Numerical analysis of gas bearings in oil-free linear compressors

2020 ◽  
pp. 095440892094381
Author(s):  
Xinye Zhang ◽  
Davide Ziviani ◽  
James E Braun ◽  
Eckhard A Groll
Keyword(s):  
Numerical Analysis ◽  
Cylinder Wall ◽  
Vapor Compression ◽  
Linear Compressor ◽  
Gas Bearings ◽  
Frictional Losses ◽  
Operation Conditions ◽  
Overall Performance ◽  
Volume Method ◽  
Gas Bearing

Recently, linear compressor technology has gained increased attention in vapor compression systems due to its compactness and lower frictional losses compared with the conventional reciprocating compressors. Since the absence of the crank-mechanism eliminates the rotation and reduces the side loads on the piston centered inside the cylinder, it is possible to operate the linear compressors without oil lubrication. A number of advantages can be obtained in terms of the refrigerant compatibility, operation conditions and the system cost. In order to enable oil-free operation, while minimizing frictional losses and leakage flow between the piston and the cylinder wall, a gas bearing approach is applied. Little work was found in the open literature related to the numerical analysis of gas bearings coupled with a comprehensive dynamic linear compressor model. This paper presents a 1-D gas bearing model based on a Finite Volume Method (FVM) applied to a linear compressor. The dynamic characteristics of the gas bearings on the gas film pressure field are analyzed using the model. When integrated together with a comprehensive dynamic linear compressor model, it is possible to predict leakage and frictional losses within the compressor as well as the overall performance.

scholarly journals Effects of mesh loop modes on performance of unstructured finite volume GPU simulations

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Yue Weng ◽  
Xi Zhang ◽  
Xiaohu Guo ◽  
Xianwei Zhang ◽  
Yutong Lu ◽  
...  
Keyword(s):  
Finite Volume ◽  
Data Access ◽  
Data Locality ◽  
Data Dependence ◽  
Speed Up ◽  
Computational Fluid Dynamics Cfd ◽  
Overall Performance ◽  
Volume Method ◽  
Cell Data ◽  
Unstructured Finite Volume Method

AbstractIn unstructured finite volume method, loop on different mesh components such as cells, faces, nodes, etc is used widely for the traversal of data. Mesh loop results in direct or indirect data access that affects data locality significantly. By loop on mesh, many threads accessing the same data lead to data dependence. Both data locality and data dependence play an important part in the performance of GPU simulations. For optimizing a GPU-accelerated unstructured finite volume Computational Fluid Dynamics (CFD) program, the performance of hot spots under different loops on cells, faces, and nodes is evaluated on Nvidia Tesla V100 and K80. Numerical tests under different mesh scales show that the effects of mesh loop modes are different on data locality and data dependence. Specifically, face loop makes the best data locality, so long as access to face data exists in kernels. Cell loop brings the smallest overheads due to non-coalescing data access, when both cell and node data are used in computing without face data. Cell loop owns the best performance in the condition that only indirect access of cell data exists in kernels. Atomic operations reduced the performance of kernels largely in K80, which is not obvious on V100. With the suitable mesh loop mode in all kernels, the overall performance of GPU simulations can be increased by 15%-20%. Finally, the program on a single GPU V100 can achieve maximum 21.7 and average 14.1 speed up compared with 28 MPI tasks on two Intel CPUs Xeon Gold 6132.

The Numerical Analysis of the Velocity and Pressure Distribution of the Oil Film in Heavy Hydrostatic Thrust Bearing

2014 ◽  
Vol 541-542 ◽  
pp. 658-662
Author(s):  
Jian Li ◽  
Yuan Chen ◽  
Yang Chun Yu ◽  
Zhu Xin Tian ◽  
Yu Huang
Keyword(s):  
Mathematical Model ◽  
Numerical Analysis ◽  
Pressure Distribution ◽  
Working Conditions ◽  
Thrust Bearing ◽  
Rotation Speed ◽  
The Other ◽  
Surface Load ◽  
Oil Film ◽  
Volume Method

To study the velocity and pressure distribution of the oil film in a heavy hydrostatic thrust bearing, a mathematical model of the velocity is proposed and the finite volume method (FVM) has been used to simulate the flow field under different working conditions. Some pressure experiments were carried out and the results verified the correctness of the simulation. It is concluded that the pressure distribution varies small under different rotation speed when the surface load on the workbench is constant. But the velocity of the oil film is influenced greatly by the rotation speed. When the rotation speed of the workbench is as quick as enough, the velocity of the oil film on one radial side of the pad will be zero, that is to say the lubrication oil will be drained from the other three sides of the recess.

