Fuel Injection Systems Part 2

[Admiral_dk]

The last one looks really good - I hope that it will perform well too 

Per         

[Roger B]

Thank you both 

Pirmin, I decided to use commercial springs for my injection experiments for consistency and to allow others to purchase the same springs if they want to reproduce my work. I have measured the release pressure by measuring the force on the plunger of my test pump. The successful injectors open at around 90-100 bar.

I lapped the two new injector needles with 5 micron diamond paste, allowing the body to float around, and gave then a cleanup in the ultrasonic bath.

The tests were rather disappointing      I took one of the older 1.4mm units as a test which worked well as before:


<a href="https://www.youtube.com/watch?v=IuGWteDWUsQ" target="_blank">http://www.youtube.com/watch?v=IuGWteDWUsQ</a>


Both the new units gave a poor, very wide angle, spray   


<a href="https://www.youtube.com/watch?v=r09Fqx1yAJo" target="_blank">http://www.youtube.com/watch?v=r09Fqx1yAJo</a>


<a href="https://www.youtube.com/watch?v=17xV4S2k3D8" target="_blank">http://www.youtube.com/watch?v=17xV4S2k3D8</a>


I think I will need to make some new needles with a shallower angle   

[Minh Thanh]

 
maybe ...Try a larger spring - more force - may improve spraying ...!!?

[Admiral_dk]

Honestly Roger - I don't think this last endeavor being a lost cause ...!

As I see the video - it looks like you got the Atomizing down to very small droplets this time
+ I wouldn't be surprised if some Engines would run reasonably well with this Injector ....

That said - I do find it surprising to see the Spray-Pattern look almost like a Disk    - so not for the Junckers 

Would be nice if you have access to a very High-Speed Video-Camera ....
That would allow you (and us) to see what is going on in much better details ....

Per       

[Roger B]

Thank you both 

These are certainly not a lost cause, just part of a long series of experiments. Different engines need different styles of injectors.

[Zephyrin]

I stumbled across this website, which you probably already know, but this model maker uses an electronic card to manage fuel injection in his engines...
and he uses also a cheap commercial injector from motorcycle, I will buy one to see just to see what's inside, for now...

<a href="https://www.youtube.com/watch?v=aoINEoMGf6s" target="_blank">http://www.youtube.com/watch?v=aoINEoMGf6s</a>

[Minh Thanh]

. This may be where Find Hansen's small injector shows it's benefits     

 Hi Roger !
I thought for a long time after I read your topic
_ I don't like to interfere or hinder the fun in the hobby
So...., If you rely on Mr. Find's injection results, consider one issue: the amount of fuel per injection
With the amount of fuel per injection that you have calculated and proven and compare it with the amount of fuel injected from his video - You will see a huge difference.

[Laurentic]

interesting post Zephyrin, but you need to be switched on for that electronic control system, I might struggle with that!

Chris

[steamer]

I pointed that one out a while back.  Ordered an injector for inspection. And then the tariff caflufal happened and I had to cancel the order.

[Roger B]

Thank you Minh 

Find Hansen’s video clip shows the injector being fed by a test pump which delivers much more fuel than would be used in a running engine. The details on here state a 2mm pump plunger and a working stroke at idle of 0.03mm.

https://findsminimodelhotbulbengines.dk/Aboutmymodelmaking.html

Those are similar dimension to the ones on my engine. He also states that the injector needle is 0.9mm diameter which is similar to my latest design.

I met with Daniel Hunziker at an exhibition in Switzerland and was asking him about his fuel injection experiments. The single cylinder engine was built as a test bed for his fuel injected VR5 engine. He is using the injector from a Honda Monkey motor bike, which is, I think, 150cc. The pulse time is around 4 milliseconds and he said he is using methanol and glow plug ignition as it is much less sensitive to mixture variations than petrol/gasoline and spark ignition.

[Vixen]

He said he is using methanol and glow plug ignition as it is much less sensitive to mixture variations than petrol/gasoline and spark ignition.

+1 for methanol being far less sensitive to mixture strength than petrol. Almost any methanol mixture strength will ignite. Whereas the petrol mixture strength needs to be within tight limits. Another advantage of methanol may be with the higher flow rates through the injector.

Surely, the Honda Monkey Bike would use a low pressure indirect port injection, whereas you are striving for high pressure direct injection into the combustion space. I do not believe methanol will combust on compression alone, hence the glow plug.

Mike

[Minh Thanh]

Thank you Minh 

Find Hansen’s video clip shows the injector being fed by a test pump which delivers much more fuel than would be used in a running engine. The details on here state a 2mm pump plunger and a working stroke at idle of 0.03mm.

https://findsminimodelhotbulbengines.dk/Aboutmymodelmaking.html

Those are similar dimension to the ones on my engine. He also states that the injector needle is 0.9mm diameter which is similar to my latest design.

That's the problem, if someone is trying to test the injector with "enough fuel" to run the engine and expect the result like that

  The 0.03mm stroke: I don't believe he can do it - never ......
Why?? Suppose a fuel pump system consists of 5 parts ( plunger , cylinder , camshaft , governor , control lever ) then their tolerances :
A + B + C + D + F < 0.03 mm
Because you can not take one or several parts with tolerance = or > 0.03 mm to control the result of 0.03 mm
Just like a lathe with a tolerance of 0.02 then you can not create a part of 0.01 or 0.005 mm
Suppose their tolerances are equal then the tolerance of each part = 0.03 /5 = 0.006 mm
You watch his video when assembling you will see all the parts cannot reach the tolerance of 0.006 mm then how can they control 0.03 mm of stroke
 A vibration of the engine while running also affects the stroke by 0.03 mm.
and some other problems....

[petertha]

Surely, the Honda Monkey Bike would use a low pressure indirect port injection, whereas you are striving for high pressure direct injection into the combustion space. I do not believe methanol will combust on compression alone, hence the glow plug.

You made me curious what the fuel mixture was for classic compression / tommy bar / 'diesel' engines. I only saw them running at the flying field when I was a kid & that was many years ago now. I recall the exhaust had a particular odor - amongst other particular odor's LOL. Anyway, not sure if this is a popular recipe. 'I used my standard small-engine test fuel of 35% kerosene, 35% ether and 30% castor oil, with 2% added cetane booster.'

https://www.modelenginemaker.com/index.php?action=post;quote=295566;topic=10603.165

I wonder if Find has a unique fuel recipe? I have not really followed the videos much lately but I gather there seems to be some mystique around how & why it runs; some details left out of the description or something to that effect? I guess that's a different subject & each to their own I suppose.

[Roger B]

Hello Mike,

You are quite correct, I was commenting on the video that Zephyrin had posted.

Hello Minh,

As Find Hansen is using a feedback governor which will compensate for the tolerances he could end up with such a small working stroke although I agree it does seem rather small, 0.3mm is a more reasonable figure if allowing for losses.

Hello Peter,

Find Hansen says that he uses Kerosene with a small addition of 2 stroke oil. The critical part which he does not give much details for is the injector.

[Minh Thanh]

Hello Minh,

As Find Hansen is using a feedback governor which will compensate for the tolerances he could end up with such a small working stroke although I agree it does seem rather small, 0.3mm is a more reasonable figure if allowing for losses.

 I wish he was here and could prove his pump system can control 0.03 mm stroke or fuel volume : V = 3.14.r.r.h = 3.14 x 1 x1 x 0.03 = 0.0942 mm3 
That is a crazy - illusion claim !!! 
Let's stop here and get back to your topic !!