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This paper presents an experimental study of the emission characteristics of a small Spark-Ignited, LPG engine. A single cylinder, four-stroke, water-cooled, 125cc SI engine for motorcycle is modified for using LPG fuel. The power output of LPG is above 95% power output of gasoline. The emission characteristics of LPG are compared with the gasoline. The test result shows that LPG for small SI engine will help to reduce the emission level of motorcycles. The HC and CO emission level can be reduced greatly, but NOx emissions are increased. The emission of motorcycle using LPG shows the potential to meet the more strict regulation.

An air-cooled, four-stroke, 125 cc electronic gasoline fuel injection SI engine for motorcycles is altered to burn ethanol fuel. The effects of nozzle orifice size, fuel injection duration, spark timing and the excess air/ fuel ratio on engine power output, fuel and energy consumptions and engine exhaust emission levels are studied on an engine test bed. The results show that the maximum engine power output is increased by 5.4% and the maximum torque output is increased by 1.9% with the ethanol fuel in comparison with the baseline. At full load and 7000 r/min, HC emission is decreased by 38% and CO emission is decreased 46% on average over the whole engine speed range. However, NOx levels are increased to meet the maximum power output. The experiments of the spark timing show that the levels of HC and NOx emission are decreased markedly by the delay of spark timing.

The work of this paper aimed at investigating the cyclic variations of argon power cycle engine with fuel of hydrogen at lean burn operating conditions. The engine had been modified based on a 0.402 L, single-cylinder diesel engine into spark ignition engine with a port fuel injection system. The influencing factors on the cyclic variations, such as ignition timing, engine speed and compression ratio, were tested in this study. In all tests, the throttle opened at 0%, and the excess oxygen coefficient was maintained at 2.3. The results showed that as the ignition timing retards, CoVPmax and CoV(dp/dφ)max of argon power cycle engine increased, while CoVIMEP decreased firstly and increased afterward. And there is an ignition timing to make the lowest CoVIMEP, which is not consistent with MBT.

In order to improve the performance of low temperature combustion of diesel engines to achieve ultra-low emissions and load condition expansions, exhaust gas recirculation (EGR) stratification in the cylinder was proposed to further intensify local EGR concentration and reduce the amount of EGR to acquire high average oxygen concentration within cylinder. In this study, the intake/exhaust port and combustion chamber models were explored by CFD software on a four-valve HD diesel engine, and fresh air and EGR respectively replaced by O2 and CO2 were introduced with division and timing intake strategies during the intake process for stratification optimization.