JP2007297951A - Gas fuel internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve thermal efficiency of an internal combustion engine using reformed gas fuel as main fuel. <P>SOLUTION: This engine is provided with at least reforming catalyst 230 reforming liquid fuel to gas fuel containing a plurality of gas components, an evaporator 220 for supplying gasified fuel to the reforming catalyst 230, a flow rate sensor 140 detecting flow rate of liquid fuel to the evaporator 220, and a catalyst temperature sensor 146 detecting reformed catalyst temperature. When liquid fuel is reformed by steam, water flow rate detection is also executed. An ECU 100 estimates reformed gas composition by using at least detection values of a flow rate sensor and a catalyst temperature sensor and referring a corresponding map of gas composition and a detection value stored inside. An estimated value is corrected according to measured specific gas composition concentration in the reformed gas and a detection value of temperature of input and output gas to and from the catalyst. The ECU 100 operates lean combustion limit concentration of air fuel mixture in a cylinder based on the estimated vale, and always materializes operation in a vicinity of lean combustion limit by controlling gas fuel supply quantity and air flow rate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an internal combustion engine using gas fuel obtained by reforming as a main fuel.

By reforming hydrocarbon-based (C _m H _n ) liquid fuel such as gasoline, gas fuel with a large calorific value is obtained and used as fuel for internal combustion engines to improve engine thermal efficiency. Has been proposed. In addition, in an internal combustion engine, it is necessary to bring the supply amount of fuel and air into the cylinder close to the stoichiometric air-fuel ratio in order to realize an engine with good combustion efficiency, and an optimum air amount corresponding to the fuel to be used is set in the cylinder. Control to supply to

  Therefore, even in the gas fuel internal combustion engine, it is required to perform control so as to obtain an optimum air amount corresponding to the gas fuel. Therefore, in a conventionally known reformed gas engine, attention is paid to hydrogen contained in the reformed gas fuel obtained by reforming hydrocarbon-based fuel, and the hydrogen concentration is measured, and the cylinder is determined based on the measured concentration. The amount of air supplied to the inside and the amount of gas fuel are controlled (see Patent Document 1 below).

JP 2002-221098 A JP 2004-251273 A

  In Patent Document 1, the stable combustion range of the internal combustion engine is estimated from the measurement of the hydrogen concentration in the reformed gas fuel, and the amount of air and the amount of fuel supplied to the engine cylinder are controlled. For example, in Patent Document 1, it is estimated that the methane number in the supply gas fuel is too small in the occurrence of knocking, and control such as reducing the supply amount of hydrogen separately obtained from the reformer by the separator is performed. It is running.

  However, the gas fuel obtained by reforming the liquid fuel is not composed of only hydrogen, but contains hydrogen, carbon monoxide, carbon dioxide, and methane as main components. Further, the lean limit equivalent ratio of each component is different, hydrogen is diluted limit equivalent ratio (φlimit) = 0.1, carbon monoxide is φlimit = 0.34, carbon dioxide (does not function as fuel), Methane has an equivalent ratio of φlimit = 0.5, which is necessary for combustion. Therefore, it is difficult to grasp the lean combustion limit of an internal combustion engine only from the hydrogen concentration.

  Further, the composition of the reformed gas fuel varies depending on the reforming conditions, and depending on the conditions, there are cases where the amount of hydrogen produced is small and methane is produced in large quantities. For this reason, it may be difficult to estimate the lean combustion limit only from the measurement of the hydrogen concentration in the gas fuel, and it is difficult to always satisfy the torque required by the driver using the minimum amount of gas fuel. There are restrictions on improving fuel efficiency.

  Further, in Patent Document 2 above, hydrocarbon fuel and air are reformed by a reformer to generate a reformed gas containing carbon monoxide and hydrogen, but depending on the temperature of the reforming catalyst of the reformer. Since the reforming conditions change, it is described that the supply amounts of hydrocarbon fuel and air to the reformer are controlled so that the reforming efficiency is within a predetermined range. However, there is no consideration at all about the composition of the reformed gas produced. In other words, since reforming is always performed so that the reforming efficiency is within a predetermined range, it is assumed that the composition of the gas fuel supplied into the cylinder is always within a certain range, and the actually generated reformation is performed. There is no need to consider what the quality gas composition actually will be. However, in various environments, it is difficult to always satisfy the optimum reforming conditions, and the reformed gas composition actually changes. And even in such a situation, it is desired to be an internal combustion engine with good thermal efficiency and fuel efficiency.

  The present invention aims to improve thermal efficiency in an internal combustion engine that uses gas fuel obtained by reforming as a main fuel.

