High enthalpy hypersonic wind tunnel for propulsion physics research
Abstract
Advanced hypersonic propulsion systems such as scramjets will be key components of high-speed transportation for both military and civilian applications in the future. The combustion process in scramjets typically involves highly turbulent reactive flow conditions, often beyond the limits of our physicochemical understanding. The work proposed here is to enable transformative advancement in our knowledge of the interaction between combustion and shock wave dynamics relevant to next generation hypersonic scramjets operating at speeds exceeding Mach 7. The United States Air Force devotes significant effort in fundamental research in hypersonic propulsion systems at the Mach 5 range as evidenced by the X-51 scramjet. This study will provide a foundational scientific knowledgebase in furthering these efforts to a new generation of propulsion systems at higher velocity ranges where the physics can be dramatically different. Development of next generation high speed propulsion systems is fraught with a vast range of technical challenges. The scramjet for example, which offers the benefits of a simple design, reduced weight, high specific impulse, and high speed operation, also faces significant technical challenges in flow control and combustion stability due to the supersonic airflow through the entire engine and resulting high Reynolds number regimes (1, 2). To achieve maximum efficiency in hypersonic flight, gas entering the combustion chamber must mix with the fuel and react before the burned gas is expanded through the nozzle. This should occur with minimal pressure loss, leading to minimal irreversibility in the propulsion cycle. In realistic flight conditions, the temperature and pressure ranges which allow efficient fuel-air mixing and stable combustion to occur can be limited and careful design of the flowpath is required so that optimal thrust can be generated. During the ram to scram transition phase, unmitigated instabilities can occur in the combustion due to the mutual coupling between the unsteady heat release and local flow fluctuations in the flame zone (3). In this phase, the combustion dynamics can induce unpredicted thermal choking which can degenerate into unstart , a process where severe flow obstruction in the combustor due to excessive thermal dissipation and severe flow fluctuations ultimately lead to the loss of thrust.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 06, 2025
- Source ID
- FA95502410114
Entities
People
- Tonghun Lee
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of Illinois Urbana–Champaign