Theoretical and Experimental Investigation of Influence of Mixture Ratio on Hydrogen-Oxygen Detonation Characteristics

Abstract

The Detonation Wave Ignition (DWI) technique practiced its adaptation to the large liquid rocket engines which have multiple chambers or a large chamber with multiple combustion regions. It is an important step to describe the characteristics of DWI technique for engineering application. Theoretical analysis has been made in order to obtain the rule of mixture ratio influencing on detonation characteristics of GH2/GO2. Assumed that the detonation species were in chemical equilibrium on the C-J detonation wave surface, chemical equilibrium constant method was used to calculate the detonation species, and the thermodynamic parameters and the characteristic parameters of detonation wave were gained. Experimental system has been set up and more than 70 experiments have been carried out under different mixture condition. The pressure and the temperature of detonation wave have been obtained and the average velocity of detonation propagation between the test locations has been calculated. The influence of mixture ratio on detonation wave propagation velocity and detonation wave propagation Mach number has been studied and compared with each other under different mass flow rate condition. The theoretical results agree well with the experimental results. I. Introduction ELIABLE simultaneous ignition of the large liquid rocket engines which have multiple chambers or a large chamber with multiple combustion regions is quite important to the startup of these engines. The commonly used in liquid rocket engines methods are chemical, pyrotechnical and electrical ignitions. Among the various ignition means for these engines, the Detonation Wave Ignition (DWI) system appears to be the most practical one. The DWI technique is a novel concept of rocket ignition system devised for the simultaneous ignition of multiple combustion chambers by delivering detonation waves through several detonation tubes. Shortly after the premixed gaseous propellants were excited by a weak spark in the premix chamber, the deflagration flame transited to detonation wave in the detonation tube. The detonation wave propagated with high temperature and high pressure along the detonation tubes, which were filled with gaseous propellants beforehand, and arrived at multiple ignition locations. In 1970s, American Rocketdyne Corporation performed more than 100 experiments and verified the feasibility of detonation wave ignition 1 . Ten combustion chamber units were ignited with DWI system. In 1990s, American Lewis Research Center ignited a simulation combustion chamber using DWI igniter 2 . The conclusions show that the detonation wave ignition is a simple and safe system and has applicability to multiple-chamber rocket engines. In this paper, theoretical analysis has been made in order to obtain the rule of mixture ratio influencing on detonation characteristics of GH2/GO2. Assumed that the detonation species were in chemical equilibrium on the CJ detonation wave surface, chemical equilibrium constant method was used to calculate the detonation species, and the thermodynamic parameters and the characteristic parameters of detonation wave were gained. Keeping mixture pressure and temperature as constant, theoretical calculation results show that, when the mixture ratio is less than the chemical equilibrium ratio, the temperature and pressure of detonation, and the Mach number (the detonation wave propagation velocity versus the sonic velocity of unburned gases) increase with mixture ratio. And when the mixture ratio is larger than the chemical equilibrium ratio, they decrease with mixture ratio. It is also showed that the propagation velocity of detonation decreases while the mixture ratio increases.