Research On The Hot Surface Ignition Condition Of Hydrogen-air Mixture

Aiming at the pre-ignition caused by hot spots in HICE,based on the prototype of the CVCB with an overhead glow plug,the two heating durations(t_ch1 and t_ch2)were firstly researched under different fuel-air equivalence ratio?0.5¹.0?,initial temperature?400⁸20K?,initial pressure?1.5¹8bar?,hot surface temperature?1200²000K?and hot surface area?129.59¹99.69mm²?through simulation using the orthogonal experiment design scheme,and the influence of each factor on the two heating durations was analyzed,respectively.The results of the heating duration t_ch1 show that,the order of the effect of each factor on the hot surface ignition is as follow: hot surface temperature > initial pressure of hydrogen-air mixture > equivalent ratio > initial temperature of hydrogen-air mixture > hot surface area.The heating duration t_ch1 is decreased first and then increased slightly with the increase of the equivalent ratio,reaching the minimum value 0.354 ms when the equivalent ratio is 0.750.Before 505 K,147.94mm²,the heating duration t_ch1 of hot surface ignition decreases rapidly with the initial temperature and the hot surface area increasing.After 505 K,147.94mm²,the heating duration t_ch1 shows a slight fluctuation with the increase of the initial temperature and the hot surface area,the maximum amount of fluctuation is 0.866 ms and 0.816 ms,respectively.With the initial pressure and the hot surface temperature increasing,the heating duration t_ch1 decreases rapidly initially and followed by a gentle decrease.The results of the heating duration t_ch2 show that,in order to prevent the occurrence of pre-ignition,the seven states where the abnormal combustion occurs should be avoided in the HICE.Except for the initial pressure of hydrogen-air mixture,the influence of each factor on t_ch2 is similar to that of t_ch1.The influence of the hot surface characteristic parameters?hot surface temperature and hot surface area?on the heating duration t_ch1 was further studied in detail.The results show that,when the hot surface temperature is low,the heating duration t_ch1 is sensitive to the hot surface temperature.With the increase of the hot surface temperature,the heating duration t_ch1 decreases with the increase of the hot surface area,but the decline amplitude is gradually reduced.When the hot surface temperature is higher than 1200 K,the influence of the hot surface area on the heating duration t_ch1 can be almost negligible.On this basis,the critical ignition temperature was proposed,and the relationship between the critical ignition temperature,the heating duration t_ch1 and the hot surface area was studied and established.The results show that,within the range of the studied parameters,the heating duration t_ch1 is the only major factor affecting the critical ignition temperature.Finally,the research results were applied to analyze the pre-ignition in HICE.The critical ignition temperature of the pre-ignition at different rotational speeds of the HICE and the variation of the critical ignition temperature with the speed were obtained.