  The present invention relates to an internal combustion engine that uses gas fuel as fuel, a reforming catalyst that reacts liquid fuel with water to reform the gas fuel containing a plurality of gas components, and uses the liquid fuel as the reforming catalyst. An evaporator for turning the liquid fuel and water into steam before supply, a flow sensor for detecting the flow rate of liquid fuel and water supplied to the evaporator, and a gas for detecting gas temperature in the reforming catalyst A temperature sensor; a catalyst temperature sensor that detects a temperature of the reforming catalyst; and a detector that detects a concentration of at least one gas component of the plurality of gas components of the reformed gas fuel. . The engine control unit uses the detection values of the flow rate sensor and the catalyst temperature sensor to refer to the correspondence map between the detection value stored in advance and the gas composition, and the gas composition of the gas fuel obtained by reforming Further, the predicted value of the gas composition is corrected based on the detected concentration of the gas component.

  In another aspect of the present invention, the internal combustion engine further includes a gas temperature sensor that detects a gas temperature of an input gas or an output gas of the reforming catalyst, and the engine control unit is further configured to predict the gas composition, The detected gas temperature is used.

  In another aspect of the present invention, in the internal combustion engine, in the correction of the predicted value of the gas composition, the concentration of the detected gas component is set to the concentration of the corresponding gas component in the predicted value, and the detected concentration of the gas component is entirely set. Based on the value removed from the concentration, the remaining gas component concentration of the predicted value is calculated.

  In another aspect of the present invention, there is provided an internal combustion engine that uses a gas fuel as a main fuel, the reforming catalyst that reacts the liquid fuel with water to reform the gas fuel containing a plurality of gas components, and the liquid fuel. An evaporator for converting the liquid fuel and the water into steam before being supplied to the reforming catalyst, a flow sensor for detecting a flow rate of liquid fuel and water supplied to the evaporator, and an input of the reforming catalyst A gas temperature sensor for detecting a gas temperature of the gas or the output gas; and a catalyst temperature sensor for detecting a temperature of the reforming catalyst. The engine control unit refers to a correspondence map between the detection value stored in advance and the gas composition based on the detection values of the flow rate sensor and the catalyst temperature sensor, and determines the gas composition of the gas fuel obtained by reforming. A predicted value is obtained, and further, the predicted value is corrected based on the detection result of the gas temperature sensor.

  The correction of the predicted value is based on the first predicted value obtained based on the detected value at the flow rate sensor and the catalyst temperature sensor, and the detected value stored in advance based on the flow rate sensor and the detected gas temperature. And the second predicted value obtained by referring to the correspondence map between the gas composition and the gas composition.

  In another aspect of the present invention, there is provided an internal combustion engine that uses gas fuel as a main fuel, a reforming catalyst that reforms liquid fuel into gas fuel containing a plurality of gas components by reaction, and the liquid fuel is reformed. An evaporator for converting the liquid fuel into vapor before being supplied to the catalyst, a flow sensor for detecting a flow rate of the liquid fuel supplied to the evaporator, and a catalyst temperature sensor for detecting the temperature of the reforming catalyst, Prepare. The engine control unit uses at least the detection values of the flow rate sensor and the catalyst temperature sensor to refer to the correspondence map between the detection value stored in advance and the gas composition, and the gas fuel gas obtained by reforming The composition is predicted, the lean combustion limit concentration of the mixture in the cylinder is calculated based on each lean combustion limit concentration of the combustible gas composition of the predicted gas composition, and the lean combustion limit concentration and the required torque are calculated. Accordingly, the amount of gas fuel supplied to the cylinder and the air flow rate are controlled.

  In another aspect of the present invention, the liquid fuel is a hydrocarbon-based liquid fuel, and the gas fuel obtained by the reforming contains hydrogen, carbon monoxide, carbon dioxide, and methane.

  When a reformed gas is obtained using a reforming catalyst for liquid fuel, the composition of the reformed gas changes according to the reforming conditions, thereby changing the lean combustion limit of the air-fuel mixture in the cylinder. In the present invention, even if the composition of the reformed gas changes in this way, the liquid fuel flow rate, the wall temperature of the reforming catalyst, and the like are measured, and the composition of the reformed gas is predicted based on the measurement results. Therefore, even if the reforming conditions change, it is possible to always predict a composition close to the actually obtained composition and perform control according to this.

  In the present invention, for the predicted value, the concentration of at least one gas component of the obtained reformed gas is detected, and the predicted value is corrected based on the detected value, or the input gas to the reforming catalyst or By detecting the temperature of the output gas and correcting the predicted value in consideration of the detected value, higher prediction accuracy is possible.

