Study On Structure Optimization Of Marine Gas Turbine Lobe Ejector

Based on the present situation that the lobed ejector is seldom studied on ships,this paper studies the lobed ejector of marine gas turbine by numerical simulation.The influence of lobe ejector structure parameters on the performance of exhaust ejector system is analyzed,and the excellent performance of marine lobe ejector is optimized by response surface analysis,which provides reference for the improvement of exhaust ejector system in the future.The main conclusions are as follows:The numerical simulation method adopted in this paper is verified by the experimental data of foreign circular cross-section elbow ejector.Aiming at the defect of small mixing gap on the left side of the original model,the position of nozzle was changed and the mixing gap on the left side was increased.By analyzing the flow field at the outlet of lobe ejector,it is found that large-scale secondary circulations will be formed at the outlet of lobe ejector.These secondary circulations are distributed at both sides of each lobe,and their scale is related to the lobe height,which has an important influence on the ejection coefficient of exhaust ejector system.By changing the number of lobes,lobe length,lobe width,lobe retraction angle and lobe expansion angle,the influence of five structural parameters on the performance of lobe ejector is analyzed.The results show that the ejection coefficient,velocity mixing degree and back pressure coefficient are negatively correlated with the number of lobes.Ejection coefficient,velocity mixing degree and back pressure coefficient are positively correlated with lobe length;Ejection coefficient and velocity mixing degree are negatively correlated with lobe width,while back pressure coefficient is positively correlated with lobe width.The ejection coefficient and back pressure coefficient are positively correlated with the lobe retraction angle,while the velocity mixing degree is negatively correlated with the lobe retraction angle.Ejection coefficient and back pressure coefficient are negatively correlated with lobe flare angle,while velocity mixing degree is positively correlated with lobe flare angle.Finally,based on the influence law of single factor change on the performance of lobed ejector,response surface method was used to analyze the lobed ejector by two factors,and the lobed ejector with excellent performance was optimized.Compared with the original model,the injection coefficient of the optimized lobe ejector is increased by about 5%,the back pressure coefficient is increased by about 0.7,and the temperature in the box is reduced by3.98 K under working condition 1.In addition,the ejector coefficient,velocity mixing degree,back pressure coefficient and cooling performance of the optimized lobe ejector are better than those of the necking ejector.