Patent Application
20230139667
This patent disclosure relates generally to internal combustion engines and, more specifically, to systems and methods of measurement or estimation of engine operating parameters.
Internal combustion engines operate based on a controlled burning of an air and fuel mixture within one or more engine cylinders. Expanding gas trapped within the cylinder, and the pressure it produces, pushes onto a piston disposed in a bore, which in turn provides the work necessary to turn a crankshaft of the engine to produce power. Gas pressure within the engine cylinders is sometimes used to monitor the air/fuel burning progress to better control engine operation. This monitoring is especially useful when the chemical properties of the fuel provided to operate the engine is not known or uniform. For example, engines operating generators (gensets) in an environment where natural gas is used as a fuel to operate the engine may experience unreliable operation if the chemical makeup of the natural gas changes.
To ensure proper engine operation, various solutions have been proposed in the past for devices that can measure cylinder pressure in an operating engine. Some solutions propose use of pressure transducers placed directly in contact with the cylinder gases, but such solutions expose these sensors to extreme operating conditions and are generally unreliable or expensive to implement reliably. Indirect cylinder pressure measurements have also been proposed. For example, U.S. Pat. No. 7,623,955 to Rackmil et al. discusses a method for inferring Indicated Mean Effective Pressure (IMEP) in an engine by monitoring crankshaft rotation. The method disclosed in Rackmil includes acquiring at least one crankshaft time stamp for use in determining a cylinder-specific engine velocity; calculating an incremental change in engine kinetic energy from the previously fired cylinder (j-1st) to the currently fired (jth) cylinder using the cylinder-specific engine velocity; equating the incremental change in engine kinetic energy to a change in energy-averaged cylinder torque (IMEP) from the previously-fired (j-1st) to a currently-fired (jth) cylinder; summing a plurality of the incremental changes in engine kinetic energy over time to determine a value of the transient component of indicated torque; determining a value of the quasi-steady indicated engine torque; and adding the value of transient component of indicated torque to the value of quasi-steady indicated engine torque to yield the Indicated Mean Effective Pressure. However, Rackmil's method, while at least partially effective in estimating cylinder pressure, can also be susceptible to inaccuracy and depends on the rotation of the crankshaft, which is typically connected to a transmission and other rotating structures in a vehicle or machine, which can further introduce inaccuracies in the measurement method.
The disclosure describes, in one aspect, a drive arrangement between a driver and a driven system. The drive arrangement includes a rotatable driver component having first and second sensors associated therewith, the first sensor rigidly mounted relative to the rotatable driver component and configured to provide a first signal indicative of a rotation of the rotatable driver component. The arrangement further includes a rotatable driven component and a flexible coupler disposed between the rotatable driver component and the rotatable driven component. The second sensor is configured to provide a second signal indicative of a rotation of the rotatable driven component. A controller is disposed to receive the first signal and the second signal. The controller is configured to calculate a difference between the first signal and the second signal, and infer a torque variation between the rotatable driver component and the rotatable drive component based primarily on the difference between the first signal and the second signal.
In another aspect, the disclosure describes a genset that includes an engine having a plurality of cylinders, and a generator. Each of the plurality of cylinders of the engine is connected to and configured to drive a flywheel during operation of the engine. A first timing sensor is associated with the engine and provides an input signal indicative of rotation of the flywheel. A flexible coupling has an input side connected to the flywheel and an output side connected to an input shaft of a generator. The input shaft of the generator includes a tone ring. A second timing sensor is rigidly connected relative to the engine and is configured to provide an output signal indicative of a rotation of the tone ring. A controller is associated with the engine. The controller is disposed to receive the input signal and the output signal. The controller is programmed to calculate a difference between the input signal and the output signal, and infer a cylinder pressure in each of the plurality of cylinders based on the difference.
