SPEED OF AN ENGINE

BACKGROUND

[0001] Embodiments of the present specification relate generally to a method and a system for controlling an engine, and more particularly to a method and a system for determining a maximum efficiency operating speed of the engine.

[0002] Typically, engines such as internal combustion engines find application in vehicles operable on land, water, and air, power generation systems, and industrial machinery. The internal combustion engines are typically operated using fuels such as petrol, diesel, natural gas, biogas, liquefied petroleum gas (LPG), compressed natural gas (CNG), and the like. Further, it is desirable to optimize use of the available fuel resources. Accordingly, it is desirable to operate the engine at an optimum efficiency for a given power requirement.

[0003] It may be noted that to ensure operation of the engine at the optimum efficiency for the given power requirement, an engine characterization is performed, typically, during a manufacturing stage of the engine. The engine characterization includes determining an optimum operating speed of the engine to ensure operation of the engine at its optimum efficiency. Traditional engine characterization techniques entail an estimation of fuel being consumed by the engine. The estimation of the fuel is dependent on various parameters, for example, fuel density, pressure, temperature, and the like. In certain situations, the estimation of the fuel may not be accurate, thereby leading to erroneous engine characterization. Moreover, if an unknown engine is used in any application, an operator or control system of such an engine may not be able to operate the engine efficiently. Additionally, an efficient characterization of the engine is a time consuming and challenging task.

[0004] In addition, the engine characterization performed at the manufacturing stage may not be valid during the entire life of the engine due to the ageing of the engine and the internal components of the engine during the lifetime of the engine. Accordingly, the aging of the engine may also lead to deterioration in the performance of the engine. Therefore, optimizing engine performance during operation of the engine is an additional challenge.

BRIEF DESCRIPTION

[0005] In accordance with aspects of the present specification, a control sub-system for determining a maximum efficiency operating speed of an engine is presented. The engine is operatively coupled to an engine control unit. The control sub-system includes a measurement unit operatively coupled to the engine, where the measurement unit is configured to generate electrical signals indicative of an engine power. The control sub-system further includes a controller operatively coupled to the engine control unit. The controller is configured to (a) measure the engine power based on the electrical signals received from the measurement unit, (b) determine a maximum efficiency operating speed of the engine corresponding to the engine power based on a value of a fuel command received from the engine control unit, and (c) communicate control commands to the engine control unit to operate the engine at the maximum efficiency operating speed corresponding to the engine power.

[0006] In accordance with another aspect of the present specification, a method for determining a maximum efficiency operating speed of an engine corresponding to an engine power is presented. The engine is operatively coupled to an engine control unit. The method includes (a) communicating control commands to the engine control unit to update an operating speed of the engine, (b) receiving a fuel command from the engine control unit in response to the control commands, (c) repeating steps (a) and (b) until a value of the fuel command attains a minimum value corresponding to the engine power, and (d) identifying the updated operating speed corresponding to the minimum value of the fuel command as the maximum efficiency operating speed of the engine corresponding to the engine power.

[0007] In accordance with yet another aspect of the present specification, a method for operating an engine is presented. The engine is operatively coupled to an engine control unit. The method includes (a) measuring an engine power, (b) determining a maximum efficiency operating speed of the engine corresponding to the engine power based on a value of a fuel command received from the engine control unit, and (c) communicating control commands to the engine control unit to operate the engine at the maximum efficiency operating speed corresponding to the engine power.

[0008] In accordance with aspects of the present specification, a power generation system is presented. The power generation system includes an engine. The power generation system further includes an engine control unit operatively coupled to the engine and configured to control operation of the engine. Further, the power generation system includes a generator mechanically coupled to the engine and configured to generate an alternating current (AC) voltage and current. Moreover, the power generation system includes a control sub-system operatively coupled to the engine control unit and the generator. The control sub-system includes a measurement unit operatively coupled to the engine, where the measurement unit is configured to generate electrical signals indicative of an engine power. The control sub-system further includes a controller operatively coupled to the engine control unit. The controller is configured to (a) measure the engine power based on the electrical signals received from the measurement unit, (b) determine a maximum efficiency operating speed of the engine corresponding to the engine power based on a value of a fuel command received from the engine control unit, and (c) communicate control commands to the engine control unit to operate the engine at the maximum efficiency operating speed corresponding to the engine power.

DRAWINGS

[0009] These and other features, aspects, and advantages of the present specification will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

[0010] FIG. 1 is a diagrammatic representation of a system for determining a maximum efficiency operating speed of an engine, in accordance with aspects of the present specification;

[0011] FIG. 2 is a diagrammatic representation of a system for determining a maximum efficiency operating speed of an engine in a power generation sub-system, in accordance with aspects of the present specification;

[0012] FIG. 3 is a flow diagram of an example method for operating the engine of FIG. 1 or FIG. 2, in accordance with aspects of the present specification; and

[0013] FIG. 4 is a flow diagram of an example method for determining a maximum efficiency operating speed of the engine of FIG. 1 or FIG. 2 corresponding to an engine power, in accordance with aspects of the present specification.

