Performance Characteristics of a Centrifugal Compressor with Air Injection

1973 ◽  
Vol 187 (1) ◽  
pp. 425-434 ◽  
Author(s):  
J. D. Ledger ◽  
R. S. Benson ◽  
H. Furukawa
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
Total Mass ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Performance Characteristics ◽  
Air Injection ◽  
Delivery Pressure ◽  
Mass Flow Rates ◽  
The Right

The parameters which influence the performance characteristics of centrifugal compressors with air injection through nozzles at the rotor tip are developed using both dimensional analysis and a simple model. Experiments on a small centrifugal compressor show that the injection air pressure is the main influence on the overall performance such as excess torque, increased delivery pressure and increased delivery flow. With air injection the pressure-mass flow characteristics are displaced to the right with surge occurring at increased total mass flow rates and the overall pressure ratio across the compressor is increased for the same total mass flow.

Performance Characteristics of a Centrifugal Compressor with Air Injection

1973 ◽  
Vol 187 (1) ◽  
pp. 425-434 ◽  
Author(s):  
J. D. Ledger ◽  
R. S. Benson ◽  
H. Furukawa
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
Total Mass ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Performance Characteristics ◽  
Air Injection ◽  
Delivery Pressure ◽  
Mass Flow Rates ◽  
The Right

The parameters which influence the performance characteristics of centrifugal compressors with air injection through nozzles at the rotor tip are developed using both dimensional analysis and a simple model. Experiments on a small centrifugal compressor show that the injection air pressure is the main influence on the overall performance such as excess torque, increased delivery pressure and increased delivery flow. With air injection the pressure-mass flow characteristics are displaced to the right with surge occurring at increased total mass flow rates and the overall pressure ratio across the compressor is increased for the same total mass flow.

Numerical Investigation of the Effect of Tip Clearance to the Performance of a Small Centrifugal Compressor

2006 ◽  
Author(s):  
Jin Tang ◽  
Teemu Turunen-Saaresti ◽  
Arttu Reunanen ◽  
Juha Honkatukia ◽  
Jaakko Larjola
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Flow Distribution ◽  
Ideal Gas ◽  
Tip Clearance ◽  
Flow Angle ◽  
Flow Rates ◽  
Real Gas ◽  
Mass Flow Rates

Numerical analysis is conducted for the 3-dimensional impeller and vaneless diffuser of a small centrifugal compressor. The influence of impeller tip clearance is investigated. A Navier-Stokes flow solver Finflo has been applied for the simulation. A practical real gas model has been generated for the calculation. Simulations with different sizes of tip clearance at different mass flow rates have been made. The results are compared to experimental results at a certain tip clearance and one operating point. Reasonable agreement has been obtained. The ideal gas model has also been applied to compare with the real gas model. The numerical results show that tip clearance has a significant effect on the performance of a small centrifugal compressor. As the size of tip clearance increases, both the pressure ratio and the efficiency decrease. The decreasing rate of efficiency is higher at higher mass flow rates and lower at lower mass flow rates. The input power of the compressor hardly changes with different sizes of tip clearance, but increases as the mass flow rate increases. The incidence of impeller and flow angle at the exit of the impeller increase as the size of tip clearance increases. Correlations of the size of tip clearance with the efficiency drop and change of flow angle at the exit of impeller are given. The detailed flow distribution shows that as the size of tip clearance increases, the tangential leaking flow at the tip clearance makes the low velocity flow region grow larger and move from the suction-shroud corner to the center of the flow channel. The main flow at the pressure side is compressed and accelerated. Therefore the uniformity of the flow in the whole channel decreases. The detailed flow distribution also shows that the leaking flow is stronger at higher mass flow rates.

