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Considering the eccentricity and deformation of the plunger, a lubrication model of laser-textured plunger pair was established to research friction-and-wear performance of typical surface texture on the plunger under diesel and methanol lubrication. The calculation results show that for the non-textured plunger, the oil film thickness and fluid friction under methanol lubrication are lower than diesel lubrication, and the asperity friction was greater than diesel lubrication, indicating that methanol may deteriorate the lubrication performance of the plunger surface. After texturing the plunger, the oil film thickness and fluid friction during methanol lubrication are greater than the non-textured scheme, and the asperity friction is lower than the non-textured scheme, which means that the surface texture has the potential to improve the lubrication performance of the plunger. The friction and wear tests results indicate that the average friction coefficient of the textured plunger is reduced by 3.4 ∼ 6.2 % compared with the non-textured plunger in methanol lubrication. The lubrication performance of the textured plunger during methanol lubrication reaches the level of the non-textured plunger in diesel lubrication. After the wear test, the surface wear depth of the textured plunger is reduced by 16.2 % compared with the non-textured plunger in methanol lubrication condition.

Based on a small non-road diesel engine, internal exhaust gas recirculation (IEGR) was realized by the exhaust valve re-opening (2EVO). The influences of IEGR on combustion and emission performance were analyzed. The results showed that in-cylinder pressure peak decreased, the start of heat release was delayed by 0.5 oCA and the heat release rate peak was reduced after the introduction of IEGR. Furthermore, the average temperature of combustion flame was reduced, centering between 1900 and 2100 K. That was beneficial to curbed nitrogen oxides (NOX) emissions. The average value for KL factor was obviously increased within the entire range of combustion, which resulting in an increase in soot emission. In terms of emission characteristics, NOX emission was significantly reduced under the original injection timing but soot emission was increased slightly. Subsequently, the start of injection (SOI) were adjusted based on IEGR and two fuel injection control strategies were formulated from the perspective of reducing pollutant emissions and fuel consumption: Strategy 1 keeping BSFC consistent with the original engine, the NOX+HC weighted emission was reduced by 17.6 %; Strategy 2 keeping NOX+HC emissions consistent with the original engine, BSFC and CO were reduced by 10 % and 20 % respectively and Soot emission was slightly increased.