| 1. |
- Baidar, Binaya, et al.
(författare)
-
Numerical study of the Winter-Kennedy method for relative transient flow rate measurement
- 2019
-
Ingår i: IOP Conference Series. - : Institute of Physics (IOP). - 1755-1307 .- 1755-1315. ; 405:1
-
Tidskriftsartikel (refereegranskat)abstract
- The Winter-Kennedy (WK) method is used to estimate relative flow rate using the differential pressure between two taps located at a radial section of a spiral casing (SC). It is widely used in index testing, for double regulated turbines optimization and sometimes for continuous discharge measurement in low head plants. This paper explores the possibility of using the WK method for relative transient flow rate measurements. A numerical model of a Kaplan model turbine from the penstock to the distributor has been developed. Unsteady RANS simulations with k-ω SST turbulence model are performed. Previously conducted experiments on the model turbine are used to validate the numerical results. In the simulations, the guide vanes (GVs) are closed from 26.5°, the best efficient point (BEP), to about 5° opening angle. Two azimuthal locations of the SC and four different WK configurations at each location are considered. The variation of the WK coefficients with time are investigated and compared to the ones at several stationary GV angles. The results showed a difference between the WK coefficients obtained at transient and stationary operations. However, there may be a possibility of using the WK method during transients by locating the pressure taps in appropriate locations for an acceptable variation of the WK coefficient from its BEP value.The research has been funded by Swedish Hydropower Centre (SVC).
|
|
| 2. |
- Baidar, Binaya, et al.
(författare)
-
Sensitivity of the Winter-Kennedy method to different guide vane openings on an axial machine
- 2019
-
Ingår i: Flow Measurement and Instrumentation. - : Elsevier. - 0955-5986 .- 1873-6998. ; 68
-
Tidskriftsartikel (refereegranskat)abstract
- This work studies the effects of guide vane openings (GVOs) on the Winter-Kennedy (WK) flow measurement method using CFD. The dependence of the WK coefficient with GVOs and its physical mechanism are presented. Although the WK method is reported to be sensitive to different factors including GVO, it is still unclear to which extent the GVO can be changed without modifying the WK coefficient significantly and the mechanism leading to such modification, if any. A numerical model of a Kaplan model turbine with a semi-spiral casing is developed and used to such purpose. Previously conducted experiments on the model turbine are used to validate the numerical results. The magnitude and behavior of the secondary flow are investigated together with the WK coefficients. The GVO is found to have an impact on the WK method, and the impact increases with the GVOs as the flow structure change. A suitable location to minimize the impact of the GVO is suggested. Furthermore, the theoretical WK constant with a suitable location and configuration are also presented; this can be useful in the absence of the measured WK coefficient.
|
|
| 3. |
- Baidar, Binaya, et al.
(författare)
-
Sensitivity of the Winter-Kennedy method to inlet and runner blade angle change on a Kaplan turbine
- 2019
-
Ingår i: IOP Conference Series. - : Institute of Physics (IOP).
-
Konferensbidrag (refereegranskat)abstract
- The Winter-Kennedy (WK) method is a widely used index testing approach, which provides a relative or index value of the discharge that can allow to determine the on-cam relationship between blade and guide vane angles for Kaplan turbines. However, some discrepancies were noticed in previous studies using the WK approach. In this paper, a numerical model of a Kaplan model turbine is used to study the effects of upstream and downstream flow conditions on the WK coefficients. Experiment on the model turbine is used to validate unsteady CFD calculations. The CFD results show that the inflow condition affects the pressure distribution inside the spiral case and hence the WK results. The WK coefficients fluctuate with high amplitude - suggesting to use a larger sampling time for on-site measurement as well. The study also concludes that to limit the impact of a change in runner blade angle on the coefficients, the more suitable WK locations are at the beginning of the spiral case with the inner pressure tap placed between stay vanes on the top wall.
|
|
