Additions to rules:
Motor results not final until all data is in.
Honor system reporting, but you may have to come prove your results at a meet!
Here's the beginnings of a results sheet:
Interested ?
Moderator: Mike Everman
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Mike Everman
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milisavljevic
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Re: Interested ?
Graham, Mike and others with a keen interest in the mathematical workings of pulsejets... Some news:
As I discussed with Mike yesterday, the maximum amount of thrust that can be extracted from a given
combustor volume is a "bound" problem (mathematically speaking). This is to say that we can calculate
an EXACT value for thrust-per-unit-volume for a known set of boundary conditions (eg., self-sustaining
static operation, sea level altitude, propane fuel, etc.). These values represent a ceiling INDEPENDENT
of duct geometry -- in a manner completely analogous to the relationship between combustor diameter
and maximum static thrust as first reported by JS Cronje, ca. 1979. This is a new development for me.
The required calculations are not straightforward, and I need to write a program to generate solutions,
but it can be done. At this moment, I'm leaning towards graphical solutions (method of characteristics,
anyone?). I believe(?) I can isolate values (+/- 10%) without too much effort (but no more Haiku...
).
What may not be a bound problem, and certainly far harder to calculate in any event, is the maximum
thrust that can be extracted from a given pulsejet volume (total volume). This suggests that adopting
total volume as the restriction (as opposed to using combustor volume) is the more interesting choice.
If Mike has time to chime in here, he can brag (and justifiably so) about the specific thrust of his own
"pocket jet": 15.6 N (3.5 lbf) thrust (~ sea level static) from 0.494 liters (30.1 cu. in.) = 31.6 N / liter!
(to put this into perspective, the (Laird) Chinese rates only about 17.0 N / liter; ~20 N from 1.18 liter)
Sometimes, apparently, less really is more!
Cheers,
M.
As I discussed with Mike yesterday, the maximum amount of thrust that can be extracted from a given
combustor volume is a "bound" problem (mathematically speaking). This is to say that we can calculate
an EXACT value for thrust-per-unit-volume for a known set of boundary conditions (eg., self-sustaining
static operation, sea level altitude, propane fuel, etc.). These values represent a ceiling INDEPENDENT
of duct geometry -- in a manner completely analogous to the relationship between combustor diameter
and maximum static thrust as first reported by JS Cronje, ca. 1979. This is a new development for me.
The required calculations are not straightforward, and I need to write a program to generate solutions,
but it can be done. At this moment, I'm leaning towards graphical solutions (method of characteristics,
anyone?). I believe(?) I can isolate values (+/- 10%) without too much effort (but no more Haiku...
).What may not be a bound problem, and certainly far harder to calculate in any event, is the maximum
thrust that can be extracted from a given pulsejet volume (total volume). This suggests that adopting
total volume as the restriction (as opposed to using combustor volume) is the more interesting choice.
If Mike has time to chime in here, he can brag (and justifiably so) about the specific thrust of his own
"pocket jet": 15.6 N (3.5 lbf) thrust (~ sea level static) from 0.494 liters (30.1 cu. in.) = 31.6 N / liter!
(to put this into perspective, the (Laird) Chinese rates only about 17.0 N / liter; ~20 N from 1.18 liter)
Sometimes, apparently, less really is more!
Cheers,
M.
no safe haven for merchant scum
for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT
avast!
Cap'n M.
for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT
avast!
Cap'n M.
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Graham C. Williams
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Re: Interested ?
Mikes "Pocket Jet" is a very special motor. It's a solution to the unsteady momentum equation that seems to be better at optimising the change in momentum content (internal momentum) of the pulsejet with time. If you like, 'more of the thrust is going in the right direction at any given moment.'
Graham.
Graham.
Dark days nurture new
light. Productions begin.
Now open your eyes.
light. Productions begin.
Now open your eyes.
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Graham C. Williams
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Re: Interested ?
The Twin induction Lady Anne (Rev 6 Type 07 derivative. I think?) Built by James D. isn't too bad either, at a little over 22 N/L (21.6 N with a volume of about 0.97L)
This motor could probably get nearer to 24N/L by making it a little more unsteady!
