1 Kootenay Canal Flow Rate Measurement Comparison Test Using Intake Methods

Despite the fact that Kaplan-type turbines with short, converging intakes are in widespread use, neither of the two test codes most commonly used in North America [1, 2] provide a practical method for measuring flow rate in this type of unit. Code-accepted flow rate measurement methods generally require relatively long sections of uniform penstock or a well-formed bellmouth inlet, which rarely exist with low-head Kaplan units. This paper describes the execution and results of an ASME and CEATI-sponsored test comparing methods for flow rate measurement suitable for use in the short converging intakes which are typical of low-head hydro plants. Three flow rate measurement technologies were evaluated – acoustic transit time, current meters, and acoustic scintillation. The former was installed in a non-uniform transition section, and the latter two in an intake gate slot. An existing code-accepted acoustic flowmeter in the penstock served as a “reference” measurement. The test was executed at the level of accuracy required for turbine acceptance testing, generally in accordance with ASME PTC 18 [1]. Furthermore it was conducted “blindly”, meaning the flow rate data was not shared among test participants during testing. The testing is described and the results of the comparison measurements are presented, including a statistical analysis that compares the intake method flow rate measurements with the reference meter at the 95 % confidence level. A comparison is also made with the results of flow rate comparison tests sponsored by EPRI at Kootenay Canal in 1983 [3]. That test included only methodologies inside the penstock, including acoustic transit time, current meter, salt velocity, pressure time, and dye dilution. Because the same acoustic transit time flowmeter section was used for both tests, the results for all methods are directly comparable. In addition to the intake flow rate measurement methods, a CFD model of the intake flow field was implemented, and comparison of the CFD model with the field measurements is briefly discussed