OB_boneman
Registered
>>Has anyone worked through the figures yet
>>to find out what the increase in intake
>>air pressure would be at certain speeds,
>>and using this what increase in power this
>>would lead to?
Yes
>>I've been thinking you see, you know how a
>>bow wake on a boat protrudes from the
>>front, does this not happen the same on a
>> motorcycle?
yes, on cars, trucks, aircraft anything moving through the air. Varies in strength with alt/vel/temp, planet alignment (haha, just kidding)
>>so there is a build up of air
>>pressure in the intake pipes (because I am
>>sure that at 160mph (say) all the ram air
>>can't be used). This excess air then has to
>>spill over back out of the air ducts.
Correct to an extent, it's called spillage
drag or Ram Drag. Not
really applicable to bikes that travel at
such low speeds, i.e. it's effects are
negligable compared to the drag
effects created by other things like body position, fairing design etc. and because of
the low subsonic speeds it's even less of a
player.
>>Okay. Now. If the ducts have an edge that
>> is angled backwards, like Busa's, this
>>would not cause any extra drag, forward
>> pressure, call it what you like.
Not quite sure what you mean but if you're
refering to the angle of the plane at which
the lnlet faces as viewed from above, it will
still create a bow plane if you will.
Doesn't matter what it's shaped like. Or the fact that it can "slip" around, like I said,
pretty negligable effect in this case. On an
aircraft shape will play a big roll on drag,
engine performance, recovery etc..
>>Following this argument through, the 12,
>> with its letterbox right in the middle,
>> has no means to allow the excess air to
>> escape backwards without a fight from the
>> oncoming air at 160mph. Hence a bow wake
>> starts. Forward pressure. Perhaps this is
>> enough to cause increased drag.
No, not at all, in fact the zx12's inlet is more than likely a better performer because
it's reaching further out into the freestream and not taking in as much low energy boundary layer than the busa is (I dare say it's not far enough out to reach the freestream but
a better attempt than the busa). It is that way for a very good reason. I'd go into
diverters and what not but I don't want to bore you too much.
As far as a pressure rise goes people who say they get more than about 0.7psia (ssl) of
boost in the airbox are defying the laws of physics. That amt is also provided you're
doing about mach 0.26 or app 200mph and you have zero losses in your inlet and you're at
standard sea level conditions (ssl).
So it's even less than that if you're lucky.
Ratio of total to static pressure (pt/po) = (1+((gama-1)/2)*M^2)^^(gama/(gama-1)) gama = 1.4, M=0.26 in our example pt/po = 1.048, take this value times standard atmospheric pressure 14.696psia = 15.401psia, that pressure delta is equal to 0.7psia.You can check this out in any aero book that deals with compressible flow fields.
To get over 1psia you'd need to be doing about mach 0.371 or app 300mph, not going to happen on a bike any time soon. Most bikes will get about 7-10hp on a good day at top speed from results I've seen.
>>I DONT KNOW. THIS IS PURE SPECULATION.It
>>just got me thinking thats all
Good to see someone using that gray matter up there. The web is full of useful (and not so useful) info and simple to read articles, one site comes to mind is
http://www.geocities.com/CapeCanaveral/Lab/3481/jetlesson/jetlesson.html
Stick with reputable sources like nasa sites as best you can, I've seen some that are just full of !@#$.
>>Anyone care to work through it with me??
If you've got a few days.
Boneman - Propulsion Engineer X-35B
>>to find out what the increase in intake
>>air pressure would be at certain speeds,
>>and using this what increase in power this
>>would lead to?
Yes
>>I've been thinking you see, you know how a
>>bow wake on a boat protrudes from the
>>front, does this not happen the same on a
>> motorcycle?
yes, on cars, trucks, aircraft anything moving through the air. Varies in strength with alt/vel/temp, planet alignment (haha, just kidding)
>>so there is a build up of air
>>pressure in the intake pipes (because I am
>>sure that at 160mph (say) all the ram air
>>can't be used). This excess air then has to
>>spill over back out of the air ducts.
Correct to an extent, it's called spillage
drag or Ram Drag. Not
really applicable to bikes that travel at
such low speeds, i.e. it's effects are
negligable compared to the drag
effects created by other things like body position, fairing design etc. and because of
the low subsonic speeds it's even less of a
player.
>>Okay. Now. If the ducts have an edge that
>> is angled backwards, like Busa's, this
>>would not cause any extra drag, forward
>> pressure, call it what you like.
Not quite sure what you mean but if you're
refering to the angle of the plane at which
the lnlet faces as viewed from above, it will
still create a bow plane if you will.
Doesn't matter what it's shaped like. Or the fact that it can "slip" around, like I said,
pretty negligable effect in this case. On an
aircraft shape will play a big roll on drag,
engine performance, recovery etc..
>>Following this argument through, the 12,
>> with its letterbox right in the middle,
>> has no means to allow the excess air to
>> escape backwards without a fight from the
>> oncoming air at 160mph. Hence a bow wake
>> starts. Forward pressure. Perhaps this is
>> enough to cause increased drag.
No, not at all, in fact the zx12's inlet is more than likely a better performer because
it's reaching further out into the freestream and not taking in as much low energy boundary layer than the busa is (I dare say it's not far enough out to reach the freestream but
a better attempt than the busa). It is that way for a very good reason. I'd go into
diverters and what not but I don't want to bore you too much.
As far as a pressure rise goes people who say they get more than about 0.7psia (ssl) of
boost in the airbox are defying the laws of physics. That amt is also provided you're
doing about mach 0.26 or app 200mph and you have zero losses in your inlet and you're at
standard sea level conditions (ssl).
So it's even less than that if you're lucky.
Ratio of total to static pressure (pt/po) = (1+((gama-1)/2)*M^2)^^(gama/(gama-1)) gama = 1.4, M=0.26 in our example pt/po = 1.048, take this value times standard atmospheric pressure 14.696psia = 15.401psia, that pressure delta is equal to 0.7psia.You can check this out in any aero book that deals with compressible flow fields.
To get over 1psia you'd need to be doing about mach 0.371 or app 300mph, not going to happen on a bike any time soon. Most bikes will get about 7-10hp on a good day at top speed from results I've seen.
>>I DONT KNOW. THIS IS PURE SPECULATION.It
>>just got me thinking thats all
Good to see someone using that gray matter up there. The web is full of useful (and not so useful) info and simple to read articles, one site comes to mind is
http://www.geocities.com/CapeCanaveral/Lab/3481/jetlesson/jetlesson.html
Stick with reputable sources like nasa sites as best you can, I've seen some that are just full of !@#$.
>>Anyone care to work through it with me??
If you've got a few days.
Boneman - Propulsion Engineer X-35B