Graham.
This motor could probably get nearer to 24N/L by making it a little more unsteady!
Graham.
Dark days nurture new
light. Productions begin.
Now open your eyes.
light. Productions begin.
Now open your eyes.
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milisavljevic
- Posts: 855
- Joined: Sat Oct 04, 2003 9:36 am
- Antipspambot question: 125
Re: Interested ?
Hello Graham,
Or did you mean something different by "unsteady"?
To correct any possible miscomprehensions from an earlier post: I did not mean to suggest that there's a singular
ceiling value for specific thrust (ie., thrust per unit volume); this is physically impossible. Ceiling values will vary
with volume, meaning we will find a curve^. At the moment, I expect this curve to reflect an inverse exponential.
^ In English: "All other things being equal, smaller pulsejets can achieve higher thrust densities than larger ones."
While Mike's "pocket jet" boasts v. high thrust density, it does so at the expense of fuel efficiency. We may then
imagine that the ratio of volume specific thrust density to specific fuel consumption represents a possible metric
of interest to those working to optimise the size and efficiency of practical* pulsejets. Just not for this challenge.
* 'Practical' in the sense of fitness for purpose, eg., propulsion for civil transport aircraft, or high-endurance UAV.
Haiku later..?
Cheers,
M.
Come to think of it, I now expect that volume specific thrust density will peak at some minimum volume and then
decrease as volume tends to zero; this means that a plot may resemble a flat arc, with its peak shifted to the left.
Ever try feeding her shots of Bourbon/Vodka/Whiskey/Tequila? Chase it all down with black coffee: Wobbly Anne!Graham C. Williams wrote: This motor could probably get nearer to 24N/L by making it a little more unsteady!
Or did you mean something different by "unsteady"?
To correct any possible miscomprehensions from an earlier post: I did not mean to suggest that there's a singular
ceiling value for specific thrust (ie., thrust per unit volume); this is physically impossible. Ceiling values will vary
with volume, meaning we will find a curve^. At the moment, I expect this curve to reflect an inverse exponential.
^ In English: "All other things being equal, smaller pulsejets can achieve higher thrust densities than larger ones."
While Mike's "pocket jet" boasts v. high thrust density, it does so at the expense of fuel efficiency. We may then
imagine that the ratio of volume specific thrust density to specific fuel consumption represents a possible metric
of interest to those working to optimise the size and efficiency of practical* pulsejets. Just not for this challenge.
* 'Practical' in the sense of fitness for purpose, eg., propulsion for civil transport aircraft, or high-endurance UAV.
Haiku later..?
Cheers,
M.
Come to think of it, I now expect that volume specific thrust density will peak at some minimum volume and then
decrease as volume tends to zero; this means that a plot may resemble a flat arc, with its peak shifted to the left.
no safe haven for merchant scum
for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT
avast!
Cap'n M.
for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT
avast!
Cap'n M.
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Ghrey
- Posts: 286
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- Contact:
Re: Interested ?
Had I only the time, I would most definitely make an entry.
I am a little perplexed however, I would think that using the power to weight ratio of an engine as the judging criteria would be a way to leave the contest completely open to all designs, regardless of size. This becomes more complicated if fuel efficiency is factored in but not that much. My reason for this line of thought is based only on my own modeling experiences, where the power plant was chosen by that criteria.
Consider the above as more a question than a suggestion.
I have managed to face a flat spot on the cap for the CC of my coaxial experiment, man am I slow or what.
I am a little perplexed however, I would think that using the power to weight ratio of an engine as the judging criteria would be a way to leave the contest completely open to all designs, regardless of size. This becomes more complicated if fuel efficiency is factored in but not that much. My reason for this line of thought is based only on my own modeling experiences, where the power plant was chosen by that criteria.
Consider the above as more a question than a suggestion.
I have managed to face a flat spot on the cap for the CC of my coaxial experiment, man am I slow or what.
In the process of moving, from the glorified phone booth we had to the house we have.
No real time to work on jets, more space, no time.
Life still complicated.
No real time to work on jets, more space, no time.
Life still complicated.
