Laminar burning speeds and flame structures of mixtures of difluoromethane (HFC-32) and 1,1-difluoroethane (HFC-152a) with air at elevated temperatures and pressures

Laminar burning speeds and flame structures of difluoromethane (HFC-32)/air and 1,1-difluoroethane (HFC-152a)/air mixtures have been studied. Experiments have been carried out in constant-volume spherical and cylindrical vessels coupled with a schlieren/shadowgraph system and high-speed complementary metal-oxide-semiconductor (CMOS) camera. Laminar burning speed was determined using a thermodynamic model that employs the pressure rise history of the combustion process. Experiments were conducted for different initial conditions over a wide range of equivalence ratios. Laminar burning speeds of HFC-152a/air mixtures have been measured over the temperature range of 298 K to 580 K and pressure range of 1 to 8 bar. Laminar burning speeds of HFC-32/air mixtures have been measured for the temperature range of 350 K to 475 K and pressure range of 2 to 6.8 bar. Correlations have been developed for laminar burning speeds of HFC-32 and HFC-152a to demonstrate the temperature and pressure dependency of laminar burning speeds of these two refrigerants.