A method for calculating the overall volume elastic modulus of an ultrahigh pressure common rail system

Abstract

This invention provides a method for calculating the bulk modulus of elasticity of an ultra-high pressure common rail system. The method includes: constructing an ultra-high pressure common rail system test system; selecting measuring points X and Y; recording the pressure signal curves of measuring points X and Y during injection under fixed camshaft speed, injector pulse width, and high-pressure fuel line length; calculating the ultra-high pressure wave propagation velocity u = L / t under each operating condition; calculating the pressure wave propagation velocity at different fuel pressures and temperatures; calculating the fuel density corresponding to the pressure wave propagation velocity under the corresponding pressure and temperature conditions; obtaining the formula for calculating the bulk modulus of elasticity of the ultra-high pressure common rail system under different fuel pressure and temperature conditions; and verifying the calculation results. The method for calculating the bulk modulus of elasticity of an ultra-high pressure common rail system described in this invention can accurately calculate the bulk modulus of elasticity of the system under different fuel pressure and temperature conditions.

Description

Technical Field

[0001] This invention belongs to the field of calculation and analysis technology of diesel engine ultra-high pressure common rail system, and in particular relates to a method for calculating the overall volume elastic modulus of ultra-high pressure common rail system. Background Technology

[0002] High-performance diesel engines require further increases in power density to meet the power demands of vehicles. This increase in power density requires the fuel injection system to inject more fuel into the cylinder without increasing the injection time. This necessitates further increases in the operating pressure of the fuel injection system. As a result, fuel injection systems are beginning to develop towards ultra-high pressure common rail systems with operating pressures exceeding 200 MPa.

[0003] The development and research of ultra-high pressure common rail systems cannot be separated from simulation analysis and calculation. The physical properties or characteristics of fuel are the foundation of this simulation analysis. As the system's operating pressure increases, the physical properties of the fuel within the ultra-high pressure common rail system change significantly. These changes inevitably affect the injection characteristics of the system. Therefore, before conducting simulation analysis of the ultra-high pressure common rail system, it is essential to clarify the physical properties of the fuel. The bulk modulus of elasticity is an important indicator of fuel compressibility and a crucial parameter in fuel system simulation calculations, especially in calculations involving pressure fluctuation propagation. Therefore, the bulk modulus of elasticity directly impacts the accuracy of fuel system simulation calculations.

[0004] Currently, calculations of the bulk elastic modulus of fuel oil are concentrated below 180 MPa, while calculations of the bulk elastic modulus above 200 MPa are lacking. The lack of data on the total bulk elastic modulus of the UHVDC system directly affects the accuracy of simulation calculations and evaluations of the UHVDC system. Summary of the Invention

[0005] In view of this, the present invention aims to propose a method for calculating the overall volumetric elastic modulus of an ultra-high pressure common rail system, so as to solve the problem of inaccurate calculation of the volumetric elastic modulus above 200MPa.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] A method for calculating the overall bulk elastic modulus of an ultra-high pressure common rail system includes the following steps:

[0008] S1. Build an ultra-high pressure common rail system test system, and select the measuring point X near the end of the high pressure oil pipe and the measuring point Y near the end of the high pressure oil pipe as the locations for installing transient pressure and temperature sensors.

[0009] S2. Under the conditions of fixed camshaft speed n, electromagnetic injector injection pulse width Φ and high-pressure oil pipe length L, set multiple working pressure values ​​and the corresponding low-pressure oil circuit temperature value under each working pressure, and record the pressure signal curves of measuring point X and measuring point Y during the injection process under each working condition.

[0010] S3. Select the pressure drop point A at the electromagnetic injector end and the pressure drop point B at the common rail end in the pressure signal curve as the characteristic points for calculating the pressure wave propagation speed. The time difference between points A and B is the pressure wave propagation time t. The ultra-high pressure wave propagation speed u = L / t under each working condition.

[0011] S4. Record the fuel temperature at points A and B under each working condition, take the average of the two as the fuel temperature T in the high-pressure fuel line, take the working pressure as the fuel pressure P in the high-pressure fuel line, and calculate the pressure wave propagation speed under different fuel pressures and temperatures according to step S3.

[0012] S5. The empirical formula for fuel density under different pressures and temperatures is shown in Equation (1). The fuel density under pressure and temperature conditions corresponding to the pressure wave propagation speed is calculated based on Equation (1).

