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Is the “K Value” of an Engine Truly Fuel Independent?

Shell Global Solutions (UK)-Roger Cracknell
Nissan Motor Co., Ltd.-Masaharu Kassai, Taisuke Shiraishi
  • Technical Paper
  • 2020-01-0615
To be published on 2020-04-14 by SAE International in United States
The octane appetite of an engine is frequently characterised by the so-called K value. It is usually assumed that K is dependent only on the thermodynamic conditions in the engine when knock occurs. In this work we test this hypothesis: further analysis was conducted on experimental results from SAE 2019-01-0035 in which a matrix of fuels was tested in a single cylinder engine. The fuels consisted of a relatively small number of components, thereby simplifying the analysis of the chemical kinetic proprieties.Through dividing the original fuel matrix into subsets, it was possible to explore the variation of K value with fuel properties. It was found that K value tends to increase slightly with RON. The explanation for this finding is that higher RON leads to advanced ignition timing (i.e. closer to MBT conditions) and advanced ignition timing results in faster combustion because of the higher pressures and temperatures reached in the thermodynamic trajectory. The Livengood-Wu integral can be employed to show that for higher octane fuels, knock onset occurs at a higher temperature and pressure.…
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Impact of fuel octane quality on various advanced vehicle technologies

Shell Global Solutions (UK)-Alastair Smith
Shell Global Solutions (Deutschland)-Caroline Magdalene Zinser, Patrick Haenel
  • Technical Paper
  • 2020-01-0619
To be published on 2020-04-14 by SAE International in United States
Fuel with higher octane content is playing a key role in optimising engine performance by allowing a more optimal spark timing which leads to increased engine efficiency and lower CO2 emissions. In a previous study the impact of octane was investigated with a vehicle fleet of 20 vehicles using market representative fuels, varying from RON 91 to 100. The resulting data showed a clear performance and acceleration benefit when higher RON fuel was used. In this follow-up study 10 more vehicles were added to the database. The vehicle fleet was extended to be more representative of Asian markets, thus broadening the geographical relevance of the database, as well as adding vehicles with newer technologies such as boosted down-sized direct injection engines, or higher compression ratio engines. Eight different fuel combinations varying in RON were tested, representing standard gasoline and premium gasoline in different markets around the world. The new results augment our previously published octane study and result in a vehicle fleet dataset comprising 30 cars from 18 different automotive manufactures. Two key metrics were…
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Assessing the Impact of Lubricant and Fuel Composition on LSPI and Emissions in a Turbocharged Gasoline Direct Injection Engine

Shell Global Solutions (UK)-Robert Mainwaring
FCA US LLC-Andrew Huisjen, Asim Iqbal, Ken Hardman
  • Technical Paper
  • 2020-01-0610
To be published on 2020-04-14 by SAE International in United States
Downsized turbocharged gasoline direct injection (TGDI) engines with high specific power and torque can enable reduced fuel consumption in passenger vehicles while maintaining or even improving on the performance of larger naturally aspirated engines. However, high specific torque levels, especially at low speeds, can lead to abnormal combustion phenomena such as knock or Low-Speed Pre-Ignition (LSPI). LSPI, in particular, can limit further downsizing due to resulting and potentially damaging mega-knock events. Herein, we characterize the impacts of lubricant and fuel composition on LSPI frequency in a TGDI engine while specifically exploring the correlation between fuel composition, particulate emissions, and LSPI events. Our research shows that: (1) oil composition has a strong impact on LSPI frequency and that LSPI frequency can be reduced through a carefully focused approach to lubricant formulation. In addition, (2) we observed significant improvement potential in Brake Mean Effective Pressure (BMEP) achievable with zero LSPI events using both experimental and market-representative lubricant formulations. Finally, (3) fuels blended with high polyaromatic content were shown to increase LSPI frequency significantly; these fuels also caused…
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Effect of Oil Viscosity and Driving Mode on Oil Dilution and Transient Emissions Including Particle Number in Plug-In Hybrid Electric Vehicle

