Numerical Study of Solid-Rocket Motor Ignition Overpressure Wave Including Infrared Radiation

Abstract

The ignition overpressure wave generated during the pressure build-up of a solid-rocket motor is numerically investigated in this study. Numerical simulations are compared to the LP10 experiments, consisting of the horizontal firing of a scaled-down model for the Ariane 5 P230 booster. The present work aims at the prediction of the main characteristics of the ignition overpressure in the far field and the assessment of afterburning influence on both its formation mechanisms and its alteration by the jet plume. Two three-dimensional large-eddy simulations are performed, one considering inert flow and one modeling the afterburning. Infrared images of the plume are also computed with a dedicated radiation transfer solver. An overall good agreement with the experimental results is reported on amplitude and duration. Nevertheless, the reactive case is found to provide better results on amplitude and directivity. The signature is also better reproduced on the microphones near the jet centerline, and the emitted infrared intensity is well captured. Computations indicate that the formation of the shock wave is obtained by coalescence of compression waves emitted by the accelerating jet at early times. For the reactive case, computations show an increased interaction between the jet and the overpressure wave. Nomenclature A = area, m 2 a = ellipse x-axis length, m b = ellipse y-axis length, m C s = sth far-field microphone c = speed of sound, m · s −1 D = diameter, m e = eccentricity h = infrared field height, m I = acoustic intensity, W k = absorption index l = infrared field length, m M = Mach number m = alumina complex refraction index n = refraction index p = pressure, Pa R = shock traveled distance, m t = time, ms u = velocity, m · s −1 x, y, z = Cartesian coordinates α = far-field microphone angle, deg γ = ratio of specific heats Δp = shock amplitude, Pa Δt = time step, s Δx = maximal grid cell size, mm δ = duration, s λ = wavelength, m ρ = density, kg · m −3 Subscripts 0 = isotropic shock initial characteristics atm = atmospheric conditions bu = properties at rupture instant em = properties at ignition overpressure emission instant i = stagnation value ini = simulation initial characteristics int = shock tube intermediate properties iop = ignition overpressure properties ir = infrared properties j = nozzle exit plane properties le = ignition overpressure leading front arrival time max = ignition overpressure pressure maximum nl = ignition overpressure nonlinear propagation predicted time prop = propellant properties s = far-field sensor index st = shock-tube properties theo = ideal seal rupture characteristics at sensor location tr = ignition overpressure trailing front arrival time Superscript = nozzle throat properties

Large-eddy simulation of supersonic planar jets impinging on a flat plate at an angle of 60 to 90 degrees

“…These three types of waves were analysed by Tsutsumi et al 16 using a snapshot proper orthogonal decomposition with Fourier transformation. Moreover, the transient regime of supersonic jets was investigated by Dargaud et al 17 by conducting the simulation of the ignition overpressure wave generated by horizontal rocket motors interacting with the ground.…”

High-speed jet noise

“…When these motors ignite in a silo, the expelled pressure waves reflect from the silo floor and propagate up over the vehicle. When these motors ignite on an open launch pad, two types of pressure waves are propagated over the vehicle and surrounding structures, see Dargaud et al (2013). In addition to IOP, which is a very strong single transient pressure wave, weaker pressure waves are also continuously emitted from the jet structure of rocket plumes during the rocket liftoff stage.…”

Assessment of a Two-Way Coupling Methodology Between a Flow and a High-Order Nonlinear Acoustic Unstructured Solvers

“…In addition to various experimental studies [5] which have led to significant noise reduction on launch pads [6], semi-empirical jet noise models based on the Lighthill's theory have been formulated [7] and improved [8][9][10] but they are often unsuitable to deal with such realistic space applications. More recently, the development of large-eddy simulation (LES) allowed accurate simulations of hot supersonic jets [11][12][13][14][15], even for increasingly complex configurations as performed with realistic launch pad geometries by Fujii et al [16] or Tsutsumi et al [17]. The computational cost of such simulations remains however heavy for current industrial practices, especially when the acoustic propagation is directly calculated by the flow solver.…”