Measuring Pressure Pulses

[horse]

i think what would be more useful would be a signal generator conneced to a small speaker on the end of a PVC pipe of X length, find a harmonic of this length with the signal generator, then add stuff like a bellmouth, a taper, a pulse plate etc etc and see what happens to the freq of the harmonic, and the volume of the released sound.

Ed, the only problem i can see here is that testing of tapers will yield different results when used with a speaker as that changes the harmonic of the tube/wave characteristics , where as the taper for you would be for the venturi effect which relies more on the movement of air via suction (vacuum).

[ed]

true, ok, remove tapers from the independent variable list

[mrshin]

ps - why doesnt anyone ever join my forum - it makes me feel sad

*sigh*

Look, if it makes you feel any better, well, I might just join....

[ed]

yay! add one! lol... *

*i have no life - this is important to me

just added a whole bunch-o-shit re: instrument acoustics and the impact of the bell on harmonics and reflection co-efficient/sound loss to atmo etc

[river]

Hi,

A potential problem with using a speaker is it has it's own natural resonance and Q (damping) factor which needs to be accounted for in your tests. Also a speaker has a limited amount of travel and this could also taint you test results.

seeyuzz
river

PS: ed, love to join your forum...... when I get a 1UZ engine.

[ed]

yup i agree, speaker and pipe need to be mated. but if you can establish just one good harmonic, the you should be able to find measurable effects of bellmouths and pulse plates etc which if you were on my forum youd realise this is where the discussion started, which has nearly nothing to do with 1uz, actally most of the site doesnt

[allencr]

Any fan, SC, blower, vacuum cleaner or turbo/turbine will put out air, but at a steady state, and that's not what you want.
What you'd need is a single or multi piston compressor, driven at variable speeds and even that won't mimic what an intake valve does to air flow.
I think it's a waste of time trying to emulate an engine, when the engine itself is the best test bed. Sure you'll find out what's best at a specific RPM, but then you've got to decide whether it's more important for total power or lower power with a wider range.

[river]

Hi,

You could have a butterfly valve in the output tube, and have this connected to a small motor that you can vary the rpm on - and you will need to know what rpm the butterfly is spinning. This will disrupt the flow, but perhaps not the way an inlet valve would do so - but it's still better than a steady, constant stream of air.

seeyuzz
river

[ed]

i dont think ben is trying to model an engine, rather play with different physical parameters and their effects on the harmonics and strength of reflected pulses in intake tracts

[river]

Hi,

I'd like a simple diagram of the proposed test-rig that will be used for this. I'm a picture guy and it will help me understand.... and maybe... just maybe I can then contribute something.

seeyuzz
river

can we talk about carbies on v8.com?

[horse]

i believe this is the test that ben is thinking of setting up.

A - test of bell mouths r/d, pulse plates etc
B - test of runner length to get ideal harmonic
C - attach dril to SC14/SC12 pulley

this way you can kinda of replicate a intake flow through a runner.
though i may be wrong

[The Witzl]

Ed, I dont want to join your forum because of the shameful truth of my academic background, i think i would not be welcomed....

[ed]

can we talk about carbies on v8.com?

if you know anything about pulse plates, be my guest!

[Ben Wilson]

PS: ed, love to join your forum...... when I get a 1UZ engine.

It also mentions "associated technologies", that's the bit I joined for

Any fan, SC, blower, vacuum cleaner or turbo/turbine will put out air, but at a steady state, and that's not what you want.
What you'd need is a single or multi piston compressor, driven at variable speeds and even that won't mimic what an intake valve does to air flow.

The sc12 is a rootes type blower, its input and output is anything but steady state. If you crank one up open you can clearly hear the pulses. I agree that it will be nothing like an inlet valve, but short of setting up a motor, it's the best I can come up with. If you want to contribute to a fund to get an engine dyno in my shed feel free

The speaker idea has some merit, but it only simulates part of the equation. I'm not sure, but I believe that having the air being actively pumped through the pipe will effect the results.

[wilbo666]

Look, if it makes you feel any better, well, I might just join....

aww heck ed, i'll join soon for you too

Cheers
Wilbo