An Analytical Model of Axial Compressor Off-Design Performance

1994 ◽  
Vol 116 (3) ◽  
pp. 425-434 ◽  
Author(s):  
T. R. Camp ◽  
J. H. Horlock
Keyword(s):  
Design Process ◽  
Axial Compressor ◽  
Axial Flow ◽  
Operating Conditions ◽  
Flow Coefficient ◽  
Design Stage ◽  
Turbine Engine ◽  
Design Performance ◽  
Design Value ◽  
Stage Matching

An analysis is presented of the off-design performance of multistage axial-flow compressors. It is based on an analytical solution, valid for small perturbations in operating conditions from the design point, and provides an insight into the effects of choices made during the compressor design process on performance and off-design stage matching. It is shown that the mean design value of stage loading coefficient (ψ = Δh0/U2) has a dominant effect on off-design performance, whereas the stage-wise distribution of stage loading coefficient and the design value of flow coefficient have little influence. The powerful effects of variable stator vanes on stage-matching are also demonstrated and these results are shown to agree well with previous work. The slope of the working line of a gas turbine engine, overlaid on overall compressor characteristics, is shown to have a strong effect on the off-design stage-matching through the compressor. The model is also used to analyze design changes to the compressor geometry and to show how errors in estimates of annulus blockage, decided during the design process, have less effect on compressor performance than has previously been thought.

scholarly journals An Analytical Model of Axial Compressor Off-Design Performance

1993 ◽  
Author(s):  
T. R. Camp ◽  
J. H. Horlock
Keyword(s):  
Design Process ◽  
Axial Compressor ◽  
Axial Flow ◽  
Operating Conditions ◽  
Flow Coefficient ◽  
Design Stage ◽  
Turbine Engine ◽  
Design Performance ◽  
Design Value ◽  
Stage Matching

An analysis is presented of the off-design performance of multistage axial-flow compressors. It is based on an analytical solution, valid for small perturbations in operating conditions from the design point, and provides an insight into the effects of choices made during the compressor design process on performance and off-design stage matching. It is shown that the mean design value of stage loading coefficient (ψ = Δho/U2) has a dominant effect on off-design performance, whereas the stage-wise distribution of stage loading coefficient and the design value of flow coefficient have little influence. The powerful effects of variable stator vanes on stage-matching are also demonstrated and these results are shown to agree well with previous work. The slope of the working line of a gas turbine engine, overlaid on overall compressor characteristics, is shown to have a strong effect on the off-design stage-matching through the compressor. The model is also used to analyse design changes to the compressor geometry and to show how errors in estimates of annulus blockage, decided during the design process, have less effect of compressor performance than has previously been thought.

Optimum Design and Sensitivity Analysis of Axial Flow Compressor With Combination of Analytical Method, Qualitative and Quantitative Rules and Genetic Algorithm

2008 ◽  
Author(s):  
Mohsen Reza Soltani ◽  
Hiwa Khaledi ◽  
Mohammad Bagher Ghofrani ◽  
Amir Abbas Rezaei
Keyword(s):  
Genetic Algorithm ◽  
Gas Turbine ◽  
Design Process ◽  
Axial Flow ◽  
Design Stage ◽  
Actual Behavior ◽  
Combustion Chambers ◽  
Qualitative And Quantitative ◽  
Stage Matching ◽  
Flow Compressor

Simulation and prediction of gas turbine performance is a very important issue in design process or in actual behavior analysis. In these models physical behavior of components such as compressors, combustion chambers and turbines are simulated related to each other. The compressor is the most important part of simulation. This paper presents a model for simulating a compressor using stage stacking procedure with the aid of a genetic algorithm. The most important feature of the proposed method is that qualitative and quantitative rules based on turbo-machinery knowledge of compressors are used as constraints to the genetic algorithm to find the corrected situations of design. This knowledge is evaluated with both industrial and aero gas turbine engines (501F & CF6 (LM2500)). The model is based on an analytical solution and provides an insight into the effects of choices made during the compressor design process on performance and off-design stage matching. The results of the model highlight the capability of the method which accurately reproduces the available data. In addition to obtaining design conditions, this model can find and calculate stages that are highly loaded and this information is vital to control the compressor.

