Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel Full Length Article The effects of diisopropyl ether on combustion, performance, emissions and operating range in a HCCI engine Ahmet Uyumaz a, ⁎ , Bilal Aydoğan b , Alper Calam c , Fatih Aksoy d , Emre Yılmaz e a Burdur Mehmet Akif Ersoy University, Faculty of Engineering – Architecture, Department of Mechanical Engineering, Burdur, Turkey b Burdur Mehmet Akif Ersoy University, High Vocational School of Technical Sciences, Burdur, Turkey c Gazi University, Ostim High Vocational School, Ankara, Turkey d Afyon Kocatepe University, Faculty of Technology, Department of Automotive Engineering, Afyon, Turkey e Hakkari University, Faculty of Engineering, Department of Mechanical Engineering, Hakkari, Turkey ARTICLE INFO Keywords: Diisopropyl ether HCCI combustion Performance Emissions Operating range ABSTRACT In the current study, the effects of diisopropyl ether were experimentally investigated on combustion, perfor- mance, emissions and operating range in a homogeneous charged compression ignition (HCCI) engine. For this purpose, a single cylinder, four stroke, port injection test engine was run with different lambda values between 1.69 and 3.08 on HCCI mode with pure n-heptane, 20% diisopropyl ether 80% n-heptane (D20N80), and 40% diisopropyl ether 60% n-heptane (D40N60) fuel blends at full load. HCCI engine was operated between 800 and 1600 rpm engine speed at constant inlet air temperature of 60 °C and wide open throttle (WOT). The effects of diisopropyl ether addition were observed on cylinder pressure, heat release rate (HRR), combustion duration (CD), indicated mean effective pressure (imep), brake torque, power output, specific fuel consumption (SFC) and exhaust emissions. Test results showed that the increase of lambda leads to lower in-cylinder pressure and HRR. The addition of diisopropyl ether caused to retard combustion. Indicated thermal efficiency (ITE) increased 4.92% with D40N60 compared that n-heptane at 1200 rpm and λ = 2. Brake torque and power output increased by about 1.03% and 1.18% with D20N80 according to pure n-heptane at 1200 rpm respectively. On the contrary, SFC decreased 24.08% with D40N60 compared to n-heptane at 1200 rpm and λ = 2. HC and CO increased with the addition of diisopropyl ether. The test results also showed that the addition of diisopropyl ether expanded the HCCI combustion towards to knocking and partial combustion zone. 1. Introductıon Homogeneous charged compression ignition engines (HCCI) have received great attention by researchers due to high thermal efficiency and lower CO release. HCCI combustion provides simultaneous reduc- tion on soot and NO x emissions, because they are significant handicap in compression ignition (CI) engines. HCCI engines also give reasonable thermal efficiency in spite that the engine runs with leaner charge mixture. Low temperature combustion (LTC) is seen such as reactive controlled compression ignition (RCCI), premixed charge compression ignition (PCCI) and partial premixed combustion (PPC) [1–6]. That phonomena shows to be enviromentally friendly economic combustion mode compared conventional combustion cycles. Nevertheless, HC formation increases due to lower in-cylinder wall and combustion chamber temperature especially with leaner charge mixtures in HCCI combustion. Exhaust gas after treatment systems such as diesel particulate filter (DPF), three way catalytic converter have been used in order to reduce exhaust emissions. But, these systems are not cost-ef- fective and enough practical to use fertilely in the internal combustion engines [2–11]. Hence, HCCI is seen to present good potential in view of lower exhaust emisssions and reasonable performance. However, HCCI operating range is restricted by misfiring and knocking at low and high engine load respectively. Knocking is seen due to uncontrollable auto-ignition process, because combustion phasing is directed by che- mical kinetics and thermodynamic situation at the end of compression stroke apart from spark ignition (SI) and CI cycles [3–15]. Excess air is needed due to combustion of richer charge mixture in order to reduce knocking tendency and complete oxidation reactions on HCCI mode. On the contrary, auto-ignition chemical reactions are deteriorated because of lower end gas temperature and combustion efficiency with leaner mixture. On the other hand, sudden and simultaneous self-ignition causes to higher pressure rise rate resulting in pressure oscillations in https://doi.org/10.1016/j.fuel.2019.116919 Received 11 June 2019; Received in revised form 21 August 2019; Accepted 17 December 2019 ⁎ Corresponding author. Tel.: +90 248 2132765; fax: +90 248 213 27 04. E-mail addresses: auyumaz@mehmetakif.edu.tr (A. Uyumaz), baydogan@mehmetakif.edu.tr (B. Aydoğan), acalam@gazi.edu.tr (A. Calam), faksoy@aku.edu.tr (F. Aksoy), emreyilmaz@hakkari.edu.tr (E. Yılmaz). Fuel 265 (2020) 116919 0016-2361/ © 2019 Elsevier Ltd. All rights reserved. T