CN101539448A

CN101539448A - Injection protective cover used for measuring air injection volume of plasma jet

Info

Publication number: CN101539448A
Application number: CN200910082580A
Authority: CN
Inventors: 王海兴; 张亚民; 魏福智; 汤海滨; 贾少霞
Original assignee: Beihang University
Current assignee: Beihang University; Beijing University of Aeronautics and Astronautics
Priority date: 2009-04-27
Filing date: 2009-04-27
Publication date: 2009-09-23
Anticipated expiration: 2029-04-27
Also published as: CN101539448B

Abstract

The invention discloses an injection protective cover used for measuring the air injection volume of a plasma jet, comprising a front end outer baffle, an inner baffle, a rear baffle, a sealing cover, a mesh support column, a mesh hold-down ring, a metal mesh and an injection air inlet duct; wherein, the front end outer baffle is fixed on a flange plate of the sealing cover and is connected with an inner screwed hole of the inner baffle by external thread; the injection air inlet duct is connected with the inner baffle at the front end by screw thread and is communicated with an inner cavity of the sealing cover; the front end of the mesh support column passes through the edges of the mesh hold-down ring and the metal mesh, and is firmly fixed at the outer edge of the inner baffle together with a hold-down nut; the rear end of the mesh support column passes through the edges of the mesh hold-down ring and the metal mesh, and is fixed at the outer edge of the rear baffle together with the hold-down nut. The injection protective cover imitates the static air in the real injection environment, and ensures the injection air to be injected out by jet flow after being decelerated by a plurality of layers of meshes instead of entering the jet flow area without being decelerated due to passing through the short cut of gaps.

Description

Be used to measure the injection protective cover of plasma jet to air injection volume

Technical field

The invention belongs to field of measuring technique, be specifically related to a kind of injection protective cover of plasma jet that be used to measure air injection volume.

Background technology

In the various practical applications of hot plasma materials processing, hot plasma occurs with pattern usually, and plasma jet has material impact therein to the injection of environmental gas.With the plasma spray coating is example, its process is that metal or nonmetal feed particles are spurted in the high-temperature part ionized gas jet that is produced by plasma generator, feed particles acceleration in the high temperature and high speed jet, heating, fusing, striking work and distortion are sprawled, and a slice connects a slice, one deck covers one deck ground and forms coating.Compare with the infrabar plasma spray coating, the plasma spray coating that carries out in the atmospheric air environment has a tangible advantage, does not promptly need complicated vacuum system, thereby can reduce production costs greatly.But this technology is used and is also run into a difficult problem, is exactly that plasma jet can be gone into a large amount of cold environment air by injection, and this often has adverse influence to coating quality.Injection advances a large amount of cold environment air of plasma jet on the one hand, cause plasma temperature and speed on the jet axis direction, to reduce rapidly, thereby be unfavorable for acceleration and the heating of feed particles in jet, be unfavorable for that particle obtains higher speed and suitable heated condition before the bump substrate, influence the quality of coating; On the other hand, the surrounding air that injection advances plasma jet increases sharply the oxygen content in the jet on the jet axial direction, form by air at the gas downstream composition of the turbulent plasma jet overwhelming majority, this can cause feed particles and baseplate material oxidation, becomes the major reason of coating quality deterioration and even coating failure and spalling failure.In order to solve an above-mentioned difficult problem of in the atmospheric air environment, carrying out plasma spray coating, normal adopt following two kinds of methods to reduce the injection of plasma jet to surrounding air: the one, the inertia shroud gas (argon) that increases with the coaxial injection of jet alleviates the injection of jet to surrounding air, studies show that and adopt this scheme that certain effect is arranged, coating quality is made moderate progress; But according to numerical simulation result, go out air content on the turbulent jet axis apart from plasma generator outlet 10cm interface and be controlled at 10% and need up to more than 3.75 times of generator self working gas strength if will make with the interior shielding argon flow amount that then increases, and at distance generator exports 10.5cm place, if the air content in the argon plasma turbulent jet is reduced to 46% from 82%, the speed of shroud gas must be up to 100m/s; As seen inertia shielding gas shiled can only be used for the less demanding materials processing occasion of material oxidation, and the cost that need pay is quite big; Another kind method is exactly to add the solid protective cover coaxial with jet in the jet outside, stops surrounding air flowing to jet.

