scholarly journals An overview of the effects of fuel molecular structure on the combustion and emissions characteristics of compression ignition engines

2017 ◽  
Vol 232 (1) ◽  
pp. 90-105 ◽  
Author(s):  
Paul Hellier ◽  
Midhat Talibi ◽  
Aaron Eveleigh ◽  
Nicos Ladommatos
Keyword(s):  
Molecular Structure ◽  
Particulate Matter ◽  
Ignition Delay ◽  
Carbon Dioxide Emissions ◽  
Compression Ignition ◽  
Ring Number ◽  
Compression Ignition Engines ◽  
Point Increase ◽  
Particulate Matter Emissions ◽  
Alkyl Moiety

Future fuels for compression ignition engines will be required both to reduce the anthropogenic carbon dioxide emissions from fossil sources and to contribute to the reductions in the exhaust levels of pollutants, such as nitrogen oxides and particulate matter. Via various processes of biological, chemical and physical conversion, feedstocks such as lignocellulosic biomass and photosynthetic micro-organisms will yield a wide variety of potential fuel molecules. Furthermore, modification of the production processes may allow the targeted manufacture of fuels of specific molecular structure. This paper therefore presents an overview of the effects of fuel molecular structure on the combustion and emissions characteristics of compression ignition engines, highlighting in particular the submolecular features common to a variety of potential fuels. An increase in the straight-chain length of the alkyl moiety reduces the duration of ignition delay, and the introduction of double bonds or branching to an alkyl moiety both increase ignition delay. The movement of a double bond towards the centre of an alkyl chain, or the addition of oxygen to a molecule, can both increase and decrease the duration of ignition delay dependent on the overall fuel structure. Nitrogen oxide emissions are primarily influenced by the duration of fuel ignition delay, but in the case of hydrogen and methane pilot-ignited premixed combustion arise only at flame temperatures sufficiently high for thermal production. An increase in aromatic ring number and physical properties such as the fuel boiling point increase particulate matter emissions at constant combustion phasing.

Dilution Sensitivity of Particulate Matter Emissions From Reactivity Controlled Compression Ignition Combustion

2015 ◽  
Author(s):  
Wei Fang ◽  
David B. Kittelson ◽  
William F. Northrop
Keyword(s):  
Particulate Matter ◽  
Diesel Combustion ◽  
Compression Ignition ◽  
Total Particulate Matter ◽  
Reactivity Controlled Compression Ignition ◽  
Carbonaceous Particles ◽  
Relative Contribution ◽  
Particulate Matter Emissions ◽  
Soot Emissions ◽  
Hydrous Ethanol

Dual-fuel reactivity-controlled compression ignition (RCCI) combustion can yield high thermal efficiency and simultaneously low NOx and soot emissions. Although soot emissions from RCCI is very low, hydrocarbon emissions are high, potentially resulting in higher than desired total particulate matter (PM) mass and number caused by semi-volatile species converting the particle phase upon primary dilution in the exhaust plume. Such high organic fraction PM is known to be highly sensitive to the dilution conditions used when collecting samples on a filter or when measuring particle number using particle sizing instruments. In this study, PM emissions from a modified single-cylinder diesel engine operating in RCCI and conventional diesel combustion modes were investigated under different dilution conditions. To investigate the effect of the fumigated fuel on the PM emissions, 150 proof hydrous ethanol and gasoline were used as low reactivity fuels to study the relative contribution of fumigant versus directly injected fuel on the PM emissions. Our study found that PM from RCCI combustion is more sensitive to the variation of dilution conditions than PM from single fuel conventional diesel combustion. RCCI PM primarily consisted of semi-volatile organic compounds and a smaller amount of solid carbonaceous particles. The fumigated fuel had a significant effect on the PM emissions characteristics for RCCI combustion. Hydrous ethanol fueled RCCI PM contained a larger fraction of volatile materials and were more sensitive to the variation of dilution conditions compared to the gasoline fueled RCCI mode.

Experimental Study of Premixed-Charge Compression Ignition Mode in Low Load Fueled With Butanol Isomers and Diesel Binary Fuels in a Common-Rail Diesel Engine

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Zilong Li ◽  
Guan Huang ◽  
Chenxu Jiang ◽  
Yong Qian ◽  
Zhuoyao He ◽  
...  
Keyword(s):  
Experimental Study ◽  
Particulate Matter ◽  
Geometric Mean ◽  
Volume Ratio ◽  
Compression Ignition ◽  
Nox Formation ◽  
Tert Butanol ◽  
Low Load ◽  
Particulate Matter Emissions ◽  
Gas Recirculation