Shell Global Solutions (UK)-Robert Taylor
Shell (Shanghai) Technology Limited-Weizi Li, Tian Jia, Bin Zheng
  • Technical Paper
  • 2020-01-0362
To be published on 2020-04-14 by SAE International in United States
Plug-in electric vehicle (PHEV) has a promising prospect to reduce greenhouse gas (GHG) emission and optimize engine operating in high-efficiency region. According to the maximum electric power and all-electric range, PHEVs are divided into two categories, including “all-electric PHEV” and “blended PHEV” and the latter provides a potential for more rational energy distribution because engine participates in vehicle driving during aggressive acceleration not just by motor. However, the frequent use of engine may result in severe emissions especially in low state of charge (SOC) and ahead of catalyst light-off. This study quantitatively investigates the impact of oil viscosity and driving mode (hybrid/conventional) on oil dilution and emissions including particle number (PN). Two cycles, WLTC (World-wide Harmonized Light Duty Driving Test Cycle) and continuous ECE 15 (European Driving Cycle), were adopted and initial SOC was controlled in the range of 10-13%, which can induce more engine start events. Oil dilution is detected through method of ASTM D3525-04 to identify dilution rate under different conditions. Results show that both in WLTC and ECE 15, frequent engine start…
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An Efficient, High-Precision Vehicle Testing Procedure to Evaluate the Efficacy of Fuel-Borne Friction Modifier Additives

Shell Global Solutions (UK)-Shuhui Yow, Pauline Ziman, Sue J. Smith
BASF Corporation (USA)-Robert J. Bacchi
  • Technical Paper
  • 2019-01-2353
Published 2019-12-19 by SAE International in United States
Improved fuel economy is increasingly a key measure of performance in the automotive industry driven by market demands and tighter emissions regulations. Within this environment, one way to improve fuel economy is via fuel additives that deliver friction- reducing components to the piston-cylinder wall interface. Whilst the use of friction modifiers (FMs) in fuel or lubricant additives to achieve fuel economy improvements is not new, demonstrating the efficacy of these FMs in vehicles is challenging and requires statistical design together with carefully controlled test conditions. This paper describes a bespoke, efficient, high-precision vehicle testing procedure designed to evaluate the fuel economy credentials of fuel-borne FMs. By their nature, FMs persist on engine surfaces and so their effects are not immediately reversible upon changing to a non FM-containing fuel (“carryover” effect), therefore requiring careful design of the test programme. The solution presented here comprises a one-day chassis dynamometer test, internally referencing the fuel economy of an FM- containing test fuel to an FM-free reference fuel. When incorporated into a statistically designed test programme, two or more…
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Lubricant Impact on Friction by Engine Component: A Motored Friction Tear Down Assessment of a Production 3.6L Engine

Shell Global Solutions (UK)-Robert Mainwaring
Ricardo Inc.-Stephen Cakebread
  • Technical Paper
  • 2019-01-2239
Published 2019-12-19 by SAE International in United States
Worldwide, Fuel Economy (FE) legislation increasingly influences vehicle and engine design, and drives friction reduction. The link between lubricant formulation and mechanical friction is complex and depends on engine component design and test cycle. This Motored Friction Tear Down (MFTD) study characterizes the friction within a 3.6L V6 engine under operating conditions and lubricant choices relevant to the legislated FE cycles. The high-fidelity MFTD results presented indicate that the engine is a low-friction engine tolerant of low viscosity oils. Experiments spanned four groups of engine hardware (reciprocating, crankshaft, valvetrain, oil pump), five lubricants (four candidates referenced against an SAE 0W-20) and five temperature regimes. The candidate lubricants explored the impact of base oil viscosity, viscosity modifier (VM) and friction modifier (FM) content. The results indicate that (i) a prototype SAE 0W-8 fluid generated the largest overall reduction in friction, (ii) the valvetrain group responded well to FM content, and (iii) an SAE 0W-20 with alternative VM performed remarkably well at low temperatures (-7°C to 30°C). In order to understand the significance of that engine friction…
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Understanding the Adverse Effects of Inlet Valve Deposits on SI Engine Operation, through a Novel Technique to Create Surrogate Deposits

