Compression ignition

[Kegan]

Thank you for the discussion.

I suppose if I build a "true" diesel of sorts and used a commercially available injector I could scale the model to suit. Right now its a pipe dream.
If only Mr. Find Hansen would let us in on some of his secrets but if can build small models that work I am sure over time I could theoretically do the same.

 

[minh-thanh]

If only Mr. Find Hansen would let us in on some of his secrets

He kept it a secret...I respect that, It's no problem for me. But don't barrage people with stupid information !!

 

[minh-thanh]

Let me ask, does the small, model diesel engine's diminished mass cause a common inability to create and maintain enough heat within the combustion space to begin the compression ignition process, requiring all true diesel compression ignition model engines to use alternative fuels? Would using a glo-plug be considered cheating?

I use kerosene and diesel and the engine still runs fine
As long as the compression ratio is at least 18-1 it's fine
With a lower compression ratio, flammable fuel or fuel mixture should be used
Using a glow-plug is not a problem if you need a running engine. - The most important thing is that the engine must run - other issues, improving it... are not a problem.

 

[The Ignoble Troll]

I use kerosene and diesel and the engine still runs fine
As long as the compression ratio is at least 18-1 it's fine
With a lower compression ratio, flammable fuel or fuel mixture should be used
Using a glow-plug is not a problem if you need a running engine. - The most important thing is that the engine must run - other issues, improving it... are not a problem.

What kind of RPM do you get?

Does it produce usable power or is it more of a proof of concept?

 

[Lloyd-ss]

A few people on the forum (MT) have successfully built true diesels, but it ain't easy.

Regarding fuel atomization, it can be done. I am working on a 2 stroke diesel patterned loosely after the Detroit Diesel series of engines. I finally got the unit injector (HP pump and injector combined into a single unit) to work more-or-less to my satisfaction. I have about 6 other injectors in the scrap box. Difficult learning curve.

Here is a video of the cylinder head mounted on a solid block, with the injector being driven by an electric motor via camshaft and pushrod. I had to turn the fuel delivery volume up excessively high to get a decent picture of the cloud of diesel fuel. It is regular highway diesel. The push rods for the 2 exhaust valves are removed so as not to confuse the image with the valves moving around.

 

[The Ignoble Troll]

A few people on the forum (MT) have successfully built true diesels, but it ain't easy.

Regarding fuel atomization, it can be done. I am working on a 2 stroke diesel patterned loosely after the Detroit Diesel series of engines. I finally got the unit injector (HP pump and injector combined into a single unit) to work more-or-less to my satisfaction. I have about 6 other injectors in the scrap box. Difficult learning curve.

Here is a video of the cylinder head mounted on a solid block, with the injector being driven by an electric motor via camshaft and pushrod. I had to turn the fuel delivery volume up excessively high to get a decent picture of the cloud of diesel fuel. It is regular highway diesel. The push rods for the 2 exhaust valves are removed so as not to confuse the image with the valves moving around.

View attachment 155958

Two stroke as in a forced draft 2 stroke, like trains use?

 

[Lloyd-ss]

Two stroke as in a forced draft 2 stroke, like trains use?

Yes, with a roots blower like Greyhound buses, diesel trucks, lots of marine and stationary engines, and of course trains with the always disastrous run-away blown diesels.

Here is the build thread for the project. I have been stalled on it for a while, but now that I have the blower, head, unit injector ( ), low pressure fuel pump, and flywheel completed, I might be past the half-way point, but the project continues to be full of surprises . I should have started with a kit for a simpler engine, or an air powered steam engine, but where is the fun in that, LOL? Now I can spend 4 times as long and get one fourth the engines.

Here is the project. You might start by looking at posts #85 and #149
The thread title says it all.

https://www.homemodelenginemachinis...-56cc-2-stroke-will-it-ever-work.31110/page-5

Lloyd

 

[The Ignoble Troll]

Yes, with a roots blower like Greyhound buses, diesel trucks, lots of marine and stationary engines, and of course trains with the always disastrous run-away blown diesels.

Here is the build thread for the project. I have been stalled on it for a while, but now that I have the blower, head, unit injector ( ), low pressure fuel pump, and flywheel completed, I might be past the half-way point, but the project continues to be full of surprises . I should have started with a kit for a simpler engine, or an air powered steam engine, but where is the fun in that, LOL? Now I can spend 4 times as long and get one fourth the engines.

Here is the project. You might start by looking at posts #85 and #149
The thread title says it all.

https://www.homemodelenginemachinis...-56cc-2-stroke-will-it-ever-work.31110/page-5

Lloyd

You just absolutely made my day. I've always wanted to see a miniatureized blown 2 stroke but to the best of my knowledge there were no running examples. I wish you the best of luck with yours and look forward to following the build thread!

