Gluhareff 130R power failure issue still open ... Any Idear?

Moderator: Mike Everman

Locked
Dave
Posts: 227
Joined: Sat Nov 08, 2003 7:03 pm
Antipspambot question: 0
Location: Buffalo, NY

Recording

Post by Dave » Wed Feb 25, 2004 12:05 pm

Hello all:

GRAHAM: I ordered the Behringer B5 and it is scheduled for delivery today. Even if it does arrive as promised, I will only have a few minutes with it before I have to pack to leave for the trip. I plan to use the omni pickup and anticipate that I will need to use the -10db down switch because of the SPL. As a backup plan I intend to take along 3 dynamics. Not the best for this type of recording work, but you always have to have a backup plan. I also intend to run a pad between the mixer and the PC to drop the level enough to avoid clipping the input. Hopefully the input pad for the PC will also help to improve the signal to noise ratio. I have no concerns about the mixer, except that this will be the first time it will have a condenser microphone hooked to it. I hope the phantom power supply works as advertised. I finished loading the PC and gave the test a rig (minus the B5) a quick run. All appeared to be OK at the SPL I could muster in the house.

RAYMOND: Good point about the test plan. Unfortunately there is little time to put together all the proper details. With the help of those on the forum, we should be able to do a decent job. Because of the limited amount of time we have for both planning and execution I think this is a place to apply the KISS theory:

1. To get cold readings, do you suggest we try using something like compressed air or nitrogen through the fuel system to get a baseline?

2. I also remember something about a high pitched squeal in some of the old literature and it was not good. Hopefully, one of us can find the old references to that sound and what it means. We will try to get that recorded as well.

3. I plan to use Sound Forge v4.5h on the PC to do the recording. Unfortunately, there was not enough time to get an update to v7.0 before the trip. Advantages of using this software are that it has a time line and I can slice and dice the recording into as many pieces as is necessary. We should be able to edit out the throttle transitions, etc if this will improve your analysis.

4. Synchronizing events on the time line with various measurements, throttle adjustment, etc will require some kind of reliable reference point. Something as low tech as banging on a piece of metal to produce a recognizable transient might be enough. My only concern here is that the ambient noise of the engine could be so high that the transient would be lost.

VIV: "44.1KHz 16Bit WAV formatâ€

Viv
Posts: 2158
Joined: Sat Oct 04, 2003 2:35 pm
Antipspambot question: 125
Location: Normandy, France, Wales, Europe
Contact:

Post by Viv » Wed Feb 25, 2004 12:26 pm

Dave any thing you can get that is not clipped will be a help, Graham has in the past used the sound of the spark from the spark plugs as a referance in recordings:-)

I have seen Graham use two hardwood sticks banging them together to get a good transiant, makes a nice CRAACK when you bring them together fast, up to 100+db

The squeal is the inlet tract going in to resonance and yes we want that! a lot! if it don't squeal it is not working.

The flame front is a noise generator and that powers up the resonance of each part of the engine, but they have to add up constructivly to get the inlet tract pumping, thats why we want a good recording so we can see were every thing is resonating.

Se we realy need to hear it squeal:-) can you do that for me baby? squeal real laud:-)

The trouble with compressed air or nitrogen in the fuel line will be its cold, you would have to heat it to 1200f to get the same effect as a hot engine for it to be any good.

Each part of the engine is tuned to its own frequency of resonance like a violine, all together they form the overall tone of the engine but as each part operates at a differant temperature they are differant sizes to take acount of the change in the local speed of sound.

So if you try to excite the engine with an external sound source at one single temperature it wont work.

My final plan would be to use an fft in real time and tune the intake whith the engine running but before that we need to know whhat we are looking at.

Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

Viv's blog

Monsieur le commentaire

luc
Posts: 768
Joined: Fri Dec 05, 2003 5:05 pm
Antipspambot question: 125
Location: Quebec, Canada

130R Power failure

Post by luc » Wed Feb 25, 2004 1:17 pm

Hi guys,

Mark
Luc, It seems like you are headed in the direction of a rocket. There's only so much energy to be extracted from propane and air before you start to crumble/pulsate any structure within 20 feet of you. It might be interesting to mix propane and air with a fraction of liquid O2 or N2O.
Perhaps you are trying for a fuel/air bomb engine.
The only reasons I have posted the previous message about the engine location, is because we are about to do a sound recording of the engine and I was woundering if the eight of the engine could change or altered the reasults. The application were this engine will be use is still a sensitive matter for now, but beleive me, we are very far from a rocket purpose here.

The fact that this engine run on air and propane mixture is just what we want. Later on, I will probaly be able to tell you guys more about the application, but not now ... sorry.

Dave ... I got your phone and Email messages. I will call you today.

