Thermal Damage of Intake Valves in ICE with Variable Timing

Abstract

The article provides the study on causes of damage to ICE intake valves, in the course of which the intake valve heads have been overheated and deformed as a result of material creep. On the example of the failure detected in the analysed engine, it has been estab-lished that the traditionally known reasons such as the combustion process failure cannot cause the damage described. For the purpose of determining the real causes of damage to the intake valves the authors simulated the thermal state of the intake valve in the heating-cooling conditions with the impact of gas in the cylinder and the impact of air in the intake pipe as well as the contact heat exchange with the seat with regard to thermal conductivity along the stem. The calculations have shown that with the increase of rotation frequency the failure of the control system that causes the engine to run at high rotation frequencies with a small intake valve lift leads to the temperature increase higher than it is recom-mended for the materials used, which causes the described overheating. Based on the conducted research the authors have developed recommendations for improving the reli-ability of the intake valves performance in the ICEs with variable valve timing.