  Thus, since the gas composition is predicted with high accuracy, it becomes possible to more accurately calculate the lean combustion limit determined according to the gas composition, and the amount of air supplied to the engine cylinder so as to be the lean combustion limit, The injection amount of the reformed gas can be appropriately controlled, and it is possible to always operate near the lean limit.

Here, the thermal efficiency η of the internal combustion engine is
η = 1− (1 / ε ⁽ κ ⁻¹⁾ ) (i)
(Ε: compression ratio, κ: specific heat ratio of working gas). If the compression ratio is the same, the specific heat ratio κ of the working gas (combustion gas) increases as it is burned under a lean condition, so that the thermal efficiency is improved. That is, in the present invention, since it is possible to always burn near the lean limit, it is possible to provide an internal combustion engine with very high thermal efficiency.

  Embodiments (hereinafter, embodiments) of the present invention will be described below with reference to the drawings.

  [Outline of Embodiment]

  The internal combustion engine according to the present embodiment is an internal combustion engine that uses gas fuel as a main fuel, and the gas fuel is a reformed gas fuel containing a plurality of gas components obtained by reforming liquid fuel with a reforming catalyst. . As the liquid fuel, a hydrocarbon-based liquid fuel can be employed, and examples thereof include gasoline, methanol, ethanol, light oil, and heavy oil. The gas component obtained by reforming such hydrocarbon liquid fuel is, for example, when gasoline or the like is adopted as the liquid fuel and reformed with water (steam reforming method), hydrogen, carbon monoxide A reformed gas mainly composed of carbon dioxide and methane is obtained. Alternatively, liquid organic compound fuel (hydrocarbon liquid fuel as described above), water, and air are supplied to the reformer, and hydrogen, carbon monoxide, carbon dioxide, methane, and nitrogen are the main components. It is also possible to obtain a reformed gas.

  In such an internal combustion engine, in addition to the reforming catalyst for reforming the liquid fuel, an evaporator is provided for converting the liquid fuel and water into steam before supplying the liquid fuel to the reforming catalyst. Furthermore, a flow rate sensor for detecting the flow rate of liquid fuel and water supplied to the evaporator and a catalyst temperature sensor for detecting the temperature of the reforming catalyst (particularly the wall temperature of the reforming catalyst) are provided.

  The engine control unit (ECU: electronic control unit) uses at least the detection values of the flow rate sensor and the catalyst temperature sensor, refers to the correspondence map between the detection value and the gas composition stored in advance, and performs reforming. Predict the gas composition of the resulting gas fuel. In addition, it is more preferable to correct this predicted value by using another detected value, as will be described in a specific example described later.

Next, the ECU calculates the following formula (1) from the concentration of the gas component (combustible gas component) serving as fuel in the gas composition and the combustion limit of the air-fuel mixture.
L = 100 / (Σ (M _i / N _i )) (1)
L (vol%): mixed reformed gas - air mixture in the combustion limit concentration N _i (vol%) of the air: the fuel gas component - mixture in the combustion limit concentration M _i (vol%) of the air: mixed reformed gas The concentration of each fuel gas component is calculated, and the combustion limit L of the mixture of mixed reformed gas and air is obtained.

  As described above, in the present embodiment, the gas composition is predicted based on the actually measured values such as the flow rate and the catalyst temperature, and the lean combustion limit concentration L of the entire reformed gas that changes depending on the gas composition is obtained. Further, the ECU controls the reformed gas supply amount and the air flow rate into the engine cylinder according to the obtained lean combustion limit concentration L and the torque required by the driver.

  FIG. 1 shows an example of a reformed gas composition obtained when the wall temperature (° C.) of the reforming catalyst is changed, gasoline is used as the liquid fuel, and this is steam reformed. As described above, the main components of the reformed gas are hydrogen, carbon monoxide, carbon dioxide, methane, and water (which is later removed by the aggregator). As can be understood from FIG. The composition differs greatly. Among these generated gases, the combustible gases are hydrogen, carbon monoxide, and methane. As described above, the hydrogen lean limit equivalent ratio (φlimit) = 0.1, and carbon monoxide is φlimit = 0. .34, methane, φlimit = 0.5, and the respective dilution limits are greatly different. Therefore, for example, in FIG. 1, under a situation where the reforming catalyst wall temperature is high and the composition ratio of hydrogen and carbon monoxide is very large, combustion is possible even in a situation where hydrogen is very lean. The lean burn limit equivalent ratio is very small (thin). Conversely, when the wall temperature is low, the amount of hydrogen and carbon monoxide is small, and the amount of methane is large, the lean limit equivalent ratio of methane is large, so the lean combustion limit equivalent ratio of the mixture in the cylinder is the same as when the wall temperature is high. When compared, it becomes very large (dark). For this reason, the gas fuel supply amount and the air amount to be supplied into the cylinder in order to execute the operation near the lean combustion limit should be different.

