Introduction to ?To the Question of Energy Use of Detonation Combustion? By Ya. B. Zel?dovich

Abstract

Y A. B. Zel'dovich (1914A. B. Zel'dovich ( -1987 made numerous contributions 1 to the theory of detonation, beginning with his very wellknown and widely translated article 2 on detonation structure that first introduced the standard Zel'dovich-von Neumann-Döring (ZND) model of shock-induced combustion. Even at that early stage of detonation research, Zel'dovich was also considering the application of detonations to propulsion and power engineering. He published these ideas in another paper 3 that has been virtually unknown in the West and has apparently remained untranslated until now. We are indebted to Sergey Frolov of the N. N. Semenov Institute of Chemical Physics for first bringing this article to our attention. We believe that the focus of this paper, which is the application of detonation waves to power generation and propulsion, is very relevant to the current activity on pulse detonation engines. In particular, Zel'dovich was apparently the first researcher to consider the questions of the relative efficiency of various combustion modes, the role of entropy production in jet propulsion, and the distinction between unsteady and steady modes of detonation in power engineering and propulsion applications. Even 60 years later, we believe that his results are relevant and can be of value in modern discussions on thermodynamic cycle analysis of detonation waves for propulsion. 4 For these reasons, we have arranged for the paper to be translated and suggested that it be published by the Journal of Propulsion and Power.The paper is clearly written, and there is no need for extensive commentary, so we only sketch some connections with contemporary work. Sections 1-3 are concerned with the correct computation of the energy budget in an unsteady cyclic process and the thermodynamic efficiency. Zel'dovich recognizes that one has to account for the work necessary to sustain the detonation wave (through a piston, for example) when calculating the work that can be done by the products. This idea was also independently developed by Jacobs 5 and later Fickett and Davis, 6 although they were concerned primarily with high explosives. More recently, we have revisited this idea 7 and carried out computations for mixtures and conditions relevant to pulse-detonation-engine operation. To our knowledge, Zel'dovich was the first researcher to conduct a thermodynamic analysis of a cycle involving a detonation. His conclusion that the efficiency of this cycle is always slightly larger than that of a cycle using constant-volume combustion (Humphrey cycle) has been confirmed many times since.8−10 Zel'dovich's formal results for the thermal efficiency are identical to the results of recent studies. 7,9 The specific numerical values given in the main body are, as Zel'dovich recognized, rough estimates and deviate substantially from detailed computations based on realistic thermodynamic properties. Despite the incorrect values for thermodynamic states, his final results regarding the differences in cycle efficiency are quantitatively c...