CN1808089A - Horizontal pumping system and pumping control method for automobile wind tunnel - Google Patents

Abstract

The invention relates to a system for pumping horizontally on wind tunnel of vehicles and a method for controlling pumping. The system comprises: wind tunnel spout, pumping spout seal, horizontal pumping slot, air flow pumping pipe, flow counter, differential pressure sensor, PLC controller and variable-frequency controller; under the wind tunnel spout being placed the pumping spout, on the front edge being connected with pumping spout seal, on the upper, lower ends of the front edge being connected with the differential pressure sensor; on one end of the flowing counter being connected with the pumping spout, the other end being connected with pumping machine which is connected with the variable-frequency controller; the variable-frequency controller, differential pressure sensor, and the flow counter are respectively connected with the PLC controller. The method comprises: making air flow for testing enter downstream diffusion stage of testing via the inventive device, in front of the testing vehicle forming wind speed profile, selecting different pumping spout seal, adjusting the opening of the pumping spout; calibrating the pressure differential vs. testing wind speed, flow vs. testing wind speed and rotary speed vs. testing wind speed three action control curve, comparing the real pumping flow with the real pressure differential of the upper, lower edges of pumping spout and the calibration curve data.

Description

The horizontal suction system of automobile wind tunnel and suction control method

Technical field

The invention belongs to aerodynamics and Vehicle Engineering technical field, be specifically related to a kind of horizontal suction system and suction control method of automobile wind tunnel.

Background technology

There is relative motion in automobile between air and the automobile, gas velocity U in the process of travels down ₀Equal the travel speed of automobile, the gas velocity in automobile head the place ahead equals constant in short transverse, promptly so-called " evenly wind profile ".Yet in wind-tunnel, owing to there is the solid wall surface boundary layer, inhomogeneous by the wind profile in instruction carriage the place ahead, the existence in boundary layer makes the analog distortion of air-flow in the wind-tunnel, particularly the airflow characteristic and the reality of automobile bottom are more different again, and then influence the accuracy that aerodynamic force is measured.In order to eliminate or to weaken effect of boundary layer in the automobile wind tunnel, be necessary to set up uniform mean wind speed section as far as possible, developed basic suction (Basic suction) and peripheric jet flow (Tangential blowing) two type systematics for this reason in the world in vehicle front.Basis suction and peripheric jet flow degree can reduce boundary layer thickness, form and approach uniform wind profile, but they have significant disadvantages separately:

(1) shortcoming of basis suction: vertical suction airstream produces tangible static-pressure gradient in the whole test section, influences aerodynamic force and measures;

(2) shortcoming of peripheric jet flow: peripheric jet flow be easy to generate the air-flow drift angle.

Two kinds of traditional boundary-layer control systems of this explanation all can reduce the quality in test section flow field.Therefore, research is a kind of can reduce the automobile wind tunnel surface boundary layer but not influence the test section flow field quality and automobile wind tunnel horizontal suction system that static pressure gradient distributes is those skilled in the art's a goal in research.

Summary of the invention

The objective of the invention is to propose a kind of horizontal suction system and suction method that reduces the automobile wind tunnel surface boundary layer, do not influence the automobile wind tunnel of test section flow field quality and static pressure gradient distribution.

The horizontal suction system of the automobile wind tunnel that the present invention proposes, form by wind tunnel spout 1, pump orifice sealing 5, horizontal suction socket 6, suction airstream pipeline 7, flowmeter 8, sucktion fan 9, differential pressure pick-up 12, PLC controller 13 and variable-frequence governor 14, wherein, wind tunnel spout 1 outlet below is provided with horizontal suction socket 6, form pump orifice 15, the leading edge of pump orifice 15 connects pump orifice sealing 5, the leading edge upper and lower end of pump orifice 15 is provided with pressure tap 11, and pressure tap 11 connects differential pressure pick-up 12 by piezometric tube; One end of flowmeter 8 connects pump orifice 15 by suction airstream pipeline 7, and the other end connects sucktion fan 9 by pipeline, and sucktion fan 9 connects variable-frequence governor 14 by power cable; Variable-frequence governor 14, differential pressure pick-up 12, flowmeter 8 connect PLC controller 13 by signal cable respectively.