DETAILED DESCRIPTION

[0014] In the following specification and the claims, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. As used herein, the term "or" is not meant to be exclusive and refers to at least one of the referenced components being present and includes instances in which a combination of the referenced components may be present, unless the context clearly dictates otherwise. [0015] As used herein, the terms "may" and "may be" indicate a possibility of an occurrence within a set of circumstances; a possession of a specified property, characteristic or function; and/or qualify another verb by expressing one or more of an ability, capability, or possibility associated with the qualified verb. Accordingly, usage of "may" and "may be" indicates that a modified term is apparently appropriate, capable, or suitable for an indicated capacity, function, or usage, while taking into account that in some circumstances, the modified term may sometimes not be appropriate, capable, or suitable.

[0016] As will be described in detail hereinafter, systems and methods for determining a maximum efficiency operating speed of an engine are presented. As will be appreciated, during operation, the engine is configured to generate a requisite amount of engine power based on a load requirement. Additionally, while the engine is delivering the requisite amount of engine power, it is also desirable to optimize use of fuel by the engine. In accordance with aspects of the present specification, the systems include a control sub-system configured to measure the engine power being delivered by the engine, determine a maximum efficiency operating speed of the engine corresponding to the engine power, and operate the engine at the maximum efficiency operating speed. Advantageously, determining and operating the engine at the maximum efficiency operating speed aid in minimizing fuel consumption by the engine while delivering the requisite engine power.

[0017] FIG. 1 is a diagrammatic representation 100 of a system for determining a maximum efficiency operating speed of an engine 104, in accordance with aspects of the present specification. The system 100 includes an engine 104 and an engine control unit (ECU) 106. The engine 104 and the ECU 106 may collectively be referred to as an engine sub-system 102. The ECU 106 may be operatively coupled to the engine 104 and configured to control functionality of the engine 104.

[0018] In a presently contemplated configuration, the system 100 includes a control sub-system 108. The control sub-system 108 is operatively coupled to the engine sub-system 102 and configured to control the functionality of the engine 104 via the ECU 106. In particular, the control sub-system 108 is configured to determine the maximum efficiency operating speed of the engine 104. It may be noted that in one embodiment, the maximum efficiency operating speed may be a single value of the operating speed. However, in certain other embodiments, the maximum efficiency operating speed may include a range of values of the operating speed. In one embodiment, the control sub-system 108 includes a measurement unit 110 and a controller 112. In some embodiments, the control sub-system 108 may also include a temperature sensor 114 and a pressure sensor 116 that are operatively coupled to the controller 112.

[0019] The engine 104 is representative of any system that is capable of converting chemical energy of one or more fuels into mechanical work. In certain embodiments, the engine 104 may be an internal combustion engine. Non-limiting examples of such an internal combustion engine may include an engine that is operable at variable speeds, a gas turbine, a compressor, or combinations thereof. In one example, the engine 104 is a variable speed reciprocating engine which typically includes a combustion chamber (not shown), a piston (not shown), and a crankshaft (not shown) mechanically coupled to the piston. Further, the engine 104 may be operated by combustion of various fuels including, but not limited to, diesel, natural gas, petrol, liquefied petroleum gas (LPG), biogas, biomass, producer gas, and the like. The engine 104 may also be operated using a waste heat cycle. It may be noted that the scope of the present specification is not limited by the types of fuel and the engine 104 employed in the engine subsystem 102. A combustion of one or more fuels in the combustion chamber of the engine 104 results in a reciprocating motion of the piston. The reciprocating motion of the piston is in turn translated into rotations of the crank shaft. In some embodiments, the engine 104 may be coupled to a load such as a generator (see FIG. 2), a mechanical power train, or a combination thereof. As will be appreciated, the engine 104 may be operated to generate a requisite amount of the engine power in accordance with a load requirement.

[0020] The ECU 106 is operatively coupled to the engine 104 and configured to control the operation of the engine 104 by communicating control commands to the engine 104. By way of example, the ECU 106 may be configured to communicate control commands to the engine 104 to vary one or more operating parameters of the engine such as a speed, a torque, the engine power, or combinations thereof. In some embodiments, the operating parameters of the engine 104 may be controlled via a fuel command generated by the ECU 106. The term "fuel command" refers to a control signal or a digital command that is used to control an amount of fuel dispensed in the combustion chamber of the engine 104. In some embodiments, the fuel command is a numerical value. In other embodiments, the fuel command may include a pulse of a determined duration, a fuel injection duration, an inlet valve opening duration, or combinations thereof. In such embodiments, the controller 112 may be additionally configured to determine a numerical value of the fuel command based on the pulse of a determined duration, the fuel injection duration, the inlet valve opening duration, or combinations thereof. [0021] In a non-limiting example, the numerical value of the fuel command may be indicative of an amount of the fuel to be dispensed in the combustion chamber of the engine 104. A lower value of the fuel command is indicative of a lower amount of fuel to be dispensed in the combustion chamber of the engine 104. Whereas, a higher value of the fuel command is indicative of a higher amount of fuel to be dispensed in the combustion chamber of the engine 104.

