NOWAK Jan BOSMAL Automotive Research and Development Institute Ltd.

Spoluautoři ADAMASZEK Krzysztof

Operating advantages of thermally and mechanically heavy loaded exhaust valves depends on high-temperature creep resistance i.e. simultaneously high resistance on mechanical deformation and corrosion resistance on combustion gases at high temperature. Long-term operating of exhaust valves in cyclic variable thermal and mechanical stresses in combustion gases of petrol fuel, where main oxidizing compounds are oxygen, carbon dioxide and steam-gas. These gases simultaneously cause both, surface corrosion of valves and diffusion processes in thin near-surface layer of valve steel, what in extreme cases can lead to deformation of valves, decrease of tightness level of combustion chamber and finally damaging of the engine. Studies of influence of steel alloying elements on corrosion resistance of valve steel in combustion gases environment of petrol fuel with variable ethanol additives were performed in thermal shock conditions simulating operation of the exhaust valves inside combustion engines with spark ignition. Performed investigations have shown that corrosion resistance of valve steels in combustion gases of combustion engines with spark ignition is decreasing due to increasing of additive of ethanol in petrol fuel.

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