Among the present invention, the leading edge of pump orifice 15 is a kind of of semiellipse arc or sharp-edged.

The suction control method of the horizontal suction system of the automobile wind tunnel that the present invention proposes, its concrete steps are as follows:

(1) tested air-flow enters the boundary layer that forms before the test chamber, enter by horizontal suction system in first diffuser in test section downstream, form uniform vertical velocity section at the experiment vehicle front, below the outlet of vehicle wind tunnel spout, offer horizontal suction socket, form pump orifice, pump orifice is positioned at spout and exports inboard L _Ex, the height of pump orifice is H _ScSelect different pump orifice sealings, regulate the pump orifice aperture; The height H of pump orifice _ScBe 0～1 times of boundary layer thickness, for car load wind-tunnel, L _ExIn 0～200mm scope; As selecting H _Sc=0,0.25,0.50, pump orifice maximum height such as 0.75 and 1.0 times, i.e. state such as pump orifice full cut-off, 25%, 50%, 75% to 100% aperture.

(2) demarcate pressure reduction-The test wind, flow-The test wind and three suction system operations of rotating speed-The test wind control curve:

To each pump orifice aperture, formulate the The test wind point, wind speed is from 5m/s to U _Max, each point The test wind step difference is 2～5m/s, for car load wind-tunnel, U _MaxIn 60～70m/s scope;

To each The test wind point, regulate the rotating speed of sucktion fan and the flow of flowmeter respectively, and detect the pressure differential deltap P of the upper and lower pressure tap of pump orifice leading edge by differential pressure pick-up ₁₂, Δ P ₁₂=P ₁-P ₂, to Δ P ₁₂Be the parallel reference value of a certain proof air-flow (as being zero), record Δ P ₁₂Sucktion fan rotation speed n, the flow Q of reference value when (as being zero) that a certain proof air-flow is parallel, Δ P ₁₂Be the pressure reduction of pressure tap up and down, P ₁Be the pressure of last pressure tap, P ₂Pressure for following pressure tap;

To pressure reduction, rotating speed and the flow measurement of the different tests wind speed point chosen, set up pressure reduction-The test wind, flow-The test wind and three suction systems operations of rotating speed-The test wind control curve; The operation curve data of different opening are stored in the PLC controller with list data storehouse form, call for operation control;

(3) operation control:

The pump orifice sealing that needs is installed, fixing horizontal pump orifice aperture;

Call corresponding aperture sucktion fan rotating speed-wind tunnel test wind speed curve tables of data, adopt variable-frequence governor to set the sucktion fan rotating speed, and the operation level suction system; If the wind tunnel test wind speed is not being demarcated on the wind speed point, adopt front and back calibration point interpolation to determine;

Measure actual suction flow and the upper and lower surperficial pressure reduction of actual pump orifice leading edge, with the calibration curve data that obtain in itself and the step (2) relatively, system normally moves in＜1% error allowed band; When exceeding 1% permissible error, by increasing or reduce the correction of sucktion fan rotating speed, up to the upper and lower surperficial pressure reduction of pump orifice leading edge and flow error all in allowed band.

Among the present invention, eliminate or reduce the boundary layer of vehicle front in wind-tunnel, stream field quality and pneumatic acoustic experiment ground unrest influence simultaneously is very little.For this reason, at spout outlet (slightly going deep into spout inside) design level notch, the low speed flow in boundary layer is discharged test section by suction system, near the air-flow than low velocity avoiding is drawn into the test section downstream, thereby forms uniform wind profile in vehicle front; At pump orifice the place ahead design flow line style packoff, be used to regulate the pump orifice aperture, when needs carried out the aeroacoustics test, the pump orifice complete closed can not produce any additional background noise herein.

