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The Impact of Low Speed Pre-Ignition on Next Generation Engine Oils

Kristin Fletcher, R&D Scientist at Afton Chemical presented the challenges facing the automotive industry with the phenomena of Low Speed Pre-Ignition (LSPI). She discussed the current legislative challenges facing car manufacturers and new technology that is able to meet those challenges. In addition, she reviewed relevant findings available in the literature demonstrating fuel and lubricant impacts on the frequency of LSPI produced in a test engine.

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The Impact of Low Speed Pre-Ignition on Next Generation Engine Oils

  1. 1. The Impact of Low Speed Pre-Ignition on Next Generation Engine Oils Kristin Fletcher Ashu Gupta Greg Guinther KSTLE 2014
  2. 2. Who We Are! Fuel Additives Gasoline Performance Diesel Performance Lubricity Cetane Improvers Combustion Improvers Octane Improver Finished Fuel Additives Engine Oil Additives Passenger Car Motor Oils HD Diesel Oils Medium Speed Diesel Oil Viscosity Index Improvers Components Driveline & Industrial Transmission Fluids Automotive Gear Hydraulic, Tractor Slideway, Turbine Metalworking Industrial Gear Grease Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  3. 3. What I’m Going to Talk about Today Low Speed Pre-Ignition – LSPI  Current legislative challenges facing car manufacturers  Their technology to meet those challenges  How LSPI affects their technologies  How LSPI occurs  Contributing factors towards LSPI Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  4. 4. Legislative Challenges: Lower CO2 EU Baseline: 142 EU 2020: 95 US Baseline: 219 US 2025:107 Japan Baseline:131 Japan 2020: 105 China Baseline: 185 China 2015: 167 270 250 230 210 190 170 150 130 110 90 2000 2005 2010 2015 2020 2025 CO2 Emissions Normalised to NEDC (g/km) EU US-LDV Japan China 1.9% Annually 3.9% Annually 2% Annually 4.7% Annually (Source: Mahle Powertrain, UK) Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  5. 5. CO2 Enabler The Downsized Gasoline Engine Downsizing replaces larger engines with smaller engines with additional technology  Typically a turbocharger and direct fuel injection Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  6. 6. CO2 Enabler The Downsized Gasoline Engine (Graphs Source: Mahle Powertrain, UK) Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  7. 7. CO2 Enabler The Downsized Gasoline Engine 2.0 litre N/A high-speed engine MAHLE 1.2 litre D/S engine 0 1000 2000 3000 4000 5000 6000 7000 8000 Engine Speed [rev/min] (Graphs Source: Mahle Powertrain, UK) Corrected Torque [Nm] 300 250 200 150 100 50 0 Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  8. 8. CO2 Enabler The Downsized Gasoline Engine Downsizing replaces larger engines with smaller engines with additional technology  Typically a turbocharger and direct fuel injection Downsized engines in conjunction with suitable transmission design give additional fuel economy gains through Downspeeding Downsizing & Downspeeding achieve fuel economy by  Having fewer and smaller parts leading to less heat loss and friction  Direct injection gives a cooling effect to allow high levels of turbocharging  Downspeeding lowers engine friction and pumping losses Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  9. 9. CO2 Enabler The Downsized Gasoline Engine (Graphs Source: Mahle Powertrain, UK) Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  10. 10. How Does this Link to LSPI? Unfortunately, the most fuel efficient area for the engine is also the area where it is most susceptible to LSPI LSPI RISK (Graph Source: Mahle Powertrain, UK) Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  11. 11. How Does this Link to LSPI? Unfortunately, the most fuel efficient area for the engine is also the area where it is most susceptible to LSPI As a result car manufacturers have to tune their engines to avoid LSPI in the affected area Typically achieved by injecting more fuel than necessary – with detrimental effects on fuel economy Therefore LSPI is a limiting factor of fuel economy / CO2 reduction Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  12. 12. The Effect of Auto-Ignition / LSPI (Picture Source: Southwest Research Institute, Tx) Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  13. 13. The Effect of Auto-Ignition / LSPI (Graph Source: Southwest Research Institute, Tx) Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  14. 14. The Effect of Auto-Ignition / LSPI (Pictures Source: Southwest Research Institute, Tx) Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  15. 15. What Could be Causing This? Surface hot spots – LSPI imaging does not show auto-ignition starting from just one point on the surface of the engine [Zadeh et al., Dahnz et al, Palaveev et al.] (Source: Copyright SAE 2014, 2011-01—0340, Zadeh et al) Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  16. 16. What Could be Causing This? Surface hot spots – LSPI imaging does not show auto-ignition starting from just one point on the surface of the engine [Zadeh et al., Dahnz et al, Palaveev et al.] LSPI does not lead to ‘run-away’ pre-ignition LSPI increases with lower coolant temperature – contrary to surface pre-ignition or knock May be due to deposits / particles in the combustion chamber soaked with fuel and oil and hot enough to start combustion Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  17. 17. Proposed Mechanisms for Preignition Possible Mechanisms Release of Oil-Fuel Droplet from Piston Crevice which Auto-Ignites Combustion Chamber Deposits or Particles which Initiate a Flame Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  18. 18. The Oil Droplet Theory Droplets of lubricant and fuel mixed together enter the combustion chamber The inclusion of lubricant lowers the auto-ignition temperature of the droplet [Amann et al., SAE 2012-01-1140] Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  19. 19. Fuel and Lubricant Mixing AIR IN Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  20. 20. Combustible Fuel & Air Mixture Auto-Ignition Velocity Accel. Fuel & Air Crevice Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  21. 