JPS6318236A - Air flow measuring instrument for vehicle - Google Patents

Abstract

PURPOSE:To enable air flows in three-dimensional directions to be arbitrarily and accurately measured in positions behind a vehicle by constituting pressure measuring means by spherical probes wherein a plurality of pressure sensors are provided in three-dimensional directions. CONSTITUTION:Pressure measuring means 5 is constituted such that a plurality of spherical probes 7, 7... are pivotally supported in parallel in a vertical direction by a prescribed support member 6 longer than the height of a vehicle 1 in the vertical direction. A plurality of pressure sensors are buried in each of the probes 7, 7.... The output pipes 10, 10... of the pressure sensors communicate with a scanning valve 11 through the pivotally supporting portions of the probes 7, 7... and the member 6. A pressure measuring instrument 13 sequentially conducts the multi-point measurement of pressure values via the valve 11. Obtained data are recorded in a prescribed memory booth 12. Further, the means 5 can arbitrarily move back and forth or right and left with respect to the vehicle by a traverse device 20 as a moving device. Thus, air flows in three-dimensional directions over the whole region behind the vehicle can be arbitrary and accurately measured.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a vehicle airflow measuring device.

(Prior Art) Conventionally, the measurement of air flow on the surface of a vehicle, particularly an automobile, has been carried out by scanning a vehicle (sample bundle) to be measured, as shown in Japanese Patent Application Laid-Open No. 58-48830, for example. This is done by installing a palm dynamometer in a wind tunnel test room and blowing cooling air through a fan duct from either side of the front of the vehicle. 1986-4
Smoke is used as shown in Publication No. 2939.

(Problem to be Solved by the Invention) However, although the above-mentioned conventional technology is effective in measuring the airflow on the surface of the car body where the airflow flows in a stratified state, Judging from the shape of the car body, negative pressure tends to occur when driving, and in areas where the airflow is rolled up from below to above, the air streamlines shown by the smoke are disturbed in three dimensions due to complex changes in the flow direction. Therefore, there is a problem that it becomes impossible to measure the air flow substantially accurately.

In particular, in view of the above circumstances, measurement of the airflow direction in a three-dimensional direction is indispensable for accurate measurement of changes in airflow in the area, but the above-mentioned conventional technology does not adopt a three-dimensional observation method itself. I can't deal with this because I can't.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above problems. In the air flow measuring device, the pressure measuring means is composed of a spherical probe having a plurality of pressure sensors installed in three-dimensional directions, and is configured to be movable in any direction by a predetermined moving device.

(Function) According to the above means, the pressure measuring means for measuring the air flow of the vehicle is constituted by a spherical probe in which a plurality of pressure sensors are installed in three-dimensional directions, and is movable arbitrarily by the moving means. Therefore, it is possible to arbitrarily and accurately measure the airflow in three-dimensional directions at each position at the rear of the vehicle.

(Embodiment) FIGS. 1 to 3 show a vehicle airflow measuring device according to an embodiment of the present invention.

First, in FIG. 1, reference numeral I is a hatchback type vehicle (automobile), for example, which has been delivered and installed in the wind tunnel test room A, and in front of the vehicle I in the wind tunnel test room A is a fan duct 2 for blowing air. is installed. From this fan duct 2, a predetermined air flow is blown toward the vehicle 1 at an arbitrary flow velocity.

On the other hand, the reference numeral 5 denotes a pressure measuring means located at the rear of the vehicle 1 in the wind tunnel test room A and movable in the longitudinal and lateral directions of the vehicle 1.

The pressure measuring means 5 includes a plurality of spherical probes 7.7 supported vertically in parallel on a predetermined support member 6 which is longer than the vehicle height of the vehicle 1 in the vertical direction.・
As shown in FIG. 2, a plurality of pressure sensors 9 made of, for example, Pitot tubes are installed over the entire spherical part in a radial direction from the center of the spherical body and located at the intersection of the meridian and latitude of the spherical surface. 9... is buried. The output pipes 10, 10, . . . of the pressure sensors 9, 9, . A pressure measuring device 13 such as a manometer, etc.
The pressure values are sequentially measured at multiple points and the measured data are recorded in a predetermined memory booth 12 at multiple points. In addition to the data recording function, the memory booth 12 also has a drive control function for a traverse device 20, which will be described later, and a scanning control function for the scanning valve 11. For example, a floppy disk is used to record the measurement data, and the flow field based on the measurement data includes (a) distribution diagram of flow velocity vectors, (b) isototal pressure diagram, (c)
) Isostatic pressure diagrams etc. are formed and recorded.

