It is well known that the cylinder tests have been conducted with four different initial densities for PETN (pentaerythritol tetranitrate), and JWL parameters for each test are available, which describe the isentropic release of detonation gases from the estimated C-J (Chapman-Jouguet) state for each initial density. These datasets of ρ-υ isentropes contain information on the equation of state (EOS) of detonation product gases provided that all four detonations can be described by a unique EOS for detonation product gases of the same chemical composition. In this paper, we assumed the Grüneisen type EOS and also the Rice-Walsh type EOS in order to search for the EOS compatible with all the cylinder tests. For this purpose, six different forms of EOSes were tested. It is shown that both the simple Grüneisen type EOS with Grüneisen parameter assumed as a function of volume alone, and the Rice-Walsh EOS with Wu- Jing parameter assumed as a function of pressure alone, were incompatible with the experimental data. Among tested EOSes, it is concluded that the only possible EOS which can describe all the release isentropes obtained by the cylinder tests is the extended Grüneisen EOS with the Grüneisen parameter containing a term of the thermal contribution squared.
detonation product gases, JWL parameters, Grüneisen equation of state, Rice-Walsh equation of state