[0022] In certain embodiments, the ECU 106 may include a specially programmed general purpose computer, a microprocessor, a digital signal processor, and/or a microcontroller. The ECU 106 may also include input/output ports, and a storage medium, such as an electronic memory. Various examples of the microprocessor include, but are not limited to, a reduced instruction set computing (RISC) architecture type microprocessor or a complex instruction set computing (CISC) architecture type microprocessor. Further, the microprocessor may be a single- core type or multi-core type. Alternatively, the ECU 106 may be implemented as hardware elements such as circuit boards with processors or as software running on a processor such as a commercial, off-the-shelf personal computer (PC), or a microcontroller.

[0023] As will be appreciated, it is desirable to ensure that the engine 104 consumes a minimum amount of fuel while delivering the engine power. In accordance with aspects of the present specification, the control sub-system 108 is configured to control the operation of the engine 104 such that consumption of fuel by the engine 104 is minimized while delivering the requisite engine power. In particular, the control sub-system 108 is configured to operate the engine 104 at a maximum efficiency operating speed corresponding to the engine power to optimize the fuel consumption. As used herein, the term operating speed of the engine 104 represents a rotational speed in revolutions per minute (rpm) of a crankshaft of the engine 104. Further, as used herein, the term maximum efficiency operating speed represents an operating speed of the engine 104 that facilitates minimum fuel consumption for the requisite engine power.

[0024] As previously noted, the engine 104 may be operated to generate the requisite engine power in accordance with the load requirement. It is desirable that the engine 104 consumes minimum fuel while delivering the requisite engine power.

[0025] As noted hereinabove, the control sub-system 108 includes the measurement unit 110 and the controller 112. Also, the control sub-system 108 is configured to determine the maximum efficiency operating speed of the engine 104 to minimize fuel consumption of the engine 104 while delivering the requisite engine power. To that end, the measurement unit 110 is configured to measure the engine power being generated by the engine 104. More particularly, the measurement unit 110 is configured to generate electrical signals that are indicative of the requisite engine power. By way of example, these electrical signals may include a torque signal, a speed signal, or a combination thereof. In some embodiments, the measurement unit 110 may include a speed sensor (not shown) and/or a torque sensor (not shown). The speed sensor is configured to generate an electrical signal that is representative of an rpm of the crankshaft of the engine 104. Similarly, the torque sensor is configured to generate an electrical signal that is indicative of a torque exerted on the crankshaft of the engine 104.

[0026] The speed sensor and/or torque sensor may be disposed in physical contact with the engine 104. In some other embodiments, the speed sensor and/or torque sensor may be disposed proximate to the engine 104. Non-limiting examples of the speed sensor may include a rotary type encoder, a photoelectric sensor, a magnetic rotational speed sensor, or combinations thereof. Also, non-limiting examples of the torque sensors may include a magneto-elastic torque sensor, strain gauge based torque sensor, a surface acoustic wave (SAW) device based torque sensor, a twist angle measurement or phase shift measurement based torque sensor, or combinations thereof.

[0027] The controller 112 is operatively coupled to the measurement unit 110 and configured to receive the electrical signals from the measurement unit 110. In certain embodiments, the controller 112 is electrically coupled to the speed sensor and/or the torque sensor of the measurement unit 110 and configured to directly receive the electrical signals indicative of the torque and the speed of the crankshaft of the engine 104. In one embodiment, the controller 112 may include a specially programmed general purpose computer, a microprocessor, a digital signal processor, and/or a microcontroller. The controller 112 may also include input/output ports, and a storage medium, such as, an electronic memory. Various examples of the microprocessor include, but are not limited to, a reduced instruction set computing (RISC) architecture type microprocessor or a complex instruction set computing (CISC) architecture type microprocessor. Further, the microprocessor may be a single-core type or multi-core type. Alternatively, the controller 112 may be implemented as hardware elements such as circuit boards with processors or as software running on a processor such as a commercial, off-the-shelf personal computer (PC), or a microcontroller.

[0028] Moreover, the controller 112 is configured to measure the engine power being generated by the engine 104 based on the electrical signals received from the measurement unit 110. More particularly, the controller 112 is configured to measure the requisite engine power generated by the engine 104 based on the torque and speed signals received from the torque sensor and the speed sensor of the measurement unit 110. In one example, the controller 112 may measure the engine power ( P _e ) using equation (1). Ρ _β = τ * ω (1) where τ represents a magnitude of the torque signal and ω represents a speed of the crankshaft of the engine 104 in rpm.

