Rob and I figured out the coefficient (~0.36) for the McMaster orifice ( https://www.mcmaster.com/#2712t47/=1agjtnf) and the hole size (3/8") we need to drill in it. (drilling the hole will change the coefficient but this is the most conservative). This will result in ~200 psi drop across the orifice at the 3 lbm/s flowrate. If we use two of these transducers https://www.omega.com/pressure/pdf/PX119.pdf the error should remain significantly below 10% leaving us room to add error by drilling the hole in the orifice.
On Tue, Nov 28, 2017 at 1:01 PM, Bertrand DeChant <[email protected]> wrote: > Undesirable conditions should result in failsafe(likely shutdown and > Purge). Mitigation of sensing error(extreme) should be considered. This is > not an issue for pintle testing where pressure data can be calibrated and > used only for water. > > On Nov 28, 2017 12:55 PM, "Joseph Shields" <[email protected]> wrote: > >> > If all else fails in this regard, we're out about $100 as opposed to >> $$$ for a gox safe transducer. >> >> If you got misleading pressure measurements from it, what other parts >> might get damaged? Like, say you got a low measurement and opened some >> upstream valve in response. >> >> On Nov 28, 2017 12:49 PM, "Bertrand DeChant" <[email protected]> >> wrote: >> >> Absolutely, the ones that were previously specc'd for the engine should >> work well in this pressure range. These would be recycled for the igniter >> (engineer chamber pressure) and the engine (fuel manifold pressure). I'll >> look at the specs and point out expected factors of error this afternoon or >> evening. As for an oxygen environment it seems the previous plan to >> standoff/pack is the industry standard and reasonable for our budgeting >> needs. If all else fails in this regard, we're out about $100 as opposed >> to $$$ for a gox safe transducer. >> >> On Nov 28, 2017 12:40 PM, "Erin Schmidt" <[email protected]> wrote: >> >>> Hi guys, >>> I'm sick and won't be coming to the meeting tonight. For what it is >>> worth here are my thoughts: >>> -I think we should aim for <10% measurement uncertainty. >>> --This probably is expensive to achieve over our range of flow rates >>> with most kinds of flow meters (though we could do more research here). >>> --The dP tranducer has error +/- 5 psig, if we pick the larger >>> orifice we will have 50% measurement uncertainty at the 1 lb/s flowrate. If >>> we want to lower the uncertainty by increasing the pressure drop, then we >>> need to factor in the added expense of the higher-pressure dP sensor (note >>> that even the 260psi dP sensor would have ~17% error @ 1 lb/s). >>> --Probably our best bet is to use 2 transducers in lieu of a single >>> dP transducer. Some of the ashcroft/omega ones easily meet our requirements >>> and we can move to a bigger pressure drop to improve accuracy. I also like >>> this because the sensors won't be 1-offs and potentially could be recycled >>> into other projects. Bert and/or Jacob, was there a sensor you liked for >>> LFETS applications? If so can you send me a link to the spec sheet? >>> --An alternate option is to relax either our range of flow rates or >>> measurement accuracy requirements. Thoughts about this Kristin? >>> >>> >>> Ad astra, >>> Erin Schmidt >>> >>> On Sun, Nov 26, 2017 at 10:10 PM, Kristin Travis < >>> [email protected]> wrote: >>> >>>> dP presure transducers get pretty expensive if you go above 250 psi. >>>> Maybe