Experimental Investigation of Inlet Distortion in a 4.5-Stage Axial Compressor

2020 ◽  
Author(s):  
Oliver Reutter ◽  
Gerd Enders ◽  
Theo Dabrock ◽  
Andreas Peters
Keyword(s):  
Experimental Investigation ◽  
Gas Turbines ◽  
Axial Compressor ◽  
Metal Plate ◽  
Axial Compressors ◽  
Transonic Compressor ◽  
Inlet Distortion ◽  
Surge Margin ◽  
Small Influence ◽  
Compressor Map

Abstract Inlet distortion is a subject of increasing interest in compressors over the last years. Circumferential inhomogeneities can significantly influence the behavior and the aeroelastic response of transonic compressors in gas turbines in the field of airplane propulsion as well as power generation. The circumferential inhomogeneities can result from boundary layer ingestion as planned in many future airplane concepts or from restrictions of the space available leading to short aerodynamically unfavorable intakes. As modern front rows of axial compressors react more and more sensitive to inhomogeneities because of the thinner profiles in the transonic flow regime, understanding the behavior is vital. Therefore, an experimental investigation of the inlet distortion effects on a 4.5 stage axial transonic compressor, Rig250, which is representative of the front stages of a modern high pressure compressor, has been investigated at DLR Cologne. The inhomogeneity is a total pressure distortion which is applied to the inflow upstream of the strut and the swan neck. The distortion is achieved by a perforated metal plate which can be rotated by 360° at its position. Thereby traverse measurements are possible, which allow a better understanding of the effects of the flow as the sensor positions on the casing and on the blades and vanes are fixed. As these traverses take longer time for measuring only some points are measured with traverses. The compressor has been tested with and without this inlet distortion to get a direct comparison. On the compressor map the 100 % speed line up to surge has been investigated. The inlet distortion shows only a small influence on the surge margin.

Experimental Investigation on the Performance of a Compressor Airfoil in Droplet Laden Flow

2012 ◽  
Author(s):  
Birger Ober ◽  
Franz Joos
Keyword(s):  
Experimental Investigation ◽  
Gas Turbines ◽  
Air Flow ◽  
Axial Compressor ◽  
Experimental Investigations ◽  
Test Cases ◽  
Incident Flow ◽  
Improve Performance ◽  
Compression Process ◽  
Axial Compressors

One way to improve performance and efficiency of gas turbines is to implement a wet compression process in the gas turbines’ axial compressor. Water droplet laden compressor flows promise benefits in efficiency and to some extent in performance and stability. A promising approach is the stabilizing influence on highly stressed airfoils as numerically predicted by Sun et al. [1]. First systematic experimental investigations have been made [2], but were restricted to a limited number of test cases. The ongoing experimental investigation focuses on the influence of a droplet laden flow on an axial compressors’ aerodynamics over the entire range of relevant incident flow angles. The result is a comparison of a dry air flow and a droplet laden air flow with respect to values of loss coefficient and the range of incident angles which result in a stable compressor flow.

A New Inlet Distortion and Pressure Loss Based Design of an Intake System for Stationary Gas Turbines

2013 ◽  
Author(s):  
Jose Rodriguez ◽  
Stephan Klumpp ◽  
Thomas Biesinger ◽  
James O’Brien ◽  
Tobias Danninger
Keyword(s):  
Gas Turbines ◽  
Inlet System ◽  
Inlet Distortion ◽  
Surge Margin ◽  
Compressor Surge ◽  
Compressor Inlet ◽  
The Face ◽  
Flow Quality ◽  
Inlet Manifold ◽  
Distortion Parameters

This paper presents a new design for a Compressor Inlet Manifold (CIM) for a land-based power generation Gas Turbine (turbine). The CIM is the component of the Inlet System (IS) that is directly connected to the turbine via the Compressor Inlet Case (CIC). The design philosophy is to use low fidelity but fast and automated CFD (Computational Fluid Dynamics) for design iterations and then confirm the design with detailed higher accuracy CFD before proceeding to engine tests. New design features include contouring the wall to minimize areas of flow separation and associated unsteadiness and losses, and improvement of the flow quality into the compressor. The CIM in a land-based turbine acts as a nozzle whereas the inlet of an aircraft acts as a diffuser. The flow also enters the CIM at 90 deg to the engine axis. This leads to a pair of counter rotating vortices at the compressor inlet. Three main sources of flow distortions at the face of the compressor are identified: flow separations at outer walls of the IS and CIM struts and the counter rotating vortices. The higher accuracy CFD analysis including the complete IS, CIM and the first compressor stage, simulates the effect of these distortions on the compressor front stage at design conditions. A range of inlet distortion parameters are used to evaluate the inlet design. The well known DC60 based criterion derived from aircraft engines and other less known but published parameters are able to give an indication of how the compressor surge margin of stationary gas turbines is affected.

