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Effect of Octane Number on the Performance of Euro 5 and Euro 6 Gasoline Passenger Cars

BP International Ltd.-John Williams
Concawe-Heather D. Hamje, David J. Rickeard
Published 2017-03-28 by SAE International in United States
Research Octane Number (RON) and Motor Octane Number (MON) are used to describe gasoline combustion which describe antiknock performance under different conditions. Recent literature suggests that MON is less important than RON in modern cars and a relaxation in the MON specification could improve vehicle performance. At the same time, for the same octane number change, increasing RON appears to provide more benefit to engine power and acceleration than reducing MON. Some workers have advocated the use of an octane index (OI) which incorporates both parameters instead of either RON or MON to give an indication of gasoline knock resistance. Previous Concawe work investigated the effect of RON and MON on the power and acceleration performance of two Euro 4 gasoline passenger cars during an especially-designed acceleration test cycle. A large number of fuels blended with and without oxygenates and ranging from around 95 to 103 RON and sensitivities (RON minus MON) up to around 15 were tested. The results were vehicle dependent but in general, showed that sensitivity and octane index appear to be…
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Influence of Different Fuel Properties and Gasoline - Ethanol Blends on Low-Speed Pre-Ignition in Turbocharged Direct Injection Spark Ignition Engines

SAE International Journal of Engines

BP International Ltd.-John Williams, James Moss
Vienna University of Technology-Mattias Mayer, Peter Hofmann, Bernhard Geringer
  • Journal Article
  • 2016-01-0719
Published 2016-04-05 by SAE International in United States
In recent years a new combustion phenomenon called Low-Speed Pre-Ignition (LSPI) occurred, which is the most important limiting factor to exploit further downsizing potential due to the associated peak pressures and thus the huge damage potential. In the past there were already several triggers for pre-ignitions identified, whereat engine oil seems to have an important influence. Other studies have reported that detached oil droplets from the piston crevice volume lead to auto-ignition prior to spark ignition. However, wall wetting and subsequently oil dilution and changes in the oil properties by impinging fuel on the cylinder wall seem to have a significant influence in terms of accumulation and detachment of oil-fuel droplets in the combustion chamber. For this reason, the influence of test fuels with different volatility were investigated in order to verify their influence on wall wetting, detachment and pre-ignition tendency. During these investigations also different ethanol fuels were investigated to analyse the influence of various alcohol blends on pre-ignitions.
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The Effect of Combustion Knock on the Instantaneous Heat Flux in Spark Ignition Engines

BP International Ltd.-John Williams
University of Oxford-Johannes Mutzke, Blane Scott, Richard Stone
Published 2016-04-05 by SAE International in United States
Knocking combustion places a major limit on the performance and efficiency of spark ignition engines. Spontaneous ignition of the unburned air-fuel mixture ahead of the flame front leads to a rapid release of energy, which produces pressure waves that cause the engine structure to vibrate at its natural frequencies and produce an audible ‘pinging’ sound. In extreme cases of knock, increased temperatures and pressures in the cylinder can cause severe engine damage.Damage is thought to be caused by thermal strain effects that are directly related to the heat flux. Since it will be the maximum values that are potentially the most damaging, then the heat flux needs to be measured on a cycle-by-cycle basis. Previous work has correlated heat flux with the pressure fluctuations on an average basis, but the work here shows a correlation on a cycle-by-cycle basis.The in-cylinder pressure and surface temperature were measured using a pressure transducer and eroding-type thermocouple. These sensors were installed side-by-side at the surface of the cylinder in order to investigate the relationship between knock and heat flux…
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Influence of Different Oil Properties on Low-Speed Pre-Ignition in Turbocharged Direct Injection Spark Ignition Engines