These recorded data are finally input to a personal computer 16 equipped with a graphic display function, and the image display (animation display) that simulates the actual vehicle driving mode is used to display airflow conditions (airflow winding up, negative pressure distribution, etc.). will be analyzed and considered three-dimensionally.

The pressure measuring means 5 can be moved arbitrarily in the longitudinal or lateral direction of the vehicle by a traverse device 20 as a moving device, and is capable of measuring the three-dimensional direction of the air flow over the entire area at the rear of the vehicle. It is possible to measure airflow. The traverse device 20 includes two traverse devices provided corresponding to the longitudinal and lateral directions of movement of the vehicle l.
The support member 6 of the pressure measuring means 5 is supported movably in the direction of each rack by a set of racks 17.17 and pinions 18.18. By arbitrarily driving the pressure measuring means 5 to rotate by a motor (not shown), the pressure measuring means 5 is controlled to move in the backward direction or in the left-right direction of the vehicle 1. The pulse motor is driven by a control command from the memory booth 12 according to the measurement program as described above.

Next, a method for measuring airflow in a vehicle using the above airflow measuring device will be explained with reference to the flowchart shown in FIG.

First, the above-mentioned spherical probe 7.7...In order to estimate the magnitude S of the surface pressure bead and the vertical position θ○, ψ0 of the peak, the pressure sensor 9.9 which gives the maximum value imax of the 11 values of the surface pressure meter is used.
...The surface pressure distribution in the vicinity is approximated by a polynomial of θ and ψ (step S). Since the shape of the probes 7.7... is spherical, the pressure distribution is determined at the peak position θ0. It is considered that the distribution is axially symmetric with respect to ψ0. Therefore, a functional expression representing the pressure distribution is set as follows. t, θ, and ψ are the general bead angles for the airflow represented by the probe base Q coordinates in FIG.

Cp= Cpt -a((θ-θ0)2÷(ψ-ψo)
2)=Cr)*C+'F3'θ+C++p'ψC2(02+ψ2)・・・・・・・・・(+) 7, Cp is the pressure coefficient, Cpt is the total pressure (dynamic - static) ) coefficient (peak value of pressure coefficient cp), a, Co
.

C, e, Cut, C2; Yo, spherical probe 7.7”
A constant determined by the position of θ0. ψ0 is the value of θ and ψ that give a peak, and has the following relationship.

Therefore, by approximating the pressure distribution as in the above equation (+) and using the pressure detection data near the pressure casenosa that gives the maximum value of the measured value, the above constant \lCo is determined.

Once CIe, C+w, and Ct are determined, the peak of the surface pressure, that is, the total pressure, and the position giving the peak, from equation (2),
That is, the flow direction (θO1ψO) can be estimated (step S).

Next, in the coordinate system (probe reference coordinates) whose origin is the peak position (θ0.ψ0) of the pressure determined as described above, the peak value imax of the pressure and the points adjacent to it both vertically and horizontally (the peak point) are added. 5 points) are coordinate transformed and expressed in local flow reference coordinates (step S). This is done in order to obtain a three-dimensional flow velocity vector for the local flow to the peak point.

That is, for example, as shown in FIG. 4, first, each axis Xp of the reference coordinates of the spherical probes 7.7.

It is assumed that Yp and Zp are defined.

On the other hand, X, Y, and Z indicate the spatial coordinates of the position of the spherical probe 7.7 in the rear flow field of the airflow given to the vehicle.
The position of is defined relative to this coordinate system. As above, <Xp, Yp, and Zp are probe reference coordinates, and the zp axis is parallel to the It is. The above θ.

ψ is defined based on the X p, Y p, and Z p coordinate axes. The center axis of Ze is the local flow reference coordinate.

Since the local flow around the spherical probes 7.7 is expected to be axially symmetrical about the Zey axis, it is expected that the pressure distribution will also be symmetrical about the Z~ axis.

In other words, the surface pressure distribution of the spherical probe 7.7...
Spherical probe 7.7... Considering the coordinate system with the stagnation point P on the surface as the origin, the pressure distribution at a certain point Q is: Yo, Ze, the angle φ between the sleeve and the line segment 0Q (O is the center of the spherical probe) It can be expressed as a function of only.

Therefore, by rotating the X p, Y p, and Z p axes, Ze1. Create an r; coordinate system so that the axis and the zp axis overlap, and set it to Xp.

