JP3823158B2 - Method for detecting excess air ratio in cylinder of 4-stroke diesel engine with supercharger - Google Patents

Description

  The present invention relates to a method for detecting an excess ratio of air in a cylinder of a supercharged four-stroke diesel engine.

  Conventionally, the generation of air pollutants such as nitrogen oxides in exhaust gas generated from a diesel engine is often caused by combustion. However, in a 4-cycle diesel engine with a supercharger, directly in the cylinders involved in combustion. The excess air ratio was not clear and it was inconvenient to analyze the combustion. Generally, when analyzing the combustion of a non-supercharged diesel engine, the residual oxygen concentration in the exhaust gas is measured, and the excess air ratio is calculated on the assumption that there is no blow-by intake. And the same method was adopted also in the 4-cycle diesel engine with a supercharger.

  By the way, normally, in a 4-cycle diesel engine with a supercharger, there is an overlap period in which the intake valve and the exhaust valve are open at the same time, and during this period, part of the intake air blows out from the exhaust valve, so the oxygen concentration in the exhaust gas The excess air ratio obtained from the above does not accurately represent the excess air ratio in the cylinder. For this reason, a method of measuring the oxygen concentration of the gas in the cylinder and calculating the excess air ratio can be considered, but since this technique requires advanced technology, this method is a general method. I can not say.

  Therefore, the present invention can generally determine the excess air ratio with higher accuracy than the excess air ratio determined from the oxygen concentration in the exhaust gas, and is generally performed without requiring a particularly advanced technique for measurement. An object of the present invention is to provide a method for detecting an excess air ratio in a cylinder of a 4-stroke diesel engine with a supercharger that can easily detect an excess air ratio using a measurement value obtained by measurement.

  The method for detecting the excess air ratio in a cylinder of a 4-stroke diesel engine with a supercharger according to the present invention is based on the state of the gas flowing through the 4-stroke diesel engine with a supercharger, the mass of residual gas in the cylinder, the mass of blow-in intake air, and the exhaust gas. The mass of the cylinder is unknown, and an equation is constructed from the balance between the output of the turbocharger turbine driven by the exhaust gas and the work of the blower, the volume of the cylinder in the compression process and the composition of the exhaust gas, and substituted into the equation Among the measured values, the temperature of the exhaust gas at the outlet of the turbine is the auxiliary variable, and the highest temperature among the auxiliary variables in which the unknown value is a physically meaningful value in the range of the solution values obtained. From the correct answer, the amount corresponding to air is obtained from the correct solution, and the relationship between the theoretical air ratio and the mass of the supplied fuel is obtained. It is characterized by determining the excess air ratio Luo within the cylinder.

  In addition, the method for detecting an excess air ratio in a cylinder of a four-stroke diesel engine with a supercharger according to the present invention is the above-described method for detecting an excess air ratio in a cylinder of a four-stroke diesel engine with a supercharger. In order to obtain a correct answer by solving the above equation assuming that the engine is in a state where there is no blow-through intake and the mass of the blow-through intake, which is the unknown, is zero, the temperature of the exhaust gas at the outlet of the turbine is the value of the solution of the above equation. It is characterized in that the correct answer is obtained by specifying the highest temperature among the temperatures at which becomes a physically meaningful value.

  According to the method for detecting an excess air ratio in a cylinder of a 4-stroke diesel engine with a supercharger according to the present invention, the following effects can be obtained. In other words, the excess air ratio in the cylinder can be easily clarified with higher accuracy than the excess air ratio obtained from the oxygen concentration in the exhaust gas, and generally no advanced technology is required for measurement. The excess air ratio can be easily calculated using the measurement values obtained by the measurement being performed, and it is a very effective means for formulating measures to reduce air pollutants such as nitrogen oxides. Can be used as

