Closed comb experiments are taken

Closed comb experiments are taken to analyze the phenomena of propellant combustion with or without plasma [7,8]. EGGR of propellants during and after electrical discharges were verified in the experiments. An EGGR coefficient is used to evaluate the effect of electric power [9,10]. Because of EGGR, pressure gradient changes rapidly. The effect of pressure gradient (dp/dt) on burning rate should be considered, especially at a large ratio of input electric Flavopiridol hydrochloride cost to propellant impetus. In this paper, the firing tests using a 30 mm ETC gun are described. A 0D internal ballistic model is used to simulate the ETC launch. A transient burning rate law including the influence of EGGR coefficient by electric power and pressure gradient (dp/dt) is added into the model. The accuracy of the simulated data is analyzed.
30 mm ETC gun firings
Propellant burning rate law The propellant used in the 30 mm ETC gun was tested in an improved closed vessel into which electrical energy was discharged. Fig. 5 shows the pressure gradient (dp/dt) in the closed vessel tests. The pressure gradient (dp/dt) of CPG is much larger than that of the conventional ignition. The phenomenon of EGGR during the electrical discharge was verified. Clive R. Woodley added an EGGR coefficient into the Vieille\'s law to simulate the effect of EGGR in the 155 mm ETC launch [11]. In the 30 mm ETC launch, the peak of pressure gradient (dp/dt) is higher than 1000 MPa/ms, while the peak of pressure gradient (dp/dt) in conventional ignition is just about 500 MPa/ms. The pressure gradient changes rapidly under the condition of plasma ignition. The influence of pressure gradient (dp/dt) on the burning rate of solid propellant should be taken into consideration [12,13]. A semi-empirical equation of propellant burning rate, including the influence of pressure gradient (dp/dt) and EGGR coefficient by electric power, is presented.where u1 is the burning rate coefficient of the solid propellant, n1 is the burning rate exponent, α(t) is time variable function of pressure and flame structure, Pe is the electric power (in MW), βe is the EGGR coefficient (in MW−1).
0D simulation The transferred electric power and the predicted and measured breech pressures are shown in Figs. 6–9, respectively. The predicted breech pressures are simulated by Woodley\'s modified burning rate law and transient burning rate law in Eq. (1). The enhancement of burning rate during the electrical discharge can be simulated with the help of the EGGR coefficient. It can be seen from Figs. 6–9 that the predicted breech pressures are in good agreement with the measured pressures when the EGGR coefficient is equal to 0.005 MW−1. Compared with the breech pressures simulated by Woodley\'s modified burning rate law, the breech pressures simulated by the transient burning rate law are more coincident with the measured breech pressures especially at the end of electrical discharge. In the 30 mm ETC launch, the ratio of the input electric energy to propellant impetus is higher than 0.65, which is much larger than the ratio in Woodley\'s 155 mm ETC launch [14]. A higher ratio leads to a greater effect on the burning rate of propellant. The enhanced burning rates during and after electrical discharge should not just depend on EGGR coefficient by electric power, and the influence of the pressure gradient (dp/dt) should be considered. Table 2 shows the mean square error (MSE) between the simulated and measured breech pressures. The MSE of the pressure simulated by the transient burning rate law is about 1 MPa less than that simulated by Woodley\'s modified burning rate law. In order to analyze the simulation accuracies of the different burning rate laws, the MSEs of simulated breech pressure within 1.2 ms are listed in Table 3. It can be known from Table 3 that the MSE of pressure simulated by the transient burning rate law decreases, while the MSE of the pressure simulated by Woodley\'s modified burning rate law decreases only slightly or increases. It proves that the pressure simulated by the transient burning rate law is more accurate. The projectile muzzle velocity and relative error are listed in Table 4. The simulated projectile muzzle velocity is larger than the measured muzzle velocity. In particular, the simulation accuracy of transient burning rate law is better. Depending on the simulated pressure and projectile muzzle velocity, the simulation accuracy of the transient burning rate law is better than that of Woodley\'s modified burning rate law in the 30 mm ETC launch.