[0029] It may be noted that a measured engine power ( P _e ) is representative of the engine power being generated by the engine 104. It is to be noted that the terms "engine power," "requisite engine power," and "measured engine power" are used interchangeably in the present specification. Moreover, it is desirable to operate the engine 104 such that the fuel consumption is minimized while generating the requisite engine power. Accordingly, the controller 112 is configured to determine the maximum efficiency operating speed of the engine 104 corresponding to the engine power. As previously noted, the maximum efficiency operating speed of the engine 104 is an operating speed of the engine 104 that facilitates minimum consumption of fuel by the engine 104.

[0030] In accordance with aspects of the present specification, the controller 112 is configured to determine the maximum efficiency operating speed of the engine 104 corresponding to the engine power based on the fuel command received from the ECU 106. Typically, the ECU 106 is configured to generate and communicate the fuel command to the engine 104 to facilitate operation of the engine 104 at a particular operating speed. In accordance with aspects of the present specification, the ECU 106 is also configured to concurrently communicate the fuel command to the control sub -system 108.

[0031] Moreover, the controller 112 is configured to ensure that the fuel command attains a minimum value corresponding to the engine power to facilitate operation of the engine 104 using the minimum amount of fuel. As previously noted, the numerical value of the fuel command is indicative of the amount of the fuel to be dispensed in the combustion chamber of the engine 104. More particularly, as the numerical value of the fuel command decreases, the amount of the fuel to be dispensed in the combustion chamber also decreases. Hence, the minimum value of the fuel command corresponds to a minimum amount of the fuel to be dispensed in the combustion chamber of the engine 104. Accordingly, the controller 112 is configured to instruct the ECU 106 to operate the engine 104 at different operating speeds. In particular, the controller 112 is configured to communicate/transmit one or more control commands to instruct the ECU 106 to alter the operating speed of the engine 104. By way of example, the controller 112 may communicate a first set of control commands to instruct the ECU 106 to increase the operating speed of the engine 104. The controller 112 may also communicate a second set of control commands to instruct the ECU 106 to decrease the operating speed of the engine 104.

[0032] Upon receipt of the control commands from the controller 112, the ECU 106 is configured to generate a new fuel command based on a relationship between the control command, the operating speed of the engine 104, and the fuel commands. In one example, this relationship between the control command, the operating speed of the engine 104, and the fuel commands may be retrieved by the ECU 106 from a look-up table. The ECU 106 is configured to communicate the new fuel command to the engine 104 to alter the operating speed of the engine 104. The controller 112 is configured to monitor the fuel commands corresponding to the different operating speeds of the engine 104.

[0033] In some embodiments, the controller 112 may continue to instruct the ECU 106 to alter the operating speed of the engine 104 and monitor the corresponding fuel commands transmitted from the ECU 106 to the engine 104 until the fuel command attains the minimum value for the engine power. The aspect of determining if the fuel command has attained the minimum value corresponding to the engine power will be described in greater detail in conjunction with FIG. 4. The minimum value of the fuel command corresponds to a minimum fuel consumption by the engine 104 for generating the requisite engine power. Accordingly, if the controller 112 determines that the value of the fuel command has attained the minimum value, the controller 112 is configured to identify the operating speed of the engine 104 corresponding to the minimum value of the fuel command as the maximum efficiency operating speed of the engine 104. In some embodiments, the controller 112 is configured to communicate a set of third control commands to the ECU 106 to facilitate operation of the engine 104 at the identified maximum efficiency operating speed.

[0034] In certain instances, while the engine 104 is operating at the maximum efficiency operating speed corresponding to the requisite engine power, one or more parameters, including, but not limited to, an ambient temperature, an ambient pressure, an altitude, or combinations thereof, may impact the engine power and consequently the fuel consumption by the engine 104. Therefore, it may be desirable to monitor the engine power to identify any changes in the value of the engine power. In one embodiment, the controller 112 is employed to monitor the value of the engine power. In addition, if the controller 112 identifies any change in the engine power, the controller 112 is configured to perform corrective measures to optimize the fuel consumption by the engine 104. [0035] Moreover, in certain embodiments, the controller 112 is configured to identify any changes in the engine power by measuring a present value of the engine power based on the torque and/or speed signals received from the measurement unit 110. The controller 112 is configured to compare the present value of the engine power with a previously measured engine power to identify any change in the value of the engine power. By way of example, if the present value of the engine power is different than that of the previously measured engine power, the controller 112 is configured to identify a change in the engine power. However, if the present value of the engine power is the same as or substantially similar to that of the previously measured engine power, the controller 112 is configured to identify that there is no change in the engine power.

