The large production of the single diesel engine is the characteristic of China internal combustion engine industry. But the environmental pollution is more serious and the large quantity of the single diesel engine is one of the main pollution sources. The exhaust after-treatment is a good measure of the diesel engine to reduce the emissions. In order to improve the emission performance of single cylinder diesel engine through external purification, the one-body purification muffler was designed. The functions of the one-body purification muffler were noise elimination and emission purification. The internal velocity uniformity was one of the most important aspects of the structure design of the one-body purification muffler. Numerical simulation and performance test were adopted in the structure design and performance optimization of the one-body purification muffler to optimize the catalytic performance, acoustic performance, aerodynamic performance and structural performance. Numerical simulation was used to analyze the internal airflow velocity field of one-body purification muffler to optimize the internal structure. The reasonable internal structure of the one-body purification muffler could effectively improve the catalytic conversion efficiency and the service life. Performance test was used to analyze the catalytic performance, acoustic performance and aerodynamic performance of the one-body purification muffler. According to the results of the performance test, the internal structure of the one-body purification muffler was improved. The results of overall performance test showed that the test prototype with the third scheme of one-body purification muffler had the advantages of low power loss, low flow resistance and high noise elimination. The power loss of the one-body purification muffler based on the third scheme was 1.18%, which was reduced by 28.5% compared with the original muffler. The flow resistance of one-body purification muffler based on the third scheme was lower than the original muffler. With the third scheme of one-body purification muffler, the engine noise was 108.6 dB, which remained the same compared with the original muffler. The results of overall emission test showed that the test prototype with the third scheme of one-body purification muffler had the advantage of low exhaust emission value. The measured values of carbon monoxide (CO), hydrocarbon (HC) and particulate matter (PM) were 0.94, 0.46 and 0.4 g/kW·h respectively, which were reduced by 85.4%, 70.5% and 28.6% respectively, compared with the original muffler. But the measured value of nitrogen oxide (NOx) remained the same compared with the original muffler. Besides, the measured values of CO, HC and PM of the third scheme of one-body purification muffler were reduced by 21.0%, 25.8% and 7.0% respectively compared with the second scheme of one-body purification muffler because of the optimizations of the aerodynamic performance and the structural performance. After the endurance test, the exhaust emission values of the third scheme of one-body purification muffler still met the third phase limits. The third scheme of one-body purification muffler can improve the emission performance of single cylinder diesel engine through external purification effectively and optimize the catalytic performance, the acoustic performance, the aerodynamic performance and the structural performance. The research provides theoretical and technical references for the design of the one-body purification muffler of the single diesel engine.%为了通过机外净化的方式降低柴油机排放，基于单缸柴油机的工作特点，融合一体式净化消声器的设计要求，研制了一种单缸柴油机用一体式净化消声器。通过数值模拟与试验相结合的方法，对设计的一体式净化消声器的催化性能、声学性能、空气动力性能以及结构性能展开研究，提高催化器转化效率和使用寿命，同时满足消声作用。整机性能试验表明：安装优化后的一体式净化消声器，整机噪声略小于原机消声器，整机八工况排放CO、HC、PM分别为0.94、0.46、0.40 g/kW·h，相比于仅采用机内净化的样机分别降低了85.4%，70.5%，28.6%，劣化试验后柴油机排放满足非道路柴油机国Ⅲ要求；一体式净化消声器采用优化结构，与原结构相比，由于排气气流均匀流经催化器，CO、HC和PM的转化效率分别提高了21.0%、25.8%和7.0%。该研究可为单缸柴油机的机外净化研究提供参考。
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