Diesel / kerosene injector placement with propane starter no

[hosedup]

I've been reading a bunch about fuel introduction devices. It seems that with propane, radial flow is critical and axial flow is fast death for turbine.  But with diesel / kerosene, axial flow is just fine. Is this because of parts availability or because of high latent heat needed to vaporize the oil? Or something completely different?

I'm in the process of planning the next engine. For ease of starting, I want to start with propane but switch to oil once warmed up.  If time permits, maybe run on biodiesel / waste cooking oil (I have nearly 10 gallons of left over Turkey frying oil) 

So,  what is a good injector configuration to have both propane and oil?  One thought is to make a large bolt style propane injector with radial holes but with a store bought oil injector on the bolt face. This will take creative drilling but I have an idea.

Also, would a power steering pump be a good candidate to repurpose for a fuel pump? The one I have will easily generate over 200 psi and likely far more according to specs. 

[racket]

Yep , go co-axial , I did that with my TV84 , the gas flowed out around the fuel nozzle , once it ignited the fuel spray went through the flame for positive ignition

[hosedup]

Nov 17, 2019 15:20:33 GMT -5 racket said:

Yep , go co-axial , I did that with my TV84 , the gas flowed out around the fuel nozzle , once it ignited the fuel spray went through the flame for positive ignition

How should the primary holes line up to the oil nozzle?  Currently I have my bolt injector setup so the propane holes are lined up with the primary holes.  I have a feeling the tip of the nozzle should be right with the primary holes or behind them.

[racket]

Hi

Do you want to run on propane or only use it as a pilot light for the liquid fuel??

If only a pilot light then having the radial injection isn't as necessary as when its the only fuel used .

You want the spray nozzle spray to impact the Primary holes at the wall , so the injector tip needs to be considerably "higher" in the flametube than the wall holes

Cheers
John

[hosedup]

Plan is to start on propane and run on oil. From what I've read, its far easier to start on propane than oil. Ultimately I want to run it on diesel, kerosene or waste cooking oil.

[racket]

By "start on propane" do you mean get it up to idle on propane before then attempting to switch over onto oil ??

Or simply use the propane as a pilot light ??

[hosedup]

I'm hoping to start and idle until warm, then transition over to oil.

[racket]

Thats not going to be so easy to accommodate , you'll need to displace the propane injection further up the flametube to roughly the position of the fuel sprayer and have the propane injection holes angled to match the fuel spray so both would impact the Primary holes , as you'll only be going to idling conditions hopefully the "off design" propane injection hole orientation won't be an issue .............the propane hole sizes will need to be smaller than for full power sizing so as to keep propane pressures high and to produce strong and more "accurate??" jets of fuel , if too big, the propane might only form a central core of fuel within the flametube and not burn correctly

[hosedup]

Nov 17, 2019 22:02:26 GMT -5 racket said:

Thats not going to be so easy to accommodate , you'll need to displace the propane injection further up the flametube to roughly the position of the fuel sprayer and have the propane injection holes angled to match the fuel spray so both would impact the Primary holes , as you'll only be going to idling conditions hopefully the "off design" propane injection hole orientation won't be an issue .............the propane hole sizes will need to be smaller than for full power sizing so as to keep propane pressures high and to produce strong and more "accurate??" jets of fuel , if too big, the propane might only form a central core of fuel within the flametube and not burn correctly

Sounds like it would be best to design for propane but leave space to accommodate oil.  Considering how much simpler propane is to use, this should make the build less complex. 

I have a couple ideas for how to make a propane injector that accommodates oil.  One is a ring of tubing that is mounted forward of the oil injector.  Small holes are drilled around its diameter and positioned in line with primary holes. 

When it comes to liquid fuels, what do most people use for a pump?  I was thinking of a power steering pump because they are easily available and can make rather high pressure. 

[racket]

Nope that idea will have potential problems , don't go there .

Better to design for oil as its going to be your higher power setting fuel , also propane is a very forgiving fuel so we can get away with less than ideal fuel/air presentation which allows its injection , especially for only idling power settings, to be rudimentry .

Better to have the propane tubing ring "behind" the oil sprayer , preferably with a lot of "largish" holes for injecting the propane , you could have the same number of injection holes as Primary wall holes and inject axially past each wall holes , the larger and numerous injection holes will provide a "curtain" of propane past the wall holes which will hopefully create the right conditions for combustion .

Though you will need to be very careful about heat at the end cap of the combustor , you may need some air injection across its face .

Lotsa things to think about before making a final decision .................LOL, theres probably an easier and simpler solution stareing me in the face :-)

Power steering pumps have been used as oil/lube pumps so no reason why a small PS pump wouldn't work as a fuel pump

Cheers
John

[racket]

Hi

Maybe try something like this, shes a rough drawing , not to scale or anything ................but its quicker than trying to type a description :-)


Cheers
John

[hosedup]

Very interesting design. I was thinking of something along those lines. I tempted to build this just to see how it fires (with leaf blower, no turbo)