Dilution Effects on the Controlled Auto-Ignition (CAI) Combustion of Hydrocarbon and Alcohol Fuels

Oakley, Aaron J.; Zhao, Hua; Ladommatos, Nicos; Ma, Tom

doi:10.4271/2001-01-3606

Cited by 71 publications

(46 citation statements)

References 18 publications

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“…In the previous study, Christensn et al [6] compared ethanol with gasoline in a high compression ratio HCCI engine and demonstrated the high load limit that could be achieved with ethanol. Oakely et al [7] have shown that methanol and ethanol could be operated in CAI combustion mode over a wider range of relative air/fuel ratios and EGR concentrations than gasoline in a single cylinder engine with elevated intake charge temperature. Iida [8] conducted experimental studies of CAI combustion in a two-stroke ATAC engine and found that methanol provided larger range of CAI combustion than gasoline.…”

Section: Introductionmentioning

confidence: 99%

Combustion Characteristics of CAI Combustion with Alcohol Fuels

Tongroon

Zhao

2010

SAE Technical Paper Series

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Due to its potential for simultaneous improvement in fuel consumption and exhaust emissions, controlled autoignition (CAI) combustion has been subject to continuous research in the last several years. At the same time, there has been a lot of interest in the use of alternative fuels in order to reduce reliance on conventional fossil fuels. Therefore, this experimental study has been carried out to investigate the effect of alcohol fuels on the CAI combustion process and on the resulting engine performance.The experimental work was conducted on an optical single cylinder engine with an air-assisted injector. To achieve controlled autoignition, residual gas was trapped in the cylinder by using negative valve overlap and an intake air heater was used to ensure stable CAI combustion in the optical engine. Methanol, ethanol and blended fuels were tested and compared with the results of gasoline. The combustion processes were analysed through total chemiluminescence images captured with a high speed camera equipped with an intensifier. In addition, the effect of spark discharge was investigated.The images show that CAI combustion of alcohol fuels was characterized with fast and early autoignition combustion compared with pure gasoline. Chemiluminescence of the gasoline fuel was most visible and it decreased with increasing percentage of oxygenated fuels. During the re-compression stroke, chemiluminescence images of the gasoline engine indicated the presence of oxidation reactions. In the presence of spark discharge, the location of charge ignition was dominated by spark discharge at the center of cylinder while simultaneous autoignition sites were found around the periphery of the combustion chamber for nonspark-assisted ignition.

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Section: Introductionmentioning

confidence: 99%

Combustion Characteristics of CAI Combustion with Alcohol Fuels

Tongroon

Zhao

2010

SAE Technical Paper Series

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“…Oakley et al [9,10] extended the investigation by performing detailed analysis of the heat release characteristics of the CAI combustion process in a 4-stroke gasoline engine. They found that the conventional Octane number is inadequate to describe the autoignition behaviour of fuels in a CAI engine.…”

Section: Introductionmentioning

confidence: 99%

“…Higher compression ratio will assist fuel to autoignite, but it leads to knocking combustion at higher load conditions, limiting the maximum power output of the engine. Some fuels, such as alcohol fuels [10], have shown to be superior to others, but a dual fuelled engine requires additional fuelling systems and adds more complexity to engine control, making them unsuited for automotive applications.…”

Section: Introductionmentioning

confidence: 99%

Performance and Analysis of a 4-Stroke Multi-Cylinder Gasoline Engine with CAI Combustion

Zhao

Jian

et al. 2002

SAE Technical Paper Series

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166

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Controlled Auto-Ignition (CAI) combustion was realised in a production type 4-stroke 4-cylinder gasoline engine without intake charge heating or increasing compression ratio. The CAI engine operation was achieved using substantially standard components modified only in camshafts to restrict the gas exchange processThe engine could be operated with CAI combustion within a range of load (0.5 to 4 bar BMEP) and speed (1000 to 3500 rpm). Significant reductions in both specific fuel consumption and CO emissions were found. The reduction in NOx emission was more than 93% across the whole CAI range. Though unburned hydrocarbons were higher under the CAI engine operation.In order to evaluate the potential of the CAI combustion technology, the European NEDC driving cycle vehicle simulation was carried out for two identical vehicles powered by a SI engine and a CAI/SI hybrid engine, respectively. The simulation results showed only moderate improvement in fuel economy and exhaust emissions because of low utilisation of CAI during the drive cycle.In order to take full advantage of the CAI combustion technology, detailed analyses were carried out on the engine's performance, heat release and combustion characteristics, emissions and the effect of gas exchange processes. These analyses showed that the engine's performance and emissions were mainly affected by the trapped residual fractions and residual temperature. In addition, the backflow was found to affect the combustion and emission as well.

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“…Methanol has been chosen as fuel because of the resulting feasible computational effort. Additionally, it should be mentioned that methanol is of interest as an alternative fuel [30,31].…”

Section: Introductionmentioning

confidence: 99%

The ignition of methanol droplets in a laminar convective environment

Stauch

Maas

2008

Combustion and Flame

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Numerical simulations of the ignition of methanol droplets in a laminar convective environment are performed using detailed reaction mechanisms and detailed transport models. The flow velocities of the forced convection ranges from 0.01 up to 5 m/s, whereas the ambient gas temperature is varied between 1300 and 1500 K. The ignition delay time of a single droplet is found to decrease with increasing velocity of the convective gas flow. This decrease is attributed to the steepening of the spatial gradients of the profiles of physical variables, such as species mass fractions or temperature. This steepening is originated by a stronger gas flow and leads to a speed-up of the physical transport processes. For the studied flow conditions, an acceleration of the gas flow on the order of the gravitational acceleration does not show a significant influence on the ignition delay time. A downstream movement of the local ignition point with increasing flow velocity is observed. For higher flow velocities, an ignition in the wake of the droplet followed by an upstream flame propagation is found. After ignition, the formation of an envelope flame is detected. The structure of this envelope flame is studied.

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Dilution Effects on the Controlled Auto-Ignition (CAI) Combustion of Hydrocarbon and Alcohol Fuels

Cited by 71 publications

References 18 publications

Combustion Characteristics of CAI Combustion with Alcohol Fuels

Combustion Characteristics of CAI Combustion with Alcohol Fuels

Performance and Analysis of a 4-Stroke Multi-Cylinder Gasoline Engine with CAI Combustion

The ignition of methanol droplets in a laminar convective environment

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