[en] The plasma-based technique was studied for ignition and flameholding in a supersonic airflow in different laboratories for a long time. It was shown that flameholding of gaseous and liquid hydrocarbon fuel is feasible by means of surface DC discharge without employing mechanical flameholders in a supersonic combustion chamber. However, a high power consumption may limit application of this method in a real apparatus. This experimental and computational work explores a distributed plasma system, which allows reducing the total energy consumption and extending the life cycle of the electrode system. Due to the circuit flexibility, this approach may be potentially enriched with feedbacks for design of a close loop control system. (paper)

[en] This paper presents the results of experimental study of plasma-based actuator for mixing of the fuel with air in a supersonic flow. The long unsteady plasma filament of Q-DC electrical discharge is located along the fuel jet from a wall-arranged supersonic injector with a wall-normal direction of injection. The location of plasma filament over the fuel jet was controlled by using the nozzle of injector as one of discharge electrodes. Three different gases were tested for simulation of fuel injection: air, CO₂ and C₂H₄. It was found that the discharge position in respect of the fuel jet significantly depends on the injected gas. The activation of discharge within all injected gases results in development of fluid instability at fuel-air interface which leads to the mixing enhancement. (paper)

[en] The paper describes experimental research of the surface electrical discharge influence on the ignition and combustion of the gaseous and liquid hydrocarbon fuel in supersonic airflow without mechanical flameholders. Electrodes of plasma generator are integrated with injectors of gaseous fuel. Tests were carried out on the experimental setup T131B in TsAGI. Diagnostics includes schlieren visualization, measurements of pressure distribution and discharge voltage/current. It is shown that new scheme of plasma generation and pilot fuel injection is rather effective and provides ignition of liquid hydrocarbon fuel in hot supersonic airflow (T ₀=750 K) and ethylene ignition in cold (T ₀=300 K) supersonic airflow. (paper)

[en] We report a procedure for temperature and water vapour concentration measurements in an unsteady-state combustion zone using diode laser absorption spectroscopy. The procedure involves measurements of the absorption spectrum of water molecules around 1.39 μm. It has been used to determine hydrogen combustion parameters in M = 2 gas flows in the test section of a supersonic wind tunnel. The relatively high intensities of the absorption lines used have enabled direct absorption measurements. We describe a differential technique for measurements of transient absorption spectra, the procedure we used for primary data processing and approaches for determining the gas temperature and H₂O concentration in the probed zone. The measured absorption spectra are fitted with spectra simulated using parameters from spectroscopic databases. The combustion-time-averaged (∼50 ms) gas temperature and water vapour partial pressure in the hot wake region are determined to be 1050 K and 21 Torr, respectively. The large signal-to-noise ratio in our measurements allowed us to assess the temporal behaviour of these parameters. The accuracy in our temperature measurements in the probed zone is ∼40 K. (laser applications and other topics in quantum electronics)

[en] An absorption spectrometer based on diode lasers is developed for measuring two-dimension maps of temperature and water vapour concentration distributions in the combustion zones of two mixing supersonic flows of fuel and oxidiser in the single run regime. The method of measuring parameters of hot combustion zones is based on detection of transient spectra of water vapour absorption. The design of the spectrometer considerably reduces the influence of water vapour absorption along the path of a sensing laser beam outside the burning chamber. The optical scheme is developed, capable of matching measurement results in different runs of mixture burning. A new algorithm is suggested for obtaining information about the mixture temperature by constructing the correlation functions of the experimental spectrum with those simulated from databases. A two-dimensional map of temperature distribution in a test chamber is obtained for the first time under the conditions of plasma-induced combusion of the ethylene – air mixture. (laser applications and other topics in quantum electronics)