a flowmeter costs less than the orifice + the dP transducer + the >>>> fittings and tubes for the dP transducer? Or if we drill out the orifice to >>>> have a larger hole, can we drop the dP below 250psi (assuming it's 250 psi >>>> dP across the transducer)? >>>> >>>> Let's go over this on Tuesday >>>> >>>> On Thu, Nov 23, 2017 at 11:59 AM, Musil Mark <[email protected]> >>>> wrote: >>>> >>>>> Ok, I will await your modified order. >>>>> >>>>> On Nov 23, 2017 11:27, "Erin Schmidt" <[email protected]> wrote: >>>>> >>>>>> The dp treasurer will not work for the range of flow rates required >>>>>> (either the pressure is too high for the sensor, or the measurement >>>>>> error>50%). Let's respec it. >>>>>> >>>>>> On Nov 22, 2017 7:14 PM, "Mark Musil" <[email protected]> wrote: >>>>>> >>>>>>> The current purchase order is attached. Nothing has been ordered. >>>>>>> Let me know what needs changed. >>>>>>> >>>>>>> On Nov 22, 2017 5:04 PM, "Kristin Travis" <[email protected]> >>>>>>> wrote: >>>>>>> >>>>>>>> Hi Erin, >>>>>>>> >>>>>>>> The dP transducer we spec-ed is this https://www.omega.com/pre >>>>>>>> ssure/pdf/PX26.pdf >>>>>>>> >>>>>>>> I cc'd Mark Musil, did you order this yet Mark? >>>>>>>> >>>>>>>> Thanks, >>>>>>>> Kristin >>>>>>>> >>>>>>>> >>>>>>>> On Wed, Nov 22, 2017 at 4:34 PM, Erin Schmidt <[email protected]> >>>>>>>> wrote: >>>>>>>> >>>>>>>>> BTW have you guys ordered any of the 'general purpose' pressure >>>>>>>>> transducers yet? I'd like to have a look at the spec. sheet. >>>>>>>>> >>>>>>>>> Ad astra, >>>>>>>>> Erin Schmidt >>>>>>>>> >>>>>>>>> On Tue, Nov 21, 2017 at 10:13 PM, Erin Schmidt <[email protected]> >>>>>>>>> wrote: >>>>>>>>> >>>>>>>>>> Guys, >>>>>>>>>> I want your feedback on this orifice: Brass, 2712T47, 0.047" >>>>>>>>>> diameter, 1/2"X1/2" NPT ($24.69) >>>>>>>>>> *https://www.mcmaster.com/#2712t47/=1ad0hiu >>>>>>>>>> <https://www.mcmaster.com/#2712t47/=1ad0hiu>* >>>>>>>>>> >>>>>>>>>> Gets us a 30 psi drop at the low end of our flow range (still not >>>>>>>>>> sure if 30 psi is too much for flow measurement accuracy, the >>>>>>>>>> corresponding >>>>>>>>>> drop will be 120 psi @ 2 lb/s and 260 psi @ 3 lb/s😑). This implies >>>>>>>>>> we >>>>>>>>>> need a maximum tank pressure of around 344 psi. If we go up to a >>>>>>>>>> 0.063" >>>>>>>>>> diameter the range is a bit more reasonable (10, 35, 80 psi @ 1, 2, 3 >>>>>>>>>> lb/s). Have we had any luck speccing the delta-p transducer yet? >>>>>>>>>> Knowing >>>>>>>>>> the accuracy of the measurement will help us make a more informed >>>>>>>>>> decision >>>>>>>>>> about the orifice... >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> Ad astra, >>>>>>>>>> Erin Schmidt >>>>>>>>>> >>>>>>>>>> On Tue, Nov 14, 2017 at 10:43 PM, Erin Schmidt <[email protected]> >>>>>>>>>> wrote: >>>>>>>>>> >>>>>>>>>>> https://neutrium.net/fluid_flow/discharge-coefficient-for-no >>>>>>>>>>> zzles-and-orifices/ >>>>>>>>>>> >>>>>>>>>>> Ad astra, >>>>>>>>>>> Erin Schmidt >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>> >>>>>>>> >>>> >>> >>> _______________________________________________ >>> psas-airframe mailing list >>> [email protected] >>> http://lists.psas.pdx.edu/mailman/listinfo/psas-airframe >>> >>> >> _______________________________________________ >> psas-airframe mailing list >> [email protected] >> http://lists.psas.pdx.edu/mailman/listinfo/psas-airframe >> >> >>
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