Cleaner, Higher Efficiency Vehicles Using Plasmatrons†

Daniel R. Cohn

Plasma Science and Fusion Center

Massachusetts Institute of Technology

Presentation to Fusion Power Associates Meeting

Washington, D.C., Nov. 21, 2003

†Research supported by Dept. of Energy Office of FreedomCAR and Vehicle Technologies and by ArvinMeritor

Team• MIT PLASMA SCIENCE AND FUSION CENTER

– L. Bromberg– D.R. Cohn– A. Rabinovich – K Hadidi – N. Alexeev – A. Samokhin– J. Palaia

• MIT SLOAN AUTOMOTIVE LABORATORY– J. Heywood– J. Goldwitz– N. Margarit – G. Ziga

• ARVINMERITOR– Major US automotive and heavy truck components manufacturer – Commercializing technology licensed from MIT– R. Smaling et. al.

Lower Emission, Higher Efficiency Gasoline Engine

Fuel Tank

Onboard Plasmatron

FuelConverter

Ultra lean Burn Gasoline engine

Gasoline

(e.g. 25%)Hydrogen-rich gas (H2+CO)

• Reduced pollutants (NOx)

• Increased efficiency

Gasoline

(e.g. 75%)

Uses of Onboard Hydrogen Generation

Gasoline Engine Cars And Other Light Duty VehiclesHydrogen combusted along with gasoline in engineLower emissions (from ultra lean operation)Higher efficiency (from ultra lean operation, higher

compression ratio, strong turbocharging)

Diesel Engine Trucks and BusesUse in exhaust aftertreatment systemFacilitates attractive exhaust aftertreatment system for

reduction of NOx (nitrogen oxides are a primary source of smog)

Plasmatron Reformer

Compact (e.g. 2 liter) device for onboard reforming of hydrocarbon fuels (gasoline, diesel, bio-oils, other fuels) into hydrogen-rich gas

Reforming promoted by special electrical discharge

Production of Hydrogen Rich Gas From Partial Oxidation Reforming

• Add sufficient oxygen from air to bind all carbon in fuel as CO;

• For iso-octane (representative of gasoline):

C8H18 + 4 (O2 + 3.8 N2) --> 8 CO + 9 H2 + 15.2 N2

• Reaction is mildly exothermic– ~ 15% of energy released in the reformation process

– Relatively slow reaction

– Difficult to provide effective reforming under transient conditions

• Provides continuous volumetric initiation of reforming reactions– Use of a special low current, high voltage distributed plasma

• Advantages– Rapid startup and transient response– Relaxation or elimination of reforming catalyst requirements

(conventional reformer catalyst vulnerability has been a major impediment)

– Inhibits soot production– Compact– Efficient– Applicable to a wide range of fuels including difficult to

process fuels (diesel, bio-oils)

Plasmatron Reformer

Low current gasoline plasmatron

Power W 250Plasma current A 0.1 - 0.4

H2 flow rate slpm 10-200

Volume liter 2

Weight kg 3

• Plasma created in the a gas flow

• Gas flow stretches the plasma

• Plasma extinguishes and re-establishes (1 kHz)

• Discharge over a large volume

END VIEW

Plasmatron Hydrogen Enhanced Turbocharged Gasoline Engines

•Moderate fraction (20% - 30%) of gasoline converted into hydrogen-rich gas

•Addition of hydrogen-rich gas improves both combustion stability resistance to knock (undesired detonation or “pinging”)

•Increased knock resistance allows high compression ratio and strong turbocharging

•Net efficiency increase of up to 30%

•Engine efficiency can be substantially increased by

–Ultra lean burn (high air/fuel ratio)–High compression ratio–Strong turbocharging (allows for engine downsizing)

SAE-2003-01-0630

Lean burn characteristics of a gasoline engine enriched with hydrogen rich gas from a plasmatron fuel reformer

E. Tully and J.B. Heywood

MIT Dept. of Mechanical Engineering and Sloan Automobile Laboratory

Gasoline engine testing at MIT

• Hydrogen enhanced combustion stability allows very lean burn (high air to fuel ratio) without misfire