Among the present invention, the pump orifice height H _ScDepend on the thickness in boundary layer herein.For the car load wind-tunnel, avoid the boundary layer thickness that forms relevant in spout bottom with the length of spout.The sealing of airflow design is arranged before the pump orifice, carry out the aerodynamics laboratory at automobile wind tunnel, sealing is opened, suction system work; When needs carry out the noise measurement experiment, can suction system be closed with sealing, in order to avoid notch produces additional noise.

The present invention adopts semiellipse arc and two kinds of pump orifice leading edges of sharp-edged, and the leading edge upper and lower surface is provided with pressure tap P ₁And P ₂Whether be used to detect air-flow parallel.This differential pressure coefficient of 2 (with test section mean wind speed nondimensionalization) has clear and definite corresponding relation with best suction flow, particularly when changing model, best suction flow often also needs to adjust, and the benchmark of its adjustment is formally realized by this pressure survey of 2.

Among the present invention, maximum The test wind suction flow: Q _{Sc, max}≈ W _NozzleH _ScU _Max, W wherein _NozzleBe the width of wind tunnel spout, U _MaxBe the maximum The test wind of wind tunnel operation.

Among the present invention, the loss of total pressure of suction runner: $\mathrm{\Δ}{P}_{\max }={\mathrm{\ξ}}_{\mathrm{sc}}\·\frac{1}{2}\mathrm{\ρ}{U}_{\max }^2,$ ξ wherein _ScFor utilizing the suction runner pressure drop coefficient of wind tunnel test wind speed nondimensionalization, ρ represents atmospheric density.

Among the present invention, sucktion fan and frequency conversion drive electricity rated power: P _Fan=Δ P _MaxQ _Max/ η _Fan, P _Drive=P _Fan/ η _Drive, η wherein _FanEqual sucktion fan efficient, η _DriveEqual the overall efficiency of motor and frequency conversion drive.

Among the present invention, the suction system range of adjustment: suction flow is from 0～100%Q _{Sc, max}

Suction system is as a subsystem of wind-tunnel, and it has the PLC control of oneself, and the operation of whole wind-tunnel simultaneously is by the operation of wind-tunnel TT﹠C system, and ICP/IP protocol is adopted in the communication between wind-tunnel TT﹠C system and the subsystem PLC.If adopt traditional control model not have independent PLC control, but all adopt wind-tunnel TT﹠C system direct control, the stability of system and poor expandability.And the present invention has independent PLC control system, reserves and wind-tunnel TT﹠C system interface (TCP/IP) simultaneously, and all demarcation, measurement and control can be passed through the operated from a distance of wind-tunnel TT﹠C system.

For the validity of verification system, the inventor has carried out wind tunnel model test.Design and installation one monoblock is raised the floor on model wind tunnel test section floor, the front portion of raising the floor is connected with basic suction system, and the dummy level suction system, the rear portion is as new test section floor.Experimental result reveal competence suction system is simulated the effect of even wind profile, and compares without any suction, and the gas velocity homogeneity of automotive front has very significantly to be improved; And test section static-pressure gradient curve during horizontal suction system work, horizontal suction system is to the almost not influence of test section static pressure distribution, and basic suction system produces very significantly static-pressure gradient.Evidence, horizontal suction system can reach the purpose of anticipation fully.

Beneficial effect of the present invention: the present invention can simulate even wind profile effectively, remove of the influence of wind-tunnel boundary layer, overcome negative effects such as test section static-pressure gradient that traditional boundary layer control method such as basic suction or peripheric jet flow produces or air-flow drift angle simultaneously the automotive aerodynamics experiment.

Description of drawings

Fig. 1 is a structural diagrams of the present invention.

Fig. 2 is pump orifice enclosed switch of the present invention constitutional diagram, and wherein (A) opens for the pump orifice sealing, (B) closes for the pump orifice sealing.

Fig. 3 is the mean wind speed section after the level suction (with no aspiration phases comparison).

