Model Diesel: 32mm bore, 38mm stroke, indirect injection

[The Ignoble Troll]

Thanks guys!

 

[Nerd1000]

I decided to take Roger's advice and grind the grooves in after heat treatment. Here's my setup, I just put a dremel cut-off wheel and arbor in my milling collet.

Worked pretty well. I covered my ways with rags before grinding, the abrasive dust is not good for them. My mill only does 1100 rpm at full speed which is really too slow for a grinding wheel. Still made a lot of heat, I had to squirt coolant on it between passes to avoid taking the temper out of the part!

This part lapped in much better. Interesting observation, it was actually lobed with 3 high points. I suspect the low points lined up with the chuck jaws on the lathe when I was turning it. I've got it cleaned up slightly oversized, I'm not totally happy with the surface finish in the barrel (grit was too coarse) so I think I'll finish by lapping the barrel bigger to match.

 

[peterl95124]

Having done all this, temptation took over and i put the head on and cranked the engine with a more powerful drill in low gear. There was a noticeable smell of burnt oil, and so, optimistic, I sprayed some 'start ya bastard' into the intake port and tried again... a large cloud of white smoke shot out of the exhaust as the valve opened. We've achieved compression ignition!

I used some "start ya bastard" on my Merlin V12, that was the only time it ever backfired, and given the large volume of the intake manifold, it was quite a backfire resembling a gun shot more than an engine pop, not using it any more :-( !!!

anyway, following this thread with interest as I have a Hansen A-frame Diesel in the works but have not yet attempted the fuel pump and injector...

 

[ruben]

Más progreso: ¡tengo un (más o menos) inyector que funciona!
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El patrón de pulverización podría necesitar algo de trabajo, sospecho que esto podría beneficiarse al lamer la punta de la aguja junto con la boquilla del inyector. El otro problema que tengo es que el resorte del inyector no es lo suficientemente fuerte como para hacer que la presión de "pop" del inyector alcance mi objetivo de 10 MPa. Creo que esto se puede solucionar simplemente doblando los resortes.

A continuación se muestran las partes principales del inyector, antes de algunas operaciones de fresado que necesitaban para el acabado. Como referencia, el tornillo de cabeza hueca que los acompaña es de tamaño M3. Los componentes del cuerpo del inyector son de acero inoxidable, mientras que la aguja es de acero para herramientas.

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Dónde puedo encontrar los dibujos de ese inyector

 

[ruben]

Este es tu inyector con válvula exterior, ¿verdad?View attachment 139449

Hola dónde puedo encontrar los planos de ese inyector

 

[Steamchick]

Peter, White smoke means we either elected a new pope, or unburnt fuel has been vaporised.
WELL DONE!
K2

 

[Mechanicboy]

Hola dónde puedo encontrar los planos de ese inyector

Ho hay de ese inyector por el motor de modelismo.

 

[minh-thanh]

Hola dónde puedo encontrar los planos de ese inyector

You go to a place where English is the standard, you should use English, Don't make it your own place !!!!
I got a PM from you but I'm too lazy to translate it
Imagine, many others learn the way you do, then this place will be a trash can
Note: 90% of my comments on the forum are completely using google translate .

 

[ruben]

You go to a place where English is the standard, you should use English, Don't make it your own place !!!!
I got a PM from you but I'm too lazy to translate it
Imagine, many others learn the way you do, then this place will be a trash can
Note: 90% of my comments on the forum are completely using google translate .

Ok use english

 

[ruben]

Algunas reflexiones y sugerencias sobre los motores diésel pequeños. Llegué hasta un diésel de 4 tiempos, 20 cc, 25 mm de diámetro y 40 mm de carrera, ejecutable. Funciona con bomba diésel estándar. El video es un comienzo cálido, abriendo la rejilla de combustible cuando empiezo a arrancar.



La atomización del inyector aún no es muy buena. Al menos la mitad del combustible sale sin quemar del escape. La presión de compresión ronda los 35 bar y la presión de inyección supera los 100 bar.

La culata es plana con una cámara de combustión semiesférica en el pistón. El inyector está colocado en ángulo apuntando al centro de la cámara.

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La bomba de inyección tiene un diámetro de 2 mm y una carrera de trabajo de 2 mm, el primer mm cierra el puerto de entrada. La cantidad de combustible se controla mediante una hélice de derrame, por lo que el momento del inicio de la inyección es constante. El inyector es de tipo obturador o hongo basado en el diseño GM 5.7L. He experimentado con inyectores de aguja, pero fue muy difícil conseguir un buen asiento en el extremo de un orificio largo. Con un estilo de asiento los asientos son visibles. Encuentre que Hansen y Don Comstock usan este tipo.

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Los émbolos de la bomba de combustible están hechos de calibres de pasador lapeados y endurecidos comerciales. La hélice dosificadora se rectifica con un pequeño disco de corte. El cuerpo de la bomba está hecho de acero plateado endurecido lapeado a medida usando una aguja Acro y pasta de diamante de 1 micra.

