The role of acoustic Reynolds numbers on studying of heat transfer in solid propellant rocket motor

Abstract

Oscillating flows occur in many engineering applications. Engineering systems that exhibit undesirable flow oscillation include solid propellant rocket motors (SPRM) that may exhibit acoustic oscillations effecting the burning rate of the propellant. Acoustic erosion occurs when the scrubbing action of the acoustic wave increases the mean burning rate of the propellant. It has been postulated that this increased burning rate is due to the transition to turbulence and the resulting increased heat transfer to the propellant surface. In this investigation the use of naphthalene sublimation technique made it posible to study the simulation of the flow near a burning propellant in a SPRM in turbulent case at different axial locations in a duct containing an oscillatory flow for determination of heat tranfer at high acoustic Reynolds number has been investigated using the mass - heat transfer analogy. In this study, the combustion process is separated from fluid dynamic aspect of the problem. The acoustic Reynolds number was varied over a range from well below the values where acoustically generated turbulence is expected to occur to values above the anticipated transition value. The mass transfer (or heat transfer) rate increasing with Reynolds number, as would be expected with a turbulent flow, is observed, but beginning at Reynolds numbers an order of magnitude below the expected turbulent transition values and continuing with the same form to values well above the transition Reynolds number. The work involved the design, and construction of the simulation facility and all necessary measurements.