Patent Grant
11867141
The disclosure generally relates to the detection of ethanol in engine fuel and, more specifically, to the determination of the ethanol content of fuel with a heated component of an automotive engine fuel delivery system.
Flexible fuel vehicles (FFV's, which may also be referred to as flex-fuel, dual-fuel, total flex, flexifuel, hi-flex, or simply flex vehicles) are vehicles having an internal combustion engine that is capable of operation using both conventional vehicular fuel (e.g., unleaded gasoline) and an alternative fuel such as ethanol or methanol which are stored in the same fuel tank of the vehicle. The most common type of flexible fuel vehicle has an engine that can run on gasoline, gasoline-ethanol blends (e.g., E10, E20, E85), and/or pure ethanol (E100). E85, also known as flex fuel, is a gasoline-ethanol blend that includes up to 85% by volume anhydrous ethanol and in practice may contain between 51% to 85% anhydrous ethanol depending on the geographical region and seasonal temperatures. Other common gasoline-ethanol blends include E10 (containing a maximum of 10% anhydrous ethanol), E20 (containing a maximum of 20% anhydrous ethanol), E25 (containing a maximum of 25% anhydrous ethanol), E70 (containing a maximum of 70% anhydrous ethanol), and E75 (containing a maximum of 75% anhydrous ethanol). Pure ethanol (E100) contains no gasoline and is 100% hydrous ethanol, which contains an average of 5.3% by volume water and the balance ethanol. Due to its inherent water content, pure ethanol is sometimes referred to as E95.
The type/blend of fuel used in a flexible fuel vehicle can be varied based on the user's preference and availability of the various blends described above. For example, a user may fill the fuel tank of a flexible fuel vehicle with gasoline, and later when the tank is empty and/or in need of refilling, may instead next fill the tank with E85 fuel. The user thus may freely switch between gasoline (which in its pure form contains no ethanol, but as presently sold at the gas pump in the United States, may contain up to 10% ethanol) and E85, which is more than half ethanol. As shown by example in
Conventionally, the ethanol content of the fuel stored in the vehicle's fuel tank is detected and measured using an ethanol sensor located at the fuel line or by the oxygen (02) sensor located in the engine's exhaust system. The ethanol content may also be measured indirectly in other ways, such as by measuring the electrical capacitance of the fuel. However, given the significant lag time in a vehicle learning the ethanol content of fuel by conventional methods (for example, the oxygen sensor measures the mixture after burn) and the potential undesirable effects of this lag time, there is a need for an alternative method of determining the ethanol content of fuel used in flexible fuel vehicles.
A method of detecting a percentage of ethanol in fuel used by an engine is provided. The method includes initiating a heating cycle in a component of a fuel delivery system of the engine, the component including a heater. The method further includes monitoring the temperature of the heater as a function of time, the heater being operated during the heating cycle. The method further includes obtaining the heater temperature at a first time t1 at which a slope of the heater temperature as a function of time reaches a predetermined threshold value indicative of fuel boiling. The method further includes obtaining the heater temperature at a subsequent time t2 at which the slope of the heater temperature approaches a value of the slope prior to the time t1 and which is greater than the predetermined threshold value indicative of fuel boiling. The method further includes calculating a difference ΔT between the heater temperature at time t2 and the heater temperature at the first time t1. The method further includes determining the percentage of ethanol in the fuel as a function of the calculated temperature difference ΔT and the first time t1.
In specific embodiments, the heating cycle is initiated prior to ignition of the engine.
In specific embodiments, the heating cycle is initiated after a refueling event.
In specific embodiments, the component is a heated fuel injector.
In particular embodiments, the heater heats a body of the heated fuel injector.
A method of detecting a percentage of ethanol in fuel used to operate an engine of a flexible fuel vehicle is also provided. The method includes initiating a heating cycle in a heated fuel injector of the engine, the heated fuel injector including a heater that is operated during the heating cycle. The method further includes monitoring the temperature of the heater of the heated fuel injector as a function of time. The method further includes obtaining the heater temperature at a first time t1 at which a slope of the heater temperature as a function of time reaches a predetermined threshold value indicative of fuel boiling. The method further includes obtaining the heater temperature at a subsequent time t2 at which the slope of the heater temperature approaches a value of the slope prior to the time t1 and which is greater than the predetermined threshold value indicative of fuel boiling. The method further includes calculating a difference ΔT between the heater temperature at time t2 and the heater temperature at the first time t1. The method further includes determining the percentage of ethanol in the fuel as a function of the calculated temperature difference ΔT and the first time t1 at which there was a change in slope.
