scholarly journals Numerical Study on the Influence of Step Casing on Cavitating Flows and Instabilities in Inducers with Equal and Varying Pitches

Processes ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1103
Author(s):  
Lu Yu ◽  
Haochen Zhang ◽  
Hui Chen ◽  
Zhigang Zuo ◽  
Shuhong Liu
Keyword(s):  
Flow Field ◽  
Optimization Design ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Cavitating Flow ◽  
Engineering Practice ◽  
Pressure Distributions ◽  
Significant Difference ◽  
Liquid Rocket ◽  
Safety And Stability

It is known that cavitating flow characteristics and instabilities in inducers can greatly impact the safety and stability of a liquid rocket. In this paper, step casing optimization design (Model OE and Model AE) was carried out for two three-bladed inducers with an equal (Model O) and a varying pitch (Model A), respectively. The unsteady cavitation flow field and accompanied instabilities were studied via numerical simulations. Reductions of the cavity size and fluctuation were observed in cases with a step casing. A significant difference in cavity structures was seen as well. Referring to the pressure distributions on the blades and details of the flow field, the mechanism of cavitation suppression was revealed. This work provides a feasible and convenient method in engineering practice for optimizing the characteristic of the cavitating flow field and instabilities for the inducer.

Experimental and Numerical Investigation of the Flow in a Low-Pressure Industrial Steam Turbine With Part-Span Connectors

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
Markus Häfele ◽  
Christoph Traxinger ◽  
Marius Grübel ◽  
Markus Schatz ◽  
Damian M. Vogt ◽  
...  
Keyword(s):  
Flow Field ◽  
Steam Turbine ◽  
Numerical Study ◽  
Three Dimensional ◽  
Low Pressure ◽  
Operating Conditions ◽  
Engineering Practice ◽  
Cfd Model ◽  
Wide Range ◽  
The Impact

An experimental and numerical study on the flow in a three-stage low-pressure (LP) industrial steam turbine is presented and analyzed. The investigated LP section features conical friction bolts in the last and a lacing wire in the penultimate rotor blade row. These part-span connectors (PSC) allow safe turbine operation over an extremely wide range and even in blade resonance condition. However, additional losses are generated which affect the performance of the turbine. In order to capture the impact of PSCs on the flow field, extensive measurements with pneumatic multihole probes in an industrial steam turbine test rig have been carried out. State-of-the-art three-dimensional computational fluid dynamics (CFD) applying a nonequilibrium steam (NES) model is used to examine the aerothermodynamic effects of PSCs on the wet steam flow. The vortex system in coupled LP steam turbine rotor blading is discussed in this paper. In order to validate the CFD model, a detailed comparison between measurement data and steady-state CFD results is performed for several operating conditions. The investigation shows that the applied one-passage CFD model is able to capture the three-dimensional flow field in LP steam turbine blading with PSC and the total pressure reduction due to the PSC with a generally good agreement to measured values and is therefore sufficient for engineering practice.

scholarly journals Recirculation Flow and Pressure Distributions in a Rayleigh Step Bearing

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
Feng Shen ◽  
Cheng-Jin Yan ◽  
Jian-Feng Dai ◽  
Zhao-Miao Liu
Keyword(s):  
Flow Field ◽  
Flow Characteristics ◽  
Lower Surface ◽  
Navier Stokes ◽  
Maximum Pressure ◽  
Slider Bearing ◽  
Navier Stokes Equation ◽  
Recirculation Flow ◽  
Lubrication Equation ◽  
Pressure Distributions

Flow characteristics in the Rayleigh step slider bearing with infinite width have been studied using both analytical and numerical methods. The conservation equations of mass and momentum were solved utilizing a finite volume approach and the whole flow field was simulated. More detailed information about the flow patterns and pressure distributions neglected by the Reynolds lubrication equation has been obtained, such as jumping phenomenon around a Rayleigh step, vortex structure, and shear stress distribution. The pressure distribution of the Rayleigh step bearing with optimum geometry has been numerically simulated and the results obtained agreed with the analytical solution of the classical Reynolds lubrication equation. The simulation results show that the maximum pressure of the flow field is at the step tip not on the lower surface and the increment of the strain rate from Navier-Stokes equation is approximately 49 percent greater than that from Reynolds theory at the step tip. It is also shown that the position of the maximum pressure of the lower surface is a little less than the length of the first region. These results neglected by the Reynolds lubrication equation are important for designing a bearing.