Shell Global Solutions (UK)-Pauline R. Ziman, Adrian P. Groves
Shell (Shanghai) Technology Ltd.-Kaihua Wu
Published 2018-09-10 by SAE International in United States
For gasoline spark ignition engines, port fuel injection (PFI) on a global basis remains the most common type of fuel delivery. When operated with lower quality fuels and lubricants, PFI engines are prone to suffering from the build-up of harmful deposits on critical engine parts including the inlet valves. High levels of inlet valve deposits (IVDs) have been associated with drivability issues like engine stumble and hesitation on sudden acceleration. Fuels formulated with the appropriate level of deposit control additive (DCA) can maintain engine cleanliness and even remove deposits from critical components.This study, involving a single cylinder research bench engine operated in PFI injection mode and heavily augmented with measurement equipment, aimed to gain a deeper understanding of the detrimental impacts of IVDs on engine efficiency and performance. Guided by 3D-scans of carbonaceous IVDs sourced from industry standard tests conducted per ASTM D5500, surrogate metal deposits were generated, utilizing the novel approach of powder-laser-cladding (PLC). The modified inlet valves were evaluated in the research engine across eight different speed load conditions including full-load. Using this…
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Investigation of Late Stage Conventional Diesel Combustion - Effect of Additives

Shell Global Solutions (UK)-Caroline Wakefield, Mark Brewer, Roger Cracknell
Eindhoven University of Technology-P.C. Bakker, Robbert Willems, Nico Dam, Bart Somers
Published 2018-09-10 by SAE International in United States
The accepted model of conventional diesel combustion [1] assumes a rich premixed flame slightly downstream of the maximum liquid penetration. The soot generated by this rich premixed flame is burnt out by a subsequent diffusion flame at the head of the jet. Even in situations in which the centre of combustion (CA50) is phased optimally to maximize efficiency, slow late stage combustion can still have a significant detrimental impact on thermal efficiency.Data is presented on potential late-stage combustion improvers in a EURO VI compliant HD engine at a range of speed and load points. The operating conditions (e.g. injection timings, EGR levels) were based on a EURO VI calibration which targets 3 g/kWh of engine-out NOx. Rates of heat release were determined from the pressure sensor data. To investigate late stage combustion, focus was made on the position in the cycle at which 90% of the fuel had combusted (CA90).An EN590 compliant fuel was tested. To this fuel was added an organic compound, commonly encountered in sunscreen products, that was designed to absorb ultraviolet light.…
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Impact of Demanding Low Temperature Urban Operation on the Real Driving Emissions Performance of Three European Diesel Passenger Cars

Shell Global Solutions (UK)-Rod Williams, Pauline Ziman
Concawe, Belgium-Heather Hamje
Published 2018-09-10 by SAE International in United States
In Europe, the development and implementation of new regulatory test procedures including the chassis dynamometer (CD) based World Harmonised Light Duty Test Procedure (WLTP) and the Real Driving Emissions (RDE) procedure, has been driven by the close scrutiny that real driving emissions and fuel consumption from passenger cars have come under in recent times. This is due to a divergence between stated certification performance and measured on-road performance, and has been most pointed in the case of NOx (oxides of nitrogen) emissions from diesel cars. The RDE test is certainly more relevant than CD test cycles, but currently certification RDE cycles will not necessarily include the most extreme low speed congested or low temperature conditions which are likely to be more challenging for NOx after-treatment systems. To build understanding of the emissions and fuel consumption performance of the latest available diesel passenger cars, Concawe has conducted a study of the performance of three vehicle types. Two of the vehicles featured urea-dosed Selective Catalytic Reduction (SCR) after-treatment, whilst the third was fitted with a Lean NOx…
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Factors Affecting Test Precision in Latest Vehicle Technologies

Shell Global Solutions (UK)-Michael Gee, Rod Williams
No Affiliation-Keeley Burke
Published 2018-04-03 by SAE International in United States
Demonstrating the cost/benefits of technologies in the automotive sector is becoming very challenging because the benefits from technologies are sometimes of similar magnitude to testing precision. This paper aims to understand vehicle-borne imprecision and the effect of this on the quality of chassis dynamometer (CD) testing. Fuel consumption and NOx emissions precision is analyzed for two diesel vehicles with particulate filter and SCR systems. The two vehicles were tested on a high precision CD facility over the NEDC (New European Drive Cycle) and WLTC (World harmonized Light-duty Test Cycle) cycles. The CD base precision of testing was characterized between 0.6-3% depending on the cycle phase. A novel application of multi-variate statistical analysis was used to identify the factors that affected testing precision, allowing isolation of small differences that were not obvious when conducting cycle-averaged or cycle-phase-averaged analysis. One of the vehicles was particularly sensitive to the vehicle warm-up rate which caused significant variations in catalyst light-off strategy within the engine management system (EMS). This was seen to cause up to 2.3% variability in fuel consumption.…
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