Experimental Investigation on Droplet Behavior in a Transonic Compressor Cascade

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
Niklas Neupert ◽  
Birger Ober ◽  
Franz Joos
Keyword(s):  
Experimental Investigation ◽  
Gas Turbines ◽  
Surface Film ◽  
Flow Channel ◽  
Point Of View ◽  
Compressor Cascade ◽  
Two Phase ◽  
Transonic Compressor ◽  
Droplet Behavior ◽  
Industrial Gas Turbines

In recent years, overspray fogging has become a powerful means for power augmentation of industrial gas turbines (GT). Most of the studies concerning this topic focus on the problem from a thermodynamic point of view. Only a few studies, however, were undertaken to investigate the droplet behavior in the flow channel of a compressor. In this paper, results of experimental investigation of a water laden flow through a transonic compressor cascade are presented. A finely dispersed spray was used in the measurements (D10 < 10 μm). Results of the droplet behavior are shown in terms of shadowgraphy images and images of the blade surface film pattern. The angle of attack, the incoming velocity, and the water load were varied. The qualitative observations are related to laser Doppler and phase Doppler anemometer (LDA/PDA) data taken in the flow channel and at the outlet of the cascade. The data represent a base for numerical and mean line models of two-phase compressor flow.

Experimental Investigation of Inlet Distortion in a 4.5-Stage Axial Compressor

2021 ◽  
Author(s):  
Oliver Reutter ◽  
Gerd Enders ◽  
Theodor Dabrock ◽  
Andreas Peters
Keyword(s):  
Experimental Investigation ◽  
Axial Compressor ◽  
Inlet Distortion

A State-of-the-Art CFD Setup for Axial Compressors: Details and Validation

2020 ◽  
Author(s):  
Lorenzo Cozzi ◽  
Filippo Rubechini ◽  
Andrea Arnone ◽  
Savino Depalo ◽  
Pio Astrua ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Power Plants ◽  
State Of The Art ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Cfd Modelling ◽  
Axial Compressors ◽  
Surge Margin ◽  
Wide Range

Abstract The overall fraction of the power produced by renewable sources in the energy market has significantly increased in recent years. The power output of most of these clean sources is intrinsically variable. At present day and most likely in the upcoming future, due to the lack of inexpensive and reliable large energy storage systems, conventional power plants burning fossil fuels will still be part of the energy horizon. In particular, power generators able to promptly support the grid stability, such as gas turbines, will retain a strategic role. This new energy scenario is pushing gas turbine producers to improve the flexibility of their turbomachines, increasing the need for reliable numerical tools adopted to design and validate the new products also in operating conditions far from the nominal one. Especially when dealing with axial compressors, i.e. machines experiencing intense adverse pressure gradients, complex flow structures and severe secondary flows, CFD modelling of offdesign operation can be a real challenge. In this work, a state-of-the art CFD framework for RANS analysis of axial compressors is presented. The various aspects involved in the whole setup are discussed, including boundary conditions, meshing strategies, mixing planes modelling, tip clearance treatment, shroud leakages and turbulence modelling. Some experiences about the choice of these aspects are provided, derived from a long-date practice on this kind of turbomachines. Numerical results are reported for different full-scale compressors of the Ansaldo Energia fleet, covering a wide range of operating conditions. Furthermore, details about the capability of the setup to predict compressor performance and surge-margin have been added to the work. In particular, the setup surge-margin prediction has been evaluated in an operating condition in which the turbomachine experiences experimental stall. Finally, thanks to several on-field data available at different corrected speeds for operating conditions ranging from minimum to full load, a comprehensive validation of the presented numerical framework is also included in the paper.

