Performance Study On The Perforated Plate Flowmeter Applied To Cryogenic Fluid

The perforated plate flowmeter inherits the advantage of standard orifice flowmeter, such as simplicity in design and the absence of moving parts, and it also occupies the merits of better flow balance, less turbulence, weaker dead flow effect and lower energy loss, leading to the promising application potential in the field of flow measurement, especially for cryogenic fluids. However, the geometric parameters of perforated plate, such as the total open area, hole diameter, numbers and hole distribution, have important influence on the performance of the perforated plate flowmeter. In order to investigate the characteristics of the perforated plate flowmeter when applied to cryogenic fluids, the present work will focus on the theoretical analysis, numerical simulation and experimental work of the multi-hole perforated plate flowmeters as follows:1. Theoretical analysis on the flow rate and pressure loss during throttling process The formula of flow rate and pressure loss, which based on the principle of standard orifice flowmeter, were deduced from the equation of continuity and Bernoulli Equation, with which the factors that have influence on the discharge coefficient C and the pressure loss coefficient ζ were analyzed. The results can offer the guide to numerical simulation and experimental investigation.2. Numerical simulation and performance analysis of the perforated plates Upon checking the grid independency and validating the numerical model, the influence of the fluid type and geometric parameters on the performance of a perforated plate has been numerically simulated by the realizable k-ε model and Schnerr-Sauer cavitation model with the help of Fluent. According to computed results, the analysis was devoted to the influence of the properties of liquid nitrogen, liquid oxygen, liquid hydrogen and water, and the geometric parameters, such as perforating form, the thickness, the equivalent diameter ratio and the hole diameter of perforated plate, on the discharge coefficient C, the pressure loss coefficient C and the ranges of Re for the stable operating region. The perforating form matching the turbulent velocity distribution in the circular tube was put forward, which can provide a preliminary basis for the optimizing design of the perforated plate.3. Experimental test on the perforated plates with liquid nitrogen as working fluid Based on the simulation results, the perforated plates have been experimentally tested. The results from the apparatus of DN25 show that a perforated plate with the perforating form matching the turbulent velocity distribution in the circular tube achieves better performance. The influences of the hole pitch and the introduced semicircle hole on the discharge coefficient C and the pressure loss coefficient C were also explored, further guiding the optimizing design of the perforated plate.