Numerical Analysis of Contra-Rotating Small Hydro-Turbine with Cylinder Spoke

Abstract

Small hydropower is one of potential energy resource existing in our living environment and yet not been widely used. Small hydro-turbine is suitable in these energy resources while it still has some shortages, like performing low efficiency and easy to be out of control when there are foreign materials in the water. Thus we designed this contrarotating small hydro-turbine to increase its efficiency and enhance its ability of keeping stable operation. The experimental apparatus was designed and assembled, and some experiments were conducted. A new kind of cylinder spoke, which supports the front and rear rotor, was adopted and the numerical analysis was carried out in this paper. As the numerical analysis results shown, the efficiency of test turbine with cylinder spoke increased in a wide range of flow rate. The maximum efficiency increased about 2.2%, reaching to 66.4%, and it was obtained at 1.25Qd. The internal flow condition, especially at the areas behind the spoke, was improved by the cylinder spoke.

Pressure fluctuation on casing wall and investigation to tip leakage flow of contra-rotating small hydro-turbine

“…The detailed parameters of original model and new model are described in the previous research. 19 The differences between the original model and new model mainly focus on the blade thickness and shape of front rotor. The differences of front rotor between original model and new model are shown in Figure 2.…”

“…To decrease the blade thickness of new model, a parameter named blockage ratio is defined, and the blockage ratio is set to be constant to make the blade thinner. 19 For the shape of front rotor, two modifications are conducted. First, the length of front rotor increased for 16 mm.…”

“…The detailed parameters of original model and new model are described in the previous research. 19 The differences between the original model and new model mainly focus on the blade thickness and shape of front rotor. The differences of front rotor between original model and new model are shown in Figure 2.

Figure 1.3D models of original model and new model, (a)original model (b)new model.

Figure 2.Differences of front rotor between original model and new model.

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“…16,17 The performance and internal flow condition of original model was highly improved because of the changing of spoke. 18,19 The passing experiment of foreign vegetable materials was also conducted. 20 In order to further enhance the performance of contra-rotating small hydro-turbine, the blade thickness and shape of front rotor were changed to design the new model.…”

Investigation and Analysis of Attack Angle and Rear Flow Condition of Contra-Rotating Small Hydro-Turbine

“…After that, we continued to change the spoke from conical to cylindrical, and perform numerical analyses. The simulation result shows that the performance and internal flow conditions are further improved [20]. To clarify the running stability, we performed foreign materials experiments to evaluate performance when foreign vegetable materials become attached to the blade [21].…”