Blow-Down Tests Confirm Accurate Critical Flow Venturi Measurements During Transients

Published

August 14, 2009

Author(s)

John D. Wright

Abstract

Critical flow venturis (CFVs) can be used to measure flow under transient pressure, temperature, and flow conditions with k=2 uncertainties of 0.4 % or less. Blow-down tests transferred 630 g of nitrogen during a 100 s interval from an unregulated cylinder (initially at 10 MPa) through a CFV into a known collection volume. Fast pressure and temperature sensors monitored the inlet to the CFV. The integrated CFV mass flows,  , averaged 0.38 % smaller than the mass V of the collected gas. To reduce temperature transients at the CFV, a heat exchanger was added upstream of it. The heat exchanger reduced the percentage difference 100( /(V)  1) to 0.04 %. Accurate measurements of transient flows require careful measurements of the gas temperature near the throat of the CFV and careful attention to thermal effects on the CFV discharge coefficient. We conclude that a properly instrumented critical nozzle can be used as a flow reference to evaluate the performance of other flowmeter types exposed to transient conditions

Proceedings Title

Proceedings of the International Symposium for Fluid Flow Measurement

Conference Dates

August 12-14, 2009

Conference Location

Anchorage, AK

Pub Type

Conferences

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Keywords

blow-down, critical flow venturi, critical nozzle, flow, fueling, transient, vehicle

Citation

Wright, J. (2009), Blow-Down Tests Confirm Accurate Critical Flow Venturi Measurements During Transients, Proceedings of the International Symposium for Fluid Flow Measurement, Anchorage, AK, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=903281 (Accessed December 26, 2024)