Numerical Analysis of the Turbulent Flow Field Applied to Thermal Spallation Drilling

2004 ◽  
Author(s):  
Angela O. Nieckele ◽  
Luis Fernando Figueira da Silva ◽  
Joa˜o Carlos R. Pla´cido
Keyword(s):  
Reynolds Number ◽  
Numerical Analysis ◽  
Flow Field ◽  
Gas Phase ◽  
Accurate Determination ◽  
Rock Surface ◽  
Drilling Technique ◽  
High Reynolds ◽  
Drilling Conditions ◽  
Volume Method

Thermal spallation is a possible drilling technique which consists of using hot supersonic jets as heat source to perforate hard rocks at high rates. This work presents a numerical analysis of a typical spallation drilling configuration, by the finite volume method. The time-averaged conservation equations of mass, momentum and energy are solved to determine the turbulent compressible gas phase flow field. Turbulence is predicted by the classical high Reynolds number κ-ε model, as well as with a low Reynolds number κ-ε model. The influence of the jet Reynolds number is investigated. Special attention is given to the rock surface temperature, since its accurate determination is required to predict spallation rates under field-drilling conditions.

Externally pressurized gas bearings in a mixed configuration

2002 ◽  
Vol 216 (2) ◽  
pp. 181-189
Author(s):  
A Cazan ◽  
R Gohar ◽  
M M A Safa
Keyword(s):  
Full Length ◽  
The Other ◽  
Gas Bearings ◽  
High Stiffness ◽  
Parallel Arrangement ◽  
Gas Bearing

This paper analyses the stabilityof an externally pressurized gas bearing (EPB) in a series-parallel arrangement. This mixed con. guration is an alternative to the rigidly mounted single bearing with no external damping, yielding, as one extreme, a high stiffness, but a low whirl threshold speed. The other extreme is a series bearing arrangement with a full-length externally pressurized sleeve between the journal and the housing, yielding a lower stiffness but a higher whirl threshold speed. The paper shows that a mixed con. guration allows for an increase in whirl threshold speed above that for an equivalent rigidly mounted single bearing but below that for a series arrangement. However, the mixed con. guration is stiffer than the series arrangement.

A NUMERICAL ANALYSIS OF A REACTION–DIFFUSION SYSTEM MODELING THE DYNAMICS OF GROWTH TUMORS

2010 ◽  
Vol 20 (05) ◽  
pp. 731-756 ◽  
Author(s):  
VERÓNICA ANAYA ◽  
MOSTAFA BENDAHMANE ◽  
MAURICIO SEPÚLVEDA
Keyword(s):  
Weak Solution ◽  
Numerical Analysis ◽  
Numerical Scheme ◽  
System Modeling ◽  
Reaction Diffusion ◽  
Reaction Diffusion System ◽  
Diffusion System ◽  
Existence Of Weak Solutions ◽  
Early Tumor ◽  
Volume Method

We consider a reaction–diffusion system of 2 × 2 equations modeling the spread of early tumor cells. The existence of weak solutions is ensured by a classical argument of Faedo–Galerkin method. Then, we present a numerical scheme for this model based on a finite volume method. We establish the existence of discrete solutions to this scheme, and we show that it converges to a weak solution. Finally, some numerical simulations are reported with pattern formation examples.

Experimental Identification of Dynamic Force Coefficients for a 110 mm Compliantly Damped Hybrid Gas Bearing

2014 ◽  
Author(s):  
Adolfo Delgado
Keyword(s):  
Load Capacity ◽  
Excitation Frequency ◽  
Dynamic Test ◽  
Inlet Pressure ◽  
Dynamic Force ◽  
Metal Mesh ◽  
Gas Bearings ◽  
Force Coefficients ◽  
Test Parameters ◽  
Gas Bearing

Compliant hybrid gas bearings combine key enabling features from both fixed geometry externally pressurized gas bearings and compliant foil bearings. The compliant hybrid bearing relies on both hydrostatic and hydrodynamic film pressures to generate load capacity and stiffness to the rotor system, while providing damping through integrally mounted metal mesh bearing support dampers. This paper presents experimentally identified force coefficients for a 110 mm compliantly damped gas bearing using a controlled-motion test rig. Test parameters include hydrostatic inlet pressure, excitation frequency, and rotor speed. The experiments were structured to evaluate the feasibility of implementing these bearings in large size turbomachinery. Dynamic test results indicate weak dependency of equivalent direct stiffness coefficients to most test parameters except for frequency and speed, where higher speeds and excitation frequency decreased equivalent bearing stiffness values. The bearing system equivalent direct damping was negatively impacted by increased inlet pressure and excitation frequency, while the cross-coupled force coefficients showed values an order of magnitude lower than the direct coefficients. The experiments also include orbital excitations to simulate unbalance response representative of a target machine while synchronously traversing a critical speed. The results indicate that the gas bearing can accommodate vibration levels larger than the set bore clearance while maintaining satisfactory damping levels.

