Patent Description:
Gasoline, diesel and gaseous fuels are mixtures of hydrocarbons, which are compounds that contain hydrogen and carbon atoms. In a "perfect" engine, oxygen in the air would convert all the hydrogen in the fuel to water and all the carbon in the fuel to carbon dioxide. Accordingly, a maximum level of carbon dioxide would be obtained when there is just enough oxygen supplied to react with the carbon in the fuel. On the other hand, when too little air is provided or poor fuel and air mixing occurs, carbon monoxide and soot result and the level of carbon dioxide is low. Additionally, when too much air is provided, the level of carbon dioxide is also low as the extra air dilutes the carbon dioxide.

When a spark ignited engine is run on a gaseous fuel, the amount of carbon dioxide obtained in the engine exhaust gas varies depending on the methane number of the inlet fuel. The methane number of the fuel correlates to a hydrogen/carbon ratio of the fuel. Thus, depending on the inlet fuel quality, the engine air-fuel ratio may need to be adjusted. Accordingly, the methane number may be used to help with adjustments to achieve a maximum level of carbon dioxide by allowing the appropriate amount of fuel for an amount of air provided to be determined.

Thus, it would be advantageous to have a system and method for self-adjusting engine performance parameters in response to fuel quality variations wherein the performance parameters are adjusted based on a determined methane number of the fuel to provide a more controllable and fuel-efficient engine. Patent literature <CIT>, <CIT> and non-patent literature publications <NPL> and <NPL> disclose approaches to use the methane number in gas engine control.

In one embodiment of the present disclosure, a controller for self-adjusting engine performance parameters in response to fuel quality variations according to claim <NUM> is provided.

In another embodiment of the present disclosure, an engine system according to claim <NUM> is provided.

In a further embodiment of the present disclosure, a method for self-adjusting engine performance parameters in response to fuel quality variations according to claim <NUM> is provided.

Advantages and features of the embodiments of this disclosure will become more apparent from the following detailed description of exemplary embodiments when viewed in conjunction with the accompanying drawings, wherein:.

Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of the present disclosure, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the present disclosure. The exemplifications set out herein illustrate embodiments of the disclosure.

Referring to <FIG> and <FIG>, an engine system <NUM> generally includes a mixer <NUM>, an inlet manifold <NUM>, an exhaust manifold <NUM>, an exhaust sensor <NUM>, a knock sensor <NUM> and/or a cylinder pressure transducer <NUM>, a controller <NUM>, an adjusting mechanism <NUM> and an engine <NUM>. Generally, engine system <NUM> further includes a center exhaust manifold positioned between cylinder heads of engine <NUM> (not shown). In various embodiments, engine system <NUM> may also include at least one turbocharger, at least one charge air cooler, at least one throttle, a compressor bypass, and/or a compressor bypass valve. Additionally, in various embodiments, intake manifold <NUM> may extend into the center of the engine between the engine's cylinder heads while exhaust manifold <NUM> includes portions extending along the sides of the engine or intake manifold <NUM> may include portions along the sides of the engine while exhaust manifold <NUM> extends out of the center of the engine between the engine's cylinder heads.

In more detail and still referring to <FIG> and <FIG>, mixer <NUM> generally includes at least two inlets <NUM>, <NUM> and at least one outlet <NUM>. Air and fuel may be introduced into mixer <NUM> through inlets <NUM>, <NUM>, and the mixture of air and fuel may then be released from mixer <NUM> through outlet <NUM> to engine <NUM>. In various embodiments, a fuel line <NUM> is fluidly coupled to inlet <NUM> such that fuel line <NUM> provides fuel to mixer <NUM>.

Referring to <FIG>, exhaust manifold <NUM> is coupled to engine <NUM> to route exhaust gases resulting from fuel used in engine <NUM> away from engine <NUM>. Exhaust sensor <NUM> is positioned along exhaust manifold <NUM> such that exhaust sensor <NUM> may measure a level of carbon dioxide present in the exhaust gases within exhaust manifold <NUM>. In various embodiments, exhaust sensor <NUM> may be positioned at any location after the cylinder(s) of the engine. For instance, exhaust sensor <NUM> may be positioned along the exhaust manifold, at a turbo charger inlet, at a turbo charger outlet or at an exhaust stack.

