Performance characteristics of compression-ignition engine using high concentration of ammonia mixed with dimethyl ether Kyunghyun Ryu a , George E. Zacharakis-Jutz b , Song-Charng Kong b,⇑ a School of Mechanical and Automotive Engineering, Kunsan National University, South Korea b Department of Mechanical Engineering, Iowa State University, USA highlights  Performance of a diesel engine using direct-injection ammonia-DME is investigated.  Stable engine operation can be achieved by using early injection timings.  Combustion of high concentration of ammonia exhibits HCCI characteristics.  High load operations favor the use of high concentration of ammonia. article info Article history: Received 30 November 2012 Received in revised form 13 July 2013 Accepted 31 July 2013 Available online 24 August 2013 Keywords: Ammonia combustion Compression-ignition engine Alternative fuel Non-carbon fuel abstract Combustion and emissions characteristics of a compression-ignition engine using ammonia (NH 3 ) and dimethyl ether (DME) mixtures were investigated in this study. The experiments were conducted using three different mixtures, including 100%DME, 60%DME–40%NH 3 , and 40%DME–60%NH 3 (by weight). The injection pressure was maintained at approximately 20.6 MPa and engine combustion and exhaust emis- sions were measured in order to analyze and compare the performance of different mixture composi- tions. Results show that engine performance decreases as ammonia concentration in the fuel mixture increases. Significant cycle-to-cycle variations are observed when 40%DME–60%NH 3 is used. The injec- tion timing for best torque needs to be advanced with increased ammonia concentration in the fuel mix- ture due to the high resistance to autoignition of ammonia. Moreover, with the increase in ammonia concentration, both engine speed and engine power exhibit limitations relative to 100%DME cases. For 40%DME–60%NH 3 , the appropriate injection timing was found to range from 90 to 340 BTDC and the engine exhibits homogeneous charge compression ignition (HCCI) combustion characteristics due to the highly advanced injection timing. 40%DME–60%NH 3 conditions also results in higher CO and HC emissions due to the low combustion temperature of ammonia. Soot emissions for 40%DME–60%NH 3 remain extremely low. When ammonia is used, NOx emissions are increased due to the formation of fuel NOx. Exhaust ammonia emissions also increase as ammonia concentration in the fuel mixture increases from 40% to 60%. Overall, in this study appropriate strategies are developed to enable the use of ammonia in direct-injection compression-ignition engines and the corresponding engine performance is evaluated. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction It is important to explore the use of alternative engine fuels for reasons of environmental protection and energy conservation. The use of alternative fuels, such as biorenewable fuels, can help reduce the life-cycle carbon emissions. Studies on internal com- bustion engines using biorenewable fuels have increased steadily in recent years [1–4]. In addition to tradition biofuels such as bio- diesel and ethanol, it is also of critical importance to evaluate the use of non-carbon-based fuels to further reduce carbon dioxide (CO 2 ) emissions, an important greenhouse gas, in urban areas. Hydrogen (H 2 ) is recognized as a carbon-free fuel with favorable combustion characteristics. Hydrogen-fueled internal combustion engines and fuel cells have also received much attention and at- tracted significant public interest [5–7]. However, there are many challenges in using hydrogen for transportation due to various infrastructural issues such as production, storage, and transport. 0306-2619/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.apenergy.2013.07.065 Abbreviations: ATDC, after top-dead-center; BMEP, brake mean effective pressure; BSEC, brake specific energy consumption (MJ/kW h); BSFC, brake specific fuel consumption (g/kW h); BTDC, before top-dead-center; CAD, crank angle degree; DME, dimethyl ether (CH 3 OCH 3 ); EPA, Environmental Protection Agency; GDI, gasoline direct injection; IMEP, indicated mean effective pressure. ⇑ Corresponding author. Tel.: +1 515 294 3244. E-mail address: kong@iastate.edu (S.-C. Kong). Applied Energy 113 (2014) 488–499 Contents lists available at ScienceDirect Applied Energy journal homepage: www.elsevier.com/locate/apenergy