1. mixtures is far from new. Reports dating to 1949 discuss this phenomenon. Two forms of reflected shock ignition are distinguishedin ref. 17:
2. The test conditions of ref. 20 were duplicated in the HYPULSE expansion tube and, usingan OHdetector focusedonthetestgasinthe acceleration tube, the OH radid was indeed observed to be present. These are conditions at which no reaction whatever shouldbe occurringif the ZND model is employed with the currently accepted C q - q chemical kinetic mechanism. Clearly, the conjecture in ref. 1cited above was correct, and weak ignition of the fuel-oxidizer mixture had occurred upstream of the test section. The perturbation-induced phenomena discussed aboveare,therefore, notlimitedto 9-4systems. Facilities Suitable for SDTReasearch
3. Areview of facilities applicable to hypersonicexperimentationandenginedevelopment iscontainedin ref.21. Thestream chemistryissues raised therein apply here aswell. For example,in performingPMSICinlet/combustormodeltests,the air supplied must be sufficiently low in concentrationsof NO and 0to ensurethat ignition phenomena are not compromised. Inlet shock ignitionorcombustorwaveignitionwhichwouldnot occur in tlight lead to incorred conclusions concerning a particular design. Facilities that stagnate the air at high temperature and pressure and failto recombine the dissociatedspeciesin the facilitynode,resultinginconsiderablequantitiesof atomic oxygen and nitric oxide, must be deemed unsatisfactory above, perhaps, Mach 10-12 flight total enthalpyconditions(ref.21). Reflectedshock tunnels and arc-heated wind tunnels present this problem.
4. The next step in the evolution of a model strategyforPMSICenginesimulationistointegrate anenginemodelandtest facilitynozzleinamanner such that the facility nozzle simulates at least a portion of the inlet compression system. This techniquehasbeenextensivelyemployedbyStalker and co-workers (refs. 23-27), among others, primarily forstudiesof dihiveburningsaamjets. A basic PMSICsimulation is d e m i in ref. 23. In thisparticular example,depicted inFwU,fuel was injected within the model itself, and was not fully premixed. Adequate length to achieve full premixing while retaining praaical model dimensionscanonlybeachievedbyinjectingfuelin the inlet section represented by the facilitynozzle. Thisapproachhasnotyetbeenattemptedaspartof a PMSIC engine simulation technique, although there isnothingfundamentalprecludingit.