  In the present embodiment, at least the liquid fuel flow rate, the water flow rate, and the reforming catalyst temperature are detected, and the gas composition is predicted using the detected flow rate, whereby accurate composition prediction is possible, and the ECU responds to the composition. The lean combustion limit concentration is calculated, and the amount of reformed gas injected into the cylinder and the air flow rate are controlled so as to obtain the concentration. Of course, as will be described later, the lean combustion limit can be predicted more accurately by measuring the input gas temperature and the output gas temperature to the reforming catalyst and predicting the gas composition in consideration of the measured values. . Therefore, in the internal combustion engine of the present embodiment, the air-fuel mixture can always be burned in the vicinity of the lean limit in the cylinder, high thermal efficiency can be achieved, and fuel consumption can be improved.

  As described above, when an organic compound fuel is reformed using water and air, the air undergoes a combustion reaction with the organic compound fuel or product gas, and a reforming reaction (endothermic reaction) which is a main reaction. Reduce the amount of heat absorbed. By such a combustion reaction, all the oxygen in the air disappears, and the remaining nitrogen remains in the reformed gas (product gas) supplied into the cylinder.

[Specific Example 1]
FIG. 2 shows a schematic configuration of the internal combustion engine 10 according to the first specific example of the present embodiment. An ignition plug 60, an intake valve 24, and an exhaust valve 26 are provided in the vicinity of the upper portion of the cylinder 110, and a piston that moves up and down along the cylinder axis and is connected to the crankshaft by a connecting rod is provided in the cylinder 110. It has been. The intake pipe 20 is provided with a throttle valve 22 to control the intake air amount of the cylinder 110. Further, an air flow sensor 132 that measures the flow rate of air passing through the vicinity of the valve and outputs an air flow meter signal is provided near the throttle valve 22. Further, a gas fuel injection valve 130 for injecting reformed gas fuel is provided near the intake port of the intake pipe 20. The exhaust port of the cylinder 110 is connected to the exhaust pipe 30, and an exhaust catalyst 28 made of a three-way catalyst or the like is installed at the end.

  The hydrocarbon liquid fuel (for example, gasoline) stored in the fuel tank 40 and the water stored in the water tank 50 are respectively pumped up by a pump and supplied to the evaporator 220. In the evaporator 220, these are converted into steam, which are respectively sent to the reforming catalyst 230, and the hydrocarbon fuel gas is reformed by steam in the reforming catalyst 230, and mainly contains hydrogen, carbon monoxide, carbon dioxide, and methane. A reformed gas is generated. Note that the evaporator 220 and the reforming catalyst 230 perform vaporization and reforming processing by heating fuel and water using exhaust heat, a heater, or a burner, as will be described later. The reformed gas obtained by the reforming catalyst 230 is then dehydrated by the aggregator 240, stored in the reformed gas tank 250, pressurized to a desired pressure by the pump 260, and sucked from the gas fuel injection valve 130. Supplied to the tube 20.

  Between the tanks 40, 50 and the evaporator 220, a liquid fuel flow sensor 140 that detects the flow rate of hydrocarbon fuel (liquid) pumped from the fuel tank 40 and supplied to the evaporator 220, and a water tank A water flow rate sensor 142 that detects the flow rate of water drawn from 50 and supplied to the evaporator 220 is provided.

  Between the evaporator 220 and the reforming catalyst 230, an input gas temperature sensor 144 for detecting the fuel gas temperature input to the reforming catalyst 230 and the water vapor temperature is provided, and the output side ( An output gas temperature sensor 148 that detects the gas temperature of the gas (reformed gas) output from the reforming catalyst 230 is provided between the coagulator 240 and the aggregator 240. The gas temperature sensors 144 and 148 may be only one of them, for example, only the sensor 144 that detects the input gas temperature.

  The reforming catalyst 230 is provided with a catalyst temperature sensor 146 for measuring the temperature of the catalyst (catalyst wall temperature). Further, a gas concentration sensor 150 that detects a specific gas component concentration of the reformed gas output from the reforming catalyst 230 is provided between the reforming catalyst 230 and the aggregator 240.