  According to the method for detecting the excess air ratio in a cylinder of a 4-stroke diesel engine with a supercharger according to the present invention, the excess air ratio can be obtained and measured with higher accuracy than the excess air ratio obtained from the oxygen concentration in the exhaust gas. However, with the aim of making it possible to easily calculate the excess air ratio using measured values obtained by commonly performed measurements that do not require exceptionally advanced technology. From the state of the gas flowing through the 4-stroke diesel engine, the mass of the residual gas in the cylinder, the mass of the blow-in intake air, and the mass of the exhaust gas are unknown, and the output of the turbocharger turbine driven by the exhaust gas and the work of the blower The equation of the cylinder volume and the composition of the exhaust gas in the compression process and the temperature of the exhaust gas at the outlet of the turbine among the measured values to be substituted into the equation Is used as the auxiliary variable, and the correct temperature is determined by specifying the highest temperature among the auxiliary variables in which the above unknown value is a physically meaningful value within the range of the calculated solution values. This is achieved by determining the amount of air corresponding to air among the gas components in the cylinder and determining the excess air ratio in the cylinder from the relationship between this and the theoretical air ratio and the mass of fuel supplied. did.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is an overall conceptual diagram for explaining the gas flow of a 4-stroke diesel engine with a supercharger, and FIG. 2 shows the relationship between the mass of blow-through intake air and the temperature of exhaust gas at the turbine outlet of the turbocharger. It is a graph to show.

  First, in FIG. 1, the gas flow in a supercharger in a 4-stroke diesel engine with a supercharger and a 4-stroke diesel engine will be described. The air is sucked and compressed by the blower (or compressor) 2 of the supercharger 1, then cooled by the intercooler 4 as intake air, and further supplied to each of the cylinders 5, 6, and 7 through the intake manifold. All the gas discharged from each of the cylinders 5, 6 and 7 becomes exhaust gas (so-called exhaust gas), is led to the turbine 3 of the supercharger 1, and after energy is recovered, the exhaust pipe 11 enters the atmosphere. And released.

  Next, the flow of in-cylinder gas in the intake stroke will be described. In FIG. 1, as shown in the third cylinder 7, since the intake valve 8 is open in the intake stroke, the intake air is guided into the cylinder 7. However, since there is a period in which the intake valve 8 and the exhaust valve 9 are open at the same time, the intake air is divided into in-cylinder intake air that remains in the cylinder 7 and blow-through intake air that passes from the intake valve 8 to the exhaust valve 9.

  Next, the in-cylinder gas in the compression stroke will be described. As shown in the second cylinder 6 in FIG. 1, when the compression stroke starts, the intake valve 8 closes early and compression starts. The gas in the cylinder 6 at this time is composed of the cylinder intake air and the residual gas.

  Then, the in-cylinder gas in the expansion stroke will be described. As shown in the first cylinder 5 of FIG. 1, fuel is injected at the initial stage of the expansion stroke, and combustion is performed. Along with this, the in-cylinder gas becomes combustion gas.

  Further, the gas flow in the exhaust stroke will be described. In FIG. 1, when the end of the expansion stroke is approached, the exhaust valve 9 is opened, and most of the combustion gas is discharged outside the cylinder, but a part remains in the cylinder and becomes residual gas. The fuel gas discharged to the outside of the cylinder is mixed in the blow-in air intake and the exhaust manifold 10 to become exhaust gas and reach the turbine 3 of the supercharger 1.

Next, the unknown will be described. In order to obtain the excess air ratio in the cylinders 5, 6, and 7, the residual gas mass, the blow-in intake mass, and the exhaust gas mass are represented as unknowns by the following symbols.
G _ret : Residual gas mass G _short : _Blow-in intake mass G _exh : Exhaust gas mass

