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Experimental data obtained in this study (Part II) complement the speciation data presented in Part I, but also offer a basis for extensive facility cross-comparisons for both experimental ignition delay time (IDT) and laminar flame speed (LFS) observables.To improve understanding of the ignition characteristics of propene, a series IDT experiments were performed in six different shock tubes and two rapid compression machines (RCMs) under conditions not previously studied. This study is the first of its kind to directly compare ignition in several different shock tubes over a wide range of conditions. For common nominal reaction conditions among these facilities, cross-comparison of shock tube IDTs suggests 20-30% reproducibility (2σ) for the IDT observable. The combination of shock tube and RCM data greatly expands the data available for validation of propene oxidation models to higher pressures (2-40 atm) and lower temperatures (750-1750 K).Propene flames were studied at pressures from 1-20 atm and unburned gas temperatures of 295-398 K for a range of equivalence ratios and dilutions in different facilities. The present propene-air LFS results at 1 atm were also compared to LFS measurements from the literature. With respect to initial reaction conditions, the present experimental LFS cross-comparison is not as comprehensive as the IDT comparison; however, it still suggests reproducibility limits for the LFS observable. For the LFS results, there was agreement between certain data sets and for certain equivalence ratios (mostly in the lean region), but the remaining discrepancies highlight the need to reduce uncertainties in laminar flame speed experiments amongst different groups and different methods. Moreover, this is the first study to investigate the burning rate characteristics of propene at elevated pressures (> 5 atm).IDT and LFS measurements are compared to predictions of the chemical kinetic mechanism presented in Part I and good agreement is observed.

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Infrared laser-absorption spectroscopy (IR-LAS) sensors play an important role in diagnosing and characterizing a wide range of combustion systems. Of all the laser-diagnostic techniques, LAS is arguably the most versatile and quantitative, as it has been used extensively to provide quantitative, species-specific measurements of gas temperature, pressure, composition and velocity in both laboratory-and industrial-scale systems. Historically, most IR-LAS work has been conducted using tunable diode lasers, however, today's researchers have access to a wide range of light sources that provide unique sensing capabilities and convenient access to nearly the entire IR spectrum (≈1 to 20 μm). In particular, the advent of room-temperature wavelength-tunable mid-infrared semiconductor lasers (e.g., interband-and quantum-cascade lasers) and hyperspectral light sources (e.g., Fourierdomain mode-locked lasers, dispersed supercontinuum lasers, and frequency combs) has provided a number of unique capabilities that combustion researchers have exploited. The primary goal of this review paper is to document the recent development, application, and current capabilities of IR-LAS sensors for laboratory-and industrial-scale combustors and propulsion systems. A thorough review and description of the fundamental spectroscopy governing the accuracy of such sensors, and recent findings and databases that enable improved modeling of molecular absorption spectra will be provided. Modern light sources and the most commonly used diagnostic techniques are also discussed.

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Using FM spectroscopy formyl radicals were detected for the first time behind shock waves. HCO radicals have been generated by 308 nm photolysis of mixtures of formaldehyde in argon. The HCO spectrum of the (A ˜2A 00 X ~2A 0 ) (09 0 0 00 1 0) transition was measured at room temperature with high resolution and the predissociative linewidths G of the individual rotational lines were fitted to G ¼ X + ZN 02 (N 0 + 1) 2 , where X ¼ 0.22 cm À1 and Z ¼ 1.0  10 À5 cm À1 . Since FM spectroscopy is very sensitive to small line shape variations the spin splitting in the Q-branch could be resolved.Time resolved measurements of HCO profiles at temperatures below 820 K provided the temperature independent rates of reaction ( 4), H + HCO ! H 2 + CO, and reaction (5), HCO + HCO ! CH 2 O + CO,and the low pressure room temperature absorption cross section of the Q( 9)P(2) line at 614.872 nm, a c ¼ (1.5 AE 0.4)  10 6 cm 2 mol À1 (base e).Measurements of the unimolecular decomposition of HCO, reaction (3) HCO + M ! H + CO + M, were performed at temperatures from 835 to 1230 K and at total densities from 3.3  10 À6 to 2.5  10 À5 mol cm À3 . They can be represented by the following Arrhenius expression. k 3 ¼ 4:0  10 13 ÁexpðÀ65 kJ mol À1 =RTÞ cm 3 mol À1 s À1 ðD log k 3 ¼ AE0:23ÞThe corresponding RRKM fit, 4.8  10 17 Á(T/K) À1.2 Áexp(À74.2 kJ mol À1 /RT ) cm 3 mol À1 s À1 (600 < T/ K < 2500), supports the lower range of previously reported high temperature rate expressions.

We report an experimental investigation that reveals significant differences in the near-flowfield properties of hydrogen and ethylene jets injected into a supersonic crossflow at a similar jet-to-freestream momentum flux ratio. Previously, the momentum flux ratio was found to be the main controlling parameter of the jet's penetration. Current experiments, however, demonstrate that the transverse penetration of the ethylene jet was altered, penetrating deeper into the freestream than the hydrogen jet even for similar jet-to-freestream momentum flux ratios. Increased penetration depths of ethylene jets were attributed to the significant differences in the development of large-scale coherent structures present in the jet shear layer. In the hydrogen case, the periodically formed eddies persist long distances downstream, while for ethylene injection, these eddies lose their coherence as the jet bends downstream. The large velocity difference between the ethylene jet and the freestream induces enhanced mixing at the jet shear layer as a result of the velocity induced stretching-tilting-tearing mechanism. These new observations became possible by the realization of high velocity and high temperature freestream conditions which could not be achieved in conventional facilities as have been widely used in previous studies. The freestream flow replicates a realistic supersonic combustor environment associated with a hypersonic airbreathing engine flying at Mach 10. The temporal evolution, the penetration, and the convection characteristics of both jets were observed using a fast-framing-rate ͑up to 100 MHz͒ camera acquiring eight consecutive schlieren images, while OH planar laser-induced fluorescence was performed to verify the molecular mixing.

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