Effects of Doplet Diameter on the Performance of Scramjet Engines
- Paper number
IAC-07-C4.5.05
- Author
Mr. RajiniKanth B, Defence Research and Development Laboratory, India
- Coauthor
Dr. Ramanujachari V, Defence Research and Development Laboratory, India
- Year
2007
- Abstract
Scramjet jet engine is one of the most efficient propulsion means for hypersonic air-breathing vehicles. The residence time of the fuel is of the order of 1ms in a typical Scramjet engine. The evaporation time of liquid fuel droplet holds considerable portion of the residence time. Thus engine performance is a strong function of droplet diameter, injection velocity and fuel flow rates. Here a parametric CFD study is carried out on Ramp-cavity based Scramjet engine with kerosene as fuel, to evaluate the engine performance for different droplet diameters. The droplet trajectory calculations are made in lagrangian frame, while the continuous medial is modeled in Eulerian frame. Single step global kinetics for kerosene combustion model and K-ε turbulence model are used. The fuel is distributed in stages along the combustor length. The performance of the engine evaluated based on the parameters like, heat release pattern for each stage of the fuel, (in terms of total temperature and CO2 production), the loss of total pressure, static pressure, static temperature and Mach number along the combustor length. The evaporation history of the droplets (diameter w.r.t time) for the same initial droplet diameter is compared between two different combustor configurations. The comparison showed a strong dependency of the evaporation history on the combustor geometry, as the shock patterns are different for different configurations. Out of two configurations one is considered for further studies with different droplet diameters. The performance evaluation parameters (listed above) are compared. The heat release pattern clearly reflected the change in the droplet diameter. For the smaller droplet diameters the intense heat release creates strong shock and separated regions in the combustor due to thermal choking. Thermal choking may throw the intake of the hypersonic vehicle to un-start conations. Whereas for bigger droplets the heat release is delayed causing poor thrust generation. The wall pressure distribution shows higher static pressure levels and higher total pressure loss for smaller droplet diameters. The higher temperature and pressure fields caused by smaller droplets may cause heat transfer challenges for construction materials. The droplet evaporation times for different stages of fuel are compared for different droplet diameters. Thus optimum thrust without thermal choking for a particular combustor configuration along with material considerations happens for a particular range of droplet diameters. Current paper discusses the results obtained from these simulations in detail.
- Abstract document
- Manuscript document
IAC-07-C4.5.05.pdf (🔒 authorized access only).
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