An Investigation of Centrifugal Compressor Stability Enhancement Using a Novel Vaned Diffuser Recirculation Technique

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Lee Galloway ◽  
Daniel Rusch ◽  
Stephen Spence ◽  
Klemens Vogel ◽  
René Hunziker ◽  
...  
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Vaned Diffuser ◽  
Casing Treatment ◽  
Operating Range ◽  
Stable Operating ◽  
Mass Flow Rates ◽  
Low Mass ◽  
Casing Treatments

The main centrifugal compressor performance criteria are pressure ratio, efficiency, and wide flow range. The relative importance of these criteria, and therefore the optimum design balance, varies between different applications. Vaned diffusers are generally used for high-performance applications as they can achieve higher efficiencies and pressure ratios, but have a reduced operating range, in comparison to vaneless diffusers. Many impeller-based casing treatments have been developed to enlarge the operating range of centrifugal compressors over the last decades but there is much less information available in open literature for diffuser focused methods, and they are not widely adopted in commercial compressor stages. The development of aerodynamic instabilities at low mass flow rate operating conditions can lead to the onset of rotating stall or surge, limiting the stable operating range of the centrifugal compressor stage. More understanding of these aerodynamic instabilities has been established in recent years. Based on this additional knowledge, new casing treatments can be developed to prevent or suppress the development of these instabilities, thus increasing the compressor stability at low mass flow rates. This paper presents a novel vaned diffuser casing treatment that successfully increased the stable operating range at low mass flow rates and high pressure ratios. Detailed experimental measurements from a high pressure ratio turbocharger compressor stage combined with complementary CFD simulations were used to examine the effect of the new diffuser casing treatment on the compressor flow field and led to the improvement in overall compressor stability. A detailed description of how the new casing treatment operates is presented within the paper.

Backward Traveling Rotating Stall Waves in Centrifugal Compressors

2002 ◽  
Author(s):  
Z. S. Spakovsky
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
First Principles ◽  
Rotating Stall ◽  
Air Injection ◽  
System Stability ◽  
Centrifugal Compressors ◽  
Injection Scheme ◽  
Surge Margin ◽  
Low Order

Rotating stall waves that travel against the direction of rotor rotation are reported for the first time and a new, low-order analytical approach to model centrifugal compressor stability is introduced. The model is capable of dealing with unsteady radially swirling flows and the dynamic effects of impeller-diffuser component interaction as it occurs in centrifugal compression systems. A simple coupling criterion is developed from first principles to explain the interaction mechanism important for system stability. The model findings together with experimental data explain the mechanism for first-ever observed backward traveling rotating stall in centrifugal compressors with vaned diffusers. Based on the low-order model predictions, an air injection scheme between the impeller and the vaned diffuser is designed for the NASA Glenn CC3 high-speed centrifugal compressor. The steady air injection experiments show an increase of 25% in surge-margin with an injection mass flow of 0.5% of the compressor mass flow. In addition, it is experimentally demonstrated that this injection scheme is robust to impeller tip-clearance effects and that a reduced number of injectors can be applied for similar gains in surge-margin. The results presented in this paper firmly establish the connection between the experimentally observed dynamic phenomena in the NASA CC3 centrifugal compressor and a first principles based coupling criterion. In addition, guidelines are given for the design of centrifugal compressors with enhanced stability.

scholarly journals Determination of mass flow characteristics of supersonic axisymmetric nozzle diaphragms in modeling variable duties of low-consumption turbines

2020 ◽  
pp. 39-43
Author(s):  
Р.Р. Симашов ◽  
С.В. Чехранов
Keyword(s):  
Mass Flow ◽  
Flow Rate ◽  
Flow Characteristics ◽  
Relative Length ◽  
Axisymmetric Nozzle ◽  
Relative Flow Rate ◽  
Wide Range ◽  
Mass Flow Rates ◽  
Subsonic Part ◽  
Low Consumption

В работе приводятся обобщающие зависимости коэффициентов расхода сопловых аппаратов со сверхзвуковыми осесимметричными соплами в широком диапазоне изменения определяющих геометрических и режимных параметров. Предложена двухпараметрическая функция, учитывающая влияние расположения сопел в сопловом аппарате и степени конфузорности дозвуковой части осесимметричного сопла на коэффициент расхода. Показано слабое влияние на коэффициент расхода относительного радиуса закругления стенки в узкой части сопла и относительной длины дозвуковой части сопла в области их оптимальных значений определенных по минимуму потерь кинетической энергии. Переменные режимы работы сопла учитываются зависимостью относительного коэффициента расхода в функции от числа Рейнольдса в критическом сечении сопла. Полученные в работе эмпирические зависимости позволяют использовать их при моделировании переменных режимов и многорежимной оптимизации малорасходных турбин. The research presents generalizing dependences of mass flow rates in supersonic axisymmetric nozzle diaphragms n a wide range of variation of the governing geometric and operating parameters. A two-parameter function is proposed that takes into account the influence of the location of the nozzles in the nozzle apparatus and the degree of compression of the flow of the subsonic part of the nozzle on the mass flow rate. It is shown that the relative radius of rounding of the nozzle wall in the vicinity of the throat section and the relative length of the subsonic part of the nozzle in the region of their optimal values determined by the minimum of kinetic energy losses have a weak effect on the flow rate. Variable duties of nozzle operation are taken into account by the dependence of the relative flow rate as a function of the Reynolds number in the throat of the nozzle. The empirical dependencies obtained in this work make it possible to use them in modeling variable modes and multi-mode optimization of low-consumption turbines.

