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<p>The combustion characteristics of tri-propellant coaxial shear injectors with Air/LOX/ethanol propellants, featuring different outlet geometries, were investigated through hot fire experiments conducted using a combustion air heater. The pressure time evolution and high-speed camera images were acquired for all test cases, enabling comparisons of the spray morphology, ignition process, and flame dynamics across different injector geometries. Analysis of the spray process revealed that the expanded outlet structure introduces an impingement mode within the coaxial shear injector, enhancing liquid-liquid interaction and thereby improving atomization and promoting LOX evaporation. The ignition process of the combustion air heater was found to comprise two distinct stages: formation of a flame core downstream of the liquid jet, followed by upstream propagation of the flame core. Furthermore, grayscale intensity analysis revealed periodic flame variation closely corresponding to the chamber pressure time evolution, indicating that the instantaneous heat release coupled with the chamber pressure fluctuations, thereby amplifying the pressure oscillations. The injector base height and chamfer half-angle were identified as parameters significantly governing ignition and combustion characteristics, with the chamfer half exerting a great influence. Among the configurations investigated, a 15<InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(^{\circ }\)</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mrow /> <mo>∘</mo> </mmultiscripts> </math></EquationSource> </InlineEquation> chamfer half-angle proved most favorable for achieving reliable ignition and maintaining stable combustion.</p>

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Experimental study on the effects of a tri-propellant coaxial injector outlet structure on the combustion characteristics of an air heater

  • 期刊论文

  • 发表日期：

    2026年6月19日

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  • Bo Fan,
  • Chibing Shen,
  • Ke Wang

摘要

The combustion characteristics of tri-propellant coaxial shear injectors with Air/LOX/ethanol propellants, featuring different outlet geometries, were investigated through hot fire experiments conducted using a combustion air heater. The pressure time evolution and high-speed camera images were acquired for all test cases, enabling comparisons of the spray morphology, ignition process, and flame dynamics across different injector geometries. Analysis of the spray process revealed that the expanded outlet structure introduces an impingement mode within the coaxial shear injector, enhancing liquid-liquid interaction and thereby improving atomization and promoting LOX evaporation. The ignition process of the combustion air heater was found to comprise two distinct stages: formation of a flame core downstream of the liquid jet, followed by upstream propagation of the flame core. Furthermore, grayscale intensity analysis revealed periodic flame variation closely corresponding to the chamber pressure time evolution, indicating that the instantaneous heat release coupled with the chamber pressure fluctuations, thereby amplifying the pressure oscillations. The injector base height and chamfer half-angle were identified as parameters significantly governing ignition and combustion characteristics, with the chamfer half exerting a great influence. Among the configurations investigated, a 15 \(^{\circ }\) ∘ chamfer half-angle proved most favorable for achieving reliable ignition and maintaining stable combustion.