Burning rate augmentation in solid fuel ramjets by swirling inlet air stream

Proceedings of the Institution of Mechanical Engineers, Part G:

2022

Due to the complexities of the turbulent reacting flows in the combustion chamber of the turbo-engines, despite significant advances in the computational fluid dynamics, the experimental investigations are still very useful in design and optimization processes. On the other hand, the operating conditions of the combustion chambers are such that they have high inlet pressures and temperatures, so providing these conditions for the considered air flow in the combustion chamber is very complex and expensive. Therefore, the development of low pressure test stands has been considered for decades, and the atmospheric tests are utilized in many research centers and industries related to the turbo-engines. In the present study, using numerical simulations, the effect of pressure on the flame shape and pollutants is investigated and the validity of the results of atmospheric tests is analyzed. Here, an in-house developed program is used to solve the governing equations using the finite volume method. The results show that the flame shape significantly varies at low pressures compared to the operating conditions, and the atmospheric test data are not reliable enough.

Section: Governing Equations and Numerical Proceduresmentioning

confidence: 99%

Assessment of the combustion chambers' atmospheric test data

Gheshlaghi

Proceedings of the Institution of Mechanical Engineers, Part G:

2022

“…More details on the governing equations and numerical procedure are presented in Ref. [7][8]. This program has also been validated using some experimental data, and used satisfactorily to study different reacting flow fields which details can also be found in Ref.…”

Section: Governing Equations and Simulation Proceduresmentioning

confidence: 99%

“…Therefore, some ideas have been proposed to augment the fuel regression rate in the combustion chamber of the solid fuel ramjets and increase the engine thrust level to the limit of this propulsion system. It has been illustrated that imposing the inlet flow swirl by using a swirler can increase the solid fuel regression rate [6], and a correlation has been found for its behavior [7]. The other way is an engine spin that can augment the regression rate and improve the performance, which has been analyzed recently in both steady and transient situations [8].…”

Section: Introductionmentioning

confidence: 99%

Using Wavy Fuel Surface to Improve the Performance of the Solid Fuel Ramjets

Reyhani

Propellants Explo Pyrotec

2022

Self Cite

This paper introduces a new idea to augment the fuel regression rate in solid fuel ramjets. The heat transfer rate from the reacting flow field into the surface of the solid fuel grain determines directly its regression rate in this propulsion system, which is very low in comparison with solid rocket motors leads the low thrust levels. This innovative simple practical method is based on the geometrical treatment of the fuel grain, making the smooth ribs as a wavy surface, to increase the turbulence and the heat transfer rate into the evaporating surface where the fuel flow rate is determined. The finite volume solver of the turbulent reacting compressible flow is developed to study the flow field where the burning rate is computed using the conjugate heat transfer for the solid fuel. The influence of the amplitude and the period of the cosine function as the fuel surface geometry are investigated on the regression rate, and it is shown that the amplitude is more effective, and utilizing such surface treatments helps to augment considerably the fuel average regression rate.

“…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%

“…Tahsini 13 performed numerical studies on the effect of the ramjet's spin on the regression rate of the solid fuel and proposed a relation for steady state condition and also illustrated that the transientburning phenomenon may occur at unsteady operation when the rapid spin-accelerations are imposed. In recent years, Musa et al [14][15][16] and Tahsini 17 conducted some experimental and numerical studies on the enhancement of the regression rate by inlet swirl for performance improvement of the SFRJs.…”

Section: Introductionmentioning

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.