Title: Study of the intensive combustion in the scramjet engine
Abstract: The intensive combustion was observed in the subscale scramjet engine combustion tests, and the engine in the mode produced the large thrust. The mechanism should be made clear to apply the intensive combustion mode to the practical engine. The following mechanism was proposed in the present paper. The normally injected fuel interacted with the boundary layer behind the backward-facing step. There appeared the re-circulation region between the step and the fuel jet. The re-circulation region also appeared behind the fuel jet. This region affected the combustion condition greatly. The mixing and the combustion occurred not only in the supersonic primary flow, but also in the re-circulation region. It caused the heat release near the fuel injector, and the high combustion efficiency. Introduction The scramjet, one of the engines that will be used in the aerospace plane, is being studied at the National Aerospace Laboratory (NAL), Japan, and the sub-scale scramjet engine models have been tested in the Ramjet Engine Test Facility (RJTF). In the tests, several inflow air conditions, several engine configurations, and several fuel injection conditions were investigated. In other tests, the effects of radicals and water vapor were discussed.' In the experiments of the sub-scale scramjet engine model, there were two combustion modes, i.e., (1) the intensive combustion mode and (2) the weak combustion mode.' When the fuel flow rate was small, there was the weak combustion mode, and thrust was not produced. As the fuel flow rate was increased, the engine jumped into the intensive combustion mode. Then the thrust was large, and the net thrust was positive in several cases. The intensive combustion should be utilized in the scramjet engines. The research engine model used in the RJTF is different from the practical engine to be used in the aerospace plane. Therefore, the features and the mechanism of the intensive combustion must be made clear for its attainment in the practical engine. The mechanism of the intensive combustion was under discussion and it has not been made clear yet. In this paper, my opinion on the intensive combustion was presented. In the RJTF tests, the inflow air conditions correspond to the flight Mach numbers of 4, 6, and 8. There are many experimental results in the Mach 4 and 6 test conditions. The present discussion was based on the results of the Mach 4 and 6 test conditions. Experimental Apparatus and Methods A. Test facility The test conditions in the RJTF are shown in Table 1. They correspond to the flight conditions of Mach 4 and Mach 6 with a flight dynamic pressure of 65 kPa. Compressed air was heated by a ceramic storage heater. The supersonic nozzle had exit dimensions of 5 1 cm by 5 1 cm. In the Mach 4 test condition, the boundary layer thickness was 35 mm at the engine entrance. In the Mach 6 test condition, it
Publication Year: 1998
Publication Date: 1998-07-13
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 3
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