Regards,

Luc

luc
Posts: 768
Joined: Fri Dec 05, 2003 5:05 pm
Antipspambot question: 125
Location: Quebec, Canada

130R power failure

Post by luc » Wed Feb 25, 2004 1:47 pm

Viv, Dave, Raymond,

First, the high pitch noise (Squeeking or wissling noise) I was refering to in our previous posting, was when the nozzle get out of aligment due to thermal expansion. It create a cavitation in the 1st and 2nd stage. I don't know if you want that. When does that ... That a No No No for this engine and it will not go in reasonance (Sonic lock) until it stop doing that. But if you wnat that to, it is very easy to do. Actually, it is easier to do, then avoid.

Viv ... What is "FFT" I saw those abreviations a few times and could never figure out what it was. Please, always consider that I am probably not as brainiacs as you guys are ... He he he. I need longer explanations. But, your stuck with me ... Since I am the one with the engine and resouces ... Mouahahahahahaha... (Joke).

He he he ...

Cya,

Luc

Viv
Posts: 2158
Joined: Sat Oct 04, 2003 2:35 pm
Antipspambot question: 125
Location: Normandy, France, Wales, Europe
Contact:

Re: 130R power failure

Post by Viv » Wed Feb 25, 2004 2:04 pm

Luc wrote:Viv, Dave, Raymond,

First, the high pitch noise (Squeeking or wissling noise) I was refering to in our previous posting, was when the nozzle get out of aligment due to thermal expansion. It create a cavitation in the 1st and 2nd stage. I don't know if you want that. When does that ... That a No No No for this engine and it will not go in reasonance (Sonic lock) until it stop doing that. But if you wnat that to, it is very easy to do. Actually, it is easier to do, then avoid.

Viv ... What is "FFT" I saw those abreviations a few times and could never figure out what it was. Please, always consider that I am probably not as brainiacs as you guys are ... He he he. I need longer explanations. But, your stuck with me ... Since I am the one with the engine and resouces ... Mouahahahahahaha... (Joke).

He he he ...

Cya,

Luc
Is there a misunderstanding going on I wonder? the squealing noise I thought was the honking noise that has been refered to as the sound of the inlet stage going in to sonic lock.

Now this cavitation sounds interesting (I thought that was to do with liquids only?) can you explain a bit more on what happens when it does that.

Its the sonic lock sound I particulaly want to hear, now what ever everybody wants to discribe the sound like i am not worried as long as we all agree what it is!

FFT is short for fast fourer transform, a mathamatical term that will give you all the frequencys in a waveform, so we feed in the jet sound and it tells us were the engine is resonating and at what levels.

I have attached a picture of an FFT out put for a small gluey engine, notice that the dominant frequency is at about 150Hz followed by the second and third harmonics at double and triple the frequency but at steadily lower power levels.

Now I don't trust this one as the result is to linear and I was expecting to see the power levels in a differant relationship, but this was taken from a clipped sound sample so it is probably just reading the distortion products of the microphone.

Also attached is the original waveform (cleaned up a bit) as an osciliscope trace, the waveform is not a sine wave due to the harmonic content.

Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

Viv's blog

Monsieur le commentaire

luc
Posts: 768
Joined: Fri Dec 05, 2003 5:05 pm
Antipspambot question: 125
Location: Quebec, Canada

130R power failure

Post by luc » Wed Feb 25, 2004 3:01 pm

Hi Viv,
Now this cavitation sounds interesting (I thought that was to do with liquids only?) can you explain a bit more on what happens when it does that.
Okey, cavitation occure in almost all media. It happen when the flow your trying to move (Props, ventury, pumps ... ect.) exceed what the supply condition can provide (i.e: Ambiant air, water, tank head pressure).

In water for exemple, if your prop as to much pitch or the rpm is to high, it will move more water then it can suck up, creating a hole in water (Empty space under vaccum) wich is cavitation. It is a very destructive force. And you know that when your engine RPM goes off the roof for a split second.

Same thing for air, when the tip of a prop blade get faster then the speed of sound, the engine RPM goes Yaouuuu. This is also why fan engine don't have that type of problem, first : they have many blades, second : they are surounded by a cowling and third, they act more like a vaccum cleaner then a propeler blade. A good exemple of that ... Put your hand on your vaccum cleaner hose entrance and see what happen. The electric motor RPM goes higher. No air, vaccum condition.

Same thing with the ventury effect. When the nozzle get out of alignment, the air that is sucked in the first stage get uneven from one side to the other, flow circulation break and and cavitation occure.

Now, imagine the nozzle jet stream and the air suction like a chain. One drag the other in, in a linear and constent flow. Then, you move the nozzle left. So, the left side air suction continues while on the right side, the air sucked in slows down. What happen when your trying to pull in more then it can supply? ... Cavitation. The chain breaks, connect, breaks, connect many time a second and the noise is heard.