In specific embodiments, the heating cycle includes heating a body of the heated fuel injector over a period of time.
In specific embodiments, the heating cycle is initiated after adding fuel to a fuel tank of the flexible fuel vehicle.
In specific embodiments, the heating cycle is initiated prior to ignition of the engine.
In specific embodiments, duration of the heating cycle is between 5 and 10 seconds.
In specific embodiments, the percentage of ethanol is determined by the following equation (I): % ethanol in fuel=C+αt1−β(ΔT).
In particular embodiments, C is 49.95±2.50, α is 5.22±0.26, and β is 2.8319±0.1416.
In particular embodiments, the numerical values of the formula are determined based on an empirical linear regression using experimental data points obtained from known ethanol concentrations of fuel.
In specific embodiments, a margin of error of the determined percentage of ethanol in the fuel is ±15%.
In specific embodiments, the steps of the method are performed by a fuel heater control module of the flexible fuel vehicle.
A fuel delivery system of an engine is also provided. The fuel delivery system includes a heated fuel injector including a heater and a body that is heated by the heater. The system further includes a fuel tank that stores fuel, and a fuel module that delivers the fuel from the tank to the heated fuel injector. A fuel heater control module controls the heater of the heated fuel injector. The fuel heater control module detects a percentage of ethanol in the fuel used to operate the engine by the method described herein.
A flexible fuel vehicle is also provided. The flexible fuel vehicle includes an engine and a fuel delivery system that delivers fuel to the engine. The fuel delivery system includes a heated fuel injector including a heater that heats a body. The fuel delivery system further includes a fuel heater control module that controls the heater of the heated fuel injector. The fuel heater control module detects a percentage of ethanol in fuel used to operate the engine by the method described herein.
A non-transitory computer readable medium storing a program that causes a controller to execute the method of detecting a percentage of ethanol in fuel used to operate an engine of a flexible fuel vehicle is also provided.
Various advantages and aspects of this disclosure may be understood in view of the following detailed description when considered in connection with the accompanying drawings, wherein:
A method of detecting a percentage of ethanol in fuel used by an engine, as well as a fuel delivery system and a flexible fuel vehicle that detects the content of ethanol in fuel according to the method, are provided. Referring to
Turning first to
As shown in detail in
The heated fuel injector 22 also includes an integral temperature sensing element or similar that is configured to determine a temperature of the injector heater element 80. In a non-limiting example, the integral temperature sensing element may be a temperature dependent electrical device such as a thermistor 84. The thermistor 84 generally exhibits a resistance value that corresponds to a thermistor temperature of the thermistor 84. The thermistor 84 may also be formed of thick film material applied using methods similar to those used to apply thick film material to form the heater element 80. The thermistor 84 may also be a discrete electrical component such as a positive temperature coefficient (PTC) or negative temperature coefficient (NTC) device attached using solder or the like. The location of the thermistor 84 shown in
The fuel heater control module 42 and engine control module 44 individually or together constitute a controller. As such, the controller may include a microprocessor or other control circuitry such as an application specific integrated circuit (ASIC) as would be evident to those skilled in the art. The controller also may include memory, including random-access memory (RAM) as well as non-volatile memory, such as electrically erasable programmable read-only memory (EEPROM), masked read only memory (ROM), or flash memory for storing one or more software routines, thresholds, and captured data. The one or more software routines, including the method of detecting the ethanol content of fuel, may be executed by the microprocessor to control the engine components including the heater fuel injector 22. The controller may also include analog to digital (ND) convertor circuits and digital to analog (D/A) convertor circuits to allow the convertor to establish electrical communication with devices outside the controller, such as the sensors described above. The controller may also include power supply circuitry.
