Numerical investigation on the operating characteristics of the cylinder liners of a turbocharged diesel engine

Abstract

The main operating characteristics of cylinder liner include the liner deformation and coolant flow. The insufficient coolant flow can lead to greater deformation of cylinder liner and hence worse engine performance and emissions performance. However, previous works have been done focusing on the characteristics of liner bore deformation and comprehensive coolant flow and the importance of the characteristics of different loads on liner deformation has not been recognized when analyzing cylinder liner. Therefore, the aim of this study is to reveal the characteristics of the coolant flow around cylinder liners and the effect of different loads on liner deformation. A simulation model of a diesel engine was developed to analyze coolant flow characteristics, deformation, and temperature distribution of cylinder liners in steady-state conditions. The effects of thermal stress, bolt preload, firing pressure, and piston side thrust on deformations of cylinder liners were analyzed in various designed conditions based on simulation results. It is found from the analysis results that the temperature of the cylinder liners gradually decreases from the top to the bottom. Meanwhile, the temperature gradient of the upper portion of the cylinder liner is greater than that of the middle portion or the bottom portion due to uneven distributions of the coolant flow in the cooling water jackets of different cylinder liners. In addition, the coolant flow velocity in the valve bridge area is lower than the target value. The expansion and compression deformations of the liner 1 and liner 4 are greater than those of other two liners, and the comprehensive deformation trends of different cylinder liners are similar in various loading conditions. The thermal load has the greatest impact on liner deformation because the total liner deformation contributed by the impacts of different types of loads looks similar to the liner deformation caused by only the thermal load.