[0036] Furthermore, based on the comparison, if the controller 112 determines that there is a change in the engine power, the controller 112 is configured to determine a maximum efficiency operating speed corresponding to the present value of the engine power. The controller 112 is also configured to communicate control commands to the ECU 106 to operate the engine 104 at the maximum efficiency operating speed corresponding to the present value of the engine power.

[0037] In certain embodiments, the controller 112 may be configured to continuously or periodically ascertain whether the engine power has changed and accordingly take corrective measures to optimize the fuel consumption by the engine 104. Some examples of the periodic monitoring include weekly, monthly, quarterly, half-yearly, or yearly checks. Also, the frequency of the periodic checks may be user defined and/or customizable. In this example, the controller 112 may be configured to periodically determine the engine power and the maximum efficiency operating speed corresponding to the engine power. Moreover, the engine 104 may be operated at the determined maximum efficiency operating speed.

[0038] As previously noted, the control sub-system 108 also includes the temperature sensor 114. The temperature sensor 114 is configured to measure an ambient temperature of the engine 104. Further, the temperature sensor 114 is configured to generate an electrical signal indicative of the ambient temperature of the engine 104.

[0039] Moreover, the controller 112 is configured to determine a value of the ambient temperature corresponding to the engine 104 based on the electrical signal received from the temperature sensor 114. Also, the controller 112 may be configured to determine whether the value of the ambient temperature is within a determined temperature tolerance range. In one example, the controller 112 may be configured to compare the value of the ambient temperature with a determined threshold temperature to determine if the ambient temperature is within the determined temperature tolerance range. Based on the comparison, if it is determined that the value of the ambient temperature is outside the determined temperature tolerance range, the controller 112 may be configured to ascertain any changes in the engine power and accordingly perform corrective measures to optimize the fuel consumption by the engine 104.

[0040] In addition, the control sub-system 108 also includes the pressure sensor 116 that is electrically coupled to the controller 112. The pressure sensor 116 is configured to measure an ambient pressure of the engine 104 and generate an electrical signal that is indicative of the ambient pressure of the engine 104. Further, the controller 112 is configured to determine a value of the ambient pressure based on the electrical signal received from the pressure sensor 116. The controller 112 may also be configured to determine whether the value of the ambient pressure is within a determined pressure tolerance range. In one example, the controller 112 may be configured to compare the value of the ambient pressure with a determined threshold pressure to determine if the ambient pressure is within the determined pressure tolerance range. Based on the comparison, if it is determined that the ambient pressure is outside the determined pressure tolerance range the controller 112 may be configured to ascertain any changes in the engine power and accordingly perform corrective measures to optimize the fuel consumption by the engine 104.

[0041] Implementing the control sub-system 108 as described hereinabove aids in operating the engine 104 to provide the requisite engine power, while minimizing fuel consumption. Also, the control sub-system 108 is configured to perform corrective measures to circumvent any effects of changes in the engine power, ambient temperature, and/or ambient pressure on the fuel consumed by the engine 104, thereby enhancing the performance of the engine 104.

[0042] As will be appreciated, engines are also used in power generation systems to drive a generator. The generator in turn produces electrical power that may be supplied to one or more electrical loads. It is desirable to operate the engine in a fuel-efficient manner in such power generation systems.

[0043] FIG. 2 is a diagrammatic representation 200 of a system for determining a maximum efficiency operating speed of an engine 204 in a power generation sub-system 202, in accordance with aspects of the present specification. The power generation sub-system 202 of FIG. 2 is configured to generate and supply electrical power to one or more electrical loads (not shown) or an electric grid (not shown). In one embodiment, the power generation sub-system 202 includes an engine 204, an ECU 206, and a generator 218. The ECU 206 may be operatively coupled to the engine 204 and configured to control functionality of the engine 204. [0044] Additionally, the system 100 includes a control sub-system 208 that is operatively coupled to the power generation sub-system 202. In particular, the control sub-system 208 is configured to determine the maximum efficiency operating speed of the engine 204. In a presently contemplated configuration, the control sub-system 208 includes a measurement unit 210, a controller 212, a temperature sensor 214, and a pressure sensor 216. It may be noted that the engine 204, ECU 206, controller 212, temperature sensor 214, and pressure sensor 216 are similar to the corresponding elements of FIG. 1.

[0045] The generator 218 in the power generation sub-system 202 may be a synchronous generator, an asynchronous generator, or a doubly-fed induction generator (DFIG). Also, the generator 218 may include a stator, a rotor, and a stator winding. The generator 218 is mechanically coupled to the engine 204. More particularly, the rotor of the generator 218 is mechanically coupled to a crankshaft of the engine 204 either directly or via an intermediate coupling such as a gear box. During operation, rotation of the crankshaft of the engine 204 results in the rotation of the rotor of the generator 218. Moreover, the rotating rotor aids in the generation of power (e.g., an alternating current (AC) voltage and a current) at the stator winding of the generator 218. This power may generally be referred to as a generator power. It may be noted that the generator power is proportional to the engine power. The engine power is in turn dependent on the operating speed of the engine 204. Accordingly, a frequency and/or a magnitude of the generator power are also dependent on the operating speed of the engine 204.

