Inlet air and fuel flow pressure fluctuation effect on supersonic combustion

2023

AEAT

Self Cite

Purpose The purpose of this study is to investigate the combustion of the n-Heptane droplets in the supersonic combustor with a cavity-based fuel injection configuration. The focus is on the impacts of the droplet size on combustion efficiency. Design/methodology/approach The finite volume solver is developed to simulate the two-phase reacting turbulent compressible flow using a single step reaction mechanism as finite rate chemistry. Three different fuel injection settings are studied for the considered physical geometry and flow conditions: the gas fuel injection, small droplet liquid fuel injection and big droplet fuel. The fuel is injected as a slot wall jet from the bottom of the cavity. Findings The results show that using the small droplet size, the complete fuel consumption and combustion efficiency can be achieved but using the big droplet sizes, most fuel exit the combustor in the liquid phase and gasified unburned fuel. It is also demonstrated that the cavity's temperature distribution of the liquid fuel case is different from the gas fuel, and two flame branches are observed there due to the droplet evaporation and combustion in the cavity. Originality/value To the best of the authors’ knowledge, this study is performed for the first time on the combustion of the n-Heptane fuel droplets in scramjet configuration, which is promising propulsion system for the future economic flights.

Section: Governing Equations and Numerical Proceduresmentioning

confidence: 99%

Supersonic combustion of n-Heptane droplets with cavity-based fuel injection

Mohamadi

2023

AEAT

Self Cite

“…Different features of the developed numerical program have been validated by diverse benchmark problems and also have been utilized to study various flows in past decade where more details are explained. 12,19,[43][44][45][46][47] Here, three related problems are presented.…”

Section: Governing Equations Numerical Procedure and Validationmentioning

confidence: 99%

Evaporation and combustion of n-heptane droplets in supersonic combustor

Proceedings of the Institution of Mechanical Engineers, Part G:

Nabavi

2021

The purpose of the present study is to investigate the combustion of the n-heptane droplet cloud in the supersonic combustor. The finite volume solver is developed to simulate the two-phase reacting compressible flow using single step reaction mechanism as finite rate chemistry. The focus is on the impacts of droplet size and cloud density on the performance of the scramjet. For the considered physical situation, the upper limit of the droplet size is determined to have higher combustion efficiency, and it is shown that the combustion mode is kinetic-controlled for small sizes and is evaporation-controlled for large droplet sizes. The variation of combustor’s exit total pressure and temperature is also investigated for different droplet cloud densities, demonstrating their apparent opposite behavior that must be considered to get optimum propulsion efficiency. In addition, it is illustrated that thermal choking is another criterion which should be avoided by controlling the fuel mass flow rate for intended flight conditions.

“…20 More details on the equations, numerical algorithm, and validations have been presented in Ref. 11–13, 17–18, and 21–22.…”

Section: Governing Equations and Numerical Proceduresmentioning

confidence: 99%

The response of the solid fuel ramjet combustor to the inflow excitations

Proceedings of the Institution of Mechanical Engineers, Part G:

Nabavi

2021

Self Cite

The response of the solid fuel ramjet to the imposed excitations of the ambient pressure is investigated using full part computation of the system including the intake, combustion chamber, and exhaust nozzle. The finite volume solver of the turbulent reacting compressible flow is used to simulate the flow field, where two grid blocks are considered for discretizing the computational domain. Both impulsive and oscillatory excitations are imposed to predict the response of the solid fuel mass flow rate. The results demonstrate that strong fuel flow overshoot occurs in the case of sudden impulsive excitation which is omitted for gradual impulsive excitations. In addition, the oscillatory excitations eventually lead to regular oscillatory response with frequencies similar to the imposed excitations and decrease the average fuel mass flow rate independent of the excitation frequency. But the amplitude of the response depends on the excitation frequency and amplification occurs in some frequencies. This behavior is not related to the combustion instabilities and is similar to the L-star instability in the solid rocket motors. In the design and analysis of the solid fuel ramjets, the coupling of the flight dynamics and the engine performance must be considered, and this study is the first step of such complete methodology to have more accurate predictions.