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Axial Flow Pumps
Published in Getu Hailu, Michal Varchola, Peter Hlbocan, Design of Hydrodynamic Machines, 2022
Getu Hailu, Michal Varchola, Peter Hlbocan
Flow separations in the impeller of an axial flow pump may occur when operating at part load due to a rise in the incidence angle at the impeller leading edge, most likely resulting in head curve instability. The unstable region is shown in Figure 4.21. If the pump is operated within the unstable operation region, there will be vibration and noises. Researchers have also reported that the power consumption can surpass the rated brake power highly (Figure 4.20b). Therefore, it is advised that axial pumps be started with the delivery valve fully open.
Turbomachinery
Published in William S. Janna, Introduction to Fluid Mechanics, Sixth Edition, 2020
The next turbomachine that we will discuss is the axial-flow pump. In this case, the fluid medium is an incompressible fluid, and temperature changes are not as significant as pressure changes. Consequently, the descriptive equations can be written using static pressures. Figure 9.19 shows one design of an axial-flow pump. At the inlet or suction side are placed straightener vanes to ensure that the flow into the pump is purely axial. The impeller is made up of a hub and blades that act much like a propeller, adding energy to the liquid. The outlet guide vanes have the function of removing any tangential velocity component the liquid might have. The outflow is thus purely axial. The axial-flow pump has a high capacity and corresponding low head output.
Rocket Engines
Published in Ahmed F. El-Sayed, Aircraft Propulsion and Gas Turbine Engines, 2017
Axial types become competitive to centrifugal ones when multistaging or maximum efficiency is of paramount consideration [8]. This design is well suited to liquid hydrogen service, which entails the problems of extremely low fluid temperature and density. Low fluid density results in high-volume flow and in high-pressure head-rise requirements. For such applications, a multistage axial flow pump is generally superior with respect to construction and performance. Elements of an axial flow pump are shown in Figure 19.15. The rotor assembly consists of an inducer, a cylindrical rotor with multiple rows of rotating blades, and a rotor shaft. The stator assembly includes a cylindrical casing with rows of stationary blades spaced between the inducer and rotating blades, a volute casing, bearings, and seals. An inducer is placed at the pump inlet to supply the fluid to the main-pump section at the required pressure and velocity. The main function of the rotor blades is to accelerate the flow (or increase the kinetic energy of the fluid), while the stator blades, acting as diffusers, convert the velocity head of the fluid into a pressure head. The axial speed of flow is kept constant throughout the various stages of the pump.
Experimental investigation and one-dimensional (1D) dynamic modelling of steady flow through a levee breach
Published in Journal of Hydraulic Research, 2022
Ibrahim Adil Ibrahim Al-Hafidh, Ezzat Elalfy, Jasim Imran
The downstream water depth was adjusted using a calibrated sharp-crested weir. Seven different weir heights, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13 and 0.14 m, were used to control downstream water depth. Four breach widths, 0.7, 0.6, 0.5, and 0.4 m, were used in these experiments. The set-up was constructed on a 0.3-m-high raised platform from the laboratory floor to allow a free fall from the floodplain. Water was supplied to the main channel by an axial flow pump. Constant discharge of 0.075 m s was used. The discharge was monitored using an in-line Krohne electromagnetic flowmeter (measurement error less than 0.5%). A honeycomb made of short pipe sections, flow straighteners, and a wave suppressor were used at the inlet of the main channel to reduce turbulence and water surface fluctuation. The flow was allowed to achieve a steady-state condition before the measurement was commenced. The downstream discharge was estimated from the sharp-crested weir equation, , obtained by performing calibration experiments. Here Q is the flow rate, B = 0.61 m is the crest width, is the discharge coefficient, h is the head above the crest, and n = 1.5 is the exponent. The breach discharge was calculated from the mass balance equation.
Influence of spiral flow on the hydraulic performance of a siphon outlet conduit in an axial flow pump system
Published in Journal of Hydraulic Research, 2022
Lei Xu, Bryan Karney, Wei Shi, Dongtao Ji, Bo Xu, Weigang Lu
Axial flow pumping stations working with relatively low operational heads are widely applied in hydraulic systems. Applications often involve large flows and low heads, such as associated with water diversion projects, environmental management and improvement projects, flood control applications as well as irrigation and drainage projects. A recent example is the “Eastern Route Project of South to North Water Diversion” in China, which includes 21 large pumping stations leading to considerable power consumption with a total power requirement in this case of over 220 MW. Many other low-head water transfer projects can be found in the Philippines, Sudan, the Netherlands and the USA. At the heart of such projects is an axial flow pump system, and it is obviously crucial for the pump system to operate safely, stably and efficiently.
Study on the characteristics of horn-like vortices in an axial flow pump impeller under off-design conditions
Published in Engineering Applications of Computational Fluid Mechanics, 2021
Haoru Zhao, Fujun Wang, Chaoyue Wang, Wenhao Chen, Zhifeng Yao, Xiaoyan Shi, Xiaoqin Li, Qiang Zhong
Figure 5 shows the experimental system of the axial flow pump. Under the condition of no cavitation, the energy characteristics and pressure fluctuation experiments were carried out on the test bench. The uncertainty of pressure transmitter (V15712-HD1A1D7D) is less than ±0.10%, the uncertainty of magnetic flowratemeter (LDG-500S) is less than ±0.20%, and the uncertainty of tacho-torquemeter (JCZL2-500) is less than ±0.10%, the uncertainty of pressure fluctuation signal sensor (HDP503) is less than ±0.25%. The diameter of the impeller D is 300 mm, the diameter of the hub Dh is 140 mm, the impeller blades number is 4, the guide vanes number is 7, the rated speed nr is 1450 rpm, the rated head H0 is 7.12 m, the rated flow Q0 is 335.38L/s, and the specific speed ns (nrQ00.5/H00.75) is about 193m0.75/s1.5. The experiments were carried out on a test bench that complies with the IEC-60193 standard.