Further Results on Pressure Effects in a Scramjet Engine Combustor Model

Foluso Ladeinde 한국추진공학회 2019 한국추진공학회 학술대회논문집 Vol.2019 No.5

Understanding the roles of pressure in scramjets is the focus of this work. Beside the issue of artificially creating backpressures by using mechanical flaps downstream of the combustor, a non-trivial problem is differentiating backpressure created by mechanical means and thermally-generated backpressure in realistic (reactive) situations. The difficulty stems from the fact that fuel injection contributes to both mechanical and thermal sources of backpressure. To address this problem, backpressures have been generated in the present work by using three different approaches: mechanically by fuel injection without reaction, thermally by fuel injection with reaction, and mechanically by imposing an external pressure at the outlet of the combustor without fuel injection or chemical reaction. Although a few surprising observations are reported, the results suggest that the surrogate approaches have some deficiencies in terms of being able to model the real system.

Supersonic Combustion Modeling and Simulation for Scramjets

Foluso Ladeinde 한국연소학회 2015 KOSCOSYMPOSIUM논문집 Vol.2015 No.12

The State-of-the-Art of Scramjet Simulation

Foluso Ladeinde 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.5

Pressure Effects in a Dual-Mode Scramjet Engine Model

Foluso Ladeinde 한국추진공학회 2018 한국추진공학회 학술대회논문집 Vol.2018 No.12

Deciphering the intriguing roles of pressure in modeled scramjets is the focus of this work in which we investigate three ways of creating backpressure in a simplified model of a dual-mode scramjet (DMSJ) engine. The three approaches are, respectively, from injection pressure, pressurized outlet of the combustor, and thermal choking. Numerous previous studies by others on the dynamic roles of pressure in scramjet have been based on pressurizing the outlet of the engine combustor. Our results show that the dynamics from such a procedure are significantly different from those in the real system where backpressure originates from fuel injection and/or thermal choking.

Numerical Study on the Effect of Equivalence Ratio on Rotating Detonation Engine Flow field

Jacobs Somnic,Foluso Ladeinde 한국추진공학회 2019 한국추진공학회 학술대회논문집 Vol.2019 No.5

Rotating detonation engines (RDEs) have been extensively investigated recently as a candidate for an air-breathing propulsive system with high thermal efficiency, with most of the studies focusing on premixed combustion under stoichiometric conditions. Because a purely stoichiometric condition cannot be ascertained in realistic applications, the knowledge of the effects of equivalence ratio becomes very important. The present study has the objective of investigating the effects of equivalence ratio on premixed combustion in a realistic RDE system. For this purpose, both one-dimensional and two-dimensional spatial models are studied. The effects on the pressure, temperature, and chemical species distributions will be presented. A basic RDE is shown in Fig. 1. The combustion chamber is an annular ring, where the direction of flow is from the head end (bottom in figure) to the exit plane (top of figure). In experimental study, the fuel and oxidizer are injected separately into the combustion chamber to avoid backfire [2]. The mixing process occurs inside the combustion chamber while detonation wave propagates circumferentially to consume fresh reactive mixture. Schwer et al. [2] investigated the flow field of RDE in general and observed the effect of stagnation and back pressure on an RDE. In addition, Schwer et al.[3] also examined the fluid dynamics of rotating detonation engines with hydrogen and hydrocarbon fuels. Jin Zhou et al.[4] studied the effects of injection nozzle exit width on rotating detonation engine. These studies pertain to stoichiometric conditions. Only a handful of studies have investigated the effects of equivalent ratio. Wang et al.[5] recently investigated the effects of equivalence ratio and found that as the equivalence ratio increases, the velocity of the rotating detonation wave first increases and then decreases. Baoxing et al [6] experimentally studied the effects of equivalence ratio on RDE and found that for their engine model operating with equivalence ratio from 0.42 to 1.43, the rotating detonation wave was successfully initiated, and propagation self-sustained. In this study, we are interested to see how equivalence ratio influence RDE flow field in general. Furthermore, we want to see how it affects the detonation wave structure Key Words: Rotating Detonation Engine, Computational Fluid Dynamics (CFD), Supersonic Combustion, Equivalence Ratio.

Comparison of RDE Simulation Methods

Jacobs Somnic,Foluso Ladeinde 한국추진공학회 2018 한국추진공학회 학술대회논문집 Vol.2018 No.12

Air-breathing Rotating Detonation Engine (RDE) has been widely investigated using a variety of techniques for the kinetic mechanism, turbulence, turbulence-combustion interaction, the spatial and temporal numerical procedure, and the use of Euler or the Navier-Stokes equations. However, there seems to be no consensus presently as to the optimal combination of procedures to use. In this work, a comparison of various modeling options is presented for the physics, chemistry, and numerical modeling of the RDE problem. Differing performance of several kinetic mechanisms has been observed and the two spatial numerical schemes investigated – the Weighted Essentially-Non-oscillatory (WENO) and MUSCL – give significantly different results. In this limited study, Euler and Navier-Stokes give results that are not significantly different, although the real issue in this case is the level of numerical dissipation, since no truly inviscid solutions to the flow equations are physically or numerically realizable. Other effects will be reported during the oral presentation.

