A PRAGMATIC APPROACH TO REDUCING THE CO2 FOOTPRINT OF THE INTERNAL COMBUSTION ENGINE

Transcription

1 A PRAGMATIC APPROACH TO REDUCING THE CO2 FOOTPRINT OF THE INTERNAL COMBUSTION ENGINE SYNERGISTICALLY INTEGRATING ADVANCED SPARK IGNITION ENGINES AND FUTURE FUELS Paul Najt General Motors Global R&D

2 THE CO2 CHALLENGE

3 MY2014 Vehicles Meeting CO2 Reg THE CO2 CHALLENGE Meeting future CO2 regulations while delivering vehicles that customers want and can afford. will require the synergistic integration of fuels and engine technologies <5% MY2014 vehicles in the US meet MY2025 CO2 and all make use of are advanced powertrains Source: EPA US Light-Duty Automotive Technology, Carbon Dioxide Emissions and Fuel Economy Trends: 1975 Through 2014

4 THE ENGINE CHALLENGE To maximize engine efficiency we must focus on minimizing loss mechanisms and maximizing work recovery Aggressively downsize to reduce parasitic losses o Key enablers are advanced boost systems and increased knock tolerance more knock resistant fuels Migrate to compression ratios between 13 & 14 to maximize work extraction without incurring major parasitic losses o Key enablers are variable valve actuation and increased knock tolerance more knock resistant fuels Migrate to high levels of charge dilution to minimize heat losses and maximize work extraction o Key enablers are increased EGR tolerance and Lean, Low Temperature Combustion more reactive fuels Maintaining modest peak pressure levels to avoid incurring major parasitic losses o Key enablers are homogeneous stoichiometric operation at WOT with rated speed above 6000rpm

5 THE ENGINE CHALLENGE BSFC (g/kw-hr) Downsizing is critical to enhancing vehicle level fuel economy and thus fuels that maximize resistance to knock are critical -- enabling increased compression ratios and more advanced combustion phasings at high loads to maximizing the benefits L Prod. Turbo 2.0L Prod. Nat. Asp Downsizing Engines scaled to 120kW (equivalent vehicle level performance) Torque (Nm)

6 THE ENGINE CHALLENGE BSFC (g/kw-hr) High levels of charge dilution and lean, low temperature combustion at low loads are critical to enhancing vehicle level fuel economy and thus fuels with good low load reactivity are critical but, not at the expense of full load performance Downsizing 1.4L Prod. Turbo 2.0L Prod. Nat. Asp. 1.35L G-LTC Engine Lean, Low Temp Comb Engines scaled to 120kW (equivalent vehicle level performance) Torque (Nm)

7 THE ENGINE CHALLENGE BSFC (g/kw-hr) At equal performance, engines that operate lean, LTC at full load degrade specific output and vehicle level fuel economy --- to maximize fuel economy it is critical to synergistically blend aggressive downsizing (stoichiometric operation at full power) with lean, low temperature combustion at part load Upsizing 1.4L Prod. Turbo 2.0L Prod. Nat. Asp. 2.1L Delphi GDCI Engine GDCI 1.35L G-LTC Engine GDCI Data SAE Engines scaled to 120kW (equivalent vehicle level performance) Torque (Nm)

8 THE FUELS CHALLENGE To maximize SI Engine potential the fuel should have high knock resistance at high loads and good reactivity at low loads, the fuel should have the following properties High knock resistance with high sensitivity o High RON and High Sensitivity Low variability across the marketplace o RON, Sensitivity, T90, Near-zero sulfur, < 10 ppm Good low temperature catalyst reactivity Low propensity to soot We don t need a new fuels, we need an improved gasoline with high RON, high Sensitivity and low variability

9 More Reactive Ignition Delay THE FUELS CHALLENGE SENSITIVITY High sensitivity fuels are relatively stable at low temperatures, but react rapidly at high temperatures. Typical High Sensitivity Fuel (e.g. Ethanol) High RON Increasing Sensitivity Decreasing Reactivity Knock Resistance Typical Low Sensitivity Fuel (e.g. 100 PRF) Low MON Sensitivity = RON-MON Increasing Sensitivity Increasing Reactivity Compression Ignition 1/Temperature Higher Temperature

10 THE FUELS CHALLENGE OCTANE INDEX Octane Index (OI = RON K*Sensitivity) is a good measure of fuel performance when K is adjusted to the engine/combustion mode K characterizes the temperature, pressure trajectory associated with a specific engine/combustion mode Gasoline Spark Ignition (conventional) Gasoline Low Temp Combustion (e.g. HCCI) Knock Resistance high pressure, low temperature condition K is negative Sensitivity increases Octane Index and degrades reactivity Compression Ignition low pressure, high temperature condition K is positive Sensitivity decreases Octane Index and increases reactivity

11 THE FUELS CHALLENGE KNOCK RESISTANCE For high load SI Engine Knock Resistance a K value of -1 reflects modern, high boost SI engine/combustion performance Reference: Sarah Remmert et. al., Fuel Effects in a downsized, Highly Boosted direct Injection Spark Ignition Engine, 23rd Aachen Colloquium Automobile and Engine Technology 2014.

12 NVO = 130 THE FUELS CHALLENGE COMPRESSION IGNITION For Lean, Low Temperature Compression Ignition a K value of 2 accurately predicts engine/combustion performance Gasolines y = x R 2 = B&Ternary Octane Index (K = 2)

13 THE FUELS CHALLENGE The ideal gasoline is a high RON, high Sensitivity alternative for both near-term Boosted SI Engines and long-term LTC/HCCI Engines Need to minimize the impact of low sensitivity paraffinic fuels

14 THE FUELS CHALLENGE The ideal low-carbon based gasoline for both near-term Boosted SI Engines and long-term LTC/HCCI Engines emphasizes alcohols, olefins and furans Need to minimize the impact of low sensitivity Esters & Ketones

15 THE PRAGMATIC APPROACH The ideal engine synergistically integrates aggressive downsize boosting with lean, low temperature combustion The ideal engine builds on the downsize boosting mega-trend, operating with homogeneous, stoichiometric combustion at high loads to maximize specific output and minimize parasitic losses The ideal engine introduces lean, low temperature combustion at low loads to maximize vehicle level fuel economy by reducing heat losses and maximizing work extraction The ideal engine needs a fuel that has excellent knock resistance at high loads and good autoignition reactivity at low loads The ideal fuel has High RON, High Sensitivity and low variability to support the synergistic integration of downsizing and lean, low temperature combustion We do not need radical changes, we need to continue building on existing engine trends and developing a better gasoline!