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New Diesel Technology

Thermoelectrics, Liquid Nitrogen Injection, and Chrysler’s MultiFuel 2.4L Four-Cylinder

Text By Jason Thompson

Let’s say it’s 1996 and you’re trying to decide between a GM 6.5L, Ford 7.3L, or a Cummins 5.9L-powered truck. In your searches of the public library’s card catalog, you come across a technical article that says crystals will one day be used to electronically control diesel fuel injection. It goes on to say this new injector will be so fast it’ll be able to inject five times per combustion event. You think to yourself, “Could this be?” Just think: Four years later this very concept was in mass production in Europe, and 12 years later it was available in the United States. Ideas like this, along with pressure-sensing glow plugs and variable-geometry turbochargers, are all things we enjoy today—though they were just far-out ideas a few years earlier.

Industry Rumblings
The basic design of the diesel engine has not changed drastically since its conception. Historically, improvements have been gradual more than revolutionary. Although, the perfect storm generated by increased fuel costs and emissions regulations is poised to change our engine compartments forever. Right now, whirlwinds are arising in companies as these new innovations are forged.

Thermoelectrics
A thermoelectric generator (TEG) turns temperature differences into electricity and vice versa. They are made from solid-state integrated circuits that form thermocouples, which are sandwiched between thin ceramic wafers. The TEG is similar to the semiconductor because its price is projected to go down with production volume, performance is increasing, and it has the potential to change the world we live in. For every gallon of diesel fuel you burn in your engine, only about 30 to 40 percent of it gets transferred to work. More than half the potential energy gets wasted out the exhaust pipe, EGR cooler, and radiator in the form of heat. This was acceptable when emissions regulations weren’t as strict and when fuel was $1 a gallon—but not when it’s at $5. In order to capture this supply of wasted energy, engineers are turning the muffler into a TEG generator. A device like this is capable of reducing fuel consumption by 5 to 6 percent because the alternator can be reduced by 1⁄3. Ford and GM are both working on concepts of their own with DOE support. Another use of thermoelectrics is engine pre-heating and battery temperature management for increased longevity.

BMW’s thermoelectric generator (TEG) concept doubles as an EGR cooler with an electrical output of approximately 250 watts. It also enables precise heat management inside the engine.

GM 1.9L four-cylinder diesel engine with electrically assisted diesel particulate filter (EADPF)
Diesel enthusiasts don't like the fuel economy penalty that results when their DPF goes into regeneration mode. This happens because extra fuel is needed to heat up the exhaust after-treatment because normal engine operation is not generating enough heat to carry out the reaction. Recently, the Department of Energy and GM came together to produce an electrically assisted diesel particulate filter (EADPF). This device allows the regeneration event to be much more controlled and efficient, which translates into fuel savings and clean emissions.

Chrysler’s MultiAir and MultiFuel 2.4L Four-Cylinder
Chrysler, in a partnership with the DOE, is developing a new 2.4L four-cylinder engine. When the program is completed in 2013, this Multi engine is supposed to demonstrate a 25 percent fuel economy improvement over the ’09 minivan powered by a gasoline 4.0L V-6 . It’s also projected to meet squeaky-clean Tier 2 Bin 2 emissions regulations.

Highlights include:

Variable valve technology that allows for internal EGR

Three valves per cylinder

Delphi supplied the injectors. There is direct injection of diesel fuel above the piston and gasoline directly injected on the side of the combustion chamber.

The engine block is aluminum with a spray-on bore liner.

The Multi has crankshaft-mounted absorbers for limiting 2nd order torsional vibrations that affect four cylinder engines. This enables the torque converter to lock up at lower engine speeds—increasing economy.

Two turbochargers selected

High-compression ratio for increased efficiency

Cuts fuel supply during vehicle deceleration

Engine shutoff at idle (stop and start technology)

Ricardo’s CoolR Concept
The CoolR concept (partly funded by the United Kingdom’s Technology Strategy Board) uses split-cycle cryogenic injection combustion. This engine uses thermodynamic principles to its advantage in order to obtain 60 percent thermal efficiency. Split-cycle means one cylinder is for compressing the gas and one cylinder is for expanding (combusting) it. Recuperated combustion engines transfer exhaust heat to the working gas at the end of compression (at constant volume).

SOURCES
Ricardo
www.ricardo.com
Department of Energy
www1.eere.energy.gov
By Jason Thompson
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