-
milisavljevic
- Posts: 855
- Joined: Sat Oct 04, 2003 9:36 am
- Antipspambot question: 125
Re: Interested ?
Hello "Ghrey",
You are correct in that power to weight (or specific power) is a standard metric for evaluating reciprocating engines.
Considering that reciprocating aeroengines are (all but) exclusively liquid-fueled, collecting fuel consumption data is
rather straightforward. Thus it makes sense to use these two metrics when comparing different aeroengine designs.
Pulsejets built by enthusiasts present certain difficulties wrt. the above. First of all, jet engines do not produce any
measurable power, at least while stationary, so we must substitute thrust for power. So why not thrust to weight as
our metric? If any of these engines were destined to power an aircraft, then building to minimum weight would be a
good plan; however, for pulsejets that may never move anything -- save a spring or bucket of water -- why put such
emphasis on weight, if the real challenge is to maximise thrust? Enthusiast-built pulsejets are (basically) pipes, and
as such, their weight is primarily a function of surface area and wall thickness. The enthusiast operating on a shoe-
string budget has limited options wrt. wall thickness, so please consider this following (not too unrealistic) example:
James Irvine has a much improved version of the "Chinese" style pulsejet with a 2.0 inch (50.8 mm) combustor. He
builds individual copies of this design by hand, from 0.5 mm thick stainless steel. Recently, he shipped two of them
to Mike Everman for testing, but for the sake of this example, let's pretend that James had only sent the plans that
Mike would then use to "roll his own" pulsejet from. While Mike could (technically) acquire 0.5 mm steel sheet, both
the practicalities of the US market and Mike's welding skill (no offense, Mike ) dictate that he weld thicker steel,
typically 0.035 inch (0.89 mm). Even if Mike meticulously maintained James' internal dimensions, his pulsejet must
weigh far more than James' original...approximately 80% more! This fact would discourage many builders, when the
central theme of this challenge is to encourage advances in thrust (or geometry), from as many builders as possible.
The second metric, fuel consumption, is similarly complicated by the simple fact that most enthusiast pulsejets are
run from propane vapor (vapour). While this is not true in valved pulsejets, this challenge is for valveless pulsejets.
The plain truth is that few builders ever measure fuel consumption, and we do not want to discourage participation.
In the end, if someone comes up with a extraordinary design, but lacks the skill or materials to optimise its weight,
there are talented and honorable (honourable) builders among us who would probably jump! at a chance to help out!
I vote to let the "competition" be friendly, fun and inclusive of all builders. The restrictions in place at the moment
are minimal wrt. impeding either creativity or participation; may a thousand flowers bloom, er...pulsejets roar!
C'mon, find the time -- and toss your "pipe" into the ring!
Cheers,
M.
You are correct in that power to weight (or specific power) is a standard metric for evaluating reciprocating engines.
Considering that reciprocating aeroengines are (all but) exclusively liquid-fueled, collecting fuel consumption data is
rather straightforward. Thus it makes sense to use these two metrics when comparing different aeroengine designs.
Pulsejets built by enthusiasts present certain difficulties wrt. the above. First of all, jet engines do not produce any
measurable power, at least while stationary, so we must substitute thrust for power. So why not thrust to weight as
our metric? If any of these engines were destined to power an aircraft, then building to minimum weight would be a
good plan; however, for pulsejets that may never move anything -- save a spring or bucket of water -- why put such
emphasis on weight, if the real challenge is to maximise thrust? Enthusiast-built pulsejets are (basically) pipes, and
as such, their weight is primarily a function of surface area and wall thickness. The enthusiast operating on a shoe-
string budget has limited options wrt. wall thickness, so please consider this following (not too unrealistic) example:
James Irvine has a much improved version of the "Chinese" style pulsejet with a 2.0 inch (50.8 mm) combustor. He
builds individual copies of this design by hand, from 0.5 mm thick stainless steel. Recently, he shipped two of them
to Mike Everman for testing, but for the sake of this example, let's pretend that James had only sent the plans that
Mike would then use to "roll his own" pulsejet from. While Mike could (technically) acquire 0.5 mm steel sheet, both
the practicalities of the US market and Mike's welding skill (no offense, Mike
) dictate that he weld thicker steel,typically 0.035 inch (0.89 mm). Even if Mike meticulously maintained James' internal dimensions, his pulsejet must
weigh far more than James' original...approximately 80% more! This fact would discourage many builders, when the
central theme of this challenge is to encourage advances in thrust (or geometry), from as many builders as possible.
