• Transactions of the Korean Society of Automotive Engineers
• /
• v.7 no.9
• /
• pp.28-35
• /
• 1999

In this study, investigation of transient knock characteristics in a spark-ignition engine has been carried out. The universal knock threshold values were found by a DFDD method and a NSDBP method which is a non-dimensional version of the SDBP method. Also modified NSDBP method could be used for transient knock detection. In a commercial ECU , spark timing was retarded from the steady -state spark timing during rapid throttle opening to avoid uncomfortable feeling and knock. Knock usually occurred just after the start of rapid throttle opening when spark timing was set, as values for the steady state condition. We found that air/fuel ratio deeply involved with the knock during transient condition. Due to the difference of initial heat release rate, knock occurred more easily at rich air/fuel ratio than at lean air/fuel ratio.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.33 no.4
• /
• pp.248-254
• /
• 2009

The HCCI engine is a next generation engine, with high efficiency and low emissions. The engine may be an alternative to SI and DI engines; however, a pressure rise rate is a major limitation for high load range and power reduction. Recently, we were able to reduce the pressure rise rate using thermal stratification. Nevertheless, this was insufficient to produce high power. In this study, the reduction of the pressure rise rate using thermal stratification was confirmed and the HCCI engine power was increased using the boost pressure. The rate and engine power were produced by CHEMKIN and modified SENKIN. As a result of increasing the boost pressure, a higher IMEP was attained while the pressure rise rate increased only slightly in the HCCI with thermal stratification.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.17 no.4
• /
• pp.32-39
• /
• 2009

The HCCI engine is a next generation engine, with high efficiency and low emissions. The engine may be an alternative to SI and DI engines; however, HCCI's operating range is limited by an excessive rate of pressure rise during combustion and the resulting engine knock in high-load. The purpose of this study was to gain a understanding of the effect of only initial temperature and thermal stratification for reducing the pressure-rise rate in HCCI combustion. And we confirmed characteristics of combustion, knocking and emissions. The engine was fueled with Di-Methyl Ether. The computations were conducted using both a single-zone model and a multi-zone model by CHEMKIN and modified SENKIN.

• Transactions of the Korean hydrogen and new energy society
• /
• v.20 no.3
• /
• pp.256-263
• /
• 2009

The operating range of HCCI engine is narrow due to excessive rate of pressure rise on high load. The fuel stratification is proposed to solve the problem. The purpose of this study is to gain a better understanding of the effects of fuel stratification on reducing the pressure-rise rate at high load in HCCI combustion and to investigate that the operating range is expanded for fuel stratification in the preceding condition of initial temperature and equivalence ratios. The engine is fueled with Di-Methyl Ether (DME) which has unique 2-stage heat release. The computations were conducted using SENKIN application of the CHEMKINll kinetics rate code. Calculation result shows that proper fuel stratification prolongs combustion duration and reduce pressure rise rate.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.18 no.3
• /
• pp.19-25
• /
• 2010

The purpose of this study is to gain a better understanding of the effects of fuel stratification on reducing the pressure-rise rate at high load in HCCI combustion. It was found that fuel stratification offers good potential to achieve a staged combustion event and reduced pressure-rise rates. The engine is fueled with Di-Methyl Ether (DME) which has unique 2-stage heat release. Numerical analysis is conducted with single and multi-zones model and detailed chemical reaction scheme is done by chemkin and senkin. Calculation result shows that proper fuel stratification prolongs combustion duration and reduce pressure rise rate. Besides IMEP, combustion efficiency and indicated thermal efficiency keep constant. However, too wide fuel stratification increases pressure rise rate and CO and NOx emissions in exhaust gas.

• Transactions of the Korean hydrogen and new energy society
• /
• v.20 no.4
• /
• pp.344-351
• /
• 2009

A multi-zone model was used to predict the operating range of homogeneous charge compression ignition (HCCI) engine, the boundaries of the operating range were determined by knock (presented by ring intensity), misfire (presented by sensitivity of indicated mean effective pressure to the initial temperature). A HCCI engine fueled with Di-Methyl Ether (DME) was simulated under different initial temperature and equivalence ratios, and the operating range was well produced by the model. Furthermore, the model was applied to develop the operating range for thermal stratification in the preceding condition of initial temperature and equivalence ratios. The computations were conducted using Senkin application of the CHEMKINII kinetics rate code.