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To properly respond to demands to reduce national energy consumption and meet greenhouse gas emission targets based on environment policy, the Ministry of Trade, Industry, and Energy of Korea formed a research consortium consisting of government agencies and academic and research institutions to establish the first fuel efficiency standards for medium- and heavy-duty (MHD) commercial vehicles. The standards are expected to be introduced in 2017 as Phase 1 of the plan and will regulate trucks with a gross vehicle weight in excess of 3.5 tons and buses with a carrying capacity of more than 16 persons. Most MHD commercial vehicles are custom-made and manufactured in diversified small-quantity batch production systems for commercial or public use, resulting in difficulties in utilizing mandatory vehicle tests for fuel efficiency evaluations.

As a part of the global efforts to reduce CO2 emission, studies are in progress to derive regulation measures for CO2 emission from heavy-duty vehicles. Thus, identification of emission characteristics of CO2 for heavy-duty vehicle is required and test driving cycle for this would be necessary. Before developing a test driving cycle to identify the emission characteristics of CO2, selection of test subject vehicles and actual road test was carried out. Through this, road drive characteristics per diverse vehicle type and emission levels of CO2 were identified. Correlations between the currently used cycles of each country and the actual road were analyzed and the cycle most similar to the actual road situations was selected among various countries' cycles to verify whether its easy use was possible for the actual tests. The test driving cycle selected after comparison with actual road situations was modified so as to enable actual tests for all heavy-duty vehicles.

Studies of driving cycles for buses have been published in a number of papers, e.g., the Central Business District (CBD) and New York Bus (NY Bus) driving cycles. Such studies, however, cannot represent the actual driving environment of Seoul because of differences in road conditions and the volume of traffic. Thus, this study presents the development of a driving cycle for the city bus system of Seoul, the capital city of Korea. A representative route is selected by means of a statistical analysis of the city bus routes in Seoul. Experiments are performed to measure velocity, road grade, engine speed, load conditions, gear-shift patterns, and vehicle acceleration in actual Seoul traffic. A simulation model is developed to evaluate a driving cycle on the basis of the measured data obtained. The coupling effect between velocity and acceleration is analyzed, as well as the coupling effect between road grade and vehicle acceleration.

Electromagnetic valve (EMV) actuation system is a new technology for the improvement of fuel efficiency and the reduction of emissions in SI engines. It can provide more flexibility in valve event control compared to conventional variable valve actuation devices. However, a more powerful and efficient actuator design is needed for this technology to be applied in mass production engines. This paper presents the effects of design and operating parameters on the thermal, static and dynamic performances of the actuator. The finite element method (FEM) and computer simulation models are used in predicting the solenoid forces, dynamic characteristics and thermal characteristics of the actuator. Effect of design parameters and operating environment on the actuator performance were verified before making prototypes using the analytical models. To verify the accuracy of the simulation model, experimental study is also carried out on a prototype actuator.

The residual gas in SI engines is one of important factors on emission and performance such as combustion stability. With high residual gas fractions, flame speed and maximum combustion temperature are decreased and there are deeply related with combustion stability, especially at Idle and NOx emission at relatively high engine load. Therefore, there is a need to characterize the residual gas fraction as a function of the engine operating parameters. A model for predicting the residual gas fraction has been formulated in this paper. The model accounts for the contribution due to the back flow of exhaust gas to the cylinder during valve overlap and it includes in-cylinder pressure prediction model during valve overlap. The model is derived from the one dimension flow process during overlap period and a simple ideal cycle model.

Results from an experimental study of flow distribution in a close-coupled catalytic converter (CCC) are presented. The experiments were carried out with a flow measurement system specially designed for this study under steady and transient flow conditions. Flow distribution at the exit of the first monolith was measured by a pitot tube. Numerical analysis was also performed for comparison. Experimental results showed that the flow uniformity index decreases as Reynolds number for the flow increases. For steady flow conditions, the flow through each exhaust pipe concentrates on a specific region of the monolith. The transient test results showed that the flow through each exhaust pipe, in the engine firing order, interacts with each other to make the flow distribution uniform. The numerical analysis results supported the experimental results, and helped explain the flow distribution in the CCC.