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The Evolution of the Internal Combustion Engine and Future Design Challenges: Performance, Efficiency, Emissions. Paul D. Ronney Dept. of Aerospace & Mechanical Eng. University of Southern California Los Angeles, CA 90089-1453 USA http://carambola.usc.edu. Outline.

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The Evolution of the Internal Combustion Engine and Future Design Challenges:Performance, Efficiency, Emissions

Paul D. Ronney

Dept. of Aerospace & Mechanical Eng.

University of Southern California

Los Angeles, CA 90089-1453 USA

http://carambola.usc.edu

outline
Outline
  • Why gasoline-fueled premixed-charge IC engines?
  • History and evolution
  • Things you need to understand about IC engines before ...
  • Ideas for improvements
  • Conclusions

University of Southern California - Department of Aerospace and Mechanical Engineering

why premixed charge ic engines
Why premixed-charge IC engines?
  • Alternatives
    • External combustion - "steam engine," "Stirling cycle"
      • Heat transfer is too slow (≈ 100x slower than combustion)
      • 10 B-747 engines ≈ large coal-fueled electric power plant
    • Electric vehicles (EVs)
      • Batteries are heavy ≈ 1000 lbs/gal of gasoline equivalent
      • Fuel cells better, but still nowhere near gasoline
      • "Zero emissions" myth - EVs export pollution
      • Environmental cost of battery materials
      • Possible advantage: makes smaller, lighter, more streamlined cars acceptable to consumers
      • Prediction: eventual conversion of electric vehicles to gasoline power (>100 miles per gallon)

University of Southern California - Department of Aerospace and Mechanical Engineering

zero emission electric vehicles
“Zero emission” electric vehicles

University of Southern California - Department of Aerospace and Mechanical Engineering

why premixed charge ic engines5
Why premixed-charge IC engines?
  • Alternatives (continued…)
    • Solar
      • Need ≈ 30 ft x 30 ft collector for 15 hp (Arizona, high noon, mid-summer)
    • Nuclear
      • Who are we kidding ???
  • Moral - hard to beat gasoline-fueled IC engine for
    • Power/weight & power/volume of engine
    • Energy/weight & energy/volume of liquid hydrocarbon fuel
    • Distribution & handling convenience of liquids

University of Southern California - Department of Aerospace and Mechanical Engineering

history and evolution
History and evolution
  • 1859 - Oil discovered in Pennsylvania
  • 1876 - Premixed-charge 4-stroke engine - Otto
    • 1st practical IC engine
    • Power: 2 hp; Weight: 1250 pounds
    • Comp. ratio = 4 (knock limited), 14% efficiency (theory 38%)
    • Today CR = 8 (still knock limited), 30% efficiency (theory 52%)
  • 1897 - Nonpremixed-charge engine - Diesel - higher efficiency due to
    • Higher compression ratio (no knock problem)
    • No throttling loss - use fuel/air ratio to control power

University of Southern California - Department of Aerospace and Mechanical Engineering

premixed vs non premixed charge engines
Premixed vs. non-premixed charge engines

University of Southern California - Department of Aerospace and Mechanical Engineering

history and evolution8
History and evolution
  • 1923 - Tetraethyl lead - anti-knock additive
    • Enable higher CR in Otto-type engines
  • 1952 - A. J. Haagen-Smit
    • NO + UHC + O2 + sunlight  NO2 + O3

(from exhaust) (brown) (irritating)

  • 1960s - Emissions regulations
    • Detroit won’t believe it
    • Initial stop-gap measures - lean mixture, EGR, retard spark
    • Poor performance & fuel economy
  • 1973 & 1979 - The energy crises
    • Detroit takes a bath

University of Southern California - Department of Aerospace and Mechanical Engineering

history and evolution9
History and evolution
  • 1975 - Catalytic converters, unleaded fuel
    • Detroit forced to buy technology
    • More “aromatics” (e.g., benzene) in gasoline - high octane but carcinogenic, soot-producing
  • 1980s - Microcomputer control of engines
    • Tailor operation for best emissions, efficiency, ...
  • 1990s - Reformulated gasoline
    • Reduced need for aromatics, cleaner(?)
    • ... but higher cost, lower miles per gallon
    • Now we find MTBE pollutes groundwater!!!

University of Southern California - Department of Aerospace and Mechanical Engineering

things you need to understand before
Things you need to understand before ...

…you invent the zero-emission, 100 mpg 1000 hp engine, revolutionize the automotive industry and shop for your retirement home on the French Riviera

  • Room for improvement - factor of 2 in efficiency
    • Ideal Otto cycle engine with CR = 8: 52%
    • Real engine: 25 - 30%
    • Differences because of
      • Throttling losses
      • Heat losses
      • Friction losses

University of Southern California - Department of Aerospace and Mechanical Engineering

things you need to understand before11
Things you need to understand before ...
  • Room for improvement - infinite in pollutants
    • Pollutants are a non-equilibrium effect
      • Burn: Fuel + O2 + N2® H2O + CO2 + N2 + CO + UHC + NO

OK OK OK Bad Bad Bad

      • Expand: CO + UHC + NO “frozen” at high levels
      • With slow expansion, no heat loss:

CO + UHC + NO ® H2O + CO2 + N2

...but how to slow the expansion and eliminate heat loss?

