Hi,

I am currently trying to start some research on temperature to ignition of leaf samples. The process requires me to place samples into a muffle furnace for a period of time raising the temperature to around 400C. The problem I am having is that I need some sort of spark to actually light the leaves otherwise they just wither away.

A previous study was done (Ignitability of Leaves of Australian Plants, Gill, 1996) where they used a Spark Gun Circuit in the muffle furnace in order to achieve ignition. There is a diagram of this apparatus but I literally have no experience in this sort of field. I would need the apparatus to give off a spark every 1 second and max 5 seconds if the latter was unachievable.

I have been searching for help on my campus but I am of no priority to the relevant people to design something like this. I hope I can get some insight on how obtain or create this circuit.

Thanks

 

model engines use ignition modules to fire spark plugs. this sounds like the perfect place for such a device.
Google for small engine ignition modules to find hundreds of options

 

How about a gas range/stove igniter module? You would still need to make electrodes, but the module is made for doing the sparking and is self contained. This is just one of the many online sellers - https://www.bellparts.com/catalog/range_oven_spark_modules

 

Purchase a small neon sign transformer, that would make a very simple ignition system.

 

Purchase a small neon sign transformer, that would make a very simple ignition system.

If I were to use one of these transformers would I simply plug it in with the end wiring stripped and just let it spark? It seems like that could be a bit dangerous given the high voltage. Or would it be fine as long as I didn't touch the exposed wiring while it was plugged in and concentrated in confined area (for the most part)?

 

model engines use ignition modules to fire spark plugs. this sounds like the perfect place for such a device.
Google for small engine ignition modules to find hundreds of options

I looked into the small engine ignition modules and my only concern is that I would need to figure out how to power the device since it does not just have a plug in. This may be easy but as I said in my original post I have virtually no experience with this sort of thing.

 

<snip> I would need to figure out how to power the device since it does not just have a plug in.

Use a 4 cell NiMH battery or any other convenient battery. Relatively small batteries, say 2000 mAh, will run an engine at 8000 rpm for several 15 minute flights. That is almost 500,000 ignitions on a single charge, and of course, you can easily recharge it or buy non-rechargeable batteries and just replace them. That is a lot of leaves you can burn.

John

 

Use a 4 cell NiMH battery or any other convenient battery. Relatively small batteries, say 2000 mAh, will run an engine at 8000 rpm for several 15 minute flights. That is almost 500,000 ignitions on a single charge, and of course, you can easily recharge it or buy non-rechargeable batteries and just replace them. That is a lot of leaves you can burn.

John

Okay so say I was to get the following module: http://www.ebay.com/itm/like/281403987055?lpid=82&chn=ps How exactly would that look hooking it up to a battery? Just make sure the connections are on both the positive and negaative ends of the battery, say with electric tape?

 

That is not for model airplanes. Look up the datasheet for it.

A small spark is very high temperature, but may not have much heat. I suspected that is what you wanted. That is, almost a static discharge. If that is not the case, please explain how you will separate the effects of the heating you are doing, and the effects of a high powered spark that might,by itself, ignite the leaves?

John

 

If you wish to keep it simple, you could obtain an automotive ignition coil and drive it with a basic CD driver... If you indeed wish a lower-energy (i.e. 'cooler') spark you could go super-simple and drive the coil with a relay.

Best regards
HP

 

I cant think of a way I would separate them considering I need the constant heat source (muffle furnace) and the spark

That is not for model airplanes. Look up the datasheet for it.

A small spark is very high temperature, but may not have much heat. I suspected that is what you wanted. That is, almost a static discharge. If that is not the case, please explain how you will separate the effects of the heating you are doing, and the effects of a high powered spark that might,by itself, ignite the leaves?

John

I cant think of a way I would separate them considering I need the constant heat source (muffle furnace) and the spark to both be present in order to have an accurate measure of the temperature that my sample would ignite at.

Even if the spark added/changed the temperature I would be able to account for it because I will have type-k thermocouples recording the temperature of the sample every second.

 

I need the constant heat source (muffle furnace) and the spark to both be present in order to have an accurate measure of the temperature that my sample would ignite at

So it seems your aim is determination of the (lower) 'flash point' (or, flash range, if you will) of thermolysis products evolved from organic matter (CIP leaves) --- Now I'm curious, what is your use for such data? Wildfire abatement/prevention perhaps?