AVL LIST GmbH-Paul Kapus
BP International Ltd.-John Williams, James Moss
Published 2016-04-05 by SAE International in United States
In recent years concern has arisen over a new combustion anomaly, which was not commonly associated with naturally aspirated engines. This phenomenon referred to as Low-Speed Pre-Ignition (LSPI), which often leads to potentially damaging peak cylinder pressures, is the most important factor limiting further downsizing and the potential CO2 benefits that it could bring. Previous studies have identified several potential triggers for pre-ignition where engine oil seems to have an important influence. Many studies [1], [2] have reported that detached oil droplets from the piston crevice volume lead to auto-ignition prior to spark ignition. Furthermore, wall wetting and subsequently oil dilution [3] and changes in the oil properties by impinging fuel on the cylinder wall seem to have a significant influence in terms of accumulation and detachment of oil-fuel droplets in the combustion chamber. For this reason the interaction of fuel and engine oil at the combustion chamber walls was investigated in a comprehensive parameter variation. During these investigations the parameters oil temperature, start of injection and injection strategy were varied. Other studies [4], [5]…
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Effect of Octane on the Performance of Two Gasoline Direct Injection Passenger Cars

BP International Ltd-John Williams
Concawe-David Rickeard, Heather Hamje
Published 2015-04-14 by SAE International in United States
The performance aspect of gasoline combustion has traditionally been measured using Research Octane Number (RON) and Motor Octane Number (MON) which describe antiknock performance under different conditions. Recent literature suggests that MON is less important than RON in modern cars and a relaxation in the MON specification could improve vehicle performance, while also helping refiners in the production of gasoline. At the same time, for the same octane number change, increasing RON appears to provide more benefit to engine power and acceleration than reducing MON. It has also been suggested that there could be fuel efficiency benefits (on a tank to wheels basis) for specially adapted engines, for example, operating at higher compression ratio, on very high RON (100+). Other workers have advocated the use of an octane index (OI) which incorporates both RON and MON to give an indication of octane quality.The objective of this study was to investigate the effect of RON and MON on the power and acceleration performance of two Euro 4 gasoline vehicles under full throttle acceleration conditions. Fifteen fuels…
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CO2 Emission Reduction Synergies of Advanced Engine Design and Fuel Octane Number

BP International Ltd.-Ben Leach, Richard Pearson, Rana Ali, John Williams
Published 2014-10-13 by SAE International in United States
Engine downsizing is a key approach employed by many vehicle manufacturers to help meet fleet average CO2 emissions targets. With gasoline engines in particular reducing engine swept volume while increasing specific output via technologies such as turbocharging, direct injection (DI) and variable valve timing can significantly reduce frictional and pumping losses in engine operating areas commonly encountered in legislative drive cycles.These engines have increased susceptibility to abnormal combustion phenomena such as knock due to the high brake mean effective pressures which they generate. This ultimately limits fuel efficiency benefits by demanding use of a lower geometric compression ratio and sub-optimal late combustion phasing at the higher specific loads experienced by these engines. The lower expansion ratio and retarded combustion in turn increase the exhaust gas temperature, which often leads to a need to add extra fuel that cannot be fully combusted in order to cool and protect engine components from thermal damage. Optimizing the engine design for use with a fuel with an increased research octane number (RON) allows the adoption of a higher compression…
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Lubricant Induced Pre-Ignition in an Optical SI Engine

BP International Ltd.-John Williams, Oliver Williams, Rana Ali
Brunel Univ.-Simon F. Dingle, Alasdair Cairns, Hua Zhao
Published 2014-04-01 by SAE International in United States
This work was concerned with study of lubricant introduced directly into the combustion chamber and its effect on pre-ignition and combustion in an optically accessed single-cylinder spark ignition engine. The research engine had been designed to incorporate full bore overhead optical access capable of withstanding peak in-cylinder pressures of up to 150bar. An experiment was designed where a fully formulated synthetic lubricant was deliberately introduced through a specially modified direct fuel injector to target the exhaust area of the bore. Optical imaging was performed via natural light emission, with the events recorded at 6000 frames per second. Two port injected fuels were evaluated including a baseline commercial grade gasoline and low octane gasoline/n-heptane blend. The images revealed the location of deflagration sites consistently initiating from the lubricant itself. With the high octane fuel (and the limited load adopted for safe optical work) lubricant induced pre-ignition was observed, but without knock. This pre-ignition was repeatedly the result of the lubricant deliberately introduced earlier on in the same cycle. With the lower octane fuel, the previously well…
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Impact of Lubricant Composition on Low-speed Pre-Ignition

