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| Numerical simulation of braking transient process for hydraulic turbine |
| Jiao Lei, Zhang Pengpeng, Liu Jintao, Yin Junlian, Wang Leqin |
| Institute of Process Equipment, Zhejiang University, Hangzhou, Zhejiang 310027, China |
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Abstract In order to study the braking performance of hydraulic turbine in a hydraulic braking system in shut-down process, a CFD computational model of a hydraulic turbine was established, and the SST k-ω turbulence model was used to simulate the process. The different operating points in the braking process were selected and the process was simulated by the quasi-steady and transient computational methods, respectively; then the various CFD results were compared. The results showed that the strea-mlines in blade to blade surfaces obtained by the two methods are similar basically, and there is no noted reverse flow structure, but the braking torque is quite different between both methods in the initial phase of braking process. For the transient method, however, a stall phenomenon appears when the turbine operating speed is reduced to below 2 000 r/min; further, with decreasing speed, the stall becomes more and more dominated. Importantly, the static pressure in the turbine obtained with the transient method is significantly higher than that with the quasi-steady one, suggesting the hydraulic losses in the turbine given by the former method are larger than those by the latter.
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Received: 17 May 2012
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