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Challenge

Research has shown that CIDI(compression ignition, directinjection) engines fueled withdimethyl ether (DME) canachieve ULEV exhaust emis-sions levels while maintainingthe thermal efficiencyof a conventional diesel.However, the unique physicalproperties of DME presentchallenges to its utilization.DME is a gas at atmosphericpressure but liquifies under modest pressuriza-tion. DME also has very low viscosity, leadingto high internal leakage in supply pumps,solenoid valves, and fuel injectors. Suchlimitations require that significant modificationsbe made to conventional fuel injectionequipment to accommodate the use of DMEin a diesel engine.

TechnologyDescription

A high efficiency, variable displacement axialpiston fuel pump has been designed for usein DME fueled CIDI engines. The wobbleplate actuated pump design permits variabledisplacement through inlet throttling and highefficiency (low leakage) through positivesealing.

A uniquely designedfuel tank delivers liquidDME under pressure of

10 bar to the pump. Acam actuated intensifierincreases fuel pressuresupplied to the throttleinlet to 20 bar. As thepiston strokes down,fuel flows through thethrottle and into the

cylinder. If piston speed is low enough, inletflow is equal to the piston displacement. Ifpiston speed is high, inlet flow is lower thanthe piston displacement; the fuel vaporizesand then re-liquifies upon compression bythe piston. When all of the fuel is liquefied,pressure rises and fuel flows out.

Accomplishments

The pump has been integrated into a completecommon rail fuel system and packaged foruse on a Ford DIATA engine. Additional fuelsystem components have been designed. Theseinclude: fuel injector assembly, rail pressureand back pressure control valve mountings,fuel filter, supply and return lines, and fueltank assembly.

Benefits

s CIDI engines have the

highest thermal efficiency ofany demonstrated automo-tive power plant.

s DME fueled engines couldlimit harmful emissionswithout sacrifice to engineefficiency.

PrototypeFuelInjectionSystem

April 2001 http://www.ott.doe.gov/success.html

Allows dimethyl ether use ina 4-cylinder diesel engine

ContactsLucito CataquizManager, Alternative Fuels202-586-0729202-586-9811 faxlucito.cataquiz@ee.doe.gov

Wendy ClarkNational Renewable

Energy Laboratory303-275-4468303-275-4415 faxwendy_clark@nrel.gov

PrototypeFuelInjectionSystem

Fuel delivery system

Variable displacement fuel pump.

Saturated Propane

Liquid DME10 bar, 25 C

Return Cam

2:1 Intensifier

Liquid DME20 Bar, 30 C

Throttle

Saturated DME14 Bar, 60 C

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Future Activities

Emissions and performance demonstrations are underway using the developed fuel system installedon a Ford DIATA CIDI engine fueled with DME.

Partners in Success

s AVL Powertrain Technologies, Inc.

s Ford Motor Company

s National Renewable Energy Laboratory

http://www.ott.doe.gov/success.html