Improved criteria for stall-free preliminary design of axial compressor of aero gas turbine engines

2018 ◽  
Vol 233 (9) ◽  
pp. 3286-3297 ◽  
Author(s):  
MR Aligoodarz ◽  
A Mehrpanahi ◽  
M Moshtaghzadeh ◽  
A Hashiehbaf
Keyword(s):  
Gas Turbine ◽  
Large Scale ◽  
Axial Compressor ◽  
Axial Flow ◽  
Design Criterion ◽  
Flow Coefficient ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Parameter Ranges ◽  
Axial Flow Compressors

A worldwide effort has been devoted to developing highly efficient and reliable gas turbine engines. There exist many prominent factors in the development of these engines. One of the most important features of the optimal design of axial flow compressors is satisfying the allowable range for various parameters such as flow coefficient, stage loading, the degree of reaction, De-Haller number, etc. But, there are some applicable cases that the mentioned criteria are exceeded. One of the most famous parameters is De-Haller number, which according to literature data should not be kept less than 0.72 in any stage of the axial compressor. A deep insight into the current small- or large-scale axial flow compressors shows that a discrepancy will occur among design criterion for De-Haller number and experimental measurements in which the De-Haller number is less than the design limit but no stall or surge is observed. In this paper, an improved formulation is derived based on one-dimensional modeling for predicting the stall-free design parameter ranges especially stage loading, flow coefficient, etc. for various combinations. It was found that the current criterion is much more accurate than the De-Haller criterion for design purposes.

Prestall Instability in Axial Flow Compressors

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Mario Eck ◽  
Roland Rückert ◽  
Dieter Peitsch ◽  
Marc Lehmann
Keyword(s):  
Pressure Fluctuations ◽  
Axial Compressor ◽  
Axial Flow ◽  
Leading Edge ◽  
Propagation Speed ◽  
Flow Coefficient ◽  
Spectral Signature ◽  
Time Resolved ◽  
Pressure Transducers ◽  
Flow Disturbances

Abstract The aim of the present paper is to improve the physical understanding of discrete prestall flow disturbances developing in the tip area of the compressor rotor. For this purpose, a complementary instrumentation was used in a single-stage axial compressor. A set of pressure transducers evenly distributed along the circumference surface mounted in the casing near the rotor tip leading edges measures the time-resolved wall pressures simultaneously to an array of transducers recording the chordwise static pressures. The latter allows for plotting quasi-instantaneous casing pressure contours. Any occurring flow disturbances can be properly classified using validated frequency analysis methods applied to the data from the circumferential sensors. While leaving the flow coefficient constant, a continuously changing number of prestall flow disturbances appears to be causing a unique spectral signature, which is known from investigations on rotating instability. Any arising number of disturbances is matching a specific mode order found within this signature. While the flow coefficient is reduced, the propagation speed of prestall disturbances increases linearly, and meanwhile, the speed seems to be independent from the clearance size. Casing contour plots phase-locked to the rotor additionally provide a strong hint on prestall disturbances clearly not to be caused by a leading edge separation. Data taken beyond the stalling limit demonstrate a complex superposition of stall cells and flow disturbances, which the title “prestall disturbance” therefore does not fit to precisely any more. Different convection speeds allow the phenomena to be clearly distinguished from each other. Furthermore, statistical analysis of the pressure fluctuations caused by the prestall disturbances offer the potential to use them as a stall precursor or to quantify the deterioration of the clearance height between the rotor blade tips and the casing wall during the lifetime of an engine.

Complex Gas Dynamic Optimization of a Three Spool Axial Compressor of an Industrial Gas Turbine Engine

2019 ◽  
Author(s):  
Grigorii M. Popov ◽  
Igor Egorov ◽  
Dmitrii Dmitriev ◽  
Evgenii S. Goriachkin ◽  
Andrei A. Volkov
Keyword(s):  
Dynamic Optimization ◽  
Axial Compressor ◽  
Operating Conditions ◽  
Specific Task ◽  
Turbine Engine ◽  
Gas Dynamic ◽  
Impressive Result ◽  
Complex Models ◽  
Overall Efficiency ◽  
Industrial Gas Turbine

Abstract The paper provides a description of the algorithm, an example of a specific task, and the results of the optimization of a 15-stage three-spool compressor for a ground-based GTU by the efficiency criteria of the engine. It can be performed by using the proposed algorithm to find such a compressor configuration that will be not just the optimum compressor, but the best option for working as part of the engine under the specified operating conditions and with various types of required restrictions. Using the proposed algorithm, varying only the stagger angles of the profiles, the authors managed to find a way to increase the overall efficiency of the NK-36ST engine by 0.43%. Obviously, it is possible to achieve a more impressive result and at the same time to increase reliability, reduce the weight and cost of the engine by applying more complex models by changing the shape of the blade profiles.

