Peak Cylinder Pressures 1

[ip308]

Hi guys,


Just a quick question,

was wodnering what kind of figures would be reasonable to assume for peak and mean pressures of the power strokes in a high BMEP engine

A bit of searching, ive find figures of around 50 bar for peak pressures, is this sensible?


Thanks

 

[xlch58]

tbuelna,

Why did your team chose to run the pistons out of phase rather than move the ports, or alter their shape. Seems the balance issue would be a big penalty to pay. Is it normal for opposed piston engines to run their pistons out of phase?

Charles

 

[BrianPetersen]

Two-stroke opposed-piston engine. You want the exhaust port to open first and close first. That's only possible by having the opposing pistons slightly out of phase.

Yes, you can do it the way a normal two-stroke does it, with the pistons in phase, but why not take advantage of the ability to have unsymmetrical timing?

 

[tbuelna]

turbomotor,

I don't know how you lasted longer with the good doctor than I did.

Of course, now I'm working with a relatively pedestrian 12,000 hp turboshaft drivetrain. Much more power...... but less vibration!

 

[HiPerTEC]

EdDanzer,

We started out looking at extracting power through a reciprocating generator design, but most people wanted a mechanical extraction system in order to reduce size and weight. We designed and fabricated a mechanical conversion unit that changes reciprocating motion to rotary motion. This unit is not a slider crank design, but uses very fast acting one-way clutches to engage and disengage the rotary power output shaft from the free piston engine. We are in the middle of the investigation on this power extraction unit, but so far things look very promising.

The valves in our 4-stroke free piston engine are pneumatically actuated, and are independently controlled with our control system for the engine. The valves are pneumatically controlled in for opening and closing (no springs). We have designed very high speed pneumatic control systems for some of our rocket thruster programs. Our actuators can run about 4000 rpm in 4-stroke mode at the moment. We have a new design being fabricated now that will push us over 10,000 rpm in 4-stroke mode. We went with pneumatic actuators because of the smaller size and weight compared to electro-mechanical actuators. Plus we use the air through the system to help cool parts of the engine.