Numerical Investigation of the Mixing Process in Inlet-fuelled Scramjets

Gehre, Rolf; Peterson, David M.; Wheatley, Vincent; Boyce, Russell

doi:10.1007/978-3-319-16838-8_32

Cited by 12 publications

(18 citation statements)

References 10 publications

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“…Far-field mixing is controlled by turbulent diffusion and is enhanced when the flow passes through shock waves, owing to baroclinic torque generated from the pressure and density gradients of the plume and air. In the interest of brevity, the mixing processes are not detailed further; however, further discussion on the mixing processes in inlet-fueled scramjets can be found in [29,30]. Figure 15 shows the combustion efficiency and temperature contours in the engine for the reacting simulation.…”

Section: Two-dimensional Resultsmentioning

confidence: 99%

Numerical Investigation into the Combustion Behavior of an Inlet-Fueled Thermal-Compression-Like Scramjet

2015

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A numerical study on the combustion behavior of an inlet-fueled three-dimensional nonuniform-compression scramjet is presented. This paper is an extension to previous work on the combustion processes in a premixed threedimensional nonuniform-compression scramjet, where thermal compression was shown to enhance combustion. This paper demonstrates how thermal compression can be used in a generic scramjet configuration with a realistic fuelinjection method to enhance performance at high flight Mach numbers. Such a scramjet offers an extra degree of freedom in the design process of fixed-geometry scramjets that must operate over a range of flight Mach numbers. In this study, how the combustion processes are affected is investigated, with the added realism of inlet porthole fuel injection. Ignition is established from within a shock-induced boundary-layer separation at the entrance to the combustor. Radicals that form upstream of the combustor within the inlet, from the injection method, enhance combustion. Coupling of the inlet-induced spanwise gradients and thermal compression improves combustion. The results highlight that, although the fuel-injection method imparts local changes to the flow structures, the global flow behavior does not change compared to previous premixed results. This combustion behavior will be reproduced when using other fueling methods that deliver partially premixed fuel and air to the combustor entrance.

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Section: Two-dimensional Resultsmentioning

confidence: 99%

Numerical Investigation into the Combustion Behavior of an Inlet-Fueled Thermal-Compression-Like Scramjet

2015

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“…Secondly, combustion of the inlet injected fuel raises the average temperature and density within the combustor, decreasing the reaction time of the fuel injected at the step (see Rogers and Schexnayder, 1981, and Figure 6.8 of this thesis). Thirdly, interaction of the inlet fuel plumes with the cowl shock (and its reflections) changes the vorticity within the combustor leading to improved mixing of the step injected fuel (Buttsworth, 1996;Gehre et al, 2013;Schetz et al, 2010). Thus, in the context of the inlet and step injection scheme data, the combined injection scheme data unequivocally demonstrate the importance of inlet injection as a means of promoting combustion of fuel injected at the step.…”

Section: Fuel-off Datamentioning

confidence: 96%

“…Three mechansims are hypothesised to be at work. Firstly, the interaction of the inlet fuel plumes with the engine cowl shock would increase vorticity within the combustor, thereby increasing the mixing of the step injected fuel (Buttsworth, 1996;Gehre et al, 2013). Secondly,…”

Section: Thesis Findingsmentioning

confidence: 99%

An experimental investigation of an airframe integrated three-dimensional scramjet engine at a Mach 10 flight condition

