Nitro engine injection and ignition parameters

[Rocketgeek]

Hi everyone!!

I was looking for the injection/ignition parameters of a nitro engine that burns a 90/10 mixture of nitromethane and methanol

-Which kind of injectors are used and what's the pressure jump across them?

- What is the pressure in the chamber at the moment of combustion?

-Spark plug or glow plug?

-What is the energy and/or power absorbed by the spark/glow plug and how long does it stay on?

-Bonus question: how much spark energy does a 90/10 NM/methanol mixture required to ignite?

Thanks to everyone who will contribute

 

[WVNed]

A curious post. Have you ever seen a typical model engine?

2 cycle, glow ignition, carburetor, no valves just intake and exhaust ports.

 

[Rocketgeek]

A curious post. Have you ever seen a typical model engine?

2 cycle, glow ignition, carburetor, no valves just intake and exhaust ports.

Actually no, I haven't. I am trying to design a nitromethane fueled rocket
So I was looking for some ranges for operational parameters to orient myself
Since nitromethane is widely used in RC models, I was thinking maybe you guys could provide some reasonable numbers

 

[WVNed]

Actually no, I haven't. I am trying to design a nitromethane fueled rocket
So I was looking for some ranges for operational parameters to orient myself
Since nitromethane is widely used in RC models, I was thinking maybe you guys could provide some reasonable numbers

We dont need to know any of that stuff to run our little cars and it's just a hobby. About the trickiest we get is using temperature to make sure we aren't running the engine too lean so we don't damage the engines.


I think you would have more success looking in drag racing real cars that run nitromethane and actually have the parts you mentioned and have to worry about the combustion properties so they dont explode but make maximum power.

 

[Rocketgeek]

The thing is that our engine is very small.
Combustion chamber is approximately 30 mm in diameter and 60 mm long
Therefore I was counting on your knowledge on miniaturized engines

 

[WVNed]

The combustion parameters for a fuel are based on air fuel ratios, compression and ignition temperature. None of those are dependent on the volume of fuel burned or the size of the engine.

There are probably tables you can look up based on fuel composition but you are asking about real car technology and not model technology
Our engines can be run on straight methanol or methanol with various percentages of nitromethane. That is how uncritical the combustion parameters are and why we don't bother to learn them.

Perhaps someone smarter than me will answer your questions.

 

[tntpoof]

I dont think the nitro engine will give you the thrust # you are going to need. read this post early today and was like wow This is either a science project or rocket man..

 

[Greywolf74]

The thing is that our engine is very small.
Combustion chamber is approximately 30 mm in diameter and 60 mm long
Therefore I was counting on your knowledge on miniaturized engines

I dont believe any one in this forum is going to know the answers to this. you're going to need an engineer, race car mechanic, or a chemist to get those answers.

 

[WVNed]

That kind of stuff is right on the net. I have looked at it before. As I suspected they had no idea what the engines we use even look like.
a 1 second search
COMBUSTION CHARACTERISTICS AND FLAME STRUCTURE OF NITROMETHANE LIQUID MONOPROPELLANT

https://etda.libraries.psu.edu/files/final_submissions/2640

Typical A/F ratio for nitromethane is 1.7:1 and nitromethane has an energy content of 5,000 BTU/lb.Using our Focus engine from above with a 1.7:1 ratio our motor would use 13.04lbs of fuel. Multiply that by the 5,000btu’s per lb of nitro and our motor would be making 65,200btu’s at 7000rpms.

 

[WVNed]

The thing is that our engine is very small.
Combustion chamber is approximately 30 mm in diameter and 60 mm long

That would give a volume of 42 cc. One cylinder on a new 5.7 hemi is 65cc.
I don't consider that small.

Meh, I thought maybe there would be a person into drag racing on here. I read a lot about it but never did it.

 

[Greywolf74]

I'm in to drag racing but only as the driver lol

42CC is very big compared to our little toys that are 4.5CC for a big .28. I mean some of the big plane engines might get up to 2 or 3 times that but thats still a fraction of the size.