ここで、
Ｍ_f ： 供給された燃料質量
Ｔ_o ： 大気温度
Ｔ_b ： 過給機１のブロア２の出口における吸気の温度
Ｔ_t ： 過給機１のタービン３の入口における排出ガスの温度
Ｔ_se ： タービン３の出口における排出ガスの温度
Ｋ_s ： 吸気管の入口における空気の温度を用いた空気の比熱比
Ｋ_t ： タービン３の入口における排出ガスの温度を用いた排出ガスの比熱比 The relationship between the output of the turbine 3 of the supercharger 1 and the work of the blower 2 will be described. For the supercharger 1, the output of the turbine 3 can be obtained from the change in the exhaust gas flowing through the turbine 3, and the work can be obtained from the change in the intake air flowing through the blower 2. Since the output of the turbine 3 is the work of the blower 2, the formula [1] is established.

here,
M _f : supplied fuel mass T _o : atmospheric temperature T _b : intake air temperature at the outlet of the blower 2 of the turbocharger T _t : exhaust gas temperature at the inlet of the turbine 3 of the turbocharger T _se : turbine Exhaust gas temperature at outlet 3 K _s : Specific heat ratio of air using air temperature at inlet of intake pipe K _t : Specific heat ratio of exhaust gas using temperature of exhaust gas at inlet of turbine 3

ここで、
Ｐ_b ： 吸気の圧力
Ｔ_s ： 気筒５，６，７の入口における吸気の温度
Ｒ_s ： 空気のガス定数
Ｖ_cl ： 吸気弁８が閉時の気筒５，６，７の体積 Next, an equation for obtaining the mass of gas in the cylinders 5, 6, and 7 will be described. The cylinder volume at the moment when the intake valve is closed in the compression stroke is obtained by calculation. Further, the pressure in the cylinders 5, 6, and 7 is the intake pressure, and the cylinders 5, 6, and 7 have the intake air and the residual gas in the cylinders 5, 6, and 7, so the cylinders 5, 6, and 7 The mass of the gas inside can be expressed by the formula [2].

here,
P _b : Intake pressure T _s : Intake air temperature at the inlets of cylinders 5, 6, 7 R _s : Gas constant of air V _cl : Volume of cylinders 5, 6, 7 when intake valve 8 is closed

ここで、
Ｃ_nＨ_m ： 燃料が単一の分子からなるとしたときの化学記号
ＣＯ₂ ： 二酸化炭素の化学記号
Ｏ₂ ： 酸素分子の化学記号
Ｎ₂ ： 窒素分子の化学記号
Ｆｒ_CO2 ： 残留ガス中の二酸化炭素の質量分率
Ｆｒ_H2O ： 残留ガス中の水分の質量分率
Ｆｒ_N2 ： 残留ガス中の窒素の質量分率
Ｆｒ_a ： 残留ガス中の空気の質量分率
ｍ ： 燃料が単一の分子からなるとしたときの分子に含まれる水素原子の数 ｎ ： 燃料が単一の分子からなるとしたときの分子に含まれる炭素原子の数 ｍ_f ： 燃料の分子量
ｍ_CO2 ： 二酸化炭素の分子量
ｍ_H2O ： 水分の分子量
ｍ_a ： 空気の分子量
ｍ_N2 ： 窒素の分子量
３．７７３は空気中の酸素モル数を１とした時の窒素モル数
４．７７３は空気中の酸素モル数を１とした時の空気モル数 The relational expression at the time of combustion in the cylinder will be described as follows. In the combustion in the expansion stroke, if the fuel is composed of only carbon and hydrogen and complete combustion is performed, the chemical reaction shown in [Formula 3] is performed before and after the combustion.

here,
C _n H _m : Chemical symbol when fuel is composed of a single molecule CO ₂ : Chemical symbol of carbon dioxide O ₂ : Chemical symbol of oxygen molecule N ₂ : Chemical symbol of nitrogen molecule Fr _CO2 : Dioxide in residual gas Mass fraction of carbon Fr _H2O : Mass fraction of moisture in residual gas Fr _N2 : Mass fraction of nitrogen in residual gas Fr _a : Mass fraction of air in residual gas m: Fuel from a single molecule The number of hydrogen atoms contained in the molecule when n is n: The number of carbon atoms contained in the molecule when the fuel is composed of a single molecule m _f : The molecular weight of the fuel m _CO2 : The molecular weight of carbon dioxide m _H2O : Water Molecular weight of m _a : molecular weight of air m _N2 : molecular weight of nitrogen 3.773 is the number of moles of nitrogen when the number of moles of oxygen in air is 1. 4.773 is the air when the number of moles of oxygen in air is 1. Number of moles