An Investigation of Cavitation and Suction Vortices Behavior in Pump Sump

2011 ◽  
Author(s):  
Won-Tae Kang ◽  
Ki Han Yu ◽  
Seung Yeob Lee ◽  
Byeong Rog Shin
Keyword(s):  
Experimental Investigation ◽  
Numerical Analysis ◽  
Test Procedure ◽  
Three Dimensional ◽  
Water Levels ◽  
National Standard ◽  
Piping System ◽  
Test Model ◽  
Grid Systems ◽  
Volume Method

A numerical and an experimental investigation on a suction vortices including cavitation, free vortices and subsurface vortices behavior in the model sump system with multi-intakes is performed at several flow rates and water levels. A test model sump and piping system were designed based on Froude similitude for the prototype of the recommended structure layout by HI-9.8 American National Standard for Pump Intake Design of the Hydraulic Institute. An experiment is performed according to the sump model test procedure of Hyosung Goodsprings, Inc. A numerical analysis of three dimensional multiphase flows through the model sump is performed by using the finite volume method of the CFX code with multi-block structured grid systems. A k-ω Shear Stress Transport turbulence model and the Rayleigh-Plesset cavitation model are used for solving turbulence cavitating flow. Several types of free surface and submerged vortex which occurs with each different water level are identified through the experimental investigation. From the numerical analysis, the vortices are reproduced and their formation, growing, shedding and detailed vortex structures are investigated. To reduce abnormal vortices, an anti-vortex device is considered and its effect is investigated and discussed.

scholarly journals Study on dynamic characteristics of gas films of spherical spiral groove hybrid gas bearings

2019 ◽  
Vol 233 (8) ◽  
pp. 1169-1181
Author(s):  
Chenhui Jia ◽  
Haijiang Zhang ◽  
Shijun Guo ◽  
Ming Qiu ◽  
Wensuo Ma ◽  
...  
Keyword(s):  
Pressure Effect ◽  
Dynamic Pressure ◽  
Iteration Algorithm ◽  
Unstable State ◽  
Gas Bearings ◽  
Damping Coefficients ◽  
The Stability ◽  
Stiffness And Damping ◽  
Film Stiffness ◽  
Gas Bearing

According to the gas film force variation law, when the bearing axis is slightly displaced from the static equilibrium position, displacement and velocity disturbance relation expressions for the gas film force increment are constructed. Moreover, combined with the bearing rotor system motion equation, calculation model equations for the gas film stiffness and damping coefficients are established. The axial and radial vibration and velocity of the gas bearings during operation are collected. The instantaneous stiffness and damping coefficients of the gas film are calculated by the rolling iteration algorithm using MATLAB. The dynamic changes in the gas film stiffness and damping under different motion states are analyzed, and the mechanism of the gas film vortex and oscillation is studied. The results demonstrate the following: (1) When the gas bearing is running in the linear steady state in cycle 1, the dynamic pressure effect is enhanced and the stability is improved by increasing the eccentricity; when the gas supply pressure is increased, the static pressure effect is enhanced and the gas film vortex is reduced, but the oscillation is strengthened. (2) With the increase in rotational speed, the gas film vortex force gradually exceeds the gas film damping force, and the stability gradually worsens, causing a fluctuation in the gas film stiffness and damping, following which singularity occurs and a half-speed vortex is formed. Meanwhile, the gas film oscillation is intensified, and the rotor enters the nonlinear stable cycle 2 state operation. (3) As the fluctuation of the film force increases, the instantaneous stiffness and damping oscillation of the film intensifies, most of the stiffness and damping coefficients exhibit distortion, and the rotor operation will enter a chaotic or unstable state. Therefore, the gas bearing stiffness and damping variation characteristics can be used to study and predict the gas bearing operating state. Finally, measures for reducing the vortex and oscillation of the gas film and improving the stability of the gas bearing operation are proposed.

Sign in / Sign up

Export Citation Format

Share Document