 

[weir-smith]

In respect to building a true model diesel, this has been an interesting discussion with some informative comments.
I have written about my experience previously regarding building a true model diesel but here is a condensed version. I started out with a basic design of an engine with an 32 mm dia cylinder and a 65 mm stroke. The build was somewhat over the top in terms of robustness and I was quite happy with the result. While everyone advised that it couldn't be done, I was quite determined. I made a total of 11 jerk pumps trying to achieve 2000 psi and the best I could achieve was around 1200 psi. I had to add additional bearings either side of the pump to avoid bending of the shaft. After studying commercial pumps I decided to purchase a the smallest pump I could find. I tested it on my pump setup and it could easily attain a pressure of 3000 psi which was the limit of my gauge. I then machined as much off as I could and fitted it to the engine. Somewhat out of scale but it worked.

Then came the injector where quite a few were made. Where surfaces were butted together, they were surface ground. The results were mixed in terms of atomisation. I ended up using an 8mm dia commercial nozzle of the pintal type which consisted of the body and the pin. Again a little out of scale but it worked consistently.

The next problem was not enough compression. To obtain ignition on diesel you need in excess of 500 psi compression and when measured, I was well below that. I remade the valves and fitted an extra three rings to the piston making a total of six. I now had plenty of compression such that you needed a large crank handle to turn it over.

I did managed to get the engine to run on diesel but it was inconsistent and after working on the project for two years, I put it all down to experience. Using lamp kero the engine would run consistently if not somewhat difficult to control. It would either run too fast or too slow and stop. You can use fuels that have a lower ignition point which makes life easy typically the 30/70 model aircraft fuel but it's not diesel.

The problem is, you can scale an engine but you can't scale the physics which remain constant. I then moved on to air blast injection and that is another story all together.

Bruce WS

 

[GreenTwin]

We started making patterns for a small replica of Diesel’s first experimental engine earlier this year. Several weeks ago I was hit by a stroke which initially paralysed my right side but now just affects my arm and hand. Hopefully as time progresses I will gain more use and be able to finish it.

We intend to use direct injection rather than air blast and have had some wonderful advice from Roger B over at MEM.

Some 25 years ago I built a 1/4 scale replica of a 2-1/2 HP Hornsby Akroyd oil engine. The engine wasn’t a particularly good runner so rather than have disappointed customers I shelved the project. Only 2 were built. I had no problem making either the high pressure oil pump or the injector. ( other than needing a little magnification )

Cheers Graham.
View attachment 155948

Sorry to hear about your health issues.
That is a bummer for sure.

.

 

[GreenTwin]

Thank you for the discussion.

I suppose if I build a "true" diesel of sorts and used a commercially available injector I could scale the model to suit. Right now its a pipe dream.
If only Mr. Find Hansen would let us in on some of his secrets but if can build small models that work I am sure over time I could theoretically do the same.

Find Hansen posted on his website exactly how he made his injector.

He tried several configurations, and finally came up with (as I understand it) a tiny valve, much like the typical mushroom valve on an IC engine.
He said this arrangement was necessary to prevent the cylinder pressure from flowing back into the injector.

Find's fuel (diesel I assume) pushes the valve open, I think by pressure alone.
The head of the valve faces into the cylinder, just like a standard IC valve, and so pressure from the cylinder keeps the valve closed until the pump pressure forces it open.

I have photos of his test rig and his injector.
It was all posted on his website, and may still be posted there.

Edit:
Photos of Find's injectors are shown at this link.

https://craftsmanshipmuseum.com/artisan/find-hansen/

This page shows his injector test stand.

https://craftsmanshipmuseum.com/artisan/find-hansen/find-hansen-photos/

Injector pump is shown here.

https://findsminimodelhotbulbengines.dk/engineparts/index.html
.

Find mentions that his diesel engines run better on kerosene than on pure diesel.

Edit: Supposedly his compression ratio is 21:1.

The injector is shown at 21:50 in this video.

 

[minh-thanh]

Like I said: Rely on his design but don't take his information .

.

Find mentions that his diesel engines run better on kerosene than on pure diesel.

I don't believe any of the information.
Remember one thing : The self-ignition temperature of kerosene and diesel is 210, 220 degrees Celsius !!!!!

 

[GreenTwin]

I have tried using kerosene and diesel as a foundry fuel, and have found that kerosene is a lighter fuel than diesel, and it lights/flashes much more easily than diesel.

I consider kerosene a borderline unsafe fuel for foundry work just because of how easily it flashes when you light the burner, compared to diesel.

I would assume the same effect would be noticeable in a model diesel engine, since you are atomizing the fuel with an injector in a very similar manner as atomizing the fuel with a foundry burner, but that is just a guess.

.

 

[Kegan]

He kept it a secret...I respect that, It's no problem for me. But don't barrage people with stupid information !!

You were referring to Mr. Hansen correct?