Numerical Simulations of Onset of Volute Stall Inside a Centrifugal Compressor

2008 ◽  
Author(s):  
Hua Chen ◽  
Strong Guo ◽  
Xiao-Cheng Zhu ◽  
Zhao-Hui Du ◽  
Stone Zhao
Keyword(s):  
Centrifugal Compressor ◽  
Peak Pressure ◽  
Stokes Equations ◽  
Pressure Ratio ◽  
Pressure Rise ◽  
Navier Stokes ◽  
Cross Sectional ◽  
Navier Stokes Equations ◽  
Mass Flow Rates ◽  
Discharge Section

In a previous publication (Guo & Chen et al., 2007), the authors solved the unsteady, 3-D Navier-Stokes equations with the k-ε turbulence model using CFX software to show that there is a volute stall coincided with the stage stall of a turbocharger centrifugal compressor operated at 423m/s tip speed and the stage stall frequency is dictated by a volute standing wave. This paper presents the flow condition at the vaneless diffuser and volute from the same simulation at various mass flow rates from stage peak efficiency to deep stage stall. Time averaged flow conditions show that (1) the influence of exducer blade passing at the volute inlet rapidly diminishes at the compressor peak pressure ratio point and the influence vanishes when the stage is in stall; (2) only at the peak pressure ratio point, circumferentially averaged, spanwise distribution of radial velocity at the volute inlet has an inflection point and the distribution meets the requirement of the Fjo̸rtoft instability theorem; (3) in the volute discharge section, the flow stalls after the stage stalls and the vortex core at the cross sectional center of the section breaks down; (4) impeller total pressure rise curve has a flat region in the middle before the stage stalls and (5) diffuser stall triggers the stage stall and drives the volute into stall.

An Experimental Study of the Flow of R-407C in an Adiabatic Spiral Capillary Tube

2009 ◽  
Vol 1 (4) ◽  
Author(s):  
M. K. Mittal ◽  
R. Kumar ◽  
A. Gupta
Keyword(s):  
Experimental Data ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Capillary Tube ◽  
Flow Characteristics ◽  
Flow Rates ◽  
Tube Test ◽  
Mass Flow Rates ◽  
R 134A

The objective of this study is to investigate the effect of coiling on the flow characteristics of R-407C in an adiabatic spiral capillary tube. The characteristic coiling parameter for a spiral capillary tube is the coil pitch; hence, the effect of the coil pitch on the mass flow rate of R-407C was studied on several capillary tube test sections. It was observed that the coiling of the capillary tube significantly reduced the mass flow rate of R-407C in the adiabatic spiral capillary tube. In order to quantify the effect of coiling, the experiments were also conducted for straight a capillary tube, and it was observed that the coiling of the capillary tube reduced the mass flow rate in the spiral tube in the range of 9–18% as compared with that in the straight capillary tube. A generalized nondimensional correlation for the prediction of the mass flow rates of various refrigerants was developed for the straight capillary tube on the basis of the experimental data of R-407C of the present study, and the data of R-134a, R-22, and R-410A measured by other researchers. Additionally, a refrigerant-specific correlation for the spiral capillary was also proposed on the basis of the experimental data of R-407C of the present study.

