DETAILED ANALYSIS OF THE ENERGY EFFICIENCY OF AN INCOMPLETE THERMODYNAMIC CYCLE WITH DETONATION COMBUSTION

A new approach is suggested to assessing the efficiency of a detonation jet engine, which is determined as a ratio of the combustion products′ work in the process of their isentropic expansion to the heat of combustion. A comparison is made of the energy efficiency in constant-volume combustion and in a detonation wave with a subsequent release of detonation products into the surrounding environment. The calculation of the efficiency of detonation combustion is performed on the basis of an exact solution of a self-similar problem of propagation of infinitely thin Chapman– Jouguet detonation in a tube with an end wall. It is shown that the absolute advantage of Chapman–Jouguet detonation which has been established for a full cycle is achieved due to transformation of the kinetic energy of the detonation products into useful work and that in the case of an incomplete thermodynamic cycle, detonation combustion turns out less efficient than constant-volume combustion. An analysis has been made of a detonation cycle compared to Otto and Brayton cycles at a limited degree of pressure rise, maximum temperatures and indicated efficiency and arbitrary independent energy parameters (amount of heat supplied during combustion). It has been established that at the adopted limitations, the detonation cycle does not have an absolute advantage over the Otto and Brayton cycles. The detonation cycle surpasses the said cycles in the values of the thermal efficiency, maximum pressure and the criterion of irreversibility; in terms of the value of specific volume work (work-to-volume ratio) the detonation cycle surpasses the Brayton cycle but is outperformed by the Otto cycle

Author:  Yu. V. Tunik, M. S. Assad
Keywords:  energy efficiency, detonation adiabat, Chapman–Jouguet detonation, Poisson adiabat, self-similar solution, constant-volume combustion, isentropic expansion, Otto and Brayton cycles, thermal efficiency
Page:  920