Sodium cooling efficiency in hollow valves for heavy duty engines
As a consequence of the continuous evolution of engines, where their performance is improving day by day and the use of alternative fuels is being adopted by many engine manufacturers, thermal working conditions of the exhaust valves is getting critical within the last years. The adjustments needed are diverse. In order to better resist the higher temperature levels of the exhaust gases the current development ranges from improvement on the cooling concept for the overall system over new materials for valves set components up to the upgrade of the exhaust manifold material. Change on the design of several valvetrain components due to the increased thermal loads is a logical consequence of this technical evolution process. Hollow exhaust valves filled with Sodium (Na) are a known technology that is widely used in passenger car engines to improve its thermal behavior and avoid the need of changing to expensive materials (Ni-base alloys).