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.

Selection Criteria of Spring Stiffness for Nozzle Type Check Valves in Compressor Station Applications

2011 ◽  
Author(s):  
K. K. Botros
Keyword(s):  
Selection Criteria ◽  
Hydrodynamic Force ◽  
Pressure Ratio ◽  
Check Valve ◽  
Compressor Station ◽  
Force Coefficient ◽  
Minimum Flow ◽  
Open Position ◽  
Type Check ◽  
Nozzle Type

Nozzle type check valves are often employed in compressor stations in three locations: compressor outlet, station discharge and station by-pass. 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 disc at 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 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 disc will not be at fully open position, which will give rise to disc 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.

Single Versus Dual Recycle System Dynamics of High Pressure Ratio, Low Inertia Centrifugal Compressor Stations

2011 ◽  
Vol 133 (12) ◽  
Author(s):  
K. K. Botros
Keyword(s):  
High Pressure ◽  
Centrifugal Compressor ◽  
Dynamic Instability ◽  
Pressure Ratio ◽  
Check Valve ◽  
Analytical Methodology ◽  
High Pressure Ratio ◽  
Compressor Surge ◽  
Rapid Transients ◽  
Single Versus

Compression systems are designed and operated in a manner to eliminate or minimize the potential for surge, which is a dynamic instability that is very detrimental to the integrity of the compressor unit. Compressor surge can occur when compressors are subjected to rapid transients such as those occurring following an emergency shutdown (ESD) or a power failure, which in turn, requires fast reaction. To prevent this from occurring, compressor stations are designed with single or dual recycle systems with recycle valves, which are required to open upon ESD. There has been extensive debate and confusion as to whether a single recycle or a dual recycle system is required and the circumstances and the conditions under which one system or the other must be used. This paper discusses this crucial design issue in detail and highlights the parameters affecting the decision to employ either system, particularly for high pressure ratio, low inertia compressors. Parameters such as gas volume capacitance (V) in the recycle path, compressor power train inertia, compressor performance characteristics, the recycle valve coefficient (Cv), prestroke and stroke time, and check valve dynamic characteristic are crucial in determining the conditions for dynamic instabilities. A simple analytical methodology based on the perturbation theory is developed that provides a first-cut analysis to determine if a single recycle system is adequate for a given compression system. The concept of an inertia number is then introduced with a threshold value that determines which recycle system to use. Techniques to circumvent compressor surge following ESD are discussed and their respective effectiveness are highlighted including when and if a delay in the fuel cutoff will be effective. An example of a case study with actual field data of a high pressure ratio centrifugal compressor employed in a natural gas compressor station is presented to illustrate the fundamental concept of single versus dual recycle systems.

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.

Single vs. Dual Recycle System Requirements in the Design of High Pressure Ratio, Low Inertia Centrifugal Compressor Stations

2011 ◽  
Author(s):  
K. K. Botros
Keyword(s):  
High Pressure ◽  
Centrifugal Compressor ◽  
Dynamic Instability ◽  
Pressure Ratio ◽  
Check Valve ◽  
Threshold Value ◽  
Analytical Methodology ◽  
High Pressure Ratio ◽  
Compressor Surge ◽  
Rapid Transients

Compression systems are designed and operated in a manner to eliminate or minimize the potential for surge, which is a dynamic instability that is very detrimental to the integrity of the compressor unit. Compressor surge can occur when compressors are subjected to rapid transients such as those occurring following an emergency shutdown (ESD) or a power failure, which in turn, requires fast reaction. To prevent this from occurring, compressor stations are designed with single or dual recycle systems with recycle valves, which are required to open upon ESD. There has been extensive debate and confusion as to whether a single recycle or a dual recycle system is required and the circumstances and the conditions under which one system or the other must be used. This paper discusses this crucial design issue in detail and highlights the parameters affecting the decision to employ either system, particularly for high pressure ratio, low inertia compressors. Parameters such as gas volume capacitance (V) in the recycle path, compressor power train inertia, compressor performance characteristics, the recycle valve coefficient (Cv), pre-stroke and stroke time, and check valve dynamic characteristic are crucial in determining the conditions for dynamic instabilities. A simple analytical methodology based on the perturbation theory is developed that provides a first-cut analysis to determine if a single recycle system is adequate for a given compression system. The concept of an inertia number is then introduced with a threshold value that determines which recycle system to use. Techniques to circumvent compressor surge following ESD are discussed and their respective effectiveness are highlighted including when and if a delay in the fuel cut-off will be effective. An example of a Case study with actual field data of a high pressure ratio centrifugal compressor employed in a natural gas compressor station is presented to illustrate the fundamental concept of single vs. dual recycle systems.

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.

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.

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.

Investigation of the Secondary Flow Structure in the Mixed Flow Turbine for a High Pressure Ratio Turbocharger

2008 ◽  
Author(s):  
Li Chen ◽  
Weilin Zhuge ◽  
Yangjun Zhang ◽  
Shuyong Zhang ◽  
Jizhong Zhang
Keyword(s):  
High Pressure ◽  
Secondary Flow ◽  
Flow Structure ◽  
Cross Sections ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Horseshoe Vortex ◽  
Mixed Flow ◽  
High Pressure Ratio ◽  
Secondary Flow Structure

A numerical investigation into aerodynamic features of the mixed flow turbine used in a high pressure ratio turbocharger was conducted. 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, while detailed endwall flow and secondary flow structure were analyzed. The development of different vortex, especially the tip leakage vortex, 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 mixed flow turbine.

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