port flows of 3sge BEAMS

[Billzilla]

Also, the ultimate goal would be to acheive a port speed that is close to or greater then the speed of sound. Being 1128 CFP
It has been acheived on a test tube, but how to do it on a port?

Well no.
The maximum (average) speed you want lies somewhere between M 0.3 and M 0.4.
You will never get near M 1.0 due to frictional effects, nor do you want to.

[jeffro ra28]

Well no.
The maximum (average) speed you want lies somewhere between M 0.3 and M 0.4.
You will never get near M 1.0 due to frictional effects, nor do you want to.

Ok fair enough on "nor do you want to".
But it is possible to do. (half the speed of sound, my bad)

[Billzilla]

Ok fair enough on "nor do you want to".
But it is possible to do.

Not with a piston engine.

[jeffro ra28]

I havent studied enough of the topic to be sure of this at all. I realise this is complete a stab in the dark aswell. But for the sake of discussion.

Using the flow bench and some fidly machining, i have acheived a ram tube style test peice, that flows extremely close to this mach 1 speed. It has almost a complete energy balance meaning it is almost completely silent ( i cannot here it with my ears) when flowing from 0-38" of water. When the depression is increased to around the 38" mark it has a slight unbalance, meaning it starts making noise, then after about 50" of pressure it becomes silent again, however stops flowing any air. At about the stage where it starts to make noise, the air flow will not go any higher, regardless of how much higher the depression is. I only bring this up because i am keen to learn more about it and to see what others think about this experiment.

[Billzilla]

I havent studied enough of the topic to be sure of this at all. I realise this is complete a stab in the dark aswell. But for the sake of discussion.

Using the flow bench and some fidly machining, i have acheived a ram tube style test peice, that flows extremely close to this mach 1 speed. It has almost a complete energy balance meaning it is almost completely silent ( i cannot here it with my ears) when flowing from 0-38" of water. When the depression is increased to around the 38" mark it has a slight unbalance, meaning it starts making noise, then after about 50" of pressure it becomes silent again, however stops flowing any air. At about the stage where it starts to make noise, the air flow will not go any higher, regardless of how much higher the depression is. I only bring this up because i am keen to learn more about it and to see what others think about this experiment.

Interesting!
But not entirely relevent to an engine inlet, as they have a very stacatto flow. As you know, the airflow stops and starts extremely violently, and there's never a really good vacuum so you won't get much past about M 0.8 odd even at full flow.

[jeffro ra28]

Ok, but IF you could get the air flow to exceed te speed of the sonic pressure wave (around 1100 ft/s) what do you think would happen?

[Billzilla]

Ok, but IF you could get the air flow to exceed te speed of the sonic pressure wave (around 1100 ft/s) what do you think would happen?

I think would work much like a boosted engine.

But the trans-sonic drag precludes this ever happening. So that's why we push more air in at the same speed, with a turbo or supercharger.

[jeffro ra28]

Ok, all taken in So, that would be why we cannot exceed M 0.8.

Also, averages put aside, how can we determine the desired MAXIMUM air velocity?

[Billzilla]

Ok, all taken in So, that would be why we cannot exceed M 0.8.

Also, averages put aside, how can we determine the desired MAXIMUM air velocity?

I'm not 100% sure, but they're still related and can't really be ignored I suspect - My reasoning is that in constant free-flow, as you've shown, you can get very good flow but with an engine inlet and it stopping and starting you really have to take into account not only the maximum flow, but the length of the inlet at certain revs ...... which leads to averages again.

[jeffro ra28]

Just opening up another can of worms for me

So what is the reasoning behind not wanting any more average port speed then M 0.4?

[Billzilla]

Just opening up another can of worms for me

So what is the reasoning behind not wanting any more average port speed then M 0.4?

That I'm not too sure about either, but it seems to be a fairly reliable figure.
So Empirical results are all I have to offer here sorry.

[jeffro ra28]

Thats why i would like to acheive it, so i can prove it.
Know one i know has been able to come up with an answer for me yet

[oldcorollas]

Well no.
The maximum (average) speed you want lies somewhere between M 0.3 and M 0.4.
You will never get near M 1.0 due to frictional effects, nor do you want to.

what are peak port speeds?
say the valve is (nominally) open for sayy 300deg out of 720, and of that, it will not be flowing extremely quickly for the first X degrees after opening (depending on the pressur eof th ebuilt up air and the reflected waves.

[Billzilla]

what are peak port speeds?
say the valve is (nominally) open for sayy 300deg out of 720, and of that, it will not be flowing extremely quickly for the first X degrees after opening (depending on the pressur eof th ebuilt up air and the reflected waves.

I've seen figures up around M 0.8, but I can't remember where I've seen that sorry.

Most of the effective flow comes from the reflected pressure wave as well. That's how you get over 100% VE.

[Fish]

so i guess when you get to speeds about M0.8 turburlance is met and that kills the effectiveness of the port?