  The gas composition of the reformed gas is strongly influenced by the hydrocarbon flow rate, water flow rate, and reforming catalyst temperature supplied to the evaporator 220. Also, the input gas temperature has a great influence on the gas composition. Furthermore, since the output gas temperature also changes due to the reforming reaction in the reforming catalyst, the reforming condition can be estimated from the value. Therefore, in the specific example 1, as described above, the hydrocarbon liquid fuel flow rate, the water flow rate, the reforming catalyst temperature, the input gas temperature, and the output gas temperature are detected by the sensors 140, 142, 146, 144, and 148, respectively. .

The ECU 100 performs a prediction calculation of the lean combustion limit in the cylinder 110 based on the detection values obtained by the respective sensors. Hereinafter, the arithmetic processing in the ECU 100 will be described with further reference to FIG. The ECU 100 receives detection values of the hydrocarbon flow rate, the water flow rate, the reforming catalyst temperature, the input gas temperature, and the output gas temperature from each sensor as described above (S1), and based on these values, With reference to the correspondence map between the detected value and the gas composition stored in advance, the gas composition and its concentration (vol%) of the generated reformed gas are predicted (M ₁ , M ₂ , M ₃ , M ₄ ···) (S2).

The gas concentration sensor 150 detects a predetermined gas concentration M ₁ ′ (vol%) of one component of hydrogen, carbon monoxide, carbon dioxide, and methane among the main components of the reformed gas (S3). ). The ECU 100 uses the detected concentration M ₁ ′ to obtain correction values M ₁ ″ M ₂ ″, M ₃ ″, M ₄ ″... For each gas component concentration based on the following formula (S4).

M ₁ ”= M ₁ '
M ₂ ″ = (1−M ₁ ′) M ₂ / (M ₂ + M ₃ + M ₄ )
M ₃ ″ = (1−M ₁ ′) M ₃ / (M ₂ + M ₃ + M ₄ )
M ₄ ″ = (1−M ₁ ′) M ₄ / (M ₂ + M ₃ + M ₄ )
That is, the corresponding gas component concentration M ₁ obtained from the map is replaced with the detected concentration M ₁ ′ to obtain the corrected concentration M ₁ ″ for the M ₁ component. The remaining components M ₂ , M ₃ , M _4. ... Is calculated in accordance with the overall concentration (volume) ratio of each component concentration obtained from the map within the concentration (volume) obtained by subtracting the detected gas component concentration (volume) from the overall concentration (volume).

Next, the thus obtained modified each component concentration M ₁ of the gas _{", M 2", M 3} ", M 4" inside, on the basis of the lean combustion limit concentration N _i of the combustion gases, L as described above = 100 / (Σ (M _i / N _i )) (1)
Formula (1) is calculated (S5). Thereby, the lean combustion limit concentration L (vol%) of the air-fuel mixture in the cylinder 110 can be obtained, and the ECU 100 determines the lean combustion limit concentration L and the required torque requested from the driver at this time. The amount of gas fuel to be supplied to the cylinder 110 and the air flow rate are determined, and the fuel injection period in the fuel injection valve 130 and the opening of the throttle valve 22 are controlled according to the amounts (S6). The opening degree of the throttle valve 22 is controlled so that the output from the air flow sensor 132 approaches the required air amount. In this way, by detecting the gas concentration of one predetermined component of the reformed gas actually obtained, and correcting the predicted value of the gas composition thereby, accurate composition prediction and lean combustion limit concentration prediction Is possible.

  Here, the gas component for detecting the gas concentration can be detected with high accuracy, and has a high dependency on the reforming catalyst temperature, the input / output gas temperature and the like as shown in FIG. 1, for example. It is preferred to select a gas. As an example, hydrogen having a low lean combustion limit equivalent ratio, the highest combustible gas such as methane, carbon monoxide, carbon dioxide, or the like can be given.

  In addition, about 1 gas component which measures a density | concentration, according to reforming conditions etc., you may change the gas component to measure.

[Specific Example 2]
FIG. 4 shows a calculation process in the ECU 100 according to the second specific example. The difference from the first specific example is that the gas component to be measured is not one component but two components (S13), and the predicted value of the gas composition is corrected from the gas concentrations of the two components (S14). Other processes are the same as those in the first specific example.

  About the gas component which measures a density | concentration, what is necessary is just to select two which can be measured accurately. For example, when the main component of the gas composition is hydrogen, carbon monoxide, carbon dioxide, or methane, methane and hydrogen, methane and carbon monoxide, or the like can be selected. In this combination, when the temperature of the reforming catalyst has the greatest influence on the composition of the reformed gas, gases having different dependence on the catalyst temperature are selected one by one, which is high for any catalyst temperature. Detection accuracy, that is, high composition prediction is possible. Of course, there may be two kinds of gases (for example, methane and water in FIG. 1) exhibiting the same tendency, and one of the two kinds of gases (for example, in FIG. 1, the temperature dependence is low and the other is high in temperature dependence). Methane and carbon dioxide) can also be selected. In any case, the gas concentration can be measured with high accuracy, and the prediction accuracy can be further improved by selecting any two different types. The gas concentration sensor 150 employs an arbitrary sensor depending on the number of gases to be detected and the type of gas.

