Application Research And Numerical Simulation Of Thermal Barrier Coatings In Cylinder Liner

Limited energy supply and stricter laws on tail gas all raise a new high demand forcombustion engineering. Recently, a new kind of theory Homogeneous ChargeCompression Ignition, which is HCCI in short, has become a hot study topic. Ithighly improves the efficiency of fuel, and meanwhile lower the emission of NOx andSOOT. However, with the low temperature inside the cylinder stator, unburnedhydrocarbons (UBHC) and CO increase at the same time especially lower theefficiency of traditional combustion engine. In order to improve the efficiency ofcombustion engine and bring less heat loss, it is necessary to develop a low heat lossengine.Low heat rejection diesel is an engine applying heat isolating technique to themain parts of combustion chamber. In the thermal insulation material selection, withhigh hardness, resistance to corrosion, high temperature, oxidation and friction andlow thermal conductivity of ceramic materials, it is feasible to apply ceramic materialin the production of overall ceramic parts to replace the traditional internalcombustion engine parts. Still, there is a long way to go to apply this kind of parts inmotor engines. Therefore, it is a promising method to make ceramic coating (alsoknown as thermal barrier coating) on the surface of the mainly heated component.The subject of this paper is the cylinder cover of internal combustion engine. Theresearch is divided into two parts: the first part is about calculation on temperaturefield and stress field of the engine cylinder with thermal barrier coatings throughnumerical simulation software ANSYS12.0. we get the following conclusion:(1).The highest temperature inside the cylinder is higher with a coating, and thethicker the coating,the higher the temperature;(2).The temperature gradient along with wall thickness is bigger with a coating,and the thicker the coating, the greater the temperature gradient;(3).Due to the thermal inertia of materials, the temperature of the cylinder withvariation of the gas temperature is not timely;(4).The maximum equivalent thermal stress and average equivalent thermalstress between BC and substrate as well as TBC and BC increase with the increase ofthe coating thickness.On the second part, with the appliance of thermal spraying technology, thermal barrier coating, which combines CoNiCrAlY for bonding layer and ZrO2+8wt%Y2O3for surface ceramic layers, is made on2A70aluminum alloy. The thermal shock test isfollowed, to see the resistance to thermal shock. Then the position of crack and thecause of formation is analyzed, we get the following conclusion:(1).Crack coating appears in vertical and horizontal. Vertical cracks begin in theceramic layer surface, and with continuing thermal shock, the crack gradually expand,and eventually extended to aluminum substrate; while transverse crack appears insideTBC and even the joint surface between the BC and substrate;(2).The formation and extension of thermal shock crack is mainly in the adhesivelayer and aluminum substrate interface, and radial thermal stress and high temperatureoxidation is the main reason of the crack.