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Posted:
Sat Oct 01, 2005 6:46 pmby Jesse Lackman
I read old posts from this board and the old board until 2am this morning and decided on using one of those pitot flow tuber do-jobbers with the FP-1.
My reasons will remain private for a while because I really don't know what I'm doing.
Plus this way I will have someone very visible and specific to blame for any problems, that person being Bruce.
The pitot flow tube will go in the Mercdog bench. I don't know where just yet.
The flow will be reversable through the pitot flow tube and head fixture, because it's logical to me, on superficial level at least, to suck from the chamber through the intake valve and blow from the chamber through the exhaust valve.
I'd like the bench running by this year's end.
There I said it, now hang on.....
Posted:
Wed Oct 05, 2005 2:30 amby blownS10blazer
So how's it goin' Jesse? I am new to this site and presently gathering information to build my own flowbench and I know nothing about it, yet. Are you making progress? Just curious.
Steve
Posted:
Fri Oct 14, 2005 9:52 pmby Jesse Lackman
Boy, that is strange, every place I used the word "averaging pitot tube" in the compost post box got changed to "averaging pitot tube" in the preview post box and in the actual post.
Here is proof;
What is the hidden meaning of that?
Posted:
Fri Oct 14, 2005 9:57 pmby Jesse Lackman
anubar
averaging pitot tube
annubur under the saddle
I guess I just have to deliberately misspell a n n u b a r
This is a strange way for Bruce to show he is the A n n u b a r King of this forum.
Posted:
Fri Oct 14, 2005 9:58 pmby bruce
The word "a n n u b a r " is a registered product name so the forum is setup to change it to averaging pitot tube.
Posted:
Fri Oct 14, 2005 10:12 pmby bruce
Here is a few pics of the back of my bench, My cabinet is about the same size as what you are working with. These pics are kinda outdated, I'll see if I can take some new ones.
Should give you some ideas?
Posted:
Sat Oct 15, 2005 12:38 pmby Jesse Lackman
Thanks Bruce.
I've been reading about different averaging pitot tube shapes specifically elliptical.
This shape evidently has accuracy and turndown advantages.
If the turndown can be increased one would not have to have two flow sections, the entire flow range could be covered with one section.
This averaging pitot shape is interesting;
What I don't understand is how the hp and lp sources are seperated in the tube. An averaging pitot tube is obviously more than a simple piece of tubing.
Posted:
Sat Oct 15, 2005 1:29 pmby Mouse
Jesse,
Really good looking bench and workmanship!
I have to say, however, I really don't know how you will be able to fit a Pitot tube type flow element into there. But, that's just me. I hope you can do it.
If you have to make a sharp turn, do it by splitting the air path with a Y and then make the turn using another Y. We call those a "Tighty-Righty" (Tight Right angle turn).
John
Posted:
Sat Oct 15, 2005 2:06 pmby Jesse Lackman
John, I re-read that flowbench accuracy speedtalk thread last night, very good information there. That's what prompted the pitot tube shape post above.
Are you referring to the fitting the pitot tube element in the valve chamber?
The only way I think that would work is if I offset the head flow fixture and ran the vertical piping feeding the head fixture through the motor chamber. I think there would be enough length that way but reversing the pitot for flow reversal presents a problem. That might mean the pitot tube element might be better mounted on the upper back of the bench. The pitot would be easily accessible from the front manometer panel for reversal.
Posted:
Sat Oct 15, 2005 4:53 pmby bruce
Yes an averaging pitot can be as simple as a single tube, I use one everyday and its repeatable and accurate for a flowbench application. Its nothing more than a brass tube drilled with 6 holes using dimensions from the airflow industry for duct traversing. Additional, I have seen no flow problems on my bench with the 90* turn. I do have a section right after the turn with a honeycomb flow straightener. I found this made actually no difference in flow readings on my bench.
On the averaging pitot that I make the velocity pressure is measured with the pitot and there is a seperate static pickup located 1/2" in front of its location. These two are feed into a FP1 which gives me my readings on my laptop. I take my static test depression pickup in the chamber just below my test peice. This is a .062" hole drilled into the chamber wall with a fitting on the outside.
Posted:
Sat Oct 15, 2005 7:52 pmby Mouse
Posted:
Sat Oct 15, 2005 8:49 pmby Jesse Lackman
Posted:
Sat Oct 15, 2005 9:02 pmby Jesse Lackman
Quick reply here Bruce, interesting that the honeycomb straightener didn't change the readings.
I think the critical areas re accuracy and repeatibility will be;
the pitot tube section which should include upstream and downstream flow straighteners
and
the piping leading to the test fixture, I think flow straighteners there would be a good idea, (especially if the bench reverses flow for exhaust testing).
I think one could put all the bends you wanted outside of those two areas and all it would do is affect total flow, and not do much to the accuracy or repeatability of the bench. (Of course the bench and piping between the pitot section and cylinder head would have to have no leaks for this to be the case, your 90 seems to bear this out.)
However, I do reserve the right to be wrong.
Posted:
Sun Oct 16, 2005 11:19 amby Mouse