Summary of the invention

The objective of the invention is to design a kind of plasma jet of can accurately measuring normal atmosphere is depressed the protective cover of surrounding air injection volume, thereby help to carry out the characteristic research and the application of article on plasma body jet.Adopt the method for jet injection protective cover to measure plasma jet to be to the principle of the injection volume of surrounding air: with injection protective cover with plasma jet and external environment air insulated; manually introduce then by injection gas in injection protective cover; to be reduced near zero by injection gas speed by the multiple layer metal silk screen; to simulate surrounding air static in the true atmosphere; when being equaled the static pressure of external environment atmosphere by the static pressure of injection gas in the wire gauze; what promptly expression was imported is just in time equaled the gas flow that the plasma jet injection is walked by the injection airshed, so just can be by measuring the gas flow that be obtained the plasma jet injection by the flow of injection gas.

The invention provides a kind of injection protective cover of plasma jet that be used to measure to air injection volume, described injection protective cover is cylindrical injection protective cover, comprise front end outer baffle, Internal baffle, backboard, seal closure, silk screen support column, silk screen hold-down ring, wire gauze and injection gas entry conductor, the front end outer baffle links together by external thread and Internal baffle internal thread hole, and has the ambroin ring to make electrical isolation between front end outer baffle and Internal baffle jet inlet central through hole and plasma generator outlet counterface; Injection gas entry conductor is with being threaded on the front end outer baffle, and injection gas enters the back thus to be stopped by Internal baffle and transfer Radial Flow to; The silk screen support column passes the silk screen hold-down ring and the wire gauze edge is fixed on the Internal baffle outer rim tightly with gland nut, the silk screen hold-down ring compresses the wire gauze edge, the tinsel net volume is cylindric for three to four layers, provide axially and support radially by the silk screen support column, by being threaded togather, housing screw passes the silk screen hold-down ring and the wire gauze edge screws in the internal thread hole of silk screen support column one end at other end silk screen support column and housing screw.Outer circle column type seal closure and front end outer baffle and backboard are connected by fastening bolt, the clamp nut on the flange separately, between the flange in addition rubber washer to guarantee impermeability.The injection cover inner adopt the multiple layer metal silk screen as porous wall to reduce the influence of manually-injected gas article on plasma body jet flow field, static air in the atmosphere under the simulation true environment, when the gas of introducing outside the porous wall equates with the pressure of ambient atmosphere, just can measure the injection volume of plasma jet like this to surrounding environment gas.

The jet inlet perforate of described front end outer baffle and Internal baffle is the diameter decision of central through hole size by the outlet counterface of institute's using plasma generator, described injection gas entry conductor external diameter is 6mm, internal diameter is 4mm, described front end outer baffle and Internal baffle inside surface parallel distance are 7mm, described wire gauze outermost layer and injection cover inner surface distance are 5mm, described injection cover can adopt different length in the axial direction with the cylinder that wire gauze surrounds, described backboard jet opening diameter is 70mm, and described silk screen support column adopts the standard component double-screw bolt.

The invention has the advantages that:

1) injection cover of the present invention can use the metallic cylinder of different length, uses with the wire gauze cylinder collocation of corresponding axial length simultaneously, can be used on the measuring distance plasma generator outlet different length plasma jet to the injection volume of surrounding air; Determining of backboard jet exit diameter is by what some injection experiments back was determined jet to be penetrated the minimum final size of influence.

2) thus the present invention adopts Internal baffle that manually-injected injection gas is constituted to be stopped air flow divert is sharply reduced its speed, and further adopt the multiple layer metal silk screen to surround cylinder to constitute the porous wall structure and the injection gas velocity is reduced to approaches zero, to simulate static air under the true injection environment.For keeping the wire gauze cylinder in the regular shape that axially makes progress with the footpath, adopt the cooperation of double-screw bolt as strut and hold-down ring, make wire gauze accomplish the tensioning of rule; In addition, such structural design has guaranteed that also the wire gauze edge does not have bigger slit, has guaranteed that injection gas all walked by the jet injection by the multi-layer silk screen back of slowing down, rather than walks the slit shortcut and be not decelerated and just enter the fluerics.