The coordinate system of the probe surface pressure sensor defined by the Yp, ZpM system is expressed in a new coordinate system, and the angle φ between the coordinates of each pressure sensor and the sleeve is determined. The coordinate transformation by rotation at this time is the transformation matrix (Ae) that rotates by 00 around the zp axis, and the rotation by (Ae) that moves the yp axis to create an axis Yp'. This is performed by A9), a conversion process that rotates the images by ψ, ==π/2 - ψ0 so that they overlap.

That is, 1 kodashi (X pi, Y pi, Z pi) is
These are the coordinates of the i-th pressure sensor. At this time, φ can be obtained as follows.

φ 1=cos−'Ze+i
・ ・ ・ ・ (4) By such coordinate transformation, φ of the pressure sensor near the peak value is determined. Assume that the pressure distribution with respect to the second φ is determined by the following experimental formula, for example, from a preliminary experiment conducted in advance.

Cp(φ) = Cpj −K (1φ2 to sin'φ+
+ to 2φ4' to 3φ6shi... ・ ・ ・) ・ ・
・(5) Here, kl, 2. 3. ...ha, yo(,
This is a constant determined from four experiments. When φ=φi, K is determined by setting Cp=Cpi so that the pressure coefficient of the first pressure sensor and φ satisfy equation (5). Alternatively, ignoring the pressure coefficient cpt obtained from equation (2),
It is possible to obtain K and Cpt simultaneously from equation (4) (step S4).

Once the equation Cp=Cp(φ) has been completely determined in this way, the angle φ=φS that gives static pressure is substituted into equation (4) to find the static pressure Cps=Cp(φS). . However, φS
It is assumed that has been determined through preliminary experiments (step S5).

Then, when the static pressure Cps is found, the local dynamic pressure ratio at that time can be expressed as (Cpt - Cps), so the local flow velocity V is V - (V / V engineering)' = A5 [cloud i ・...(6) can be calculated (step S6). In addition, ■o
represents the mainstream velocity of the non-dimensional local flow.As a result, the direction and magnitude of the '13 flow can be found using equations (2) and (6) above. Therefore, if we decompose this into the X, Y, and Z components of the spatial coordinate system of the flow field and rewrite it, the velocity vector in the three-dimensional direction centered on the local flow will be:
The result is as follows (step S).

Moreover, this is the above-mentioned mainstream speed V. can be expressed as follows.

Therefore, in the case of this embodiment, as is clear from the above calculation process, the total pressure of the local flow in the flow field centered on the pressure peak position of each of the plurality of spherical probes 7,7,...
Static pressure, flow direction, and flow velocity vector (velocity) can each be relatively easily measured as data in three-dimensional directions. As a result, by simulating the actual running conditions from various three-dimensional angles using the personal computer 16 having the graphic display function described above based on each of these data, it is possible to analyze the complicated airflow conditions at the rear of the vehicle very easily. You will be able to do this.

(Effects of the Invention) As explained above, the present invention provides a vehicle airflow measuring device that uses a pressure measuring means to measure the airflow generated at the rear of the vehicle when the vehicle is running, wherein the pressure measuring means comprises: It is characterized by being composed of a spherical probe in which a plurality of pressure sensors are installed in three-dimensional directions, and is configured to be movable in any direction by a predetermined t3 motion device.

Therefore, according to the present invention, the pressure measuring means for measuring the airflow of a vehicle is constituted by a bulb-shaped probe having a plurality of pressure sensors arranged in a three-dimensional direction, and is movable by means of a moving means. Therefore, it is possible to easily and accurately measure the air flow in three dimensions at each position at the rear of the vehicle.

[Brief explanation of the drawing]

FIG. 1 is a side view of a vehicle air flow a++ constant device according to an embodiment of the present invention, FIG. 2 is an enlarged perspective view of the main part of the pressure measuring means in the device, and FIG. FIG. 4 is a flowchart showing an outline of the method for measuring the airflow of the vehicle used, and is a spatial coordinate diagram of the airflow field for explaining the measurement method. I... Vehicle 2... Fan duct 5... Pressure measuring means 6... Support member 7... Spherical probe 9... Pressure sensor II. ... Scanning valve I2 ... Memory booth 13 ... Pressure measuring instrument 16 ... Personal computer 20 ... Traverse device

Claims (1)

[Claims] 1. A vehicle air flow measuring device that measures the air flow generated in the rear part of a vehicle when the vehicle is running, using a pressure measuring means, the pressure measuring means comprising a plurality of pressure sensors.
1. An air flow measuring device for a vehicle, comprising a spherical probe installed in a dimensional direction and configured to be movable in any direction by a predetermined moving device.