Author Topic: Fuel injection systems  (Read 73912 times)

Offline Minh Thanh

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Re: Fuel injection systems
« Reply #330 on: August 13, 2021, 03:24:45 PM »
Hi Roger !
Thanks !
 I will try with this injector
Here is my injector design, if you are interested !

Offline Roger B

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Re: Fuel injection systems
« Reply #331 on: August 15, 2021, 04:48:01 PM »
Thank you Thanh  :)

What CAD package do you use? All my drawings are .DWG (AutoCad, DraftSight) which I am happy to share if you can read them.

With all my injection components I have tried to minimise the number of joints and possible places where air could be trapped. The needle type injectors will always leak a little past the needle shaft which is not good with petrol (gasoline) injection. I moved to the mushroom (poppet, pintle) type to avoid this problem. Don Comstock who has made some working diesels (W7CJ on YouTube and Flickr seems to be his son) appears to have used cut down Oldsmobile poppet injectors.
Best regards

Roger

Offline Minh Thanh

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Re: Fuel injection systems
« Reply #332 on: August 16, 2021, 10:25:17 AM »
Hello Roger !
I have autocad, but usually use inventor
About adding 1 or 2 joints: I think - the way I think, of course - it doesn't matter, and it doesn't hold any extra air.

"The needle type injectors will always leak a little past the needle shaft which is not good with petrol (gasoline) injection."

You are correct, even though I try to do it as best I can, always leak a little past the needle shaft
I will design the injector like yours, I will try both ways

Thanks !

Offline Roger B

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Re: Fuel injection systems
« Reply #333 on: August 19, 2021, 07:09:40 PM »
Full size diesels with needle injectors always have piping to feed the fuel that leaks past back to the tank.

I made a new body for the 10░ injector and cleaned it up in the ultrasonic bath. when assembled on the test rig it made a very satisfactory 'creak' and gave a tighter patten that the 15░ nozzle from the last trial. To open the nozzle required more than 4kg on the 2mm plunger so well over 100 Bar.

10░


15░ from the last trial

Best regards

Roger

Offline Admiral_dk

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Re: Fuel injection systems
« Reply #334 on: August 19, 2021, 11:05:45 PM »
Sound good - but it's very hard to tell how fine the 'atomizing' is .... and as that has a very direct influence on the end result .... I don't think that you (and the rest of us) will know before you have it running in one of your engines  :cheers:

I will admit that there are more factors in the engine as you already has discovered.

Offline steamer

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Re: Fuel injection systems
« Reply #335 on: August 20, 2021, 12:42:08 AM »
Full size diesels with needle injectors always have piping to feed the fuel that leaks past back to the tank.

I made a new body for the 10░ injector and cleaned it up in the ultrasonic bath. when assembled on the test rig it made a very satisfactory 'creak' and gave a tighter patten that the 15░ nozzle from the last trial. To open the nozzle required more than 4kg on the 2mm plunger so well over 100 Bar.

10░


15░ from the last trial


That's amazing Roger!    I do hope you could do a show and tell on how you  make those!....Tolerances must be tight!....

Dave


PS>...I'll need 13 and the pump......1/4 scale.....
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline bent

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Re: Fuel injection systems
« Reply #336 on: August 20, 2021, 06:16:21 PM »
I am always in a little bit of awe as I read your reports, Roger.  You are one persistent and methodical guy!

Offline Minh Thanh

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Re: Fuel injection systems
« Reply #337 on: August 21, 2021, 03:11:27 AM »
Hi Roger !
I'm making an injector similar to yours
I have a question : With the spring so small , can it hold the needle to maintain high pressure in the oil pipe ?
    How to adjust the injector to only inject at a certain pressure range, for example at least 50 bar?

Offline Roger B

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Re: Fuel injection systems
« Reply #338 on: August 21, 2021, 12:44:35 PM »
Thank you all  :) I'm still learning but will certainly present a summary when I think I have a realistic solution.

Directly measuring pressures with these small volumes is very difficult so I try to calculate some values. When I assemble a nozzle I adjust the spring load so it just opens with a 1.2kg weight rested on it (nothing very special about 1.2kg, I just happened to have a bar end that weighed that to hand). As the bore of the nozzle is 1.4mm this calculates to around 80 bar opening.

My test pump has a linkage so I can apply force to the plunger with a spring balance. 2.5kg and a 2mm plunger also calculates to around 80 bar. In my last trial with the 10░ nozzle I required 4 kg to get the spray in the video which is around 130 bar.
Best regards

Roger

Offline Minh Thanh

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Re: Fuel injection systems
« Reply #339 on: August 21, 2021, 01:04:39 PM »
 Roger !
Thanks for the explanation and pictures !  :ThumbsUp:

Offline Roger B

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Re: Fuel injection systems
« Reply #340 on: August 21, 2021, 07:16:36 PM »
No Problem, I am happy that you are trying to do this as well  :)  :)  :)

Best regards

Roger

Offline Minh Thanh

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Re: Fuel injection systems
« Reply #341 on: August 26, 2021, 10:12:42 AM »
Hi Roger !
A copy of your injector   ;D

Offline cnr6400

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Re: Fuel injection systems
« Reply #342 on: August 27, 2021, 12:00:41 AM »
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:

Offline Roger B

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Re: Fuel injection systems
« Reply #343 on: August 27, 2021, 07:16:41 PM »
Looks good  :ThumbsUp:  :ThumbsUp: Have you tried it yet?
Best regards

Roger

Offline Minh Thanh

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Re: Fuel injection systems
« Reply #344 on: August 28, 2021, 05:03:30 AM »
Cnr6400 , Roger B !
Thanks !

I tested it with compressed air, it's completely sealed,
Due to the epidemic situation and travel restrictions ... I am not able to buy small tubes and pressure gauges to adjust.
I really hate it but I can't do anything else