Laser measurement techniques applied to turbulent combustion in piston engines

Air-Fuel Mixture Characteristics of Reciprocating Engines

“…Attempts to obtain such measurements using laser-excited fluorescence, Raman spectroscopy and laser Rayleigh scattering have been reported by Smith (1980), Cole and Swords (1980) and Green and Whitelaw (1987), but the emphasis has been on technique development. Efforts involving the study of turbulent combustion in engines using combined laser techniques have been reported on by Witze and Dyer (1986).…”

Emerging combustion diagnostics

“…Suitable pulse-repetition rates can be provided by continuous-wave lasers strobed using an acoustooptic modulator or by mode-locked, continous-wave sources. 36 ' 37 Unfortunately, imaging of schlieren signals to obtain two-dimensional flame shapes has been of limited utility in and of itself, because relating the images obtained to quantities such as temperature, pressure, or concentration is difficult. 38 As a result, high-speed schlieren is often accomplished simultaneously with some quantitative measurement, either globally (as in high-speed pressure-transducer measurements) or locally (as in high-speed LDV measurements of velocity).…”

“…34 ' 35 While high-repetition-rate imaging studies of combustion processes have been accomplished using both natural and chemically induced flame luminosity, both methods are restricted severely in temporal resolution; schlieren and shadowgraph techniques using laser illumination can overcome this difficulty. 36 Lasers offer high irradiance with short temporal pulse durations, important for "freezing" combustion events in time. Suitable pulse-repetition rates can be provided by continuous-wave lasers strobed using an acoustooptic modulator or by mode-locked, continous-wave sources.…”

“…38 As a result, high-speed schlieren is often accomplished simultaneously with some quantitative measurement, either globally (as in high-speed pressure-transducer measurements) or locally (as in high-speed LDV measurements of velocity). 36 ' 38 Simultaneous accomplishment of high-speed schlieren with a second quantitative measurement is complicated when using conventional film to collect signals by synchronization difficulties resulting in temporal uncertainty. 32 Other practical issues include film heating and the handling requirements imposed by large numbers of exposed film reels.…”