Optical Experimental Study on Knock Characteristics of Hydrogen-Air Pre-mixture

By means of schlieren method and gas pressure measurement, knock characteristics of hydrogen-air pre-mixture has been studied in constant volume combustion chamber. The effects of initial temperature, initial pressure and equivalence ratio on flame development process and pressure characteristics have been investigated. The experimental results show that knock caused by auto-ignition of unburned gas appears firstly in the angle region between the spherical flame front and the wall of combustion chamber on this paper's condition, detonation occurs easilier with higher temperature, higher pressure and higher equivalence ratio, the higher the initial temperature is, the faster the pressure rises, but the lower the peak pressure is, pressure increases faster and meanwhile peak pressure is higher according to higher initial pressure, severe knock emerges on the conditions of low temperature and high pressure.