The T6 Stalker Tunnel is a multi-mode, high-enthalpy, transient ground test facility. It is the first of its type in the UK. The facility combines the original free-piston driver from the T3 Shock Tunnel with modified barrels from the Oxford Gun Tunnel. Depending on test requirements, it can operate as a shock tube, reflected shock tunnel or expansion tube. Commissioning tests of the free-piston driver are discussed, including the development of four baseline driver conditions using piston masses of either 36 kg or 89 kg. Experimental data are presented for each operating mode, with comparison made to numerical simulations. In general, high-quality test flows are observed. The calculated enthalpy range of the experimental conditions achieved varies from $$2.7\hbox { MJ kg}^{-1}$$
2.7
MJ
kg
-
1
to $$115.0\hbox { MJ kg}^{-1}$$
115.0
MJ
kg
-
1
.
Graphical abstract
Scramjet engines must be designed to operate over a range of Mach numbers. In order to maintain robust starting characteristics at low freestream Mach numbers, the inlet contraction ratio must be minimized, reducing performance at high Mach numbers. The technique of thermal compression can be used to maintain robust combustion at low mean pressure and temperature, improving the performance of low inlet contraction ratio engines over a range of Mach numbers. This paper examines a scramjet engine with a threedimensional inlet that induces spanwise gradients of pressure and temperature, producing high inlet compression on one side and low inlet compression on the other. The effect of combustion in each half on pressure throughout the entire flowfield is examined by suppressing combustion on either half of the combustor through injecting either a combusting fuel, hydrogen, or a non-combusting replacement, helium. Two optical techniques are used to examine how the concentration of the OH radical varies throughout the combustor. Images of OH* Chemiluminescence and OH Planar Laser-Induced Fluorescence (PLIF) map the concentration and production of OH radicals indicating chemical activity throughout the combustion process. The thermal compression effect is isolated, and is shown to increase combustion-induced pressure rise in a scramjet engine.
Nomenclaturemomentum flux ratio = forebody shock angle LC = low compression = ratio of specific heats M = Mach number = forebody turning angle N = rotational quantum number = standard deviation P = pressure = fuel-air equivalence ratio q = dynamic pressure Re = Reynolds number 2 Subscripts e = nozzle exit T = total i = shot index ∞ = freestream s = stagnation
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