High-pressure common-rail oil injector control valve and cavitation suppression design method thereof

Abstract

The invention provides a high-pressure common-rail oil injector control valve and a cavitation suppression design method thereof. The high-pressure common-rail oil injector control valve comprises a control valve shell and a valve rod. A control cavity and a mounting cavity are formed in the control valve shell; the control cavity is communicated with the rail pipe through the oil inlet hole; a first pore plate and a second pore plate which are in close contact with each other are sequentially and coaxially arranged in the mounting cavity from top to bottom; the peripheral edges of the first pore plate and the second pore plate are in close contact with the inner wall of the mounting cavity; a discharge hole is formed in the first pore plate; a ball valve cavity, a flow guide hole, an oil outlet hole and a middle cavity which are communicated with one another are sequentially formed in the second pore plate from top to bottom; the middle cavity is communicated with the control cavity; the discharge hole is communicated with the ball valve cavity; a sealing steel ball is fixedly arranged at the bottom end of the valve rod; the valve rod penetrates through the first hole plate to enter the ball valve cavity, and the sealing steel ball is located above the flow guide hole and matched with the conical wall face of the ball valve cavity. The cavitation strength of the sealing surface of the ball valve is reduced, and the service life of the oil injector control valve is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of high-pressure common rail fuel injectors, and in particular relates to a high-pressure common rail fuel injector control valve and a design method for suppressing cavitation thereof. Background Art

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

[0003] At present, ball valve type injector control valves are commonly used in the industry. In order to ensure the high response speed of the control valve and realize the precise control of fuel injection, the ball valve sealing ball is designed to be small (the diameter is generally 1-2mm) and the ball valve lift is small (about 0.03-0.1mm). After the ball valve is opened, the fuel will produce a large pressure drop at the ball valve sealing surface, resulting in strong cavitation, causing cavitation on the metal surface of the valve seat sealing surface, and ultimately leading to failure of the control valve, affecting the overall working efficiency and life of the injector, so that there are certain safety hazards in the use of the injector. Summary of the invention

[0004] The purpose of the present invention is to solve the shortcomings of the above-mentioned background technology, to provide a high-pressure common rail injector control valve and a design method for suppressing cavitation, to change the location where cavitation occurs in the ball valve cavity, to reduce the cavitation intensity at the ball valve sealing surface, and to increase the service life of the injector control valve.

[0005] The technical solution adopted by the present invention is: a high-pressure common rail injector control valve, including 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 hole; the characteristic is that: the mounting chamber is coaxially arranged with a first orifice plate and a second orifice plate in close contact with each other from top to bottom; the edges of the first orifice plate and the second orifice plate are in close contact with the inner wall of the mounting chamber; the first orifice plate is provided with a discharge hole; the second orifice plate is provided with a plurality of A ball valve cavity, a flow guide hole, an oil outlet hole and an intermediate chamber are connected; 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 arranged at the bottom end of the valve stem; the valve stem passes through the first orifice plate into the ball valve cavity, the sealing steel ball is located above the flow guide hole and cooperates with the conical wall of the ball valve cavity; an elliptical fillet is formed at the junction of the flow guide hole and the ball valve cavity; the elliptical fillet is tangent to the edge line of the flow guide hole and the edge line 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.

[0006] The beneficial effects of the present invention are as follows: the present invention reduces the cavitation intensity in the throttle hole and the guide hole after the control valve is opened by reasonably optimizing the internal structure design of the injector control valve, so that the cavitation originally occurring at the sealing surface of the conical wall of the ball valve cavity is transferred to its downstream, thereby reducing the cavitation risk of the sealing surface of the conical wall of the ball valve cavity, and further improving the working efficiency, stability and service life of the injector.

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

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

[0009] Furthermore, the present invention designs the guide hole based on the size of the intermediate chamber, thereby reducing the generation of large-scale eddies in the guide hole and reducing the generation of cavitation in the guide hole.

