Vlasenko V.V.   Voloshchenko O.V.   Sabelnikov V.A.   Talyzin V.A.  

Choice of geometry and operating regimes for experimental dual-mode high-speed propane-fueled combustion chamber

Reporter: Vlasenko V.V.

In 2017, in the framework of the megagrant of the Ministry of Education and Science (Russian Federation), contract No. 14.G39.31.0001 of February 13, 2017, laboratory for physical and numerical simulation of flows with combustion in the engines of promising aircraft is created in TsAGI. An essential element of the work that will be performed by the laboratory in 2017-2019 is validation of the developed physical models and software on the basis of a "hot" aerodynamic experiment, specially performed in T-131 wind tunnel (TsAGI).
For this purpose, an experimental model of a combustion chamber with a supersonic flow at the entrance is designed and will be made in TsAGI. In this model, subsonic or supersonic combustion will be realized, depending on the inflow parameters. Propane will be used as fuel. The experiment will be oriented to the validation of calculations, therefore it will include detailed measurements - both time-averaged static pressure distribution measurements and pressure pulsation registration, wall temperature measurement using thermocouples and thermovision equipment, flowfield visualization (high-speed Schlieren-video shooting, chemiluminescence videoregistration in the near ultraviolet and near infrared ranges). For the visualization, the camera will be equipped by the thick quartz glass optical windows along the whole length.
In the designing the combustion chamber, the experience of studying the model hydrogen-fueled chamber of similar geometry was used, which was considered at the ONERA-Laerte facility in the framework of the European project LAPCAT-II [Vincent-Randonnier, A., Moule, Y., & Ferrier, M. Combustion of hydrogen in hot air flows within LAPCAT-II Dual Mode Ramjet combustor at Onera-LAERTE facility-Experimental and Numerical Investigation. In 19th AIAA International Space Planes and Hypersonic Systems and Technologies Conference, 2014, p. 2932]. These experiments revealed both subsonic combustion behind a pseudoshock and various supersonic combustion regimes, characterized by the interaction of fuel jets injected from the walls with boundary layers on the chamber walls and shock-wave structures in the duct.
The following flow regime is chosen at the chamber entrance: M=2.5, T0=2100 K, p0 = 10 atm. For the choice of the fuel supply scheme, preliminary calculations based on the unsteady Reynolds equations for a multicomponent gas with finite-rate reactions are performed in the 2.5 dimensional approximation. It is shown that there is no self-ignition of propane under the chosen flow regime; and when a pneumothrottle is used, the flameout was obtained after the pneumothrottle stopping. Fuel supply schemes have been found that provide the stabilization of combustion. At oxidizer excess ratio α = 1.5, with addition of 15% H2, a stationary asymmetric flow with subsonic combustion was obtained. The role of the stabilizer is played by the separation upstream from the jet of the upper injector. For α = 3, with the addition of 30% H2, a stationary symmetric flow with supersonic combustion near the chamber walls was obtained.

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