Flow Characteristics of a Novel Centrifugal Compressor Design

2016 ◽  
Author(s):  
Shashank Mishra ◽  
Shaaban Abdallah ◽  
Mark Turner
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Axial Compressor ◽  
Low Pressure ◽  
Flow Path ◽  
Optimization Techniques ◽  
Single Stage ◽  
Multi Stage ◽  
Compressor Design

Multistage axial compressor has an advantage of lower stage loading as compared to a single stage. Several stages with low pressure ratio are linked together which allows for multiplication of pressure to generate high pressure ratio in an axial compressor. Since each stage has low pressure ratio they operate at a higher efficiency and the efficiency of multi-stage axial compressor as a whole is very high. Although, single stage centrifugal compressor has higher pressure ratio compared with an axial compressor but multistage centrifugal compressors are not as efficient because the flow has to be turned from radial at outlet to axial at inlet for each stage. The present study explores the advantages of extending the axial compressor efficient flow path that consist of rotor stator stages to the centrifugal compressor stage. In this invention, two rotating rows of blades are mounted on the same impeller disk, separated by a stator blade row attached to the casing. A certain amount of turning can be achieved through a single stage centrifugal compressor before flow starts separating, thus dividing it into multiple stages would be advantageous as it would allow for more flow turning. Also the individual stage now operate with low pressure ratio and high efficiency resulting into an overall increase in pressure ratio and efficiency. The baseline is derived from the NASA low speed centrifugal compressor design which is a 55 degree backward swept impeller. Flow characteristics of the novel multistage design are compared with a single stage centrifugal compressor. The flow path of the baseline and multi-stage compressor are created using 3DBGB tool and DAKOTA is used to optimize the performance of baseline as well novel design. The optimization techniques used are Genetic algorithm followed by Numerical Gradient method. The optimization resulted into improvements in incidence and geometry which significantly improved the performance over baseline compressor design. The multistage compressor is more efficient with a higher pressure ratio compared with the base line design for the same work input and initial conditions.

Numerical Performance and Flow Field Study of Centrifugal Compressor With Supercritical Carbon-Dioxide (SCO2)

2019 ◽  
Author(s):  
Hemant Kumar ◽  
Chetan S. Mistry
Keyword(s):  
Carbon Dioxide ◽  
Thermodynamic Properties ◽  
Critical Point ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Compressor Inlet

Abstract The Supercritical carbon-dioxide Brayton cycle main attraction is due to the Supercritical characteristic of the working fluid, carbon-dioxide (SCO2). Some of the advantages of using SCO2 are relatively low turbine inlet temperature, the compression work will be low, and the system will be compact due to the variation of thermodynamic properties (like density, and specific heat ratio) of SCO2 near the critical point. SCO2 behave more like liquid when its state is near the critical point (Total Pressure = 7.39 MPa, Total Temperature = 305 K), operating compressor inlet near critical point can minimize compression work. For present study the centrifugal compressor was designed to operate at 75,000 rpm with pressure ratio (P.R) = 1.8 and mass flow rate = 3.53 kg/s as available from Sandai report. Meanline design for centrifugal compressor with SCO2 properties was done. The blade geometry was developed using commercial CAD Ansys Bladegen. The flow domain was meshed using Ansys TurboGrid. ANSYS CFX was used as a solver for present numerical study. The thermodynamic properties of SCO2 were imported from the ANSYS flow material library using SCO2.RPG [NIST thermal physics properties of fluid system]. In order to ensure the change in flow physics the mesh independence study was also conducted. The present paper discuss about the performance and flow field study targeting different mass flow rates as exit boundary condition. The comparison of overall performance (Pressure Ratio, the Blade loading, Stage efficiency and Density variation) was done with three different mass flow rates. The designed and simulated centrifugal compressor meets the designed pressure rise requirement. The variation of mass flow rate on performance of centrifugal compressor was tend to be similar to conventional centrifugal compressor. The paper discusses about the effect of variation in density, specific heat ratio and pressure of SCO2 with different mass flow outlet condition. The performance map of numerical study were validated with experiment results and found in good agreement with experimental results. The change in flow properties within the rotor flow passage are found to be interesting and very informative for future such centrifugal compressor design for special application of SCO2 Brayton cycle. 80% mass flow rate has given better results in terms of aerodynamic performance. Abrupt change in thermodynamic properties was observed near impeller inlet region. Strong density variations are observed at compressor inlet.

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