UNITI Mineral Oil Technology Congress LSPI lubricant formulation effect on fuel pre-ignition in engines Presented by: Dr Cecile Pera, Senior Engineer Performance you can rely on. Introduction 2017 Infineum International Limited. All rights reserved 1
Introduction What do we know about LSPI? LSPI has been studied by researchers for more than a decade It happens at low-speed and high-load Very sporadic and random occurrences Low speed pre-ignition Turbocharged engine High speed pre-ignition Torque (Nm) Natural aspirated engine Knocking Auto ignition Engine speed (rpm) October 2014 edition of SRI news 2012-01-1276 Introduction What do we know about LSPI? Problem exacerbated with high power-density engines (downsizing) Contrary to classical knock, it cannot be eliminated by spark-timing delay Contrary to classical knock, it can instantaneously damage the engine Lubricant and its additive package are involved Fuel blending and its properties also play a crucial role Pcyl Pre-ignition Super-knock Spark-timing Crank Knock Normal combustion 2017 Infineum International Limited. All rights reserved 2
Introduction Difference between LSPI, pre-ignition and super-knock? LSPI synopsis: Pre-ignition stage (prior to spark timing) Slow heat release stage due to flame propagation which is similar to normal combustion Super-knock: fast heat release due to large amount of unburnt mixture auto-igniting in one go Super-knock Although sometimes interchangeable, pre-ignition and super-knock represent 2 different phenomena Pcyl Pre-ignition Spark-timing Knock Normal combustion Pre-ignition: combustion of fuel/air mixture triggered by hot-spot prior to the spark timing Super-knock: severe engine knock (fuel auto-ignition) resulting of in-cylinder conditions (pressure, temperature) Crank Contents Introduction Influencing parameters LSPI mechanism focus on combustion LSPI combustion process Ignition Quality Tester (IQT) Conclusion 2017 Infineum International Limited. All rights reserved 3
Influencing parameters Influencing parameters on LSPI Overview Many factors can affect LSPI Engine hardware design (injection system, piston rings, etc.) Engine operating conditions (temperature, pressure, mixture composition, etc.) Gasoline fuel properties Deposits Lubricant 2017 Infineum International Limited. All rights reserved 4
Influencing parameters on LSPI Additives 120 100 SwRI HSHL Average GM Engine ILSAC GF-5 products 14 12 LSPI events 80 60 10 8 6 40 4 20 2 0 0 % Calcium Influencing parameters on LSPI Additives 120 100 SwRI engine GM engine 14 12 LSPI events 80 60 40 10 8 6 4 20 2 0 0 % Magnesium 2017 Infineum International Limited. All rights reserved 5
Influencing parameters on LSPI Additives 200 SwRI engine LSPI Events 180 160 140 120 100 80 60 40 20 0 % ZDDP Influencing parameters on LSPI Base stocks LSPI frequency Gp I Gp II Gp III PAO PAO (High Visc) Data from [SAE 2012-01-1615] GM engine Ford engine LSPI event Ignition frequency Gp II Gp III Gp III+ Gp IV Gp V Gp I Gp II Gp III PAO Data from [SAE 2014-01-1213] PAO (High Visc) 2017 Infineum International Limited. All rights reserved 6
LSPI mechanism focus on combustion LSPI mechanism: Proposed synopsis Step 1: pre-ignition Hot-spot ignition triggered by oil / additive combustion properties Injector Spray Oil film Fuel liner wetting Fuel + Oil 2017 Infineum International Limited. All rights reserved 7
LSPI mechanism: Proposed synopsis Step 1: pre-ignition Hot-spot ignition triggered by oil / additive combustion properties Injector Step 2: Following combustion process (flame propagation) Spray Oil film Fuel liner wetting Fuel + Oil LSPI mechanism: Proposed synopsis Step 1: pre-ignition Hot-spot ignition triggered by oil / additive combustion properties Injector Step 2: Following combustion process (flame propagation) Spray Step 3: Super-knock (fuel auto-ignition) Oil film Fuel Liner wetting Fuel + Oil Hardware (small vs large bore, etc.) Operating conditions (spark timings, etc.) Fuel/oil mixture and mixing Lube formulation Fuel properties 2017 Infineum International Limited. All rights reserved 8