In step 102, a heating cycle is initiated in the heated fuel injector 22. The heating cycle includes operating the heater element 80 by supplying an electric current to the heater element 80, which causes the heater element 80 to generate heat and generally increase in temperature. Warming of the heater element 80 heats the body 78 of the heated fuel injector 22 which in turn raises the temperature of the fuel in the injector body 78 adjacent a tip portion 86. The heating cycle may be initiated at any time but preferably after a refueling event in which the controller detects that fuel has been added to the fuel tank 24, such as via a fuel level sensor 31 of the fuel module 28 in the fuel tank. Alternatively or in addition, the heating cycle may be initiated prior to ignition of the engine 26, e.g. just before start-up of the engine, for example triggered by the opening of the driver-side door, so that the ethanol content of the fuel may be determined prior to ignition with no start-up delay for the driver/operator so that engine operation parameters may be properly adjusted by the controller based on the determined ethanol content. As used herein, engine start-up is the time period from an initial or priming injection event until the engine speed reaches a predetermined engine speed threshold, usually an engine idle speed typically between 600 and 1000 revolutions per minute (RPM). Furthermore, a heating cycle also may be initiated at any time during engine operation to periodically measure the fuel ethanol content. The duration of the heating cycle itself is long enough to raise the temperature of the heater element 80 above the boiling temperature of at least one component of the fuel, for example the boiling temperature of ethanol which is 79° C., and for vaporization of the fuel to begin. In some embodiments, the heating cycle duration is between 3 and 10 seconds. In other embodiments, the heating cycle duration is between 5 and 10 seconds, 3 and 7 seconds, or 5 and 7 seconds.
In step 104, during the heating cycle the temperature of the heater element 80 of the heated fuel injector 22 is monitored as a function of time, such as a function of the elapsed time of the heating cycle. The temperature of the heater element 80 may be obtained from the temperature sensing element 84 and may be temporarily recorded in the memory of the controller as a function of the heating cycle time. The temperature of the heater element 80 will continue to rise until vaporization (boiling) of the fuel in the heated fuel injector begins to occur. Table 1 below shows that the specific heats of gasoline and ethanol are similar. Therefore, the initial heating phase before boiling cannot easily discriminate different fuel compositions. The heats of vaporization and boiling points, however, are quite different, which is useful for distinguishing between various fuel compositions. Pure ethanol boils at 79° C., and shows a temperature plateau while vaporization occurs, since heat energy at boiling is used to vaporize the liquid instead of heating it further. On the other hand, the many components of gasoline boil over a range of 25° C. to 175° C. They do not show the expected vaporization plateau, since they have many tiny plateaus which give the overall appearance of continuity across the temperature range of interest. But fuels with significant amounts of ethanol begin to show features of the behavior of pure ethanol, with the pure-substance behavior growing progressively more dominant as ethanol content increases.
The heater element 80 temperature responds to heat transfer factors, for example the formation and persistence of fuel vapor bubbles on the heater surface, a factor that does not affect the bulk fuel temperature.
The bulk fuel experiences a temperature rise based on its specific heat capacity until the phase transition to vapor begins. Since vaporization is endothermic, the temperature of the fuel will not rise further until all the fuel is vaporized. Thus, in the bulk fuel a temperature rise is followed by a temperature plateau, followed by the resumption of temperature rise. The behavior of the monitored heater temperature generally follows this pattern.
In step 106, the controller obtains from the monitored heater element temperature the measured heater temperature at a first time t1 at which a slope of the heater temperature as a function of time reaches a predetermined threshold value indicative of fuel boiling (i.e. the “vaporization plateau”). It will be appreciated that the slope of the temperature vs. time characteristic may alternatively be referred to as the time rate of change of the temperature, or as the derivative of the temperature with respect to time. Further, the change in slope of the heater temperature as a function of time may alternatively be referred to as the time rate of change of the slope of the temperature, or as the derivative of the slope of the temperature with respect to time. As described above, the heater temperature increases to the point where boiling first occurs, at which point (first time t1) the slope of the temperature vs. time characteristic undergoes a sharp, sometimes abrupt reduction depending on the ethanol content of the fuel. Depending on the ethanol content, at first time t1 the slope may undergo an inflection where it changes from positive to negative, or for lesser ethanol content (i.e. closer to pure, straight gasoline) there is abrupt decrease in the slope such that the rate of change of the slope undergoes an abrupt negative decrease. In any event, at the beginning of boiling, the slope becomes less than zero, becomes zero, or decreases to a value that is approaching zero such that the slope is less than a predetermined threshold value that is near zero, and the rate of change of the slope is negative, i.e. the slope is decreasing with time. Hence, in step 106 the slope of the temperature vs. time characteristic is compared to a predetermined threshold value which is indicative of fuel boiling, the predetermined threshold value being a positive slope close to but slightly zero, a zero value slope, or even a slope that is less than zero.