As described above, the gas concentration sensor 150 detects the gas concentrations M ₁ ′ and M ₂ ′ (vol%) for two predetermined components of the reformed gas (S13), and the ECU 100 Using the detected concentrations M ₁ ′, M ₂ ′, correction values M ₁ ″, M ₂ ″, M ₃ ″, M ₄ ″... For each gas component concentration are obtained based on the following formula (S14).

M ₁ ”= M ₁ '
M ₂ ”= M ₂ '
M ₃ ″ = (1−M ₁ ′ −M ₂ ′) M ₃ / (M ₃ + M ₄ )
M ₄ ″ = (1−M ₁ ′ −M ₂ ′) M ₄ / (M ₃ + M ₄ )
Using the correction values M ₁ ″, M ₂ ″, M ₃ ″ and M ₄ ″ obtained as described above, the air-fuel mixture in the cylinder 110 is calculated in the same manner as in the first specific example by calculating Expression (1). The lean combustion limit concentration L (vol%) is obtained (S5). The ECU 100 determines the amount of gas fuel to be supplied to the cylinder 110 and the air flow rate according to the lean combustion limit concentration L and the required torque requested by the driver at this time, and further determines the fuel according to the amount. During the fuel injection period at the injection valve 130, the opening degree of the throttle valve 22 is controlled (S6).

  In addition, about the 2 gas component which measures a density | concentration, you may change the gas component to measure according to reforming conditions etc.

[Specific Example 3]
In specific examples 1 and 2, the predicted value is corrected by detecting the concentration of a specific gas component from the reformed gas obtained by the reforming catalyst 230. However, in the internal combustion engine according to specific example 3, the gas concentration is Without measurement, prediction and correction are performed based on other measurement values.

  Hereinafter, the configuration and processing of the internal combustion engine of the specific example 3 will be described with reference to FIGS. 5 and 6. FIG. 5 is a schematic system example of an internal combustion engine that can be adopted in the third specific example, and is common to the system of FIG. 2 except that the gas concentration sensor 150 shown in FIG. 2 is omitted.

  Based on the hydrocarbon fuel flow rate and water flow rate obtained from the sensors 140 and 142 and the catalyst wall temperature obtained from the sensor 146, the ECU 100 creates a correspondence map created in advance based on the correspondence between these flow rates and the catalyst wall temperature. In consideration, the predicted value 1 is obtained (FIG. 6A).

  Further, the ECU 100 corrects the predicted value 1 based on the input gas temperature and the output gas temperature obtained from the temperature sensors 144 and 148.

  More specifically, first, based on the correspondence between the flow rate and the input / output gas temperature based on the hydrocarbon fuel flow rate and water flow rate, and the input gas temperature and output gas temperature obtained from the temperature sensors 144 and 148. Then, the predicted value 2 is obtained separately by referring to the correspondence map created in this way (see FIG. 6B). Next, the predicted value 1 is corrected by the predicted value 2, and a predicted value of the reformed gas composition is obtained (FIG. 6C). It is also synonymous to correct the predicted value 2 by the predicted value 1. For the obtained correction value, the lean combustion limit concentration L of the air-fuel mixture is calculated by calculating the equation (1) in the same manner as in the specific examples 1 and 2, and the lean combustion limit concentration L and the required torque are calculated. Accordingly, the amount of gas fuel to be supplied to the cylinder 110 and the air flow rate are controlled.

  Here, when correcting the predicted value for the gas composition, the predicted value 1 and the predicted value 2 are, for example, the catalyst wall temperature and the input / output gas temperature to the catalyst, which are the reforming conditions (gas composition). Weighted according to the degree of influence. When the gasoline fuel is reformed with steam as in the specific example 3, at least the influence of the catalyst wall temperature on the reforming condition is larger than the input / output gas temperature. Therefore, a higher weight is given to the predicted value 1 (for example, 0.8), a predicted value 2 is set to a weight according to the degree of influence (for example, 0.2), and the two predicted values can be added. it can. Of course, this weighting is set to an optimum value depending on the type of hydrocarbon liquid fuel, reforming reaction, reforming catalyst, and the like. Further, the weighting is not always constant and may be changed according to the reforming conditions. For example, under conditions where the catalyst wall temperature is very high and hardly affected by the input gas temperature, the weight of the predicted value 1 is set higher than usual, and conversely, the catalyst wall temperature is low and the influence of the input gas temperature. If it is a grade which should be considered, it can be set as normal weighting. The predicted value 2 can be obtained from the correspondence between the flow rate and the input gas temperature, the predicted value 3 can be obtained from the correspondence between the flow rate and the output gas temperature, and the predicted value 1 can be corrected by the predicted value 2 and the predicted value 3. It is.