Furthermore, knock sensor <NUM> and/or cylinder pressure transducer <NUM> are generally in communication with engine <NUM>. In various embodiments, knock sensor <NUM> and/or cylinder pressure transducer <NUM> are coupled to at least one cylinder head(s) <NUM> of engine <NUM>, as shown in <FIG>. In various embodiments, knock sensor <NUM> and/or cylinder pressure transducer <NUM> may be coupled to each cylinder head <NUM> of engine <NUM>. Furthermore, in various embodiments, knock sensor <NUM> may be used to determine a location of peak pressure within engine <NUM>. Generally, knock sensor <NUM> is a simple accelerometer that measures vibration levels on a cylinder head <NUM> of each cylinder of engine <NUM>. Knock sensor <NUM> converts the measured vibration levels into an output voltage. The output voltage from knock sensor <NUM> is directly proportional to the engine combustion quality. By processing the signal coming from the knock sensor, the location of peak pressure can be determined. Location of peak pressure is the location at which the maximum cylinder pressure occurs for each combustion cycle. Additionally, in various embodiments, cylinder pressure transducer <NUM> may be used to determine a centroid of engine <NUM>. Cylinder pressure transducer <NUM> is a pressure measurement device which records cylinder pressure for a cylinder on which it is placed. Once the cylinder pressure is obtained, it can be converted to a heat release rate which shows the quality of combustion. Centroid is the point in the heat release rate where <NUM>% of combustion is complete. The centroid is inversely proportional to engine combustion quality. Thus, if the combustion gets slower, the centroid increases in crank angle degrees.

With reference to <FIG> and <FIG>, adjusting mechanism <NUM> adjusts an engine performance parameter based on a determined methane number. In general, adjusting mechanism <NUM> is manipulated by controller <NUM>. In various embodiments, the engine performance parameter may include the quantity of fuel provided. In an exemplary embodiment, adjusting mechanism <NUM> may be a fuel control valve, wherein the fuel control valve controls the amount fuel delivered to mixer <NUM> based on an optimized air-fuel ratio determined from the methane number by controller <NUM>.

Controller <NUM> is generally in communication with exhaust sensor <NUM>, knock sensor <NUM> and/or cylinder pressure transducer <NUM> and adjusting mechanism <NUM>. Additionally, controller <NUM> may include a plurality of programmable tables. In an exemplary embodiment of the present disclosure, controller <NUM> is an engine control module. In certain embodiments, controller <NUM> forms a portion of a processing subsystem including one or more computing devices having memory, processing, and communication hardware. The controller <NUM> may be a single device or a distributed device, and the functions of the controller may be performed by hardware and/or as computer instructions on a non-transient computer readable storage medium.

Furthermore, in certain embodiments, the controller <NUM> includes one or more processors, evaluators, regulators and/or determiners that functionally execute the operations of the controller <NUM>. The description herein including processors, evaluators, regulators and/or determiners emphasizes the structural independence of certain aspects of the controller <NUM>, and illustrates one grouping of operations and responsibilities of the controller. Other groupings that execute similar overall operations are understood within the scope of the present application. Processors, evaluators, regulators and/or determiners may be implemented in hardware and/or as computer instructions on a non-transient computer readable storage medium, and may be distributed across various hardware or computer based components.

Certain operations described herein include operations to interpret and/or to determine one or more parameters or data structures. Interpreting or determining, as utilized herein, includes receiving values by any method known in the art, including at least receiving values from a datalink or network communication, receiving an electronic signal (e.g. a voltage, frequency, current, or PWM signal) indicative of the value, receiving a computer generated parameter indicative of the value, reading the value from a memory location on a non-transient computer readable storage medium, receiving the value as a run-time parameter by any means known in the art, and/or by receiving a value by which the interpreted parameter can be calculated, and/or by referencing a default value that is interpreted to be the parameter value.

