Determination of Discharge Coefficients of Sonic Nozzles Obtaining Low Uncertainty without Knowledge of Throat Diameter |
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| Bodo Mickan, Rainer Kramer, Petra Kiesewetter, Dietrich Dopheide |
- Abstract:
- The paper presents a new approach for the determination of discharge coefficients of sonic nozzles. Innovating the conventional way, where the knowledge of throat diameter is always necessary, the new approach utilises a special mathematical characteristic of the equation cD = a +b·Re-0.5 to figure out a relationship of the parameter b as a function of the parameter a and to define a new parameter β with b =f(a,β).
It is shown in the paper by theory as well as by experimental results, that the parameter β can be determined only from measurements of flow rate and gas parameters without any knowledge about throat diameter.
With parameter a as a parameter which is very well known with low uncertainty from past research and theoretical studies, the discharge coefficient cD = a +b·Re-0.5 = a + f(a, β)·Re-0.5 can be determined now also for very small nozzles down to a Reynolds number Re = 1000 (throat diameter roughly 0.1 mm) with a very low uncertainty.
Additional to this, it is shown based on measurements of more than 300 nozzles, that the new parameter β is related to the inner geometry of the nozzle and a sensitive indicator of the quality of manufacturing and/or the measurements. - Download:
- IMEKO-TC9-2004-040.pdf
- DOI:
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