Influence of geometric parameters of pipe narrowing on pressure losses in a pressure short pipelin

Pipelines with contraction are used in water supply, sewage, ventilation, energy, and other fields. In general, for an open-type pressure hydraulic system with a liquid flow rate Q = const, the pressure regulation characteristic, with and without measures necessary to change energy losses in the pipeline of the pressure hydraulic system, depends on the hydraulic resistance of the liquid in the regulated and unregulated sections of the pipeline. There was considered a short pipeline in which water flows without changes in properties, without affecting its unregulated section. The regulated section represented a segment of the pipe contraction. In this case, the reduction in cross-sectional area could be in the form of a gradual contraction (converging nozzle) or a pipe sudden contraction. The regulation function includes the relationship of pressure loss coefficients for these local hydraulic resistances. Moreover, the first was considered using measures necessary to change energy losses in the pipeline of the pressure hydraulic system, while the second was considered without them. The formula for calculating the pressure loss coefficient structurally reflects only the change in the geometry of the pipe. For the first case, the correction factor is variable and depends on the cone angle of the converging nozzle and the length of the converging section. However, the pressure coefficient for the first case is always less than that for the second. Negative values of the regulation function indicate a reduction in pressure losses at the pipeline contraction when using the aforementioned measures, while positive values indicate an increase in pressure losses. It has been shown that changes in the geometric parameters of the contraction section of the pressure pipeline in a pressure hydraulic system affect head losses both in the pipeline and, overall, throughout the entire system.