21. The Deposit Mechanism Suggests that deposits may flake off, heat up by the exhaust gases and survive the gas-exchange process and induce thermal ignition in the next cycle Mechanism consistent with  Fuel sensitivity (aromatic content and T90)  Lubricant sensitivity (basestock quality, additives)  High-speed visual images SAE 2014-01-1218 Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  22. 22. Why are These Engines Sensitive to LSPI? Spray direction – direct injection engines allows fuel onto cylinder walls Side mounted injectors are worst [Zadeh et al., SAE 2011- 01-1140] Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  23. 23. Why are These Engines Sensitive to LSPI? Spray direction – direct injection engines allows fuel onto cylinder walls Side mounted injectors are worst [Zadeh et al., SAE 2011- 01-1140] Boost pressure – increases combustion chamber temperature [Zadeh et al., SAE 2011-01-1140] Engine speed – lower engine speeds allow more time for the reactive fuel-oil mixture to auto-ignite Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  24. 24. Influence of Fuel Composition RON and MON are not the best indicators for LSPI resistance [Dahnz et al., SAE 2010-01-0355] Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  25. 25. Influence of Fuel Composition RON and MON are not the best indicators for LSPI resistance [Dahnz et al., SAE 2010-01-0355] Less volatile and older fuel can increase LSPI as a larger fraction remains with the lubricant on the cylinder wall High Aromatic content can increase LSPI - even though aromatics are commonly used to achieve octane [Amann et al., SAE 2012-01-1140] Oxygenate content may reduce LSPI – due to their low boiling point, requires further research Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  26. 26. Influence of Base Oil Takeuchi et al. [SAE 2012-01-1615] evaluated different base stocks in a prototype engine  Found higher group numbers correlated with lower LSPI frequency (Source: Copyright SAE 2014, 2012-01—1615, Takeuchi et al.) Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  27. 27. Influence of Lubricant Additives Calcium Higher calcium levels correlate with higher LSPI frequency [Takeuchi et al., 2012-01-1615, Hirano et al., 2013-01-2569] (Source: Copyright SAE 2014, (Source: Copyright SAE 2014, 2013-01-2569, Hirano et al.) 2012-01—1615, Takeuchi et al.) Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  28. 28. Influence of Lubricant Additives Phosphorous and Molybdenum Increasing molybdenum and phosphorus (through ZDDP) levels decreased LSPI frequency [Takeuchi et al., 2012-01-1615] (Source both graphs: Copyright SAE 2014, 2012-01—1615, Takeuchi et al.) Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  29. 29. Lubricant Physical Properties Takeuchi et al. [SAE 2012-01-1615] also evaluated lubricant volatility using the Noack test  There was no clear correlation between lubricant volatility and LSPI (Source: Copyright SAE 2014, 2012-01—1615, Takeuchi et al.) Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  30. 30. Lubricant Physical Properties Takeuchi et al. [SAE 2012-01-1615] also evaluated lubricant oxidative reactivity inferred by auto-ignition temperature  There was a clear correlation between oxidative characteristic and frequency of LSPI DSC = differential scanning calorimeter (Source: Copyright SAE 2014, 2012-01—1615, Takeuchi et al.) Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  31. 31. Wear Metals and Older Oils Hirano et al. [SAE 2013-01-2569] also looked at lubricant effects  Simulated the impact of wear metals using iron and copper • Found that in their presence LSPI frequency increased  Similar to Takeuchi, also found that used oil may have higher LSPI frequency Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  32. 32. Lubricants Require Holistic Formulation Chain Wear LSPI Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  33. 33. LSPI Lube Industry Tests Under Development  ILSAC GF-6 • Ford 2.0L 4-cyl Ecoboost  GM dexos1TM Gen II • GM 2.0L 4-cyl Ecotec Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  34. 34. Afton’s Approach: Technology Driven Solutions Afton are conducting a range of research/testing programs in-house  Fundamental / Basic research for improved understanding of LSPI  Internal engine testing to support research is underway Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  35. 35. Afton’s Approach: Technology Driven Solutions Afton are conducting a range of research/testing programs in-house  Fundamental / Basic research for improved understanding of LSPI  Internal engine testing to support research is underway Commercially available GF-5 technologies 5W-20 using Group II base oils used as the baseline for LSPI tests  Afton understands key drivers of LSPI performance We are using optimal formulation strategies to develop Technology Driven Solutions Afton actively involved in the Preignition Prevention Program (P3) - a joint program with Southwest Research Institute, OEMs and other oil industry partners  Characterizing the LSPI phenomenon  Developing test conditions and platforms Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  36. 36. Summary of the Problem OEMs  Employ sub-optimal engine calibration to reduce LSPI risk • Fuel enrichment, exhaust gas recirculation  Sacrifice fuel economy  Stronger engine components – higher cost and weight (degrading CO2) Fuels  Fuel characteristics appear to influence LSPI  Current fuel specifications are not sufficient to capture LSPI performance Lubricants  Industry developing tests to measure tendency for LSPI  Optimal formulation strategies will be used to reduce risk of LSPI Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  37. 37. Conclusions Downsized engines will only become more prevalent in mature and emerging markets Fuels and lubricants work together with the engine as a system Their combined performance is crucial to enable the engine to realize its full potential We must balance this new demand against the existing requirements through the use of relevant industry tests Confidential and Proprietary - not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation. 2014 © Afton Chemical Corporation, All Rights Reserved
  38. 38. Acknowledgements Many thanks to our technical partners who contributed to this presentation The Southwest Research Institute

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