An Experimental Survey on the Emissions Characteristics of Non-Road Small S.I. Engines in China 2003-32-0036
There are not emission legislations for non-road small spark ignition engines in China so far. To formulate an appropriate one, an experimental investigation was firstly carried out in order to point out the state of the art of the exhaust emissions of non-road small spark ignition engines in China.
17 different engines were selected as representative of the most common non-road small spark ignition engines in China, including lawn mowers, generator and chain saws. Fourteen engines are four stroke and three engines are two stroke. All of them were not equipped with catalytic converter.
After a run-in period, exhaust emissions such as HC, CO, CO2, NOX were measured according to different test cycles. Besides these, exhaust temperature, A/F in the exhaust and fuel consumption were also measured. The exhaust analyzers are HFID for HC, CLD for NOX, NDIR for CO and CO2. The specific exhaust emissions obtained under different test cycles were then compared with the EPA phase 2 limitations. It was concluded that non-handheld engines had more difficulty in complying with the corresponding limitations than handheld engines. For non-handheld engines, HC+NOX emission was the main problem.
Finally, a four-stroke non-handheld engine was selected to do further research, to reduce its higher HC+NOX emission, different measures such as carburetor tuning, second air supply and catalytic converter were tried and favorable results were achieved. The specific exhaust emissions of CO, HC+NOX were reduced by 49.2% and 46.6% respectively.