At the inception of boiling, latent heat energy is absorbed to allow the fuel to change from liquid phase to vapor phase. While this phase change is subsequently underway, the fuel temperature is essentially constant, at the boiling point of the fuel being vaporized. In step 108, the controller obtains from the monitored heater element temperature the measured heater temperature at a subsequent time t2 at or after which the slope of the heater temperature has approached a value of the slope prior to the change in slope at time t1. The slope of the heater temperature approaching the slope prior to the slope at the first time t1 means that the slope has changed from zero or near zero to a positive value that is close to the prior slope and that is greater than the predetermined threshold value, or that the rate of change of the slope has undergone a positive increase. The point at time t2 corresponds to a point at which all the fuel is vaporized (stabilized film boiling) and there is a resumption in the rise in temperature as shown in
In step 110, a temperature difference (ΔT) between the obtained heater temperature at time t2 and the obtained heater temperature at the first time t1 is calculated. As shown in
% Ethanol in fuel=C+αt1−β(ΔT)
wherein the constant C and coefficients α and β are obtained by linear regression of empirical data points obtained from various known ethanol contents such as E100, E60, and E20. A fitted line plot of these data points including confidence interval and population interval boundaries is shown in
It is to be understood that the appended claims are not limited to express and particular compounds, compositions, or methods described in the detailed description, which may vary between particular embodiments which fall within the scope of the appended claims. With respect to any Markush groups relied upon herein for describing particular features or aspects of various embodiments, different, special, and/or unexpected results may be obtained from each member of the respective Markush group independent from all other Markush members. Each member of a Markush group may be relied upon individually and or in combination and provides adequate support for specific embodiments within the scope of the appended claims.
Further, any ranges and subranges relied upon in describing various embodiments of the present invention independently and collectively fall within the scope of the appended claims, and are understood to describe and contemplate all ranges including whole and/or fractional values therein, even if such values are not expressly written herein. One of skill in the art readily recognizes that the enumerated ranges and subranges sufficiently describe and enable various embodiments of the present invention, and such ranges and subranges may be further delineated into relevant halves, thirds, quarters, fifths, and so on. As just one example, a range “of from 0.1 to 0.9” may be further delineated into a lower third, i.e., from 0.1 to 0.3, a middle third, i.e., from 0.4 to 0.6, and an upper third, i.e., from 0.7 to 0.9, which individually and collectively are within the scope of the appended claims, and may be relied upon individually and/or collectively and provide adequate support for specific embodiments within the scope of the appended claims. In addition, with respect to the language which defines or modifies a range, such as “at least,” “greater than,” “less than,” “no more than,” and the like, it is to be understood that such language includes subranges and/or an upper or lower limit. As another example, a range of “at least 10” inherently includes a subrange of from at least 10 to 35, a subrange of from at least 10 to 25, a subrange of from 25 to 35, and so on, and each subrange may be relied upon individually and/or collectively and provides adequate support for specific embodiments within the scope of the appended claims. Finally, an individual number within a disclosed range may be relied upon and provides adequate support for specific embodiments within the scope of the appended claims. For example, a range “of from 1 to 9” includes various individual integers, such as 3, as well as individual numbers including a decimal point (or fraction), such as 4.1, which may be relied upon and provide adequate support for specific embodiments within the scope of the appended claims.
The above description is that of current embodiments of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents. This disclosure is presented for illustrative purposes and should not be interpreted as an exhaustive description of all embodiments of the invention or to limit the scope of the claims to the specific elements illustrated or described in connection with these embodiments. For example, and without limitation, any individual element(s) of the described invention may be replaced by alternative elements that provide substantially similar functionality or otherwise provide adequate operation. This includes, for example, presently known alternative elements, such as those that might be currently known to one skilled in the art, and alternative elements that may be developed in the future, such as those that one skilled in the art might, upon development, recognize as an alternative. Further, the disclosed embodiments include a plurality of features that are described in concert and that might cooperatively provide a collection of benefits. The present invention is not limited to only those embodiments that include all of these features or that provide all of the stated benefits, except to the extent otherwise expressly set forth in the issued claims. Any reference to claim elements in the singular, for example, using the articles “a,” “an,” “the” or “said,” is not to be construed as limiting the element to the singular.
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| Number | Date | Country |
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| 209656487 | Nov 2019 | CN |
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| De Oliveira Jr. et al., “Ethanol Sensor using the Critical Heat Flux (CHF) Principle,” SAE Technical Paper Series 2011-36-0115, SAE Brasil 2011 Congress and Exhibition (2011). |
