An Object-Oriented CFD Code for Optimization of High Pressure Ratio Compressors

2012 ◽  
Author(s):  
Elmar Gröschel ◽  
Benjamin Rembold ◽  
Luca Mangani ◽  
Ernesto Casartelli
Keyword(s):  
Optimization Design ◽  
Compressible Flows ◽  
State Of The Art ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Object Oriented ◽  
Special Treatment ◽  
3D Flow ◽  
High Pressure Ratio ◽  
Flow Features

The flow fields and performances of different transonic radial compressors of varying geometries and conceptual designs have been studied numerically. All the simulations were performed with a modified in-house 3D RANS solver based on an object-oriented open-source library. The solver uses an All-Mach algorithm with a special treatment for the pressure corrector equation to deal with highly compressible flows. The 3D flow field structures, the characteristics and integral quantities have been compared to the results of established, state-of-the-art commercial solvers as well as to measurements whenever possible. This paper demonstrates for various configurations that the main flow features and the flow characteristics have been captured by the new solver. Furthermore, the new solver is also capable of computing the delta variations of similar designs. This is an essential step for the broad application of the new solver for optimization design cycles.

Assessment of Various Turbulence Models in a High Pressure Ratio Centrifugal Compressor With an Object Oriented CFD Code

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
Luca Mangani ◽  
Ernesto Casartelli ◽  
Sebastiano Mauri
Keyword(s):  
Boundary Layer ◽  
High Pressure ◽  
Pressure Gradient ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Turbulence Models ◽  
Object Oriented ◽  
Adverse Pressure Gradient ◽  
High Mass ◽  
High Pressure Ratio

The flow field in a high pressure ratio centrifugal compressor with a vaneless diffuser has been investigated numerically. The main goal is to assess the influence of various turbulence models suitable for internal flows with an adverse pressure gradient. The numerical analysis is performed with a 3D RANS in-house modified solver based on an object-oriented open-source library. According to previous studies from varying authors, the turbulence model is believed to be the key parameter for the discrepancy between experimental and numerical results, especially at high pressure ratios and high mass-flow. Particular care has been taken at the wall, where a detailed integration of the boundary layer has been applied. The results present different comparisons between the models and experimental data, showing the influence of using advanced turbulence models. This is done in order to capture the boundary layer behavior, especially in large adverse pressure gradient single stage machinery.

Numerical Investigation of Impeller Tip Tailoring and its Impact on Aerodynamic Design of a Centrifugal Compressor’s Impeller

2014 ◽  
Author(s):  
Ashvin Mahajan ◽  
Lieven Baert ◽  
Michaël Leborgne ◽  
Timothée Lonfils ◽  
I. Gede Parwatha ◽  
...  
Keyword(s):  
Design Optimization ◽  
Significant Contribution ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Aerodynamic Design ◽  
High Pressure Ratio ◽  
Important Improvement ◽  
Geometrical Features ◽  
Isentropic Efficiency

The current research focuses on the aerodynamic design of a centrifugal compressor and the effect of tip tailoring on the aerodynamic impeller efficiency. To this extent a high-fidelity multi-point design optimization process has been developed and exploited on a high pressure ratio transonic impeller. By manipulating the shape of the impeller blades and endwalls and by including advanced geometrical features such as winglets on the impeller blades, the behavior of the impeller flow has been investigated. Here, the results of three-dimensional RANS simulations with the Spalart-Allmaras turbulence model on a structured multi-block mesh is used for the evaluation of the flow characteristics. In the context of radial machines, the results of the aerodynamic design optimization show an important improvement of the impeller isentropic efficiency compared to the reference impeller, with a significant contribution from the presence of the impeller tip winglets. Furthermore, the integration of the impeller winglet has encouraged this study to provide a detailed analysis on the impeller flow structures in order to have a better understanding of the effects of tip tailoring on impeller performance.