 

[minh-thanh]

I have tried using kerosene and diesel as a foundry fuel, and have found that kerosene is a lighter fuel than diesel, and it lights/flashes much more easily than diesel.

I consider kerosene a borderline unsafe fuel for foundry work just because of how easily it flashes when you light the burner, compared to diesel.

I would assume the same effect would be noticeable in a model diesel engine, since you are atomizing the fuel with an injector in a very similar manner as atomizing the fuel with a foundry burner, but that is just a guess.

.

You can google about flash point and self-ignition point of kerosene and diesel .
And they are completely different.
I don't remember where I posted it

You were referring to Mr. Hansen correct?

Like I said: Rely on his design but don't take his information .

I don't believe any of the information.
Remember one thing : The self-ignition temperature of kerosene and diesel is 210, 220 degrees Celsius !!!!!

As I said once before. , It's everyone's right to share or not, and I respect that, But don't confuse people, Don't give out information ...that makes others think diesel engines are impossible to build.....
And if I believe his information, I probably won't be able to build a diesel engine., Because I would have given up before I even started .
Maybe some people won't like my comments , But with me, When you come to your hobby with lies : that is unacceptable, no matter who it is !!

 

[Kegan]

I have tried using kerosene and diesel as a foundry fuel, and have found that kerosene is a lighter fuel than diesel, and it lights/flashes much more easily than diesel.

I consider kerosene a borderline unsafe fuel for foundry work just because of how easily it flashes when you light the burner, compared to diesel.

I would assume the same effect would be noticeable in a model diesel engine, since you are atomizing the fuel with an injector in a very similar manner as atomizing the fuel with a foundry burner, but that is just a guess.

.

I have seen a video ...dont

You can google about flash point and self-ignition point of kerosene and diesel .
And they are completely different.
I don't remember where I posted it



As I said once before. , It's everyone's right to share or not, and I respect that, But don't confuse people, Don't give out information ...that makes others think diesel engines are impossible to build.....
And if I believe his information, I probably won't be able to build a diesel engine., Because I would have given up before I even started .
Maybe some people won't like my comments , But with me, When you come to your hobby with lies : that is unacceptable, no matter who it is !!

I'm quite new to the hobby and the site in terms of contribution and I was a little confused at your comment and thought perhaps I had said something wrong. I know I have a lot to learn but I hate being put off. Don't tell me I cant do something, help me figure out how I can.
Thank you for everyone's contributions, most informative and interesting.

 

[Kegan]

I have tried using kerosene and diesel as a foundry fuel, and have found that kerosene is a lighter fuel than diesel, and it lights/flashes much more easily than diesel.

I consider kerosene a borderline unsafe fuel for foundry work just because of how easily it flashes when you light the burner, compared to diesel.

I would assume the same effect would be noticeable in a model diesel engine, since you are atomizing the fuel with an injector in a very similar manner as atomizing the fuel with a foundry burner, but that is just a guess.

.

I saw a video a while back, I think a bloke from Oz who built a nice foundry/furnace and he spoke of mixing a bit of kerosene with the diesel. I have no personal experience yet but hopefully soon.

 

[minh-thanh]

Don't tell me I cant do something, help me figure out how I can.

If you want to build a diesel engine
Some information for you...it will help you be more confident

https://www.homemodelenginemachinist.com/threads/mini-diesel-engine-new-discussion.35396/

Building a diesel engine: Possible !
What's really important is: Experience, meticulous attention to every smallest detail
You can use any fuel as long as the engine is running.
Don't worry too much about fuel, glow-plug... Get the engine running and it will tell you what it needs to be better.

 

[Lloyd-ss]

I occasionally need to refer back to the opening post of the topic to see what question the original poster asked.
Lloyd

 

[peterl95124]

Like I said: Rely on his design but don't take his information .

I don't believe any of the information.
Remember one thing : The self-ignition temperature of kerosene and diesel is 210, 220 degrees Celsius !!!!!

I have a hard time understanding what you're complaining about here, Hansen's
fuel choice, his compression ratio ?, his injector design ?, his pump design ?

here are some fun facts from thermodynamics, compression ratio, pressure ratio PSI, and Temp, for gasoline engines in the 6 to 12 CR range and diesel around 20
6:1 12:1 166 psi 625-F (for the non-imperialists, ~12-bar, ~330-C)
12:1 32:1 462 psi 972-F
20:1 66:1 960 psi 1780-F (ditto, ~66-bar, ~970-C)

there's a huge disconnect between the supposed self-ignition of gasoline and diesel or kerosene compared with the air temperature in the chamber at peak compression, so I don't think you can use the self-ignition temperature as a design point for any engine, since if you take those numbers seriously then gasoline engines would not need spark plugs (and they would knock like heck) ?

Also, I believe(?) that good atomization is easier with a lower viscosity liquid, so am ready to believe that kerosene worked better than diesel for Hansen ?