Time requirements for scramjet performance study with fuel of kerosene

Abstract

Progress and achievement of airbreathing propulsion is seriously constrained by the capability of ground test facility and test time is one of the critical technical issues for the development of its concept and test technique. As we know, airbreathing propulsion test objectives are typically classified into three categories: performance, operability and durability tests. Usually, the performance test time criterion is the time needed to establish steady combustion flow, the operation test time criterion is the time needed to operate moving components of the propulsion system through its operating range, and the durability test time criterion is the time to reach equilibrium temperature along a trajectory or the time of a long cruise. For operability and durability research, blow-down wind tunnel (run duration of tens seconds) and continuous wind tunnel (run duration of more than several minutes) are regularly used. However, for performance research, run duration is still often cited as an impediment to the use of pulse facilities, like shock-tunnels. The generally accepted test time criterion for steady combustion flow establishment is the ratio of the product of test time and flow velocity (often referred to as “slung length”) to the model’s length, and there are a lot of reviews about the time requirement for performance research of model scramjet engine under the condition of laminar or separated turbulent flow[1]. Nevertheless, using shock tunnel, for model engine length of 3.6 m with gas hydrogen fuel, steady combustion flow is fully established within 2ms from flow initiation through the combustor and important sets of data have been successfully obtained for duplicating flight condition of Mach 12 with run duration of 8ms (this represents 8 model flow lengths) [2].