Ther you have it. I will try to post a video were you see our pressurejet doing that.

Bye the way ... I have 2 tricky questions for you guys. One is easy but the other is more tricky.

1) What mostly, make a plane fly, the top or bottom of its wings?

2) As for a piston engine propeler, does it push or pull the plane?

Also, air cavitation is also why we have varaible pitch on props today. Takeoff = fine pitch = slow but strong. Cruise = coarse pitch = fast but easy to stall.

Also, a wing that stall in air, is a wing that cavitates. Look at a wind tunel air flow on a stalled wing and look at cavitation in a water pipe, it's the same thing.

Cya,

Luc

luc
Posts: 768
Joined: Fri Dec 05, 2003 5:05 pm
Antipspambot question: 125
Location: Quebec, Canada

130R Power failure

Post by luc » Wed Feb 25, 2004 4:43 pm

Okey Viv budy,

I have extracted a sound track from a .mpg video recorded with a Sony camera. The quality may not be good due to the camera cheap microphone but you clearely hear the high pitch wisseling noise when the enginer is warming up. At the end, the steady grounding sound is the engine sound when at max power.

I hope it put some light on what I mean by "High pitch wisseling noise".

Cya,

Luc
Attachments
PressureJet Noise.zip
(376.01 KiB) Downloaded 227 times

Viv
Posts: 2158
Joined: Sat Oct 04, 2003 2:35 pm
Antipspambot question: 125
Location: Normandy, France, Wales, Europe
Contact:

Post by Viv » Wed Feb 25, 2004 5:25 pm

Now this is a bit interesting, just a quick run with the FFT

Look at the differance between the full power waveform and the mid power waveform

belowe the wavform is the fft plot, you can see that the power levels in the harmonics have reversed.

midpower level, the fundamental frequency has the highest power level and the harmonics are surpresed but later this reverses and the waveform develops a notch were another harmonic is now interfering.

the midpower waveform matches the fft and shape from the smallewr gluey engne

Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

Viv's blog

Monsieur le commentaire

Viv
Posts: 2158
Joined: Sat Oct 04, 2003 2:35 pm
Antipspambot question: 125
Location: Normandy, France, Wales, Europe
Contact:

Post by Viv » Wed Feb 25, 2004 5:33 pm

If you are having a problem with this stuff have a look at this link as it illistrates the the basic method the gluey uses in the inlet duct diffuser to stabilize the flame front.

Note that the resultant wave being relected is twice the amplitude of the wave going towards the barrier.

Thats what gives the extra compression.

http://www.walter-fendt.de/ph14e/stwaverefl.htm

Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

Viv's blog

Monsieur le commentaire

Viv
Posts: 2158
Joined: Sat Oct 04, 2003 2:35 pm
Antipspambot question: 125
Location: Normandy, France, Wales, Europe
Contact:

Post by Viv » Wed Feb 25, 2004 5:48 pm

well lets not get too excited but when Dave gets his stuff set up and you have a done a few runs why not try tuning the inlet and throttle while looking at thereal time wavform on the pc.

Try to keep it looking like the mid power.jpg image rather than the full power one.

Its that nasty looking notch in the full power one that is the problem, if you can do that and look at the thrust reading from the load cell we may be on to a winner:-)

Maybe!

Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

Viv's blog

Monsieur le commentaire

Dave
Posts: 227
Joined: Sat Nov 08, 2003 7:03 pm
Antipspambot question: 0
Location: Buffalo, NY

Recording / FFT

Post by Dave » Wed Feb 25, 2004 6:17 pm

Viv:
At this point I am only equipped to do a recording. Although I can see the waveform enough to identify clips, I do not have the right software to do FFTs. My plan was to send the data on to those of you with all the right stuff (software and grey matter) to do a proper analysis. If you can recommend something that I can pick up cheaply along the way to Luc’s place, I may be able to give it a go. Hey, maybe we just have to do another trip later with better tools. (Or is that toys? Sometimes it’s hard to tell which is which!)
Dave
PS: Luc, 1. The top. 2. It pulls?

Viv
Posts: 2158
Joined: Sat Oct 04, 2003 2:35 pm
Antipspambot question: 125
Location: Normandy, France, Wales, Europe
Contact:

Re: Recording / FFT

Post by Viv » Wed Feb 25, 2004 6:50 pm

Dave wrote:Viv:
At this point I am only equipped to do a recording. Although I can see the waveform enough to identify clips, I do not have the right software to do FFTs. My plan was to send the data on to those of you with all the right stuff (software and grey matter) to do a proper analysis. If you can recommend something that I can pick up cheaply along the way to Luc’s place, I may be able to give it a go. Hey, maybe we just have to do another trip later with better tools. (Or is that toys? Sometimes it’s hard to tell which is which!)
Dave
PS: Luc, 1. The top. 2. It pulls?
Dave you could probably get away with just looking at the waveform for now.

