1. Competition To The Diesel Engine? David E. Foster Engine Research Center University of Wisconsin - Madison SAE Congress 2002, March 7, 2002

2. Criteria For An Acceptable Powerplant High power density – Power/Volume of the powerplant (kW/dm 3 ) – Displacement specific power (kW/L) – Mass per power (kg/kW) Good fuel economy Good vehicle range Must meet emission standards Robust Affordable

3. Two Approaches to Considering Competition to the Diesel Engine Advances in other powerplants enable them to more effectively meet the criteria for acceptability. Changes in the criteria for acceptability preclude the use of diesel engines. – For example: more stringent emission regulations might become unattainable when using a diesel engine.

4. Examining the Changing Criteria Avenue If the diesel engine is unable to meet future emission regulations, what might be alternative candidate powerplants? – Gasoline Engines – Gas Turbines – Fuel Cells – Electric motors – battery storage

5. Immediately Eliminate Two of the Candidates Gas turbines – Fuel economy for highly transient operation is too poor Electric motors with battery storage – On board energy storage capacity (range) and mass of the batteries severely limit their practicality for this application

6. Meeting Emissions Regulations Regulations (Trucks - 2007): – NOx (0.2 g/bhp-hr - 2007) – Particulate (0.01 g/bhp-hr) – NMHC (0.14 g/bhp-hr) Diesel Engines – Requires advanced combustion control, EGR, lean NOx and particulate exhaust gas aftertreatment systems Gasoline Engines – The ability to easily run stoichiometric, or rich, allows for use of efficient and mature exhaust gas aftertreatment systems Fuel Cells – Once you have the hydrogen – very low emissions

7. Assessment of Potential for Meeting Emission Regulations Diesel engines: – Very challenging – a high level of reduction of emissions in the exhaust gas is needed (lean NOx reduction is very challenging, particulate traps must be robust and withstand many cycles of regeneration Gasoline engines: – Emission reduction technologies are much more mature – should be able to meet standards Fuel cells: – It is anticipated that meeting emission standards would not be a problem

8. Comparing Fuel Consumption Because the fuels for the vehicles may be different, we must compare performance on a “Wells to Wheels” basis. – Not a huge difference in fuel processing “energy cost” when comparing gasoline and diesel. The most likely near term source of hydrogen is a hydrocarbon in combination with a fuel processor. – Petroleum, natural gas, etc Under a scenario of using a fuel processor, the “Wells to Wheels” efficiency of the fuel cell vehicle is probably on the same order, within engineering uncertainty, as that of advanced IC engine powertrains.

9. Relative Comparisons of Remaining Candidates for Other Criteria Powerplant Power/unit volume (kW/dm 3 ) Mass density (kg/kW) Displacement specific power (kW/L) BSFC (g/KW-hr) Turbocharged Diesel 18 - 263.5 – 7.0~ 45 @ 3000 rpm ~ 200 Gasoline (truck) 25 – 30 (max ~ 50) 2.5 – 6.5~ 18 @ 3000 rpm ~ 300 Fuel Cell0.14~ 7NA (?) Depends on load factor

10. Summary If the diesel engine is precluded from consideration as a powerplant, the most likely competitor will be a spark ignition engine. The primary challenge facing the spark ignition engine, for this market sector, would be fuel economy. The fuel cell faces challenges of power density, cost, range (if hydrogen is to be stored on board) and, in my opinion, fuel economy (in truck applications) – because of the heavy load duty cycle.