Energy Fuels 2010, 24, 2455–2464 Published on Web 03/30/2010
: DOI:10.1021/ef9015944
Comparative Study on Engine Performance and Diesel Emissions with European Diesel Fuel (DF)-Diethylene Glycol Dimethyl Ether (DGM) and Fischer-Tropsch (FT)-DGM Blends Md. Nurun Nabi,*,† Rudolf Schmid,‡ and Johan Einar Hustad† †
Department of Energy and Process Engineering and ‡Department of Chemistry, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway Received December 25, 2009. Revised Manuscript Received March 6, 2010
An experimental study of diesel engine performance and exhaust emissions with Fischer-Tropsch (FT)-diethylene glycol dimethyl ether (DGM) and European diesel fuel (DF)-DGM blends were conducted in the current investigation. DGM, an oxygenated fuel with 5-10% (v/v) was blended with FT and DF. No phase separation between FT and DGM blends or DF and DGM blends was found. The blends were termed as DFox5 (95% DF and 5% DGM), DFox10 (90% DF and 10% DGM), FTox5 (95% FT and 5% DGM), and FTox10 (90% FT and 10% DGM). The fuels were characterized chemically by gas chromatography (GC). GC indicated a high content of n-alkanes in the DF but not in the FT fuel. The combustion experiments were conducted with a six-cylinder, four-stroke, turbocharged, direct-injection (DI) diesel engine. Relative to DFox5 and DFox10 fuels, the experimental results showed lower total unburned hydrocarbon (THC), carbon monoxide (CO), smoke, particulate matter (PM), and oxides of nitrogen (NOx) emissions with FTox5 and FTox10 fuels. The brake-specific fuel consumption (BSFC), brake-specific energy consumption (BSEC), and engine thermal efficiency were identical with all fuels.
CO and THC emissions were lower because of the higher cetane number and lower densities of FT fuel, and NOx emissions were lower with FT fuel when compared to diesel fuel (DF). Kahandawala et al.3 examined PM emissions from two FT fuels, Shell middle distillate (MDS) and Mosgass conversion of olefins to distillate (COD), in a reflected shock tube. It has been observed that Shell MDS reduced PM emissions significantly compared to D-2 DF. McMillan et al.4 found lower emissions with FT fuel. Without modifying the engine, Huang et al.5 found lower CO, THC, NOx, and smoke emissions relative to DF100 fuel. In comparison to DF, FT fuel reduced emissions including benzene by 30-95%, toluene by 10-90%, o-xylene by 60-95%, and m-xylene by 30-90%.6 Other emission results from the literature have reported comparable or lower NOx emissions.7 Similar to FT fuel, oxygenated fuel is considered to be another alternative fuel for the diesel engine. The oxygenated fuels contain oxygen in their molecules and help reduce diesel emissions, especially soot emissions. Nabi et al.8 conducted an
1. Introduction Internal combustion (IC) engines have been identified as a major source of air pollution. Diesel exhaust emissions including oxides of nitrogen (NOx) and particulate matter (PM) are the prime concerns for not only the environment but also humans. Stringent regulations forced researchers to explore environmentally friendly alternative fuels for transportation sectors. Fischer-Tropsch (FT) fuel is considered one of the alternative fuels for diesel engines. FT fuel can be prepared from natural gas, coal, and biomass sources. Unlike fossil fuel, FT fuel can be considered as a renewable fuel if it is prepared from biomass sources. It is well-known that the FT fuel is prepared from synthesis gas (carbon monoxide and hydrogen) with a catalytic chemical reaction. Mainly cobalt and iron are used as catalysts in FT synthesis. The output of the FT synthesis is a liquid hydrocarbon mixture. Because of the absence of sulfur and aromatic compounds, FT is effective at reducing diesel emissions. Wu et al.1 investigated the performance and engine emissions with gas-liquid (GTL) blends. The authors reported improvements in fuel economy and thermal efficiency with neat GTL and blends of GTL. Further, it has been found that the GTL blends can reduce carbon monoxide (CO), total unburned hydrocarbon (THC), soot, PM, and NOx emissions simultaneously at different engine-operating conditions. It has been reported2 that soot emissions were lower because the amount of aromatic compounds in FT fuel is negligible,
