True Diesel Engine

[weir-smith]

I am in the process of building a true fuel injected engine by trial and mostly error and have made some progress. The basic engine is completed being a water cooled single cylinder 40mm x 80mm stroke and a compression ratio of 20 to 1.

My problems started when I designed my first fuel pump. I wanted to copy the CAV scaled down. At this time it has proved to be too difficult and has been put to one side. Note, all of the machined parts worked well but the cutout on the piston has been my down fall. I have now designed fuel regulation via a needle valve. Most of the parts have been made several times to obtain the required accuracy with me learning along the way. The injector has had six versions, the last failed at 1500 psi taking a lump of concrete out of the workshop ceiling. I am now on version seven and I hope all of the errors in design are behind me.

My question to the Forum, is there anyone who is or has built a true diesel and would be willing to comment on the issues surrounding fuel pumps, injectors and overall construction issues.

Bruce Weir-Smith
Western Australia

 

[deverett]

You might care to watch a couple of YouTube videos of model diesel engines for some ideas:
[ame]https://www.youtube.com/watch?v=zXzqGHn0CDY[/ame]
[ame]https://www.youtube.com/watch?v=-PvZ6S8cadk[/ame]

Find Hansen has his own web site http://www.findsminimodelhotbulbengines.dk/
You could contact him for some first hand info.

Dave
The Emerald Isle

 

[XD351]

There was a series in model engineer a year or two ago on a diesel engine build , a lister engine if memory serves me correctly .
I think you will find making the injector the hardest part as the nozzle holes are super small !

 

[Mechanicboy]

You need the injector tester to test the homemade injector. The injector must atomize fuel very well to be ignited by heat of compression.

There is 2 difference injector: pop of injector as you will find in the automotive diesel engine to example (very difficult to create in workshop) or "vibrating" injector who is less difficult to create in home work shop.

The "vibrating" injector: The injector has a spring loaded injector valve, with a valve head angle of 14 degrees. The valve stem is treaded so that the spring can be adjusted
to the right fuel pressure with one nut, and locked with another nut.

 

[weir-smith]

Thanks to those who have replied so far. I have seen most of the videos on the net relating to model diesels and some of the finished engines are quite good. Unfortunately there is no detail provided in terms of fuel systems.

I have made an injector tester that will go to just over 2000 psi and most of my failures have related to leaks and thread failure hence the redesign now version seven. My problem is not knowing what pressure I should be working toward. My current injector is based on the CAV piston type valve and pintil where the fuel lifts a piston against spring pressure.

Bruce W-S

 

[t.l.a.r. eng]

Sometime back there was a magazine called Strictly I.C. that did an engine build series called the "DUX" If you google Strictly I.C. there site still offers back issues as far as far as I know.

The thing that stuck with me about the build was the unique way he overcame the nozzle orifice. And I believe that engine was a true direct injection diesel.

 

[Mechanicboy]

The Find Hansen diesel engine has "vibrating" injector who is about same principle as the Burmeister and Wain injector as you can see the picture from my book about ship diesel engine. The B&W has 2 angle in the valve seat, the inner angle to keep tight and the outer angle to spread atomized fuel into cylinder. The "vibrating" injector in the Find Hansen has only one angle (14 degree). With right fuel pressure, the fuel will atomize when the valve is "vibrating". You can possible listen to the injector will give the sound about as "RRR"-"RRR"-"RRR" each time you are pumping the fuel into the injector due the valve is vibrating. Tips: Use same piston diameter in the fuel pump as in the injector tester to be sure you get right fuel pressure when the spring is adjusted in the injector with good atomized fuel.

 

[deverett]

Bruce

What fuel are you going/trying to use?
Successful model diesel engines seem to use kerosene for fuel, although there has been one 4 cylinder true diesel running on diesel fuel, but not very well. (Over in Washington state).
The problem is that you can't scale nature and the fuel droplets of atomised diesel oil are not small enough for miniature injectors. Kerosene is finer and therefore more suitable for model work. (So I have been informed).

Dave
The Emerald Isle

 

[Mechanicboy]

Bruce

What fuel are you going/trying to use?
Successful model diesel engines seem to use kerosene for fuel, although there has been one 4 cylinder true diesel running on diesel fuel, but not very well. (Over in Washington state).
The problem is that you can't scale nature and the fuel droplets of atomised diesel oil are not small enough for miniature injectors. Kerosene is finer and therefore more suitable for model work. (So I have been informed).

Dave
The Emerald Isle

The fuel who is used in miniature diesel engine: Kerosene, mixed with 2 % mineral engine oil (to lubricate injection pump and injector)

It has been used turpentine with 2% mineral engine oil in some miniature hot bulb engine.

Low viscosity in fuel will make easier to atomize fuel in small engines.

 

[Jasonb]

Johan Van Zanten did a very nice true diesel, there was a write up over 3 or 4 issues of Medel Engineer about the engine, few pics here

http://www.stoommachine.info/modellen_v_zanten.html#dieselmotor

 

[weir-smith]

To all of the respondents again thanks for your input. Some of the links have been very helpful. The diesel built byJohan Van Zanten is a real credit to his skill.

Dave from the Emerald Isle (spent a few weeks there in 2015 - great place and enjoyed it) the fuel I am using is kerosene. I spoke to a chemical engineer and he advised that the small mass of the engine would not allow the heavier fuels to work successfully unless there was some form of preheating involved.