In yet another aspect, the disclosure describes a method for measuring a torque variation across a flexible coupler disposed between a rotatable driver component and a rotatable driven component. The method includes providing the flexible coupler between the rotatable driver and driven components, the flexible coupler having a driver side connected to the rotatable driver component and a driven side connected to the rotatable driven component. First and second sensors are provided and rigidly mounted relative to the driver side of the flexible coupler. Rotation of the rotatable driver component is sensed using the first sensor to provide a first signal. Rotation of the rotatable driven component is sensed using the second sensor to provide a second signal. A difference between the first signal and the second signal is calculated using a controller to infer a torque variation across the flexible coupler based on the difference between the first signal and the second signal.
This disclosure relates to management of engine systems and, more particularly, to systems and methods for the indirect measurement or, stated differently, the inference of cylinder pressure within combustion cylinders of an engine by use of external sensors.
More specifically, in an exemplary embodiment, a genset 100 is shown in an outline view in
The crankshaft is connected to a flywheel 212 (
In the illustrated embodiment, the controller 118 is further configured to tune operation of the engine, for example, in terms of fuel quantity, ignition timing, power output and the like, based on the electrical needs of an electrical consumer system connected to the switchgear 116 and also based on changes of engine operation that are caused by differences in the chemical makeup of the natural gas used to fuel the engine 102. For example, a higher concentration of compounds having a lower octane rating may require retarding of engine ignition and injection timing, and correspondingly a lower quality fuel may require advancement of engine ignition and timing to avoid engine knocking during operation of the engine 102. Engine knocking, as is known, can cause inefficient engine operation because it involves uncontrolled burning of the air/fuel mixture provided to the cylinders 106, and can also increase stresses in engine components, which can increase wear and reduce component service life. To accomplish this, the controller 118 receives signals from sensors that are indicative of cylinder pressure within the cylinders of the engine. This cylinder pressure is measured indirectly based on rotational or angular differences or variations present at the engine to generator connection.
A partial section view through a portion of the engine 102 around a connection end of the flywheel 212 of the engine 102 with the generator 114 is shown in
The coupling hub 206 is elastically connected to an engine output flange 210 via elastomeric elements 208. The engine output flange 210 is connected to the flywheel 212 and is rotated thereby. Rotation of the flywheel 212 causes the output flange 210 to rotate, and the rotation is transferred to the coupling hub 206 connected to the generator input shaft 200 via elastomeric elements 208. The elastomeric elements 208, in a typical configuration, include compressible or stretchable elements in sections that can elastically deform peripherally around the coupling hub 206 and are retained in place by paddles 209 that extend radially or perpendicularly relative to the axis 108 between the coupling hub 206 and the engine output flange 210. Vibrations produced by bursts of power of a particular cylinder firing, or drains of power when another cylinder compresses cause continuous micro stretching and micro compressive stresses in the elastomeric elements 208 in a rotational or angular direction during engine operation. The elastomeric elements 208 also take up any minor axial misalignments between the flywheel 212 and the generator input shaft 200. A protective cover 214 is placed over and around the various rotating components, i.e., the tone ring 204, the flywheel coupling hub 206, the elastomeric elements 208, the engine output flange 210, and any other components that may be present in this area in this and other implementations.
The engine 102 further includes a timing gear formed peripherally around an outer portion of the flywheel 212 having teeth 402 (
As can be seen in the enlarged detail view of
An outline view of the tone ring 204 as installed on the generator 114 is shown in
To illustrate, the sensor readings of the first timing sensor 406 on the engine and the second timing sensor 410 would or should be identical if there was a solid connection between the engine and the generator, i.e., if there were no elastomeric elements 208 used between the flywheel 212 and the generator input shaft 200. However, since the elastomeric elements 208 are present, their minute rotational or angular compression or stretching during engine operation caused by successive torque spikes or delays caused by cylinder operation will cause differences in the readings between the first and second timing sensors 406 and 410, which can also be referred to as an input sensor (the first timing sensor 406) to the flexible coupling between the engine and generator, and an output sensor (the second timing sensor 410). The terms input and output in this context refer to the input and output signal changes of any torque variations provided from the engine to the generator via the flexible coupling that includes the elastomeric elements 208.