[0010] Furthermore, the present invention designs the elliptical fillet based on the size of the oil outlet, the intermediate chamber and the guide hole, ensuring that the elliptical angle profile at the corner is conducive to reducing the flow separation of the fuel at the sealing surface and the upstream part of the sealing surface, avoiding the formation of a local low-pressure area; at the same time, it can reduce the conversion rate of the 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 initiation conditions, reduces the cavitation intensity at the sealing surface, and thus achieves the purpose of reducing the cavitation erosion of the sealing surface.

[0011] Furthermore, the present invention optimizes the structural matching relationship between the oil outlet hole, the intermediate chamber and the guide hole, so that the low-pressure area moves downstream, and the cavitation generated in the low-pressure area also moves downstream. The cavitation is generated at the downstream position of the sealing ring belt where the sealing steel ball and the conical wall surface of the ball valve chamber match, thereby reducing the degree of cavitation at the sealing ring belt. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0014] Figure 3 It is a schematic diagram of the design dimensions of the present invention;

[0015] Figure 4 A comparison diagram of the cavitation effects of the present invention and the prior art;

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

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

[0018] Example 1

[0019] like Figure 1-2 As shown, the present invention provides an injector control valve with an elliptical rounded throttling orifice plate, comprising a control valve housing 5 and a valve stem 3; a control chamber 9 and a mounting chamber 15 are coaxially arranged from bottom to top inside the control valve housing 5; the control chamber 9 is connected to the rail pipe through an oil inlet hole 8; the mounting chamber 15 is coaxially arranged with a first orifice plate 2 and a second orifice plate 1 in close contact with each other from top to bottom; the edges of the first orifice plate 2 and the second orifice plate 1 are in close contact with the inner wall of the mounting chamber 15; a discharge hole 14 is arranged on the first orifice plate 2; a ball valve chamber 13, a guide hole 12, an oil outlet hole 11 and an intermediate chamber 10 that are interconnected are arranged in sequence from top to bottom inside the second orifice plate 1; 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 arranged 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 matches 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 is chamfered, and the chamfer size is 1 / 15 to 1 / 10 of the diameter of the oil outlet hole 11. This structure of the present invention can reduce the cavitation degree 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 cavitation degree of the ball valve cavity 13.

[0021] Specifically, the length of the oil outlet hole 11 is l 2 The calculation is done using the following formula:

[0022]

[0023] Where, d 2 is the diameter of the oil outlet hole 11, which is selected according to the power requirement 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 inlet and outlet pressure difference of the injector control valve, which is the initial design parameter of the injector control valve; n 1 is an empirical constant.

[0024] Specifically, the diameter d of the middle chamber 10 of the second orifice plate 1 is 1The calculation is done using the following formula:

[0025]

[0026] Where g is the acceleration due to gravity, n is 2 is an empirical constant.

[0027] The length of the middle chamber 10 of the second orifice plate 1 is l 1 The calculation is done using the following formula:

[0028]

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

[0030] The chamfer angle β between the middle chamber 10 and the oil outlet hole 11 is in the range of 120°

[0031] The structural design of the intermediate chamber 10 is conducive to reducing 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 hole 11, inhibiting the flow separation caused by the sudden drop in the fuel flow area and the change in flow direction, and can effectively inhibit the cavitation phenomenon in the oil outlet hole 11, thereby reducing the cavitation intensity in the downstream guide hole 12 and the ball valve cavity 13.

[0032] Specifically, the diameter d of the guide hole 12 of the second orifice plate 1 is 3 The calculation is done using the following formula:

[0033]

[0034] Where P v is the saturated vapor pressure of fuel, n 3 Empirical constant.

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

[0036]

[0037] Wherein, 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 conducive to reducing the generation of large-scale vortices in the guide hole 12, reducing the generation of cavitation in the guide hole 12, and can reduce the flow rate of the fuel in the guide hole 12, appropriately increase the fuel pressure, accelerate the collapse of the collapsed cavitation bubbles flowing from the oil outlet hole 11 into the guide hole 12, reduce the number of cavitation bubbles flowing into the ball valve cavity 13, and reduce the cavitation degree of the ball valve cavity 13.