Experimental and Numerical Investigation of the Flow in a LP Industrial Steam Turbine With Part-Span Connectors

2015 ◽  
Author(s):  
M. Häfele ◽  
C. Traxinger ◽  
M. Grübel ◽  
M. Schatz ◽  
D. M. Vogt ◽  
...  
Keyword(s):  
Flow Field ◽  
Steam Turbine ◽  
Numerical Study ◽  
Resonance Condition ◽  
Three Dimensional ◽  
Measurement Data ◽  
Detailed Comparison ◽  
Operating Conditions ◽  
Engineering Practice ◽  
Wide Range

An experimental and numerical study on the flow in a three stage low pressure (LP) industrial steam turbine is presented and analyzed. The investigated LP section features conical friction bolts in the last and a lacing wire in the penultimate rotor blade row. These part-span connectors (PSC) allow safe turbine operation over an extremely wide range and even in blade resonance condition. However, additional losses are generated which affect the performance of the turbine. In order to capture their impact on the flow field, extensive measurements with pneumatic multi-hole probes in an industrial steam turbine test rig have been carried out. State-of-the-art three-dimensional CFD applying a non-equilibrium steam (NES) model is used to examine the aero-thermodynamic effects of the PSC on the wet steam flow. A detailed comparison between measurement data and CFD results is performed for several operating conditions. The investigation shows that the applied CFD model is able to capture the three-dimensional flow field in LP steam turbine blading with PSC and the total pressure reduction due to the PSC with a generally good agreement to measured values and is therefore sufficient for engineering practice.

Improved Thermal Uniformity by Introducing Tree-Like Flowing Channels in a PEMFC Flow-Field Plate

2017 ◽  
Author(s):  
Yuxin Jia ◽  
Rui Zhu ◽  
Bengt Sunden ◽  
Gongnan Xie
Keyword(s):  
Fuel Cells ◽  
Flow Field ◽  
Proton Exchange Membrane ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Flow Channel ◽  
Proton Exchange ◽  
Field Plate ◽  
Flow Channels ◽  
Exchange Membrane

Thermal uniformity in the flow field plate of proton exchange membrane fuel cells (PEMFCs) is crucial for their power generating efficiency and reliability and therefore, has attracted much attention. The present numerical study is an attempt to optimize the flow channels via replacement of convectional zigzag continuous channels by tree-like bifurcated channels radially outwards. The numerical model is validated by experimental data available in the open literature. The effects of included angles and length ratios among the channels on thermal uniformity are analyzed based on detailed fluid flow characteristics. Results show that tree-like channels outperform conventional ones. It is found that tree-like flow channels can improve thermal uniformity of proton exchange membrane fuel cells. Within limits, with smaller angle between bifurcated flow channels and length ratio 2−1/3 between higher flow channel and lower flow channel, PEMFC can obtain the most uniform temperature distribution in Y shape tree-liked flow field.

A numerical study of aerodynamic characteristics of a high-speed train with different rail models under crosswind

2020 ◽  
pp. 095440972096925
Author(s):  
Zhiwei Jiang ◽  
Tanghong Liu ◽  
Houyu Gu ◽  
Zijian Guo
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Simulation Method ◽  
Aerodynamic Characteristics ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Pressure Distributions ◽  
Significant Difference ◽  
Aerodynamic Performances ◽  
Yaw Angle

The CFD (Computational Fluid Dynamics) numerical simulation method with the DES (detached eddy simulation) approach was adopted in this paper to investigate and compare the aerodynamic performance, pressure distributions of the train surface, and flow fields near the train model placed above the subgrade with non-rail, realistic rail, and simplified rail models under crosswind. The numerical methods were verified with the wind tunnel tests. Significant differences in aerodynamic performances of the train body and bogie were found in the cases with and without a rail model as the presence of the rail model had significant impacts on the flow field underneath the vehicle. A larger yaw angle can result in a more significant difference in aerodynamic coefficients. The deviations of the train aerodynamic forces and the pressure distribution on the train body with the realistic and simplified rail models were not significant. It was concluded that a rail model is necessary to get more realistic results, especially for large yaw angle conditions. Moreover, a simplified rectangular rail model is suggested to be employed instead of the realistic rail and is capable to get accurate results.

Numerical investigation on the flow field of a modified vortex spinning system for producing core-spun yarns

2019 ◽  
Vol 89 (19-20) ◽  
pp. 4028-4045
Author(s):  
Zeguang Pei ◽  
Ge Chen
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Swirling Flow ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Secondary Flows ◽  
Wall Region ◽  
The Core ◽  
Spun Yarns ◽  
Bottom Roller

A modified vortex spinning technology, which produces core-spun yarns by means of a tangentially injected swirling airflow, is of great prospect in view of its production rate and yarn structure. In this paper, a numerical study based on computational fluid dynamics is presented to investigate the characteristics of the flow field of this system. In the simulation, the effect of the rotating front rollers on the flow field is taken into consideration. Flow characteristics inside the spinning nozzle, flow field of the front rollers, and streamline patterns have been revealed. The results show that a high-speed swirling flow is generated in the near-wall region in the nozzle chamber due to the ejection of air-jets from the tangential injectors. An asymmetric sub-pressure zone is formed in the core region of the nozzle chamber where the interactions of the high-speed swirling flow and three streams of secondary flows generate three vortices. Airflows in the vicinity of the front rollers generally converge toward the nozzle entrance from all directions except those in the boundary layer of the front roller surfaces, which is helpful for the delivery of fibers into the nozzle. A vortex is formed above the top roller and another beneath the bottom roller. The results of the streamline patterns show that the flow characteristics of the modified vortex spinning can facilitate the formation process of the core-spun yarn, which presents a qualitative explanation to the dynamic behavior of the fibers that was experimentally obtained.

