Discussion: “Losses in Vaneless Diffusers of Centrifugal Compressors and Pumps: Analysis, Experiment, and Design” (Johnston, J. P., and Dean, Jr., R. C., 1966, ASME J. Eng. Power, 88, pp. 49–60)

1966 ◽  
Vol 88 (1) ◽  
pp. 60-61
Author(s):  
J. H. Howard
Keyword(s):  
Centrifugal Compressors ◽  
Analysis Experiment ◽  
Vaneless Diffusers

Losses in Vaneless Diffusers of Centrifugal Compressors and Pumps: Analysis, Experiment, and Design

1966 ◽  
Vol 88 (1) ◽  
pp. 49-60 ◽  
Author(s):  
J. P. Johnston ◽  
R. C. Dean
Keyword(s):  
Experimental Data ◽  
Centrifugal Compressor ◽  
Friction Loss ◽  
Sudden Expansion ◽  
Centrifugal Compressors ◽  
One Dimensional ◽  
Complex Theory ◽  
Loss Analysis ◽  
Analysis Experiment ◽  
Vaneless Diffusers

Two simple analyses are developed to predict losses in centrifugal compressor (or pump) vaneless diffusers: (a) One-dimensional, axisymmetric friction loss and (b) sudden-expansion mixing to account for losses in the diffuser caused by wakes of separated impeller blades. It is shown that these theories may be substituted for the more complex theory of Dean and Senoo [5]. Some experimental data are included to show the validity of the friction-loss analysis. Finally, the utility of the analyses in design is demonstrated.

scholarly journals A Method of Predicting the Energy Losses in Vaneless Diffusers of Centrifugal Compressors

1989 ◽  
Author(s):  
Huashu Dou
Keyword(s):  
Experimental Data ◽  
Energy Loss ◽  
Total Energy ◽  
Wall Friction ◽  
Energy Losses ◽  
Flow Conditions ◽  
Centrifugal Compressors ◽  
Flow Losses ◽  
Vaneless Diffusers ◽  
Good Agreement

The flow losses in the veneless diffusers of centrifugal compressors is investigated. It is found that the total energy loss in vaneless diffusers is a function of Bsin2 α0 when inlet flow conditions and radius ratio between inlet and outlet are given. A wall friction coefficient equation is derived and a method of predicting the total energy loss excepting mixing loss is presented. A comparison is made between results obtained from this method and experimental data generated by the author as well as data from the literature. Good agreement is obtained.

scholarly journals ЗБІЛЬШЕННЯ ДІАПАЗОНУ СТІЙКОЇ РОБОТИ СТУПЕНЯ ВІДЦЕНТРОВОГО КОМПРЕСОРА З БЕЗЛОПАТКОВИМ ДИФУЗОРОМ

2019 ◽  
pp. 4-9
Author(s):  
Микола Васильович Калінкевич ◽  
Микола Іванович Радченко
Keyword(s):  
Mathematical Model ◽  
Gas Injection ◽  
Rotating Stall ◽  
Low Flow ◽  
Stable Operation ◽  
Vaneless Diffuser ◽  
Centrifugal Compressors ◽  
Flow Separation Control ◽  
Flow Part ◽  
Vaneless Diffusers

Centrifugal compressors often operate at different capacities, so it is important to ensure their stable operation over a wide flow range. Stages with vaneless diffusers have several advantages compared to stages with other types of diffusers: they are more technologically advanced to manufacture, and more uniform pressure distribution behind the impeller improves the dynamics of the rotor. At low flows, due to the occurrence of a rotating stall and surge, the efficiency of stages with vaneless diffusers rapidly decreases. The occurrence of unstable operating modes of centrifugal compressor stages at low flow rates is associated with the appearance of developed backflows in the flow part. To expand the range of stable operation of the stages, it is necessary to use methods of flow separation control. Separation of the flow can be controlled either by special profiling the flow part channels or by actively influencing the flow, for example, by injecting gas. To solve this problem, a mathematical model of the gas flow in a vaneless diffuser with gas injection is developed. The characteristics and parameters of the flow in the vaneless diffusers with various meridional profiles with and without injecting gas were calculated. A comparison of the calculated and experimental characteristics of the vaneless diffusers and flow parameters in diffusers with different geometries and with different injection modes confirms the adequacy of the mathematical model. Investigations have confirmed the possibility of improving the characteristics of the stages of centrifugal compressors through the use of vaneless diffusers and diffusers with gas injection. Gas injection diffusers extend the stable operation range of the stages. The use of gas injection in a vaneless diffuser allows reducing the power consumption during antisurge control in comparison with the widespread bypass suction system at the entrance to the impeller

