Valve-seats are the most thermally and mechanically loaded components of combustion engines. These loads increase rapidly with the use of LPG and CNG gaseous fuels. Conducted at BOSMAL Automotive Research & Development Institute numerous durability tests of self - and spark ignition combustion engines proved, that the temperature of diesel, gasoline, LPG and CNG exhaust gases measured in the exhaust manifold reaches in case of CNG around 1223 K. The valve seats fueled with LPG are usually manufactured from high-alloyed sintered powders. Attempts of application of same valve seats to the engines fueled with CNG (as engines fueled with LPG) were finished unsuccessfully. The aim of the study was to investigate the effect of molybdenum disulfide and open porosity saturated with Cu on the durability of the valve seat faces in the operating conditions of two-cylinder engine type 0.9 SGE TC80 CNG fueled with natural gas. Durability test was conducted according to the methodology of BOSMAL procedure. There were measuring (among others parameters) the power, torque and rotation speed, also the exhaust gases temperature and the hourly fuel consumption. Studies had shown a strong influence of molybdenum disulfide and open porosity on the durability of tested valve seats in engine fueled with compressed natural gas (CNG).Keywords: sintered valve seat, combustion engine, CNG
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