Parametric study of a laser ignited hydrogen-air mixture in a constant volume combustion chamber

Experiments were carried out in a constant volume combustion chamber (CVCC) to investigate flame kernel development and flame speed of hydrogen-air mixtures having different fuel-air ratios. A Q-switched Nd: YAG laser with 1064 nm wavelength and pulse duration of 6-9 ns was used for ignition by generating laser induced plasma inside the CVCC. In this study, laser induced ignition of hydrogen-air mixtures was investigated using different initial chamber filling pressures (P = 2.5 bar-10 bar) at different initial temperatures (373 K-523 K). A variable optical setup with converging lenses having different focal lengths (f = 100-250 mm) were used to position the plasma at various locations inside the CVCC. A high speed camera recorded the flame kernel development and a piezoelectric pressure transducer recorded the pressure-time history for all the experiments. The main objective of this study was to determine the dependence of combustion properties of laser ignited hydrogen-air mixtures on lasers, optical configurations and initial conditions prevailing in the CVCC.