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Visual Analyses of End of Injection Liquid Structures and the Behaviour of Nozzle Surface-Bound Fuel in a Direct Injection Diesel Engine

BP International Ltd.-Martin Gold, Richard Pearson
University of Brighton-Dan Sykes, Guillaume de Sercey, Cyril Crua
Published 2019-01-15 by SAE International in United States
For efficiency, the majority of modern diesel engines implement multiple injection strategies, increasing the frequency of transient injection phases and thus, end of injection (EOI) events. Recent advances in diagnostic techniques have identified several EOI phenomena pertinent to nozzle surface wetting as a precursor for deposit formation and a potential contributor towards pollutant emissions. To investigate the underlying processes, highspeed optical measurements at the microscopic scale were performed inside a motored diesel engine under low load/idling conditions. Visualisation of the injector nozzle surface and near nozzle region permitted an indepth analysis of the post-injection phenomena and the behaviour of fuel films on the nozzle surface when the engine is not fired. Inspection of the high-speed video data enabled an interpretation of the fluid dynamics leading to surface wetting, elucidating the mechanisms of deposition and spreading. As the needle re-seated, the abrupt pressure drop inhibited atomisation. Large, slow moving, liquid structures were released into the cylinder with the capability of impinging on nearby surfaces, creating localised fuel rich regions, or escaping through the exhaust and contributing…
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Fast NGC: A New On-Line Technique for Fuel Flow Measurement

BP International Ltd.-Martin Gold, Richard Pearson
University of Oxford-Felix Leach, Martin Davy, Manus Henry, Maruthi Rochishnu Malladi, Michael Tombs, Feibiao Zhou
Published 2019-01-15 by SAE International in United States
Knowledge of fuel mass injected in an individual cycle is important for engine performance and modelling. Currently direct measurements of fuel flow to individual cylinders of an engine are not possible on-engine or in real-time due to a lack of available appropriate measurement techniques. The objective of this work was to undertake real-time Coriolis fuel flow measurement using GDI injectors on a rig observing fuel mass flow rate within individual fuel injections. This paper evaluates the potential of this technology - combining Coriolis Flow Meters (CFMs) with Prism signal processing together known as Fast Next Generation Coriolis (Fast NGC), and serves as a basis for future transitions on-engine applications. A rig-based feasibility study has been undertaken injecting gasoline through a GDI injector at 150 bar in both single shot mode and at a simulated engine speeds of 1788 and 2978 rpm. The results show that these injections can, in principle, be observed. In addition a number of features of the Fast NGC system unique to gasoline are discussed, and the repeatability of the technique is preliminarily assessed.…
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Simulation and Measurement of Transient Fluid Phenomena within Diesel Injection

SAE International Journal of Advances and Current Practices in Mobility

BP International Ltd.-Martin Gold, Richard Pearson
City University London-Mithun Murali-Girija, Foivos Koukouvinis, Manolis Gavaises
  • Journal Article
  • 2019-01-0066
Published 2019-01-15 by SAE International in United States
Rail pressures of modern diesel fuel injection systems have increased significantly over recent years, greatly improving atomisation of the main fuel injection event and air utilisation of the combustion process. Continued improvement in controlling the process of introducing fuel into the cylinder has led to focussing on fluid phenomena related to transient response. High-speed microscopy has been employed to visualise the detailed fluid dynamics around the near nozzle region of an automotive diesel fuel injector, during the opening, closing and post injection events. Complementary computational fluid dynamic (CFD) simulations have been undertaken to elucidate the interaction of the liquid and gas phases during these highly transient events, including an assessment of close-coupled injections.Microscopic imaging shows the development of a plug flow in the initial stages of injection, with rapid transition into a primary breakup regime, transitioning to a finely atomised spray and subsequent vaporisation of the fuel. During closuring of the injector the spray collapses, with evidence of swirling breakup structures together with unstable ligaments of fuel breaking into large slow-moving droplets. This leads to…
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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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Reduction of CO2 Emissions through Lubricant Thermal Management During the Warm Up of Passenger Car Engines

BP International Ltd.-Richard Pearson
BP International Ltd., Univ. of Oxford-Oliver P. Taylor
Published 2016-04-05 by SAE International in United States
Most major regional automotive markets have stringent legislative targets for vehicle greenhouse gas emissions or fuel economy enforced by fiscal penalties. Large improvements in vehicle efficiency on mandated test cycles have already taken place in some markets through the widespread adoption of technologies such as downsizing or dieselisation. There is now increased focus on approaches which give smaller, but significant incremental efficiency benefits, such as reducing parasitic losses due to engine friction.The reduction in tail pipe CO2 emissions through the reduction of engine friction using lubricants has been reported by many authors. However, opportunities also exist to reduce the lubricant viscosity during warm up by the thermal management of the lubricant mass. This presents an attractive proposition to vehicle manufacturers because of the favorable cost-benefit ratios of thermal management systems and because this strategy can achieve some of the benefits that ordinarily require the lubricant viscosity grade to be lowered.In this paper the experimental results from chassis dynamometer tests are analysed. The performance of two modern vehicles was determined using various lubricant thermal management strategies,…
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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

BP International Ltd.-John Williams, James Moss
AVL LIST GmbH-Paul Kapus
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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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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Tribological Behavior of Low Viscosity Lubricants in the Piston to Bore Zone of a Modern Spark Ignition Engine

BP International Ltd.-Richard Pearson
BP International Ltd. / University of Oxford-Oliver P. Taylor
Published 2014-10-13 by SAE International in United States
Most major regional automotive markets have stringent legislative targets for vehicle greenhouse gas emissions or fuel economy enforced by fiscal penalties. Large improvements in vehicle efficiency on mandated test cycles have already taken place in some markets through the widespread adoption of technologies such as downsizing or dieselization. There is now increased focus on approaches which give smaller but significant incremental efficiency benefits such as reducing parasitic losses due to engine friction. Fuel economy improvements which achieve this through the development of advanced engine lubricants are very attractive to vehicle manufacturers due to their favorable cost-benefit ratio.For an engine with components which operate predominantly in the hydrodynamic lubrication regime, the most significant lubricant parameter which can be changed to improve the tribological performance of the system is the lubricant viscosity. Low viscosity lubricants are increasingly being specified by vehicle manufacturers who are now more frequently working directly with the lubricant supplier to design fluids specific to their requirements. As lubricant viscosity grades far below those currently in the market are investigated it is vital that…
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