Numerical investigation on thermo-acoustic effects and flow characteristics in semi-conical Hartmann–Sprenger resonance tube

Abstract

Hartmann–Sprenger tube is a device in which an underexpanded jet enters a closed end tube that is placed in a specific distance from the nozzle. In specific conditions, a standing shock is built in front of the tube, which oscillates based on the tube resonance frequency and creates oscillatory flows with periodic shock motions along the tube. In these conditions, intensive temperature rise could be observed near the tube end wall. Considering these thermal effects, the device could be used as a combustion starter in the space propulsion systems. The present study focuses on flow analysis in various phases of the oscillatory process in a semi-conical PTFE resonance tube by the aim of numerical simulation results. An experimental test is also performed for validation purposes. The T–S diagram is plotted to describe the thermal effects in detail during the oscillatory processes. Various modes of shock contact with flow front are described. In order to follow up the shock traveling process, the diagrams of changes related to major flow properties inside the tube are used. Generation of small turbulences at the moments of combination of compression waves and beginning of flow entrance is also detected. According to the results, traveling of shock waves through the trapped gas was found to be the major mechanism for heat generation inside the tube. The thermal effects are also compared in the conical and cylindrical tubes. The flow analysis will lead to increase in insight for shock motion and heat generation mechanism in a semi-conical Hartmann–Sprenger tube.