Research On The Performance Of Exhaust Ejector With Lobed Nozzle For Marine Gas Turbine

The function of the gas turbine enclosure is to protect and fix the gas turbine and its auxiliary equipment,while preventing the heat generated by the gas turbine from affecting the external environment of the enclosure,ensuring the normal operation of auxiliary equipment inside the enclosure.Therefore,the cooling performance of the gas turbine enclosure directly affects the normal operation of ship gas turbines and the reliability of auxiliary equipment,making it a key aspect in the design of naval power systems.This thesis is based on fluid dynamics simulation methods to design and optimize the gas turbine enclosure for ships,aiming to find a configuration with optimal ejection performance and cooling performance.The specific research contents are as follows:(1)This thesis proposes multi-objective evaluation indicators for the thermal performance of gas turbine enclosures,which includes four ejection performance evaluation indicators and one temperature distribution evaluation indicator.Based on the configuration of a certain type of enclosure,two square-to-circle ejectors and one lobe nozzle ejector are designed,and the ejection performance of each structure is compared and analyzed,revealing the ejection mechanisms under different structures.Furthermore,the impact of six factors on various evaluation indicators is further explored,including the number of lobes,width,expansion angle,diameter and height of the mixing tube,and the spacing between the lobe nozzle ejector outlet and the mixing tube inlet.(2)This thesis designed an orthogonal experiment with four factors,namely,lobe width,lobe expansion angle,mixing tube diameter,and spacing,as the study variables,and four levels of each factor were taken to study the sensitivity of the parameters under various combinations.The impact of each factor on the performance indicators of the enclosure assembly varies.The largest impact on the entrainment coefficient and velocity non-uniformity is the diameter D of the mixing tube,and the largest impact on the pressure loss coefficient and temperature non-uniformity is the expansion angleαof the lobed nozzle.(3)Based on the orthogonal experiment results,the entropy value method was used to assign weights to each evaluation indicator,and the weight coefficients w_j of the four evaluation indicators,namely,entrainment coefficient,pressure loss coefficient,velocity non-uniformity and temperature non-uniformity,were derived,among which the entrainment coefficient had the largest weight and the temperature non-uniformity had the smallest weight.Furthermore,the TOPSIS method is proposed to sort the results of each experiment,and Case10 is indicated as the optimal case,and the numerical simulation results are used to verify that the internal temperature of the gas turbine enclosure corresponding to the optimal case meets the design requirements.