Improving Steady CFD to Capture the Effects of Radial Mixing in Axial Compressors

2019 ◽  
Author(s):  
Lorenzo Cozzi ◽  
Filippo Rubechini ◽  
Andrea Arnone ◽  
Andrea Schneider ◽  
Pio Astrua
Keyword(s):  
Steady State ◽  
Gas Turbines ◽  
Turbulent Viscosity ◽  
Computational Cost ◽  
Axial Compressor ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Axial Compressors ◽  
Rans Model ◽  
Aspect Ratios

Abstract The axial compressors of power-generation gas turbines have a high stage count, blades with low aspect ratios and relatively large clearances in the rear section. These features promote the development of strong secondary flows. An important outcome deriving from the convection of intense secondary flows is the enhanced span-wise transport of fluid properties mainly involving the rear stages, generally referred to as “radial mixing”. An incorrect prediction of this key phenomenon may result in inaccurate performance evaluation and could mislead the designers during the compressor design phase. As shown in a previous work, in the rear stages of an axial compressor the stream-wise vorticity associated with tip clearance flows is one of the main drivers of the overall span-wise transport phenomenon. Limiting it by circumferentially averaging the flow at row interfaces is the reason why a steady-state analysis strongly under-predicts radial mixing. To properly forecast the span-wise transport within the flow-path, an unsteady analysis should be adopted. However, due to the high blade count, this approach has a computational cost not yet suitable for industrial purposes. Currently, only the steady-state full-compressor simulation can fit in a lean industrial design chain and any model upgrade improving its radial mixing prediction would be highly beneficial for the daily design practice. To attain some progresses in RANS model, its inherent lack of convection of stream-wise vorticity must be addressed. This can be done by acting on another mixing driver, able to provide the same outcome, that is turbulent diffusion. In particular, by enhancing turbulent viscosity one can promote span-wise diffusion, thus improving the radial mixing prediction of the steady approach. In this paper, this strategy to update the RANS model and its application in simulations on a compressor of the Ansaldo Energia fleet is presented, together with the model tuning that has been performed using the results of unsteady simulations as the target.

Aerodynamic Instability and Life Limiting Effects of Inlet and Interstage Water Injection Into Gas Turbines

2005 ◽  
Author(s):  
Klaus Brun ◽  
Rainer Kurz ◽  
Harold R. Simmons
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Water Injection ◽  
Axial Compressor ◽  
Careful Analysis ◽  
Operating Conditions ◽  
Aerodynamic Stability ◽  
Surge Margin ◽  
Power Enhancement ◽  
Aerodynamic Instability

Gas turbine power enhancement technologies such as inlet fogging, interstage water injection, saturation cooling, inlet chillers, and combustor injection are being employed by end-users without evaluating the potentially negative effects these devices may have on the operational integrity of the gas turbine. Particularly, the effect of these add-on devices, off-design operating conditions, non-standard fuels, and compressor degradation/fouling on the gas turbine’s axial compressor surge margin and aerodynamic stability is often overlooked. Nonetheless, compressor aerodynamic instabilities caused by these factors can be directly linked to blade high-cycle fatigue and subsequent catastrophic gas turbine failure; i.e., a careful analysis should always proceed the application of power enhancement devices, especially if the gas turbine is operated at extreme conditions, uses older internal parts that are degraded and weakened, or uses non-standard fuels. This paper discusses a simplified method to evaluate the principal factors that affect the aerodynamic stability of a single shaft gas turbine’s axial compressor. As an example, the method is applied to a frame type gas turbine and results are presented. These results show that inlet cooling alone will not cause gas turbine aerodynamic instabilities but that it can be a contributing factor if for other reasons the machine’s surge margin is already slim. The approach described herein can be employed to identify high-risk applications and bound the gas turbine operating regions to limit the risk of blade life reducing aerodynamic instability and potential catastrophic failure.

