion of a measured baseline torque profile. However, multiple degraded cylinders may cause deviations in multiple portions of the combustion torque profile.Furthermore, the firing order position of multiple degraded cylinders may alter the portions of the estimated combustion torque profile that deviate from the baseline measurement torque profile. For example, two degraded cylinders 180 degrees out of phase may affect different portions of the torque profile than two degraded cylinders in consecutive firing order, and thus, the methods disclosed herein may identify one or more degraded cylinders based on various changes in the estimated torque profile. Anomalies that do not match the baseline measurement torque profile of a healthy engine, or another degraded engine component, may be identified and reported by the controller.Other examples of deteriorated engine components include a deteriorated crankcase ventilation system, a deteriorated turbocharger, and a deteriorated crankcase.

[0039] In one embodiment, the time-domain generator data (e.g., the DC link voltage and the field current) may be filtered through a low-pass filter with a cutoff frequency slightly higher than the motor's first-order frequency. For example, the cutoff frequency may be 10 to 20 percent higher than the first-order frequency. Thus, in one embodiment, the cutoff frequency may be determined by the motor speed. The generator data may be time-sampled at a frequency greater than or equal to the Nyquist rate. In one embodiment, the time-domain signal may be sampled at a frequency greater than twice the motor's first-order frequency. In one embodiment, the time-domain signal may be sampled at a frequency greater than twice the motor's cutoff frequency.Thus, low-pass filtering and sampling at a frequency higher than or equal to the Nyquist rate prevent the frequency content of the generator data from being corrupted. The same can be true for the motor speed data.

[0040] Fig. Figure 8 is an illustration of example embodiments of how the frequency content of a time-domain torque profile may be generated, which may be used for engine diagnostics. The estimated engine combustion torque profile (time-domain data) may be input to a Fourier transform process 810 (e.g., a Fast Fourier Transform (FFT) process or a bandpass filtering process 820) to extract the frequency content of the estimated engine combustion torque profile. Furthermore, generator signals (e.g., the DC link voltage) and the engine speed signal may be processed to extract the frequency content in a similar manner.

[0041] As discussed herein, the sampled generator data (e.g., the DC link voltage, torque, etc.) may be transformed to generate frequency-domain frequency content. In one embodiment, a fast Fourier transform (FFT) may be used to generate the frequency-domain frequency content. In another embodiment, a bandpass filtering process may be used to generate the frequency-domain content. The frequency analysis process transforms the sampled time-domain parameters into frequency content in the frequency domain. The various frequency components of the frequency content may include DC (zero-order), fundamental (first-order), and harmonic (second-order, half-order, third-order, etc.) frequency components.According to one embodiment, the fast Fourier transform process and the bandpass filter process include computer-executable instructions executed by processor 152.

[0042] In one embodiment, a correlation algorithm may be applied to compare the frequency content of the generator data with a signature for a condition of the engine. For example, the signature for a healthy engine may include a frequency content at the first-order frequency with a magnitude below a first-order threshold and a frequency content at the half-order frequency with a magnitude below a half-order threshold. The first-order threshold may correspond to engine speed, engine load, crankcase temperature, and historical engine data. Furthermore, the threshold level T may depend on an operating condition of the engine, such as power, speed, ambient conditions, repair history, etc.

[0043] For example, the historical engine and generator data may be stored in a database containing samples of frequency content from previous operation of the engine. Thus, a trend in frequency content can be detected, and the trend can be used to determine the health of the machine. For example, an increasing magnitude in the engine's half-order component for a given engine speed and load may indicate that a cylinder is deteriorating. As another example, an increasing average crankcase pressure associated with an increasing magnitude in the engine's half-order component for a given engine speed and load may indicate that the turbocharger or crankcase ventilation system is deteriorating. A possible fault may involve a deteriorated cylinder, a deteriorated turbocharger, or a deteriorated crankcase ventilation system.

[0044] In one embodiment, the frequency content of the combustion torque profile may be stored in a database. In another embodiment, the measurement baseline torque profile may be stored in the database. For example, the database may be stored in memory 154 of controller 150. As another example, the database may be stored at a location external to rail vehicle 106. For example, historical data may be included in a message and transmitted via communication system 190. In this way, the command center may perform steps to diagnose the condition of the engine using the combustion torque profile data transmitted via communication system 190.For example, the command center may receive estimated engine combustion torque profile data from the rail vehicle 106, perform a frequency transformation of the torque profile data, and diagnose potential engine degradation. Alternatively, the command center may receive estimated engine combustion torque profile data from the rail vehicle 106 and apply a template matching algorithm to the estimated data (perform a comparison to a measured baseline torque profile) and diagnose potential engine degradation. Furthermore, the command center may schedule maintenance and deploy fault-free locomotives and maintenance personnel in a manner that optimizes the capital investment. Historical torque profile data may also be used to evaluate engine health before and after engine service, engine modification, and engine component replacement.

