Combustion Characteristics of GCH_4/GO_2 Coaxial Jet Flames at Low-temperature Injection Conditions in a Model Combustor

摘要

For understanding the combustion stability mechanisms of a methane (CH_4)/oxygen (O_2) bipropellant which is considered as a next-generation liquid rocket propellant under various phases, the fundamental combustion characteristics of gaseous CH_4/O_2 (GCH_4/GO_2) coaxial jet flames at low-temperature injection conditions in a model combustor are experimentally investigated. Using the cryogenic heat exchanger and the model combustor with a single shear coaxial injector and an orifice-type nozzle, the measurement of the combustion stability limits and the flame visualization with OH~* chemiluminescence and direct imaging for GCH_4/GO_2 coaxial jet flames at the low-temperature injection conditions are conducted. The injection temperature of CH_4 and O_2 after passing through the cryogenic heat exchanger ranges from 245 to 288 K depending on the injection conditions. The combustion stability limits of the GCH_4/GO_2 flames at low temperature are substantially reduced compared with those at normal temperature. With decreasing reactant injection temperature, the maximum OH~* intensity of GCH_4/GO_2 flames decreases due to the reduced reactivity and diffusivity of CH_4 and O_2. The measured combustion stability limits and visualization of the GCH_4/GO_2 coaxial jet flames at low-temperature injection conditions provide a useful database to model the combustion of CH_4/O_2 bipropellants under various phases.