E305 Characteristics of THC Emission and Combustion Stability with Spark Timing Retard at Cold Start in SI Engine(SI engine performance)
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概要
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In this study, the mass of THC is reduced almost 40 percent with spark timing ATDC 7.8CA during 15 seconds from engine start in phase 1 of LA4 mode, comparison with BTDC 2.8CA. One of the reasons of THC reduction in vehicle test is reduction of raw THC concentration before CCC that is 36% lower level than base condition. The other reason is that the LOT of catalyst is shortened from 34 seconds to below 20 seconds. Therefore in order to maintain a pre-determined idle speed as base vehicle, the mass of intake air should be increased and LOT was shortened. To find out the reason of THC reduction with spark timing retard, THC concentration is measured at an exhaust port and manifold in single cylinder engine and flame propagation was visualized as well. Spark timing is correlated with the duration of combustion. THC concentration is inversely proportional to the lasting time of flame. The applicability of spark timing retard in mass production vehicle is evaluated by engine speed fluctuation in cold idle. Combustion stability of engine such as IMEP COV (Equation (1)) or IMEP LNV (Equation (2)) at coolant temperature 30℃ was not much difference between BTDC 2.8CA and ATDC 7.8CA spark timing operation. Because engine stability is correlated with not only spark timing but also intake MAP related with internal EGR. Therefore the spark timing retardation (up to some degrees ATDC) is one of the useful and applicable method for SULEV or ZLEV in gasoline engine vehicle.
- 一般社団法人日本機械学会の論文
- 2000-10-01
著者
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Choi Myung-sik
Power Train R&d Center Hyundai Motor Company
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Choi Jae-kwon
Power Train R&d Center Hyundai Motor Company