[Modification 1]
7 and 8 show more specific system examples that can be employed in the internal combustion engines of the first to third specific examples. When applied to the third specific example, the gas concentration sensor 150 shown in FIGS. 7 and 8 is not necessary.

  In any system, the hydrocarbon-based liquid fuel is pumped from the fuel tank 40 and the water is pumped from the water tank 50, and is sent to the evaporator 220 via each flow control valve. The evaporator 220 is heated by a heater in FIG. 7 and by an exhaust heat heat exchanger in FIG. 8, and evaporates liquid fuel and water, respectively.

  Similarly, the reforming catalyst 230 is heated by a heater in FIG. 7 and by a heat exchanger for exhaust heat in FIG. The reforming reaction that generates reformed gas mainly composed of hydrogen, carbon monoxide, carbon dioxide, methane, etc. from hydrocarbon liquid fuel such as gasoline and water is an endothermic reaction. The quality catalyst 230 is heated by a heater, a heat exchanger, or the like, thereby proceeding with a reforming reaction using the catalyst.

7 and 8, an O ₂ sensor 134 for measuring the oxygen concentration contained in the exhaust gas is provided on the exhaust side of the cylinder 110 (further downstream of the exhaust catalyst 28). Based on the oxygen concentration obtained by the O ₂ sensor 134, the ECU 100 controls the fuel injection valve 130 so that the air-fuel mixture concentration in the cylinder matches the lean combustion limit concentration L obtained from the above equation (1). Thus, the gas fuel supply amount (fuel injection period) is controlled, and the opening of the throttle valve 22 is controlled to control the air flow rate.

[Modification 2]
It is also possible to switch the correction method as in specific example 1, specific example 2, and specific example 3 in accordance with the change in the reforming conditions.

  For example, among the components of the reformed gas, the concentration of the gas of interest (the gas whose concentration is to be measured) decreases such that it cannot be detected as the catalyst temperature increases or decreases, or the catalyst characteristics change over time. In such a case, or when the fuel flow rate or the water flow rate is a predetermined condition, the number of measurement targets and measurement targets of the gas component may be changed. That is, according to the change of the reforming conditions, it is possible to switch the method of the specific example 1 and the specific example 2 or further to the specific example 3.

  Also, for example, when the detection accuracy of the gas concentration sensor itself changes, or when the gas concentration changes significantly as a result of changes in the characteristics of the reforming catalyst, the detection accuracy changes. It is also possible to employ a prediction and correction method that does not use the measured value of the gas concentration as in Example 3 and to perform switching such that the gas concentration is used for correction under high-accuracy conditions.

It is a figure which shows the relationship between the reforming catalyst temperature and the composition of the reformed gas obtained. 1 is a schematic system diagram of an internal combustion engine according to a specific example 1 of the present embodiment. It is a figure explaining the prediction and the correction | amendment processing method of the gas composition which concerns on the specific example 1 of this embodiment. It is a figure explaining the prediction and correction | amendment processing method of the gas composition which concerns on the specific example 2 of this embodiment. It is a schematic system diagram of an internal combustion engine according to Specific Example 3 of the present embodiment. It is a figure explaining the prediction and correction | amendment method of the gas composition which concerns on the specific example 3 of this embodiment. It is a figure which shows the example of the specific structure applicable to the internal combustion engine which concerns on this embodiment. It is a figure which shows the other example of the specific structure applicable to the internal combustion engine which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine, 20 Intake pipe, 22 Throttle valve, 24 Intake valve, 26 Exhaust valve, 28 Exhaust catalyst, 30 Exhaust pipe, 40 (hydrocarbon type) liquid fuel tank, 50 Water tank, 60 Spark plug, 100 ECU (engine) Controller), 110 cylinder, 130 gas fuel injection valve, 132 air flow sensor, 134 O ₂ sensor, 140 liquid fuel flow sensor, 142 water flow sensor, 144 input gas temperature sensor, 146 catalyst temperature sensor, 148 output gas temperature sensor , 150 gas concentration sensor, 220 evaporator, 230 reforming catalyst, 240 aggregator, 250 reformed gas tank, 260 pump.

