Browse Publications Technical Papers 2007-01-4113
2007-10-29

Possible Very High Speed Rate Shaping Fuel Injector 2007-01-4113

Magnetostrictive and piezoceramic materials combine specific energy with speed, enabling fast and powerful but compact transducers. These materials, used in US Navy sonar for decades, elastically strain under the influence of a magnetic or electric field.
Piezoceramics become active when electrically poled. Poling being artificial, the ceramic loses its piezoelectric properties under overstress, overstrain, overvoltage, or overheating, conditions present in a diesel engine that limit injector performance.
In contrast, a magnetostrictive alloy of terbium, dysprosium, and iron will not permanently degrade under the same conditions, enabling an injector to be pushed to the highest possible speed. Quantum mechanics dictate that the non-bonding 4f electron cloud of the terbium atom be oblate, not spherical, an inherent property that connects magnetic and elastic influences.
Very high speed injector features include a thin solenoid coil of few turns, a highly compressed magnetostrictive alloy, and a minimized magnetic flux path that suppresses eddy currents. Compression controls size, cost, and electrical needs. Valve speed and displacement are both always proportional. Direct contact fuel cooling of the magnetostrictive alloy and solenoid coil are possible.
The injector speed offers the ability to input an arbitrarily-shaped electrical waveform to maximize control over the formation of NOx and DPM. Electrical flexibility allows state of the art re-programming of performance while the engine is operating, including tuning of each cylinder. With few moving parts and flexible operation, its simple and compact design cuts cost and enables potential cost-effective replacement of existing injectors, increasing equipment life while cutting emissions and maximizing fuel economy.

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