Author Topic: Fuel injection systems  (Read 68602 times)

Offline Brendon M

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Re: Fuel injection systems
« Reply #300 on: October 26, 2020, 11:16:36 AM »
Not exactly easy to get them that long, slim, precise and with good finish ....

I know I can't do it with what I got - but 'cheating' is also acceptable - like using a hone to get the required finish and exact diameter .... so that's what I do  ;D

I agree Admiral_dk, that looks like it would be a difficult operation... wow
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Offline Roger B

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Re: Fuel injection systems
« Reply #301 on: October 29, 2020, 08:06:33 PM »
Thank you both  :ThumbsUp:

If this design works it is not so complicated. The surface finish on the needle is not so important and the cone will be lapped in after hardening. I thought about keeping everything precise and concentric (hard) but wondered if I gave the needle a bit of freedom I could lap a sort of bell shaped curve as the seating which would be much simpler. After turning I hardened the cones and then have hopefully lapped them into the bodies with 1 micron diamond paste. There seems to be an even lapped area but the real test will be with fuel after a dip in the ultrasonic bath.
Both bodies and needle are marked so they can be kept as pairs.
Lapping is interesting as in theory the harder component receives more abrasion as the abrasive particles are imbedded in the softer material. Hopefully the stainless steel nozzle is not much softer than the needle. The earlier versions with brass and hardened silver steel may have had more problems  :headscratch:  ::)  :toilet_claw:
Best regards

Roger

Offline Brendon M

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Re: Fuel injection systems
« Reply #302 on: October 30, 2020, 11:42:03 PM »
Hello Roger, I look forward to seeing the test results :)
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Offline Roger B

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Re: Fuel injection systems
« Reply #303 on: November 02, 2020, 07:57:32 PM »
Thank you Brendon  :ThumbsUp:

The trial were quite interesting  ::) I checked the load on the injector springs which was more than my 1.2kg test weight, so with a 1.4mm bore more than 90 bar. The new nozzles tended to give a single jet but the previous version where I had ground and polished the cone gave a good spray with the characteristic noise. With a 2.5kg load on the test pump the nozzle wouldn't open. This equates to around 90 bar which matches the opening pressure being nearer 100 bar. the original nozzle used in the last engine trial:


One of the new nozzles:


Best regards

Roger

Offline Don1966

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Re: Fuel injection systems
« Reply #304 on: November 03, 2020, 02:36:19 AM »
Still with you Roger...... :ThumbsUp:    :Love:


 :cheers:
Don

Offline Roger B

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Re: Fuel injection systems
« Reply #305 on: November 03, 2020, 08:12:37 PM »
Thank you Don  :ThumbsUp:  :wine1:  I am learning a lot and will hopefully be able one day to offer a solution for small fuel injection systems  :headscratch:  :old:

As grinding the needles before lapping seems to be important I ground and polished the 15░ and 20░ needles as I did before and will lap them into the respective nozzles and make some more trials. I think that the compression pressure and the injection pressure that I am reaching is sensible, I now have to ensure good atomisation and find a new test area until I can reduce the smoke and clag (is clag just an English word or is it generally understandable?)
Best regards

Roger

Offline Roger B

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Re: Fuel injection systems
« Reply #306 on: November 10, 2020, 05:17:30 PM »
I lapped the two new nozzles with 1 micron diamond paste and gave them another swim in the ultrasonic bath. They and the previous stainless steel nozzle were set to open at more than 1.2kg load and then then checked with the hand test pump. All tests were using cooking alcohol.

Original 15░:


New 15░:


New 20░:


Only the original had the characteristic 'creak', the 20░ seemed still to give a side squirt. More to think about and learn  :thinking:

After this I set them up on the engine for an output check and to see how they sprayed at higher speed (battery drill 550 rpm).
Best regards

Roger

Offline Brendon M

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Re: Fuel injection systems
« Reply #307 on: November 11, 2020, 11:44:34 AM »
 :help:Hello Roger, for me at least, clag has always been a type/brand of glue :)

Just to clarify, the original 15 degree injector was needle based, and the new is the cone (poppet) injector?