The second metric, fuel consumption, is similarly complicated by the simple fact that most enthusiast pulsejets are
run from propane vapor (vapour). While this is not true in valved pulsejets, this challenge is for valveless pulsejets.
The plain truth is that few builders ever measure fuel consumption, and we do not want to discourage participation.
In the end, if someone comes up with a extraordinary design, but lacks the skill or materials to optimise its weight,
there are talented and honorable (honourable) builders among us who would probably jump! at a chance to help out!
I vote to let the "competition" be friendly, fun and inclusive of all builders. The restrictions in place at the moment
are minimal wrt. impeding either creativity or participation; may a thousand flowers bloom, er...pulsejets roar!
C'mon, find the time -- and toss your "pipe" into the ring!
Cheers,
M.
no safe haven for merchant scum
for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT
avast!
Cap'n M.
for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT
avast!
Cap'n M.
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milisavljevic
- Posts: 855
- Joined: Sat Oct 04, 2003 9:36 am
- Antipspambot question: 125
Haiku Romero
zombie breakfast, usa (in four courses)
a tide of shadows
retreats from the shores of dawn
only zombies stir
sleepy people rise
taking breakfast...while they too
are on the menu
(broken glass serenade)
crispy bacon strips!
eggs & brains: now there's a dish
coffee, milk or tea?
(thought not...)
minds are terrible
things...to fret (and gnaw) upon
seconds, anyone?
(the end...or ?)
The preceding poem was made possible by the sponsor of the previous post, which does mention the word "pulsejet".
I say! How very original.
M.
Last edited by milisavljevic on Mon Jun 02, 2008 5:11 am, edited 1 time in total.
no safe haven for merchant scum
for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT
avast!
Cap'n M.
for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT
avast!
Cap'n M.
-
Ghrey
- Posts: 286
- Joined: Fri Feb 15, 2008 8:41 am
- Antipspambot question: 125
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- Contact:
Re: Interested ?
Makes sense.
I can easily measure fuel consumption, but have NEVER had the inclination. The bigger bang the better has all ways done it for me.
My own efforts are all ways aimed at producing a power plant, usually for an aircraft.
Re: time
I have a 7 month old, teething, and a 3 year old, who is not "fully adjusted" to having a sister ( and he is 3 ... ), And my wife and I are the entire staff of a retail store that is open every day but monday.
The kids come to work.
As I say at the top, your explaination makes sense, and I thank you for your response.
My current "pipe" is a proof of theory piece, I doubt it will produce any thing but test data for a larger project.
It should however be delightfully LOUD.
I can easily measure fuel consumption, but have NEVER had the inclination. The bigger bang the better has all ways done it for me.
My own efforts are all ways aimed at producing a power plant, usually for an aircraft.
Re: time
I have a 7 month old, teething, and a 3 year old, who is not "fully adjusted" to having a sister ( and he is 3 ... ), And my wife and I are the entire staff of a retail store that is open every day but monday.
The kids come to work.
As I say at the top, your explaination makes sense, and I thank you for your response.
My current "pipe" is a proof of theory piece, I doubt it will produce any thing but test data for a larger project.
It should however be delightfully LOUD.
In the process of moving, from the glorified phone booth we had to the house we have.
No real time to work on jets, more space, no time.
Life still complicated.
No real time to work on jets, more space, no time.
Life still complicated.
-
Chadly33
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- Location: Australia
- Contact:
Re: Interested ?
OH MY GOD! I dont have internet at home as yet, didnt see what had happened to this post until I got to work monday morning!! All I wanted was to try to get people to come up with some new or outrageous designs hopefully creating something really unique in the process! Again, OH MY GOD!!lol
Bribie Islands resident mad scientist!http://www.geocities.com/ozpulse@y7mail ... 5835711956
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GRIM
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- Location: British living in Chile
Re: Interested ?