[0013]

[0014] S6. The bulk modulus of the system is K = u 2 ρ, substituting the pressure wave propagation velocity and fuel density values ​​obtained in steps S4 and S5 under the same operating condition into the formula for calculating the bulk elastic modulus, yields a complete set of data for the total bulk elastic modulus under different fuel pressures and temperatures. This complete set of data is then fitted into a formula containing 1 / K. 2 The quadratic function is given by equation (2):

[0015]

[0016] It contains a total of 9 undetermined coefficients. After solving for these undetermined coefficients, we substitute them into equation (2) to obtain the formula (3) for calculating the total bulk elastic modulus of the ultra-high pressure common rail system under different fuel pressure and temperature conditions:

[0017]

[0018] S7. Verify the calculation results of formula (3) using experimental test data.

[0019] Furthermore, the ultra-high pressure common rail system testing system includes an oil tank and an ECU. The outlet of the oil tank is connected to the inlet of the oil tank after passing through a valve, a coarse filter, a fine filter, a high-pressure oil pump, a rail pressure regulating valve, a common rail pipe, and an overflow valve. A temperature controller is also installed on the oil tank. The high-pressure oil pump is also connected to a motor. A pressure gauge is installed on the pipeline between the fine filter and the high-pressure oil pump. A pressure gauge is installed at one end of the common rail pipe, and the other end is connected to the electromagnetic injector through a high-pressure oil pipe. The measuring points X and Y of the high-pressure oil pipe near the common rail pipe and the high-pressure oil pipe near the electromagnetic injector are selected as the locations for installing transient pressure and temperature sensors. The electronically controlled injector is located above the injection pattern tester. The ECU is connected to the pressure gauge, the rail pressure regulating valve, the pressure gauge, the common rail pipe, the electromagnetic injector, and the temperature controller to achieve overall control of the entire system.

[0020] Furthermore, in step S1, measuring point X and measuring point Y are both located on the same high-pressure oil pipe. Under the premise of ensuring the installation space of the transient pressure and temperature sensor, measuring point X is the position closest to the high-pressure oil outlet joint of the common rail pipe, and measuring point Y is the position closest to the high-pressure oil inlet joint of the injector.

[0021] Furthermore, in step S1, the transient pressure and temperature sensor must be able to simultaneously measure the transient pressure and transient temperature of the fuel. The pressure measurement range is 0–300 MPa with a measurement accuracy of less than ±0.16% FSO, and the temperature measurement range is 25–180°C with a measurement accuracy of less than ±1.6°C.

[0022] Furthermore, the working pressure range in step S2 must be greater than or equal to 200 MPa.

[0023] Furthermore, in step S3, the pressure signal curve only needs to be selected from the pressure curve of one injection working cycle. In one working cycle, when the injector starts injecting fuel, a pressure drop will first be generated at the injector end. The expansion wave generated by this pressure drop will propagate to the common rail end, causing a corresponding pressure drop at the common rail end as well. Therefore, the time difference between the two pressure drop points A and B is the pressure wave propagation time t. Since the horizontal axis of the pressure signal curve is the cam angle, it is necessary to perform angle-time conversion based on the camshaft speed n of the test bench in order to obtain the pressure wave propagation time t between points A and B.

[0024] Furthermore, in step S6, since the pipeline deforms during the propagation of the pressure wave, the bulk elastic modulus here is the bulk elastic modulus of the entire high-pressure system.

[0025] Compared with existing technologies, the method for calculating the overall volumetric elastic modulus of an ultra-high pressure common rail system described in this invention has the following advantages:

[0026] (1) The method for calculating the total volume elastic modulus of the ultra-high pressure common rail system described in this invention can summarize and fit the formula for calculating the total volume elastic modulus of the ultra-high pressure common rail system under different fuel pressure and temperature conditions based on limited experimental test data points, accurately calculate the total volume elastic modulus of the ultra-high pressure common rail system under different fuel pressure and temperature conditions, and extend the calculable range of the total volume elastic modulus to ultra-high pressure common rail systems with pressure greater than 200MPa.

