Investigation on the Effect of Impeller Design Parameters on Performance of a Low Specific Speed Centrifugal Pump Using Taguchi Optimization Method

In order to investigate the effect of blade design on pump performance, a CFD analysis was carried out, and the results were compared with experimental performance data of a low specific speed radial pump, which presents a good agreement. After model verification, the effect of impeller geometrical parameters includes blade outlet angle, wrap angle, and width at the exit, was investigated on the pump’s performance. Moreover, these parameters were chosen on three levels using an L9 orthogonal standard array of the Taguchi optimization method. The efficient levels of variables were calculated using the analysis of variance (ANOVA) method. The results revealed that impeller width at exit and blade outlet angle is the most effective pump shaft power and efficiency parameters. To minimize power, the optimal levels are the outlet angle of 27∘∘, wrap angle of 150∘∘, and width at the exit of 9 mm. Further, an outlet angle of 23∘∘, a wrap angle of 155∘∘, and a width at the exit of 9 mm lead to maximum pump efficiency. According to the validation simulations, an increase of 2.4% inefficiency and a minimum power of 3.9KW were achieved. The Overall Evaluation Criteria (OEC) technique revealed that considering 23∘∘, 160∘∘, and 9 mm for outlet angle, wrap angle, and width at the exit, minimum shaft power, and maximum pump efficiency will be achieved. ANOVA introduced width at the exit as the most governing parameter of pump performance characteristics.

Performance Prediction and Geometry Optimization for Application of Pump as Turbine: A Review

Pump as Turbine (PAT) is a technically and economically effective technology to utilize small/mini/micro/pico hydropower, especially in rural areas. There are two main subjects that influence the selection and application of PAT. On the one hand, manufacturers of pumps will not provide their characteristics under the turbine mode, which requires performance prediction methods. On the other hand, PAT efficiency is always slightly lower than that of pump, which requires further geometry optimization. This literature review summarized published research studies related to performance prediction and geometry optimization, aimed at guiding for selection and optimization of PAT. Currently, there exist four categories of performance prediction methods, namely, using BEP (Best Efficiency Point), using specific speed, loss modeling, and polynomial fitting. The using BEP and loss modeling methods are based on theoretical analysis, while using specific speed and polynomial fitting methods require statistical fitting. The prediction errors of published methods are within ±10% mostly. For geometry optimization, investigations mainly focus on impeller diameter and blade geometry. The influence of impeller trimming, blade rounding, blade wrap angle, blade profile, blade number, blade trailing edge position, and guide vane number has been studied. Among published methods, the blade rounding and forward-curved impellers are the most effective and feasible techniques.

A New Prediction Method for the Complete Characteristic Curves of Centrifugal Pumps

Complete pump characteristics (CPCs) are the key for establishing pump boundary conditions and simulating hydraulic transients. However, they are not normally available from manufacturers, making pump station design difficult to carry out. To solve this issue, a novel method considering the inherent operating characteristics of the centrifugal pump is therefore proposed to predict the CPCs. First, depending on the Euler equations and the velocity triangles at the pump impeller, a mathematical model describing the complete characteristics of a centrifugal pump is deduced. Then, based on multiple measured CPCs, the nonlinear functional relationship between the characteristic parameters of the characteristic operating points (COPs) and the specific speed is established. Finally, by combining the mathematical model with the nonlinear relationship, the CPCs for a given specific speed are successfully predicted. A case study shows that the predicted CPCs are basically consistent with the measured data, showing a high prediction accuracy. For a pump-failure water hammer, the simulated results using the predicted CPCs are close to that using the measured data with a small deviation. This method is easy to program and the prediction accuracy meets the requirements for hydraulic transient simulations, providing important data support for engineering design.

Dynamic Stall Inception and Evolution Process Measured by High-Frequency PIV System in Low Specific Speed Impeller

Stall in centrifugal pumps is a complicated flow phenomenon, which is detrimental to the pumps' safety and stable operation. Using a high-frequency PIV system (f=10k Hz) and a bench-scale refractive index matching experimental setup, two measurement methods are introduced to observe the dynamic stall inception and evolution. In the first method, the flow rate was continuously reduced at an interval of 0.005Qd and the experiment was carried out under stable flow rate condition. It shows the flow adjacent to the blade suction side gradually evolved from the flow separation into a broken vortex. The stall vortex moved toward the impeller's inlet and continuously grew, and resulted in significant changes in the main flow direction at the channel inlet. The formation and development of the other vortex structures in channel were closely related to the stall vortex at the inlet. The second method is the dynamic flow rate measurement and the results show that the stall is not caused by the increase in the relative inflow angle. It was obtained that the velocity value in the stall channel near the suction side rapidly decreased; however in the non-stall channel, the velocity value increased at the channel inlet. By analyzing the velocity distribution in both flow channels before and after the stall, the mechanism of alternating stall is well explained. Meanwhile, it was obtained that the stall was more likely to originate from the flow separation near the blade suction side for low specific speed impeller

