Diesel fuel injector based on hollow spray structure induced by vortex cavitation in nozzle

Abstract

A diesel fuel injector based on a hollow spray structure induced by vortex cavitation in a nozzle, including a needle valve, a nozzle body, a plurality of spray holes, and a sac chamber. An axis of the needle valve coincides with an axis of the nozzle body. The spray holes are evenly distributed on a head of the nozzle body, and each have a converging conical structure. An inlet end of the spray hole is communicated with the sac chamber. The sac chamber consists of a hemispherical cavity and a cylindrical cavity.

Claims

1. A diesel fuel injector based on a hollow spray structure induced by vortex cavitation in a nozzle, comprising: a needle valve; a nozzle body; a plurality of spray holes; and a sac chamber; wherein an axis of the needle valve coincides with an axis of the nozzle body; the plurality of spray holes are evenly distributed on a head of the nozzle body, and each have a converging conical structure; an inlet end of each of the plurality of spray holes is communicated with the sac chamber; the sac chamber is hemispherical, or consists of a hemispherical cavity and a cylindrical cavity with the same diameter as the hemispherical cavity; a radius of the hemispherical cavity is R, and a height of the sac chamber is H; and 0<R≤H; a diameter of the inlet end of each of the plurality of spray holes is D.sub.in; a vertical distance between a center of a cross section of the inlet end of each of the plurality of spray holes and a bottom end of the sac chamber is h, and h<H; a distance between a bottom end face of the needle valve and an intersection of an axis of each of the plurality of spray holes and the axis of the needle valve is l; wherein when l.sub.l≤0, H>1.5D.sub.in; R<½H; and h>D.sub.in; when l.sub.0>0, 1.5D.sub.in<H<5D.sub.in; R>⅗H; and 1.2D.sub.in<h<3D.sub.in; and when l.sub.0<0 and l.sub.1>0, 1.5D.sub.in<H<5D.sub.in; t R>⅗H; and 1.2D.sub.in<h<3D.sub.in; wherein l.sub.0 is a minimum value of the l, and l.sub.1 is a maximum value of the l when the needle valve reaches a maximum lift; a head of the needle valve is conical or truncated cone-shaped; when the head of the needle valve is conical, a conical vertex angle is an included angle θ.sub.n of the head of the needle valve, and 60°≤θ.sub.n<90°; and when the head of the needle valve is truncated cone-shaped, an included angle between two generatrixes of a cross section passing through an axis of the head of the needle valve is the included angle θ.sub.n of the head of the needle valve, and θ.sub.n≤60°; and l=0 indicates that the intersection of the axis of each of the plurality of spray holes and the axis of the needle valve is located at the bottom end face of the needle valve; l<0 indicates that the intersection of the axis of each of the plurality of spray holes and the axis of the needle valve is located above the bottom end face of the needle valve; l>0 indicates that the intersection of the axis of each of the plurality of spray holes and the axis of the needle valve is located below the bottom end face of the needle valve; when the needle valve is seated, the l reaches the minimum value l.sub.0; as fuel injection starts, the needle valve is lifted and the l gradually increases until the needle valve reaches the maximum lift, and at this time the l reaches the maximum value l.sub.1; and in an ending stage of the fuel injection, the l is gradually reduced from l.sub.1 to l.sub.0.

2. The diesel fuel injector of claim 1, wherein an inclination angle θ of each of the plurality of spray holes is set to 70°≤θ≤77.5°; the inclination angle θ is an included angle formed by the axis of each of the plurality of spray holes and the axis of the needle valve; a taper coefficient K of each of the plurality of spray holes is set to 1≤K≤3; the K is calculated as $K=\frac{100\left(D_{in}-D_{\mathrm{out}}\right)}{L},$ wherein D.sub.out represents a diameter of an outlet end of each of the plurality of spray holes; and L represents a length of each of the plurality of spray holes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 schematically shows a structure of a nozzle of a diesel fuel injector according to an embodiment of the present disclosure;

(2) FIG. 2 is a partial enlarged view of a spray hole of the nozzle of the diesel fuel injector according to an embodiment of the present disclosure;

(3) FIG. 3a schematically shows a structure of a needle valve with a conical head according to an embodiment of the present disclosure;

(4) FIG. 3b schematically shows a structure of a needle valve with a truncated cone-shaped head according to an embodiment of the present disclosure;

(5) FIG. 4a schematically illustrates vortex cavitation flow state in the nozzle according to an embodiment of the present disclosure;

(6) FIG. 4b is a schematic diagram of two typical vortex-line cavitation flow states in the nozzle according to another embodiment of the present disclosure; and

(7) FIG. 5 schematically illustrates fuel atomization in a hollow spray structure formed in the diesel fuel injector according to an embodiment of the present disclosure.