Gentlemen, I think the Challenge is a Great idea, but for it to be of any benefit , rules are a MUST, and i see a current "best in class"rather than an outright winner , as in a competition , i think this was chadleys original intention ,
I have some ideas/comments
The 250cc Combustión Chamber idea is fine but will mean tiny engines, too small to be of practical use for powering anything, and difficult to accurately measure thrust ,
I feel that the 1200 cc TOTAL VOLUME limit is a reasonable figure, this would include inlets, exhausts, combustión chambers, and could be easily verified with a measuring jug of water,
A vote on the above should settle the size issue
I Propose:-
1 Propane/LPG only as fuel, (it is available everywhere ) liquid or vapor, only one
cylinder/tank, any size ,
Ambient temperature will be an issue , i have recorded from 15 psi to 120 psi
static over the last year, depending largely on temperature, this will leave each to pick a
good day for his test
2 any style/number of injectors
3 Seperate class for augmented Engines,
4 Seperate class for liquid fuelled Engines , same total volume , Anything goes on the fuel
Any kind of pump, gasoline, gasahol, nitro, nitrous, etc , this should allow those that
have the means, to take their Engine to the very limit of current technology (or the
Darwin awards)
By far the best way to compare and define the best Engine would be to run all the Engines on the same thrust rig and on the same day, same conditions etc,
Unfortunately this is not practical , we have people from just about every continent in this forum , to coordinate the shipping of Engines alone, would be difficult , the people issues would be a nightmare ,
My feeling is that the only really practical measurement apart from thrust , is SFC.
Pretty well everyone will have access to bathroom scales, (the modern digital ones are not too expensive ) , just sit the gas cylinder on them and measure the time it takes to burn off one kg of fuel at a constant thrust , my way of thinking is that the best engine will be the one that has the lowest SFC , however i do think that the SLS thing may be a factor here, (see below,)
I am sure someone here could generate a web based calculador, OR zipped Excel so each could enter his thrust reading (kg/lbs) and his test site altitude (ft/M) amount of fuel used (kg/lbs) and time duration (seconds)
Personally I agree with the milisavljevic rules, there are just a couple of points that need clarifying ,
all thrust measurements altitude corrected to SLS (sea level static) ( can someone explain how to do this? )
The following need to be defined :- yes /no/definition
[4] Restrictions on fuels & fuel delivery systems
[c] restrictions on gaseous fuels (eg., propane)
[d] restriction on liquid fuels (eg., gasoline)
[e] restrictions for fuel injectors / nozzles
[e1] modulation (eg., reed valves) allowed ????? reed valved valveless?????
[5] Miscellaneous restrictions / requirements (TBD)
Just my 2 cents
GRIM
I have some ideas/comments
The 250cc Combustión Chamber idea is fine but will mean tiny engines, too small to be of practical use for powering anything, and difficult to accurately measure thrust ,
I feel that the 1200 cc TOTAL VOLUME limit is a reasonable figure, this would include inlets, exhausts, combustión chambers, and could be easily verified with a measuring jug of water,
A vote on the above should settle the size issue
I Propose:-
1 Propane/LPG only as fuel, (it is available everywhere ) liquid or vapor, only one
cylinder/tank, any size ,
Ambient temperature will be an issue , i have recorded from 15 psi to 120 psi
static over the last year, depending largely on temperature, this will leave each to pick a
good day for his test
2 any style/number of injectors
3 Seperate class for augmented Engines,
4 Seperate class for liquid fuelled Engines , same total volume , Anything goes on the fuel
Any kind of pump, gasoline, gasahol, nitro, nitrous, etc , this should allow those that
have the means, to take their Engine to the very limit of current technology (or the
Darwin awards)
By far the best way to compare and define the best Engine would be to run all the Engines on the same thrust rig and on the same day, same conditions etc,
Unfortunately this is not practical , we have people from just about every continent in this forum , to coordinate the shipping of Engines alone, would be difficult , the people issues would be a nightmare ,
My feeling is that the only really practical measurement apart from thrust , is SFC.
