Numerical analysis of supersonic combustion of hydrogen flow characteristics in scramjet combustor toward the improvement of combustion efficiency

Abstract

A modification in the ramjet engine, known as the Supersonic Ramjet Combustion, completes the combustion at supersonic speeds. Inside the combustion chamber, the mixing of fuels and the entire combustion procedure completes in milliseconds. So, the combustion chamber's flow physics is highly complicated. Through this study, the target is to improve the combustion efficiency inside the combustion chamber, thereby improving the performance of the scramjet engine. For this study, the performance of a strut-based flame stabilizer was analyzed in various positions, and the impact on energy efficiency and combustion performance is evaluated. SST k-ω model of turbulence is used to work out the Navier-stokes equation. To validate data from the experiment, a single strut configuration was considered for the next step, i.e., the comparison of the available data with a three-strut configuration. While considering the three-strut layout, in the x and y directions, secondary struts are placed, while the position of the primary strut remains constant. Only the flow from the primary strut is considered for the analysis of combustion performance out of three struts. From the obtained results, it is clear that the significant factor in improving energy efficiency is positioning the secondary strut in the present three-strut layout. The experiment results state that the combustion efficiency is boosted by 33.86% compared to a single strut combustor. It was also found that there was a considerable decrease in the level of unburned fuel, which makes the configuration more economical. The placement of struts plays a vital role, as any fault in the configuration makes it less efficient than a single strut layout. Other elements that boost combustion efficiency are expansion fans and shock reflection inside the primary zone of combustion and the secondary strut region. With the inclusion of secondary struts, the static wall pressure also escalated. A discrete flow was also observed on the combustion walls for some particular strut layouts. An increase in combustion efficiency was seen when both primary and secondary struts were placed near each other and also for reacting flow from the primary strut alone. There arises no need to supply fuel to secondary struts. So, overall fuel efficiency is improved, making the whole system energy-efficient.