A high-pressure common rail fuel injector control valve and a design method for suppressing cavitation thereof

Abstract

The application provides a high-pressure common rail fuel injector control valve and a design method for inhibiting cavitation, comprising a control valve shell and a valve rod; a control cavity and a mounting cavity are arranged in the control valve shell; the control cavity is connected with a rail pipe through an oil inlet hole; the mounting cavity is coaxially provided with a first hole plate and a second hole plate in close contact with each other from top to bottom; the periphery of the first hole plate and the second hole plate is in close contact with the inner wall of the mounting cavity; the first hole plate is provided with a discharge hole; the second hole plate is internally provided with a ball valve cavity, a flow guide hole, an oil outlet hole and an intermediate chamber in close contact with each other from top to bottom; the intermediate chamber is connected with the control cavity; the discharge hole is connected with the ball valve cavity; the bottom end of the valve rod is fixedly provided with a sealing steel ball; the valve rod passes through the first hole plate and enters the ball valve cavity, and the sealing steel ball is located above the flow guide hole and cooperates with the conical wall surface of the ball valve cavity. The application reduces the cavitation intensity at the sealing surface of the ball valve and improves the service life of the fuel injector control valve.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of high-pressure common rail fuel injectors, and particularly relates to a high-pressure common rail fuel injector control valve and a design method for suppressing cavitation thereof. BACKGROUND

[0002] With the development of high-pressure common rail fuel injection systems, the fuel injection pressure of fuel injectors is continuously increased, and the cavitation intensity in the control valve of the fuel injector is also increased, especially the cavitation at the sealing surface of the control valve seriously affects the service life of the control valve.

[0003] At present, a ball valve type fuel injector control valve is commonly used in the industry, in order to ensure the high response speed of the control valve and realize the accurate control of fuel injection, the sealing ball of the ball valve is designed to be small in size (the diameter is generally 1-2 mm) and the lift of the ball valve is small (about 0.03-0.1 mm), after the ball valve is opened, a large pressure drop of fuel occurs at the sealing surface of the ball valve, which causes the generation of strong cavitation, resulting in the cavitation erosion of the metal surface of the valve seat sealing surface, and finally leading to the failure of the control valve, affecting the overall working efficiency and service life of the fuel injector, and causing certain safety hazards in the use of the fuel injector. SUMMARY

[0004] The purpose of the present application is to solve the problems in the prior art, and to provide a high-pressure common rail fuel injector control valve and a design method for suppressing cavitation thereof, which changes the cavitation occurrence position of the ball valve cavity, reduces the cavitation intensity at the sealing surface of the ball valve, and improves the service life of the fuel injector control valve.

[0005] The technical scheme adopted by the present application is as follows: a high-pressure common rail fuel injector control valve, comprising a control valve housing and a valve stem; a control cavity and a mounting cavity are coaxially arranged inside the control valve housing from bottom to top; the control cavity is connected with a rail pipe through an oil inlet hole; characterized in that: the mounting cavity is sequentially coaxially arranged with a first hole plate and a second hole plate in close contact with each other from top to bottom; the four peripheral edges of the first hole plate and the second hole plate are in close contact with the inner wall of the mounting cavity; an exhaust hole is arranged on the first hole plate; a ball valve cavity, a flow guide hole, an oil outlet hole and an intermediate chamber are sequentially arranged in the second hole plate from top to bottom and are in communication with each other; the intermediate chamber is connected with the control cavity; the exhaust hole is connected with the ball valve cavity; a sealing steel ball is fixedly arranged at the bottom end of the valve stem; the valve stem passes through the first hole plate into the ball valve cavity, and the sealing steel ball is located above the flow guide hole and cooperates with the conical wall surface of the ball valve cavity; an oval round corner is formed at the junction of the flow guide hole and the ball valve cavity; the oval round corner is tangent to the edge line of the flow guide hole and tangent to the edge line of the conical wall surface of the ball valve cavity, and the major axis of the oval round corner is perpendicular to the axis of the second hole plate.

[0006] The beneficial effects of the present application are: the present application optimizes the internal structure design of the fuel injector control valve, reduces the cavitation intensity in the throttle hole and the flow guide hole after the control valve is opened, makes the cavitation originally occurring at the sealing surface of the conical wall surface of the ball valve cavity transfer to its downstream, reduces the cavitation risk of the sealing surface of the conical wall surface of the ball valve cavity, and further improves the working efficiency, stability and service life of the fuel injector.

[0007] Further, the present application designs the oil hole based on the fuel characteristics and the fuel injector pressure to ensure that it meets the basic requirements of fuel injection.

