CN-117782837-B - Calculation method for total volume elastic modulus of ultrahigh pressure common rail system

CN117782837BCN 117782837 BCN117782837 BCN 117782837BCN-117782837-B

Abstract

The invention provides a total volume elastic modulus calculation method of an ultrahigh pressure common rail system, which comprises the steps of building an ultrahigh pressure common rail system test system, selecting a measuring point X and a measuring point Y, recording pressure signal curves of the measuring point X and the measuring point Y in the injection process under each working condition under the conditions of fixed camshaft rotation speed, injector injection pulse width and high-pressure oil pipe length, calculating the pressure wave propagation speed u=L/t of an ultrahigh pressure wave under each working condition, calculating the pressure wave propagation speed under different fuel pressures and temperatures, calculating the fuel density under the conditions of pressure and temperature corresponding to the pressure wave propagation speed, obtaining a total volume elastic modulus calculation formula under the different fuel pressures and temperatures of the ultrahigh pressure common rail system, and checking calculation result data of the calculation formula. The total volume elastic modulus calculation method of the ultrahigh pressure common rail system can accurately calculate the total volume elastic modulus of the ultrahigh pressure common rail system under different fuel pressure and temperature working conditions.

Inventors

XU DAN
YANG GUICHUN
XU CHUNLONG
ZHANG ZHIHAO
ZHAO ZHISHUAI
LIU YONGWANG
LI HUALE

Assignees

中国北方发动机研究所

Dates

Publication Date: 20260505
Application Date: 20231227

Claims (7)

1. A total volume elastic modulus calculation method of an ultrahigh pressure common rail system is characterized by comprising the following steps of: s1, building an ultrahigh pressure common rail system test system, and selecting a measuring point X of a high-pressure oil pipe, which is close to the end of a common rail, and a measuring point Y of the high-pressure oil pipe, which is close to the end of an oil sprayer, as positions for installing a transient pressure temperature sensor; S2, respectively setting a plurality of working pressure values and corresponding low-pressure oil way temperature values under each working pressure under the conditions of fixed camshaft rotating speed n, electromagnetic oil injector injection pulse width phi and high-pressure oil pipe length L, and recording pressure signal curves of a measuring point X and a measuring point Y in the injection process under each working condition; S3, selecting an electromagnetic fuel injector end pressure dip point A and a common rail pipe end pressure dip point B from a pressure signal curve as pressure wave propagation speed calculation characteristic points, wherein the time difference between the two points A, B is pressure wave propagation time t, and the ultra-high pressure wave propagation speed u=L/t under each working condition; S4, recording the fuel temperature of A, B points under each working condition, taking the average value of the two temperatures as the fuel temperature T in the high-pressure oil pipe, taking the working pressure as the fuel pressure P in the high-pressure oil pipe, and calculating to obtain the pressure wave propagation speed under different fuel pressures and temperatures according to the step S3; s5, the empirical formulas of the fuel densities at different pressures and temperatures are shown as a formula (1), and the fuel densities under the pressure and temperature conditions corresponding to the pressure wave propagation speed are calculated according to the formula (1); S6, substituting the pressure wave propagation speed and the fuel density value under the same working condition calculated according to the steps S4 and S5 into a volumetric elastic modulus calculation formula to obtain the whole set of data of the total volumetric elastic modulus under different fuel pressures and temperatures, and fitting the whole set of data into a quadratic function containing 1/K 2 as shown in formula (2): The total volume elastic modulus calculation formula (3) under different fuel pressure and temperature working conditions of the ultrahigh pressure common rail system is obtained by solving the undetermined coefficients and then carrying the undetermined coefficients into the undetermined coefficients (2): s7, checking the calculation result data of the calculation formula (3) by using the test data.
2. The method for calculating the total volume elastic modulus of the ultrahigh pressure common rail system is characterized in that the ultrahigh pressure common rail system test system comprises an oil tank and an ECU, an outlet of the oil tank is connected to an inlet of the oil tank after passing through a valve, rough filtering, fine filtering, a high-pressure oil pump, a rail pressure regulating valve, a common rail pipe and an overflow valve in sequence, a temperature controller is further arranged on the oil tank, the high-pressure oil pump is further connected to a motor, a first pressure gauge is arranged on a pipeline between the fine filtering and the high-pressure oil pump, a second pressure gauge is arranged at one end of the common rail pipe, the other end of the common rail pipe is connected to an electromagnetic oil sprayer through a high-pressure oil pipe, a measuring point X of the high-pressure oil pipe, which is close to the common rail pipe, and a measuring point Y of the high-pressure oil pipe, which is close to the electromagnetic oil sprayer are respectively selected as positions for installing transient pressure temperature sensors, the electronic control oil sprayer is arranged above the fuel injection rule tester, and is respectively connected to the first pressure gauge, the rail pressure regulating valve, the second pressure gauge, the common rail pipe, the electromagnetic oil sprayer and the temperature controller are respectively.
3. The method for calculating the total volume elastic modulus of the ultrahigh pressure common rail system according to claim 2, wherein in the step S1, the measuring point X and the measuring point Y are both positioned on the same high-pressure oil pipe, the measuring point X is the position closest to a high-pressure oil outlet joint of the common rail pipe on the premise of ensuring the installation space of a transient pressure temperature sensor, and the measuring point Y is the position closest to a high-pressure oil inlet joint of an oil injector.
4. The method for calculating the total volume elastic modulus of the ultrahigh pressure common rail system according to claim 2, wherein the transient pressure and the transient temperature of the fuel oil can be measured simultaneously by the transient pressure temperature sensor in the step S1, the pressure measurement range is 0-300 MPa, the measurement precision is less than +/-0.16% F.S.O, the temperature measurement range is 25-180 ℃, and the measurement precision is less than +/-1.6 ℃.
5. The method for calculating the total elastic modulus of an ultrahigh pressure common rail system according to claim 1, wherein the range of the working pressure in the step S2 is 200MPa or more.
6. The method of claim 1, wherein the pressure signal curve in the step S3 is only required to select a pressure curve of an injection working cycle, in one working cycle, the injector is started to inject fuel, and first a pressure drop is generated at the injector end, an expansion wave generated by the pressure drop propagates to the common rail pipe end, so that the common rail pipe end also generates a corresponding pressure drop, and therefore, a time difference between two pressure drop points A, B is a pressure wave propagation time t, and an abscissa of the pressure signal curve is a cam angle, so that an angle-time conversion is required according to a camshaft rotation speed n of a test bench, so that the pressure wave propagation time t between A, B two points can be obtained.
7. The method of claim 1, wherein in the step S6, the deformation of the pipe is generated during the propagation of the pressure wave, so that the bulk modulus is the bulk modulus of the entire high-pressure system.