(8) In the drawings, 1, needle valve; 2, nozzle body; 3, spray hole; and 4, sac chamber.

DETAILED DESCRIPTION OF EMBODIMENTS

(9) To make the objects, technical solutions, and advantages of the present disclosure clearer, the present disclosure will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the embodiments described herein are only used to explain the present disclosure, and are not intended to limit the present disclosure.

(10) The present disclosure provides a diesel fuel injector based on a hollow spray structure induced by vortex cavitation in a nozzle. By enhancing and controlling the vortex cavitation in the nozzle, the fuel jet is in a hollow spray form, allowing for optimized atomization effect of the fuel jet. As shown in FIG. 1, a diesel fuel injector is illustrated, which includes a needle valve 1, a nozzle body 2, a plurality of spray holes 3, and a sac chamber 4. An axis of the needle valve 1 coincides with an axis of the nozzle body 2. The number of the plurality of spray holes 3 is 3-8. The plurality of spray holes 3 are evenly distributed on a head of the nozzle body 2, and each have a converging conical structure. The spray holes 3 having a converging conical structure can effectively inhibit geometric induction cavitation and enhance the vortex cavitation. FIG. 2 shows a partial enlarged view of the structure of the spray hole 3. The structural parameters of the diesel engine injector are designed, which specifically include a radius of the hemispherical cavity R of the sac chamber 4, a height H of the sac chamber 4, a taper coefficient K of the spray hole 3, an inclination angle θ of each of the plurality of spray holes 3, a distance l between the bottom end face of the needle valve 1 and an intersection of an axis of each of the plurality of spray holes 3 and the axis of the needle valve 1, and an hole opening height h of the spray hole 3.

(11) The inclination angle θ of each of the plurality of spray holes 3 is set to 70°≤θ≤77.5°, which refers to an included angle formed by the axis of each of the plurality of spray holes 3 and the axis of the needle valve 1. The taper coefficient K of each of the plurality of spray holes 3 is set to 1≤K≤3, which is calculated as:

(12) $K=\frac{100\left(D_{\mathrm{in}}-D_{\mathrm{out}}\right)}{L},$
where D.sub.in and D.sub.out represent a diameter of an inlet end and an outlet end of each of the plurality of spray holes 3, respectively; and L represents a length of each of the plurality of spray holes 3.

(13) The head of the needle valve 1 is conical or truncated cone-shaped. When the head of the needle valve 1 is conical, as shown in FIG. 3a, the bottom end face of the head of the needle valve 1 is a point, the vertex angle of the head of the needle valve 1 is the included angle θ.sub.n of the head of the needle valve 1, where 60°≤θ.sub.n≤90°. When the head of the needle valve 1 is truncated cone-shaped, as shown in FIG. 3b, the bottom end surface of the head of the needle valve 1 is a surface, the included angle between two generatrixes of a cross section passing through an axis of the head of the needle valve is the included angle θ.sub.n of the head of the needle valve 1, where θ.sub.n<60°, and the height of the truncated cone is as high as possible within the allowable range of structure of the sac chamber.

(14) When the needle valve 1 is seated, the distance l between a bottom end face of the needle valve 1 and an intersection of an axis of each of the plurality of spray holes 3 and the axis of the needle valve 1 reaches the minimum value l.sub.0. Accompanying the fuel injection, the needle valve 1 is opened and the l gradually increases until the needle valve 1 reaches the maximum lift, and at this time the l reaches the maximum value l.sub.1. In the ending stage of the fuel injection, the l is gradually reduced from l.sub.1 to l.sub.0. Specifically, the seating of the needle valve 1 refers to that the needle valve 1 cannot move downwards relative to the nozzle body 2.

(15) l is the distance between a bottom end face of the needle valve 1 and an intersection of an axis of each of the plurality of spray holes 3 and the axis of the needle valve 1. l.sub.0 is the minimum value of the l, and l.sub.1 is the maximum value of the l when the needle valve 1 reaches the maximum lift.