Description of drawings

The assembling assumption diagram of Fig. 1 plasma jet injection protective cover;

Fig. 2 is a front end outer baffle structural profile synoptic diagram;

Fig. 3 is the baffle structure diagrammatic cross-section;

Fig. 4 is an injection gas entry conductor diagrammatic cross-section;

Fig. 4 a is an injection gas entry conductor vertical view.

Among the figure:

1, front end outer baffle 2, Internal baffle 3, backboard 4, seal closure 5, silk screen support column

6, silk screen hold-down ring 7, wire gauze 8, injection gas entry conductor 9, ambroin ring

10, gland nut 11, clamp nut 12, housing screw 13, rubber washer

14, fastening bolt

Embodiment

Below in conjunction with drawings and Examples plasma jet injection protective cover of the present invention is elaborated.

Be illustrated in figure 1 as and measure the jet injection protective cover that plasma jet injection gas flow parameter is used; described jet injection protective cover mainly comprises front end outer baffle 1; Internal baffle 2; backboard 3; seal closure 4; silk screen support column 5; silk screen hold-down ring 6; wire gauze 7 and injection gas entry conductor 8; described seal closure 4 is the cylindrical flange plate structure that has; described silk screen hold-down ring 6 is close to seal closure 4 inwalls with wire gauze 7 two edges and is compressed; described front end outer baffle 1 is fixed on the ring flange on the seal closure 4; front end outer baffle 1 links together by external thread and Internal baffle 2 internal thread holes 203 simultaneously, and described injection gas entry conductor 8 is threaded on the front end Internal baffle 1 and with seal closure 4 inner chambers and communicates.Described silk screen support column 5 front ends pass silk screen hold-down ring 6 and wire gauze 7 edges, are fixed on tightly on Internal baffle 2 outer rims with gland nut 10; Silk screen hold-down ring 6 and wire gauze 7 edges are passed in silk screen support column 5 rear ends, are fixed on backboard 3 outer rims with gland nut 10.

Described front end outer baffle 1 is a disc-shaped structure, as shown in Figure 2, the both sides in disk centre position are provided with cylindrical boss 102, boss 102 has central through hole 101, described boss 102 1 sides are external thread, and opposite side is smooth cylinder, and front end outer baffle 1 disk border circumferentially is evenly equipped with 8 6mm diameter through hole 103, circumferentially uniform four internal thread air admission holes 104 are used for being connected with injection gas entry conductor 8 between the margin and center through hole 101.

Described Internal baffle 2 also is a disc-shaped structure, disc centre is a central through hole 202, be evenly equipped with the through hole 204 of 8 3mm diameters on the disk, as Fig. 3, Internal baffle 2 one sides have boss 201, boss 201 centers are internal thread hole 203, and internal thread hole 203 matches with front end outer baffle 1 convex platform 102 external threads and realizes being connected.Described internal thread hole 203 communicates with the central through hole 202 of Internal baffle 2 disc-shaped structures, when front end outer baffle 1 and Internal baffle 2 by boss 102 external thread and after boss 201 internal thread holes 203 closely link together, 202 one-tenth as a whole equal diameter through holes of both central through holes 101 and central through hole have ambroin ring 9 to make electrical isolation between this through hole and the plasma generator outlet counterface.

As Fig. 4, injection gas entry conductor 8 one ends 801 are external thread, and the shaft shoulder 803 places cut two parallel planes 805 so that use the spanner clamping, shown in Fig. 4 a.802 turning of injection gas entry conductor 8 other ends go out three circle wedge-shaped slots 804 makes the effect of playing the sealing slip-off preventing when putting tracheae, injection gas entry conductor 4 usefulness are threaded on four internal thread air admission holes 104 of front end outer baffle 1, and injection gas enters the back thus to be stopped by Internal baffle 2 and to transfer Radial Flow to.

