*Article* **Numerical Analysis of the Forces on the Components of a Direct Diesel Engine**

### **Dung Viet Nguyen and Vinh Nguyen Duy \***

Modelling and Simulation Institute—Viettel Research and Development Institute, 100000 Hanoi, Vietnam; dungnv98@viettel.com.vn

**\*** Correspondence: vinhnd12@viettel.com.vn; Tel.: +84-985-814-118

Received: 16 April 2018; Accepted: 8 May 2018; Published: 11 May 2018

**Abstract:** This research introduces a method to model the operation of internal combustion engines in order to analyze the forces on the rod, crankshaft, and piston of the test engine. To complete this research, an experiment was conducted to measure the in-cylinder pressure profile. In addition, this research also modelled the friction forces caused by the piston and piston-ring movements inside the cylinder for calculating the net forces experienced by the test engine. The results showed that the net forces change according to the crank angle and reach a maximum value near the top dead center. Consequently, we needed to concentrate on analyzing the stress of the crankshaft, rod, and piston at these positions. The research results are the foundation for optimizing the design of these components and provide a method for extending the operating lifetime of internal combustion engines in real operating experiments.

**Keywords:** internal combustion engine; mechanical stress; fine element method; friction force; in-cylinder pressure