[0045] In one embodiment, a potential fault may be reported to the locomotive operating crew via an indicator 180. With the report, the operator can adjust the operation of the rail vehicle 106 to reduce the possibility of further engine deterioration. In one embodiment, a report indicating a potential fault may be sent to a command center using the communication system 190. Furthermore, the severity of the potential fault may be reported. For example, diagnosing a fault based on a comparison of an estimated torque profile with a measured baseline torque profile may enable the detection of a fault earlier than if the fault is diagnosed using only average engine information (e.g., only the speed information). Thus, if a potential fault is diagnosed in the early stages of deterioration, the engine can continue to operate.In contrast, if a potential fault is diagnosed as severe, it may be desirable to stop the engine or schedule immediate maintenance. In one embodiment, the severity of a potential fault may be determined based on the difference between a threshold and the magnitude of one or more components of the frequency content of the estimated engine torque profile induced by combustion in the engine.

[0046] By analyzing the estimated combustion torque profile data, it may be possible to monitor and diagnose the engine during operation. Further, the operation of an engine with a degraded component may be adjusted to potentially reduce additional degradation of the engine component and potentially reduce the likelihood of additional engine failure and failure during operation. For example, the half-order component may be compared to a half-order threshold. In one embodiment, if the magnitude of the half-order component is greater than the half-order threshold, the possible fault may be a degraded cylinder. However, if the magnitude of the half-order component is not greater than the half-order threshold, the possible fault may be a degraded turbocharger or a degraded crankcase ventilation system.

[0047] In one embodiment, the potential fault may be reported to the locomotive operating crew via a display device 180, and the operator may adjust the operation of the rail vehicle 106 to reduce the possibility of further deterioration. In one embodiment, a message diagnosing the potential fault may be transmitted to a command center via the communication system 190.

[0048] In one embodiment, an engine operating parameter may be adjusted to identify a degraded cylinder. For example, the degraded cylinder may be identified based on selectively disabling fuel injection to one or more cylinders of the engine. In one embodiment, fuel injection may be disabled for each of the plurality of cylinders in a sequence while monitoring one or more of the generator data items and the associated frequency content. For example, fuel injection to one cylinder may be disabled while the other cylinders are operating normally. By disabling each cylinder in a sequence, the degraded cylinder may be identified. As another example, fuel injection to a group of cylinders may be disabled while the other cylinders are operating normally.By cycling through different groups in a sequence, the deteriorated cylinder can be identified through a process of elimination.

[0049] In one example, the half-order frequency component of the torque profile data may be monitored for each deactivated cylinder of a four-stroke engine. The deactivated cylinder may be a degraded cylinder if the half-order frequency component decreases below a half-order threshold while the cylinder is deactivated. The deactivated cylinder may be a healthy cylinder if the half-order frequency component remains above the half-order threshold while the cylinder is deactivated. In other words, the degraded cylinder may be the cylinder that contributes a higher frequency component to the half-order frequency component than other cylinders. In one embodiment, the selective deactivation diagnostic may be performed when the engine is operating at idle or under light load.

[0050] In one embodiment, the degraded cylinder may be identified based on a selective change in fuel injection to one or more cylinders of the engine. For example, the fuel may be selectively increased or decreased for each cylinder while monitoring the half-order frequency component of the estimated torque profile. Samples generator data. The controller may be further operable to transform signals from one or more generator sensors into an electromagnetic torque profile of the generator. The controller may be further operable to derive an inertial torque profile of the engine from the engine speed measured by the speed sensor and modify the inertial torque profile based on the electromagnetic torque profile to estimate a combustion torque profile of the engine.The control device may further be operable to diagnose a condition of the engine based on the estimated combustion torque profile. The test set may further include one or more sensors for measuring generator parameters (e.g., generator output voltage) and / or engine parameters (e.g., engine speed).

[0051] In the specification and claims, reference is made to a number of terms having the meanings set forth below. The singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Approximate language, as used throughout the specification and claims, may be applied to modify any quantitative representation that may permissibly vary without resulting in a change in the basic function to which it relates. Accordingly, a value modified by a term or terms such as "about" is not limited to the precise value stated. In some cases, the approximate language may correspond to the accuracy of an instrument for measuring the value.Similarly, "free from" may be used in combination with a term and may include an insignificant number or trace amount while still being considered free from the modified term. Furthermore, unless specifically stated otherwise, any use of the terms "first," "second," etc., does not imply order or importance; instead, the terms "first," "second," etc., are intended to distinguish one element from another.

[0052] As used herein, the terms "can" and "may be" indicate a possibility of occurring within a group of circumstances; of possessing a specified property, characteristic, or function; and / or qualify another verb by expressing one or more of the abilities, capacities, or possibilities associated with the qualified verb. Accordingly, the use of "can" and "may be" indicates that a modified term is obviously appropriate, capable, or suitable for a specified capability, function, or use, while contemplating that under certain circumstances, the modified term may sometimes not be appropriate, capable, or suitable.For example, under certain circumstances, an event or capability may be expected, while under other circumstances, the event or capability may not occur—this distinction is captured by the terms “may” and “may be.” The terms “generator” and “alternator” are used interchangeably herein (although it will be recognized that one or the other may be more appropriate depending on the application). The terms “frequency content” and “harmonic content” are used interchangeably herein and may refer to fundamental frequency (and / or phase) components and associated harmonic frequency (and / or phase) components above and below the fundamental components. The term “instructions,” as used herein with reference to a controller or processor, may refer to computer-executable instructions.