An Investigation of the Flow Structure in the Radial Inflow Transonic Turbine

2015 ◽  
Author(s):  
Cheng Zhu ◽  
Weilin Zhuge ◽  
Yangjun Zhang
Keyword(s):  
High Pressure ◽  
Secondary Flow ◽  
Flow Structure ◽  
Cross Sections ◽  
Low Cost ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Horseshoe Vortex ◽  
High Pressure Ratio ◽  
Transonic Turbine

Radial inflow turbines which are an important component of a turbocharger consist essentially of a volute, a rotor and a diffuser. Vaneless volute turbines, which have reasonable performance and low cost, are the most widely used in turbochargers for automotive engines. In recent years the growing necessity of increasing specific output power of turbochargers has encouraged the design of high pressure ratio turbine stage. Two stage turbines, which can achieve the high pressure ratio require, are not suitable to for these applications due to volume and weight increases. The common design trend is thus to use single stage high pressure ratio radial transonic turbine. This paper describes numerical investigations of the flow fields in a radial inflow transonic turbine whose design pressure ratio is 4. The S-A turbulence model and Jameson’s center scheme have been applied in order to get good viscous resolution, accuracy and computing efficiency. Limiting streamlines on the wall surface as well as different flow characteristics, such as entropy generation of the cross sections, were evaluated, and detailed endwall flow and secondary flow structure were analyzed. The development of different vortex, especially the tip leakage vortex, vortex caused by the shock wave, passage vortex and horseshoe vortex were discussed. The results have shown that there is a great secondary flow feature and complicated vortex system in the high pressure ratio radial inflow transonic turbine.

Eliminating Static Pressure Distortion by a Large Cut Back Tongue Volute

2006 ◽  
Author(s):  
C. Xu ◽  
R. S. Amano
Keyword(s):  
High Pressure ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Experimental Studies ◽  
Flow Characteristics ◽  
Flow Structures ◽  
High Pressure Ratio ◽  
Compressor Performance ◽  
Stationary Frame ◽  
Good Agreement

This paper presents a physical solution by eliminating static pressure distortions of impeller exit due to a volute in a centrifugal compressor. The numerical and experimental studies on the circumferential distortion flow characteristics inside the stationary frame of a high-pressure ratio compressor with a large cut back tongue volute. The detailed flow structures and pressure distortions development inside the stationary components are discussed. The numerical results were demonstrated to be in good agreement with the experiments. The volute and diffuser interactions at design and off-design conditions were found to be much smaller for the large cut back volute in comparison with the reported from literature. The study indicated that the large cut back tongue volute design not only benefits the compressor performance but also reduces the impeller exit static pressure non-uniformity caused by discharge volute.

Spring Stiffness Selection Criteria for Nozzle Check Valves Employed in Compressor Stations

2011 ◽  
Vol 133 (12) ◽  
Author(s):  
K. K. Botros
Keyword(s):  
Selection Criteria ◽  
Hydrodynamic Force ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Check Valve ◽  
Compressor Station ◽  
Force Coefficient ◽  
Minimum Flow ◽  
High Pressure Ratio ◽  
Open Position

Nozzle type check valves are often employed in compressor stations in three locations: compressor outlet, station discharge, and station bypass. The fundamental design concept of these valves is based on creating a converging diverging flow through the valve internal geometry such that a minimum area is achieved at a location corresponding to the back of the check valve disk at the fully open position. This will ensure maximum hydrodynamic force coefficient which allows the valve to be fully open with minimum flow. Spring forces and stiffness determine the performance of this type of check valves and impact the overall operation and integrity of the compressor station. This paper examines the effects of various spring characteristics and stiffness in relation to the compressor and station flow characteristics. The results show that when the spring forces are higher than the maximum hydrodynamic force at minimum flow, the disk will not be at the fully open position, which will give rise to disk fluttering and potential for cyclic high velocity impact between components of the internal valve assembly. This could lead to self destruction of the check valve and subsequent risk of damage to the compressor unit itself. The paper also points to the fact that the spring selection criteria for a unit check valve are different than that for station and bypass check valves. An example of a case study with actual field data from a high pressure ratio compressor station employing this type of check valves is presented to illustrate the associated dynamic phenomena and fluid-structure interaction within the internal assembly of the check valve.

