Visualization and Emission Spectra of Flames in Combustion Chamber of Swirling-Oxidizer-Flow-Type Hybrid Rocket Engines

Abstract

In order to clarify flame behavior in the combustion chamber of swirling-oxidizer-flow-type hybrid rocket engines, a small hybrid rocket engine with a large quartz glass window was fabricated to observe the inside of the combustion chamber from the front directly. PP and PMMA fuel grains were burned under the swirling and non-swirling oxygen flow conditions. For both PP and PMMA combustion, the disturbed swirling flames were found to develop closer to the grain surface than those without swirl, resulting in an increase of the fuel regression rates. The swirling flames consisted of not a single large flame but an annular aggregate of small striated flames on the grain surface. Emission spectra of counter-diffusion flames over the PP and PMMA rods showed that the strong continuum due to hot carbon particles in the flames, and the weak C 2 and CH emissions were also visible. The filtered photographs which took the continuum and C 2 emissions in the hybrid rocket combustion chamber suggested that the gas-phase reactions of PMMA with oxygen substantially occurred not in the center region of the combustion chamber, but near the PMMA gain surface. For PP combustion, the gas-phase reactions with oxygen may also occur in some degree near the central region.

Visualization of Flames in Combustion Chamber of Hybrid Rocket Engine with Multi-Section Swirl Injection Method

“…The flame confirmed by the experiment that Professor Yuasa and others used PP and PMMA for was not observed. [7] Also the gaseous material observed in combustion chamber was similar to filament-like structures which were reported by Ashley A. Chandler in Stanford University. [8] Figure8 shows the pictures of digital single-lens reflex camera.…”

“…These methods were established by Prof. Yuasa at Tokyo Metropolitan University. [7] This mechanism enables to observe flame directly. Figures 3 shows the schematic diagram of each fuel grain shape.…”

“…[7] We carried out new experiments by taking reference to their technique of visualization. Figures 2. shows the schematic diagram of combustion chamber.…”

Performance analysis of injectors for a hybrid propulsion system

“…In [6], the relationship between regression rate and maximum specific impulse was studied. According to the authors, since the regression rates are lower in hybrid propulsion, it is much more difficult to achieve the maximum theoretical specific impulse in the richest region of the fuel surface.…”

Solid-Fuel Regression Rate for Standard-Flow Hybrid Rocket Motors

“…Here we have treated precisely those effects that were neglected in the previous studies. From many experimental results, Yuasa et al suggested that diffusion-limited combustion is dominant in the gas-phase reactions of polymethylmethacrylate (PMMA) with gaseous oxygen (GOX) in laboratory-scale hybrid rocket engines (6) . In this case, the mass flux exponent is slightly less than 0.8 (7)(8)(9) .…”