Numerical Study on Flow Characteristics in a Stirring Vessel

2011 ◽  
Vol 130-134 ◽  
pp. 3050-3053
Author(s):  
Ru Quan Liang ◽  
Jun Hong Ji ◽  
Fu Sheng Yan ◽  
Ji Cheng He
Keyword(s):  
Flow Field ◽  
Numerical Study ◽  
Fluid Model ◽  
Rotational Velocity ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Experimental Result ◽  
Flow Rule ◽  
Two Phase ◽  
Impeller Type

In order to improve the desulphurization efficiency of KR mixing method in the process of molten iron refining, the method of CFD was used to analyze the flow field in a stirring vessel. The Fluent software was adopted to simulate and analyze the internal flow rule in a 3D stirring vessel with the method of multiple reference frame approach, and the corresponding models of Euler two-phase flow fluid model and standard k-ε turbulence model were used. By comparing with the experimental result, the influence of important parameters of agitator on internal flow field in the stirring vessel, such as rotational velocity, immersion depth and impeller type was discussed, and the flow structure was analyzed as well.

Numerical Study of Cavitating Flow in Two-Phase LNG Expander

2016 ◽  
Author(s):  
Peng Song ◽  
Jinju Sun ◽  
Kaiqiang Li ◽  
Ke Wang ◽  
Changjiang Huo
Keyword(s):  
Design Optimization ◽  
Numerical Study ◽  
Temperature Drop ◽  
Flow Analysis ◽  
Flow Characteristics ◽  
Cavitating Flow ◽  
Cavitation Model ◽  
Two Phase ◽  
Hydraulic Turbines ◽  
Liquefaction Process

LNG expander is developed and used as a replacement of a J-T valve in liquefaction process of natural gas to reduce significantly the energy consumption in the LNG plant. Similar to conventional hydraulic turbines, the unexpected cavitation also occurs in the LNG expander. In the present study, cavitating flow in two-phase LNG expander is investigated. With the justified Rayleigh-Plesset cavitation model, cavitating flow characteristics is investigated for the LNG expander in the entire stage environment including an annular bend, nozzle ring, and radial inflow impeller. On the basis of cavitating flow analysis, a coaxial rotating exducer is developed and fitted downstream to the impeller, so as to reduce the cavitation in impeller and subsequently prevent impeller damage. The following are demonstrated: (1) without exducer, significant cavitating flow is encountered at the impeller trailing edge and also in half streamline-wise region, and they are resulted from the viscous dissipation and flow separation; (3) with exducer, the impeller cavitation has diminished entirely but it has occurred in the successive exducer; (3) a use of exducer enhances the energy conversion capability of the rotors, but reduces the overall temperature drop and efficiency of the expander; (4) the design optimization of exducer is required to suppress the exducer cavitation, which also needs to be incorporated with the impeller design to achieve a better match between rotor/stator, so as to maximize the design optimization benefits.

Numerical Study of Laminar Fluid Flow Around Two Cubes of Arbitrary Configuration Mounted on a Surface

2008 ◽  
Author(s):  
Mohammad Eslami ◽  
Mohammad Mehdi Tavakol ◽  
Ebrahim Goshtasbi Rad
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Flow Field ◽  
Numerical Study ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
Bluff Bodies ◽  
Laminar Fluid Flow ◽  
Pressure Distributions ◽  
Arbitrary Configuration

The problem of flow field around single or multiple bluff bodies mounted on a surface is of great importance in different fields of engineering. The case of a single surface mounted cube has been studied extensively but unfortunately, little attention has been paid to the flow around two or more rectangular blocks in array. Therefore, A CFD code is developed to calculate three dimensional steady state laminar fluid flow around two cuboids of arbitrary size and configuration mounted on a surface in free stream conditions. The employed numerical scheme is finite volume and SIMPLE algorithm is used to treat pressure and velocity coupling. Results are presented for two cubes of the same size mounted on a surface for various inline and staggered arrangements. Streamlines at different planes are plotted for various combinations of the distance between the two cubes and Reynolds number. Velocity and pressure distributions are also plotted in the wake region behind the cubes. It is shown that presence of the second cube completely changes the flow field and vortical structures in comparison with the case of a single cube. Effects of the both stream-wise and spanwise distances between the two cubes and Reynolds number are also discussed.

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