Described backboard 3 is a disc-shaped structure, and as Fig. 1, backboard 3 centers have central through hole 301 as jet exit, circumferentially are evenly equipped with the through hole 302 of 8 3mm diameters between central through hole 301 and the disk border, and is corresponding with eight through holes 201 on the Internal baffle 2; The edge that these through holes 201 and through hole 301 and silk screen hold-down ring 6 and wire gauze 7 are passed in eight circumferential uniform silk screen support column 5 two ends is fixed on Internal baffle 2 and backboard 3 outward flanges tightly with gland nut 10, wire gauze 7 volumes are cylindric for three to four layers, are provided axially and support radially by silk screen support column 5; Column type seal closure 4 is the flanged structure of cylindrical shape, have 8 6mm diameter through hole on the flange, through hole, rubber washer 13 and front end outer baffle 1 edge through hole 103 that fastening bolt 14 passes on column type seal closure 4 flanges closely link together the three with clamp nut 11, and fastening bolt 14 passes on through hole, rubber washer 13 and backboard 3 edges on column type seal closure 4 flanges through hole 302 and with clamp nut 11 three closely linked together.

Front end outer baffle 1, Internal baffle 2, seal closure 4, injection gas entry conductor 8, silk screen hold-down ring 6, backboard 3 all adopt mild carbon steel to make through machining.Silk screen support column 5 adopts standard component M3 double-screw bolt, and it is the stainless steel cloth of 1mm that wire gauze 7 adopts mesh, and gland nut 10, housing screw 12, fastening bolt 14, clamp nut 11 all adopt standard component.

Claims

1, be used to measure the injection protective cover of plasma jet to air injection volume, it is characterized in that: mainly comprise the front end outer baffle, Internal baffle, backboard, seal closure, the silk screen support column, the silk screen hold-down ring, wire gauze and injection gas entry conductor, described seal closure is the cylindrical flange plate structure that has, described silk screen hold-down ring is close to the seal closure inwall with the wire gauze two edges and is compressed, described front end outer baffle is fixed on the ring flange on the seal closure, the front end outer baffle links together by external thread and Internal baffle internal thread hole simultaneously, and described injection gas entry conductor is threaded on the front end Internal baffle and with the seal closure inner chamber and communicates; Described silk screen support column front end passes silk screen hold-down ring and wire gauze edge, is fixed on tightly on the Internal baffle outer rim with gland nut; Silk screen hold-down ring and wire gauze edge are passed in silk screen support column rear end, are fixed on the backboard outer rim with gland nut.

2, according to claim 1ly be used to measure the injection protective cover of plasma jet to air injection volume; it is characterized in that: described front end outer baffle is a disc-shaped structure; the both sides in disk centre position are provided with cylindrical boss; boss has central through hole; described boss one side is an external thread; opposite side is smooth cylinder; front end outer baffle disk border circumferentially is evenly equipped with through hole; circumferential uniform internal thread air admission hole between the margin and center through hole is used for being connected with injection gas entry conductor.

3; according to claim 1ly be used to measure the injection protective cover of plasma jet to air injection volume; it is characterized in that: described Internal baffle is a disc-shaped structure; disc centre is a central through hole; be evenly equipped with through hole on the disk; Internal baffle one side has boss; the boss center is an internal thread hole; described internal thread hole communicates with the central through hole of Internal baffle disc-shaped structure; when front end outer baffle and Internal baffle by boss external thread and after the boss internal thread hole closely links together; both central through holes become as a whole equal diameter through hole, have the ambroin ring to make electrical isolation between this through hole and the plasma generator outlet counterface.

4, according to claim 1ly be used to measure the injection protective cover of plasma jet to air injection volume; it is characterized in that: injection gas entry conductor one end is an external thread; shaft shoulder place cuts two parallel planes so that use the spanner clamping; the turning of the injection gas entry conductor other end goes out the effect of playing the sealing slip-off preventing when wedge-shaped slot is feasible to put tracheae; injection gas entry conductor is with being threaded on four internal thread air admission holes of front end outer baffle, and injection gas enters the back thus to be stopped by Internal baffle and transfer Radial Flow to.