Next, a formula representing mass fractions of carbon dioxide, moisture, air, and nitrogen in the residual gas will be described. From the viewpoint that the composition of the combustion gas generated in the expansion stroke is the same as the composition of the residual gas existing in the compression stroke, the mass fraction of carbon dioxide, moisture, air, and nitrogen is The right side of the equation is obtained by dividing the mass of carbon dioxide, moisture, air, and nitrogen by the mass of the combustion gas, and is expressed by the following [Equation 4], [Equation 5], [Equation 6], and [Equation 7]. The

ここで、
γ ： 排出ガス中の酸素濃度

Further, a relational expression between the oxygen concentration of the exhaust gas and the composition will be described. The oxygen concentration of the exhaust gas is measured by the exhaust pipe. Further, since the exhaust gas is composed of the combustion gas in which the combustion gas equivalent to the mass of the residual gas existing at the beginning of the compression stroke is left in the cylinder and the blow-in air, the composition of the exhaust gas is required. Further, since the oxygen concentration of the exhaust gas is the volume ratio of the exhaust gas and oxygen, the following equation (8) is established.

here,
γ: Oxygen concentration in exhaust gas

  A procedure for obtaining a solution from the above simultaneous equations will be described. Substituting [Equation 4], [Equation 5], [Equation 6] and [Equation 7] into [Equation 8], an equation including residual gas mass, blow-by intake mass, and exhaust gas mass which are unknown numbers It becomes. Accordingly, a solution can be obtained from the [Equation 1], [Equation 2], and [Equation 8] equations.

Next, symbols constituting the equation will be described. Of the items represented by the symbols used in the equations, γ, T _o , T _b , T _t , T _se , P _b , P _t , T _s other than the unknowns G _res , G _short , G _exh. , M _f can be a measured value or a value obtained by calculation from the measured value. Further, V _cl can be obtained by calculation from the dimensions of the engine and the closing timing of the intake valve. m, n, and m _f are known numbers obtained from the analysis results of the fuel, k _s , k _t , and R _t are physical properties of air or exhaust gas. m _CO2 , m _H2O , m _a , m _N2 Is the molecular weight of various gases and is a known number. Since all of the above are shown by specific numerical values, they can be regarded as constants.

  Now, setting of auxiliary variables will be described. A solution can be obtained by substituting a specific numerical value for the symbol of the equation. However, since the measured value includes an error, the solution of the unknown does not always take a physically meaningful value, that is, zero or a positive value. Therefore, in solving the equation, since the difference between the temperature of the exhaust gas at the inlet of the turbine 3 of the turbocharger 1 and the temperature of the exhaust gas at the outlet is important, the temperature of the exhaust gas at the inlet of the turbine 3 is regarded as a constant. Assuming that the temperature of the exhaust gas at the outlet of the turbine 3 is an auxiliary variable, the residual gas mass, the blow-in intake mass, and the exhaust gas mass have physically meaningful values for a certain range of auxiliary variables. Therefore, in order to obtain a correct answer, it is necessary to specify the value of the auxiliary variable.

  Next, the identification of the auxiliary variable will be described. In order to specify the value of the auxiliary variable, a 4-stroke diesel engine with a supercharger is operated with no blow-through intake, and the equation is solved by the same method as described above. The result is shown in FIG. In Fig. 2, the vertical axis represents the mass of the blow-through intake, which is an unknown, and the horizontal axis represents the temperature of the exhaust gas at the turbine outlet, which is an auxiliary variable. Is shown. Here, since the correct answer of the mass of the blow-through intake air is zero, the value that the auxiliary variable should take is the highest temperature of the exhaust gas at the outlet of the turbine 3 within the condition that all unknowns are physically meaningful. Can be specified. In addition, even in the case of an operation with blow-in air, a correct answer can be obtained for the previous calculation by applying the above specific method.