[0038] Specifically, Figure 3As shown, there is an elliptical fillet at the junction of the top of the guide hole 12 of the second orifice plate 1 and the ball valve cavity 13. The ellipse is tangent to the edge of the guide hole 12 and 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 the 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, usually 1.3-2.5 mm, n 4 、n 5 、n 6 、n 7 is an empirical constant. The elliptical angle profile design at the corner is conducive to reducing the flow separation of the fuel at the sealing surface and the upstream part of the sealing surface, avoiding the formation of local low-pressure areas; this design can also reduce the conversion rate of the fuel pressure energy to kinetic energy near the sealing surface, reduce the fuel velocity gradient near the sealing surface, and inhibit the formation of low-pressure areas. The reduction of the low-pressure area destroys the cavitation initiation conditions, reduces the cavitation intensity at the sealing surface, and thus achieves the purpose of reducing the cavitation erosion of the sealing surface.

[0041] Specifically, the ball valve cavity 13 is a conical structure; the diameter of the top end is larger than the bottom end; the guide hole 12 is connected to the bottom end of the ball valve cavity 13; 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, and the sealing steel ball 4 can block the inflow of fuel when closed.

[0042] Specifically, four discharge holes 14 are provided, which are symmetrically distributed above and connected to the ball valve cavity 13. The present invention can effectively discharge the fuel in the ball valve cavity 13 when the control valve is opened, ensuring the working stability and continuity of the injector.

[0043] Example 2

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

[0045] 1) Design the oil outlet hole 11: The diameter of the oil outlet hole 11 is d 2 The fuel injector is selected based on the power requirement of the diesel engine where the fuel injector is located; the fuel injector is selected based on the power of the diesel engine, and then the diameter of the oil outlet hole 11 of the fuel injector control valve can be determined; the diameter d of the oil outlet hole 11 is determined 2 Then calculate the oil hole length l according to the following formula 2 :

[0046]

[0047] In the formula, f is the friction coefficient between the fuel and the flow channel wall, ρ is the fuel density, and ΔP is the inlet and outlet pressure difference of the injector control valve, all of which are determined by the selected diesel engine. The diesel grade corresponding to the diesel engine is determined by the fuel density. The rail pressure is determined when the diesel engine is designed and finalized. The inlet pressure of the injector control valve is the rail pressure, and the outlet pressure is generally atmospheric pressure. All ΔP is generally equivalent to the rail pressure value. The friction coefficient f is the friction between the metal surface of the injector and the fuel. This value can be determined after the diesel engine is finalized. n 1 is an empirical constant.

[0048] 2) Design the middle chamber 10: Calculate the diameter d of the middle chamber 10 using the following formula: 1 :

[0049]

[0050] Where g is the acceleration due to gravity, n is 2 is an empirical constant;

[0051] Based on the diameter d of the intermediate chamber 10 1 Determine the length l of the intermediate chamber 10 1 ; The length of the intermediate chamber 10 is l 1 The value range is the diameter d of the middle chamber 10 1 2.2-2.5 times,

[0052] Determine that the value range of the chamfer angle β between the intermediate chamber 10 and the oil outlet hole 11 is 120°-140°;

[0053] 3) Design the diversion hole 12: Use the following formula to calculate the diameter d of the diversion hole 12: 3 , and then determine the length l of the guide hole 12 3 :

[0054]

[0055] Where P v is the saturated vapor pressure of the fuel, which is determined by the diesel grade corresponding to the diesel engine where the injector is located, n 3 is an empirical constant; the length of the flow guide hole 12 is l 3 The value range of the guide hole 12 aperture d 3 1.1-2.5 times;

[0056] 4) Design of ball valve cavity 13: The following formula is used to calculate the taper α of the conical wall of the ball valve cavity 13, and the major semi-axis a and minor semi-axis b of the elliptical fillet:

[0057]

[0058] Among them, R is the radius of the sealing steel ball 4, and the value range is 1.3-2.5mm, ensuring that it is larger than the radius of the oil outlet hole 11; the sealing steel ball 4 is generally a standard part, and the corresponding size is selected according to the power of the diesel engine; n 4 、n 5 、n 6 、n 7 is an empirical constant.

