*Article* **An Experimental Investigation into Combustion Fitting in a Direct Injection Marine Diesel Engine**

### **Yu Ding \*, Congbiao Sui and Jincheng Li**

College of Power and Energy Engineering, Harbin Engineering University, Harbin 150001, China; suicongbiao@hrbeu.edu.cn (C.S.); heuljc@163.com (J.L.)

**\*** Correspondence: dingyu@hrbeu.edu.cn; Tel.: +86-451-8258-9370

Received: 16 November 2018; Accepted: 30 November 2018; Published: 4 December 2018

**Abstract:** The marine diesel engine combustion process is discontinuous and unsteady, resulting in complicated simulations and applications. When the diesel engine is used in the system integration simulation and investigation, a suitable combustion model has to be developed due to compatibility to the other components in the system. The Seiliger process model uses finite combustion stages to perform the main engine combustion characteristics and using the cycle time scale instead of the crank angle shortens the simulation time. Obtaining the defined Seiliger parameters used to calculate the engine performance such as peak pressure, temperature and work is significant and fitting process has to be carried out to ge<sup>t</sup> the parameters based on experimental investigation. During the combustion fitting, an appropriate mathematics approach is selected for root finding of non-linear multi-variable functions since there is a large amount of used experimental data. A direct injection marine engine test bed is applied for the experimental investigation based on the combustion fitting approach. The results of each cylinder and four-cylinder averaged pressure signals are fitted with the Seiliger process that is shown separately to obtain the Seiliger parameters, and are varied together with these parameters and with engine operating conditions to provide the basis for engine combustion modeling.

**Keywords:** seiliger process model; combustion fitting; marine diesel engine; pressure signal; experimental investigation