[0008] Further, the present application designs the intermediate chamber based on the length and diameter of the oil hole, which is beneficial to reduce the flow velocity difference between the fuel near the oil hole wall surface and the fuel near the intermediate chamber wall surface, inhibit the flow separation caused by the sudden drop of the fuel flow area and the change of the flow direction, effectively inhibit the cavitation phenomenon in the oil hole, and further reduce the cavitation intensity in the downstream flow guide hole and the ball valve cavity.

[0009] Further, the present application designs the flow guide hole based on the size of the intermediate chamber, thereby reducing the generation of large-scale vortex in the flow guide hole and reducing the generation of cavitation in the flow guide hole.

[0010] Further, the present application designs the elliptical fillet based on the size of the oil hole, the intermediate chamber and the flow guide hole, so as to ensure that the elliptical angle profile at the corner is beneficial to reduce the flow separation of the fuel at the sealing surface and the upstream part of the sealing surface, and avoid the formation of a local low pressure area; at the same time, it can reduce the conversion rate of fuel pressure energy to kinetic energy near the sealing surface, reduce the fuel velocity gradient near the sealing surface, and inhibit the formation of a low pressure area. The reduction of the low pressure area destroys the cavitation initial condition, reduces the cavitation intensity at the sealing surface, and further achieves the purpose of reducing the cavitation of the sealing surface.

[0011] Further, the present application optimizes the structural matching relationship between the oil hole, the intermediate chamber and the flow guide hole, so that the low pressure area moves downstream, and the cavitation generated in the low pressure area also moves downstream. The cavitation generation position is downstream of the sealing ring belt where the sealing steel ball cooperates with the conical wall surface of the ball valve cavity, thereby reducing the cavitation degree at the sealing ring belt. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 Figure a is a structural schematic diagram of the present application;

[0013] Figure 2 Figure b is a structural schematic diagram of the present application;

[0014] Figure 3 Figure is a design size schematic diagram of the present application;

[0015] Figure 4 Figure is a cavitation effect comparison diagram of the present application and the prior art;

[0016] Wherein, 1-second orifice plate, 2-first orifice plate, 3-valve stem, 4-sealing steel ball, 5-control valve housing, 6-piston, 7-connecting rail pipe, 8-oil inlet, 9-control chamber, 10-intermediate chamber, 11-oil outlet, 12-guide hole, 13-ball valve chamber, 14-discharge hole, 15-installation chamber. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments to facilitate a clear understanding of the present invention, but these descriptions do not constitute a limitation on the present invention.

[0018] Example 1

[0019] like Figures 1-2 As shown, the present invention provides an injector control valve with an elliptical rounded corner throttling orifice plate, including a control valve housing 5 and a valve stem 3; the control valve housing 5 has a control chamber 9 and an installation chamber 15 coaxially arranged from bottom to top inside; the control chamber 9 is connected to the rail pipe through an oil inlet hole 8; the installation chamber 15 has a first orifice plate 2 and a second orifice plate 1 arranged coaxially from top to bottom, which are in close contact with each other; the four edges of the first orifice plate 2 and the second orifice plate 1 are in close contact with the inner wall of the installation chamber 15; the first orifice plate 2 is provided with a discharge hole 14; the second orifice plate 1 has a ball valve chamber 13, a guide hole 12, an oil outlet hole 11 and an intermediate chamber 10 arranged from top to bottom inside, which are interconnected; the intermediate chamber 10 is connected to the control chamber 9; the discharge hole 14 is connected to the ball valve chamber 13; a sealing steel ball 4 is fixedly provided at the bottom end of the valve stem 3; the valve stem 3 passes through the first orifice plate 2 and enters the ball valve chamber 13, and the sealing steel ball 2 cooperates with the conical wall surface of the ball valve chamber 13.

[0020] Specifically, the bottom end of the oil inlet hole 8 of the second orifice plate 1 has a chamfer, the chamfer size of which is 1 / 15 to 1 / 10 of the diameter of the oil outlet hole 11. This structure of the present invention can reduce the degree of cavitation in the oil outlet hole 11, reduce the number of cavitation bubbles flowing into the downstream guide hole 12 and the ball valve cavity 13, and reduce the degree of cavitation in the ball valve cavity 13.

[0021] Specifically, the length l2 of the oil outlet 11 is calculated using the following formula:

[0022]

[0023] In the formula, d2 is the diameter of the oil outlet hole 11, which is selected according to the power requirements of the diesel engine where the injector is located; f is the friction coefficient between the fuel and the flow channel wall; ρ is the fuel density; ΔP is the pressure difference between the inlet and outlet of the injector control valve, which is the initial design parameter of the injector control valve; and n1 is an empirical constant.