Comparing Water (R718) to Other Refrigerants

2006 ◽  
Author(s):  
Amir A. Kharazi ◽  
Norbert Mu¨ller
Keyword(s):  
High Pressure ◽  
Water Vapor ◽  
State Of The Art ◽  
Pressure Ratio ◽  
Cooling Capacity ◽  
Specific Work ◽  
High Pressure Ratio ◽  
Current State ◽  
Two Factors ◽  
Volumetric Cooling

Even though water (R718) is one of the oldest refrigerants, state of the art technology is required to use water as a refrigerant in compression refrigeration plants with turbo compressors. To compare water (R718) to other refrigerants, a code is developed in which all refrigerants can be compared in a single p-h, T-s, or p-T diagram. Using the code, the COP isolines of water (R718) and any refrigerant can be generated in a graph to determine which refrigerant has a better COP for a certain evaporation temperature and temperature lift. In regard to using water (R718) as a refrigerant, some specific features complicate its application in refrigeration plants with turbo compressors. Because the cycle works at very low pressure, the volumetric cooling capacity of water vapor is very low. Hence, huge volume flows have to be compressed with relatively high pressure ratios. Therefore, the use of water (R718) as a refrigerant, compared to classical refrigerants, such as R134a or R12, requires approximately 200 times the volume flow, and about twice the pressure ratio for the same applications. Because of the thermodynamic properties of water vapor, this high pressure ratio requires approximately a two to four times higher compressor tip speed, depending on the impeller design; while the speed of sound is approximately 2.5 times higher. Reynolds numbers are about 300 times lower and the specific work transmission per unit of mass has to be around 15 times higher. Two factors are introduced to compare the irreversibilities of R718 and other refrigerants and the main source of irrevercibility in R718 cycle is identified. Finally, the current state-of-the-art R718 is reviewed.

The Development of Centrifugal Compressor Impeller

2008 ◽  
Author(s):  
C. Xu ◽  
R. S. Amano
Keyword(s):  
Centrifugal Compressor ◽  
State Of The Art ◽  
Pressure Ratio ◽  
Structure Design ◽  
Centrifugal Compressors ◽  
Rotating Speed ◽  
Operating Range ◽  
High Pressure Ratio ◽  
Current State ◽  
Compressor Impeller

Impeller is one of the key components of industrial centrifugal compressors and turbochargers. Aerodynamic and structure designs of the impeller are critical to the success of the whole compressor stages. The requirements for efficiency and operating range of industrial centrifugal compressors and turbochargers have been increased dramatically compared with the situation in the past. The efficiency of newly developed low-pressure ratio centrifugal compressor has reached the possible level of the machine. However, the efficiency level of intermediate and high-pressure ratio machine still have gap between the current state-of-the-art and possible level. The challenge for centrifugal compressor design is to keep the efficiency level at state-of-the-art and increase the compressor operating range. Increase of the compressor operating range without sacrificing compressor peak efficiency is difficult to achieve. The product globalization requires one product design, which can be used in all locations. In some counties, due to the technology differences, electricity frequencies variations could be 10%. Turbocharger compressors work at different rotational speeds for majority of the time. The compressor impeller rotating speeds change in certain range. The impeller rotating speed variation makes the impeller structure design more challenging. In this study, a full-3D impeller was designed to optimize impeller aerodynamic performance and structure characteristics.