Example and non-limiting implementation elements that functionally execute the operations of the controller include sensors providing any value determined herein, sensors providing any value that is a precursor to a value determined herein, datalink and/or network hardware including communication chips, oscillating crystals, communication links, cables, twisted pair wiring, coaxial wiring, shielded wiring, transmitters, receivers, and/or transceivers, logic circuits, hard-wired logic circuits, reconfigurable logic circuits in a particular non-transient state configured according to the module specification, any actuator including at least an electrical, hydraulic, or pneumatic actuator, a solenoid, an op-amp, analog control elements (springs, filters, integrators, adders, dividers, gain elements), and/or digital control elements.

Referring now to <FIG>, controller <NUM> generally includes one or more processors, evaluators, regulators and/or determiners, such as a centroid/location of peak pressure processor <NUM>, a brake specific carbon dioxide processor <NUM>, a methane number determiner <NUM>, a methane number evaluator <NUM>, an air-fuel ratio determiner <NUM>, and a fueling regulator <NUM>. Brake specific carbon dioxide processor <NUM> is generally configured to receive measurements of exhaust carbon dioxide levels from exhaust sensor <NUM>, while centroid/location of peak pressure processor <NUM> is generally configured to receive signals from knock sensor <NUM> and/or cylinder pressure transducer <NUM>. Furthermore, centroid/location of peak pressure processor <NUM> is configured to process the signals from knock sensor <NUM> and/or cylinder pressure transducer <NUM> to determine a location of peak pressure from knock sensor <NUM> and/or a centroid from cylinder pressure transducer <NUM>. Additionally, brake specific carbon dioxide processor <NUM> is configured to calculate a brake specific carbon dioxide value from the level of exhaust carbon dioxide received. The brake specific carbon dioxide value is calculated using Formula I below, where mfexhCO2 is the mass flow of CO<NUM> in exhaust, Brk_pwr is the brake power of the engine, MWCO<NUM> is the molecular weight of CO<NUM>, MWexh is the molecular weight of theoretical exhaust, mfexh is the mass flow of exhaust, and CO<NUM>ppm is the CO<NUM> concentration measured by the exhaust carbon dioxide sensor <NUM>.

Referring to <FIG>, methane number determiner <NUM>, within controller <NUM>, may be used to determine a methane number of fuel used within engine <NUM>. The relationship by which the methane number can be determined is shown by plotting the determined brake specific carbon dioxide values against centroids/locations of peak performance, as shown in <FIG>. Methane determiner <NUM>, includes a programmable table <NUM>, shown in <FIG>, which is programmed with the relationships shown in <FIG> such that table <NUM> may correlate a determined brake specific carbon dioxide value and the centroid and/or the location of peak pressure with an associated methane number of the fuel.

With further reference to <FIG> and <FIG>, air-fuel ratio determiner <NUM> within controller <NUM> may be used to determine an optimized air-fuel ratio. Determiner <NUM> includes a programmable table <NUM> that is programmed with the hydrogen/carbon ratios of methane numbers, such that the table <NUM> correlates the determined methane number with an associated optimized air-fuel ratio. The optimized air-fuel ratio may then be used by fueling regulator <NUM> of controller <NUM> to adjust an engine performance parameter. The air-fuel ratio is adjusted by changing the fuel control valve position that controls the amount of fuel that is sent to the engine. Fueling regulator <NUM> may adjust the engine performance parameter by sending a target value to adjusting mechanism <NUM>. In an exemplary embodiment, the engine performance parameter adjusted is the fuel quantity provided to mixer <NUM>, and adjusting mechanism <NUM> is a fuel control valve. It should be understood that tables <NUM>, <NUM>, while described as being incorporated into controller <NUM>, may be stored or generated on one or more separate devices that are accessed by controller <NUM> or distributed among controller <NUM> and one or more separate devices. Additionally, it should be understood that someone of skill in the art with the benefit of the present disclosure could construct these or other suitable tables.