(16) The “positive” and “negative” of the l represent the relative position between the head of the needle valve 1 and intersection of the axis of each of the spray holes 3 and the axis of the needle valve 1:

(17) l<0 indicates that the bottom end face of the needle valve 1 is closer to the bottom of the sac chamber 4 compared with the intersection of the axis of each of the plurality of spray holes 3 and the axis of the needle valve 1;

(18) l>0 indicates that the intersection of the axis of each of the plurality of spray holes 3 and the axis of the needle valve 1 is closer to the bottom of the sac chamber 4 compared with the bottom end face of the needle valve 1; and

(19) l=0 indicates that the intersection of the axis of each of the plurality of spray holes 3 and the axis of the needle valve 1 is located at the bottom end face of the needle valve 1.

(20) The sac chamber 4 consists of a hemispherical cavity and a cylindrical cavity with the same diameter as the hemispherical cavity. The radius of the hemispherical cavity is R, and the height of the sac chamber 4 is H, where 0<R≤H, and the height H of the sac chamber 4 is equal to the radius R of the hemispherical cavity plus the height of the cylindrical cavity.

(21) The structural parameters R and H of the sac chamber 4 of the fuel injector are limited by the inlet diameter D.sub.in of each of the plurality of spray holes 3, and the hole-opening height h of each of the plurality of spray holes of the fuel injector refers to a vertical distance between a center of a cross section of the inlet end of each of the plurality of spray holes and a bottom end of the sac chamber, where h<H.

(22) If l.sub.1≤0, the height H of the sac chamber is H>1.5D.sub.in, the radius R of the hemispherical cavity of the sac chamber is R<½H, and the hole-opening height h of the spray hole is h>D.sub.in.

(23) If l.sub.0>0, the height H of the sac chamber is 1.5D.sub.in<H<5D.sub.in, the radius R of the hemispherical cavity of the sac chamber is R<⅗H, and the hole-opening height h of the spray hole is 1.2D.sub.in<h<3D.sub.in.

(24) If l.sub.0<0 and l.sub.1>0, the height H of the sac chamber is 1.5D.sub.in<H<5D.sub.in, the radius R of the hemispherical cavity of the sac chamber is R>⅗H, and the hole-opening height h of the spray hole is 1.2D.sub.in<h<3D.sub.in.

(25) Specifically, in actual use, if l.sub.l<0, that is, l is always needed to be no more than 0 during the operation of the fuel injector, the height H of the sac chamber is designed to be H>1.5D.sub.in, the radius R of the hemispherical cavity of the sac chamber is designed to be R<½H, and the hole-opening height h is designed to be h>D.sub.in. If l.sub.0>0, that is, l is always needed to be more than 0 during the operation of the fuel injector, the height H of the sac chamber is designed to be 1.5D.sub.in<H<5D.sub.in, the radius R of the hemispherical cavity of the sac chamber is designed to be R>⅗H, and the hole-opening height h is designed to be 1.2D.sub.in<h<3D.sub.in. If l.sub.0<0 and l.sub.1>0, that is, l is always needed to be less than 0 or greater than 0 during the operation of the injector, the height H of the sac chamber is designed to be 1.5D.sub.in<H<5D.sub.in, the radius R of the hemispherical cavity of the sac chamber is designed to be R>⅗H, and the hole-opening height h is designed to be 1.2D.sub.in<h<3D.sub.in. The parameters H, R and h of the injector are all fixed values, and are not changed after the parameters are determined in the actual use.

(26) In addition, during the operation of the fuel injector, l is at the position of l.sub.1 for most of the time. Therefore, in actual use, whether “l.sub.0>0”, or “l.sub.0<0 and l.sub.1>0” is needed, l.sub.1 is always greater than 0, that is, during the operation of the fuel injector, l is greater than 0 for most of the time. Hence, the values of the parameters H, R and h when “l.sub.0<0 and l.sub.1>0” are required to be consistent with the range of those when “l.sub.0>0”.

(27) The fuel injector continuously generates strong vortex cavitation in the nozzle during the fuel injection, and FIGS. 4a and 4b provide schematic diagrams of two typical vortex cavitation flow states in the nozzle.

(28) The fuel jet of the injector presents a hollow spray structure with rotational flow, as shown in FIG. 5.

(29) The above embodiments are only used to illustrate the design concepts and features of the present disclosure, and the purpose thereof is to enable one of ordinary skilled in the art to understand the contents of the present disclosure and implement the present disclosure, and are not intended to limit the scope of protection of the present disclosure. Therefore, equivalent changes or modifications made according to the principles and design ideas disclosed in the present disclosure shall fall within the scope of the protection of the present disclosure.