BP International Ltd.-John Williams, James Moss
University of Cambridge-Orian Welling, Nick Collings
Published 2014-04-01 by SAE International in United States
One of the limits on the maximum fuel efficiency benefit to be gained from turbocharged, downsized gasoline engines is the occurrence of pre-ignitions at low engine speed. These pre-ignitions may lead to high pressures and extreme knock (megaknock or superknock) which can cause severe engine damage. Though the mechanism leading to megaknock is not completely resolved, pre-ignitions are thought to arise from local autoignition of areas in the cylinder which are rich in low ignition delay “contaminants” such as engine oil and/or heavy ends of gasoline. These contaminants are introduced to the combustion chamber at various points in the engine cycle (e.g. entering from the top land crevice during blow-down or washed from the cylinder walls during DI wall impingement).This paper presents results from tests in which model “contaminants”, consisting of engine lubricant base stocks, base stocks mixed with fuel and base stocks mixed with one or more additives were injected directly into a test engine to determine their propensity to ignite. The ignition tendency was found to be lower for less reactive base stocks…
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Measuring the Impact of Engine Oils and Fuels on Low-Speed Pre-Ignition in Downsized Engines

SAE International Journal of Fuels and Lubricants

BP International Ltd-James Moss, John Williams
University of Cambridge-Orian Welling, Nick Collings
  • Journal Article
  • 2014-01-1219
Published 2014-04-01 by SAE International in United States
One of the limits on the maximum fuel efficiency benefit to be gained from turbocharged, downsized gasoline engines is the occurrence of low speed pre-ignition (LSPI). LSPI may lead to high pressures and extreme knock (megaknock or superknock) which can cause severe engine damage. Though the mechanism leading to megaknock is not completely resolved, LSPI is thought to arise from local auto-ignition of areas in the cylinder which are rich in low ignition delay “contaminants” such as engine oil and/or heavy ends of gasoline. These contaminants are introduced to the combustion chamber at various points in the engine cycle (e.g. entering from the top land crevice during blow-down or washed from the cylinder walls during DI wall impingement).This paper describes a method for testing the propensity of different contaminants to cause a local pre-ignition in a gasoline engine. During one cycle, a small amount of contaminant is injected into one cylinder of a 4 cylinder engine. The spark is suppressed during this or the following cycle to allow detection of local pre-ignition events after spark…
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Evaluating Synergies between Fuels and Near Term Powertrain Technologies through Vehicle Drive Cycle and Performance Simulation

BP International Ltd-John Williams, Rana Ali
Mahle Powertrain Ltd-Andre Bisordi, Dave OudeNijeweme, Michael Bassett, Philip Stansfield
Published 2012-04-16 by SAE International in United States
The main focus nowadays for the development of future vehicle powertrain systems is the improvement in fuel efficiency alongside the reduction of pollutant emissions and greenhouse gasses, most notably carbon dioxide.The automotive community is already engaged in seeking solutions to these issues, however, the ideal solution, namely zero emission vehicle is still regarded as being a long way from fruition for the mass market. In the meantime steps are being taken, in terms of engineering development, towards improved fuel efficiency and sustainability of relatively conventionally powered vehicles.One approach to the decarbonization of road vehicles is to supplement existing fossil fuels with sustainable biofuels.The present study examines the effect of a variety of gasoline/alcohol fuel blends on the performance of spark ignition engine vehicles and the potential of suitable "near to market" technology, using a combination of dynamometer measurements for a high technology downsized engine, running on a variety of fuel blends, and a detailed vehicle simulation model. Fuel consumption, and hence CO₂ emissions, results are presented for the technology and fuel combinations over a number…
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