Fuel Injection Systems Part 2

[Admiral_dk]

I see that you turn to KISS - 'Keep It Simple Stupid' ....
.... and it has saved my bacon on a number of times, too ...! 

Come to think about it - your new aproch might work even better with an 'Indirect Injection System' .... if you got the room for it .... 

Per       

[steamer]

Not much special about the body, the bore was reamed 2mm and the ball seating was lapped with a 3mm diamond ball lap.

The injection seems to be more of a squirt than an atomisation with the hand test pump:

<a href="https://www.youtube.com/watch?v=S9XOfphk89w" target="_blank">http://www.youtube.com/watch?v=S9XOfphk89w</a>

<a href="https://www.youtube.com/watch?v=fS5owr5DIJQ" target="_blank">http://www.youtube.com/watch?v=fS5owr5DIJQ</a>

A mushroom injector appears better:

<a href="https://www.youtube.com/watch?v=9D-_l4zTTv0" target="_blank">http://www.youtube.com/watch?v=9D-_l4zTTv0</a>

As does the latest needle injector:

<a href="https://www.youtube.com/watch?v=V5M0mXQIXQ8" target="_blank">http://www.youtube.com/watch?v=V5M0mXQIXQ8</a>

Hopefully I can do some running trials in the next couple of weeks 

Hey Roger,
Just an observation, the nozzle in your test video is hanging at the end of a copper tube....and I'm noticing it's vibrating.     That vibration is going to have a fairly significant effect on you paper spray pattern.    If you're counting on that....just sayin....
Dave

[Roger B]

Thank you both 

Per, I have thought about indirect injection, it makes the injection theoretically easier but increases the heat loss due to a larger surface area combustion chamber. The current four stroke diesel combustion chamber is about as small as it can be. There's a poster on HMEM i am following who is looking at building an indirect injection diesel.

Dave, I'm not too worried about the actual pattern at the moment, just the atomisation. Previously while I was trying to work out how to keep everything concentric it was important and someone (possibly Per?) pointed out the vibration of the pipe. The spray from the needle and mushroom injectors lights easily, the jet from the open nozzle just makes my lighter oily. With a much faster pressure rise in an engine turning at 2000 rpm rather that me pushing the handle on the test pump things may be different     

[Admiral_dk]

I can only agree on the heat loss - was just thinking out loud ....

Best wishes     

Per

[Roger B]

I had a quick trial with these injectors today. The workshop I use has been reorganised so the area I can use has a parquet floor rather than concrete so my 'workmate' is rather more lively.

A cold start with the needle injector was as good as last time, supporting the airlock theory.

<a href="https://www.youtube.com/watch?v=nHYDfQaNw98" target="_blank">http://www.youtube.com/watch?v=nHYDfQaNw98</a>

The open injector would not fire properly at all, there was some light blue smoke and a few pops but nothing useful. Most of the fuel came straight out of the exhaust 

<a href="https://www.youtube.com/watch?v=f6O0ms1kg7c" target="_blank">http://www.youtube.com/watch?v=f6O0ms1kg7c</a>

As a confirmation I refitted the needle injector which performed as before.

<a href="https://www.youtube.com/watch?v=nynKOU7mE0E" target="_blank">http://www.youtube.com/watch?v=nynKOU7mE0E</a>

If you look carefully you can see the fuel leaking past the needle coming out of the hole in the spring adjusting screw. Maybe I need to add a return pipe.

[Admiral_dk]

Easy starting with the old model Injectors 

If you look carefully you can see the fuel leaking past the needle coming out of the hole in the spring adjusting screw. Maybe I need to add a return pipe.

Considering that this engine isn't using much fuel (or most likely not doing so) - it is certainly a percentage lost that way. It appears to contain some polutants too - so if you decide to do so, run it through a filter ...

I guess that you already have a seal where it leaks .... 

Per     

[Roger B]

I have been discussing fuel injection with another member on here and started thinking about my last diesel trials.

The engine ran with the injection needle jammed open so I assumed that the fuel was being atomised via the 0.2mm orifice. I made an open nozzle with a 0.2mm orifice and tried that without any success. I now think that the needle jammed partially open and the atomisation was due to the small opening, but how small?

I decided to try and measure the needle lift for both the needle and mushroom injectors. The test pump was set up and primed with lamp oil (like diesel but not so smelly) and I set up a DTI to attempt to measure the lift. There was nothing measurable  Any movement of the indicator needle seemed due to the lack of rigidity of the simple set up. This suggests that the lift is just a few microns and the fuel is atomised by this gap. Lots more to think about 

<a href="https://www.youtube.com/watch?v=4ylfLu_BJJY" target="_blank">http://www.youtube.com/watch?v=4ylfLu_BJJY</a>

<a href="https://www.youtube.com/watch?v=x84gqNyPM6w" target="_blank">http://www.youtube.com/watch?v=x84gqNyPM6w</a>

[Brendon M]

Hello Roger,

Could you instead make a "micrometer" style setup where you can gradually decrease the gap to the point where it starts running?

[Roger B]

Hello Brendon,

Technically yes, but I would run out of hands holding the drill, adjusting the fuel rack and adjusting the injector. Maybe it would be easier when I fit a governor the look after the fuel rack I also suspect the gap may be speed dependant so adjusting the spring may be more practical

As I have said many times I am making this up as I go along, all thoughts and ideas are most welcome