Theoretical and Experimental Study of Centrifugal Compressor Impellers Elnashar, H Amr, Eldalil, M Khaled, Hashim, A., Ali, Abdelrahman, M Mohamed (original) (raw)
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유체기계 연구개발 발표회 논문집, 2015
The prediction and design of the aerodynamic performance of a compressor are crucial requirements to properly evaluate the aerodynamic performance and characteristics during preliminary design of a centrifugal compressor because it is not clear to figure out the internal flow property of a compressor including complicated three dimensional turbulent flow. In this study the industrial centrifugal compressor was calculated for variations of mass flow and blade Mach number with 2 cases of different number of diffuser vanes. One of the major cause of the impeller loss is the pressure drop when the operating mass flow rate closes to choking flow coefficient. Momentum transfer and loss characteristics of the impeller are important to understand impeller characteristics. The method was suggested to estimate the impeller performance characteristics.
The flow in centrifugal compressors is characterized by its stable margin at all speeds of rotation. In this study an experimental measurements are carried out by using slots in the impeller blades at a shroud distance of 30 % from the exit of the blade. It is found that the stable margin is increased due to minimizing the boundary layer growth near the exit part of the blade at off and design speeds, and hence increasing the stable margin in two directions, the first by decreasing the minimum flow rate and surge margin and the second by increasing the maximum mass flow rate. It was found that the surge margin is decreased by 24% and the maximum flow rate is increased by 16.5% and hence, the total stable margin is increased by 60 %. The deriving power of the compressor is decreased due to decreasing the impeller losses. It was found that the losses are decreased from 30-35 % to about 2-3 % at medium speeds. The pressure ratio is not increased at all speeds but the efficiency is incr...
An Investigation on the Performance Characteristics of a Centrifugal Compressor
The design and off-design performance characteristics of single stage centrifugal compressor consisting of 12 vanes impeller interfacing with 11 vanes diffuser have been studied experimentally and numerically. The impeller has been designed and developed with radial exit, 30o inlet blade angle (with tangent), 77 mm diameter and the discharge volute considering constant mean flow velocity. The performance of the compressor at varying capacity (60 to 120 % of design) by controlling the discharge valve and with the variation of rotating speed (15000 to 35000 rpm) by regulating speed of the coupled gas turbine has been conducted at the recently developed test rig. The numerical simulation has been done by adopting viscous Reynolds Average Navier-Stokes (RANS) equations with and without Coriolis Force & Centrifugal Force in rotating reference frame (impeller) and stationary reference frame (casing) respectively utilizing CFD software Fluent 14. The flow around a single vane of impeller interfacing with single vane of diffuser, the rotational periodicity and sliding mesh at the interfacing zone between rotating impeller and stationery diffuser are considered. Non dimensional performance curves derived from experimental and numerical results are presented and compared. The numerical results are found to match very closely with the experimented data near the design point and deviation is observed at the both side of the designed operating point. Non-uniform pressure profiles towards the impeller exit and strong cross flow from blade to blade are detected at low flow operating conditions. Total pressure, static pressure and velocity distributions at design and off design operation obtained from the CFD results are analysed and presented here.
Head Math Model For The Low-Flow Impellers Of The Centrifugal Compressors
E3S Web of Conferences, 2019
A new mathematical model has been developed to determine the coefficient of internal and theoretical head in the variant design of the low-flow rate centrifugal compressors impellers. A parametric study of the flow part of the impeller is carried out. In total 1620 impellers are numericaly simulated. As a result, a numerical database of gas dynamic and geometric parameters was developed. Due to an a priori analysis, the relations of parameters with the geometric shape of the flow part are determined. The mathematical model is developed using gas-dynamic parameters and relations determined from numerical database. Using centrifugal compressor stage digital twins, a generalizing relationship has been developed to determine the complex of friction and leakage losses.The reliability of the math model is validated by the comparison with experimental data and the results of numerical experiment in digital twins, which are not involved in the model. The application of the head math model i...
Some Aerodynamic Considerations in the Design of Centrifugal Compressor Impellers
Abstract: A simple one dimensional approach to determine the size of the centrifugal impeller for maximum through flow has been indicated. This design procedure does not mean that the centrifugal impeller could be finally decided on the results obtained from this article. It must be borne in mind that this only deals with some aspects of the design and in itself is not a complete one by which the impeller could have its final shape and size. The major idea of introducing this paper is to highlight the importance of some of the parameters that go towards influencing the design of the centrifugal impeller.