Claims (9)

An internal combustion engine using gas fuel as the main fuel,
A reforming catalyst for reacting liquid fuel with water to reform the gas fuel containing a plurality of gas components;
An evaporator for converting the liquid fuel and the water into steam before supplying the liquid fuel to the reforming catalyst;
A flow rate sensor for detecting a flow rate of liquid fuel and a flow rate of water supplied to the evaporator;
A gas temperature sensor for detecting a gas temperature in the reforming catalyst;
A catalyst temperature sensor for detecting the temperature of the reforming catalyst;
A detector for detecting a concentration of at least one gas component among the plurality of gas components of the reformed gas fuel;
With
The engine controller
Utilizing the detection values at the flow rate sensor and the catalyst temperature sensor, referring to a correspondence map between the detection values stored in advance and the gas composition, predicting the gas composition of the gas fuel obtained by reforming,
Further, the internal combustion engine, wherein the predicted value of the gas composition is corrected based on the detected concentration of the gas component. The internal combustion engine according to claim 1,
Furthermore, a gas temperature sensor for detecting the gas temperature of the input gas or output gas of the reforming catalyst is provided,
The internal combustion engine, wherein the engine control unit further uses the detected gas temperature when predicting the gas composition. The internal combustion engine according to claim 1 or 2,
In the correction of the predicted value of the gas composition, the concentration of the detected gas component is set as the concentration of the corresponding gas component in the predicted value, and the remaining of the predicted value is based on the value obtained by removing the detected concentration of the gas component from the overall concentration. An internal combustion engine that calculates a gas component concentration of the engine. An internal combustion engine using gas fuel as the main fuel,
A reforming catalyst for reacting liquid fuel with water to reform the gas fuel containing a plurality of gas components;
An evaporator for converting the liquid fuel and the water into steam before supplying the liquid fuel to the reforming catalyst;
A flow rate sensor for detecting a flow rate of liquid fuel and a flow rate of water supplied to the evaporator;
A gas temperature sensor for detecting a gas temperature of an input gas or an output gas of the reforming catalyst;
A catalyst temperature sensor for detecting the temperature of the reforming catalyst;
With
The engine control unit
Based on the detection values at the flow rate sensor and the catalyst temperature sensor, refer to a correspondence map between the detection values stored in advance and the gas composition, and obtain a predicted value of the gas composition of the gas fuel obtained by reforming, Further, the internal combustion engine, wherein the predicted value is corrected based on the detection result of the gas temperature sensor. The internal combustion engine according to claim 4,
The correction of the predicted value is
A first predicted value obtained based on the detection values of the flow rate sensor and the catalyst temperature sensor;
The internal combustion is performed by using a second predicted value obtained by referring to a correspondence map between a detected value stored in advance and a gas composition based on the flow rate sensor and the detected gas temperature. organ. The internal combustion engine according to any one of claims 1 to 5,
The liquid fuel is a hydrocarbon liquid fuel,
The internal combustion engine, wherein the gas fuel obtained by the reforming contains hydrogen, carbon monoxide, carbon dioxide and methane. The internal combustion engine according to any one of claims 1 to 6,
The engine control unit calculates a lean combustion limit concentration of a mixture of the gas fuel and air in the cylinder based on the corrected predicted value, and according to the lean combustion limit concentration and the required torque, An internal combustion engine characterized by controlling an amount of gas fuel supplied into a cylinder and an air flow rate. The internal combustion engine according to claim 7,
Furthermore, an oxygen sensor is provided on the exhaust side of the cylinder,
Based on the oxygen detection value from the oxygen sensor, the gas fuel supply amount and the air flow rate in the cylinder are controlled so that the mixture concentration in the cylinder matches the obtained lean combustion limit concentration. An internal combustion engine. An internal combustion engine using gas fuel as the main fuel,
A reforming catalyst for reforming liquid fuel into a gas fuel containing a plurality of gas components by reaction;
An evaporator for converting the liquid fuel into vapor before supplying the liquid fuel to the reforming catalyst;
A flow sensor for detecting a flow rate of liquid fuel supplied to the evaporator;
A catalyst temperature sensor for detecting the temperature of the reforming catalyst;
With
The engine control unit uses at least the detection values of the flow rate sensor and the catalyst temperature sensor to refer to the correspondence map between the detection value stored in advance and the gas composition, and the gas fuel gas obtained by reforming Predict composition,
Based on each lean combustion limit concentration of the combustible gas composition of the predicted gas composition, the lean burn limit concentration of the air-fuel mixture in the cylinder is calculated, and according to the lean burn limit concentration and the required torque, An internal combustion engine characterized by controlling an amount of gas fuel supplied into a cylinder and an air flow rate.

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