Study on loss characteristic of penetrating exhaust manifold for low-speed two-stroke marine diesel engine

Abstract

The penetrating exhaust system is commonly used in low-speed two-stroke marine diesel engine which has great advantage of fuel economy. However, few study has been carried out on either performance prediction or optimization design on this type of exhaust system. Penetration depth and diffusion angle are the most important configurations of this exhaust system on the loss characteristics, which mean the length of the branch pipe penetrating in the main pipe and the cone angle exhibited by the diffusion of the end of the branch pipe respectively. This paper investigates loss characteristics and flow mechanism of the exhaust manifold of low-speed two-stroke marine diesel engine via experimental and numerical method. Results show the minimum loss is achieved when the penetration depth and diffusion angle are 0.5 and 6°respectively. Furthermore, it is found that the trend of flow loss as ‘decrease-increase’ is the trade-off among the mixing loss due to the shearing of injecting flow and main flow, the momentum loss due to impinging on the bottom of main pipe, and the separation loss in the branch pipe. The investigation of the paper can provide guidance of the configuration optimization and loss modeling of the exhaust manifold of the low-speed two-stroke marine engine.