The signals from both the input sensor 406 and the output sensor 410 are provided to the controller 118. The controller 118 monitors an input signal from the input sensor 406 and an output signal from the output sensor 410, calculates a difference between the two, and based on the difference between the input and output signals calculates or infers a cylinder pressure that is present concurrently with the measurements within the cylinders of the engine.
More specifically, a graph of the difference between the input and output signals over time for a single cylinder operating on the engine 102 is shown in
In reference to
It has been determined that the curve 500, or a parameter representing the difference between measurements taken by the first and second timing sensors 406 and 410 is a very accurate and reliable indicator of cylinder pressure. The difference parameter tracks cylinder pressure as well as a pressure sensor that is placed within the cylinder, but without requiring sophisticated sensor technologies such as piezo sensors that are configured to operate in the harsh in-cylinder environment. A reliable cylinder pressure determination can be made by using the outputs of the first and second timing sensors 406 and 410, one being the crankshaft sensor that is typically found on engines, and the other being a second sensor that is placed on the engine and measures rotation of a tone ring placed opposite the elastomeric elements 208.
Illustrations of an exemplary embodiment for the placement of the second timing sensor 410 on an engine are shown in the detail views provided in
The present disclosure is applicable to internal combustion engines of any type that include a flexible coupling or connection between an engine output shaft and an input shaft of a driven system. A flowchart of a method of indirectly measuring cylinder pressure is provided in
A first sensor configured to sense rotation of a driver component is mounted on one side of the coupler that is rigidly associated with the driver component or system at 804. A second sensor is mounted on the same side of the coupler that is rigidly associated with the driver side of the system at 806. The second sensor is also configured to sense rotation of a tone ring mounted on the driven side of the coupler, or across the coupler, such that variations in the angular position of the coupler between the driver and driven components will affect the measurement of the second sensor relative to the first sensor. The difference between the first and second sensor signals is calculated at 808, and a rotational or angular deflection of the coupler is inferred at 810 based on the magnitude and direction of the difference. In one embodiment, the driver is an engine, the driven component is a transmission or generator, and the difference is indicative of cylinder pressure in the engine.
As can be appreciated, in an exemplary engine installation having rubber elastomeric couplings, the rotational or angular deflection of the measurement can be about 10 degrees. The controller can be programmed to calibrate the sensor difference at each startup, for example, when the engine is not carrying appreciable load, to account for various differences in the system that may affect measurements such as temperature, the hardness from weathering of the elastomeric elements, and the like. By measuring cylinder pressure during engine operation, the controller can control fuel and ignition timing, if applicable, when ignition requires delay or advancement as indicated by the cylinder pressure on the fly in the event engine operation changes, for example, due to inconsistent fuel quality. By measuring cylinder pressure in this fashion, other parameters such as burn duration, cylinder pressure rise rate, peak pressure, ignition timing and other parameters can also be calculated and used to optimize engine operation.
The tone ring 204, in one embodiment for an engine having 20 cylinders, can be arranged with 183 teeth. In such embodiment, the controller can effectively and accurately sense specific cylinder firings per engine revolution, or a trace that measures the location of about 18 teeth per firing, which provides sufficient resolution to infer the desired engine operating and cylinder firing parameters.
As can be appreciated, in the embodiment described herein two sensors are mounted onto the input side of a flexible coupling (the engine) and measure timing signals of two timing gears, one timing gear being disposed on the input side of the flexible coupling (the engine flywheel) and the other timing gear being disposed on the output side of the flexible coupling (the tone ring). In an alternative embodiment, the sensors may also be mounted onto the output side of the flexible coupling (the generator).
It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated.
Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.