[0053] The embodiments described herein are examples of articles, systems, and methods that correspond to elements of the invention recited in the claims. This description may enable those skilled in the art to make and use embodiments having alternative elements that also correspond to elements of the invention recited in the claims. The scope of the invention thus includes articles, systems, and methods that do not differ from the language of the claims, and further includes other articles, systems, and methods with insubstantial differences from the language of the claims. Although only certain features and embodiments of the invention have been shown and described herein, many modifications and changes will be apparent to those skilled in the art. The appended claims cover all such modifications and changes. List of reference symbols 100 vehicle system 102 Rail 106 rail vehicles 108 wheels 110 engine 111 Motor shaft 120 Generator (three-phase generator) 130 traction motor(s) 140 auxiliary systems 141 fans 142 compressors 143 Radiator fan 144 mechanically driven auxiliary units 150 Control device 152 processor 154 memory 160 speed sensor 162 engine actuators 170 generator sensor(s) 171 DC link sensor 172 field sensor 173 Generator output voltage sensor 174 Generator output current sensor 180 display device 182 User input controls 190 Communication system 210 rectifier 220 inverters 230 power regulator 300 procedures 320 process steps 330 process step 340 process steps 350 process steps 360 process steps 370 process steps 410 three-phase generator model 420 reverse model of the rectifier 430 generator model 440 Electromagnetic torque estimation process 510 Inertia torque estimation process 610 Engine torque estimation process 710 Torque comparison process 810 FFT process 820 bandpass filtering process

Claims

[1] A method for a reciprocating engine (110) operatively connected to a generator (120), comprising the step of: diagnosing a condition of the engine (110) by comparing an estimated engine torque profile caused by combustion in an engine (110) with an expected engine torque profile, wherein the estimated engine torque profile caused by combustion in the engine (110) is derived from an electromagnetic torque of the generator (120) and an inertia torque of the reciprocating engine (110), and wherein the electromagnetic torque is derived from at least one electrical parameter associated with the generator (120), characterized byin that the at least one electrical parameter includes at least one of a voltage of a DC intermediate circuit (171), a current of a DC intermediate circuit (171), a field voltage of the generator (120), a field current of the generator (120), an output voltage of the generator (120), and an output current of the generator (120). [2] The method of claim 1, wherein the inertia torque is derived from the speed of the rotating shaft (111) of the reciprocating engine (110). [3] A method for a reciprocating engine (110) operatively connected to a generator (120), comprising the step of: diagnosing an in-cylinder pressure profile of the engine (110) by comparing an estimated engine torque profile caused by combustion in the engine (110) with an expected engine torque profile, wherein the estimated engine torque profile caused by combustion in the engine (110) is derived from an electromagnetic torque of the generator (120) and an inertia torque of the reciprocating engine (110), and wherein the electromagnetic torque profile is derived from at least one electrical parameter associated with the generator (120), characterized byin that the at least one electrical parameter includes at least one of a voltage of a DC intermediate circuit (171), a current of a DC intermediate circuit (171), a field voltage of the generator (120), a field current of the generator (120), an output voltage of the generator (120), and an output current of the generator (120). [4] The method of claim 3, wherein the inertia torque profile is derived from the speed of the rotating shaft (111) of the reciprocating engine (110). [5] A vehicle system (100) comprising: an engine (110); a generator (120) operatively connected to the engine (110); at least one sensor (170) for measuring at least one electrical parameter associated with the generator (120) during operation; a sensor (160) for measuring the speed of a rotating shaft (111) of the engine (110); and a controller (150) having instructions configured to: sample the at least one electrical parameter and transform it into an electromagnetic torque profile; sample the speed of the rotating shaft (111) and transform it into an inertial torque profile; and estimate the engine torque profile induced by combustion in the engine (110) from the electromagnetic torque profile and the inertial torque profile. [6] The vehicle system (100) of claim 5, further comprising the step of diagnosing a condition of the engine (110) by comparing the estimated engine torque profile caused by combustion in the engine (110) with an expected torque profile of the engine (110). [7] The vehicle system (100) of claim 6, wherein the control device (150) is operable to report a degraded condition of the engine (110). [8] The vehicle system (100) of claim 6, wherein the controller (150) further includes instructions configured to adjust an operating parameter of the engine (110) based on the diagnosed condition. [9] The vehicle system (100) of claim 5, further comprising the step of diagnosing an in-cylinder pressure profile of the engine (110) by comparing the estimated engine torque profile caused by combustion in the engine (110) with an expected torque profile of the engine (110).

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