With sincere curiosity
HP

 

Yeah, I question the value of such data. I admit ignorance and I haven't read the papers, but how could these data possibly be useful? Leaves burn, we know that. They'll dry and wither at lower temperatures and, like paper, require a higher temperature to ignite.

If I wanted to know the properties of the off-gas, I think I'd capture and study it. The ignitability of those volatiles is going to depend on concentration (and a lot of other factors), and I don't see how you could control any of that in an open furnace.

 

I cant think of a way I would separate them considering I need the constant heat source (muffle furnace) and the spark


I cant think of a way I would separate them considering I need the constant heat source (muffle furnace) and the spark to both be present in order to have an accurate measure of the temperature that my sample would ignite at.

Even if the spark added/changed the temperature I would be able to account for it because I will have type-k thermocouples recording the temperature of the sample every second.

Very confusing. Either you can adjust for the effect of added heat or you cannot. Please explain how the thermocouples will help?

Your experiment reminds me of an experiment a friend of mine (initials C.E., if you are readiig this) did in school. He knew that tobacco burned at a lower temperature than the ignition temperature of diethyl ether. So, he would take some ether-soaked towels in a trash can and toss a lit cigarette into it. It usually worked, and the cigarette was extinguished by the cool ether. One day it didn't. The cigarette hit something on the way in and made a spark. The resulting conflagration was a sight to see.

He never tried that experiment again, even though, we all knew that in theory, it worked.

Bottom line, how are you going to separate the effects of the heat from the spark from the ignition temperature you assume the leaves are at? That is why I suggested a very weak spark, if that is what you decide to use. Have you considered something more controllable, such as a glow plug?

John

 

Very confusing. Either you can adjust for the effect of added heat or you cannot. Please explain how the thermocouples will help?

Your experiment reminds me of an experiment a friend of mine (initials C.E., if you are readiig this) did in school. He knew that tobacco burned at a lower temperature than the ignition temperature of diethyl ether. So, he would take some ether-soaked towels in a trash can and toss a lit cigarette into it. It usually worked, and the cigarette was extinguished by the cool ether. One day it didn't. The cigarette hit something on the way in and made a spark. The resulting conflagration was a sight to see.

He never tried that experiment again, even though, we all knew that in theory, it worked.

Bottom line, how are you going to separate the effects of the heat from the spark from the ignition temperature you assume the leaves are at? That is why I suggested a very weak spark, if that is what you decide to use. Have you considered something more controllable, such as a glow plug?

John

Okay. So I wouldn't adjust for the added heat because it would be accounted for in the overall recorded temperature (by the thermocouples). But, I would prefer a weaker spark and no I havent considered a glow plug.

 

Yeah, I question the value of such data. I admit ignorance and I haven't read the papers, but how could these data possibly be useful? Leaves burn, we know that. They'll dry and wither at lower temperatures and, like paper, require a higher temperature to ignite.

If I wanted to know the properties of the off-gas, I think I'd capture and study it. The ignitability of those volatiles is going to depend on concentration (and a lot of other factors), and I don't see how you could control any of that in an open furnace.

It has value in knowing what temperatures will ignite certain species of trees. The temperatures have been shown to vary quite widely in previous studies, many of them done in Australia. The purpose however would be to use the data that I capture for an overarching study and categorizing overall flammability of different species. There are studies that have been done in the Southeast that categorize different species into different flammability classes taking into account many factors.

 

Interesting, and thanks for the explanation. One thing I would hypothesize is that you could look at the volatiles produced per acre or per pound of tree. In other words, cook it at 400° or whatever and weigh what's left. The cellulose and lignins that make up wood will burn somewhat similarly, I imagine, but the vapors that come off as the wood cooks would vary quite a lot with species, age, moisture and so on. Just a thought.

 

Interesting, and thanks for the explanation. One thing I would hypothesize is that you could look at the volatiles produced per acre or per pound of tree. In other words, cook it at 400° or whatever and weigh what's left. The cellulose and lignins that make up wood will burn somewhat similarly, I imagine, but the vapors that come off as the wood cooks would vary quite a lot with species, age, moisture and so on. Just a thought.

And its a good thought. So weight will definitely be taken before and after as well as six other measurements to really figure what measurement impacts the ignitability the most (perimeter, thickness, width, etc...) You are also right with saying that vapors that come off would vary with the species, but one thing I think I left out in earlier comments was that this initial study will just be looking at different oak species throughout California. There are different chemical make-ups of course, but I don't believe anything to drastic. Definitely something I will have to look into more.