Scramjet Lift, Thrust and Pitching-Moment Characteristics Measured in a Shock Tunnel

Abstract

Lift, pitching moment, and thrust/drag on a supersonic combustion ramjet were measured in the T4 free-piston shock tunnel using a three-component stress-wave force balance. The scramjet model was 0.567 m long and weighed approximately 6 kg. Combustion occurred at a nozzle-supply enthalpy of 3.3 MJ/kg and nozzle-supply pressure of 32 MPa at Mach 6.6 for equivalence ratios up to 1.4. The force coefficients varied approximately linearly with equivalence ratio. The location of the center of pressure changed by 10% of the chord of the model over the range of equivalence ratios tested. Lift and pitching-moment coefficients remained constant when the nozzle-supply enthalpy was increased to 4.9 MJ/kg at an equivalence ratio of 0.8, but the thrust coefficient decreased rapidly. When the nozzle-supply pressure was reduced at a nozzle-supply enthalpy of 3.3 MJ/kg and an equivalence ratio of 0.8, the combustion-generated increment of lift and thrust was maintained at 26 MPa, but disappeared at 16 MPa. Measured lift and thrust forces agreed well with calculations made using a simplified force prediction model, but the measured pitching moment substantially exceeded predictions. Choking occurred at nozzle-supply enthalpies of less than 3.0 MJ/kg with an equivalence ratio of 0.8. The tests failed to yield a positive thrust because of the skin-friction drag that accounted for up to 50% of the fuel-off drag. Nomenclatureresponse function or matrix H = enthalpy L = lift force l = chord length (=0.567 m) M = Mach number m = pitching moment P = pressure S = reference area (=3.192 × 10 −3 m 2 ) T = temperature t = time u, u = input function or vector v = velocity y, y = output function or vector γ = ratio of specific heats = strain vector ρ = density = equivalence ratio Subscripts A = axial direction a, b, c, d = stress bar A, B, C or D M = moment direction N = normal direction o = about leading edge of model

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

“…Furthermore, it is likely that this result is a consequence of the simple design of the engine. Overall however, the results of the experiments of (Robinson et al, 2006) demonstrate that it is possible to accurately measure the thrust, lift and pitching moment of a single scramjet engine in a shock tunnel.…”

“…Good comparison with predictions was obtained for the thrust and lift forces with both increasing linearly with fuel mass flow rate. The poor prediction of the pitching moment was attributed by Robinson et al (2006) to inaccurate estimation of the pressure distribution on the latter part of the thrust surface. In comparison with the purely analytical method used by Paull et al (1995a) (for example), Robinson (2003d) made use of simple cfd simulations and some of the measured pressure data to determine the theoretical forces.…”

“…Robinson (2003d) and Robinson et al (2006Robinson et al ( , 2004: this thesis and associated papers document the development of a three component balance for the measurement of lift, thrust and pitching moment of moderately sized scramjet engines. See also Robinson (2003a,b,c).…”

“…A new airframe integrated experimental model was developed and tested within the t4 Stalker Tube at The University of Queensland, a facility that has a long history of being used for scramjet-based experimental investigations and a three-component stress wave force balance (Robinson et al, 2006;Simmons et al, 1993) was used to directly measure the lift, thrust and pitching moment of the engine module.…”

Unsteady Thrust Measurement for Pulse Detonation Engine

“…A force measurement method which requires identification of the system's dynamic parameters has been wellestablished in thrust and drag measurements in shock tunnels [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] and appears feasible for application to PDEs. In fact, as an intermediate step, these force measurement techniques can be directly applied to a single-shot…”