Anti-Shock Analysis Methods And Simplified Models Of Marine Gas Turbines

With a lot of advantages, gas turbine has now became the main power plant for surface ships in many countries. With the development of underwater weapons, the non-contact explosion shock brought serious threat to gas turbine, therefore the ship’s combat effectiveness is directly related to the gas turbine’s anti-shock ability. In view of the shock problem that the gas turbine suffered, three numerical simulation methods are carried out to study the impact performance of a gas turbine, a method to simplify the model and a program to improve the casing are proposed.At first, this paper discussed the purpose and significance to study numerical anti-shock analysis methods of gas turbine and reviewed the theoretical basis of three numerical methods. Equivalent static method is a simple static analysis, static load is associated with the weight of the equipment itself. DDAM is based on the theory of modal analysis, a multi-degree of freedom system is simplified into multiple single degree of freedom system, and the shock response of the equipment is obtained by combining the modal solutions. Time-domain dynamic analysis is carried out on the equipment on time domain, the dynamic response in each time step is calculated by gradual integration.Taking a certain type of marine gas turbine as the object of study, three anti-shock analysis methods were carried on comparative study. First, the finite element model of the marine gas turbine was built in Femap; and then worked out the finite element analysis for equivalent static, DDAM and time-domain with NX-Nastran; finally, compared the results of the three methods. The results show that the support system is the weak part of the gas turbine under impact load. Then summarized the characteristics of the three methods, and compared their advantages and disadvantages.In order to facilitate the subsequent analysis of the support system, and reduce the computational burden of the support system optimization, the rotor and the casing of the marine gas turbine were simplified into Bernoulli Euler beam and lumped mass model. Then worked out the finite element analysis for modal analysis and anti-shock analysis, the results were compared between the simplified model and the original model. The results show that although lost some modes, the simplified model has little effect on the the result of the support system analysis, what’s more it reduces the DOF significantly, so the simplified model can be used to optimize the support system.In the anti-shock analysis we found that the stress response of the intermediate casing is lesser and the strength reserves is sufficient, so we reduced half of the thickness of the plate to improve the intermediate casing. Then checked the strength and stiffness of the model by sub-model method, the results show that the improved model meets the requirements in terms of strength and stiffness, and reduces the quality of the model effectively.