LAUSR

Abstract Impinging liquid jets of monomethylhydrazine (MMH) and MON3 (i.e. dinitrogen tetroxide containing 3 wt% NO) were observed with high-speed cameras in order to explore fluid and flame behaviors in the impinging region. At the beginning of the impingement, a portion of the fluids that turned yellow in the impinging region was considered the NO2 and N2O4 vapors or chemical condensate, while the white fogs were regarded mainly as the spreading MMH vapor. Auto-ignition occurred less than 5 ms after impingement, followed by the propagation of orange flames. Due to hypergolicity, orange and blue–white flames were held near the rim of the liquid sheet of the impinging jets. The orange flames tended to exist near the MON3 jets, while the blue–white flames spread on the side of the MMH jets. When atomization was so weak that a long liquid sheet was formed, the MMH and MON3 jets were separated by the orange flames. The atomization performance significantly affected the ignition delay time, as well as combustion efficiency and stability. However, even under strong atomization conditions, the liquid MMH and MON3 jets at a steady state are regarded as the impinging immiscible fluid jets.