[0027] (2) The method for calculating the overall volumetric elastic modulus of the ultra-high pressure common rail system described in this invention further improves the fuel volumetric elastic modulus database, providing important support for improving the accuracy of performance simulation calculations of the ultra-high pressure common rail system; at the same time, compared with experimental testing, this calculation method can greatly save the time and money costs of experimental testing. Attached Figure Description

[0028] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0029] Figure 1 This is a schematic diagram of the ultra-high pressure common rail system test system according to an embodiment of the present invention;

[0030] Figure 2 The pressure signal curves at the injector end and common rail end of the ultra-high pressure common rail system described in this embodiment of the invention;

[0031] Figure 3 The total bulk modulus of elasticity described in the embodiments of the present invention is based on actual experimental test data.

[0032] Figure 4 This is a comparison chart of actual experimental test data and calculated data of the total bulk modulus of elasticity according to the embodiments of the present invention.

[0033] Explanation of reference numerals in the attached figures:

[0034] 1-Fuel tank; 2-Valve; 3-Coarse filter; 4-Motor; 5-High-pressure oil pump; 6-Rail pressure regulating valve; 7-Pressure gauge 1; 8-Fine filter; 9-Pressure gauge 2; 10-Common rail; 11-Relief valve; 12-Electromagnetic injector; 13-Injection pattern tester; 14-Temperature controller; 15-High-pressure oil pipe; S-Pressure signal curve at the common rail end; T-Pressure signal curve at the injector pipe end. Detailed Implementation

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0036] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0037] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0038] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0039] A method for calculating the overall bulk elastic modulus of an ultra-high pressure common rail system, such as... Figures 1 to 4 As shown, it includes the following steps:

[0040] S1. Build an ultra-high pressure common rail system test system, and select the measuring point X near the end of the high pressure oil pipe and the measuring point Y near the end of the high pressure oil pipe as the locations for installing transient pressure and temperature sensors.

[0041] The ultra-high pressure common rail system test system includes an oil tank 1, valve 2, coarse filter 3, motor 4, high-pressure oil pump 5, rail pressure regulating valve 6, pressure gauge 1 7, fine filter 8, pressure gauge 2 9, common rail pipe 10, overflow valve 11, electromagnetic injector 12, injection pattern tester 13, temperature controller 14, high-pressure oil pipe 15, and ECU. The outlet of oil tank 1 passes sequentially through valve 2, coarse filter 3, fine filter 8, high-pressure oil pump 5, rail pressure regulating valve 6, common rail pipe 10, and overflow valve 11 before connecting to the inlet of oil tank 1. A temperature controller 14 is also installed on oil tank 1. The high-pressure oil pump 5 is also connected to motor 4, fine filter 8, and high-pressure oil pipe 15. Pressure gauge 7 is installed on the pipeline between pumps 5. Pressure gauge 9 is installed on one end of common rail 10, and the other end is connected to electromagnetic injector 12 through high-pressure oil pipe 15. The measuring points X and Y of high-pressure oil pipe 15 near common rail 10 and electromagnetic injector 12 are selected as the locations for installing transient pressure and temperature sensors. Electro-injector 12 is located above injection pattern tester 13. ECU signals are connected to pressure gauge 7, rail pressure regulating valve 6, pressure gauge 9, common rail 10, electromagnetic injector 12 and temperature controller 14 to achieve overall control of the entire system.

[0042] In step S1, measuring point X and measuring point Y are both located on the same high-pressure oil pipe. Under the premise of ensuring the installation space of the transient pressure and temperature sensor, measuring point X is the position closest to the high-pressure oil outlet joint of the common rail pipe, and measuring point Y is the position closest to the high-pressure oil inlet joint of the injector.

[0043] In step S1, the transient pressure and temperature sensor must be able to simultaneously measure the transient pressure and transient temperature of the fuel. The pressure measurement range is 0–300 MPa with a measurement accuracy of less than ±0.16% FSO, and the temperature measurement range is 25–180°C with a measurement accuracy of less than ±1.6°C.

[0044] S2. Under fixed camshaft speed n, electromagnetic injector pulse width Φ, and high-pressure oil pipe length L, the working pressures are set to 180MPa, 200MPa, 220MPa, 240MPa, and 250MPa, and the low-pressure oil circuit temperatures are set to 15℃, 20℃, 25℃, 30℃, 35℃, and 40℃, respectively. The pressure signal curves of measuring point X and measuring point Y during the injection process under each working condition are recorded.