LSPI combustion process Combustion process Why is pre-ignition not always followed by super-knock? LSPI synopsis: Early auto-ignition Flame propagation development 2 nd auto-ignition(s) or spark event is (are) followed by: a) Combustion extinction (no flame development) Pcyl Auto-ignition Unburnt Gas Flame propagation Pre-ignition Spark timing Pre-ignition + flame propagation V Normal combustion (envelope) 2017 Infineum International Limited. All rights reserved 9
Combustion process Why is pre-ignition not always followed by super-knock? LSPI synopsis: Early auto-ignition Flame propagation development 2 nd auto-ignition(s) or spark event is (are) followed by: a) Combustion extinction (no flame development) b) Flame propagation Pcyl Flame fronts Unburnt Gas Flame propagation Pre-ignition Spark timing Pre-ignition + flame propagation V Normal combustion (envelope) Combustion process Why is pre-ignition not always followed by super-knock? LSPI synopsis: Early auto-ignition Flame propagation development 2 nd auto-ignition(s) or spark event is (are) followed by: a) Combustion extinction (no flame development) b) Flame propagation } -auto-ignition heat release is too weak -initiated initial flame kernel is too small -fuel properties Pcyl Flame fronts Unburnt Gas Flame propagation Pre-ignition Spark timing Pre-ignition + flame propagation V Normal combustion (envelope) 2017 Infineum International Limited. All rights reserved 10
Combustion process Why is pre-ignition not always followed by super-knock? LSPI synopsis: Early auto-ignition Flame propagation development 2 nd auto-ignition(s) or spark event is (are) followed by: a) Combustion extinction (no flame development) b) Flame propagation c) Detonation (succession of auto-ignitions) Flame fronts Succession of auto-ignition Pcyl Pre-ignition Spark timing Super-knock Pre-ignition + flame propagation V Normal combustion (envelope) Combustion process Why is pre-ignition not always followed by super-knock? LSPI synopsis: Early auto-ignition Flame propagation development 2 nd auto-ignition(s) or spark event is (are) followed by: a) Combustion extinction (no flame development) b) Flame propagation c) Detonation (succession of auto-ignitions) - acoustic/combustion coupling - hardware design Flame fronts Succession of auto-ignition Pcyl Pre-ignition Spark timing Super-knock Pre-ignition + flame propagation V Normal combustion (envelope) 2017 Infineum International Limited. All rights reserved 11
Combustion process Combustion theory: deflagration vs detonation Two conditions are needed to initiate a coupling between pressure waves and the 2 nd AI front An auto-ignition propagation velocity close to the one of pressure waves (called here ξ) Sound speed ξ= reaction front velocity Combustion process Combustion theory: deflagration vs detonation Two conditions are needed to initiate a coupling between pressure waves and the 2 nd AI front An auto-ignition propagation velocity close to the one of pressure waves (called here ξ) A smooth gradient in the fresh gases surrounding the initial auto-ignition spot (called here ε) Sound speed Subsonic deflagration = classical flame propagation ξ= Developing and developed detonation reaction front velocity Time for maximal heat release ε= Time for pressure wave togo out from the end gas region Supersonic reaction wave propagation 2017 Infineum International Limited. All rights reserved 12
IQT Ignition Quality Tester Ignition Quality Tester Objectives In auto-ignition mechanism, there are two driving mechanisms: Creation of radicals through branching reactions which is an important mechanism for low temperature chemistry Run-away due to large heat release and temperature increase which is more important for high temperature kinetics IQT has the potential to focus on both mechanisms 2017 Infineum International Limited. All rights reserved 13
