Shanghai Huangpu River upstream water diversion project, the use of 12 large vertical Francis pump, the impeller are equipped with German KSB company made before the guide vane device (Inlet Vane Conttrol Device VR), the purpose is to achieve in the more Wide range of regulating pump performance. Pump structure as shown in Figure 1, the parameters are: flow Q = 6.5M3 / S, head H = 15.5M, speed n = 297rpm, the number of comparison ns = 353, efficiency η = 0.80, shaft power P = 1400KW. Pre-guide vane device (referred to as VR device) is currently not much use on the pump at home and abroad, in this regard, few technical information and reports. To this end, the author based on the past three years on the pump operating conditions and the relevant experimental data and technical information on the use of VR devices to adjust the performance of the pump to do some analysis and analysis of the reasons in order to have a more objective and correct understanding of VR devices , So as to put forward some suggestions for the actual control of such pumps. Second, the front guide vane device on the performance of the pump We use the VR device is circular, guide vane straight leaf type, a total of 17, leaf length 500mm, device diameter 1300mm, see Figure 2. The device is driven by a motor and transmits the torque to the input shaft of the device through a multi-section transmission rod with a universal joint. Then, the blades of the device are rotated synchronously through the gear system in the device to adjust the angle of the guide vanes. KSB company set to VR device guide vane perpendicular to the horizontal plane 90 º, when the blade rotation tilt direction and pump impeller rotation direction for the same angle (ie, the angle becomes smaller); when the blade tilt direction and pump impeller rotation direction opposite Increase angle (ie angle becomes larger). Below the first installment of the pump installed with no guide vane, the performance of the pump for some analysis. (A) Comparison of pump performance without front guide vane and front guide vane with blade angle of 90 ° According to the information provided by KSB Company and the relevant tests conducted by our researchers, And when the blade is at 90º, it is compared with the characteristic curve of the pump without front vane device, as shown in Fig.3. From the figure, we can draw conclusions: 1. The Q-H curve of the pump without front guide vane and front guide vane is basically two parallel curves with Q- -H curve slightly lower, which is due to the addition of the front guide vane, the import flow resistance loss caused by the increase of the head down reason. 2. From the Q-η curve shows that the two curves are basically close, and there is a coincidence point on the left of this point, there is a front guide vane Q-η curve than the front guide vane Q-η curve slightly higher 3 On the right side of this point, the Q-η curve of the front guide vane is slightly lower than the Q-η curve of the front guide vane. This coincidence point is the optimal operating point. This shows that in the best conditions, the front guide vane resistance loss is minimal for the pump, does not cause any impact; and in the small flow, due to influent pipe less flow, uneven flow, plus the front After the guide vane, since the diversion effect, so that the liquid flow inlet uniformity of enhancement, the resulting efficiency has improved than the original; and in the large flow, the role of diversion disappeared, on the contrary due to the increase of the guide vane, the resistance loss increases, Resulting in lower efficiency. It can be seen that when the vane position is at 90 º, the performance of the pump is basically similar to that of the pre-vane pump without any effect on the pump characteristics. Second, take a look at the guide vane at different angles when the pump performance changes. (B) of the VR device guide vane at different angles on the performance of the pump 1 on the Q-H performance curve Figure 4 is a VR device pump in a variety of guide vane angle performance curve. As can be seen in Figure 4, when the current guide vane is adjusted to less than 90, the resulting performance curve is clearly to the left and is substantially parallel to the performance curve at 90 degrees (in the continuous operating limit range Inside). This is because at this time, the flow direction of the front guide vane exit is consistent with the rotation direction of the impeller. The flow has a forward pre-rotation Vlu in front of the pump impeller inlet (Vlu flow at the impeller inlet at the circumferential speed of the absolute velocity ), So Vlu> 0 (front guide vane is 90º. When, Vlu = 0). From the Euler equation: HT = (u2v2u-ulvlu) / g that when the guide vane angle to less than 90º. When the direction is adjusted, because Vlu> 0, the theoretical lift of the pump HT is less than that of the guide vane. When the pump head HT. And, the smaller the value of the front vane angle, Vlu value is larger, the greater head lift, so Q-H characteristic curve to the left. In actual use, it is the use of this feature, while keeping the head is basically constant, the flow becomes smaller with the VR angle becomes smaller, so as to achieve the purpose of reducing the flow. However, when the current guide vane is adjusted to be greater than 90 °, the direction of the front guide vane flow outlet is opposite to that of the impeller, that is, reverse pre-rotation occurs, so that Vlu <0. The same Euler equation shows that at this time the pump head HT is greater than the front guide vane at 90º head. Furthermore, the larger the leading vane angle, the smaller the Vlu, the greater the lift of the pump, and the Q-H characteristic shifts to the right. Therefore, it is possible to increase the pump flow rate with the increase of the vane angle under a certain lift. Practice shows that the above effect is obvious.
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