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Las agujas del inyector están torneadas en acero plateado y solo las puntas están endurecidas. Los cuerpos son de acero inoxidable. El asiento está pulido con pasta de diamante de 1 micra. He probado varios ángulos diferentes para la punta, actualmente el de 10° incluido parece funcionar. Si el ángulo es demasiado pequeño, tenderá a atascarse.

Construí una bomba de prueba para los inyectores para poder aplicar una carga conocida al émbolo con una balanza de resorte. 50 N en un émbolo de 2 mm dan una presión de apertura de alrededor de 150 bar. No lo acerques a tu piel. El patrón de pulverización todavía no es muy bueno con una mezcla de combustible bien atomizado y gotas húmedas.

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Some thoughts and suggestions on small diesels. I have got as far as a runnable 20cc, 25mm bore 40mm stroke, 4 stroke diesel. This runs on standard pump diesel. The video is a warm start, opening the fuel rack as I start to crank.



The atomisation from the injector is not very good yet. At least half the fuel is ejected unburnt from the exhaust. Compression pressure is around 35 bar and the injection pressure is over 100 bar.

The cylinder head is flat with a hemispherical combustion chamber in the piston. The injector is set at an angle aiming at the centre of the chamber.

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The injection pump is 2mm bore and 2mm working stroke, the first 1mm closes the inlet port. The fuel quantity is controlled via a spill helix so the timing of the start of injection is constant. The injector is a poppet or mushroom type based on the GM 5.7L design. I have experimented with needle type injectors but getting a good seating down the end of a long bore was very difficult. With a poppet style the seating is visible. Find Hansen and Don Comstock both use this type.

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The fuel pump plungers are made from commercial hardened and lapped pin gauges. The metering helix is ground with a small cutting disc. The pump body is made from hardened silver steel lapped to size using an Acro needle lap and 1 micron diamond paste.

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The injector needles are turned from silver steel and just the tips are hardened. The bodies are stainless steel. The seating is lapped with 1 micron diamond paste. I have tried several different angles for the tip, currently 10° included seems to work. If the angle is too shallow it will tend to jam.

I built a test pump for the injectors so I can apply a known load to the plunger with a spring balance. 50N on a 2mm plunger gives around 150 bar opening pressure. Don’t get it anywhere near your skin. The spray pattern is still not very good with a mixture of well atomized fuel and wet drops.

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Hola donde puedo encontrar los planos del piston

 

[ruben]

Hola donde puedo encontrar los planos del piston

lo siento
Hello, where can I find the piston plans?

 

[ruben]

lo siento
Hola donde puedo encontrar los planos de pistones?

 

[Roger B]

lo siento
Hello, where can I find the piston plans?

Here is the plan of the piston and combustion chamber. Can you read .DWG files?

 

[ruben]

hello thanks

 

[Nerd1000]

Roger,

With your design I wonder how much fuel gets sprayed onto the piston surface. Have you had the head off and inspected since getting a good amount of run time on the engine? Curious if there is evidence of this like a fuel washed patch in the bowl.

 

[Roger B]

Roger,

With your design I wonder how much fuel gets sprayed onto the piston surface. Have you had the head off and inspected since getting a good amount of run time on the engine? Curious if there is evidence of this like a fuel washed patch in the bowl.

This is one of the good questions, how far does the fuel spray travel in air at 30+ Bar as against in open air, will it reach the piston? I haven’t had the head off for a while but last time there was no obvious washing of the piston bowl, just signs of contact between the piston and the valves (which is why I took the head off to insert a 0.5mm shim gasket).

 

[ruben]

Aquí está el plano del pistón y la cámara de combustión. ¿Puedes leer archivos .DWG?

I will make a test piston and to make the piston what I will do is I will put the piston in the lathe and with a ball end mill I will make the shape of the combustion chamber of the piston

 

[ruben]

This is one of the good questions, how far does the fuel spray travel in air at 30+ Bar as against in open air, will it reach the piston? I haven’t had the head off for a while but last time there was no obvious washing of the piston bowl, just signs of contact between the piston and the valves (which is why I took the head off to insert a 0.5mm shim gasket).

Looks very good

 

[Nerd1000]

This is one of the good questions, how far does the fuel spray travel in air at 30+ Bar as against in open air, will it reach the piston? I haven’t had the head off for a while but last time there was no obvious washing of the piston bowl, just signs of contact between the piston and the valves (which is why I took the head off to insert a 0.5mm shim gasket).

Heh, would have been nice to have more direct evidence on that front. I've seen some papers where they painted the piston with something fuel soluble and after running a few cycles inspect to see where the paint washed off. Might be one way to attack that question.

 

[ruben]

Aquí está el plano del pistón y la cámara de combustión. ¿Puedes leer archivos .DWG?

Hola