Abstract
KEYWORDS – Thermal management, Energy balance, Heat transfer, Cooling circuit, internal combustion engine.
ABSTRACT –
Many studies have shown that in internal combustion engine, only one third of the fuel energy injected in the cylinders is converted to useful work; the other two thirds are either lost with exhaust gas or rejected as heat to the cooling circuit and evacuated to the ambient air flowing through the radiator. The objective of the current study is to define and analyze the energy flow in the engine at different stages of the NEDC cycle.
A 1-D simulation model (GT-Suite) has been built based on several engine tests. This model contains the different components of the coolant circuit: the thermostat, the radiator, the EGR cooler, and the oil cooler. The results from this GT-Suite model were used to define a detailed energy balance of the engine. In order to valorize the energy flow during the NEDC, the energy balance numerical simulations have been carried out at five different times of the NEDC cycle: three in the transient phase, one in the permanent phase and one for the whole cycle.
In present work, the different energy losses via the exhaust line, wall heat losses and auxiliary losses have been represented as percentage of the total fuel energy injected in the system. Then a detailed inspection has been carried out to analyze the wall heat losses; dividing it into different sections: energy flow to the oil circuit, to the cooling circuit and the part used to heat the different engine masses. The study of these different exchanged heats helps to define when and where to apply the different thermal management strategies as heat storage, heat recovery, fluid flow controls between different circuits … An important limitation of this study is that the model does not take into consideration the energy losses of the engine to the ambient air via radiation. Furthermore the cabin heater has been neglected in this study.
The detailed energy balance including different circuits in the engine and at different stages of the NEDC cycle in this paper is a new proposal, in addition to the GT-Suite model built for the coolant and lubricant circuit. Other studies showed only a general energy balance of the engine.
The numerical trials have been made to identify the areas of application of thermal management strategies in different engine circuits by analyzing the different plots of energy balance in the engine.