An Axial Flow Compressor for Operation With Humid Air and Water Injection

2011 ◽  
Vol 133 (7) ◽  
Author(s):  
Jesuino Takachi Tomita ◽  
Luciano Porto Bontempo ◽  
João Roberto Barbosa
Keyword(s):  
Computer Program ◽  
Water Injection ◽  
Axial Flow ◽  
Operating Conditions ◽  
Axial Position ◽  
Design Stage ◽  
Viscous Effects ◽  
Humid Air ◽  
Axial Flow Compressor ◽  
Flow Compressor

The first steps of the turbomachinery design usually rely on numerical tools based on inviscid formulation with corrections using loss models to account for viscous effects, secondary flows, tip clearances, and shock waves. The viscous effects are accounted for using semi-empirical correlations especially assembled for the chosen airfoils and range of operating conditions. Fast convergence and good accuracy are required from such design procedures. There are successful models that produce very accurate performance prediction. Among the methodologies commonly used, the streamline curvature (SLC) is used since those characteristics and the most important properties can be calculated reasonably well at any radial positions, assisting other more complex analysis programs. The SLC technique is, therefore, well suited for the design of axial flow compressors for reasons such as quick access to vital flow properties at the blade edges from which actions may be taken to improve its performance at the design stage. This work reports the association of a SLC computer program and commercial software for comparison purposes, as well as for grid generation required by a full 3D, turbulent Navier–Stokes computer program used for flow calculation in the blade passages. Application to a high performance three-stage axial flow compressor with inlet guide vane demonstrates the methodology adopted. The SLC program is also capable of calculating the compressor performance with humid air and water injection at any axial position along the compressor. The influence of water injection at different axial positions, water particle diameter, and temperature of water particles were studied for different humid air conditions. The positions of the evaporating water particles were calculated using their thermophysical and dynamic properties along the compressor.

Effect of the Stator Hub Configuration and Stage Design Parameters on Aerodynamic Loss in Axial Compressors

2014 ◽  
Author(s):  
Sungho Yoon ◽  
Rudolf Selmeier ◽  
Patricia Cargill ◽  
Peter Wood
Keyword(s):  
Pressure Loss ◽  
Axial Compressor ◽  
Flow Coefficient ◽  
Design Stage ◽  
Design Parameters ◽  
Leakage Flow ◽  
Design Decision ◽  
Leakage Loss ◽  
Stage Design ◽  
Degree Of Reaction

The choice of the stator hub configuration (i.e. cantilevered versus shrouded) is an important design decision in the preliminary design stage of an axial compressor. Therefore, it is important to understand the effect of the stator hub configuration on the aerodynamic performance. In particular, the stator hub configuration fundamentally affects the leakage flow across the stator. The effect of the stator hub configuration on the leakage flow and its consequent aerodynamic mixing loss with the main flow within the stator row is systematically investigated in this study. In the first part of the paper, a simple model is formulated to estimate the leakage loss across the stator hub as a function of fundamental stage design parameters, such as the flow coefficient, the degree of reaction and the work coefficient, in combination with some relevant geometric parameters including the clearance/span, the pitch-to-chord ratio and the number of seals for the shrouded geometry. The model is exercised in order to understand the effect of each of these design parameters on the leakage loss. It is found that, for a given flow coefficient and work coefficient, the leakage loss across the stator is substantially influenced by the degree of reaction. When a cantilevered stator is compared with a shrouded stator with a single seal at the same clearance, it is shown that a shrouded configuration is generally favored as a higher degree of reaction is selected, whereas a cantilevered configuration is desirable for a lower degree of reaction. Further to this, it is demonstrated that, for shrouded stators, an additional aerodynamic benefit can be achieved by using multiple seals. The second part of the paper investigates the effect of the rotating surfaces. Traditionally, only the pressure loss has been considered for stators. However, the current advanced CFD generally includes the leakage path with associated rotating surfaces, which impart energy to the flow. It is shown that the conventional loss coefficient, based on considering only the pressure loss, is misleading when hub leakage flows are modeled in detail, because there is energy addition due to the rotation of the hub or the shroud seals for the cantilevered stator and the shrouded stator, respectively. The calculation of the entropy generation across the stator is a better measure of relative performance when comparing two different stator hub configurations with detailed CFD.

scholarly journals Preliminary Design of Multistage Radial Turbines Based on Rotor Loss Characteristics under Variable Operating Conditions

Energies ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2550 ◽  
Author(s):  
Zheming Tong ◽  
Zhewu Cheng ◽  
Shuiguang Tong
Keyword(s):  
Guide Vane ◽  
Operating Conditions ◽  
Flow Angle ◽  
Design Performance ◽  
Outlet Flow ◽  
Design Value ◽  
Radial Turbines ◽  
Rotor Loss ◽  
Variable Operating Conditions ◽  
Early Design Phase

