Measuring and testing – Wind tunnel: aerodynamic wing and propeller study
Reexamination Certificate
2001-06-20
2003-06-03
Williams, Hezron (Department: 2855)
Measuring and testing
Wind tunnel: aerodynamic wing and propeller study
Reexamination Certificate
active
06571618
ABSTRACT:
BACKGROUND
1. Technical field
The invention relates to a device designed to support a flying instrument such as a prototype or a missile model in a wind tunnel, so as to study the behavior of this instrument under different attitudes, with its motor on.
The invention applies to wind tunnel tests carried out on any type of motorized flying instrument and particularly a prototype or a scale one model, fitted with a motor, of a missile of which it is desired to study the behavior in real time in a supersonic tunnel, hands off, by reconstructing the changes in dynamics representative of the flight attitudes of the instrument.
2. Prior art
As shown in documents FR-A-2 159 548 and FR-A2 641 378, there is a known technique of wind tunnel testing the aerodynamic behavior of a model of a flying instrument such as an aeroplane by mounting this model on a boom connected to the fixed structure of the wind tunnel by a set of mechanisms allowing the attitude of the model being tested to be varied in real time. When this technique is used, the rear end of the model is connected to the front end of the boom and the latter extends backwards approximately in the extension of the model.
Support devices of this type make it possible to study, hands off, the aerodynamic behavior of the flying instrument surfaces which are in contact with the ambient air, when the attitude of the instrument changes in time.
On the other hand, such support devices cannot be used to study the behavior of a flying instrument whose motor or motors are switched on. Indeed, the presence of a boom approximately in the extension of the model, to its rear, does not allow a motor located in the longitudinal axis of the instrument to be switched on and greatly disturbs the airflow leaving a motor offset relative to this axis.
At the present time, when flying instruments are wind tunnel tested with their motors on, support devices of a different design are used. These support devices include several articulated supports connecting the instrument to the fixed structure of the wind tunnel. The articulated supports are presented usually in the form of arms or pylons at least one of which comprises length adjustment means. Most often, three or four articulated supports are used.
In such a support device, the articulated supports are offset towards the rear relative to the front part of the instrument, so as not to disturb the airflow in this zone. Moreover, to allow the behavior of the instrument to be studied while the motor is on, the articulated supports are also located clearly outside the airflow zones located upstream and downstream of the motor.
When such a support device is used to study the behavior of an instrument the motor of which is on, operators adjust the required configuration and flight attitude (sideslip value, incidence angle, etc.) by acting on the length adjustment means, before proceeding to a test. When another configuration and another flight attitude are to be tested, it is necessary to stop the instrument motor and to intervene again manually on the length adjustment means before proceeding to a new test.
This conventional technology is particularly long and tedious to implement. Moreover, it does not allow the dynamic behavior, in real time, of an instrument with its motor on to be studied. In particular, existing support devices are ineffectual for studying the behavior of an instrument with its motor on when it describes a pre-set trajectory or trajectory fraction.
BRIEF SUMMARY
The exact object of the invention is a support device designed to allow the study of the behavior of a motorized flying instrument in a wind tunnel when the instrument motor is on, by enabling a modification in real time of the attitude of the instrument for the articular purpose of simulating a trajectory or rajectory fraction followed by the latter.
In accordance with the invention, this result is obtained by means of a device able to support a motorized flying instrument in a wind tunnel, so as to study the behavior of said instrument, with its motor on, under different attitudes, said device including several articulated supports able to connect the instrument to a fixed structure of the wind tunnel, at places offset relative to airflow zones located around a front part of the instrument and upstream and downstream of the motor, at least one of said supports comprising length adjustment means, the device being characterised in that the length adjustment means are connected to remote control means able to modify in real time the instrument attitude.
Since the length adjustment means are remote controlled, the instrument attitude may be modified in real time, hands off. It thus becomes possible, particularly, to study the behavior of a flying instrument with its motor on, by simulating a trajectory or trajectory fraction followed by this instrument.
In a preferred embodiment of the invention, the supports include a front support, of invariable length, incorporating articulation means to at least two degrees of freedom of rotation around two axes oriented along two directions orthogonal to each other and to a longitudinal axis of the instrument, and two rear supports each incorporating length adjustment means and pivot connections.
To advantage, the front support is oriented approximately radially relative to the longitudinal axis of the instrument and arranged in a vertical plane passing through this axis. The rear supports are then oriented radially relative to the longitudinal axis of the instrument and arranged symmetrically relative to the aforementioned vertical plane, when the two rear supports are in an initial state corresponding in particular to a zero sideslip value and to a zero incidence angle.
In this same initial state, the rear supports preferably form with the vertical plane an angle such that the mounting of the instrument on the device is isostatic. This angle is for example approximately equal to 45°.
In the preferred embodiment of the invention, the rear supports are offset towards the rear by about one meter relative to the front support, along the longitudinal axis of the instrument.
Furthermore, the length adjustment means are constituted preferably by hydraulic jacks servo-controlled lengthwise.
To reduce as far as possible the airflow disturbance induced by the front and rear supports, each of these supports is generally placed inside a streamlined casing. This casing also provides thermal protection for the supports and contributes to their mechanical strength.
To provide control in real time of the configuration and flight attitudes of the instrument, angular measurement means such as resolvers are to advantage associated with the articulation means.
To take account of the significant increases in temperature which occur in the wind tunnel, in the vicinity of the instrument (about 350° C.), cooling means are additionally provided to cool the pivot connections and the angular measurement means located in the immediate vicinity of the instrument.
REFERENCES:
patent: 4920791 (1990-05-01), Griffin
patent: 5370349 (1994-12-01), Bousquet et al.
patent: 5866813 (1999-02-01), Nakaya et al.
patent: 11 72 875 (1964-06-01), None
patent: 2159548 (1971-11-01), None
patent: 2641378 (1988-12-01), None
Carton Laurent
Demay Jean-Paul
Aeropatiale Matra Missiles
Krebs Robert E.
Thelen Reid & Priest LLP
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