Simulation study of a ship's engine behaviour running with a periodically immersed exhaust

Abstract

This paper presents a simulation study of a marine diesel engine equipped with an exhaust system periodically immersed by sea waves. The engine is simulated with an existing, filling and emptying zero-dimensional thermodynamic model. The exhaust system is described with capacitive and inertial elements, and the modelling can take into account water penetration into the exhaust system. An extensive parametric study is conducted to check the influence of exhaust backpressure on engine performances, efficiency, and reliability. A constant water height is first studied and then sinusoidal waves of various periods are analysed, for several engine loads from idle to full load. Results show that the turbine inlet temperature, air/fuel (A/F) ratio, or scavenging process can become critical in some situations. Simulation can help to design an exhaust system that avoids these situations.