Research On The Ejection Flow In Marine Gas Turbine Exhaust System

Infrared suppressor is widely used in modern design of marine engine exhaust system in order to reduce the infrared radiation of marine gas turbine exhaust and improve the survivability of ships.A typical infrared suppressor is usually made up of a mixer and a series of diffusers. The cold flow which ejected through the slots of diffusers increases the second flow and also cools down the diffusers by forming a cooling film on the surface of diffusers. Previous studies focused on the main structure and characteristics of a ship exhaust system, but paid less attention on the cooling film on the diffusers. This paper focus on the ejection flow in marine gas turbine exhaust system. The study is carried out by means of both experimental and numerical method.CFD calculation had been carried out to study the flow structure and characteristics of a 2-D ejection flow in ambient conditions. The ejection ratio and reattachment length had been discussed. Three factors which affect the ejection process had been considered: the expansion ratio, the Reynolds number and the structure of the ejection slot. A wind tunnel was built up to study the ejection flow by means of Particle Image Velocimetry(PIV). The experimental results show that the computation had been done is reliable. This work provides detailed information for the ejection flow and it will be useful for further design of a ship exhaust system.Also, numerical computation and experimental test has been carried out to study the performance of marine exhaust system. The results show the flow structure in the marine exhaust system model and the flow ejected in slots of diffusers. The experiment reflects the temperature and pressure on the outlet of the exhaust system as well as the infrared characteristics of the exhaust system. The impact of the distance between the nozzle and the mixer was tested. Different nozzles were also used. In addition, the influence of the slot ejection flow on the diffusers has also been discussed.