[0045] In step S2, the length L of the high-pressure oil pipe should be as long as possible. A high-pressure oil pipe that is too short is not conducive to measuring the difference in pressure fluctuations between measuring point X and measuring point Y.

[0046] In step S2, the range of working pressures should be greater than or equal to 200 MPa, and the smaller the interval between each working pressure, the more test data there will be for different pressure tests, which will be more beneficial to improving the accuracy of the calculation formula.

[0047] S3. Select the pressure drop point A at the electromagnetic injector 12 end and the pressure drop point B at the common rail end in the pressure signal curve as the characteristic points for calculating the pressure wave propagation speed. The time difference between points A and B is the pressure wave propagation time t. The ultra-high pressure wave propagation speed u = L / t under each working condition.

[0048] Specifically, in step S3, the pressure signal curve only needs to be selected from the pressure curve of one injection working cycle. In one working cycle, when the injector starts injecting fuel, a pressure drop will first be generated at the injector end. The expansion wave generated by this pressure drop will propagate to the common rail end, causing a corresponding pressure drop at the common rail end as well. Therefore, the time difference between the two pressure drop points A and B is the pressure wave propagation time t. Since the horizontal axis of the pressure signal curve is the cam angle, it is necessary to perform angle-time conversion based on the camshaft speed n of the test bench in order to obtain the pressure wave propagation time t between points A and B.

[0049] S4. Record the fuel temperature at points A and B under each operating condition, take the average of the two as the fuel temperature T in the high-pressure fuel line, take the working pressure as the fuel pressure P in the high-pressure fuel line, and calculate the pressure wave propagation speed under different fuel pressures and temperatures according to step S3.

[0050] S5. The empirical formula for fuel density under different pressures and temperatures is shown in Equation (1). The fuel density under pressure and temperature conditions corresponding to the pressure wave propagation speed can be calculated based on Equation (1).

[0051]

[0052] S6. The bulk modulus of the system is K = u 2 ρ, substituting the pressure wave propagation velocity and fuel density values ​​obtained in steps S4 and S5 under the same operating condition into the formula for calculating the bulk elastic modulus, yields a complete set of data for the total bulk elastic modulus under different fuel pressures and temperatures. This complete set of data is then fitted into a formula containing 1 / K. 2 The quadratic function is given by equation (2):

[0053]

[0054] It contains a total of 9 undetermined coefficients. These undetermined coefficients (see Table 1) are solved using the Origin platform and then substituted into equation (2).

[0055] Table 1. Undetermined coefficients for calculating pressure wave propagation velocity.

[0056] coefficient value coefficient value coefficient value A <![CDATA[2.209×10 41 ]]> <![CDATA[B3]]> <![CDATA[-2.014×10 35 ]]> <![CDATA[C3]]> <![CDATA[-2.378×10 34 ]]> <![CDATA[B1]]> <![CDATA[-5.105×10 38 ]]> <![CDATA[C1]]> <![CDATA[-2.883×10 39 ]]> E <![CDATA[-4.769×10 44 ]]> <![CDATA[B2]]> <![CDATA[1.971×10 37 ]]> <![CDATA[C2]]> <![CDATA[1.466×10 37 ]]> F <![CDATA[5.028×10 44 ]]>

[0057] The formula for calculating the bulk elastic modulus of the ultra-high pressure common rail system under different fuel pressure and temperature conditions is obtained (3):

[0058]

[0059] In step S6, since the pipeline deforms during the propagation of the pressure wave, the bulk elastic modulus here is the bulk elastic modulus of the entire high-pressure system, which includes both the bulk elastic modulus of the fuel and the bulk elastic modulus of the high-pressure oil pipe.

[0060] S7. Verify the calculation results of formula (3) using experimental test data. If the difference between the two is within 10%, it is considered that formula (3) has high accuracy and can be used to calculate the total volumetric elastic modulus of the system under various pressure and temperature conditions.

[0061] The specific implementation method is as follows:

[0062] like Figure 1 As shown, a test system for an ultra-high pressure common rail system was built. The measuring point X, which is close to the common rail end of the high-pressure oil pipe, and the measuring point Y, which is close to the injector end of the high-pressure oil pipe, were selected as the locations for installing transient pressure and temperature sensors. Under the premise of ensuring the installation space of the transient pressure and temperature sensors, measuring point X is the closest position to the high-pressure oil outlet connector of the common rail, and measuring point Y is the closest position to the high-pressure oil inlet connector of the injector.

