Please put your "I am new and need help" question here.

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kenshin
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Re: Start a valveless pulsejet with electric ducted fan?

Post by kenshin » Sun Jan 03, 2010 6:46 am

ace_fedde wrote:
kenshin wrote:Could electric ducted fan replace leaf blower to start a valveless pulsejet (mini thermojet)?
I don't have propane tank or leaf blower.
Use butane lighter refill bottle + rosscojector, the engine failed to start
Well, a leaf blower is in fact also a ducted fan... I think the problem is in the lighter refill bottle, not enough gas flow.
Why don't you post some pictures that show the sizes of your equipment and the way it is installed?
Fedde
btw: please delete the original thread

Here are the equipments, one rosscojector blow into one of the two intakes
the tube is short with low friction resistance
IMG1653A.jpg
Equipment
IMG1654A.jpg
Rosscojector
IMG1656A.jpg
Assembly
Is butane bottle capable of start a mini thermojet?
If not, next step maybe abandon butane and turn to liquid fuel + blow air, a electric ducted fan for model aircraft?

Experiment result
Light the injector or the tailpipe, reduce the gasflow, the flame retreats into the combustion chamber
The rosscojector noozle slit is adjusted
small slit = no enough fuel, engine rumbling in blow torch mode but does not start
larger slit = low injection gas velocity? no enough air entrained, runs rich and flame out
Room temprature is around 5 degree C, the bottle cools down quickly and lose pressure
warm the bottle with water, the gas flow become hard to control and flames out

metiz
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Re: Please put your "I am new and need help" question here.

Post by metiz » Sun Jan 03, 2010 12:46 pm

you could try flipping the bottle upside down to give it liquid but I don't think it'll work
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kenshin
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Re: Please put your "I am new and need help" question here.

Post by kenshin » Sun Jan 03, 2010 1:59 pm

already tried, rich fuel flame out
now looking for suitable air source to start a "Chinese CS" type liquid fuel system
maybe a bike tire hand pump.
metiz wrote:you could try flipping the bottle upside down to give it liquid but I don't think it'll work

ace_fedde
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Re: Please put your "I am new and need help" question here.

Post by ace_fedde » Sun Jan 03, 2010 4:01 pm

I am not a very experience trouble shooter, or lets say that I don't have experience with trouble shooting, but let's try the standard list:

-Is it a proven to work PJ design? Designing is pretty complicated.
-Are the intakes flanged?
-What is the position of your fuel injector?
If you answer these, I'll have to let somebody else help you further :lol:

How about trying two injectors? And how about first trying with a BBQ stove gas bottle (without the regulator!!)?

Fedde
Your scepticism is fuel for my brain.

BenJet
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Re: Please put your "I am new and need help" question here.

Post by BenJet » Thu Feb 11, 2010 12:31 am

I have two questions, to create a very powerful valveless engine to use as propulsion engine for vehicles. And one more terminology question.

1. Witch valveless engine generates the most thrust? Please link a powerful design if available.
2. Witch fuel generates the most thrust?

3. What we understand as thrust is it the same as Mass Flow Rate?
http://www.grc.nasa.gov/WWW/K-12/airplane/mflow.html

Maybe these questions have been answered thousand times, but I'm not able to find the answer. The most important one for me is the first. Before spending any money I would like to know what engine type I'm going to build. And if there are any plans I would appreciate it. I'm really looking for something that blows hard, harder than the V1.

Thanks
Ben
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metiz
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Re: Please put your "I am new and need help" question here.

Post by metiz » Thu Feb 11, 2010 11:07 am

"Harder then the v1"

....That engine produced like 700 pounds of thrust. Not only are valveless engines that size not just pulse-jet dangerous, they are massive health hazzards. I have a 100 something pound engine here and running that thing will leave me with an headace, gasping for air. A realy big engine like that could POTENTIALLY kill you. Also, what kind of vehicle are you planning to power with 700 pounds of thrust - a freaking schoolbus?

What is everyone telling you in your previous topic: start small, start slow, use an existing design, learn the ins and outs etc. Building a V1 like pulse-jet can be described by exactly non of those points.

Seriously, start with Beck-technologies 3/4 pound thermojet or similar and run that. Than you'll know why everybody keeps telling you to start slow.

Oh and that equasion I think applies to steady combustion. Pulse-jets are unsteady.
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Re: Please put your "I am new and need help" question here.

Post by Johansson » Thu Feb 11, 2010 11:40 am

kenshin wrote:already tried, rich fuel flame out
now looking for suitable air source to start a "Chinese CS" type liquid fuel system
maybe a bike tire hand pump.
metiz wrote:you could try flipping the bottle upside down to give it liquid but I don't think it'll work
Try MAPP gas, a small engine like that might not work on butane/propane.

BenJet
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Re: Please put your "I am new and need help" question here.

Post by BenJet » Thu Feb 11, 2010 1:20 pm

metiz wrote:"Harder then the v1"

....That engine produced like 700 pounds of thrust. Not only are valveless engines that size not just pulse-jet dangerous, they are massive health hazzards. I have a 100 something pound engine here and running that thing will leave me with an headace, gasping for air. A realy big engine like that could POTENTIALLY kill you. Also, what kind of vehicle are you planning to power with 700 pounds of thrust - a freaking schoolbus?

