Biodiesel Later-Phased Low Temperature Combustion Ignition and Burn Rate Behavior on Engine Torque

Author(s):  
Brandon T. Tompkins ◽  
Hoseok Song ◽  
Joshua Bittle ◽  
Timothy J. Jacobs
2014 ◽  
Vol 16 (6) ◽  
pp. 1057-1065

<div> <p>A set of experiments have been carried out in a heavy duty single cylinder engine using high <em>EGR</em> rates and different start of injection angles (<em>SOI</em>). Three different fuels (conventional diesel fuel, a diesel-ethanol mixture (e-diesel) and a Fischer-Tropsch fuel (GTL)) have been tested in order to evaluate their potential to achieve Low Temperature Combustion (LTC) conditions. Diesel and e-diesel have shown poor repeatability for the most delayed angle (4 deg aTDC) due to significant cycle-to-cycle variations. GTL has shown a heat release rate pattern typical of conventional diesel combustion for all the <em>SOI</em> values, while diesel and e-diesel show fully premixed combustion for delayed <em>SOI </em>(from 4 deg bTDC). A delay of <em>SOI</em> causes a decrease in the brake thermal efficiency and an increase in THC and CO emissions, the latter being more important when e-diesel is used. While late injection seems to considerably improve NOx emissions, no benefits have been obtained for diesel particles, maybe due to the low engine torque tested (which causes the soot production rate to be more significant than the oxidation rate). The low autoignition tendency together with the high volatility of ethanol makes e-diesel as a promising fuel to achieve LTC conditions while keeping acceptable fuel consumption and CO/THC emissions.</p> </div> <p>&nbsp;</p>


Author(s):  
Stephen M. Walton ◽  
Carlos Perez ◽  
Margaret S. Wooldridge

Ignition studies of two small esters were performed using a rapid compression facility (RCF). The esters (methyl butanoate and butyl methanoate) were chosen to have matching molecular weights, and C:H:O ratios, while varying the lengths of the constituent alkyl chains. The effect of functional group size on ignition delay time was investigated using pressure time-histories and high speed digital imaging. The mixtures studied covered a range of conditions relevant to oxygenated fuels and fuel additives, including bio-derived fuels. Low temperature and moderate pressure conditions were selected for study due to their relevance to advanced low temperature combustion strategies, and internal combustion engine conditions. The results are discussed in terms of the reaction pathways affecting the ignition properties.


Author(s):  
Yilu Lin ◽  
Han Wu ◽  
Karthik Nithyanandan ◽  
Timothy H. Lee ◽  
Chia-fon F. Lee ◽  
...  

Bio-butanol, a promising alternative transportation fuel, has its industrial-scale production hindered significantly by high cost component purification process from acetone-butanol-ethanol (ABE) broth. The purpose of this study is to investigate the possibility of using ABE-Diesel blends with high ABE percentages as an alternative transportation fuel. An optical-accessible constant volume chamber capable of controlling ambient temperature, pressure and oxygen concentration was used to mimic the environmental conditions inside a real diesel engine cylinder. ABE fuel with typical volumetric ratios of 30% acetone, 60% butanol and 10% ethanol were blended with ultra-low sulfur diesel at 80% vol. and were tested in this study. The ambient temperature was set to be at 1100K and 900K, which represents normal combustion conditions and low temperature combustion conditions respectively. The ambient oxygen concentrations were set to be at 21%, 16% and 11%, representing different EGR ratios. The in-cylinder pressure was recorded by using a pressure transducer and the time-resolved Mie-scattering image and natural flame luminosity was captured using a high-speed camera coupled with a copper vapor laser. The results show that the liquid penetration is reduced by the high percentage of ABE in the blends. At the same time, the soot formation is reduced significantly by increasing oxygen content in the ABE fuel. Even more interesting, a soot-free combustion was achieved by combining the low temperature combustion with the higher percentage ABE case. In terms of soot emission, high ABE ratio blends are a very promising alternative fuel to be directly used in diesel engines especially under low-temperature combustion conditions.


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