Late Injection HCCI 연소 최적화를 위한 압축비, 스월강도, 분무 파라미터의 영향 분석

Abstract

The purpose of this study is to optimize Late Injection Homogeneous Charge Compression Ignition (HCCI) which is also known as Modulated Kinetics (MK) combustion by analyzing the effects of compression ratio, swirl intensity and spray parameters on the exhaust emission reduction and application range expansion of MK combustion in the common rail diesel light-duty engine. A 500-cc single-cylinder engine based on the Hyundai R engine was used for the study and a 55kW AC dynamometer was used for the engine operation. For the engine control, Compact Rio was controlled through the code developed using the NI Labview Code, and the combustion and exhaust results were saved through the Data Acquisition Board and Compact Rio. The stored data were analyzed by a combustion analyzer that we made. This study consists of three parts. First, the injection time and EGR rate swing experiment were performed as a basic study to analyze the combustion characteristics and exhaust characteristics of MK combustion. The EGR rate was changed from 0% to 50% in intervals of 5%, and the injection time was changed from 6 deg forward to 6 deg perception in 2-deg increments while maintaining the number of injections and injection dwell time. Because the ignition delay increases with increasing EGR rate, it is advantageous for the MK combustion, but the effect is small and MK combustion is only realized in Case 3 which is the lowest load condition. In the injection time swing results the MK combustion was implemented in Case 1, Case 2, and Case 3, but the MK region was notably small in Case 2, which is the highest load condition. In the second part, we analyzed the effect of the swirl and injector hole number to reduce the unburned gas such as THC and CO. The swirl ratio was controlled through the swirl control valve (SCV) angle in front of the intake port. The 7, 8, 9, and 10-hole injectors were used to analyze the effect of the injector hole number. When the swirl strength increases, the PM, THC, and CO decrease, but NOx increases. Although the PM, THC, and CO decrease when the injector hole number increases, the 9-hole injector exhibits the best exhaust characteristics because the injection interference occurs from the 10th hole. In the third part we analyzed the effect of the compression ratio and HFR to expand the MK combustion area. Experiments were performed at compression ratios of 15 and 17 using a piston with different compression ratios and HFR 310 and 390 injectors. When the compression ratio increases, the internal temperature and pressure of the cylinder increases, thus the ignition delay increases and the MK combustion region decreases. However, since the IMEP increases and the ISFC decreases, increasing the compression ratio deteriorates the exhaust characteristics, but the output is improved. The increase in HFR diminishes the injection duration and increased the ignition delay, but the overall exhaust characteristics deteriorate.