[0024] Specifically, the diameter d1 of the intermediate chamber 10 of the second orifice plate 1 is calculated using the following formula:

[0025]

[0026] In the formula, g is the acceleration due to gravity, and n2 is an empirical constant.

[0027] The length l1 of the intermediate chamber 10 of the second orifice plate 1 is calculated using the following formula:

[0028]

[0029] In the formula, P is the fuel injection pressure of the diesel engine where the injector is located, which is determined by the diesel engine.

[0030] The chamfer β between the intermediate chamber 10 and the oil outlet 11 has a value ranging from 120°.

[0031] -140°, the chamfer value is adjusted according to actual needs. The structural design of the intermediate chamber 10 helps to reduce the flow velocity difference between the fuel near the wall of the intermediate chamber 10 and the fuel near the wall of the oil outlet 11, suppresses the flow separation caused by the sudden drop in fuel flow area and the change in flow direction, and can effectively suppress the cavitation phenomenon in the oil outlet 11, thereby reducing the cavitation intensity in the downstream guide hole 12 and the ball valve cavity 13.

[0032] Specifically, the orifice diameter d3 of the guide hole 12 of the second orifice plate 1 is calculated using the following formula:

[0033]

[0034] In the formula P v Where n is the saturated vapor pressure of fuel oil, and n3 is an empirical constant.

[0035] Specifically, the length l3 of the guide hole 12 is calculated using the following formula:

[0036]

[0037] In the formula, P is the injection pressure of the diesel engine where the injector is located, which is determined by the diesel engine. The structural design of the guide hole 12 of the second orifice plate 1 is beneficial to reduce the generation of large-scale eddies in the guide hole 12, reduce the generation of cavitation in the guide hole 12, reduce the flow velocity of fuel in the guide hole 12, appropriately increase the fuel pressure, accelerate the collapse of cavitation bubbles flowing from the oil outlet 11 into the guide hole 12, reduce the number of cavitation bubbles flowing into the ball valve cavity 13, and reduce the degree of cavitation in the ball valve cavity 13.

[0038] Specifically, such as Figure 3 As shown, the top of the guide hole 12 of the second orifice plate 1 has an elliptical fillet at the junction with the ball valve cavity 13. This ellipse is tangent to the edge of the guide hole 12 and to the edge of the conical wall of the ball valve cavity 13. The major axis of the ellipse is perpendicular to the axis of the orifice plate. The major semi-axis a and minor semi-axis b of the ellipse are calculated by the following formulas.

[0039]

[0040] Where α is the taper of the conical wall of the ball valve cavity 13, R is the radius of the sealing steel ball 4, typically 1.3-2.5 mm, and n4, n5, n6, and n7 are empirical constants. The elliptical profile design at this corner helps reduce fuel flow separation at the sealing surface and upstream of the sealing surface, preventing the formation of local low-pressure zones. This design also reduces the rate of conversion of fuel pressure energy to kinetic energy near the sealing surface, decreasing the fuel velocity gradient near the sealing surface and suppressing the formation of low-pressure zones. The reduction of the low-pressure zone disrupts the initial cavitation conditions, reduces the cavitation intensity at the sealing surface, and thus reduces cavitation erosion at the sealing surface.

[0041] Specifically, the ball valve cavity 13 has a conical structure; the diameter of its top end is larger than that of its bottom end; the guide hole 12 is connected to the bottom end of the ball valve cavity 13; and the diameter of the sealing steel ball 4 is larger than the diameter of the bottom end of the ball valve cavity 13. This structure of the present invention can achieve complete collapse of cavitation bubbles in the ball valve cavity 13, while the sealing steel ball 4 can block the inflow of fuel when closed.

[0042] Specifically, four discharge holes 14 are provided, symmetrically distributed around the ball valve cavity 13 above and communicating with it. This invention enables the effective discharge of fuel from the ball valve cavity 13 when the control valve is opened, ensuring the stability and continuity of the injector's operation.

[0043] Example 2

[0044] This invention provides a cavitation suppression design method for a high-pressure common rail injector control valve, comprising the following steps:

[0045] 1) Design of the oil outlet hole 11: The diameter d2 of the oil outlet hole 11 is selected based on the power requirements of the diesel engine where the injector is located; the injector is selected according to the diesel engine power, and then the diameter of the oil outlet hole 11 of the injector control valve can be determined; after determining the diameter d2 of the oil outlet hole 11, the length l2 of the oil hole is calculated according to the following formula:

[0046]

[0047] In the formula, f is the coefficient of friction between the fuel and the flow channel wall, ρ is the fuel density, and ΔP is the pressure difference between the inlet and outlet of the injector control valve, all determined by the selected diesel engine. The diesel grade corresponding to the diesel engine is determined by the fuel density, and the rail pressure is determined when the diesel engine design is finalized. The inlet pressure of the injector control valve is the rail pressure, and the outlet pressure is generally atmospheric pressure; therefore, ΔP is generally equal to the rail pressure value. The coefficient of friction f is the friction between the metal surface of the injector and the fuel; this value can be determined after the diesel engine design is finalized. n1 is an empirical constant.

