Dynamic calibration of force balances for impulse hypersonic facilities

Abstract

Abstract. This paper analyzes different techniques for the calibration of force balances for use in shortduration impulse hypersonic facilities such as shock tunnels. The background to how deconvolution can be used to infer aerodynamic forces on models in impulse hypersonic wind tunnels is presented along with the theory behind the different calibration techniques. Four calibration techniques are applied to a singlecomponent stress-wave force balance. Experiments in the T4 shock tunnel using the balance demonstrate the suitability of the different calibrations for force measurements in an impulse facility. Cross checks between the calibration techniques are used to check their ranges of validity. It is shown that the impulse response derived from tests in which the model and force balance are suspended from a fine wire and the wire cut agree well with impulse responses derived from calibrations made using an impact hammer. The suitability of the balance for measuring dynamic forces is demonstrated by showing that the drag force on a model follows the history of Pitot pressure in the test section in the tunnel shots.

Application of the Deconvolution Methods for Processing of Measurement Signals in the Fast Processes

“…Equation (6) is called the convolution equation. This equation describes the optical image blur due to subject movement (or recording device) as well as the problem of reconstruction of signals from sensors that have lag time [19]. Solution of integral equations of the first kind of the form (1), (2) refers to the number of illposed problems and requires the development of special regularization methods [8,[30][31][32].…”

“…It should be noted that methods of inverse problems solution for processing signals of the dynamic weight and pressure measurements are used for a long time and more often than in the interpretation of thermocouple signals. For example, in [19,20] the recovery of the temporal aerodynamic characteristics (pressure and forces) by solution of the convolution integral equation (deconvolution method) are described, usually by reducing the problem to a system of linear algebraic equations, or by solution of the problem in Fourier space [21].…”

An experimental investigation of an airframe integrated three-dimensional scramjet engine at a Mach 10 flight condition

“…This section outlines the basic theory of the swfmt for both single and multi-component balances and is based on the introductory sections of Robinson (2003a) and Mee (2003).…”

“…Similarly, the net strain response of the balance is a superposition of the individual strain responses for each point load. The overall calibration procedure involves imparting a series of point loads at different locations on the model using an instrumented impact hammer (Mee, 2003). The measured strain response and hammer signals are used to form a point-load impulse response function (irf) for each calibration hit.…”

“…See also Chan (2012), Kirchhartz et al (2012), and Rowan and Paull (2006). Mee (2002Mee ( , 2003: this report and paper describe the dynamic calibration of a single component balance using an instrumented impact hammer. The results and techniques described in these documents serve as a key foundation for the calibration method presented in this thesis.…”