چكيده به لاتين
Heat release has a significant role in internal combustion engine because optimum heat release can increase engine efficiency and lifetime of engine components. One of the most important issue related to heat transfer in internal combustion engines is investigating amount of heat flux transferred to engine coolant by hot combustion gases. The aim of this study is suggesting a new relationship for determination of heat flux at critical points of 4-cylinder 16-valves turbocharged SI engine. To achieve this goal, quasi-dimensional model is used for analyzing engine heat transfer. In the first step at this method, thermal boundary condition such as temperature and heat transfer coefficient in different periods is obtained by one-dimensional simulation using GT-POWER software. Then three-dimensional thermal solution within conjugated heat transfer (CHT) method is derived by FLUENT 18.1 software for obtaining parameters of coolant flow such as velocity, pressure, temperature, heat transfer coefficient and heat flux to identify the critical points. After validation of velocity and pressure of coolant in cooling passage with experimental results and investigating mesh independency, mass flow rate proportional with the maximum allowable temperature of solid wall along cooling jacket side is calculated. In addition, heat transfer coefficient and heat flux at critical points of engine are determined. It will be shown that parameters of fuel injected to combustion chamber and also compression ratio have important role for evaluating heat flux at different part of engine block and cylinder head in such a way that increasing fuel mass and compression ratio can result in heat flux rise. Finally, a relationship is proposed for estimating heat flux in different points of cylinder head.
Keywords: internal combustion engines, heat transfer, thermal flux relation, fuel flow, compression ratio