Assessment of Various Turbulence Models in a High Pressure Ratio Centrifugal Compressor With an Object Oriented CFD Code

2011 ◽  
Author(s):  
Luca Mangani ◽  
Ernesto Casartelli ◽  
Sebastiano Mauri
Keyword(s):  
Boundary Layer ◽  
High Pressure ◽  
Pressure Gradient ◽  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Turbulence Models ◽  
Object Oriented ◽  
Adverse Pressure Gradient ◽  
High Mass ◽  
High Pressure Ratio

The flow field in a high pressure ratio centrifugal compressor with vaneless diffuser has been investigated numerically. Main goal is to assess the influence of various turbulence models suitable for internal flows with adverse pressure gradient. The numerical analysis is performed with a 3D RANS in-house modified solver based on an object-oriented open-source library. According to previous studies from varying authors, the turbulence model is believed to be the key parameter for the discrepancy between experimental and numerical results, especially at high pressure ratios and high mass-flow. Particular care has been taken at the wall, where a detailed integration of the boundary layer has been applied. The results presents different comparisons between the models and experimental data showing the influence of using advanced turbulence models. This is done in order to capture the boundary layer behavior, especially in large adverse pressure gradient single stage machinery.

Multi-Objective Aerodynamic Optimization Design and Data Mining of a High Pressure Ratio Centrifugal Impeller

2015 ◽  
Vol 137 (9) ◽  
Author(s):  
Zhendong Guo ◽  
Liming Song ◽  
Zhiming Zhou ◽  
Jun Li ◽  
Zhenping Feng
Keyword(s):  
Data Mining ◽  
High Pressure ◽  
Optimization Design ◽  
Pressure Ratio ◽  
Differential Evolution Algorithm ◽  
Centrifugal Impeller ◽  
Pareto Solutions ◽  
Aerodynamic Optimization ◽  
Multi Objective ◽  
High Pressure Ratio

An automated three-dimensional multi-objective optimization and data mining method is presented by integrating a self-adaptive multi-objective differential evolution algorithm (SMODE), 3D parameterization method for blade profile and meridional channel, Reynolds-averaged Navier–Stokes (RANS) solver technique and data mining technique of self-organizing map (SOM). Using this method, redesign of a high pressure ratio centrifugal impeller is conducted. After optimization, 16 optimal Pareto solutions are obtained. Detailed aerodynamic analysis indicates that the aerodynamic performance of the optimal Pareto solutions is greatly improved. By SOM-based data mining on optimized solutions, the interactions among objective functions and significant design variables are analyzed. The mechanism behind parameter interactions is also analyzed by comparing the data mining results with the performance of typical designs.

Inlet and Exit Flow Characteristics of Mixed Flow Turbines

1998 ◽  
Author(s):  
C. Arcoumanis ◽  
R. F. Martinez-Botas ◽  
J. M. Nouri ◽  
C. C. Su
Keyword(s):  
Incidence Angle ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Expansion Ratio ◽  
Superior Performance ◽  
Mixed Flow ◽  
Flow Angle ◽  
High Pressure Ratio ◽  
Swirl Angle ◽  
Design Speed

The steady performance of mainly two high pressure ratio mixed flow turbines for an automotive turbocharger (expansion ratio of 2.9) has been investigated and the results indicated superior performance of the rotor with a constant inlet blade angle relative to that with a nominally constant incidence angle. These results have been confirmed by the measurement of the three components of velocity, the Reynolds normal stresses and the flow angle at the inlet and exit of the mixed-flow turbine rotors by laser Doppler velocimetry (LDV) under steady state conditions. The turbine testing conditions corresponded to the 50% and 70% design speeds, equivalent to 29,400 and 41,300 rpm respectively. The velocity results have indicated that the flow upstream of the rotor varies significantly along the blade inlet plane, and this is more evident at the 50% design speed. The flow in the volute behaves as a free vortex except in regions close to the hub, while the exit flow revealed that the constant incidence design rotor has a significantly higher exit swirl angle than the constant blade design, in agreement with the higher exit kinetic energy loss in the former case.

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