[0059] The structure designed by the present invention changes the position of the low-pressure area caused by the flow separation phenomenon caused by 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 present invention allows the low-pressure area to move downstream, and the cavitation generated in the low-pressure area also moves downstream. The cavitation is generated at the downstream position of the sealing ring belt where the sealing steel ball 4 and the conical wall of the ball valve cavity 13 cooperate, thereby reducing the degree of cavitation at the sealing ring belt.

[0060] like Figure 2 As shown, during use, the internal fuel flow of the present invention is as follows: when the control valve is not opened, the sealing steel ball 4 forms a seal with the conical wall of the ball valve cavity 13 of the second orifice plate 1, and 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 and the ball valve cavity 13 are in a connected state. 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, does not move when the control valve is not opened, moves upward to the specified position after the control valve is opened, and stops after moving downward to the specified position after the control valve is closed.

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

[0062] like Figure 4 As shown, compared with the conventional injector control valve, the cavitation position of the present invention is concentrated above the sealing ring (as a key area), so that the cavitation originally occurring at the sealing surface of the conical wall of the ball valve chamber 13 is transferred to its downstream, thereby reducing the cavitation risk of the sealing surface of the conical wall of the ball valve chamber 13, and further improving the working efficiency, stability and service life of the injector.

[0063] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

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 hole; characterized in that: The installation cavity is coaxially provided with a first orifice plate and a second orifice plate in close contact with each other from top to bottom; the edges of the first orifice plate and the second orifice plate are in close contact with the inner wall of the installation cavity; the first orifice plate is provided with a discharge hole; the interior of the second orifice plate is provided with a ball valve cavity, a guide hole, an oil outlet hole and an intermediate chamber which are interconnected from top to bottom; the intermediate chamber is connected with the control cavity; the discharge hole is connected with 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 into 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 line of the guide hole and to the edge line 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.

2. A high pressure common rail injector control valve according to claim 1, characterized in that: The length of the oil outlet hole l2 is calculated using the following formula: Where 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 inlet and outlet pressure difference of the injector control valve, and n1 is an empirical constant.

3. A high pressure common rail injector control valve according to claim 1, characterized in that: The diameter of the middle chamber d1 is calculated using the following formula: Where l2 is the length of the oil outlet hole, d2 is the diameter of the oil outlet hole, g is the acceleration of gravity, and n2 is an empirical constant.

4. A high pressure common rail injector control valve according to claim 1, characterized in that: The length of the middle chamber l1 is calculated using the following formula: Where P is the 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: A chamfer is provided between the middle chamber and the oil outlet hole, and the chamfer angle ranges from 120° to 140°.

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

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

8. The 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: Among them, the ball valve cavity is a conical structure, the diameter of its top is larger than that of the bottom, α is the taper of the conical wall of the ball valve cavity, R is the radius of the sealing steel ball, the diameter of the sealing steel ball is larger than the diameter of the bottom end of the ball valve cavity, n4, n5, n6, and n7 are empirical constants; d3 is the aperture of the guide hole; d2 is the diameter of the oil outlet hole; l2 is the length of the oil outlet hole.

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

10. A method for suppressing cavitation of a high-pressure common rail injector control valve according to any one of claims 1 to 9, characterized in that: The following steps are involved: The oil outlet diameter d2 is selected according to the power requirement of the diesel engine where the injector is located; The oil hole length l2 is calculated using the following formula: Where f is the friction coefficient between the fuel and the flow channel wall, ρ is the fuel density, ΔP is the inlet and outlet pressure difference of the injector control valve, and n1 is an empirical constant; The middle chamber diameter d1 is calculated using the following formula: In the formula, g is the acceleration due to gravity, and n2 is an empirical constant; The length of the middle chamber l1 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 angle β between the middle chamber and the oil outlet, the value range of which is 120°-140°; The following formula is used to calculate the diameter d3 of the diversion hole: Where P v is the saturated vapor pressure of fuel, n3 is an empirical constant; The following formula is used to calculate the diversion hole length l3: The following formula is used to calculate 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: Among them, R is the radius of the sealing steel ball, and its value range is 1.3-2.5mm; n4, n5, n6, and n7 are empirical constants.

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