Effect of Impeller-Extended Shrouds on Centrifugal Compressor Performance as a Function of Specific Speed

1983 ◽  
Vol 105 (3) ◽  
pp. 457-465 ◽  
Author(s):  
L. Sapiro
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Centrifugal Compressors ◽  
Gas Compression ◽  
Blade Tip ◽  
Compressor Performance ◽  
The Subject ◽  
Specific Speed ◽  
Vaneless Diffusers ◽  
Outside Diameter

Centrifugal compressors for gas compression applications usually employ low-pressure ratio, backward-swept impellers with vaneless diffusers. To increase the compressor flow range and speed, impeller blades are occasionally trimmed, resulting in an extended shroud configuration. The effect of extended front and back impeller shrouds on the performance of centrifugal compressors with vaneless diffusers, and the variation of this effect as a function of specific speed, is thus of concern and is the subject of this paper. An investigation was carried out on two backward-swept shrouded impellers of common blade tip and inducer hub diameters, but different inducer tip diameters (corresponding to low and high specific speeds), with the front and back shrouds extending 20 percent above the blade’s outside diameter.

scholarly journals Analysis of Rotating Stall in Vaneless Diffusers of Centrifugal Compressors

1980 ◽  
Author(s):  
Amr N. Abdelhamid
Keyword(s):  
Rotational Speed ◽  
High Speed ◽  
Equations Of Motion ◽  
Unsteady Flows ◽  
Rotating Stall ◽  
Radius Ratio ◽  
Centrifugal Compressors ◽  
Coupling Conditions ◽  
Flow Oscillations ◽  
Vaneless Diffusers

Self-excited flow oscillations in radial vaneless diffusers of centrifugal compressors are investigated analytically using the linearized equations of motion for unsteady flows. Solutions of the differential equations are made to satisfy boundary conditions at diffuser inlet and exit which in typical conversion systems represent the coupling between the diffuser and upstream and downstream components. The results indicate that the rotational speed of the stall pattern is dependent on the diffuser radius ratio and the coupling conditions between the impeller and the diffuser. It is shown that the dependence of the onset of the flow oscillations on the diffuser radius ratio is strong if the conditions at diffuser inlet are such that low speed rotating stall patterns are generated in the diffuser. Onset of high speed rotating stall patterns is more affected by the coupling conditions between the impeller and the diffuser than by the diffuser radius ratio.

scholarly journals The optimal gas dynamic design system of industrial centrifugal compressors based on Universal modeling method

2020 ◽  
Vol 178 ◽  
pp. 01028 ◽  
Author(s):  
Yuri Galerkin ◽  
Aleksey Rekstin ◽  
Aleksandr Drozdov ◽  
Kristina Soldatova ◽  
Olga Solovyeva ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Modeling Method ◽  
Design System ◽  
Centrifugal Compressors ◽  
Digital Twin ◽  
Stage Of Development ◽  
Multistage Compressors ◽  
Vaneless Diffusers ◽  
Model Features ◽  
2D And 3D

We present the modern stage of development of Universal Modeling Method, a complex of mathematical models and software for optimal design of centrifugal compressors - a new version of simplified mathematical model of efficiency and new software for variation calculations of multistage compressors. Based on this numerical calculation complex we have created a method for preliminary design of flow paths of stages - 2D and 3D impellers, vane and vaneless diffusers and return channels. The new, 9th version of its mathematical model features a quasi-3D calculation method of 2D and 3D impellers design, a new principle of pressure characteristic calculation, a new model of vaneless diffusers and much more. “Digital twin of a centrifugal compressor stage” and “3D compressor” software create digital descriptions of the flow part and its solid model (“digital twin”).