(3) Kahandawala, M. S. P.; Graham, J. L.; Sidhu, S. S. Particulate emission from combustion of diesel and Fischer-Tropsch fuels: A shock tube study. Energy Fuels 2004, 18 (2), 289–295. (4) McMillan, M. H.; Goutam, M. Combustion and emission characteristics of Fischer-Tropsch and standard diesel fuel in a singlecylinder diesel engine. SAE Tech. Pap. 2001-01-3517, 2001. (5) Huang, Y.; Wang, S.; Zhou, L. Effects of Fischer-Tropsch diesel fuel on combustion and emissions of direct injection diesel engine. Front. Energy Power Eng. China 2008, 2 (3), 261–267. (6) Nord, K.; Haupt, D. Evaluating a Fischer-Tropsch fuel, Eco-Par, in a valmet diesel engine. SAE Tech. Pap. 2002-01-2726, 2002. (7) Cowart, J. S.; Sink, E. M.; Slye, P. G.; Caton, P. A.; Hamilton, L. J. Performance, efficiency and emissions comparison of diesel fuel and a Fischer-Tropsch synthetic fuel in a CFR single cylinder diesel engine during high load operation. SAE Tech. Pap. 2008-01-2382, 2008. (8) Nabi, M. N.; Minami, M.; Ogawa, H.; Miyamoto, N. Ultra low emission and high performance diesel combustion with highly oxygenated fuel. SAE Tech. Pap. 2000-01-0231, 2000.
*To whom correspondence should be addressed. E-mail: nurun.nabi@ ntnu.no. (1) Wu, T.; Huang, Z.; Zhang, W. G.; Fang, J. H.; Yin, Q. Energy Fuels 2007, 21, 1908–1914. (2) Larsson, M.; Denbratt, I. An experimental investigation of Fischer-Tropsch fuels in a light-duty diesel engine. SAE Tech. Pap. 2007-01-0030, 2007. r 2010 American Chemical Society
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Energy Fuels 2010, 24, 2455–2464
: DOI:10.1021/ef9015944
Nabi et al.
Figure 1. Schematic diagram of the tested engine.
engine experiment with highly oxygenated fuels. The authors achieved ultra-low diesel emissions with the combination of exhaust gas recirculation (EGR), a three-way catalyst, and highly oxygenated fuels. It has been reported that diesel smoke emissions completely disappeared with an oxygen content of 38 wt % at any operating condition, even at stoichiometric condition. About 100 ppm NOx and CO emissions were realized, while 200 ppm THC emissions were observed. Miyamoto et al.9 performed engine experiments with four neat oxygenated fuels. The oxygenated fuels were diethylene glycol dimethyl ether (DGM), di-nbutyl ether (DBE), 2-ethyl hexyl acetate (EHA), and ethylene glycol-mono-n-butyl ether (ENB). The oxygen content in the oxygenated fuels was varied from 12 to 36%. Lower exhaust emissions including THC, CO, NOx, smoke, and PM, as well as higher thermal efficiency, were reported. The reductions were entirely dependent upon the fuel oxygen content. Ogawa et al.10 performed an engine experiment with highly oxygenated fuel, dimethoxy methane (DMM), which contains 42 wt % oxygen in a molecule. The authors reported extremely low diesel emissions with high engine performance, with a combination of high EGR, three-way catalyst, and DMM. Wang et al.11 investigated diesel PM emissions with different oxygenated blends. Several oxygenated blends including ethanol, biodiesel, and dimethyl carbonate (DMC) were made with DF. In comparison to DF, dry soot (DS), which is a constituent of PM emissions, was reduced significantly with oxygenated blends. It has been found that fuel oxygen in oxygenated blends reduced PM emissions. Sayin et al.12 investigated the influence of operating parameters on diesel engine performance and exhaust emissions with methanol-diesel-blended