Fig. 4 is the static pressure gradient after the front end level suction (with not having suction and basis suction relatively).

Number in the figure: 1 is wind tunnel spout, and 2 is test chamber, and 3 is the wind-tunnel collection section, 4 is the wind-tunnel diffuser, and 5 are the pump orifice sealing, and 6 is horizontal suction socket, 7 is the suction airstream pipeline, and 8 is flowmeter, and 9 is sucktion fan, 10 are the suction return air inlet, 11 is pump orifice leading edge pressure tap, and 12 is differential pressure pickup, and 13 is the PLC controller, 14 is variable-frequence governor, and 15 is pump orifice.

Embodiment

Further specify the present invention below by embodiment.

Embodiment 1

By mode shown in Figure 1, the person skilled in art all can smooth implementation with following parts.Wind tunnel spout 1 outlet below is provided with horizontal suction socket 6, forms pump orifice 15, and pump orifice 15 extends L in spout _Ex=200mm, the maximum height H of pump orifice 15 _Sc=20mm, the leading edge of pump orifice 15 connects pump orifice sealing 5, and the leading edge upper and lower end of pump orifice 15 is provided with pressure tap 11, and pressure tap 11 connects differential pressure pick-up 12 by piezometric tube; The model of differential pressure pick-up 12 is the 1151DR differential pressure transmitter, one end of flowmeter 8 connects pump orifice 15 by suction airstream pipeline 7, the other end connects sucktion fan 9 by pipeline, the model of flowmeter 8 is a LGW standard Venturi tube-type spreader, the model of sucktion fan 9 is a GD50F pipeline propeller fan, sucktion fan 9 connects variable-frequence governor 14 by power cable, the model of variable-frequence governor 14 is ACS401, variable-frequence governor 14, differential pressure pick-up 12, flowmeter 8 connect PLC controller 13 by signal cable respectively, and the model of PLC controller 13 is Simens S7.The pump orifice leading edge designs for semi arch, leading edge upper and lower surface pressure differential deltap P=P ₁-P ₂=0 expression air-flow is parallel, maximum The test wind U _MaxBe 80m/s.Suction back boundary layer thickness is less than 2mm, and the test section static pressure gradient approximates zero.

(1) the pump orifice aperture is regulated: change the pump orifice sealing of different-thickness, realize the pump orifice setting of differing heights, two kinds of extremity test: H of this employing _Sc=0 and 1.0 times of pump orifice maximum height, i.e. pump orifice full cut-off and standard-sized sheet.

(2) demarcate the control curve: except the pump orifice full cut-off does not need system works, the pump orifice full-gear is carried out operation curve demarcate, demarcating steps is as follows:

1. corresponding pump orifice sealing is installed, regulates the pump orifice aperture;

2. move wind-tunnel, The test wind from 5m/s to maximal value U _MaxPointwise is risen, and the each point The test wind step differs from 2～5m/s;

3. each The test wind point is regulated sucktion fan rotating speed and flow, and detects pump orifice leading edge upper and lower surface pressure differential deltap P ₁₂=P ₁-P ₂, up to Δ P ₁₂Equal zero survey record Δ P ₁₂Sucktion fan rotation speed n when equalling zero, flow Q;

4. finish pressure reduction, rotating speed and the flow measurement of each The test wind point, set up pressure reduction-The test wind, flow-The test wind and three suction system operations of rotating speed-The test wind control curve.

5. the operation curve data with each aperture are stored in PLC with list data storehouse form, call for operation control.

(3) operation control:

1. the pump orifice sealing that needs is installed, fixing horizontal pump orifice aperture;

2. call corresponding aperture sucktion fan rotating speed-wind tunnel test wind speed curve tables of data, directly set the sucktion fan rotating speed with variable-frequence governor according to the wind tunnel test wind speed, and the operation suction system; If the wind tunnel test wind speed is not being demarcated on the wind speed point, adopt front and back calibration point interpolation to determine;

3. measure actual suction flow and actual pump orifice leading edge upper and lower surface pressure reduction, itself and calibration curve data are compared, (＜1%) system normally moves in the error allowed band; When exceeding permissible error by increasing or reduce suction flow (sucktion fan rotating speed) correction, up to pressure reduction and flow error all in allowed band; If can not revise, system stops maintenance, perhaps demarcates the control curve again.