Effect of Impeller Extended Shrouds on Centrifugal Compressor Performance as a Function of Specific Speed

1982 ◽  
Author(s):  
L. Sapiro
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Centrifugal Compressors ◽  
Gas Compression ◽  
Blade Tip ◽  
Compressor Performance ◽  
The Subject ◽  
Specific Speed ◽  
Vaneless Diffusers ◽  
Outside Diameter

Centrifugal compressors for gas compression applications usually employ low-pressure ratio, backward-swept impellers with vaneless diffusers. To increase the compressor flow range and speed, impeller blades are occasionally trimmed, resulting in an extended shroud configuration. The effect of extended front and back impeller shrouds on the performance of centrifugal compressors with vaneless diffusers, and the variation of this effect as a function of specific speed, is thus of concern and is the subject of this paper. An investigation was carried out on two backward-swept shrouded impellers of common blade tip and inducer hub diameters, but different inducer tip diameters (corresponding to low and high specific speeds), with the front and back shrouds extending 20 percent above the blade’s outside diameter.

An Explicit, Non-Iterative, Single Equation Formulation for an Accurate One Dimensional Estimation of Vaneless Radial Diffusers in Turbomachines

2014 ◽  
Vol 31 (2) ◽  
pp. 113-122
Author(s):  
R. Amirante ◽  
F. De Bellis ◽  
E. Distaso ◽  
P. Tamburrano
Keyword(s):  
Angular Momentum ◽  
Classical Theory ◽  
Conservation Law ◽  
Fluid Dynamic ◽  
Tangential Velocity ◽  
Pressure Recovery ◽  
Preliminary Design ◽  
Centrifugal Compressors ◽  
One Dimensional ◽  
Vaneless Diffusers

AbstractThe present paper proposes a very simple one dimensional (1-D) model that accounts for the energy loss caused by the fluid dynamic losses occurring in the vaneless diffusers of centrifugal compressors and pumps. Usually, the present techniques to design turbomachines (pumps, compressors and turbines) emphasize numerical methods and their use is relatively complex because several parameters need to be chosen and a lot of time is required to perform the calculation. For this reason, it is relevant to perform an accurate preliminary design to simplify the numerical computation phase and to choose a very good initial geometry to be used for accelerating and improving the search for the definitive geometry. However, today 1-D modeling is based on the classical theory that assumes that the angular momentum is conserved inside a vaneless diffuser, although the flow evolution is considered as non-isentropic. This means that fluid-dynamic losses are taken into account only for what concerns pressure recovery, whereas the evaluation of the outlet tangential velocity incoherently follows an ideal behavior. Starting from such considerations, a new conservation law for the angular momentum is analytically derived, which incorporates the same fluid-dynamic losses modeled by the thermodynamic transformation law that is employed for correlating pressure recovery with enthalpy increase. Similar arguments hold for incompressible flows. Detailed and very accurate three-dimensional flow simulations are employed to analyze if the new model is capable of predicting the outlet tangential velocity more accurately than the classical theory. Results provided for both compressible (centrifugal compressors) and incompressible (centrifugal pumps) flows and for different inlet velocity profiles show a significant accuracy improvement of the new conservation law in the prediction of the outlet flow conditions when compared with the classical theory, thus demonstrating that the proposed model can be employed in the preliminary design of vaneless diffusers (i.e., in the estimation of the outlet diameter) more effectively than the classical ideal theory. Furthermore, the model is validated against industrial experimental campaigns. Even further experimental data, reported in a previous paper by the same authors, confirm the reliability of the employed approach.

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