A 1D Multi-Tube Code for the Shockless Explosion Combustion

Abstract

Shockless explosion combustion (SEC) has been suggested by Bobusch et al., CST, 186, 2014, as a new approach towards approximate constant volume combustion for gas turbine applications. The SEC process relies on nearly homogeneous autoignition in a premixed fuel-oxidizer charge and acoustic resonances for cyclic recharge. Operation of a single SEC tube has proven to be rather robust in numerical simulations, provided the flow control assures nearly homogeneous autoignition. Configurations with multiple tubes that fire into a common collector plenum preceding the turbine will be needed, however, to avoid excessive fluctuating thermal and mechanical load on the turbine blades. In such a configuration, the resonating tubes will interact with the volume of the plenum, and proper control of these interactions will be an important part of the engine design process. The present work presents an efficient, rough design tool that simulates the firing of such multi-tube SEC configurations into a torus-shaped turbine plenum. Both the tubes and the plenum are represented by computational quasi-one-dimensional gasdynamics modules implemented in a finite volume code for the reactive Euler equations. Suitable tube-to-plenum coupling conditions based on mass, energy, and plenumaxial momentum conservation represent the gasdynamic interactions of all engine components. First investigations utilising this tool reveal considerable dependence of the SEC-tubes' operating conditions on the tube radius and length, and on the tubes' positioning along the plenum torus. The SEC is especially sensitive to the plenum's radius. Misfiring of one of the tubes does essentially not affect the operation of the others and does not even necessarily lead to a shutdown of the disturbed SEC tube.