Hi Roger,

I am glad to hear you have finally succeeded in the illusive true miniature diesel. I have been following your posts on the other Forum throughout. I regret to say my efforts have fallen by the wayside for a number of years.

You deserve praise for your efforts, and I do hope you will put your work into print.

Regards

Gray,

Are you using any additives to help things along? (edit no he's not)

Even the aircraft industry needs a specific type of fuel, avgas I believe

Good luck with your efforts, it will be intruiging to see how your power outputs progress

Edited By Ady1 on 31/10/2022 17:28:32

Other small model diesels use ether based fuels which ignite very easily, they use the diesel principle but with far more volatile fuel and lower compression

The Germans tried to make aero diesels work in the 30s 40s

You can tank up on a gallon of diesel almost anywhere on the planet which would make a successful small version very desireable, even today

Edited By Ady1 on 31/10/2022 17:39:53

A long while ago, I heard say that a "true" diesel was one using air blast injection. This was the patent originally granted to Diesel himself. This method was later made obsolete by the development of solid injection equipment.

Probably a somewhat archaic distinction these days.

It wasn't just Germany who tried diesel aero-engines; the Americans, amongst others, also gave it a go, e.g.

http://www.enginehistory.org/Piston/Diesels/Ch3.pdf

Most of the contemporary reviews of these machines seem to have been very favourable and its not that clear why they never found wider favour, except perhaps that the 2nd World War came along with much emphasis on the highest possible performance, and subsequently gas turbines clearly became the way to go for all but the smallest engines.

Napiers though didn't let this get in the way of trying to develop a truly wacky diesel based power plant:

https://en.wikipedia.org/wiki/Napier_Nomad

Eric "Winkle" Brown flew one of the Junkers-engined aircraft (I forget which one) and reported, slightly surprisingly, that it was smoother and quieter than a comparable petrol engine. He didn't care for the smell of the exhaust though.

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re. the subject of this thread – that's a fantastic piece of work Roger, was there any special trick to making the pump plunger?

I doff my cap to you, sir. I've always thought it would be pretty tricky making a full-size pump element, let alone 2mm diameter (and with a Proxxon!).

I think part of the problem with constant pressure combustion was that it couldn't be hurried, and so was only (sort of) feasible in very large, slow running engines. Herr Diesel, aiming to use the Carnot cycle, originally intended that his engine should use isothermal compression (realised by injecting water into the cylinder), and isothermal combustion. It would have no cooling system, in fact the cylinder would be insulated. And it would also burn coal dust.

Unfortunately theory didn't translate to a workable engine (partly due to the extreme pressures that would be necessary), so Diesel omitted the isothermal compression, and after much experimentation and discussion with his team, ended up with a practicable cycle that used isobaric combustion. Modern, high speed engines seem to have a combination of constant volume and constant pressure phases.