Study on anisotropic effect correction term of Virial–Peng–Long equation of state

Abstract

In order to correct the calculation deviation of the VPL (Virial–Peng–Long) equation of state (EOS) of gaseous detonation products, based on the L-J (Lennard-Jones) 6-12 spherical molecular potential, the change in the pressure–volume–temperature (PVT) relationship of polyatomic molecular gas at high temperature and high pressure due to the anisotropic effect of the molecular structure is calculated, further improving the accuracy of the VPL EOS in describing the PVT relationship of high temperature and high pressure gas. In this paper, on the basis of the original VPL EOS, the anisotropic effect correction term, whose form is similar to the virial terms, is introduced. Taking the PVT data of CH4 (P = 0.02–187.3 GPa and T = 752–4369 K) as the reference value, the multi-objective optimization genetic algorithm is used to calibrate the coefficients of the correction term, and the VPLR (Virial–Peng–Long-Refined) EOS is established. In order to further analyze and evaluate the improvement in the accuracy of the VPLR EOS, the PVT relationship of O2 (P = 0.01–111.5 GPa and T = 573–4066 K), CO2 (P = 0.42–111.1 GPa, T = 578–5060 K), and CO (P = 0.1–130.2 GPa, T = 591–4286 K) in a wide high temperature and high pressure region was calculated and compared with the calculated values of the original VPL EOS, Virial–Han–Long EOS, and Virial–Wu EOS. The results show that the global accuracy of the VPLR EOS has been significantly improved compared with the other three virial EOSs and that the relative deviation between the calculation results and the reference values can converge in a smaller range at most pressures and temperatures.