Gas-centered swirl coaxial injectors spray with variable inner wall structures
The spray characteristics of gas-centered swirl coaxial injectors in three structures of the gas injector,namely,the smooth inner wall(A),inner wall with concave cavities(B),and inner wall with projections(C),were examined by experiments.At the same time,in order to analyze the change of flow field caused by the change of the inner wall structures of the gas injectors,the pure gas flow field was simulated without considering the liquid phase.The results demonstrated that the spray angles of the three injectors increased with the gas mass flow rate,but decreased with the liquid mass flow rate.Adding a concave cavity to the inner wall of gas injector had little effect on spray angle,breakup length and self-pulsation frequency of the injector.But inner wall with projections of gas injector had a significant effect on spray characteristics.Under the same working conditions,the inner wall with projections could enhance the ejection effect of the gas injector outlet,decrease the spray angle,and the stronger gas-liquid interaction could reduce the breakup length.When the self-pulsation occurred,the inner wall with projections also increased the frequency of self-pulsation.The self-pulsation frequency of the three injectors increased with gas mass flow rate,and the induction and maintenance mechanisms of the self-pulsation of the three injectors were analyzed.The effects of different concave cavity sizes and projection sizes on spray characteristics were investigated through experiments.For injector B,the spray angle,breakup length and self-pulsation of the spray were almost the same.The spray angle and breakup length of injector C were smaller than those of injector B,and decreased with the size of projection,while the self-pulsation frequency was larger than that of injector B,and increased with the size of projection.
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