Pressure　of　Secondary　Shock　Waves　in　Film　Detonation

Abstract

This　paper　is　devoted　to　the　experimental　study　of　nlm　detonations　wherein　the　fuel　is　very　non-volatile　liquid　combustibles　such　as　decane，1－octanol　in　a　state　of　thin　film　on　the　bottom　wall　of　a　duct and　the　oxidizer　is　gεlseous　oxygen　at　atmospheric　pressure． The　experiments　were　conducted　in　a　height-longer　rectangular　duct 2880 mm　long．Its　oross-sectional　area　was 16x32 mm²　Pressure　of　the　secondary　shock　waves　separated　from　the　Ieading shock　waves　were　measured　with　a　piezoelectric　pressure　transducer．　To　identify　the　pressure　wave with　the　phenomenon　the　streak　schlieren　photography　with　two　parallel　alternately　broken　slits　were used　at　the　same　time　and　the　same　position． Secondary　shock　wave　is　strengthen　while　it　propagates　in　the　combustion　region　and　reaches maximum　pressure　in　the　vicinity　of　the　combustion　front．　The　secondary　shock　wave　becomes　weak gradually　with　separating　from　the　combustion　region，　And　pressure　of　it　becomes　almost　equivalent to　that　of　the　leading　shock　wave　when　it　interacts　with　the　leading　shock　wave．　Such　a　process　that a　sec（mdary　shock　wave　is　strengthened　and　weakened　is　repeated　between　the　upper　and　the　Iower parts　of　the　wall　of　the　duct， Pτessure　of　a　secondary　shock　wave　may　reach2to3times　higher　than　that　of　the　Ieading　shock wave　in　an　ordinary　case，while　out　of　the　ordinary　case　the　former　may　reach60r　more　times　the latteL　It　is　presumed　that　such　a　phenomenon　that　shows　abnormally　high　pressure　is　attributed　to　a secondary　shock　wave　accompanied　with　a　combustion　front．