Doherty¹

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The University of Queensland in 2014 school of mechanical and mining engineering centre for hypersonics abstract Realisation of the dream of airbreathing access-to-space requires the development of a scramjet engine that produces sufficient net thrust to enable acceleration over a wide Mach number range. With engines that are highly integrated with the airframe, the net performance of a scramjet powered vehicle is closely coupled with the vehicle attitude and is difficult to determine only from component level studies. This work investigates the influence of airframe integration on the performance of an airframe integrated scramjet through the measurement of internal pressure distribution and the direct measurement of the net lift, thrust and pitching moment using a three-component stress wave force balance. The engine chosen as the basis for this study was the Mach 12 rectangularto-elliptical shape-transition (m12rest) scramjet that was developed by Suraweera and Smart (2009) as a research engine for access-to-space applications. The inlet and combustor flowpath were integrated with a slender 6°wedge forebody, streamlined external geometry and three dimensional thrust nozzle. The scale of the engine was chosen so that the entire engine would fit within the core-flow diamond (bi-conic) produced by a Mach 10 facility nozzle. The Mach 10b facility nozzle was chosen because it is the largest nozzle current in use with the t4 Stalker Tube and because the offdesign performance of a scramjet engine is of interest for access-to-space vehicles that must accelerate over a range of Mach numbers.Freejet experiments were conducted within the t4 Stalker Tube. Two trueflight Mach 10 test conditions were used: a high pressure test condition that replicated flight at a dynamic pressure of 48 kPa and a low pressure test condition that replicated flight at a dynamic pressure of 28 kPa. Scaling of the test conditions according to the established binary scaling law was not completed due to facility operational limits.The engine featured two fuel injection stations from which gaseous hydrogen was injected. The first injection station was partway along the length of the inlet while the second injection station was at the start of the combustor behind a rearward facing circumferential step. In addition to investigating inlet-only and step-only injection, a combined scheme where 68 % of the fuel was injected from the step station and 32 % from the inlet station was also investigated.To support the analysis of the experimental results, numerical simulations of the engine with no fuel injection were conducted using the nasa code vulcan. Analysis of the simulations show that the mass capture ratio with respect to the projected inlet area is approximately 60 % at each test condition. The simulations also show that spillage of flow from the slender forebody accounts for just 12 % of the flow through the projected iii inlet area, a small but non-negligible fraction. By integrating the engine surface forces, the drag coefficient with respect ...

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“…In addition to some fuel-air mixing occurring on the intake, inlet injection enables the fuel plumes to interact with the strong shocks and rarefactions at the combustor entrance, which greatly accelerates the mixing rate. 15,16 Consequently, partially premixed supersonic combustion is anticipated in the combustor, which may alter the distribution of turbulent combustion regimes from previously studied scenarios (e.g. Potturi et al 17 ).…”

Section: Introductionmentioning

confidence: 97%

Combustion Regimes in Inlet-fulled, Low Compression Scramjets

Gehre¹,

Wheatley²,

Boyce³

2015

20th AIAA International Space Planes and Hypersonic Systems and Technologies Conference

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This paper investigates the combustion regimes that are present in inlet-fueled, low compression scramjets. Injection of fuel in the inlet allows mixing to take place prior to ignition, and permits the fuel plumes to interact with strong shocks and rarefactions at the combustor entrance, which accelerates the mixing process. Consequently, the combustion is partially premixed. Wall-modeled large-eddy simulations (WMLES) are used to accurately resolve or model the turbulent flow structures occurring during the supersonic combustion process. Based on the WMLES data, spatial distributions of turbulent and chemical time scales can be extracted and used to determine the representative turbulent Damköhler and Reynolds numbers. The collective WMLES data is visualized using the Williams diagram, which shows that a wide range of combustion regimes are present throughout the supersonic combustion process. NomenclatureDa t Turbulent Damköhler number H Altitude, m J Momentum flux ratio Ka Karlovitz number k Turbulence kinetic energy, J/kg l 0 Integral length scale, m l c Chemical length scale, m l δ Reaction zone length scale, m M Mach numbeṙ m Mass flow rate, kg/s p Pressure, Pa q Dynamic pressure, Pa R N Leading edge radius, m Re t Turbulent Reynolds number Re u Unit Reynolds number s L Flame speed, m/s T Temperature, K u Velocity, m/s Turbulent dissipation, J/(kg s) η Kolmogorov length scale, m ν Laminar kinematic viscosity, m 2 /s τ c Chemical time scale, s τ δ Reaction zone time scale, s * PhD Student, School of Mechanical and Mining Enginieering, University of Queensland, Student Member AIAA.

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Numerical Investigation of the Mixing Process in Inlet-fuelled Scramjets

Cited by 12 publications

References 10 publications

Numerical Investigation into the Combustion Behavior of an Inlet-Fueled Thermal-Compression-Like Scramjet

Numerical Investigation into the Combustion Behavior of an Inlet-Fueled Thermal-Compression-Like Scramjet

An experimental investigation of an airframe integrated three-dimensional scramjet engine at a Mach 10 flight condition

Combustion Regimes in Inlet-fulled, Low Compression Scramjets

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