Influence Analysis of Runner Inlet Diameter of Hydraulic Turbine in Turbine Mode with Ultra-Low Specific Speed
Abstract
:1. Introduction
2. Theoretical Analysis
3. Computation Model
4. Numerical Calculation
4.1. Mesh Division
4.2. Boundary Conditions and Performance Parameter Calculation
4.3. Test Verification
5. Analysis of Calculation Results
5.1. External Characteristic
5.2. Internal Flow Pattern of the Runner
5.2.1. Pressure Distribution of Runner Blades
5.2.2. Internal Flow Field of the Runner
- (1)
- When D1 is small, there is a phenomenon of detachment at the blade front, and this is because the smaller D1, the greater the degree of blade bending. When water flows through the blade bending, detachment occurs, causing the direction of velocity to be inconsistent with the direction of the blade;
- (2)
- When D1 is large, the water flow velocity is relatively high in the middle of the blade with a large curvature at the back, which means the kinetic energy of the water flow is relatively high. According to the Bernoulli equation, the pressure energy at this location is relatively low, and even a low-pressure zone can be formed, as shown in Figure 10. Compared with the pressure distribution maps of the runner blades, the velocity and pressure are consistent, reflecting the movement of water in the flow channel and the changes in pressure energy and kinetic energy;
- (3)
- The larger the D1, the greater the inlet flow velocity of the runner, the greater the kinetic energy of the water, and the higher the H.
6. Conclusions
- (1)
- At the rated discharge, compared to D1 = 0.49 m, when D1 increases to 0.51 m, the efficiency only decreases by 1.48% and the head increases by 148.73 m, indicating a significant improvement in the ability of HTTM-ULSS to recover the water head;
- (2)
- The inlet diameter D1 of the runner is a key factor affecting HTTM-ULSS performance. The larger the D1, the lower the efficiency, the higher the water head, and the greater the output of the HTTM under rated operating conditions;
- (3)
- When D1 is large, the water head of a hydraulic turbine increases, but the increase in runner water head loss is very significant at large discharge, seriously affecting the efficiency of the hydraulic turbine to recover the water head. Therefore, the selection of runner diameter needs to consider whether the hydraulic turbine often operates under variable conditions;
- (4)
- As D1 increases, the fluid flow inside the runner becomes smoother, but the high-pressure area of the runner blades increases. To recover more pressure energy and maintain structural stability for the hydraulic turbine, further force analysis of the runner blades is needed to determine a reasonable D1.
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
Nomenclature
He | effective utilization water head |
Hr | design water head |
ω | angular velocity of the runner |
n | rotating speed of the runner |
g | gravitational acceleration |
C1 and C2 | water circulation at the inlet and outlet of the runner |
D1 | inlet diameter of the runner |
D2 | outlet diameter of the runner |
Z | number of the runner blades |
vu1 and vu2 | circumferential components of the absolute water flow velocity at the runner inlet and outlet |
u1 | circumferential speed at the runner inlet |
u2 | circumferential velocity at the runner outlet |
β1 | inlet angle of the runner blade |
β2 | outlet angle of the runner blade |
Qr | design discharge |
Q11 | unit discharge |
B | height of the runner inlet |
α2 | the outlet water flow angle |
ns | specific speed |
H | water head |
η | efficiency |
Pout | total pressure at the outlet of the draft tube |
P | output of the hydraulic turbine |
Q | working discharge |
A | inlet area of the volute |
Pin | total inlet pressure of the volute |
ρ | density of water |
M | shaft torque |
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Parameter | Value | Parameter | Value |
---|---|---|---|
β1 (°) | 140 | B (m) | 0.052 |
D2 (m) | 0.26 | n (r/min) | 1500 |
D1 (m) | 0.49, 0.5 and 0.51 | Qr (m3/s) | 0.8 |
D1/(m) | Qr (m3/s) | H/(m) | η/(%) | P/(kW) |
---|---|---|---|---|
0.49 | 0.88 | 392.14 | 68.10 | 2315.68 |
0.5 | 0.93 | 522.71 | 67.84 | 3105.95 |
0.51 | 0.99 | 540.87 | 66.62 | 3486.75 |
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Chen, J.; Zheng, Y.; Zhang, L.; Chen, X.; Liu, D.; Xiao, Z. Influence Analysis of Runner Inlet Diameter of Hydraulic Turbine in Turbine Mode with Ultra-Low Specific Speed. Energies 2023, 16, 7086. https://doi.org/10.3390/en16207086
Chen J, Zheng Y, Zhang L, Chen X, Liu D, Xiao Z. Influence Analysis of Runner Inlet Diameter of Hydraulic Turbine in Turbine Mode with Ultra-Low Specific Speed. Energies. 2023; 16(20):7086. https://doi.org/10.3390/en16207086
Chicago/Turabian StyleChen, Jinbao, Yang Zheng, Lihong Zhang, Xiaoyu Chen, Dong Liu, and Zhihuai Xiao. 2023. "Influence Analysis of Runner Inlet Diameter of Hydraulic Turbine in Turbine Mode with Ultra-Low Specific Speed" Energies 16, no. 20: 7086. https://doi.org/10.3390/en16207086