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Usually the total gap is approximately 0.002 of the seal ring diameter. If Dw = 200 mm, the total gap is 0.40 mm. When installed, the seal ring will not be too painful. Otherwise, the leak will be added. In addition, the amount of leakage can be reduced by adding seal ring resistance. The primary method of adding resistance is to make the seal ring into a labyrinth, zigzag shape, etc. This also adds the seal length of the seal ring and increases the resistance along the way. Leakage of the seal ring can, in some cases, lead to disturbances in the impeller inlet, Atlantic pump industry, and it is therefore necessary to rationally plan the seal ring approach.
Second, the balance of tissue loss is lost? In many fire pumps, there are organizations that balance axial thrust: balance holes, balance tubes, balance plates, and so on. Because there is a pressure difference between the two sides of the equilibrium tissue, there is also a leak of some liquid from the high pressure area to the low pressure area. Atlantic pumps learned that the leakage of the balance hole caused the fire pump's power to drop by 5%. In the balance plate organization, the leakage amount accounts for 3% of the operating flow, but the high pressure pump is somewhat larger than this value; in order to reduce the leakage loss, the diameter D of the balance plate can be reduced without affecting the balance force.
Third, the leakage between stages is lost? In a multi-stage pump of the volute type, the pressure on both sides of the interval plate is not equal, so there is also leakage loss. According to the different situation of the organization, the pressure difference between the two sides of the stage plate may be one, two or three levels. The more the number difference is, the more severe the leakage between the separators is. Therefore, step-type interstage sealing is widely used here. ? In addition, in the sectional multi-stage pump, there is also leakage between stages.
However, this is not the same as the above-mentioned inter-stage leakage, as some of the leaked liquid does not pass through the impeller, so it is not lost in the volume. Here, the pressure difference before and after the stage spacer is caused by the diffuser effect of the guide vane diffused and the suction effect of the impeller side clearance (equivalent to a centrifugal impeller). Under the effect of differential pressure, the leaking liquid enters the gap of the front stage impeller along the gap of the stage spacer plate, passes through the guide vanes, and the counter guide vanes (intake guide vanes) flow back to the gap between stages, repeating the above process. Although the inter-stage leakage of a segmented multi-stage pump is not a loss of volume, it is so reciprocating that it consumes the power of a fire pump.
Atlantic Pumps also learned that the passage of some of the liquid through the guide vane causes the effective section of the guide vane throat to decrease (that is, the leaked liquid takes up some of the cross section), so it will add flow rate here, resulting in additional hydraulic force. Lost. According to the book "Fundamentals of Fire Pump Planning," a multi-stage pump was used. At a flow rate of 20 l/s, the inter-stage clearance was reduced from 0.75 mm to 0.25 mm, and the inter-stage leakage q was reduced by 0.7 l/s. Because of the reduction in q, the flow through the guide vanes is reduced, the flow rate in the guide vane throat is reduced, the hydraulic loss in the guide vane is reduced, and the relative velocity of the liquid in the gap between the impeller and vane is reduced due to q reduction. Reduced, and then also cut the loss of impeller disc conflict, so the pump power has improved by 5%.
First, the leakage of the seal ring is lost. At the inlet of the impeller, there is a seal ring. When the fire pump is in operation, because there is a pressure difference between the two sides of the seal ring, one side is approximately the impeller outlet pressure, and the other side is the impeller inlet pressure, so there will always be a Some liquid leaks from the impeller outlet to the impeller inlet. Some of this liquid gains energy in the impeller, but the liquid is not sent out. This reduces the amount of water supplied by the fire pump. The energy of the leaking liquid is used to overcome the resistance of the seal ring. ? Obviously, the larger the seal ring diameter Dw, the greater the pressure difference between the two sides, the greater the leakage. With regard to the stereotyped fire pump, in order to reduce the amount of leakage and improve the power of the fire pump, the gap of the seal ring should be reduced as promised.