Ignition Quality Tester Principle of measurements Either pure oil or mixture of oil and fuel were tested Injection nozzle body τ ig Bomb pressure Injector displacement Ignition Quality Tester Gasoline surrogate design EN228 Surrogate RON 95.0 95.0 MON 85.0 85.0 H/C ratio 1.801 1.801 O/C ratio 0.011 0.011 Density (g/mol) 94.3 94.3 Real EN228 Gasoline Surrogate Olefins Oxgenated Linear paraffins Cyclohexene Ethanol n-heptane Aromatics Cyclic paraffins Branched paraffins Toluene Cyclohexane Isooctane Gasoline surrogate has been designed to target auto-ignition properties following methodology defined by Peraand Knop [1,2,3] [1] Peraand Knop, Fuel 2012 [2] Knop et al, Combust Flame 2013 [3] Knop et al Fuel 2014 2017 Infineum International Limited. All rights reserved 14
Ignition Quality Tester Results 40 100 90 DCN 30 20 IQT DCN RON Correlation 80 70 RON Pure Fuel DCN RON (Estimated) Fuel + oil 60 10 50 Mass Oil A in Sur95f Ignition Quality Tester Results Various Ca and Mg concentrations showed no statistically measurable difference in the IQT Addition of peroxide increased oil/fuel reactivity but showed again no sensitivity to the IQT to Ca / Mg content This result seems to indicate that Ca does not play a role either in the initiation or the branching reactions of the oil auto-ignition in the gaseous phase Various Ca and /or Mg concentration DCN Gasoline Mass oil in fuel 2017 Infineum International Limited. All rights reserved 15
Ignition Quality Tester Results Largest effect on IQT ignition appears to be the general chemical identity of the base oil Increased hydrocracking as group number increases through Group I Group IV 45 40 35 + 25%mass Oil in Sur95f 30 DCN 25 20 Sur95f Average 15 10 Group I Group II Group III Group IV Group V Conclusion 2017 Infineum International Limited. All rights reserved 16
Conclusion Base oil and additives play a role on LSPI mechanisms subject totest conditions (hardware, operating conditions, others) LSPI mechanism involves intricate sub-mechanisms Combustion is one of them Conclusion No discernible impact observed for Ca and Mg additives in the IQT No catalytic effect of Ca on auto-ignition in the homogeneous gaseous phase Large impact by base oil chemistry (Groups I-V) on auto-ignition in the IQT Reactivity ranking is: GpI < GpII < GpIII < GpIV (GpIV is the one that auto-ignite the more easily) Some GpV base oils are very resistance to auto-ignition Step 1: pre-ignition Injector Step 2: Flame propagation Spray Step 3: Super-knock Oil film Fuel Liner wetting Fuel + Oil 2017 Infineum International Limited. All rights reserved 17
Talk to us at exhibition stand 10 Dr. Cecile Pera, Senior Engineer Cecile.Pera@Infineum.com Permissions Permission is given for storage of one copy in electronic means for reference purposes. Further reproduction of any material is prohibited without prior written consent of Infineum International Limited. The information contained in this document is based upon data believed to be reliable at the time of going to press and relates only to the matters specifically mentioned in this document. Although Infineum has used reasonable skill and care in the preparation of this information, in the absence of any overriding obligations arising under a specific contract, no representation, warranty (express or implied), or guarantee is made as to the suitability, accuracy, reliability or completeness of the information; nothing in this document shall reduce the user s responsibility to satisfy itself as to the suitability, accuracy, reliability, and completeness of such information for its particular use; there is no warranty against intellectual property infringement; and Infineum shall not be liable for any loss, damage or injury that may occur from the use of this informationother than death or personal injury caused by its negligence. No statement shall be construed as an endorsement of any product or process. For greater certainty, before use of information contained in this document, particularly if the product is used for a purpose or under conditions which are abnormal or not reasonably foreseeable, this information must be reviewed with the supplier of such information. Please also refer to our Privacy Policy. INFINEUM, 润英联 and the interlocking ripple device are Trade Marks of Infineum International Limited. 2017 Infineum International Limited All rights reserved. 2017 Infineum International Limited. All rights reserved 18