Pretty well everyone will have access to bathroom scales, (the modern digital ones are not too expensive ) , just sit the gas cylinder on them and measure the time it takes to burn off one kg of fuel at a constant thrust , my way of thinking is that the best engine will be the one that has the lowest SFC , however i do think that the SLS thing may be a factor here, (see below,)
I am sure someone here could generate a web based calculador, OR zipped Excel so each could enter his thrust reading (kg/lbs) and his test site altitude (ft/M) amount of fuel used (kg/lbs) and time duration (seconds)
Personally I agree with the milisavljevic rules, there are just a couple of points that need clarifying ,
all thrust measurements altitude corrected to SLS (sea level static) ( can someone explain how to do this? )
The following need to be defined :- yes /no/definition
[4] Restrictions on fuels & fuel delivery systems
[c] restrictions on gaseous fuels (eg., propane)
[d] restriction on liquid fuels (eg., gasoline)
[e] restrictions for fuel injectors / nozzles
[e1] modulation (eg., reed valves) allowed ????? reed valved valveless?????
[5] Miscellaneous restrictions / requirements (TBD)
Just my 2 cents
GRIM
-
milisavljevic
- Posts: 855
- Joined: Sat Oct 04, 2003 9:36 am
- Antipspambot question: 125
Re: Interested ?
IT'S... A-L-I-V-E-!!!Chadly33 wrote: ALL I wanted was to try to get people to come up with some new or outrageous designs
(emphasis added by M.)
I (for one) will work to keep the spirit of your original challenge in place. Let's kick the tires and light the fires!
Cheers!
M.
no safe haven for merchant scum
for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT
avast!
Cap'n M.
for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT
avast!
Cap'n M.
-
milisavljevic
- Posts: 855
- Joined: Sat Oct 04, 2003 9:36 am
- Antipspambot question: 125
Re: Interested ?
No worries. I totally got your message about having time for pulsejet experiments (or lack thereof...Ghrey wrote: I thank you for your response.
)!One suggestion: Forum member "hagent" [ memberlist.php?mode=viewprofile&u=100050 ] is in your area;Ghrey wrote: My current "pipe" is a proof of theory piece, I doubt it will produce any thing but test data for a larger project.
he also has an interest in testing concentric pulsejets. Maybe the two of you could collaborate... Why not?
You may use the forum private message service [PM] to contact him. "Nothing ventured, nothing gained."
Cheers,
M.
no safe haven for merchant scum
for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT
avast!
Cap'n M.
for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT
avast!
Cap'n M.
-
milisavljevic
- Posts: 855
- Joined: Sat Oct 04, 2003 9:36 am
- Antipspambot question: 125
Re: Interested ?
I agree! Takes the pressure off (if any), and may encourage more people to participate. You, for instance? ¿Sí?GRIM wrote: i see a current "best in class"rather than an outright winner, as in a competition,
i think this was chadleys original intention...
If you re-read the posts from "Chaddly33", you will see that "practicality" is not a priority. Small, powerful andGRIM wrote: but [it] will mean tiny engines, too small to be of practical use for powering anything
potentially portable pulsejets for demonstrations are what this challenge is all about. Sometimes less is more!
Personally, I agree. But pulsejets are not particularly sensitive to fuel choice (excepting "exotic" fuel choices).GRIM wrote: 1 Propane/LPG only as fuel, (it is available everywhere ) liquid or vapor, only one cylinder/tank, any size
A problem here is that certain injectors create significant momentum --THRUST-- even with the pulsejet off.GRIM wrote: 2 any style/number of injectors
Use of these injectors in small pulsejets will allow the clever "gamer" to easily best other entries; this is why
I recommended not allowing, for example, sonic and supersonic injectors (as may be found in pressure jets).
As I have mentioned before, subdivisions simply reduce the number of participants. It is not important whatGRIM wrote: 4 Seperate class for liquid fuelled Engines...
specific fuel a pulsejet burns, as they are relatively insensitive to fuel type. Covered in the suggested 'Rules'.
Some builders do not have this option (complaining neighbors, police, etc). Keep it simple for this challenge.GRIM wrote: [set a] gas cylinder on them and measure the time it takes to burn off one kg of fuel at a constant thrust...