    • Worst problems: cold start, transients, old or out-of-tune vehicles - 90% of pollution generated by 10% of vehicles

University of Southern California - Department of Aerospace and Mechanical Engineering

things you need to understand before12
Things you need to understand before ...
  • Room for improvement - very little in power
    • IC engines are air processors
      • Fuel takes up little space
      • Air flow = power
      • Limitation on air flow due to
        • “Choked” flow past intake valves
        • Friction loss, mechanical strength - limits RPM
        • Slow burn
  • Majority of power is used to overcome air resistance - smaller, more aerodynamic vehicles beneficial

University of Southern California - Department of Aerospace and Mechanical Engineering

ideas for improvement alternative fuels
Ideas for improvement - alternative fuels
  • Natural gas

+ Somewhat cleaner than gasoline, non-toxic

+ High octane without refining or additives (≈ 110)

+ No cold start problem

+ Abundant, domestic supply

+ Cheap (≈ 1/5 gasoline)

+ Half the CO2 emission of EVs charged with coal-generated electricity

+ Dual-fuel (gasoline + natural gas) easily accommodated

- Lower energy storage density (≈ 1/4 gasoline)

- Lower power (≈ 7% less)

Attractive for fleet vehicles with limited territory

University of Southern California - Department of Aerospace and Mechanical Engineering

ideas for improvement alternative fuels14
Ideas for improvement - alternative fuels
  • Alcohols

+ Slightly cleaner than gasoline

+ High octane (≈ 95)

- Not cost-effective without price subsidy

- Lower storage density (methanol ≈ 1/2 gasoline)

- Toxic combustion products (aldehydes)

Attractive to powerful senators from farm states

  • Hydrogen

+ Ultimate clean fuel

+ Excellent combustion properties

+ Ideal for fuel cells

- Very low storage density (1/10 gasoline)

- Need to manufacture - usually from electricity + H2O

Attractive when we have unlimited cheap clean source of electricity and breakthrough in hydrogen storage technology

University of Southern California - Department of Aerospace and Mechanical Engineering

ideas for improvements reduce heat loss
Ideas for improvements - reduce heat loss
  • Reduction of heat losses
    • Heat losses caused by high engine turbulence levels
    • Need high turbulence to
      • Wrinkle flame (premixed charge, gasoline)
      • Disperse fuel droplets (nonpremixed charge, Diesel)
    • "Inverse-engineer" engine for low-turbulence
      • Gasoline - electrically-induced flame wrinkling?
      • Diesel - electrostatic dispersion of fuel in chamber?

University of Southern California - Department of Aerospace and Mechanical Engineering

electrostatic sprays
Electrostatic sprays

University of Southern California - Department of Aerospace and Mechanical Engineering

ideas reduce throttling loss
Ideas - reduce throttling loss
  • Premixed-charge IC engines frequently operated at lower than maximum torque output (throttled conditions)
  • Throttling adjusts torque output of engines by reducing intake density through decrease in pressure ( P = rRT)
  • Throttling losses substantial at part load

University of Southern California - Department of Aerospace and Mechanical Engineering

the tpce concept
The TPCE concept
  • Throttleless Premixed-charge Engine (TPCE)
  • U. S. Patent No. 5,184,592
  • Supported by SCAQMD School Clean Fuels Program
  • Preheat air using exhaust heat transfer to reduce r
  • Preheat provides leaner lean misfire limit - use air/fuel ratio AND intake temperature to control torque
  • Provides Diesel-like economy with gasoline-like power
  • Retrofit to existing engines possible by changing only intake, exhaust, & control systems

University of Southern California - Department of Aerospace and Mechanical Engineering

tpce implementation concept
TPCE implementation concept

University of Southern California - Department of Aerospace and Mechanical Engineering

results
Results
  • Substantially improved fuel economy (up to 16 %) compared to throttled engine at same power & RPM

University of Southern California - Department of Aerospace and Mechanical Engineering

results21
Results
  • NOx performance

< 0.8 grams per kW-hr (10 x lower than throttled engine )

< 0.2 grams per mile for 15 hp road load @ 55 mi/hr - half of California 2001 standard

  • CO and UHC comparable to throttled engine

University of Southern California - Department of Aerospace and Mechanical Engineering

ideas for improvements
Ideas for improvements
  • Programmable intake/exhaust valve timing
    • Electrical/hydraulic valve actuation
    • Choose open/close timing to optimize power, emissions, efficiency - can eliminate throttling loss

University of Southern California - Department of Aerospace and Mechanical Engineering

ideas for improvements23
Ideas for improvements
  • Homogeneous ignition engine - controlled knocking
    • Burn much leaner mixtures - higher efficiency, lower NOx
    • Need to abandon traditional “Hail, Mary” combustion control strategy

University of Southern California - Department of Aerospace and Mechanical Engineering

ideas improved lean limit operation
Ideas - improved lean-limit operation
  • Recent experiments & modelling suggest lean-limit rough operation is a chaotic process
  • Feedback via exhaust gas residual
  • Could optimize spark timing on a cycle-to-cycle basis
  • Need to infer state of gas & predict burn time for next cycle - need in-cylinder sensors

University of Southern California - Department of Aerospace and Mechanical Engineering

conclusions
Conclusions
  • IC engines are the worst form of vehicle propulsion, except for all the other forms
  • Despite over 100 years of evolution, IC engines are far from optimized
  • Any new idea must consider many factors, e.g.
    • Where significant gains can & cannot be made
    • Cost
    • Resistance of suppliers & consumers to change
  • Easiest near-term change: natural-gas vehicles for fleet & commuters
  • Longer-term solutions mostly require improved (cheaper)
    • Sensors(especially in-cylinder temperature, pressure)
    • Actuators (especially intake valves)

University of Southern California - Department of Aerospace and Mechanical Engineering

thanks to
Thanks to ...
  • USC Dept. of Aerospace & Mechanical Engineering
  • Gas Research Institute
  • South Coast Air Quality Management District
  • … and especially METRANS

University of Southern California - Department of Aerospace and Mechanical Engineering