Can find out obviously that from Fig. 3 suction front and rear side thickness of boundary layer is reduced to about 2mm from about 25mm.

Adopt the present invention to two of the related streams field measurement test chamber boundary layer thickness in downstream and static pressure gradient along tunnel axis.

(1) boundary layer thickness is measured:

Surveying instrument: stagnation pressure or dynamic and static pressure pitot tube, move and survey frame, pressure transducer (range 0～3000Pa), data acquisition system (DAS), the mean wind speed of measurement space position

Measure content: the mean wind speed of choosing 5 kinds of pump orifice apertures (comprising full cut-off) different tests wind speed and different spatial is along the height profile section, and it is as follows to measure content and step:

The first step: set the pump orifice aperture;

Second step:, confirm working properly according to the operation control whole suction system of curve motion (except full cut-off);

The 3rd step: regulate the wind tunnel test wind speed, be respectively 10m/s, 20m/s, 30m/s, 40m/s ... up to maximum wind velocity;

The 4th step: survey frame adjusting pitot tube position with moving, move along the test chamber axis, corresponding locus is

-apart from wind tunnel spout exit coordinates x (mm): 0,250,500,1000 ... up to the test chamber center of turntable

-each x coordinate points, vertical coordinate z (mm): 5,10,20,30,40,50,60,80,100 ... up to outer layer of boundary layer (about 600mm).

The dynamic pressure numerical value of-data acquisition each point, and the corresponding mean wind speed U that converts (x, z).

Data analysis and result: calculate definition computation bound layer thickness with boundary layer thickness, as δ ₉₉, δ ^*, δ ^*

(2) static pressure gradient along tunnel axis is measured

Surveying instrument: static pressure or dynamic and static pressure pitot tube, move and survey frame, pressure transducer (range 0～3000Pa), data acquisition system (DAS), the static pressure of measurement space position.

Measure content: the mean wind speed of choosing 5 kinds of pump orifice apertures (comprising full cut-off) different tests wind speed and different spatial is along the height profile section, and it is as follows to measure content and step:

The first step: set the pump orifice aperture;

Second step:, confirm working properly according to the operation control whole suction system of curve motion (except full cut-off);

The 3rd step: regulate the wind tunnel test wind speed, be respectively 10m/s, 20m/s, 30m/s, 40m/s ... up to maximum wind velocity;

The 4th step: survey frame adjusting pitot tube position with moving, move along the test chamber axis, corresponding locus is

-vertical coordinate z (mm): 50,100,150,200 ..., 1000

-each vertical coordinate z, apart from wind tunnel spout exit coordinates x (mm): 0,100,200,300 ... up to the porch that test chamber is collected mouthful

The static pressure numerical value of-data acquisition each point, and P (x, z).

Data analysis and result: calculate the static pressure coefficient space distribution $C_P(x,z)=\frac{P(x,z)}{1/2\mathrm{\&rho;}{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="A20061002392000101.png"\; state="\{\{state\}\}">U</figure-callout>}}^2},$ ρ is an atmospheric density, and the U mean wind speed obtains the test section static-pressure gradient $\frac{d{C}_P(x,z)}{\mathrm{dx}}=\frac{\mathrm{dP}(x,z)/\mathrm{<figure-callout\; id="1"\; label="dx"\; filenames="A20061002392000101.png"\; state="\{\{state\}\}">dx</figure-callout>}}{1/2\mathrm{\&rho;}{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="A20061002392000101.png"\; state="\{\{state\}\}">U</figure-callout>}}^2}.$ Can find out obviously that from Fig. 4 traditional test section that is pumped in produces very big static-pressure gradient, and horizontal suction system changes the static pressure distribution of test section hardly.

