Modelling and analysis of radial thermal stresses and temperature field in diesel engine valves with and without air cavity
A theoretical investigation has been undertaken to study operating temperatures, heat fluxes and radial thermal stresses in the valves of a modern diesel engine with and without air-cavity. Temperatures, heat fluxes and radial thermal stresses were measured theoretically for both cases under all four thermal loading conditions. By creating an air cavity inside the valves stem, it acts as an insulating medium and prevents the heat flow, hence the need of providing insulation coating on valves is minimized. The main motive of this is to reduce the weight of engine and cost associated with thermal coating. Results observed in the engine valves revealed that after creating an optimized air cavity in the valve, thermal stresses and temperatures at all nodal points decreases slightly. The weight of the valve decreased up to 11% without losing its strength. In addition to heat transferred by convection and radiation from combustion gases, the temperature and heat flux distributions are considerably affected by heat conduction from valve seat. The temperature field, heat transfer rate and thermal stresses were investigated with numerical simulation models using FORTRAN FE (finite element) software.
Keywords: combustion chamber, temperatures field, diesel engine valve, finite elements