Referring back to <FIG>, engine system <NUM> may further include an inlet sensor <NUM> and a correcting processor <NUM>. Inlet sensor <NUM> may be positioned at any location upstream of cylinders of the engine. For instance, inlet sensor <NUM> may be positioned along fuel line <NUM> leading to mixer <NUM>, in the charge stream from mixer <NUM> to engine <NUM>, at a fuel inlet, at an inlet to mixer <NUM>, at an outlet of mixer <NUM>, at a turbocharger(s) inlet, at a turbocharger(s) outlet, at a charger air cooler(s) inlet, at a charger air cooler(s) outlet, or before or after one or more throttles or intake manifolds. Furthermore, inlet sensor <NUM> may be used to measure the level of intake carbon dioxide present in fuel being provided to engine <NUM>. Additionally, correcting processor <NUM> may be used to subtract the level of intake carbon dioxide from the level of exhaust carbon dioxide prior to calculating the brake specific carbon dioxide value using brake specific carbon dioxide processor <NUM> of controller <NUM>. In various embodiments, correcting processor <NUM> may be part of controller <NUM>. In various embodiments, as seen in <FIG>, inlet sensor <NUM> may be configured to transmit the level of inlet carbon dioxide directly to BSCO2 processor <NUM>. Thus, in various embodiments, BSCO2 processor <NUM> may include correcting processor <NUM>.

Referring now to <FIG>, a method <NUM> for self-adjusting engine performance in response to fuel quality variations using engine system <NUM> of the present disclosure is shown. At step <NUM> of method <NUM>, a level of exhaust carbon dioxide exiting engine <NUM> is sensed. At step <NUM>, a centroid and/or location of peak pressure in engine <NUM> is sensed. At step <NUM>, a brake specific carbon dioxide value is calculated from the level of exhaust carbon dioxide using correlations within controller <NUM>. At step <NUM>, a methane number of fuel used by engine <NUM> is determined from the determined brake specific carbon dioxide value and the centroid and/or location of peak pressure. At step <NUM>, an optimized air-fuel ratio is determined from the methane number. At step <NUM>, an engine performance parameter is adjusted in response to the optimized air-fuel ratio. In an exemplary embodiment, the engine performance parameter is the quantity of fuel supplied.

Referring to <FIG>, method <NUM> may further include the steps <NUM>,<NUM> and <NUM>. At step <NUM>, the methane number is monitored using methane number evaluator <NUM> of controller <NUM>. At step <NUM>, a level of inlet carbon dioxide of the fuel entering engine <NUM> is sensed. At step <NUM>, the determined brake specific carbon dioxide value is adjusted in response to the level of inlet carbon dioxide.

Controller <NUM> may be used to calculate the brake specific carbon dioxide value from the exhaust carbon dioxide level, determine the methane number of fuel used within the engine from the determined brake specific carbon dioxide value and the centroid or the location of peak pressure, determine the optimized air-fuel ratio from the methane number, and adjust an engine performance parameter based on the optimized air-fuel ratio.

While various embodiments of the disclosure have been shown and described, it is understood that these embodiments are not limited thereto. The embodiments may be changed, modified and further applied by those skilled in the art. Therefore, these embodiments are not limited to the detail shown and described previously, but also include all such changes and modifications.

However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements. The scope is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more. " Moreover, where a phrase similar to "at least one of A, B, or C" is used in the claims, it is intended that the phrase be interpreted to mean that A alone may be present in an embodiment, B alone may be present in an embodiment, C alone may be present in an embodiment, or that any combination of the elements A, B or C may be present in a single embodiment; for example, A and B, A and C, B and C, or A and B and C.

Claim 1:
A controller (<NUM>) for self-adjusting engine performance parameters in response to fuel quality variations, wherein the controller is configured to:
receive data that corresponds to a methane number of fuel used within the engine (<NUM>), the data comprising an exhaust carbon dioxide value;
calculate a brake specific carbon dioxide value based on the exhaust carbon dioxide value;
determine the methane number based on the brake specific carbon dioxide value using correlations accessed by the controller, the correlations relating the brake specific carbon dioxide value to at least one of a centroid of the engine and a location of peak pressure in the engine; and
adjust an engine performance parameter based on the methane number in response to fuel quality variations.