Optimization of combustion chamber geometry and operating conditions for compression ignition engine fueled with pre-blended gasoline-diesel fuel Seokhwon Lee a , Joonho Jeon a , Sungwook Park b,⇑ a Department of Mechanical Convergence Engineering, Graduate School of Hanyang University, Seoul 04763, Republic of Korea b School of Mechanical Engineering, Hanyang University, Seoul 04763, Republic of Korea article info Article history: Received 6 June 2016 Received in revised form 17 August 2016 Accepted 18 August 2016 Keywords: Gasoline–diesel pre-blended fuel Combustion performance Optimization Fuel efficiency abstract In this study, experiments and numerical simulations were used to improve the fuel efficiency of com- pression ignition engine using a gasoline-diesel blended fuel and an optimization technology. The blended fuel is directly injected into the cylinder with various blending ratios. Combustion and emission characteristics were investigated to explore the effects of gasoline ratio on fuel blend. The present study showed that the advantages of gasoline-diesel blended fuel, high thermal efficiency and low emission, were maximized using the numerical optimization method. The ignition delay and maximum pressure rise rate increased with the proportion of gasoline. As the gasoline fraction increased, the combustion duration and the indicated mean effective pressure decreased. The homogeneity of the fuel-air mixture was improved due to longer ignition delay. Soot emission was significantly reduced up to 90% compared to that of conventional diesel. The nitrogen oxides emissions of the blended fuel increased slightly when the start of injection was retarded toward top dead center. For the numerical study, KIVA-CHEMKIN multi-dimensional CFD code was used to model the combustion and emission characteristics of gasoline-diesel blended fuel. The micro genetic algorithm coupled with the KIVA-CHEMKIN code were used to optimize the combustion chamber shape and operating conditions to improve the combustion performance of the blended fuel engine. The optimized chamber geometry enhanced the fuel efficiency, for a level of nitrogen oxides similar to that of conventional diesel over a variety of operation ranges. Ó 2016 Elsevier Ltd. All rights reserved. 1. Introduction Emissions of internal combustion engines must be reduced due to emission regulations. Compression Ignition (CI) engines are widely used for their efficient fuel consumption, but CI combustion is progressed in locally rich mixture and high temperature region. This is why their soot and NO x emissions are higher than those of spark ignition engines. To reduce exhaust emissions, Homoge- neous charge compression-ignition (HCCI) technology, in which the charge is premixed before being compression ignited, is used to achieve both high efficiencies and low NO x and soot emissions [1,2]. The combustion phasing, ignition timing and cylinder pres- sure rate rise for HCCI concept is difficult to control [3]. To control the combustion of HCCI, Kokjohn et al. [4] used reactivity con- trolled compression ignition (RCCI) by varying fuel reactivity. The variation in fuel reactivity was conducted by in-cylinder fuel blending using port fuel injection of gasoline and early cycle direct injection of diesel. Yang et al. [5] also investigated the effect of RCCI combustion and the blended-fuel low temperature combustion (LTC) mode with gasoline and diesel. Blended fuel LTC mode had higher fuel concentration than dual fuel highly premixed charge combustion (HPCC). For this reason, the combustion in HPCC mode was less complete than that of LTC mode and had a lower combus- tion efficiency. Chao et al. [6] compared the combustion of gasoline homoge- neous charge induced ignition (HCII) and gasoline/diesel blend fuels (GDBF). As the gasoline fraction increased, the improved fuel-air mixing in both HCII and GDBF reduced soot emissions by over 90%. This demonstrated that HCII and GDBF have a benefit compared to the diesel CI combustion. Benajes et al. [7] carried out to analyze mixing air-fuel and auto-ignition processes in RCCI combustion conditions, using a fuel blend of gasoline and diesel. In order to analyze air-fuel mixing process in detail, a 1-D spray model was used. The ignition delay increased and the mixture http://dx.doi.org/10.1016/j.enconman.2016.08.046 0196-8904/Ó 2016 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: School of Mechanical Engineering, Hanyang Univer- sity, 222 Wangsimni-ro, Seongdong-gu, Seoul 04763, Republic of Korea. E-mail address: parks@hanyang.ac.kr (S. Park). Energy Conversion and Management 126 (2016) 638–648 Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman