QUOTE(Dr Evil @ Mar 15 2013, 09:04 PM)
If one could develop electrical actuators that could tolerate the heat, I think electrical would be smaller, better, need less auxiliary parts like an air tank, much more precise to tune, etc. There may be a weight difference between pneumatic and electric actuators, but it may be negligible if viewed in gestalt.
QUOTE(Dr Evil @ Mar 15 2013, 09:04 PM)
If one could develop electrical actuators that could tolerate the heat, I think electrical would be smaller, better, need less auxiliary parts like an air tank, much more precise to tune, etc. There may be a weight difference between pneumatic and electric actuators, but it may be negligible if viewed in gestalt.
Evil, that's exactly what EFI fuel injectors are- a solenoid that has an electrically actuated coil that moves the injection pintle whenever power flows to the injector. If they can do this for a fuel injector in the same environment, they can do it for a valve.
Unfortunately, solenoids work backwards in that they generate an initial low force at the beginning of a stroke, and maximum force at the end of the stroke. So if you have a solenoid hooked up to a valve, it has a low force to start the valve to move, and then, right before the valve slams to a stop in the full open position, the force hits a maximum.
In the attached graph, the maximum force curve is for a 10% duty cycle (turned on 10% of the time), and the worst force curve is for a continuous duty cycle (full on). Notice at the beginning of the actuation (right side of the graph) the force created to open the valve is a pathetic .1-.4 kgf. The maximum stroke is on the left side of the graph and the valve slams to a full open stop at about 2mm line on the graph. So, the force application is backwards with a solenoid.
I've used solenoids in products, but had to allow the solenoid to free flight initially to move up the force curve. Once the force was sufficient, I’d smack the moving solenoid into a stationary object that needed moving. If a solenoid is used to hold the valve closed, the coil heats up and the solenoid force curve moves to the worst case/lowest force of the continuous on position.