• Naturally aspirated (no turbocharging) with conventional compression ratio

• Ultralean operation increases efficiency 15% and decreases NOx by a factor of 50

Leaner operation

Leaner operation

Lambda

Lambda

High Compression Ratio, High Boosted Operation through Improved Knock Resistance

• Recent experimental studies at MIT Sloan Automobile laboratory show that knock resistance is substantially improved by addition of hydrogen rich gas to gasoline– Octane rating number (ORN) has been increased by 20 ORN

when 25% of fuel energy is from hydrogen-rich gas (for reference, the octane rating number difference between regular and premium gasoline is 6)

• The combination of enhanced knock resistance and enhanced combustion stability are projected to increase gross engine efficiency by a factor of up to 1.4 and net efficiency by up to 1.3

Plasmatron Hydrogen Enhanced Turbocharged Gasoline EnginesRough Projections

Concept

Average fraction of fuel reformed

Net Efficiency increase

EmissionsReduction in gasoline use

Comments

Ultra lean operation with conventional powertrain

30% 1.3Extremely

low21%

Turbocharged with high compression ratio

Ultra lean operation with hydrid powertrain

30% 1.7Extremely low

40%Increased cost for powertrain

Status and Prospects Plasmatron hydrogen enhanced turbocharged

gasoline engines• Tests on engines in the laboratory • Ultimate goal is up to 30% increase in net efficiency

with further decreased emissions from already low emissions

• Could be economically attractive:– Additional cost projected to be around $1,000 including the

cost of the turbocharger – Pay back time from fuel savings significantly less than life

of vehicle

• Next step involves vehicle tests by ArvinMeritor team

Diesel Engine Emissions Aftertreatment Concept

PlasmatronReformer

AbsorberCatalyst

Exhaust from engine (Oxygen rich)

Clean exhaust

AbsorberCatalyst

Normal Operation Regeneration

Clean exhaust

NOx

Small sidestream of diesel fuel

Hydrogenrich gas

Advantages of regeneration with H2-rich gas:– Greater operating temperature range (down to about 130 C)– Greater regeneration effectiveness (fuel penalty decreased by a factor of 2)– Reduced sulfur effects on system

H2-Assisted NOx Trap: Test Set-up

NOx Trap A

Engine

Reformate

To Tailpipe

NOx Trap B

Switching Valve

Fuel ReformerFuel

Air

Power

Brake Valve

NOx Adsorption Comparison – Bus Road Load Same Fuel Penalty

0

10

20

30

40

50

60

70

80

90

100

100 150 200 250 300 350 400

Exhaust Temperature - deg C

Nox Adsorbed - %

Diesel Reformate

Upstream DOC Added

Diesel regeneration

Plasmatron hydrogen regeneration

Bus H2-Assisted NOx Trap Installation

Fuel Reformer Box

NOx Trap: 21L/leg

Access Door

Prospects Diesel Exhaust Treatment

• EPA requirements demand implementation of effective exhaust aftertreatment system in heavy trucks and buses in 2007-2010 time frame– Present heavy vehicles use no exhaust aftertreatment

• Plasmatron hydrogen enhanced NOx trap aftertreatment is one of the most promising technologies to meet this need

Summary

• Onboard plasmatron hydrogen generation could improve efficiency and reduce emissions of both gasoline and diesel engine vehicles

• The environmental and economic attractiveness of plasmatron enhanced turbocharged gasoline engine vehicles could facilitate widespread use. Widespread use could result in a significant impact on average fuel efficiency

• If average fuel efficiency of US fleet of cars and light duty

vehicles is increased by 20%, yearly fuel savings would be 25 billion gallons of gasoline (equivalent to 70% of oil presently imported from the Middle East)

Summary (continued)

• Use of onboard hydrogen generation for improving internal combustion engine vehicles could provide substantial impact much sooner than use of hydrogen fuel cells

• Could be first step towards longer term vision of hydrogen fuel cell vehicles. Next step could be use of a small amount of stored hydrogen.