Performance of a Titan Rocket Engine Using Laser-Induced Fluorescence of OH

Abstract

Rocket engine performance can be modeled by considering separately the propellant delivery system distribution, combustion efe ciency including propellant vaporization and gas-phase mixing, and nozzle expansion efe ciency. Although these quantities can be modeled, experimental verie cation is extremely helpful for separately understanding these processes and for design improvements. Laser-induced e uorescence of OH, excited by a KrF excimer laser operating at 248 nm, is used to measure the concentration of the OH radical across the exit plane of a e ring Titan IV, stage I, liquid rocket engine, from which the combusting mixture ratio proe le could be inferred. Thesemeasurementsallowassessmentofthedegreeofmixing and potential e owstratie cationbetween theinjector core, combustion bafe es, and combustion chamber fuel-e lm cooling and can help to provide the basis for future performance optimization. Nomenclature A = Einstein A coefecient Aa = area of the laser beam (height times thickness ) B12 = Einstein second coefe cient for stimulated absorption c = speed of light E = laser energy per pulse fB.T/ = temperature-dependent Boltzmann fraction of the absorbing state g.o/ = spectral overlap function ho = energy of a scattered photon K = non-noise-free gain factor M = magnie cation of the imaging system Nc = number of counts recorded by the camera per pixel Np = number of laser pulses integrated NT = total number density of the gas Pc = rocket engine combustion chamber pressure Qpre = predissociation rate S = e uorescence signal T = gas temperature uradial = radial component of the velocity V = collection volume ´ = collection efe ciency ÂOH = mole fraction of OH A = collection solid angle per pixel ! = wave number of the laser Subscript pp = per pixel