Thats why I included the good one and the one with the big notch cut out of it, if you can see that on the screen then just adjust things as best you can to clean up the waveform.

The fft in real time would be nice but hey I think just an osciloscope trace would be good at the moment.

Just compare the screen to the thrust reading as you do it and see what does the best.

Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

Viv's blog

Monsieur le commentaire

luc
Posts: 768
Joined: Fri Dec 05, 2003 5:05 pm
Antipspambot question: 125
Location: Quebec, Canada

130R Power Failure

Post by luc » Wed Feb 25, 2004 9:58 pm

Viv,

A few question for you :

1) Can we run an FFT program in real time?

2) If you have the program, is it big and if not, can you send this via Email.

3) I have an osiloscope here. What can we hook up to it to get a signal?

This one if for Dave :

Dave, does your equippment or equalizer has an output that we could send to the osiloscope?

Guys, remember that this engine intake stack has a 5 axis adjustment and we can move this thing in all direction.

Also, remember in one of my previous posting, I have calculated that my 2nd stage does not have the same frequency as the engine chamber/3rd stage combination. My calculations tell me that the 2nd stage is aprx. 1/2 inch to long.

Waiting for your answers guys.

Tomorow is the big day....

Cya guys.

Luc ............ Out

Viv
Posts: 2158
Joined: Sat Oct 04, 2003 2:35 pm
Antipspambot question: 125
Location: Normandy, France, Wales, Europe
Contact:

Re: 130R Power Failure

Post by Viv » Wed Feb 25, 2004 11:42 pm

Luc wrote:Viv,

A few question for you :

1) Can we run an FFT program in real time?

2) If you have the program, is it big and if not, can you send this via Email.

3) I have an osiloscope here. What can we hook up to it to get a signal?

This one if for Dave :

Dave, does your equippment or equalizer has an output that we could send to the osiloscope?

Guys, remember that this engine intake stack has a 5 axis adjustment and we can move this thing in all direction.

Also, remember in one of my previous posting, I have calculated that my 2nd stage does not have the same frequency as the engine chamber/3rd stage combination. My calculations tell me that the 2nd stage is aprx. 1/2 inch to long.

Waiting for your answers guys.

Tomorow is the big day....

Cya guys.

Luc ............ Out
Yes you can run the fft in real time and yes the program is small but it runs on Unix! Apple OS X to be precise sorry about that fella:-) I have moved on from that Pcee windoz stuff I am afraid.

Its called Amadeus ll and costs all of $30 ! we have used it succesfully for the last few years with the pulse jet projects.

There are PCee programs but I have never found a good one that did not cost an arm and a leg.

As you have the scope just hook it up to the line output of the preamp dave will be using, the scope input will have a high enough input impedance so it wont affect it.

Try to get a trace that looks like the mid power picture I posted, what you don't want is one that looks all notche like the high power one.

The only problem is we still do not have enough results to know what the correct tuning is supposed to be! once you can give us some results we can work out what the correct relationship is for the harmonics to be in, and phase I should add:-)

And yes I remember you saying about the 5 axis adjustment, thats a grait help, the fact that one of the stacks is over long is a concern to me!

Thats like saying one of the freackin tyres is flat and is that why my car wont go in a strait line:-)

Can it be made adjustable?

By the way the second stage being to long will throw out the phase relationship of the standing wave that is being locked up by the hole in the third stage diffuser.

That would be why it never made much differance.

Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

Viv's blog

Monsieur le commentaire

Dave
Posts: 227
Joined: Sat Nov 08, 2003 7:03 pm
Antipspambot question: 0
Location: Buffalo, NY

Recording issues

Post by Dave » Thu Feb 26, 2004 4:49 am

Hello All:

To prove that Murphy’s Law is still alive and well, the condenser microphone I ordered for the recording session did not arrive today as promised. @#$%&*> I am one bummed out puppy. I guess this is why we make backup plans. We will still do our best to get clean recordings, but they will not be of the quality I had hoped for.

Graham: Instead of using the condenser I will have to drop to dynamic microphones. They are not omni directional, but I do have three of them. Do you suggest sticking with just one, or would you think that 2 or more would give better results? Placement will be a bit of an issue because of the heat, but any advice here would be greatly appreciated.

Luc and I talked today about the O scope hookup. Since the mixer has multiple outputs this should not be a problem, as long as the input impedance is high enough and shielding is not an issue. I do think that we should get at least one good clean recording on disk before we hook it up, just in case it induces additional noise into the system.

I will be on the road all day tomorrow and will not have access to email. However, Luc has my cell phone number if any questions come along the way. Hopefully we can generate enough data in one day to make some headway. If not, we may be able to try again at a later date with better equipment.

Dave

Locked