Transverse and parallel injection of hydrogen with supersonic combustion in a shock tunnel

Wendt, M.; Stalker, R. J.

doi:10.1007/bf02511404

Cited by 15 publications

(6 citation statements)

References 8 publications

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“…For example, reaction 9 replaces the reactive radical H with the relatively nonreactive HO 2 molecule. Reactions 6,7,8, and 20 are the three-body reactions responsible for the majority of the combustion heat release. Because they are threebody reactions, they depend on the concentration of radicals being high for significant heat release to occur and thus depend on the branching cycle.…”

Section: Hydrogen-air Combustion Modelmentioning

confidence: 99%

“…If the mixture temperature is high enough, then the combustion reaction rates are high and heat is released as fast as the mixing occurs. This is known as mixing-controlled combustion (for example, Wendt and Stalker [8]). On the other hand, if the mixture temperature is low, then the combustion reaction rates are low and the rate of heat release is governed by the chemistry and the combustion becomes reaction-rate-controlled (for example, Pulsonetti [9]).…”

mentioning

confidence: 98%

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Radical-Farm Ignition Processes in Two-Dimensional Supersonic Combustion

McGuire

Boyce

Mudford

2008

Journal of Propulsion and Power

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A two-dimensional numerical study was performed of the ignition processes associated with the concept of radical farming for supersonic combustion. In a preliminary parametric study, a range of freestream conditions attainable in a hypersonic shock tunnel was investigated and mapped according to whether or not the behavior known as radical farming is present: a combustion-induced pressure rise in second or subsequent hot pockets rather than the first. Two such cases were analyzed in detail, both having mean conditions across the combustion-chamber entrance that would result in extremely long ignition lengths. The initiation, branching cycle, and heat release reactions in the combustion process become active in the radical farm, and H and OH radicals are produced. Their rate of production slows in the regions of flow expansion, but does not approach chemical freezing until toward the end of the localized expansion zones. Simultaneously, heat release elevates the local temperature. When the mixture flows through the shock at the second hot pocket, the elevated temperature and the presence of radicals enable the branching cycle and three-body recombination heat release reactions to accelerate, and significant pressure rise due to heat release is then able to occur. The extent to which this is completed in the second hot pocket depends on the inflow conditions.

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Section: Hydrogen-air Combustion Modelmentioning

confidence: 99%

mentioning

confidence: 98%

Radical-Farm Ignition Processes in Two-Dimensional Supersonic Combustion

McGuire

Boyce

Mudford

2008

Journal of Propulsion and Power

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“…Next, injection from a wall orifice was investigated (26) and results were compared with those obtained for central strut injection. The experiments with central injection were done in the duct of Fig.…”

Section: Fuel Injectionmentioning

confidence: 99%

Scramjets and shock tunnels—The Queensland experience

Stalker

Paull

Mee

et al. 2005

Progress in Aerospace Sciences

129

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This article reports on the use of a shock tunnel to study the operation of scramjet powered configurations at sub-orbital velocities above 2 km/s. Thrust, as given by a net thrust equation, is used as a figure of merit throughout the study. After a short description of the shock tunnel used and its operating characteristics, experiments on the combustion release of heat in a constant area duct with hydrogen fuel are reviewed. The interaction between heat release in the combustion wake and the walls of the duct produced pressure distributions which followed a binary scaling law, and indicated that the theoretically expected heat release could be realized in practice, albeit with high pressure or long combustion ducts. This heat release, combined with attainable thrust nozzle characteristics and a modest level of configuration drag, indicated that positive thrust levels could be obtained well into the sub-orbital range of velocities. Development of a stress wave force balance for use in shock tunnels allowed the net thrust generated to be measured for integrated scramjet configurations and, although the combination of model size and shock tunnel operating pressure prevented complete combustion of hydrogen, the cruise condition of zero net thrust was achieved at 2.5 km/s with one configuration, while net thrust was produced with another configuration using an ignition promoter in hydrogen fuel. Nevertheless, the combination of boundary layer separation induced inlet choking and limited operating pressure levels prevented realization of the thrust potential of the fuel. This problem may be alleviated by recent increases in the shock tunnel operating pressures, and by promising research involving inlet injection of the fuel. Research on the drag component of the net thrust equation resulted from the development of a fast response skin friction gauge. It was found that existing theories of turbulent boundary skin friction predicted the skin friction when combustion of hydrogen occurred outside the boundary layer, but combustion within the boundary layer dramatically reduced the skin friction. Finally, for the first time in the world, supersonic combustion was produced in a free flight experiment. This experiment validated shock tunnel results at stagnation enthalpies near 3 MJ/kg.

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“…It may be noted the fuel injection on the model takes place through a single wall orifice, rather than through a strut spanning the duct, and the combustion chamber flow therefore is not two dimensional. However, experiments have been reported' 14 ' in which the two types of injection were compared under conditions such that the flow was mixing limited, and were found to yield approximately the same combustion pressure rise along the duct. This indicates that mixing is not markedly influenced by the type of injection, and strongly suggests that reaction limited flows will be similarly unaffected.…”

Section: The Flow Path -Fuel Onmentioning

confidence: 99%

Experiments on cruise propulsion with a hydrogen scramjet

Stalker

Paull

1998

Aeronaut. j.

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Measurements of drag have been made, in a shock tunnel, on a simple integrated vehicle-engine combination for hypersonic cruise with hydrogen scramjet propulsion. The test flow Mach number was 6·4, and the velocity was 2·45 kms-1. Zero drag, which is the necessary condition for cruise, was achieved as the equivalence ratio approached one. It was found that an analysis using established aerodynamic concepts was adequate for predicting drag in the case of no combustion. When combustion occurred results of direct connect experiments provided a qualitative guide to the measured levels of drag, and indicated that thrust nozzle combustion was taking place. An heuristic analysis is used to point to the important effect this may have on propulsive lift.

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Transverse and parallel injection of hydrogen with supersonic combustion in a shock tunnel

Cited by 15 publications

References 8 publications

Radical-Farm Ignition Processes in Two-Dimensional Supersonic Combustion

Radical-Farm Ignition Processes in Two-Dimensional Supersonic Combustion

Scramjets and shock tunnels—The Queensland experience

Experiments on cruise propulsion with a hydrogen scramjet

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