Claims (3)

1. A horizontal suction system for an automobile wind tunnel, consisting of a wind tunnel nozzle (1), a suction port seal (5), a horizontal suction groove (6), a suction airflow duct (7), and a flow meter (8) , a suction fan (9), a differential pressure sensor (12), a PLC controller (13) and a frequency converter (14), which is characterized in that a horizontal suction groove (6) is set below the outlet of the wind tunnel nozzle (1) , forming a suction port (15), the front edge of the suction port (15) is connected to the suction port seal (5), the upper and lower ends of the suction port (15) are provided with pressure measuring holes (11), and the pressure measurement The hole (11) is connected to the differential pressure sensor (12) through the pressure measuring tube; one end of the flow meter (8) is connected to the suction port (15) through the suction air flow pipe (7), and the other end is connected to the suction fan (9) through the pipe , the suction fan (9) is connected to the frequency converter (14) through a power cable; the frequency converter (14), the differential pressure sensor (12), and the flowmeter (8) are respectively connected to the PLC controller (13) through a signal cable . 2. The horizontal suction system of an automobile wind tunnel according to claim 1, characterized in that the front edge of the suction port (15) is one of a semi-elliptical arc or a sharp edge. 3. A suction control method for a horizontal suction system of an automobile wind tunnel as claimed in claim 1, wherein the specific steps are as follows: (1) The measured air flow enters the boundary layer formed before the wind tunnel test section, and enters the first diffusion section downstream of the test section through the horizontal suction system, forming a uniform vertical wind speed profile in front of the test vehicle, and at the exit of the vehicle wind tunnel nozzle A horizontal suction groove is set at the bottom to form a suction port, the suction port is located at the inner side of the nozzle outlet L _ex , the height of the suction port is H _sc ; choose different suction port seals, and adjust the opening of the suction port; the height of the suction port H _sc is 0-1 times the thickness of the boundary layer, and for the vehicle wind tunnel, L _ex is 0-200mm; (2) Calibration pressure difference-test wind speed, flow-test wind speed and rotational speed-test wind speed three suction system operation control curves: For each suction port opening, set the test wind speed point, the wind speed is from 5m/s to U _max , and the test wind speed step difference at each point is 2-5m/s. For the wind tunnel of the whole vehicle, U _max is 60-70m/s ; For each test wind speed point, adjust the speed of the suction fan and the flow rate of the flowmeter respectively, and detect the pressure difference ΔP ₁₂ between the upper and lower pressure measuring holes on the front edge of the suction port through the differential pressure sensor, ΔP ₁₂ =P ₁ -P _2. To ΔP ₁₂ is a reference value that proves that the airflow is parallel. Record the suction fan speed n and flow Q when ΔP ₁₂ is a reference value that proves that the airflow is parallel. ΔP ₁₂ is the pressure difference between the upper and lower pressure measuring holes, P ₁ is the pressure of the upper pressure measuring hole, _P2 is the pressure of the lower pressure measuring hole; For the pressure difference, speed and flow measurement of different test wind speed points, three suction system operation control curves are established: pressure difference-test wind speed, flow-test wind speed and speed-test wind speed; the operation curve data of different openings are in the form of table database Stored in the PLC controller for operation control calls; (3) Operation control: Install the required suction port seal and fix the horizontal suction port opening; Call the corresponding opening suction fan speed-wind tunnel test wind speed curve data table, use the frequency converter to set the suction fan speed, and run the horizontal suction system; if the wind tunnel test wind speed is not at the calibrated wind speed point, use the front and rear Calibration point interpolation determination; Measure the actual suction flow rate and the actual pressure difference between the upper and lower surface of the front edge of the suction port, and compare it with the calibration curve data obtained in step (2). The system operates normally within the allowable range of <1% error; When there is an error, correct it by increasing or decreasing the speed of the suction fan until the pressure difference between the upper and lower surface of the front edge of the suction port and the flow error are within the allowable range.

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