Towards a two-stroke turbodiesel aero engine

[malc9141]

To HDi: someone did build a prototype piston engine as you suggest in the 1990s. It would have been quite heavy. It never got off the test bench but that doesn't mean it would be no good. But it must be able to meet the skeptics' views if it's to get Certificated.

But what you need for an aero engine in the apparently conflicting requirements of simplicity and sophistication. Simplicity for reliability and costs and weight, sophistication for economic high performance. I think my design - if applied to a multicylinder engine would fit that mould.

To Wayne: I don't know about a Rotary. Interesting idea. Propellers are liable to break with vibration and a rotary would get round that, they're smooth. (My multi cylinder concept - nothing new in more than one cylinder!!! - would be pretty smooth, esp being 2-stroke).
A rotary with modern smooth burning diesel injection technology might work quite nicely.

Malc

[HDi fun]

To Malc - if vibration is a problem then diesel is not the way to go. Diesel cars use a multitude of devices to minimise vibration. Diesels are generally heavier than petrols. And more complex.

[waynne]

Hey - I've had a diesel related idea! Wow it is contagious!

[malc9141]

Well, vibration is relative. The Wilksch 3 cylinder is fine (see www.wilksch.com). But the Renault 4 stroke (car motor put in a plane) was too troublesome. The Centurion is a Merc A series 4 stroke and is OK (just).
A two stroke is smoother, each burn is less explosive than in a 4 stroke ('cos you've only got part of the revolution to do it) but there are twice as many. It's smoother - it's good.
That's why I follow this path. But you're right, you gotta be on the watch.

Malc (What's the diesel related idea??????)

[malc9141]

Actually, now I remember, Mitsubishi spent squillions across the turn of the century on a rotary diesel for light aircraft and eventually gave up. Not sure what the problem was. They used another name for the company (so it didn't seem like a Mitsubishi failing).
Maybe it wouldn't run lean, don't know. Nice idea though.
Malc

They laughed at Eccles

[HDi fun]

Getting it off the ground comes to mind!!

[waynne]

I thought I did the bad jokes HDI!

What about "they couldn't work out whos turn it was?"

[HDi fun]

Originally Posted by waynne

As an aside! Can you theoretically do a rotary diesel engine?

There are certainly diesel powered turbine engines in service daily - they differ little from aircraft jet engines. Jet fuel is broadly similar to diesel, too. Turbines are probably the most perfect rotary engines. Effectively an infinite number of cylinders - hence the phrase 'turbine smooth'.

I'm not sure if you can do a Mazda type of rotary because the injection ports are obscured by the rotor tips at full compression so there's no way to get the fuel in at that time which is what's required by a diesel type engine.

NSU was the innovator behind the Wan*el engine in the 1960's. IIRC, Audi grew out of NSU.

[waynne]

Interesting.

[malc9141]

It was Wnkl rotary engine Mitsubishi was trying to do, unsuccessfully, maybe to do with the reasons you mention.

Jet turbines are beautiful but very costly. There are small aircraft effectively written off cos a sea-gull writes off a jet engine, and replacement cost exceeds value of having the plane earn a living.

(Things here are at a standstill again. It's like treading water).

Malc