Effect of impeller geometry on performance characteristics of centrifugal compressor
2019
Centrifugal Compressors play an essential role in oil, gas and petrochemical industries. Their extensive usage is due to their smooth operation and high reliability compared to other other compressor types. One of the main characteristics of these turbomachines is their performance curve, which is an important criterion for selecting the appropriate compressor for a desired working condition. In the presented article, the effect of impeller’s geometry on performance curve and other compressors characteristics is numerically investigated. The 3D CFD code is used to achieve the performance curves that are dedicated to each geometrical configuration. The results indicate that some of the selected geometrical parameters have a significant effect on performance curve margins. Increasing the shroud angle moves the surge point to the higher flow coefficients, while the pressure ratio remains constant and increasing the blade’s trailing edge angle, leads to increase in pressure ratio.
Numerical characteristics of a centrifugal compressor with a low flow coefficient
E3S Web of Conferences, 2019
The study presents the simulation results of the viscid gas flow in low flow coefficient centrifugal compressor stages. The problem is solved in a stationary formulation using the Ansys CFX software package. The numerical simulation is carried out on three ultrahigh-pressure model stages; two stages have blades of the classical type impeller and one stage is of the bodily type. The value of the conditional flow coefficient is 0.0063 to 0.015. As part of the study, block-structured design meshes are used for all gas channel elements, with their total number being equaled as 13–15 million. During the calculations a numerical characteristic was validated with the results of tests carried out at the Department of Compressor, Vacuum and Refrigeration Engineering of Peter the Great St. Petersburg Polytechnic University. With an increase of inlet pressure as a result of a numerical study, it was found that for a given mathematical model the disk friction and leakage coefficient (1 + βfr + ...
Study of Secondary Flow Modifications at Impeller Exit of a Centrifugal Compressor
Open Journal of Fluid Dynamics, 2012
A computational study has been conducted to analyze the performance of a centrifugal compressor under various levels of impeller-diffuser interactions. The study has been conducted using a low solidity vaned diffuser (LSVD), a conventional vaned diffuser (VD) and a vaneless diffuser (VLD). The study is carried out using Reynolds-Averaged Navier-Stokes simulations. A commercial software ANSYS CFX is used for this purpose. The extent of diffuser influence on impeller flow is studied by keeping the diffuser vane leading edge at three different radial locations. Detailed flow analysis inside the impeller passage shows that the strength and location of the wake region at the exit of impeller blade is heavily depended upon the tip leakage flow and the pressure equalization flow. Above design flow rate, the diffuser vane affects only the last twenty percent of the impeller flow. However, below design flow rate, keeping vane closer to the impeller can cause an early stall within the impeller. Small negative incidence angle at the diffuser vane is helpful in order to reduce the losses at the impeller exit.
Efficient, compact centrifugal compressors with higher pressure ratios along with adequate surge margins are required for the future. Achieving these necessitates development of newer non-conventional diffuser designs and rotating vaneless diffusers is one such concept. One method of reducing the shear losses on the stationary vaneless diffuser sidewalls, with probable improved efficiency and flow range of low-toof rotating vaneless diffuser is forced rotating vaneless diffuser, in which the rotational speed equals that of the impeller and the rotating vaneless diffuser is integral with the centrifugal impeller which is created by extending the impeller disks beyond the blades. In the present paper, the effect of extended shroud by 10% with impeller exit diameter are analysed on flow diffusion and performance and compared with stationary vaneless diffuser. The higher static pressure rise with reduced losses and increased efficiency is achieved by shroud extension.
Design analysis of centrifugal compressor impeller vanes
INTERNATIONAL CONFERENCE ON ADVANCES IN MATERIALS, COMPUTING AND COMMUNICATION TECHNOLOGIES: (ICAMCCT 2021), 2022
To determine the performance characteristics of centrifugal compressor impeller vane by optimising the shape of the forward impeller blade of the single sided centrifugal compressor through design modelling analysis thereby increasing the velocity and pressure of the compressor blade. The primary motivation behind this work is to plan an impeller with more productive execution considering streamlining the state of the forward impeller at the root and tip, which pack the approaching air at 500 rpm, where it then passes the pressurized air to the diffuser through the outlet situated at the end of the compressor, This pressurized air when it mixes with fuel, during combustion takes place in the combustion chamber the amount of burning rate will be high the to produce more efficiency as well as more amount of thrust is produced for accelerating the engine. The modelling is done using Catia v5 and simulation is done in Ansys Fluent 18.