Our Simplified Solution was to treat the problem at its source – in the cylinder – by creating the world’s first fully controllable “programmable” fuel injector.
Magnetostrictive Transducer:
(A replacement for a solenoid or piezo actuator.)
The heart of our injector lies in the programmable high-speed transducer. A smart material rod, made of a rare earth alloy sold commercially as Terfenol-D, is highly compressed by fuel pressure from the common rail fuel system and surrounded by a minimal number of electrical coil turns. When the coil is energized, a magnetic field is created through the Terfenol-D rod that allows it to lengthen proportionally with the magnitude of the field, thereby making it a perfect candidate for use as a hydraulic actuator.
Terfenol-D is a unique material in that it is easily able to withstand limitless cyclic loading without fatigue issues. It was developed originally for the U.S. Navy in the 1960’s for SONAR applications by the U.S. Government AmesLab facility in Ames, IA.
Our application of Terfenol-D is unique to other designs in that we've discovered its greatest potential lies in the pre-loading of the alloy itself. Specifically, the best performance of the alloy is seen by compressively pre-loading it with large pressures directly (such as 30,000 PSI), not by loading it lightly as would be done with a Solenoid or Piezo design.
This high pre-load is the key in our application in that it allows a number of benefits that increase the speed of the injector itself because the pre-load actually changes the Young's modulus of the material. As such it allows removal of the need for springs that would only add mass, size, friction, and unwanted dynamics to the system and helps to reduce magnetic permeability, which in turn reduces the voltage required to establish current throughout the coil.
In its standard composition, Terfenol-D will display performance degradation issues at the extremes of the temperature operating range expected for a standard production vehicle in use all throughout the world. To accommodate this known issue requires slightly adjusting the constituent proportions of the alloy mixture itself, allowing the temperature operating range of the Terfenol-D to fall into the desired range, while still maintaining all of the attractive properties of the standard composition. This re-formulation is done via application of U.S. Patent 6,758,408, authored by Perry Czimmek. For simplicity of testing purposes, our in-house testing of the material has used the readily available "standard" composition.
Spool Valve:
(A replacement for the needle valve.)
During the design phase of our transducer we discovered that the speed of the transducer actuation was exceeding the capability of the opening of the needle valve of the injector. In simple terms, the needle valve could not move out of the way quickly enough to keep up with the speed of the transducer.
As a result, our injector does not use a traditional needle valve to block the fuel passage ways, but instead uses an underlapped spool valve (typically found in aircraft hydraulic systems.) This solved the "speed" problem of the needle valve immediately but also created an unintended (but extremely beneficial) consequence; the ability to open and close the fuel passages almost instantaneously, giving a sharp start and stop to the fuel flow, which is specifically what needs to take place to reduce the generation of NOx and DPM.
Unlike a traditional needle, an underlapped spool valve does not require the need to "slow down" upon closing to prevent impact with the needle seat. Using our design, the spool can pass directly by the fuel passages at full speed, and then be slowed to stop. The result is the ability to crisply start and stop the fuel flow, and when used in combination with the magnetostrictive transducer it can be accomplished in a multitude of injection events or in one long, infinitely adjustable rate shaping event.
U.S. PATENTS
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Great Plains Magnetostrictuve Fuel Injector
Prototype Test Unit - Scout 1
Magnetostrictive Transducer
Spool Valve - Closed Position (Yellow Fuel Passages are Blocked)
Spool Valve - Open Position (Yellow Fuel Passages are Unblocked) |