Homogeneous charge compression ignition (HCCI) combustion: Mixture preparation and control strategies in diesel engines Harisankar Bendu n , S. Murugan Department of Mechanical Engineering, National Institute of Technology Rourkela, India article info Article history: Received 26 September 2013 Received in revised form 7 May 2014 Accepted 6 July 2014 Available online 24 July 2014 Keywords: Homogeneous charge compression ignition (HCCI) Mixture preparation Low temperature combustion (LTC) Diesel engines abstract At present achieving fuel economy and reducing emissions are the two main targets set by the automotive industries. Homogeneous charge compression ignition (HCCI) technology is believed to be a promising one to be applied in both spark ignition (SI) and compression ignition (CI) engines in the near future. However, some challenges such as compromise combustion phase control, controlled auto- ignition, operating range, homogeneous charge preparation, cold start and emissions of unburned hydro carbon (UHC), and carbon monoxide (CO) need to be overcome for successful operation of HCCI engine. Extensive research on HCCI combustion with a homogeneous fuel–air mixture preparation is going on throughout the world. This paper reviews the strategies of different external and in-cylinder mixture preparation methods which were adopted and proposed in the recent years. The different strategies of controlled auto-ignition by HCCI combustion are also discussed in this paper. & 2014 Elsevier Ltd. All rights reserved. Contents 1. Introduction ........................................................................................................ 733 2. Challenges of HCCI combustion ........................................................................................ 734 2.1. Combustion phase control....................................................................................... 734 2.2. Abnormal pressure rise with noise ................................................................................ 734 2.3. Domain of operation ........................................................................................... 734 2.4. High levels of UHC and CO ...................................................................................... 734 2.5. Cold start .................................................................................................... 734 2.6. Homogeneous charge preparation ................................................................................ 735 3. Homogeneous charge preparation strategies .............................................................................. 735 3.1. External mixture preparation .................................................................................... 735 3.2. In-cylinder mixture preparation .................................................................................. 736 3.2.1. Early direct injection .................................................................................... 736 3.2.2. Late direct injection ..................................................................................... 738 3.3. Narrow angle direct injection NADI TM ............................................................................. 739 4. HCCI combustion control strategies ..................................................................................... 739 4.1. Control strategies to increase the mixture homogeneity ............................................................... 740 4.1.1. Ultra high injection pressure with small nozzle holes .......................................................... 740 4.1.2. High swirl ratio ........................................................................................ 740 4.1.3. Pulsed fuel injection .................................................................................... 740 4.1.4. High boost pressure..................................................................................... 740 Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/rser Renewable and Sustainable Energy Reviews http://dx.doi.org/10.1016/j.rser.2014.07.019 1364-0321/& 2014 Elsevier Ltd. All rights reserved. Abbreviations: ATAC, active thermal atmospheric combustion; ARC, activated radical combustion; CAD, crank angle degree; CAI, controlled auto-ignition; EGR, exhaust gas recirculation; HCCI, homogeneous charge compression ignition; HiMICS, homogeneous charge intelligent multiple injection combustion system; HTHR, high temperature heat release; OI, octane index; LTHR, low temperature heat release; LTC, LOw temperature combustion; MK, modulated kinetics; MULDIC, multiple stage diesel combustion; NADI TM , narrow angle direct injection; PCI, premixed compression ignited; PFI, port fuel injection; PPCI, partially premixed compression ignition; PCCI, premixed charge compression ignition; PREDIC, premixed lean diesel combustion; SCCI, stratified charge compression ignition; UNIBUS, uniform bulky combustion system; VCR, variable compression ratio; VVA, variable valve actuation n Corresponding author. E-mail address: hsbendu@gmail.com (H. Bendu). Renewable and Sustainable Energy Reviews 38 (2014) 732–746