Abstract: The GH₂/GO₂ combustion flow field in a chamber with a single-element typical shear-coaxial injector was numerically simulated firstly.The characteristics of the flow field and the shear-coaxial injector architecture were analyzed to enhance the mixing and decrease the combustion length,some improved designs were made for suiting high flowrate conditions.Numerical analysis and validation experiments were conducted for single-element chambers with these injectors.The improved shear mixing element with high H₂/O₂ velocity ratio and a flared O₂ post tip could maintain a benign heat load environment,and effectively enhance the GH₂/GO₂ mixing suitable for the combustion in the nominal combustor with high injection flowrate.The results directly contribute to the high flow rate gas-gas injector design and the design methodologies in this paper give references for further studies.