Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel Full Length Article The comparison of combustion, engine performance and emission characteristics of ethanol, methanol, fusel oil, butanol, isopropanol and naphtha with n-heptane blends on HCCI engine Alper Calam a, ⁎ , Bilal Aydoğan b , Serdar Halis c a Gazi University, Technical Sciences Vocational High School, Ankara, Turkey b Burdur Mehmet Akif Ersoy University, Technical Sciences Vocational High School, Burdur, Turkey c Gazi University, Faculty of Technology, Department of Automotive Engineering, Ankara, Turkey ARTICLE INFO Keywords: Fuel HCCI Low temperature combustion Emissions Combustion Operating range ABSTRACT Recently, there has been increased emphasis on the homogenous charge compression ignition (HCCI) engine which offers higher thermal efficiency and ultra-low NO x and soot emissions. The central thesis of this paper is that the effects of different alternative fuels with different physical and chemical properties on combustion, performance and emissions in a HCCI engine. Ethanol (E25), methanol (M25), fusel oil (F25), butanol (B25), isopropanol (IP25) and naphtha (N25) were used alternative fuels blended with n-heptane 25% by volume. The experiments were performed at 333 K intake air temperature (IAT) and with various excess air coefficient in a single cylinder SI-HCCI test engine. The parameters such as in-cylinder pressure, heat release rate (HRR), start of combustion (SOC), combustion duration, CA50, indicated thermal efficiency (ITE), COV IMEP , maximum pressure rise rate (MPRR), HC and CO emissions were investigated. In addition, operating range of the fuels were also defined. The results showed that N25 has the largest operating range among all the test fuels. The maximum indicated mean effective pressure (IMEP) value was obtained for E25 as 5.71 bar at 800 rpm engine speed and λ = 1.3. Knocking tendency were determined for all test fuels but it decreased with increasing lambda value. The highest HC and CO emissions were obtained for F25 due to the water content of the fuel. On the contrary, the lowest HC and CO emissions were obtained for N25. 1. Introduction Many researches on alternative fuels and combustion modes has become important issue due to the decrease in fossil fuel stocks, in- creasing prices and damaging the environment in terms of emissions [1–3]. Homogenous charge compression ignition (HCCI) engine is a promising concept which offers higher thermal efficiency and ultra-low nitrogen oxide (NO x ) and soot emissions than conventional gasoline and diesel engines due to low temperature combustion (LTC) [4,5]. In HCCI combustion mode, fuel and air are premixed like spark ignition (SI) engines and air/fuel mixture is compressed until whole mixture reacts like compression ignition (CI) engines [6]. In other words, HCCI engine have the advantages of both SI and CI engines. In addition to these superior properties of HCCI engines, there are some difficulties intrinsic to HCCI combustion in the manner of uncontrolled combustion phasing, knocking, misfiring and high levels of carbon monoxide (CO) and hydrocarbon (HC) emissions [7–9]. A broad and detailed data of the advantages and disadvantages of the HCCI engine can be found in [10–13]. Knocking at high loads and misfiring at low loads are the most important parameters which limits the operation range of HCCI engines [14,15]. It is very important to determine the knocking and misfring as early as possible to prevent engine damage and to achieve stable engine operation [1]. Knocking combustion occurs more easily in HCCI engine than conventional diesel engine because of the fuel injection begins very early and combustion rate can not be controlled [16]. Misfiring can be clarified as lack of combustion, incomplete combustion, unstable combustion and failure of combustion [17–19]. Some studies focused on the control of knocking and misfiring with several methods such as variable valve timing, residual gases in cylinder, injection timing, variable compression ratio, variable intake air temperature (IAT) and using alternative fuels with high octane number [5,12,20–24]. Injection timing, IAT and variable compression ratio increase the velocity of reaction in the cylinder to overcome the problem of misfire. Homo- geneous mixing and increased end-of-in-cylinder temperature enlarge the HCCI operating range [23,25,26]. The amount of residual gas in the cylinder reduces the heat release due to dilution of fresh charge. In https://doi.org/10.1016/j.fuel.2020.117071 Received 29 October 2019; Received in revised form 17 December 2019; Accepted 10 January 2020 ⁎ Corresponding author. E-mail addresses: acalam@gazi.edu.tr (A. Calam), baydogan@mehmetakif.edu.tr (B. Aydoğan), serdarhalis@gazi.edu.tr (S. Halis). Fuel 266 (2020) 117071 0016-2361/ © 2020 Published by Elsevier Ltd. T