What is everyone telling you in your previous topic: start small, start slow, use an existing design, learn the ins and outs etc. Building a V1 like pulse-jet can be described by exactly non of those points.

Seriously, start with Beck-technologies 3/4 pound thermojet or similar and run that. Than you'll know why everybody keeps telling you to start slow.

Oh and that equasion I think applies to steady combustion. Pulse-jets are unsteady.
Thank you very much for your answer,
I am not planning to actually build such a powerfull PulseJet, I said that because I want to know wich design to use for max thrust.
Could you please tell me which valveless pulsejet type I should use for massive thrust? Chinese/Lockwood/Ecrevisse? Witch one gives the best results?
Before I start investigating, I would like to know.

Thanks
Ben
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nickwilson
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Gas injectors and pressure

Post by nickwilson » Mon Mar 01, 2010 5:06 am

I am having problems getting my small Pulse Jet running on gas. It runs fine on propane. I have a pic of it on the plans on the 'Looking for plans, Look here' forum. I've tried pinching the end off and drilling little holes in the tube all around it and just pinching the tip like I do for propane. I have a fuel pump for a car, it only pushes 5-9 psi. I think that might be the problem, but don't know. Also not sure about the injector tips. I would really like some help. Thanks. Nick Wilson

paul fellows
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Re: Please put your "I am new and need help" question here.

Post by paul fellows » Sat Mar 13, 2010 4:31 pm

take any type of pulsjet that as not been optimised,
what has to be done to optimise it for heat production?
what has to be done to optimise it for exaust valosity?
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paul fellows
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Re: Please put your "I am new and need help" question here.

Post by paul fellows » Sat Mar 13, 2010 4:54 pm

wildbillkelso wrote:Hi all.

I would like to build a small thermojet to power a small and light remote control hydroplane, The boat weighs approximately 250g. My idea is to build a thermojet and use a modified blow torch to fuel it. I have modified a servo for 4x 360 degree turns to enable me to open the valve for throttle control. Is a blow torch gas canister that is commonly used for plumbing suitable, or should I consider some other form of fuel?
Any thoughts on this, or motor design would be greatly appreciated. Or if you would point me in the right direction.

Many thanks and best regards.

Tim
not what you are looking for but!

one of the ways that as been sujested to get more thrust out of a PJ is to inject steem into the exaust stream!
what if someone where to direct the exaust of a PJ across the water between the hulls of a cat?
two test tickles

paul fellows
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Re: Please put your "I am new and need help" question here.

Post by paul fellows » Sun Mar 14, 2010 2:09 pm

is there any truth to this
do valveless pulsejets have to be noisey?
It is an unfortunate fact that the geometries that produce good Kadenacy usually also produce strong acoustic resonances but dose that mean that those resonances are necessary or even desirable???
that is a genuine question!
I believe the answer is NO, but I could be wrong?
As an aside
back in the days of the incandescent filament light bulb, bulbs produced lots more heat than they did light. This was conciderd normal and even necessary to there operation! Now we know better!
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metiz
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Re: Please put your "I am new and need help" question here.

Post by metiz » Sun Mar 14, 2010 3:17 pm

Heat isn't a driving force in lightbulbs, it's an unfortunate side-effect. Acoustics ARE the driving force in pulse-jet engines. some measurements can be taken to decrease noise but this always decreses performance or fuel consumption. And even then they are still very loud
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paul fellows
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Re: Please put your "I am new and need help" question here.

Post by paul fellows » Mon Mar 15, 2010 11:12 pm

metiz wrote:Heat isn't a driving force in lightbulbs, it's an unfortunate side-effect. Acoustics ARE the driving force in pulse-jet engines. some measurements can be taken to decrease noise but this always decreses performance or fuel consumption. And even then they are still very loud
you say that acoustics are the driving force in pulse jets. but with no proof. :?:

i say that acoustics are not the driving force in pulse jets. but with no proof. but with the following weak (very weak :oops: ) evidance.
a flat topped 'jam jar' as discribed elsewere on this site will continue to run on just kadenacy without any posibility of being acousticaly driven. and if you put a small thrust augmentor above the hole there will be a small amount of thrust. :shock:
i can not imagin a system with a megaphone in a pipe, even if driven to perfect resonance, and made to make a noise louder then a pulse jet. ever acutaly producing thrust.

i said the case is weak, please respond with proof.
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metiz
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Re: Please put your "I am new and need help" question here.

Post by metiz » Tue Mar 16, 2010 12:09 am

I don't need to prove anything. But if you insist: hows 104 years of history. If acoustics were not the driving force don't you think that, in 104 years some-one would have noticed? There's also some very complex maths that can acurately predict pulse-jets to amazing precicion. Do you think this is just a weird coincidence?

Go check out the "Essential reading" topic to find some good information.

If you're still not convinced, set up your own experiments, document them and prove 104 years of history wrong
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