GRIM wrote: Personally I agree with the milisavljevic rules, there are just a couple of points that need clarifying...
all thrust measurements altitude corrected to SLS (sea level static) ( can someone explain how to do this? )
Easy... "Good enough" is a simple ratio adjustment based upon elevation. If the test location is known, then
elevation can be looked up on the internet and in one more step, atmospheric pressure calculated (tabulated
data). Dividing this pressure into sea level standard pressure provides a ratio that is then multiplied against
the thrust reading; a refinement is to use the time and date of the test(s) and get local weather information.
GRIM wrote: The following need to be defined :- yes /no/definition
[4] Restrictions on fuels & fuel delivery systems
[c] restrictions on gaseous fuels (eg., propane)
[d] restriction on liquid fuels (eg., gasoline)
[e] restrictions for fuel injectors / nozzles
[e1] modulation (eg., reed valves) allowed ????? reed valved valveless ?????
WOW... You yourself used a LIST to spell out YOUR points, and yet you were unable to parse MY list? Hmmm...
It's lists-within-lists; try re-reading the list this way (I copied section [4..] over to this page for convenience):
[4] RESTRICTIONS ON FUELS & FUEL DELIVERY SYSTEMS
--- [a] no water injection (air-fuel mixtures ONLY)
--- no fuel additives / oxidisers (eg., nitrous)
--- [c] RESTRICTIONS ON GASEOUS FUELS (EG., PROPANE)
-------- [c1] tank at ambient temperature (no heating)
-------- [c2] tank insulation permitted (passive ONLY)
--- [d] RESTRICTIONS ON LIQUID FUELS (EG., GASOLINE)
-------- [d1] aspirated by pulsejet ONLY (no pumps)
-------- [d2] pulsejet-pressurised fuel tank allowed
--- [e] RESTRICTIONS FOR FUEL INJECTORS, NOZZLES
-------- [e1] modulation (eg., reed valves) allowed
-------- [e2] adjustable (eg., needle valve) allowed
-------- [e3] atomising liquid fuel injectors allowed
-------- [e4] (super)sonic vapor nozzles not allowed
-------- [e5] pulsejet-heated vaporiser coils allowed
About Rule [4-e.1] (ie., section 4, subsection e, part 1): some members have experimented with reed valves
to modulate fuel flow for increased efficiency, not air flow; so one can have a valveless pulsejet with a reed
valve installed in the fuel delivery system, just not functioning as an air intake valve. No contradiction there.
Hope this helps.
Cheers!
M.
no safe haven for merchant scum
for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT
avast!
Cap'n M.
for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT
avast!
Cap'n M.
-
GRIM
- Posts: 474
- Joined: Mon Jul 30, 2007 2:43 am
- Antipspambot question: 0
- Location: British living in Chile
Re: Interested ?
Mr M , thanks for the reply and for clarifying, I stand corrected on all points ,
I might add that I interpreted Chadleys "small powerful engine that could be used for hobby purposes " to mean rc aircraft" , Yet another lesson in ASS U ME , I will learn one day
I do indeed intend to participate in this challenge, once the basic design parameters have been defined,
It is a great opportunity for all forum members, Lets get some definitions posted and start building
The only point I see as needing to be defined is the CC OR OVERALL VOLUME ISSUE, I will go with either,
May I propose that we set a date, to define this issue ,one week from today maximum, so as not to kick the “why and why not” around for the next few months, until everyone is bored with the idea and it loses momentum, what think the other potential participants ??
Good luck to all those involved,
I might add that I interpreted Chadleys "small powerful engine that could be used for hobby purposes " to mean rc aircraft" , Yet another lesson in ASS U ME , I will learn one day
I do indeed intend to participate in this challenge, once the basic design parameters have been defined,
It is a great opportunity for all forum members, Lets get some definitions posted and start building
The only point I see as needing to be defined is the CC OR OVERALL VOLUME ISSUE, I will go with either,
May I propose that we set a date, to define this issue ,one week from today maximum, so as not to kick the “why and why not” around for the next few months, until everyone is bored with the idea and it loses momentum, what think the other potential participants ??
Good luck to all those involved,