Development of an Improved Streamline Curvature Approach for Transonic Axial Compressor

2016 ◽  
Author(s):  
Wu Xiaoxiong ◽  
Bo Liu ◽  
Shi Lei ◽  
Zhang Guochen ◽  
Mao Xiaochen
Keyword(s):  
Incidence Angle ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Internal Flow ◽  
Field Analysis ◽  
Design Stage ◽  
Axial Compressors ◽  
Transonic Compressor ◽  
Streamline Curvature

In this paper, an improved streamline curvature (SLC) approach is presented to obtain the internal flow fields and evaluate the performance of transonic axial compressors. The approach includes some semi-empirical correlations established based on previous literatures, such as minimum loss incidence angle model, deviation model and total pressure loss model. Several developments have been made in this paper for the purpose of considering the influences of three-dimensional (3D) flow in high-loaded multistage compressors with high accuracy. A revised deviation model is applied to predict the cascade with large deflection range. The method for predicting the shock loss is also discussed in detail. In order to validate the reliability of the approach, two test cases including a two-stage transonic fan and a three-stage transonic compressor are conducted. The overall performance and distribution of spanwise aerodynamic parameters are illustrated in this paper. Compared with both the experimental and computational fluid dynamic (CFD) data at design and a number of different off-design condition, the SLC results give reasonable characteristic curves. The validation demonstrates that this improved approach can serve as a fast and reliable tool for flow field analysis and performance prediction in preliminary design stage of axial compressors.

scholarly journals Inter-Stage Dynamic Performance of an Axial Compressor of a Twin-Shaft Industrial Gas Turbine

Machines ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 83
Author(s):  
Samuel Cruz-Manzo ◽  
Senthil Krishnababu ◽  
Vili Panov ◽  
Chris Bingham
Keyword(s):  
Gas Turbine ◽  
Dynamic Performance ◽  
Axial Compressor ◽  
Modeling Framework ◽  
Axial Compressors ◽  
Stage Performance ◽  
Compressor Map ◽  
Stage Characteristic ◽  
Industrial Gas Turbine ◽  
Semi Empirical

In this study, the inter-stage dynamic performance of a multistage axial compressor is simulated through a semi-empirical model constructed in the Matlab Simulink environment. A semi-empirical 1-D compressor model developed in a previous study has been integrated with a 0-D twin-shaft gas turbine model developed in the Simulink environment. Inter-stage performance data generated through a high-fidelity design tool and based on throughflow analysis are considered for the development of the inter-stage modeling framework. Inter-stage performance data comprise pressure ratio at various speeds with nominal variable stator guide vane (VGV) positions and with hypothetical offsets to them with respect to the gas generator speed (GGS). Compressor discharge pressure, fuel flow demand, GGS and power turbine speed measured during the operation of a twin-shaft industrial gas turbine are considered for the dynamic model validation. The dynamic performance of the axial-compressor, simulated by the developed modeling framework, is represented on the overall compressor map and individual stage characteristic maps. The effect of extracting air through the bleed port in the engine center-casing on transient performance represented on overall compressor map and stage performance maps is also presented. In addition, the dynamic performance of the axial-compressor with an offset in VGV position is represented on the overall compressor map and individual stage characteristic maps. The study couples the fundamental principles of axial compressors and a semi-empirical modeling architecture in a complementary manner. The developed modeling framework can provide a deeper understanding of the factors that affect the dynamic performance of axial compressors.

Proof of Concept for a Novel Interstage Injection Design in Axial Compressors

2020 ◽  
Author(s):  
T. Doerr ◽  
S. Braun ◽  
S. Schuster ◽  
D. Brillert
Keyword(s):  
Gas Turbines ◽  
Load Distribution ◽  
Axial Compressor ◽  
Proof Of Concept ◽  
Test Rig ◽  
Innovative Design ◽  
Axial Compressors ◽  
Novel Technology ◽  
Common Technique ◽  
Injection Methods

Abstract A common technique to increase the thermal efficiency and the power output of gas turbines is to inject water upstream of the compressor section. Through the evaporation of the water throughout the compressor, an isothermal process is approached. A recently-developed technology for this enhanced process is Interstage Injection in which water is injected directly between the stages. One advantage of this over wet compression is the avoidance of icing, since the local temperatures at the injection positions are already above melting point. Moreover, stage characteristics and load distribution can be rearranged within the compressor by individually adjusting the injection amount in different stages. However, there is little practical understanding of this process, and suitable injection methods have still to be found. This paper therefore demonstrates the implementation of a novel technology of Interstage Injection in an axial compressor test rig whereby twin jet nozzles are integrated directly into the trailing edge of the first stator row to deliver a homogenous spray over the entire radial span. Due to the resultant blade complexity, blades are manufactured by selective laser melting and subsequently installed in an enhanced four-stage axial compressor. The installed control and measurement principles of the test rig are presented and results demonstrate the functionality of the innovative design.

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