Jens from Bergen - (on my to do list to visit the Scandinavian Countries. I have been going to Europe for holidays every two years for the last twelve years, going to different countries each time. Perth Western Australia is the most remote city in the world so we are quite isolated from the main stream of things.) The links you have provided have been most useful. One in particular lead me to a site where I was able to down load the original book written by Rudolf Diesel in 1913. The drawings are very detailed however, I need to obtain a German dictionary to work out the detail.

I have had some success with the fuel pump in that I have tested it up to 150 kg/cm2 or approximatly 2000 psi. So small steps forward.

I still have some work to do in respect to the injector. I have ordered a fine (0.5 pitch) tap and die to finish the main body. The injector is very similar in principal to the one you posted which I assume was in your book. So we will see how it goes.

I assume from your comments that you have had a lot to do with marine engines. My experience with them is quite limited. I was a electrical engineer and at various times, worked on diesel generators typically two to six megawatts. The largest was a MAN twelve and a half megawatts and we had four of them plus an additional four "sixe's" and some "two's" which have all been replaced with gas turbines.

Again thanks everyone for your input

Bruce W-S

 

[minh-thanh]

Mechanicboy .

The Find Hansen diesel engine has "vibrating" injector who is about same principle as the Burmeister and Wain injector as you can see the picture from my book about ship diesel engine. The B&W has 2 angle in the valve seat, the inner angle to keep tight and the outer angle to spread atomized fuel into cylinder. The "vibrating" injector in the Find Hansen has only one angle (14 degree). With right fuel pressure, the fuel will atomize when the valve is "vibrating". You can possible listen to the injector will give the sound about as "RRR"-"RRR"-"RRR" each time you are pumping the fuel into the injector due the valve is vibrating. Tips: Use same piston diameter in the fuel pump as in the injector tester to be sure you get right fuel pressure when the spring is adjusted in the injector with good atomized fuel.

View attachment 84049

If no copyright infringement, do you have any more pictures of injectors?

 

[weir-smith]

Minh Thanh

The injectors made by Find Hansen are based on the solid injection style but use a poppet valve rather than a conventional pintle or spray valve. The problem is the scale involved and the pressures required. Find Hansen has not to my knowledge provided any technical information re his injectors except to the fact that he has made them work on his models which is commendable.

My injectors are of the pintal type and operate at around (e.g. pop off) 2000 psi. The pump I am using is capable of an injection pressure of 4000 psi as measured.

As far as drawings of injectors that are not subject to copyright try down loading any of the following books on which the copyright has expired.

1. Diesel Engines for Land and Marine Work by A. P. Chalkley
2. Oil Engines, Details and Operation by Lacey Harvey Morrison
3. Marine and Stationary Diesel Engines

Bruce W-S

 

[minh-thanh]

weir-smith !
Thank you for the advice on finding the book
I searched and downloaded .
And the link for those who need:
https://archive.org/search.php?query=subject:"Internal combustion engines"

Minh Thanh
My injectors are of the pintal type and operate at around (e.g. pop off) 2000 psi. The pump I am using is capable of an injection pressure of 4000 psi as measured.

Bruce W-S

And if you don't mind, do you have any images of your injectors and pumps ?
Thanks !

 

[H Pearce]

Hi All,

I fee that this would be a good time to bring up some safety.
Liquid under high pressure can be extremely dangerous. This is due to the possibility of it being pushed through the skin and in to tissue. The effects will not be noticed for some hours, But almost always require surgery. if you suspect this may have happened to you even for a very small amount of fuel, please go immediately to the hospital emergency room, sooner the better. The pressures being mentioned in this thread are more than high enough to do this.
fortunately it is relatively easy to avoid, the high pressure will not travel very far in open air, So keeping fingers a couple of centimetres away for any pressurised system should be enough. Running your finger over a joint to check for a leak....... not so good.
If you have a strong stomach google high pressure injection injury.
I have made my staff view some of these pictures as part of safety training, stops the clowning around and focused their attention! (and if you want to be a ..... show them when they turn up to work hungover)
Fortunately modern engines have most of these high pressure systems designed in such a way that it is much less likely. Older engines not so much.
Sorry to be the downer here. It’s just a Type of hazard that has stuck in my mind.

 

[minh-thanh]

H Pearce !
Thank you for reminding me / us of this ! (I had a bad experience with sparks and gasoline)

 

[H Pearce]

H Pearce !
Thank you for reminding me / us of this ! (I had a bad experience with sparks and gasoline)

Hi Minh,
Welcome, I’m not sure if it is a commonly known danger or not. So thought it worth while bringing it up seeing people are working with these pressures.
It’s also worth mentioning that sometimes it is not really possible to see the spray so you shouldn’t touch a high pressure line in operation. Something I’m sure most of us have done at some point, I know I have.

Regarding injectors and pressure. With the current push for lower emissions allot of work has gone in to the combustion process in a Diesel engine. Using electronic injectors they are able to have pre, main and post TDC injection all in seperate highly controlled timing and volume, I think MTU is currently using 5 seperate injections per combustion. To assist with the high speed and atomisation, injector pressures have been steadily increasing. Last I heard they were up to 2,200 bar and heading for 3000. It makes for some highly stressed and often short lived components.

If you ever get a chance to get up close to a large engine at full power...... it’s not something you will ever forget!

My last “Baby” had 2x 4Mw V16 with 8 turbochargers.... standing between a pair of them As they slammed up through the turbine stages..... a full body experience.

 

[mcostello]

If You show Your hung over employees a nasty picture You are not being an a.......... That might be the most sensible thing They have ever seen. Got to get to Them any way possible.

 

[weir-smith]

Minh Thanh

Here are a couple of photos of the injector.

Bruce

 

[H Pearce]

Hi Bruce,

Very nice work.