[0048] 2) Design of intermediate chamber 10: The diameter d1 of intermediate chamber 10 is calculated using the following formula:

[0049]

[0050] In the formula, g is the acceleration due to gravity, and n2 is an empirical constant;

[0051] The length l1 of the intermediate chamber 10 is determined based on its diameter d1; the value of the length l1 of the intermediate chamber 10 ranges from 2.2 to 2.5 times the diameter d1.

[0052] The chamfer β between the intermediate chamber 10 and the oil outlet 11 is determined to be in the range of 120°-140°;

[0053] 3) Design of guide hole 12: The diameter d3 of guide hole 12 is calculated using the following formula, and then the length l3 of guide hole 12 is determined:

[0054]

[0055] In the formula, P v The fuel saturated vapor pressure is determined by the diesel grade corresponding to the diesel engine where the injector is located, and n3 is an empirical constant; the value range of the guide orifice 12 length l3 is 1.1-2.5 times the orifice diameter d3 of the guide orifice 12.

[0056] 4) Design of ball valve cavity 13: Calculate the taper α of the conical wall surface of ball valve cavity 13, and the major semi-axis a and minor semi-axis b of the elliptical fillet using the following formula:

[0057]

[0058] Where R is the radius of the sealing steel ball 4, and its value ranges from 1.3 to 2.5 mm, ensuring that it is larger than the radius of the oil outlet hole 11; the sealing steel ball 4 is generally selected as a standard part, and the corresponding size is selected according to the diesel engine power; n4, n5, n6, and n7 are empirical constants.

[0059] The structure designed in this invention changes the position of the low-pressure zone caused by the flow separation phenomenon resulting from the change in the direction of high-speed fuel flow at the junction of the guide hole 12 and the ball valve cavity 13. This structure of the invention moves the low-pressure zone downstream, and the cavitation generated in the low-pressure zone also moves downstream. The cavitation generation position is downstream of the sealing ring where the sealing steel ball 4 and the conical wall of the ball valve cavity 13 cooperate, reducing the degree of cavitation at the sealing ring.

[0060] like Figure 2As shown, during use, the internal fuel flow of this invention is as follows: When the control valve is not open, the sealing steel ball 4 forms a seal with the conical wall of the ball valve cavity 13 of the second orifice plate 1. The control cavity 9 is connected to the connecting rail pipe 7 through the oil inlet hole 8. At this time, the fuel pressure in the control cavity 9 is the same as the rail pressure. When the control valve is opened, the valve stem 3 moves upward, and the sealing steel ball 4 moves upward with the valve stem 3, so that the guide hole 12 is connected to the ball valve cavity 13. The high-pressure fuel in the control cavity 9 flows into the ball valve cavity 13 through the oil outlet hole 11 of the intermediate chamber 10 and the guide hole 12, and finally flows to the return oil pipe through the discharge hole 14. The piston 6 is located below the control cavity 9. It does not move when the control valve is not open. After the control valve is opened, it moves upward to the designated position and stops. After the control valve is closed, it moves downward to the designated position and stops.

[0061] like Figure 4 As shown, compared with conventional injector control valves, the present invention significantly reduces the cavitation volume fraction, cavitation intensity, and cavitation range ratio of the sealing ring (as a key area), as well as the overall cavitation volume fraction, cavitation intensity, and cavitation range ratio of the injector control valve.

[0062] like Figure 4 As shown, compared with conventional injector control valves, the cavitation location of this invention is concentrated above the sealing ring (as a critical area), which shifts the cavitation that originally appeared at the sealing surface of the conical wall of the ball valve cavity 13 downstream, reducing the risk of cavitation erosion at the sealing surface of the conical wall of the ball valve cavity 13, and further improving the working efficiency, stability and service life of the injector.

