Smart materials offer new solutions for diesel engines
Here's a question to stump the shop technicians and baffle the Rotary Breakfast Club: What is Terfenol-D ? Is it:
A. The latest treatment for a cold, available in liquid or tablet form.
B. A metal alloy, composed of the elements terbium, dysprosium, and iron.
C. A compound found in commercial fertilizers, industrial greases, and some pet foods.
The correct answer is "B," and while it can't cure a cold, Terfenol-D deserves attention because of what it can do for diesel engines.
The specially formulated iron alloy is a so-called "smart material" that has the ability to react mechanically to electrical or magnetic stimuli. According to Rodi Power Systems Inc., its properties make it a perfect material for controlling liquid fuel injectors with more speed and precision than was previously possible.
"Terfenol-D is a magnetostrictive material, which means exposure to a magnetic field causes it to grow linearly at the molecular level," explains Byron Spain, Rodi founder and CEO. "It will react at the rate of 6,000 cycles per second - about 200 times faster than today's typical fuel injector valve, which opens and closes at the rate of about 30 times per second.
"Of course, technically speaking, our solid-state injector really has no moving parts. The material itself changes to permit and restrict injection of fuel into the cylinder," he notes. "A small solenoid coil creating about 10 amps of current is enough to trigger this reaction in the material, which 'opens and closes' the injector.
"From a performance standpoint, the use of Terfenol-D for fuel injectors will add a dimension of control previously unattainable, allowing extremely fast open and close times, less than 0.5 milliseconds, plus very accurate shaping of the fuel flow into the cylinder. In tests, we have been able to control 1,000 cycles to within one drop of fuel," Spain adds. "Plus, we use very high injection pressures - 28,000 to 30,000 psi.
"Since there are no moving parts, the material does not wear out. This gives us a device about as rugged as a spark plug that should last the life of the engine," he continues. "The nozzle tips can still be damaged, but they're easy to remove and replace."
Rodi recently signed an agreement with EXTREMA Products Inc., the supplier of Terfenol-D, to develop fuel injection systems utilizing the alloy. The agreement gives Rodi exclusive rights worldwide in the development and sale of the injectors for use in internal combustion engines in the 120- to 500-hp. range, according to Spain. A patent is pending.
"We are in the second generation of testing now," notes Spain. "The injectors are reliable, accurate, and durable. The next step is to modify an engine with our injectors and run comparison tests against an identical standard production engine. Truck engines are an ideal application for this system," he adds, "because the Terfenol-D injectors have the ability to perform across a very wide engine operating range, adapting to any speed."
Rodi's own engine - the HT1-450, a unique lightweight diesel - will be the first to get the injectors, according to Spain, who plans to have 25 engines in trucks and on the road in beta testing by the summer and warranted units available by November. More than 2,000 fleets have already offered to be a part of the engine field testing, which will include Terfenol-D injectors and a new Rodi-designed Turbo Supercharger.
Visit www.rodi.com to follow Rodi's progress.A warning, however: The enthusiasm and energy at Rodi is highly contagious these days, and the only known cure seems to be Terfenol-D.