Abstract: This study addresses the issue of difficult or impossible starts in small agricultural gasoline engines due to abnormal combustion within the cylinder. Utilizing a self‑constructed experimental platform for small agricultural gasoline engines, the research investigates the effects of excessively high fuel‑air mixture concentration, overly lean fuel‑air mixture, and cylinder leakage on the starting current and waveform changes under standard conditions. The results demonstrate a significant correlation between the fuel mixture concentration, cylinder leakage, and the waveform of the starting current during the ignition process. An increase in fuel injection volume leads to a higher fuel‑air mixture concentration, significantly reducing the starting current duration of the test gasoline engines by 21.2% to 68.7%. During the steady‑state phase of cranking, the starting current value increases by 14.9% to 21.7%. Conversely, as the intake air volume increases and the fuel‑air mixture concentration decreases, the starting current duration of the test gasoline engines increases by 46.8% and 144.9%, leading to a failure to start. Additionally, an increase in cylinder leakage results in an extension of the starting current duration by 9.6%, 17.5%, and 41.9%, culminating in a failure to start, and the starting current value during the steady‑state phase of cranking is reduced by 3 A to 5 A compared to normal starts.

Key words: agricultural gasoline engine, starting difficulty, starting current, cylinder combustion

摘要： 针对农用小型汽油机缸内燃烧异常导致起动困难甚至无法起动的问题，基于自行搭建的农用小型汽油机试验平台，研究缸内燃油混合气浓度过高、燃油混合气浓度过稀和气缸漏气在标准条件下对农用小型汽油机启动电流的影响和波形变化分析。结果表明：试验汽油机起动过程燃油混合气浓度、气缸漏气量与启动电流波形具有显著相关性。喷油量的增加使燃油混合气浓度增高，试验汽油机启动电流时长显著缩短，缩短幅度为21.2%~68.7%，在盘车稳态阶段，启动电流数值增大14.9%~21.7%；相反，起动阶段调节阻风门增加进气量，燃油混合气浓度随进气量的增加而降低，试验汽油机启动电流时长逐渐增加，分别增加46.8%、144.9%至启动失败。同时，逐渐增加试验汽油机气缸漏气量，试验汽油机启动电流时长增加，分别增加9.6%、17.5%、41.9%至启动失败，盘车稳态阶段的启动电流数值较正常起动减小3~5 A。

关键词: 农用汽油机, 起动困难, 启动电流, 缸内燃烧