[0046] In the embodiment of FIG. 2, the measurement unit 210 is coupled to the generator 218. More particularly, the measurement unit 210 is electrically or electromagnetically coupled to the stator winding of the generator 218 and configured to generate electrical signals indicative of the generator power. As previously noted, the generator power is indicative of the engine power. In some embodiments, the measurement unit 210 may include a current sensor and/or a voltage sensor. The current sensor and the voltage sensor are configured to measure a current and a voltage induced at the stator winding of the generator 218. Moreover, the current and voltage sensors are also configured to generate electrical signals that are respectively indicative of the measured current and voltage. Further, the measurement unit 210 is configured to communicate the generated electrical signals to the controller 212.

[0047] The controller 212 is configured to measure the generator power based on the electrical signals received from the measurement unit 210. In one example, the controller 1 12 is configured to measure the generator power (P ) based on equation (2). = v * / ^' (2) where v represents a magnitude of a voltage signal and represents a magnitude of a current signal received from the measurement unit 210.

[0048] Once the generator power is measured, the controller 212 is configured to measure the engine power (P _e ) based on the measured generator power. In one example, the controller 112 is configured to measure the generator power (P _e ) based on equation (3).

P _e = f(P _g )

(3)

where / represents a relationship between the generator power P and the engine power P _e .

[0049] In some embodiments, the relationship /between the generator power P and the engine power P _e may be obtained from a look-up table. The look-up table may include information regarding different values of the generator power P and corresponding values of the engine power P _e . Accordingly, in one example, the controller 212 may obtain the engine power P _e corresponding to the generator power P from the look-up table. Moreover, in some embodiments, the controller 212 may be configured to determine a maximum efficiency operating speed corresponding to the engine power P _e and operate the engine 204 at the maximum efficiency operating speed for the engine power, as described with reference to FIG. 1. Implementing the system 200 as described hereinabove, aids in optimizing the use of fuel(s) to produce a desirable value of generator power.

[0050] FIG. 3 is a flow diagram 300 of an example method for operating the engine 104, 204 of FIG. 1 or FIG. 2, in accordance with aspects of the present specification. The method 300 of FIG. 3 is described with reference to the components of FIG. 1. In one embodiment, one or more of the steps of the method 300 may be executed by the controller 112 of the control sub-system 108 of FIG. 1. As will be appreciated, one or more embodiments of FIG. 3 are also applicable to the system 200 of FIG. 2.

[0051] As will be appreciated, the engine 104 is configured to generate the engine power based on the load requirement during operation of the system 100. It is desirable to facilitate operation of the engine 104 to generate the desired engine power while minimizing fuel consumption. [0052] Accordingly, at step 302, the engine power being generated by the engine 104 is measured. In one embodiment, the engine power may be measured by the controller 112 based on electrical signals received from the measurement unit 110. More particularly, the engine power is measured based on the electrical signals generated by the torque sensor and the speed sensor, where the electrical signals are indicative of the torque and operating speed of the engine 104.

[0053] As previously noted, it is desirable to operate the engine 104 such that the engine 104 consumes a minimum amount of fuel while ensuring that the desired engine power is generated to fulfill the load requirement. In accordance with aspects of the present specification, a maximum efficiency operating speed corresponding to the engine power is determined and the engine 104 is operated at the maximum efficiency operating speed to ensure minimum consumption of fuel by the engine 104. As previously noted, the maximum efficiency operating speed may be a single value of the operating speed. Also, in certain other embodiments, the maximum efficiency operating speed may include a range of values of the operating speed.

[0054] Accordingly, at step 304, a maximum efficiency operating speed corresponding to the engine power is determined. In particular, the maximum efficiency operating speed corresponding to the engine power is determined based on fuel commands received from the ECU 106. It may be noted that, in some embodiments, step 304 entails sub-steps 306-314. These steps 306-314 may also be performed by the controller 112.

[0055] At step 306, the controller 112 is configured to receive a fuel command corresponding to the engine power from the ECU 106. Further, at step 308, the controller 112 is configured to communicate control commands to the ECU 106 to update an operating speed of the engine 104. As will be appreciated, the operating speed of the engine 104 may be updated by varying the fuel commands that are communicated to the engine 104 from the ECU 106. Accordingly, the controller 112 is configured to communicate control commands to the ECU 106. The control commands are employed to instruct the ECU 106 to alter the fuel command communicated to the engine 104, thereby altering the operating speed of the engine 104. By way of example, the controller 112 may communicate a first set of control commands to instruct the ECU 106 to increase the operating speed of the engine 104. Also, the controller 112 may communicate a second set of control commands to instruct the ECU 106 to decrease the operating speed of the engine 104. The ECU 106 may in turn update the operating speed of the engine 104 by communicating a corresponding fuel command to the engine 104.

