On　the　Shock　Wave　Arose＆t　Electrical　Spark　Ignltion

Abstract

Numerical　analysis　of　the　sぬock　wave　arisjng　at　electric換1spark　ignition　of　combustible　gas　was　done　by using　the丘nite　di鉦erential　method． Initial　temperature　of　the　spark　kemel　was　set　equal　to2000K，3000K　and4000K　Peak　pressure　of　the　skock wave　varied　depending　on　the　initlal　temperature，but　the　shock　wave　arose　in　all　cases，The　shock　wave　survived in　feW　miCrOSeCOndS　and　prOpagated　abOUt　l　mm・TheSe　VaIUeS　are　bOth　Smaller　than　the　Va1UeS　ObSerVed popularly　in　the　experimental　shock　waves．It　is　considered　to　be　due　to　the　instantaneous　supply　of　thermal energy　in　the　calculation．In　experimental　studies，finite（1uration　time　is　required　for　a　electricalspark、 In　this　study，a　few　tenths　of　thennal　energy　was　converted　to　kinetic　ellergy　of　the　shock　wave、1n　the　time period　in　which　the　shock　wave　survives，chemical　reaction　proceeded　little　and　could　be　ignored　in　calculation、Hot　body　of　the　spark　kemel　expanded　with　the　shock　wave　propagation，but　its　expansion　was　slower　than　the shock　wave　propagation．Temperature　at　the　center　of　the　spark　kemel　decresed　with　time歩and　a　hotter　part apPeared　at　the　outer　edge　of　the　kerneL　Surrounding　gas　of　the　spark　kernel　was　heated　a　little　after　the　shock wave　passed． The　shock　wave　is　usually　ignored　in　a　nurerical　analysis　of　the　electrical　spark　ignition　of　the　combustible gas，The　result　of　thisstudy　revealed　the　presence　ofthe　shock　wave　affectsthe　distribution　ofthe　tkermal　energy．It　should　be　taken　into　account　in　such　an　analysis.