Abstract
ABSTRACTReducing motorcycle exhaust emissions to improve air quality is important in Asia, due to the large number of motorcycles. This study describes and proposes a lean-burn system for reducing pollutant emissions and improving motorcycle engine performance. The lean-burn system, called semi-direct injection (SDI), is comprised of high-swirl charge, injection during intake-valve opening, and liquefied petroleum gas (LPG) injection. A conventional motorcycle engine with port fuel injection (PFI) and spark ignition (SI) was retrofitted by designing a new intake port with a controllable plate to enhance the swirl of intake flow. The swirl ratio was increased to 3.4, enhancing the turbulence of air flow inside the combustion chamber, and the lean limit was extended to 1.7 of relative air/fuel ratio (lambda). The engine was tested at a low-load region which includes most operating points of the ECE-40 driving cycle. A complete engine performance map was produced and a comparison was undertaken between the new design and regular gasoline engines. The results show that brake-specific energy consumption (BSEC) decreased by 19.2%. Brake-specific exhaust emissions of CO2, NOx and CO were decreased by 27%, 47% and 94%, respectively. HC emissions were increased by 4.5%.
Highlights
Traffic exhaust emissions are significant sources of air pollution in the world and may threaten human health and cause global warming effect
The results show that the hydrocarbon emissions (HC), nitrogen oxides (NOx) and carbon monoxide (CO) emission could be reduced by 30%, 98% and 90%, respectively, and achieve EURO 4 without the aid of a reducing catalyst
Lower CO emission may be due to high turbulence intensities in semi-direct injection (SDI) engine combustion, so CO interacts with O2 or OH to become CO2
Summary
Traffic exhaust emissions are significant sources of air pollution in the world and may threaten human health and cause global warming effect. Governments are compelled to minimize motor-vehicle pollution problems with more stringent emission standards for reducing pollution-related chemicals and improving air quality. Previous research shows that three-way catalytic converter used in spark ignition (SI) engines could reduce most exhaust pollution, such as HC, CO and NOx, towards achieving exhaust standards (Lou et al, 2003; Kim et al, 2011). Converters are expensive to apply in motorcycles and would not reduce carbon dioxide (CO2), a major cause of global warming effect. It may be more acceptable, especially cost wise, to address the problem in the design and manufacture of motorcycles
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