I have forgotten, were your engines direct injection? *edit* just went and skimmed the 20cc 2 stroke diesel thread, it would appear to be direction injection. Reason I bring it up is I think the current spray pattern would suit indirect injection with swirl chamber - assuming I understood your post, of course.
« Last Edit: November 11, 2020, 11:59:49 AM by Brendon M »
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Offline Roger B

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Re: Fuel injection systems
« Reply #308 on: November 11, 2020, 05:05:06 PM »
Hi Brendon,

All the injectors in this series are poppet type. I was wanting to see if the results are reproducible. The engine is direct injection but as I understand the idea behind the prototype design it is fairly high swirl. The angled ports and coned piston should produce rotation in one plane  and as the piston reaches TDC the air in the anulus is forced into the central cylindrical combustion chamber producing swirl in the other plane.
Best regards

Roger

Offline Roger B

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Re: Fuel injection systems
« Reply #309 on: November 14, 2020, 05:31:48 PM »
I took the engine into the welding bay at work and had another play. The injection timing seems quite critical so I need to work on a better adjustment system  :headscratch: The three stainless steel nozzles all reacted much the same. I got a short burst of firing which kicked the drill out and then it stopped. As things warmed up I got the impression it was running longer, may be 5 seconds. This is one test, drill in the right hand camera in the left. I like the smoke ring at the end  :)


Best regards

Roger

Offline Roger B

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Re: Fuel injection systems
« Reply #310 on: February 21, 2021, 11:24:31 AM »
I wanted to check/improve the nozzles before I tried the diesel again. The initial results were much as before. The first 15░ stainless steel nozzle gave reasonable results with a 'creak' the other two were not so good.


I decided to try some additional lapping of the seatings as before. All three had around 1/2 hour of lapping with 1 micron diamond paste followed by a clean up in the ultrasonic bath. The results were somewhat disappointing. The first 15░ nozzle was about the same the second 15░ and the 20░ nozzles were worse  :headscratch:


I carefully checked all three nozzles to try and determine why one worked better than the others  :thinking: Eventually I found the difference  :) The spring seating recess in the body of the first  nozzle was 2.4mm diameter, in the other two it was 2.5mm. As the spring is ~1.4mm ID and ~2.4mm OD it was acting as a guide for the first unit. My thoughts about allowing the needle to float a bit and having a bell shaped seating were obviously not good  :toilet_claw:

I now need to work out how to form a guide section on the 1mm diameter section of the nozzle which will allow the fuel to pass. It may be easiest to leave the needle at 1.4mm for longer and mill/grind some slots for the fuel to flow through. Off to the drawing board.
Best regards

Roger

Offline Admiral_dk

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Re: Fuel injection systems
« Reply #311 on: February 21, 2021, 07:42:52 PM »
At least you found out why  there is a difference  :ThumbsUp:

One must admire your patience / perseverance regarding this project  :praise2:

They say that the more tribulations - the bigger the satisfaction when you succeed -> I really hope that you get reason for a big happy dance  :cheers:

Offline Don1966

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Re: Fuel injection systems
« Reply #312 on: February 21, 2021, 09:08:36 PM »
At least you found out why  there is a difference  :ThumbsUp:

One must admire your patience / perseverance regarding this project  :praise2:

They say that the more tribulations - the bigger the satisfaction when you succeed -> I really hope that you get reason for a big happy dance  :cheers:
Yep agree awesome work keep it up!

Don

Offline Roger B

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Re: Fuel injection systems
« Reply #313 on: March 06, 2021, 05:43:31 PM »
Thank you both for following with this long term project  :ThumbsUp:

I have started making a needle for the mushroom injectors with a guidance section. Most of it is as before but the 1.4mm section is extended by 4mm and there are 4 0.2 x 0.5mm slots milled in this section to allow the fuel to flow through. Photography with standard equipment starts to get difficult at these sizes  ::)
Best regards

Roger

Offline Chipmaster

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Re: Fuel injection systems
« Reply #314 on: March 06, 2021, 05:55:21 PM »
Very skilful Roger, wish I could machine small diameters like that.

Andy