Abstract Low NOx and particulate matter (PM) emissions are simultaneously attempted to implement via an experimental study on diesel/butanol isomers binary fuels in premixed-charge compression ignition (PCCI) mode. N-butanol, iso-butanol, sec-butanol, and tert-butanol were blended with diesel in a certain volume ratio of 0.24:0.76, denoted as N24, I24, S24, and T24, respectively. The indicated thermal efficiency (ITE) of binary fuels in PCCI mode decreases slightly than that in direction injection (DI) mode. T24 obtains higher ITE than the other three test fuels with 50% exhaust gas recirculation (EGR). NOx formation is certainly inhibited more than 60% in PCCI mode, especially when the EGR rate is 50%. PCCI mode produces more CO, HC, and carbonyl emissions than DI mode to varying degrees; under these circumstances, T24 tends to have the lowest emissions among four test fuels, reflecting the potential of tert-butanol as a diesel alternative fuel. Butanol isomers have a vital contribution on particulate matter emissions inhibition for both PM total number and total mass. Tert-butanol tends to form accumulation mode particle, and n-butanol tends to form nucleation mode mainly caused by molecular structure diversity of isomers. The geometric mean diameter of diesel/butanol isomers increases in PCCI mode compared with that in DI mode.

Dilution Sensitivity of Particulate Matter Emissions From Reactivity-Controlled Compression Ignition Combustion

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Wei Fang ◽  
David B. Kittelson ◽  
William F. Northrop
Keyword(s):  
Particulate Matter ◽  
Semivolatile Organic Compounds ◽  
Diesel Combustion ◽  
Compression Ignition ◽  
Total Particulate Matter ◽  
Reactivity Controlled Compression Ignition ◽  
Carbonaceous Particles ◽  
Particulate Matter Emissions ◽  
Soot Emissions ◽  
Hydrous Ethanol

Dual-fuel reactivity-controlled compression ignition (RCCI) combustion can yield high thermal efficiency and simultaneously low NOx and soot emissions. Although soot emissions from RCCI are very low, hydrocarbon (HC) emissions are high, potentially resulting in higher than desired total particulate matter (PM) mass and number caused by semivolatile species converting the particle phase upon primary dilution in the exhaust plume. Such high organic fraction PM is known to be highly sensitive to dilution conditions used when collecting samples on a filter or when measuring particle number using particle sizing instruments. In this study, PM emissions from a modified single-cylinder diesel engine operating in RCCI and conventional diesel combustion (CDC) modes were investigated under controlled dilution conditions. To investigate the effect of the fumigated fuel on the PM emissions, 150 proof hydrous ethanol and gasoline were used as low reactivity fuels. The data reveal that PM from RCCI combustion is more sensitive to the variation of dilution conditions than PM from single fuel conventional diesel combustion. RCCI PM primarily consisted of semivolatile organic compounds and a smaller amount of solid carbonaceous particles. The fumigated fuel had a significant effect on PM emissions' characteristics for RCCI combustion. Hydrous ethanol fueled RCCI PM contained a larger fraction of volatile materials and was more sensitive to the variation of dilution conditions compared to the gasoline fueled RCCI mode.

scholarly journals A comparative experimental study on engine operating on premixed charge compression ignition and compression ignition mode

2017 ◽  
Vol 21 (1 Part B) ◽  
pp. 441-449
Author(s):  
Girish Bhiogade ◽  
Jiwak Suryawanshi
Keyword(s):  
Experimental Study ◽  
Particulate Matter ◽  
Thermal Efficiency ◽  
Direct Injection ◽  
Fuel Mixture ◽  
Exhaust Emission ◽  
Compression Ignition ◽  
Compression Ignition Engine ◽  
Compression Ignition Engines ◽  
Compression Ignition Combustion

New combustion concepts have been recently developed with the purpose to tackle the problem of high emissions level of traditional direct injection Diesel engines. A good example is the premixed charge compression ignition combustion. A strategy in which early injection is used causing a burning process in which the fuel burns in the premixed condition. In compression ignition engines, soot (particulate matter) and NOx emissions are an extremely unsolved issue. Premixed charge compression ignition is one of the most promising solutions that combine the advantages of both spark ignition and compression ignition combustion modes. It gives thermal efficiency close to the compression ignition engines and resolves the associated issues of high NOx and particulate matter, simultaneously. Premixing of air and fuel preparation is the challenging part to achieve premixed charge compression ignition combustion. In the present experimental study a diesel vaporizer is used to achieve premixed charge compression ignition combustion. A vaporized diesel fuel was mixed with the air to form premixed charge and inducted into the cylinder during the intake stroke. Low diesel volatility remains the main obstacle in preparing premixed air-fuel mixture. Exhaust gas re-circulation can be used to control the rate of heat release. The objective of this study is to reduce exhaust emission levels with maintaining thermal efficiency close to compression ignition engine.

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