스크램제트 엔진의 모드 천이에 관한 연구

하정호(Jeong Ho Ha),Foluso Ladeinde,김희동(Heuy Dong Kim) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12

Dual mode scramjet is typically operated in a range of M<SUB>∞</SUB>= 3 to 6. During operation of dual mode scramjet, transition from ramjet to scramjet and vice-versa is inevitable. In a scramjet mode, the supersonic flow field is formed upstream of combustor, thus having the combustion at a supersonic flow circumstance. Such a flow is typically obtained at a low equivalent ratio. As the equivalent ratio is increasing for a given constant total temperature at the inlet of engine, a shock train is formed due to strong interaction with the wall boundary layer, leading to subsonic combustion. This mode transition is associated with the unsteady behaviors of shock train according to the equivalent ratio at constant inlet total temperature. In the present study, theoretical and computational analyses have been applied to investigate the detailed flow field generating during the mode transition. The obtained results showed that the mode transition does not occur in a gradual process but in a sudden discontinuous variation, leading to having a non-allowable region during the transition.

스크램제트에서 램제트로의 모드 천이로 인한 불허지역

하정호(Jeongho Ha),Foluso Ladeinde,김태호(Taeho Kim),김희동(Heuydong Kim) 한국추진공학회 2017 한국추진공학회 학술대회논문집 Vol.2017 No.5

스크램에서 램제트로의 천이가 일어날 때, thermal choking으로 인한 연소실 입구에서의 급격한 압력 상승은 불가피하다. NAR이라고도 불리는 이러한 현상은 당량비의 과도한 증가에 의해서 관찰된다. 그러나, NAR의 변화에 영향을 미치는 요소들에 대한 연구는 활발하게 이루어지지 않았다. 본 연구에서는 격리부 입구에서의 마하수에 따른 NAR의 변화는 수치해석적 그리고 이론해석적으로 분석되었다. 결론적으로 격리부 입구의 마하수 증가는 NAR의 범위를 확대시킨다. A drastic pressure increment at the combustor inlet induced thermal choking is inevitable during scram-to-ramjet transitions. This phenomenon which is called by Non-Allowable Region(NAR) was observed on the excessive increment in the equivalent ratio. However, many studies were not investigated about factors which affects a variation of NAR. In the present study, a variation of NAR with regard to Mach number in the inlet of isolator is numerically and analytically analyzed. The conclusions from the investigation show that increasing the Mach number in the isolator inlet enlarged in the range of NAR.

스크램제트 엔진의 모드천이 발생동안 의사충격파 유동에 관한 연구

하정호(Jeong Ho Ha),Foluso Ladeinde,김희동(Heuy Dong Kim) 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.12

이중 모드 스크램제트는 일반적으로 기류 마하수 3-6의 범위에서 작동한다. 이중 모드 스크램제트가 작동하는 동안 램제트 모드에서 스크램제트 모드로의 천이 혹은 그 반대의 경우가 불가피하다. 스크램제트 모드에서 연소실의 상류에서는 초음속 영역이 형성이 되며, 이와 같은 유동은 일반적으로 낮은 당량비에서 얻을 수 있다. 엔진의 입구의 전온도가 일정한 경우 당량비가 증가할수록 벽면의 경계층과의 간섭작용에 의해 강한 충격파가 발생해 연소실의 상류는 아음속이 된다. 이 같은 모드 천이는 당량비에 따른 충격파의 비정상 유동 특성과 관련이 있다. 본 연구에서는, 모드 천이가 발생하는 동안 발생하는 상세한 유동 특성을 조사하기 위해 이론해석과 수치해석을 수행하였다. 얻어진 결과로부터 모드 천이는 급격하게 발생한다는 것을 보여준다. Dual mode scramjet is typically operated in a range of M∞= 3 to 6. During operation of dual mode scramjet, transition from ramjet to scramjet and vice-versa is inevitable. In a scramjet mode, the supersonic flow field is formed upstream of combustor, thus having the combustion at a supersonic flow circumstance. Such a flow is typically obtained at a low equivalent ratio. As the equivalent ratio is increasing for a given constant total temperature at the inlet of engine, a shock train is formed due to strong interaction with the wall boundary layer, leading to subsonic combustion. This mode transition is associated with the unsteady behaviors of shock train according to the equivalent ratio at constant inlet total temperature. In the present study, theoretical and computational analyses have been applied to investigate the detailed flow field generating during the mode transition. The obtained results showed that the mode transition does not occur in a gradual process but in a sudden discontinuous variation, leading to having a non-allowable region during the transition.

스크램-램제트 모드 천이에 미치는 연료 당량비의 영향

하정호(Jeong Ho Ha),윤영빈(Youngbin Yoon),Foluso Ladeinde,김태호(Tae Ho Kim),김희동(Heuy Dong Kim) 한국추진공학회 2018 한국추진공학회지 Vol.22 No.1