[0063] The test system was set with a camshaft speed of 900 r / min, an injector pulse width of 1.5 ms, and a high-pressure oil pipe length of 3060 mm. The above test parameters were fixed, and the working pressures were set to 180 MPa, 200 MPa, 220 MPa, 240 MPa, and 250 MPa. The low-pressure oil circuit temperatures under each working pressure were set to 15℃, 20℃, 25℃, 30℃, 35℃, and 40℃, respectively. The pressure signal curves of measuring points X and Y were recorded during the injection process under each working condition.

[0064] like Figure 2 As shown, a pressure signal curve of an injection working cycle is selected. The pressure drop point A at the injector end and the pressure drop point B at the common rail end are determined in the curve as characteristic points for calculating the pressure wave propagation speed. Since the horizontal axis of the pressure signal curve is the cam angle, it is necessary to perform angle-time conversion based on the camshaft speed of the test bench. The time difference between points A and B is the pressure wave propagation time t. The ultra-high pressure wave propagation speed u = L / t under each working condition.

[0065] Record the fuel temperature at points A and B under each working condition, take the average of the two as the fuel temperature T in the high-pressure oil pipe, take the working pressure as the fuel pressure P in the high-pressure oil pipe, and calculate the test data of pressure wave propagation speed under different fuel pressure and temperature according to step S3; calculate the fuel density under the pressure and temperature conditions corresponding to the pressure wave propagation speed according to the empirical formula (1) of fuel density in step e.

[0066] like Figure 3 As shown, the calculated values ​​of pressure wave propagation speed and fuel density under the same operating conditions are substituted into the relationship K = u 2 ρ is used to obtain actual experimental data on the total bulk modulus of elasticity under different fuel pressures and temperatures.

[0067] The entire set of actual experimental test data is fitted into a dataset containing 1 / K. 2 The quadratic function is given by equation (2):

[0068]

[0069] Equation (2) contains nine undetermined coefficients (see Table 1). These undetermined coefficients are solved using the Origin platform. Substituting each coefficient into equation (2) yields the formula (3) for calculating the total bulk modulus of elasticity of the ultra-high pressure common rail system under different fuel pressure and temperature conditions:

[0070]

[0071] like Figure 4 As shown, the calculation data of formula (3) was verified by actual test data of total bulk modulus. The difference between the two was within 5%, indicating that formula (3) has high accuracy and can be used to calculate total bulk modulus under various pressure and temperature conditions.

[0072] The method for calculating the bulk elastic modulus of an ultra-high pressure common rail system described in this solution can summarize and fit a formula for calculating the bulk elastic modulus of an ultra-high pressure common rail system under different fuel pressure and temperature conditions based on limited experimental test data points. This method obtains the bulk elastic modulus of the ultra-high pressure common rail system within a certain operating pressure and temperature range, extending the calculable range of the bulk elastic modulus to ultra-high pressure common rail systems with pressures greater than 200 MPa. This further improves the fuel bulk elastic modulus database and provides important support for improving the accuracy of performance simulation calculations of ultra-high pressure common rail systems. At the same time, compared with experimental testing, this calculation method can greatly save the time and money costs of experimental testing.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for calculating the overall volumetric elastic modulus of an ultra-high pressure common rail system, characterized in that: Includes the following steps: S1. Build an ultra-high pressure common rail system test system, and select the measuring point X near the end of the high pressure oil pipe and the measuring point Y near the end of the high pressure oil pipe as the locations for installing transient pressure and temperature sensors. S2. Under the conditions of fixed camshaft speed n, electromagnetic injector injection pulse width Φ and high-pressure oil pipe length L, set multiple working pressure values ​​and the corresponding low-pressure oil circuit temperature value under each working pressure, and record the pressure signal curves of measuring point X and measuring point Y during the injection process under each working condition. S3. Select the pressure drop point A at the electromagnetic injector end and the pressure drop point B at the common rail end in the pressure signal curve as the characteristic points for calculating the pressure wave propagation speed. The time difference between points A and B is the pressure wave propagation time t. The ultra-high pressure wave propagation speed u = L / t under each working condition. S4. Record the fuel temperature at points A and B under each working condition, take the average of the two as the fuel temperature T in the high-pressure fuel line, take the working pressure as the fuel pressure P in the high-pressure fuel line, and calculate the pressure wave propagation speed under different fuel pressures and temperatures according to step S3. S5. The empirical formula for fuel density under different pressures and temperatures is shown in Equation (1). The fuel density under pressure and temperature conditions corresponding to the pressure wave propagation speed is calculated based on Equation (1). S6. The bulk modulus of the system is K = u 2 ρ, substituting the pressure wave propagation velocity and fuel density values ​​obtained in steps S4 and S5 under the same operating condition into the formula for calculating the bulk elastic modulus, yields a complete set of data for the total bulk elastic modulus under different fuel pressures and temperatures. This complete set of data is then fitted into a formula containing 1 / K. 2 The quadratic function is given by equation (2): It contains a total of 9 undetermined coefficients. After solving for these undetermined coefficients, we substitute them into equation (2) to obtain the formula (3) for calculating the total bulk elastic modulus of the ultra-high pressure common rail system under different fuel pressure and temperature conditions: S7. Verify the calculation results of formula (3) using experimental test data.