ここで、
Ｌ_o ： 理論空気比で燃料の物性値から求めた値
Ｇ_res ： 残留ガスの質量で三連立方程式から得た値
Ｇ_exh ： 排出ガスの質量で三連立方程式から得た値
Ｍ_f ： 供給された燃料の質量
Ｆｒ_a ： 残留ガス中の空気の質量分率で［数７］式を解いて得た値 A procedure for obtaining the excess air ratio in the cylinder will be described based on the above results. The excess air ratio in the cylinder is obtained from the relationship between the amount corresponding to air among the gas components in the compression stroke, the theoretical air ratio, and the mass of the supplied fuel. That is, it can be obtained by substituting each value into the following [Equation 9].

here,
L _o : The value obtained from the physical property value of the fuel with the theoretical air ratio G _res : The value obtained from the three simultaneous equations with the mass of the residual gas G _exh : The value obtained from the three simultaneous equations with the mass of the exhaust gas M _f : Supplied Fuel mass Fr _a : Value obtained by solving the equation (7) with the mass fraction of air in the residual gas

  Experiments in the case where there is a blow-through intake and no blow-through intake using a Mu323 type engine manufactured by Matsui Iron Works, which is a 4-stroke diesel engine with a turbocharger that can change the opening and closing timing of intake and exhaust valves owned by the National Maritime Research Institute The excess air ratio in the cylinder was obtained from the measured value. As a result, it has been clarified that the nitrogen oxide concentration generated in the engine and the nitrogen oxide concentration generated from the calculated excess air ratio are proportional to the excess air ratio. Since the excess air ratio in the cylinder can be easily clarified by the present invention, the present invention can be utilized as a highly effective means in formulating measures for reducing air pollutants such as nitrogen oxides. Is expected to be.

It is a whole conceptual diagram for demonstrating the gas flow of a 4-stroke diesel engine with a supercharger. It is a graph which shows the relationship between the mass of blow-in intake, and the temperature of the exhaust gas in the exit of the turbine of a supercharger.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Supercharger 2 Blower 3 Turbine 4 Intercooler 5 1st cylinder 6 2nd cylinder 7 3rd cylinder 8 Intake valve 9 Exhaust valve 10 Exhaust manifold 11 Exhaust pipe

Claims (2)

From the state of the gas flowing through the 4-stroke diesel engine with a supercharger, the mass of the residual gas in the cylinder, the mass of the blow-in air intake, and the mass of the exhaust gas are unknown, and the output of the turbocharger turbine driven by the exhaust gas The equation was calculated from the balance between the work of the blower and the work of the blower, the volume of the cylinder in the compression process, and the composition of the exhaust gas. In the range of solution values, the correct temperature is determined by specifying the highest temperature among the auxiliary variables in which the unknown value is a physically meaningful value, and from this correct solution, the gas in the cylinder during the compression process is determined. An amount corresponding to air is obtained from the components, and an excess air ratio in the cylinder is obtained from the relationship between the theoretical air ratio and the mass of the supplied fuel. Cylinder air excess ratio detecting method of hazel engine. 2. The method for detecting an excess air ratio in a cylinder of a 4-stroke diesel engine with a supercharger according to claim 1, wherein the 4-stroke diesel engine with a supercharger is in a state where there is no blow-through intake, and the mass of the blow-through intake that is the unknown number. In order to obtain a correct solution by solving the above equation with zero as the temperature, the temperature of the exhaust gas at the outlet of the turbine is the highest among the temperatures at which the solution value of the above equation becomes a physically meaningful value. A method for detecting an excess air ratio in a cylinder of a 4-stroke diesel engine with a supercharger, characterized in that a correct answer is obtained by specifying a temperature.

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