| THEORETICAL FLOW ANALYSIS AND EXPERIMENTAL STUDY ON TIME RESOLVED THC FORMATION WITH RESIDUAL GAS IN A DUAL CVVT ENGINE |
| C. L. MYUNG1, H. KWAK2, I. G. HWANG1, S. PARK1 |
1Korea University
2Hyundai Motor Company |
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| ABSTRACT |
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Recently, a variable valve timing system has been widely adopted in internal combustion engine in order to improve the fuel economy and torque at low engine speed. In addition, it is known that varying valve timing according to the arious engine operations could reduce exhaust gas, especially NOx, because of residual gas by valve overlap. In this study, to improve the low exhaust gas and fuel economy at part load condition, the residual gas and back flow of exhaust gas due to valve overlap were calculated computationally. Moreover, the characteristics of engine performances and NOx formations were investigated with the experiment of combination of intake and exhaust valve timing condition. Under these various valve operating conditions, the effects of both the positive valve overlap and negative valve overlap (valve underlap) were examined simultaneously. Finally, the characteristics of cyclic THC emission were analyzed by using Fast Response FID (FR-FID) in the cylinder, intake port and exhaust port positions. Besides, the effect of the different gradients of the valve timing change on engine performance was investigated and an optimum control strategy was suggested. |
| Key Words:
VVT, Valve overlap, Internal EGR, Residual gas, Fast response FID, Cyclic THC emission |
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