The loading-to-flow diagram is a widely used classical method for the preliminary design of radial turbines. This study improves this method to optimize the design of radial turbines in the early design phase under variable operating conditions. The guide vane outlet flow angle is a key factor affecting the off-design performance of the radial turbine. To optimize the off-design performance of radial turbines in the early design phase, we propose a hypothesis that uses the ratio of the mean velocity of the fluid relative to the rotor passage with respect to the circumferential velocity of the rotor as an indicator to indirectly and qualitatively estimate the rotor loss, as it plays a key role in the off-design efficiency. Theoretical analysis of rotor loss characteristics under different types of variable operating conditions shows that a smaller design value of guide vane outlet flow angle results in a better off-design performance in the case of a reduced mass flow. In contrast, radial turbines with a larger design value of guide vane outlet flow angle can obtain a better off-design performance with increased mass flow. The above findings were validated with a mean-line model method. Furthermore, this study discusses the optimization of the design value of guide vane outlet flow angle based on the matching of rotor loss characteristics with specified variable operating conditions. It provides important guidance for the design optimization of multistage radial turbines with variable operating conditions in compressed air energy storage (CAES) systems.

Deciding Degree of Conservativeness in Initial Design Considering Risk of Future Redesign

2016 ◽  
Vol 138 (11) ◽  
Author(s):  
Nathaniel B. Price ◽  
Nam-Ho Kim ◽  
Raphael T. Haftka ◽  
Mathieu Balesdent ◽  
Sébastien Defoort ◽  
...  
Keyword(s):  
Design Process ◽  
Model Uncertainty ◽  
Epistemic Uncertainty ◽  
Design Stage ◽  
High Fidelity ◽  
Design Performance ◽  
Initial Design ◽  
Final Design ◽  
Fidelity Model ◽  
Epistemic Model

Early in the design process, there is often mixed epistemic model uncertainty and aleatory parameter uncertainty. Later in the design process, the results of high-fidelity simulations or experiments will reduce epistemic model uncertainty and may trigger a redesign process. Redesign is undesirable because it is associated with costs and delays; however, it is also an opportunity to correct a dangerous design or possibly improve design performance. In this study, we propose a margin-based design/redesign method where the design is optimized deterministically, but the margins are selected probabilistically. The final design is an epistemic random variable (i.e., it is unknown at the initial design stage) and the margins are optimized to control the epistemic uncertainty in the final design, design performance, and probability of failure. The method allows for the tradeoff between expected final design performance and probability of redesign while ensuring reliability with respect to mixed uncertainties. The method is demonstrated on a simple bar problem and then on an engine design problem. The examples are used to investigate the dilemma of whether to start with a higher margin and redesign if the test later in the design process reveals the design to be too conservative, or to start with a lower margin and redesign if the test reveals the design to be unsafe. In the examples in this study, it is found that this decision is related to the variance of the uncertainty in the high-fidelity model relative to the variance of the uncertainty in the low-fidelity model.

Turbomachinery Committee Best 1994 Paper Award: Dynamic Control of Rotating Stall in Axial Flow Compressors Using Aeromechanical Feedback

1995 ◽  
Vol 117 (3) ◽  
pp. 307-319 ◽  
Author(s):  
D. L. Gysling ◽  
E. M. Greitzer
Keyword(s):  
Control Strategy ◽  
Dynamic Control ◽  
Axial Flow ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Flow Coefficient ◽  
Compression System ◽  
Axial Flow Compressor ◽  
Flow Compressor ◽  
Axial Flow Compressors

Dynamic control of rotating stall in an axial flow compressor has been implemented using aeromechanical feedback. The control strategy developed used an array of wall jets, upstream of a single-stage compressor, which were regulated by locally reacting reed valves. These reed valves responded to the small-amplitude flow-field pressure perturbations that precede rotating stall. The valve design was such that the combined system, compressor plus reed valve controller, was stable under operating conditions that had been unstable without feedback. A 10 percent decrease in the stalling flow coefficient was obtained using the control strategy, and the extension of stable flow range was achieved with no measurable change in the steady-state performance of the compression system. The experiments demonstrate the first use of aeromechanical feedback to extend the stable operating range of an axial flow compressor, and the first use of local feedback and dynamic compensation techniques to suppress rotating stall. The design of the experiment was based on a two-dimensional stall inception model, which incorporated the effect of the aeromechanical feedback. The physical mechanism for rotating stall in axial flow compressors was examined with focus on the role of dynamic feedback in stabilizing compression system instability. As predicted and experimentally demonstrated, the effectiveness of the aeromechanical control strategy depends on a set of nondimensional control parameters that determine the interaction of the control strategy and the rotating stall dynamics.

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