[0063] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. A high-pressure common rail injector control valve, comprising a control valve housing and a valve stem; a control chamber and a mounting chamber are coaxially arranged from bottom to top inside the control valve housing; the control chamber is connected to the rail pipe through an oil inlet; characterized in that: The mounting cavity is coaxially arranged from top to bottom with a first orifice plate and a second orifice plate in close contact with each other; the four edges of the first and second orifice plates are in close contact with the inner wall of the mounting cavity; a discharge hole is provided on the first orifice plate; the second orifice plate is arranged from top to bottom with a ball valve cavity, a guide hole, an oil outlet hole and an intermediate chamber that are interconnected; the intermediate chamber is connected to the control cavity; the discharge hole is connected to the ball valve cavity; a sealing steel ball is fixedly provided at the bottom end of the valve stem; the valve stem passes through the first orifice plate and enters the ball valve cavity, the sealing steel ball is located above the guide hole and cooperates with the conical wall of the ball valve cavity; an elliptical fillet is formed at the junction of the guide hole and the ball valve cavity; the elliptical fillet is tangent to the edge of the guide hole and the edge of the conical wall of the ball valve cavity, and the major axis of the elliptical fillet is perpendicular to the axis of the second orifice plate; The length l2 of the oil outlet is calculated using the following formula: In the formula, d2 is the diameter of the oil outlet, f is the friction coefficient between the fuel and the flow channel wall, ρ is the fuel density, ΔP is the pressure difference between the inlet and outlet of the injector control valve, and n1 is an empirical constant. The diameter d1 of the intermediate chamber is calculated using the following formula: In the formula, l2 is the length of the oil outlet, d2 is the diameter of the oil outlet, g is the acceleration due to gravity, and n2 is an empirical constant; The length l1 of the intermediate chamber is calculated using the following formula: In the formula, P is the fuel injection pressure of the diesel engine where the injector is located.

2. The high-pressure common rail injector control valve according to claim 1, characterized in that: A chamfer is provided between the intermediate chamber and the oil outlet, and the chamfer angle ranges from 120° to 140°.

3. The high-pressure common rail injector control valve according to claim 1, characterized in that: The orifice diameter d3 is calculated using the following formula: In the formula, P v d2 is the saturated vapor pressure of fuel oil, n3 is an empirical constant; l3 is the length of the guide hole, d2 is the diameter of the oil outlet hole.

4. A high-pressure common rail injector control valve according to claim 1, characterized in that: The length l3 of the guide hole is calculated using the following formula: In the formula, P is the fuel injection pressure of the diesel engine where the injector is located.

5. A high-pressure common rail injector control valve according to claim 1, characterized in that: The major semi-axis a and minor semi-axis b of the elliptical fillet are calculated using the following formula: The ball valve cavity has a conical structure with a diameter at the top greater than that at the bottom. 'a' is the taper of the conical wall of the ball valve cavity, 'R' is the radius of the sealing steel ball, and the diameter of the sealing steel ball is greater than the diameter at the bottom of the ball valve cavity. 'n4', 'n5', 'n6', and 'n7' are empirical constants. 'd3' is the diameter of the guide hole, 'd2' is the diameter of the oil outlet hole, and 'l2' is the length of the oil outlet hole.

6. A high-pressure common rail injector control valve according to claim 1, characterized in that: The sealing steel ball and the conical wall of the ball valve cavity cooperate to form a sealing ring; the low-pressure zone caused by the flow separation phenomenon resulting from the change in flow direction of high-speed fuel at the junction of the guide hole and the ball valve cavity moves upward to the sealing ring; the cavitation phenomenon generated in the low-pressure zone occurs above the sealing ring.

7. A method for suppressing cavitation design of a high-pressure common rail injector control valve according to any one of claims 1-6, characterized in that: Includes the following steps: The diameter of the oil outlet hole d2 is selected based on the power requirements of the diesel engine where the injector is located. The length of the oil hole l2 is calculated using the following formula: In the formula, f is the friction coefficient between fuel and flow channel wall, ρ is fuel density, ΔP is the pressure difference between the inlet and outlet of the injector control valve, and n1 is an empirical constant. The diameter d1 of the intermediate chamber is calculated using the following formula: In the formula, g is the acceleration due to gravity, and n2 is an empirical constant; The length l1 of the intermediate chamber is calculated using the following formula: In the formula, P is the fuel injection pressure of the diesel engine where the injector is located; Determine the chamfer β between the intermediate chamber and the oil outlet, with a value ranging from 120° to 140°. The orifice diameter d3 is calculated using the following formula: In the formula, P v n is the saturated vapor pressure of fuel oil, and n3 is an empirical constant; The length l3 of the guide hole is calculated using the following formula: The taper α of the conical wall of the ball valve cavity, and the major semi-axis a and minor semi-axis b of the elliptical fillet are calculated using the following formula: Where R is the radius of the sealing steel ball, and its value ranges from 1.3 to 2.5 mm; n4, n5, n6, and n7 are empirical constants.

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