Analysis, Design and Validation of a Vaned Diffuser for Improved Fish Friendliness

The primary cause of mechanical-related fish injury and mortality in turbomachinery is blade strike. Fish contained in the flow may strike with the rotor blades and the fixed diffuser vanes, the latter being a non-negligible factor causing fish damage in pump system. In this study, an experiment-based correlation of fish mutilation ratio acts as critical strike velocity. The relation between strike damage in a vaned diffuser and the theoretical pump head is presented as a function of specific speed. As an example, a vaned diffuser is designed for a single-bladed, mixed-flow impeller with the purpose of improving fish friendliness. This pump can be scaled to operate with a head up to 14 m at peak efficiency, without fish damage in the diffuser. Subsequently, experiments are conducted to show the retained pump performance as well as the great improvement of fish friendliness.

Four-quadrant Characterization of Hydrodynamic Phenomena in a Low Specific Speed Centrifugal Pump

Objective: Identify and characterize subsynchronous hydrodynamics phenomena in a low specific speed centrifugal pump based on its four-quadrant characteristic curve. Materials: A 1.5 HP ITT Goulds pump instrumented with pressure transductors, an accelerometer, a torque sensor and a tachometer. Flow rate measurement was done with an ultrasonic transit time clamp-on flow meter. Methods: Time and frequency domain analysis with phase analysis were used to identify spectral components linked to hydrodynamic phenomena such as rotating stall and surge. Results and discussion: This work approaches an alternative method to calculate the phase angle using pressure signals without filtering. Related with hydrodynamic phenomena, the evidence collected suggests the presence of rotating stall in some operation points of the four-quadrant characteristic curve. Furthermore, in the third quadrant, rotating stall coexist with surge. Conclusions: The instrumentation and methods regarded in this work allow to collect evidence to identify in-phase and out of phase subsynchronous hydrodynamic phenomena. The classic cross-correlation-based method was improved to ease the diagnosis of subsynchronous phenomena by visual inspection. A new quantitative approach was introduced to detect subsynchronous phenomena, based on the Fourier analysis; it was validated with a case study for which the classical method was not suitable.

Sliding behavior of silica ball-shale rock contact under polyacrylamide aqueous solutions

The tribological properties of proppant particle sliding on shale rock determine the shale gas production. This work focuses on investigating the impacts of sliding speed on the coefficient of friction (COF) and wear of the silica ball-shale rock contact, which was lubricated by water or different types of polyacrylamide (PAM) aqueous or brine solution. The experimental results show that both boundary and mixed lubrication occur under specific speed and normal load. COF and wear depth of shale rock under water are higher than those under PAM solution due to superior lubrication of PAM. COF of shale rock under PAM brine solution increases and the wear of the rock is more serious, attributed to the corrosion of shale rock and adverse effect on lubrication of PAM by brine.

OPTIMIZATION OF PARAMETERS OF FAN UNITS OF AIR COOLING DEVICES

Purpose of the study. Optimization of the parameters of high speed fan units of air coolers, the combination of which achieves the highest economic efficiency of fan units and, accordingly, the most rational range of specific speed values for the modes of maximum efficiency of fan units in combination with the relative diameter of the sleeve. Development of a mathematical model for determining the local values of the parameters of the efficiency of highspeed fan installations. Sustainable development of territories with active subsoil use is closely related to solving the problems of improving industrial safety and the efficiency of cooling the compressed gas at compressor stations of main gas pipelines, which actualizes the problem of mathematical modeling of energy conversion processes in the impellers of fan units of gas air coolers (AVO) to increase the competitiveness of the oil and gas complex RF in the context of globalization. Research methods. To optimize and determine the limiting combination of calculated parameters, the mathematical method of searching for the area of local maxima of a multiparameter problem in this part was performed in two stages: a mathematical model was built for determining the local values of the parameters that ensure the highest efficiency of fan installations with high speed; the most rational limiting combination of design parameters was determined, at which the highest economic efficiency of fan installations is achieved. Research results. The possibility of increasing the economic efficiency of axial fan units of high speed, made according to aerodynamic schemes with one impeller for gas air cooling devices, has been established. Using the mathematical analysis of the basic laws of axial turbomachines, equations for the efficiency of a fan unit and a fan are obtained, depending on the specific speed. Formulas are obtained for the maximum values of the efficiency of the fan and the fan unit of various specific speed depending on the coefficient of the consumpconsumption speed and on the relative diameter of the impeller sleeve. A method is proposed for constructing aerodynamic schemes of axial fan units for air-cooled gas coolers of the "K" type with maximum maximum values of efficiency for given values of specific speed, relative diameter of the impeller sleeve, aerodynamic quality of the impeller profiles, coefficient of aerodynamic resistance of the flow path of the coefficient of flow velocity. The possibility of creating a fan installation with a speed of ny ≥ 400 with an efficiency of at least ηy=0,86. Application area. Enterprises of the oil and gas complex of the Russian Federation for cooling compressed gas using AVO compressor stations of main gas pipelines.