2. The method for calculating the overall volumetric elastic modulus of an ultra-high pressure common rail system according to claim 1, characterized in that: The ultra-high pressure common rail system test system includes an oil tank and an ECU. The oil tank outlet passes sequentially through valves, a coarse filter, a fine filter, a high-pressure oil pump, a rail pressure regulating valve, a common rail pipe, and an overflow valve before connecting to the oil tank inlet. A temperature controller is also installed on the oil tank. The high-pressure oil pump is also connected to a motor. A pressure gauge is installed on the pipeline between the fine filter and the high-pressure oil pump. A pressure gauge is installed at one end of the common rail pipe, and the other end is connected to the electromagnetic injector through a high-pressure oil pipe. Measurement points X near the common rail pipe and Y near the electromagnetic injector on the high-pressure oil pipe are selected as the locations for installing transient pressure and temperature sensors. The electronically controlled injector is located above the injection pattern tester. The ECU is connected to the pressure gauge, rail pressure regulating valve, pressure gauge, common rail pipe, electromagnetic injector, and temperature controller to achieve overall control of the entire system.

3. The method for calculating the overall volumetric elastic modulus of an ultra-high pressure common rail system according to claim 2, characterized in that: In step S1, measuring point X and measuring point Y are both located on the same high-pressure oil pipe. Under the premise of ensuring the installation space of the transient pressure and temperature sensor, measuring point X is the position closest to the high-pressure oil outlet joint of the common rail pipe, and measuring point Y is the position closest to the high-pressure oil inlet joint of the injector.

4. The method for calculating the overall volumetric elastic modulus of an ultra-high pressure common rail system according to claim 2, characterized in that: In step S1, the transient pressure and temperature sensor must be able to simultaneously measure the transient pressure and transient temperature of the fuel. The pressure measurement range is 0–300 MPa with a measurement accuracy of less than ±0.16% FSO, and the temperature measurement range is 25–180°C with a measurement accuracy of less than ±1.6°C.

5. The method for calculating the overall volumetric elastic modulus of an ultra-high pressure common rail system according to claim 1, characterized in that: The working pressure in step S2 must be greater than or equal to 200 MPa.

6. The method for calculating the overall volumetric elastic modulus of an ultra-high pressure common rail system according to claim 1, characterized in that: In step S3, the pressure signal curve only needs to be selected from the pressure curve of one injection cycle. In one cycle, when the injector starts injecting fuel, a pressure drop will first be generated at the injector end. The expansion wave generated by this pressure drop will propagate to the common rail end, causing a corresponding pressure drop at the common rail end. Therefore, the time difference between the two pressure drop points A and B is the pressure wave propagation time t. Since the horizontal axis of the pressure signal curve is the cam angle, it is necessary to perform angle-time conversion based on the camshaft speed n of the test bench in order to obtain the pressure wave propagation time t between points A and B.

7. The method for calculating the overall volumetric elastic modulus of an ultra-high pressure common rail system according to claim 1, characterized in that: In step S6, since the pipeline deforms during the propagation of the pressure wave, the bulk elastic modulus here is the bulk elastic modulus of the entire high-pressure system.

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