Thermal Characteristics Investigation of the Internal Combustion Engine Cooling-Combustion System Using Thermal Boundary Dynamic Coupling Method and Experimental Verification

Junhong Zhang,Zhexuan Xu,Tianshu Xu,Jingchao Wang,Zefeng Lin,Jiewei Lin

doi:10.3390/en11082127

Abstract

The engine cooling system must be able to match up with the stable operating conditions so as to guarantee the engine performance. On the working cycle level, however, the dynamic thermo-state of engines has not been considered in the cooling strategy. Besides, the frequent over-cooling boiling inside the gallery changes the cooling capacity constantly. It is necessary to study the coupling effect caused by the interaction of cooling flow and in-cylinder combustion so as to provide details of the dynamic control of cooling systems. To this end, this study develops a coupled modeling scheme of the cooling process considering the interaction of combustion and coolant flow. The global reaction mechanism is used for the combustion process and the multiphase flow method is employed to simulate the coolant flow considering the wall boiling and the interphase forces. The two sub-models exchange information of in-cylinder temperature, heat transfer coefficient, and wall temperature to achieve the coupled computation. The proposed modeling process is verified through the measured diesel engine power, in-cylinder pressure, and fire surface temperature of cylinder head. Then the effects of different cooling conditions on the cyclic engine performances are analyzed and discussed.

Highlights

Concerning the energy and environment performances of diesel engines, efficiency is an increasingly important issue since only 30% to 40% of the fuel energy is transformed into mechanical work
In-cylinder temperature, in-cylinder pressure, average wall temperature, temperature, wall heat loss, gas phase distribution of coolant and engine work are used to analyze wall heat loss, gas phase distribution of coolant and engine work are used to analyze the effects of the the effects of the rated flow of coolant and the inlet temperature on engine thermal characteristics
It is shown the heat transfer coefficient drawn in a complete cycle of 720◦ CA (Figure 7)

Summary

Introduction

Concerning the energy and environment performances of diesel engines, efficiency is an increasingly important issue since only 30% to 40% of the fuel energy is transformed into mechanical work. As a main part of energy loss, the cooling process affects the combustion by means of the cylinder wall temperature. The cooling strategy is correlated to the engine speed, which would result in overcooling effects in operation [1]. A variable-speed water pump with proper coolant flow control was adopted to increase the fuel economy by about 2.5%. Based on thermal management modeling, Kang [3] designed a double loop coolant circuit for the cylinder head and engine block, which indicates 30% coolant flow rate of the basic system can satisfy the thermal requirement of the target engine. Wang [4] presented a nonlinear adaptive control strategy for a radiator fan matrix for transient engine temperature tracking and the power consumption was reduced greatly.

Methods

Results

Conclusion