Table 1. Specifications of the Tested Engine engine type compression ratio number of cylinders bore stroke (mm) firing sequence maximum power (kW) maximum torque (N m) injection system injection pressure (bar) number of holes size of hole (mm)
Scania DC 1102 18:1 6 127 140 1-5-3-6-2-4 280 at 1800 rpm 1750 at 1080-1500 rpm unit injector 220 8 0.216
fuels. The authors found lower THC, CO, and smoke emissions with all methanol blends, while lower brake thermal efficiency and higher NOx emissions were realized with the same blends. Kozak et al.13 conducted engine experiments with 11 kinds of oxygenated additives. The additives were classified into three main categories: glycol ethers, maleates, and carbonates. It has been reported that the most favorable changes in the PM/NOx emission trade-off were obtained for maleates and carbonates. The authors also reported that the changes in PM/NOx reduction was dependent upon not only the oxygen content in fuel but also the oxygenate type and its properties. In the current study, the diesel engine performance and exhaust emissions were investigated with the blends of FT-DGM and DF-DGM. DGM was blended with two base fuels: DF100 and FT100 fuels. FT fuel was chosen as the base fuel for its superior properties, including low sulfur and aromatic contents, compared to DF100 fuel. FT fuel in this study is made from natural gas, and the price is comparable to conventional DF. DGM was selected as an oxygenated additive for its low volatility and high ignitability. Similar to DGM, other oxygenates, such as DBE, ENB, and EHA, reduce exhaust emissions significantly.9 The purpose of the current investigation was to compare the engine performance and emission results between the two base fuel blends. On the basis of the performance and emission results, suggesting an alternative fuel for the diesel engine was also a target of this investigation.
(9) Miyamoto, N.; Ogawa, H.; Nabi, M. N.; Obata, K.; Arima, T. Smokeless, low NOx, high thermal efficiency and low noise diesel combustion with oxygenated agents as main fuel. SAE Tech. Pap. 980506, 1998. (10) Ogawa, H.; Nabi, M. N.; Minami, M.; Miyamoto, N.; Seock, K. B. Ultra low emission and high performance diesel combustion with a combination of high EGR, three way catalyst and a highly oxygenated fuel, dimethoxy methane (DMM). SAE Tech. Pap. 2000-01-1819, 2000. (11) Wang, J.; Wu, F.; Xiao, J.; Shuai, S. Oxygenated blend design and its effects on reducing diesel particulate emissions. Fuel 2009, 88, 2037–2045. (12) Sayin, C.; Ozsezen, A. N.; Canakci, M. The influence of operating parameters on the performance and emissions of a DI diesel engine using methanol-blended-diesel fuel. Fuel 2010, DOI: 10.1016/j. fuel.2009.10.035.
(13) Kozak, M.; Merkisz, J.; Bielaczyc, P.; Szczotka, A. The influence of oxygenated diesel fuels on a diesel vehicle PM/NOx emission tradeoff. SAE Tech. Pap. 2009-01-2696, 2009.
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Energy Fuels 2010, 24, 2455–2464
: DOI:10.1021/ef9015944
Nabi et al. Table 2. Properties of Tested Fuels
properties mono-aromatic hydrocarbon (%, v/v) di-aromatic hydrocarbon(%, v/v) polyaromatic hydrocarbon (%, v/v) density at 15 °C (g/cm3) calorific value (MJ/kg) boiling point (°C) cetane number carbon (wt %) hydrogen (wt %) oxygen (wt %)
DF100
DFox5
DFox10
18
17.6 4.218 0.0618 0.845 42.40 328.0 49.50 85.90 14.05 0.00
FT100
FTox5
FTox10
DGM
0.807 43.00 305.5 55.65
0.815 42.03 298 59.35
1.80
3.60
0.95 24.5 163 126 53.7 10.4 35.8
18
0.850 41.50 319.72 53.32 84.38 13.82 1.80
0.856 40.61 311.45 57.15 82.77 13.65 3.60
0.2