Description

Calculation method for total volume elastic modulus of ultrahigh pressure common rail system Technical Field The invention belongs to the technical field of calculation and analysis of ultrahigh pressure common rail systems of diesel engines, and particularly relates to a total volume elastic modulus calculation method of an ultrahigh pressure common rail system. Background The power density of the high-strength diesel engine is required to be further improved so as to meet the requirement of the vehicle on dynamic performance, the fuel injection system is required to inject more fuel into the cylinder on the premise of not increasing injection time, the working pressure of the fuel injection system is required to be further improved, and therefore the fuel injection system starts to develop towards an ultrahigh-pressure common rail system with the working pressure exceeding 200 MPa. The development and development process of the ultrahigh pressure common rail system is independent of simulation analysis and calculation, the physical property or characteristic of the fuel is the basis of the simulation analysis, and along with the improvement of the working pressure of the system, the change of the physical property of the fuel in the ultrahigh pressure common rail system is very obvious, and the change of the physical property can influence the injection characteristic of the ultrahigh pressure common rail system, so that the physical property of the fuel in the ultrahigh pressure common rail system must be clarified before the simulation analysis of the ultrahigh pressure common rail system is carried out. The bulk modulus of elasticity is an important indicator for the compressibility of fuel, and is an important parameter in the simulation calculation of fuel systems, especially in the calculation involving the propagation of pressure fluctuations, so that the bulk modulus of elasticity of fuel has a direct influence on the accuracy of the simulation calculation of fuel systems. At present, the calculation of the fuel oil volume elastic modulus is concentrated below 180MPa, and the calculation of the volume elastic modulus above 200MPa is lacking, but the lack of the total volume elastic modulus data of the ultrahigh pressure common rail system directly influences the accuracy of simulation calculation and evaluation of the ultrahigh pressure common rail system. Disclosure of Invention In view of the above, the invention aims to provide a total volume elastic modulus calculation method of an ultrahigh pressure common rail system, so as to solve the problem of inaccurate calculation of the volume elastic modulus of more than 200 MPa. In order to achieve the above purpose, the technical scheme of the invention is realized as follows: A total volume elastic modulus calculation method of an ultrahigh pressure common rail system comprises the following steps: s1, building an ultrahigh pressure common rail system test system, and selecting a measuring point X of a high-pressure oil pipe, which is close to the end of a common rail, and a measuring point Y of the high-pressure oil pipe, which is close to the end of an oil sprayer, as positions for installing a transient pressure temperature sensor; S2, respectively setting a plurality of working pressure values and corresponding low-pressure oil way temperature values under each working pressure under the conditions of fixed camshaft rotating speed n, electromagnetic oil injector injection pulse width phi and high-pressure oil pipe length L, and recording pressure signal curves of a measuring point X and a measuring point Y in the injection process under each working condition; S3, selecting an electromagnetic fuel injector end pressure dip point A and a common rail pipe end pressure dip point B from a pressure signal curve as pressure wave propagation speed calculation characteristic points, wherein the time difference between the two points A, B is pressure wave propagation time t, and the ultra-high pressure wave propagation speed u=L/t under each working condition; S4, recording the fuel temperature of A, B points under each working condition, taking the average value of the two temperatures as the fuel temperature T in the high-pressure oil pipe, taking the working pressure as the fuel pressure P in the high-pressure oil pipe, and calculating to obtain the pressure wave propagation speed under different fuel pressures and temperatures according to the step S3; s5, the empirical formulas of the fuel densities at different pressures and temperatures are shown as a formula (1), and the fuel densities under the pressure and temperature conditions corresponding to the pressure wave propagation speed are calculated according to the formula (1); S6, substituting the pressure wave propagation speed and the fuel density value under the same working condition calculated according to the steps S4 and S5 into a volumetric elastic modulus calculation formula to obtain