[0056] It may be noted that it is desirable to provide a new fuel command corresponding to a desired alteration of the operating speed of the engine 104. Accordingly, the ECU 106 is configured to generate a fuel command that corresponds to the desired operating speed of the engine 104. The ECU 106 communicates the new fuel command to the controller 112. Moreover, the controller 112 is configured to receive the new fuel command from the ECU 106 in response to the control commands, as indicated by step 310.

[0057] Subsequent to the receipt of the new fuel command from the ECU 106, the controller 112 is configured to verify if the fuel command has attained a minimum value corresponding to the requisite engine power, as indicated by step 312. As will be appreciated, the minimum value of the fuel command corresponding to the requisite engine power facilitates operation of the engine 104 with minimum fuel consumption by the engine 104, while delivering the requisite engine power. In one embodiment, at step 312, the controller 112 may compare the value of the fuel command received at step 310 with a value of a previously received fuel command to ascertain whether a value of the fuel command has decreased with respect to the value of the previously received fuel command. The controller 112 may be configured to determine if the fuel command has attained the minimum value corresponding to the requisite engine power based on a plurality of such comparisons between the value of the fuel command received at step 310 with a value of a previously received fuel command. Further details of determining if the fuel command has attained the minimum value corresponding to the requisite engine power will be described in greater detail in conjunction with FIG. 4. In one example, the previously received fuel command may be the fuel command received at step 306. In another example, the previously received the fuel command may be the fuel command received at the step 310 during a previous iteration of step 312.

[0058] If, at step 312, it is determined that the fuel command has not attained the minimum value corresponding to the requisite engine power, the controller 112 may be configured to repeat the execution of steps 308-312. The execution of steps 308-312 may be repeated until it is determined that the value of the fuel command has attained the minimum value corresponding to the requisite engine power. However, at step 312, it is determined that the fuel command has attained the minimum value corresponding to the engine power, the controller 112 may be configured to identify the updated operating speed corresponding to the minimum value of the fuel command as the maximum efficiency operating speed of the engine corresponding to the engine power, as indicated by step 314. Moreover, at step 316, the controller 112 may be configured to communicate a control command, such as a third control command, to the ECU 106 to operate the engine 104 the maximum efficiency operating speed corresponding to the engine power. [0059] Furthermore, as previously noted, while the engine 104 is operating at the maximum efficiency operating speed, one or more parameters, including but not limited to, the ambient temperature, the ambient pressure, the altitude, or combinations thereof, may impact the engine power. Therefore, in some situations, it may be desirable to ascertain whether the engine power has changed and accordingly perform corrective measures to optimize the fuel consumption by the engine 104. To that end, the controller 112 may be configured to continuously or periodically monitor the engine power to identify any change in the value of the engine power. In one embodiment, the controller 112 is configured to determine a present value of the engine power. Further, the controller 112 is configured to compare the present value of the engine power with that of a previously measured engine power to identify any changes in the value of the engine power. If the present value of the engine power is different from that of the previously measured engine power, the controller 112 may determine that the engine power has changed. If the engine power changes, the controller 112 may be configured to repeat the execution of the steps 306-314 to ensure operation of the engine 104 at the maximum efficiency operating speed corresponding to the present value of the engine power.

[0060] As noted hereinabove, in certain embodiments, the controller 1 12 is configured to periodically ascertain changes in the value of the engine power and accordingly perform corrective measures to optimize the fuel consumption by the engine 104. The frequency to ascertaining changes in the value of the engine power may be weekly, monthly, quarterly, half-yearly, or yearly. Additionally, the frequency of ascertaining changes in the value of the engine power may also be user defined and/or customizable.

[0061] Moreover, during the execution of the steps 302-316 the controller 112 may be configured to develop a repository of operating characteristics of the engine 104. In one embodiment, to develop the repository of the operating characteristics of the engine 104, the controller 112 may be configured to store values of one or more of the engine power, fuel commands, various operating speeds of the engine 104, and the maximum efficiency operating speed in a memory device. In one example, the controller 112 may be configured to store the values of one or more of the engine power, fuel commands, various operating speeds of the engine

104, and the maximum efficiency operating speed in a look-up table. In some embodiments, the look-up table may be stored locally in the memory device associated with the controller 112. In other embodiments, the look-up table may be stored in one or more server computers accessible over the Internet or an intranet. This technique of developing the repository of the operating characteristics of the engine 104 is referred to as learning of the operating characteristics. This learning of the operating characteristics of the engine 104 aids in the prompt identification of a maximum efficiency operating speed corresponding to a value of the engine power from the lookup table. Accordingly, corrective measures may be initiated by the control sub-system 108 to adapt to any change in the requisite engine power may be expedited.

