Critical Review of the Methods to Measure the Condensed Systems Transient Regression Rate

Abstract

Accurate knowledge of steady state and transient burning rate of solid fuels and energetic materials is very important for evaluating the performance of different propulsion and/or gas generator systems. The practical demands imply accuracy of available burning rate data on the level of 1% or better and proper temporal resolution. Unfortunately, existing theoretical models do not allow predicting the magnitude of the burning (regression) rate with needed accuracy. Therefore, numerous burning rate measurement methods have been developed by various research groups over the world in the past decades. This paper presents a critical review of existing techniques, including basic physical principles utilized for burning rate determination, an estimate of the temporal and spatial resolutions of the methods as well as their specific merits and limitations. There are known the methods for measuring linear regression rate via high speed cinematography, X-ray radiography and ultrasonic wave reflection technique. Actually, none of those methods could satisfy the practical demands. As an alternative is the microwave reflection method, which potentially possesses high spatial and temporal resolutions and may solve the measurement problem. In addition, there exist methods for measuring transient mass or weight of the burning material. They are based on recording the frequency of oscillations of elastic element with attached specimen or a cantilevered rod with a strain gauge pasted to the base. Practically, these methods could not provide needed accuracy. Much better parameters can be obtained when using the recoil force or microwave resonator techniques. Recommendations for special applications of certain methods are formulated.