[0062] FIG. 4 is a flow diagram 400 of an example method for determining a maximum efficiency operating speed corresponding to an engine power, in accordance with aspects of the present specification. More particularly, the method 400 may be representative of another embodiment of step 304 of FIG. 3. The method 400 of FIG. 4 is described with reference to the components of FIG. 1. In one embodiment, one or more steps of the method 400 may be executed by the controller 1 12 of the control sub-system 108. It is assumed that the engine power is determined by the controller 1 12 prior to execution of step 402.

[0063] At step 402, the controller 1 12 is configured to receive a fuel command corresponding to the engine power from the ECU 106. Further, at step 404, the controller 1 12 is configured to communicate control commands to the ECU 106 to change an operating speed of the engine 104 by an amount Sc . It may be noted that & may have a positive value or a negative value. The positive value of Sc may be indicative of an increase in the operating speed of the engine 104, while the negative value of Sc may be indicative of a decrease in the operating speed of the engine 104. In response to the receipt of the control commands from the controller 1 12, the ECU 106 is configured to update the operating speed of the engine 104 by the amount & . In one embodiment, the ECU 106 is configured to update the operating speed of the engine 104 by communicating a corresponding "new" fuel command to the engine 104. Accordingly, the ECU 106 is configured to generate the "new" fuel command to the controller 1 12 in response to the control commands. Moreover, at step 406, the controller 1 12 is configured to receive the new fuel command from the ECU 106 in response to the control commands.

[0064] Subsequent to the receipt of the new fuel commands from the ECU 106, the controller 1 12 is configured to carry out a check to determine whether a value of the fuel command received is decreasing with respect to a value of the previously received fuel command. In one embodiment, the previously received fuel command may be the fuel command received at step 402. In another embodiment, the previously received fuel command may be the fuel command received during a previous execution of step 408.

[0065] At step 408, if it is determined that the value of the fuel command is decreasing, control is passed to step 404 and the controller 1 12 is configured to repeat the execution of steps 404-408. More specifically, steps 404-408 are repeated until the controller 1 12 determines that the value of the fuel command is no longer decreasing. The value of the fuel command not decreasing may be indicative that the value of the fuel command has attained a steady value or has increased with respect to the value of the fuel command received during the previous execution of step 408.

[0066] If at step 408 it is determined that the value of the fuel command is not decreasing, control is passed to step 410. At step 410, the controller 112 is configured to determine if the value of the fuel command has attained a minimum value corresponding to the requisite engine power. In one embodiment, the value of the fuel command attains the minimum value when an amount of change in the value of the fuel command with reference to the previously received fuel command is zero or substantially close to zero. The amount of change in the value of the fuel command being zero or substantially close to zero indicates that the value of the fuel command attained a steady state and cannot be decreased any further. However, the amount of change in the value of the fuel command not being zero indicates that the value of the fuel command has increased. Therefore, at step 410, the controller 112 is configured to determine if the value of the fuel command has attained a minimum value corresponding to the requisite engine power based on the amount of change in the value of the fuel command.

[0067] If, at step 410, it is determined that the value of the fuel command has not attained the minimum value corresponding to the engine power, the controller 112 may be configured to reverse a direction of the update in the operating speed of the engine 104, as indicated by step 412. In one embodiment, to reverse the direction of the change in the operating speed of the engine 104, the controller 112 may be configured to alter a polarity of the amount Sx . Subsequently, control is passed to step 404. In such an instance, the execution of steps 404-412 may be repeated till the amount of change in value of the fuel command becomes zero or a polarity of a derivative of the value of the fuel command changes.

[0068] With returning reference to step 410, if it is determined that the value of the fuel command has attained the minimum value corresponding to the engine power, the controller 112 may be configured to identify the updated operating speed corresponding to the minimum value of the fuel command as the maximum efficiency operating speed of the engine corresponding to the engine power, as indicated by step 414.

[0069] Any of the foregoing steps may be suitably replaced, reordered, or removed, and additional steps may be inserted, depending on the needs of a particular application.

[0070] Various embodiments of systems and methods for determining the maximum efficiency operating speed of the engine are presented. The methods and systems described hereinabove facilitate operation of the engine while minimizing fuel consumption. More particularly, optimal fuel consumption is achieved by operating the engine at the maximum efficiency operating speed corresponding to the requisite engine power. Also, the systems and methods provide corrective measures to circumvent adverse effects of aging of the engine and/or changes in the engine power, ambient temperature, and ambient pressure on the fuel consumption by the engine. Moreover, learning of the engine characteristics by the systems also facilitates enhanced adaptation to any change in the engine power.

[0071] It will be appreciated that variants of the above disclosed and other features and functions, or alternatives thereof, may be combined to create many other different applications. Various unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art and are also intended to be encompassed by the following claims.