Numerical Analysis of the Effects of Nonuniform Surface Roughness on Compressor Stage Performance

2011 ◽  
Vol 133 (7) ◽  
Author(s):  
Mirko Morini ◽  
Michele Pinelli ◽  
Pier Ruggero Spina ◽  
Mauro Venturini
Keyword(s):  
Surface Roughness ◽  
Gas Turbine ◽  
Fluid Dynamic ◽  
Turbine Blades ◽  
Compressor Stage ◽  
Nonuniform Surface ◽  
Turbine Performance ◽  
Performance Map ◽  
Overall Performance ◽  
Stage Performance

Gas turbine performance degradation over time is mainly due to the deterioration of compressor and turbine blades, which, in turn, causes a modification of the compressor and turbine performance maps. Since the detailed information about the actual modification of the compressor and turbine performance maps is usually unavailable, the component performance can be modeled and investigated by the following: scaling the overall performance map, using stage-by-stage models of the compressor and turbine, and scaling each single stage performance map to account for each stage deterioration, or performing 3D numerical simulations, which allow to both highlight the fluid-dynamic phenomena occurring in the faulty component and grasp the effect on the overall performance of each affected component. In this paper, the authors address the most common and experienced source of loss for a gas turbine, i.e., compressor fouling. With respect to the traditional approach, which mainly aims at the identification of the overall effects of fouling, authors investigate a microscale representation of compressor fouling (i.e., blade surface deterioration and flow deviation). This allows (i) a more detailed investigation of the fouling effects (e.g., mechanism, location along blade height, etc.), (ii) a more extensive analysis of the causes of performance deterioration, and (iii) the assessment of the effect of fouling on stage performance coefficients and on stage performance maps. In this paper, the effect of nonuniform surface roughness on both rotor and stator blades of an axial compressor stage is investigated by using a commercial CFD code. The NASA Stage 37 test case is considered as the baseline geometry and a numerical model already validated against experimental data available in literature is used for the simulations. Different nonuniform combinations of surface roughness levels are imposed on rotor and stator blades. This makes it possible to highlight how the localization of fouling on compressor blades affects compressor performance both at an overall and at a fluid-dynamic level.

Numerical Analysis of the Effects of Non-Uniform Surface Roughness on Compressor Stage Performance

2010 ◽  
Author(s):  
Mirko Morini ◽  
Michele Pinelli ◽  
Pier Ruggero Spina ◽  
Mauro Venturini
Keyword(s):  
Surface Roughness ◽  
Gas Turbine ◽  
Traditional Approach ◽  
Fluid Dynamic ◽  
Turbine Blades ◽  
Compressor Stage ◽  
Turbine Performance ◽  
Performance Map ◽  
Overall Performance ◽  
Stage Performance

Gas turbine performance degradation over time is mainly due to the deterioration of compressor and turbine blades, which, in turn, causes a modification of the compressor and turbine performance maps. Since detailed information about the actual modification of the compressor and turbine performance maps is usually unavailable, component performance can be modeled and investigated (i) by scaling the overall performance map, or (ii) by using stage-by-stage models of the compressor and turbine and by scaling each single stage performance map to account for each stage deterioration, or (iii) by performing 3D numerical simulations, which allow to both highlight the fluid-dynamic phenomena occurring in the faulty component and grasp the effect on the overall performance of the component. In this paper, the authors address the most common and experienced source of loss for a gas turbine, i.e. compressor fouling. With respect to the traditional approach, which mainly aims at the identification of the overall effects of fouling, authors investigate a micro-scale representation of compressor fouling (e.g. blade surface deterioration and flow deviation). This allows (i) a more detailed investigation of the fouling effects (e.g. mechanism, location along blade height, etc.), (ii) a more extensive analysis of the causes of performance deterioration and (iii) the assessment of the effect of fouling on stage performance coefficients and on stage performance maps. The effects of a non-uniform surface roughness on both rotor and stator blades of an axial compressor stage are investigated by using a commercial CFD code. The NASA Stage 37 test case was used as the baseline geometry. The numerical model already validated against experimental data available in literature was used for the simulations. Different non-uniform combinations of surface roughness levels on rotor and stator blades were imposed. This makes it possible to highlight how the localization of fouling on compressor blades affects compressor performance, both at an overall and at a fluid-dynamic level.

Compressor Fouling Modeling: Relationship Between Computational Roughness and Gas Turbine Operation Time

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Francesco Melino ◽  
Mirko Morini ◽  
Antonio Peretto ◽  
Michele Pinelli ◽  
Pier Ruggero Spina
Keyword(s):  
Fluid Dynamics ◽  
Surface Roughness ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Axial Compressor ◽  
Operation Time ◽  
Compressor Stage ◽  
Performance Map ◽  
Computational Fluid Dynamics Cfd ◽  
Compressor Performance

Gas turbine axial compressor performance is heavily influenced by blade fouling. As a result, the gas turbines efficiency and producible power output decrease. Performance degradation of an axial compressor stage due to fouling can be analyzed by means of simulation through computational fluid dynamics (CFD) codes. Usually these methods reproduce the deteriorated blades by increasing their surface roughness and thickness. Another approach is the scaling of compressor stage performance maps. A model based on stage-by-stage techniques was presented in a previous work. This model is able to estimate the modifications of the overall compressor performance map as a function of the operating hours. The aim of the present study is to combine these two different approaches in order to relate the increase of blade computational surface roughness with compressor operating hours.

Compressor Fouling Modeling: Relationship Between Computational Roughness and Gas Turbine Operation Time

2011 ◽  
Author(s):  
Francesco Melino ◽  
Mirko Morini ◽  
Antonio Peretto ◽  
Michele Pinelli ◽  
Pier Ruggero Spina
Keyword(s):  
Fluid Dynamics ◽  
Surface Roughness ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Axial Compressor ◽  
Operation Time ◽  
Compressor Stage ◽  
Performance Map ◽  
Computational Fluid Dynamics Cfd ◽  
Compressor Performance

Gas turbine axial compressor performance is heavily influenced by blade fouling; as a result, the gas turbines efficiency and producible power output decrease. Performance degradation of an axial compressor stage due to fouling can be analyzed by means of simulation through Computational Fluid Dynamics (CFD) codes. Usually these methods reproduce the deteriorated blades by increasing their surface roughness and/or thickness [1]. Another approach is the scaling of compressor stage performance maps. A model based on stage-by-stage techniques was presented in a previous work. This model is able to estimate the modifications of the overall compressor performance map as a function of the operating hours [2]. The aim of the present study is to combine these two different approaches in order to relate the increase of blade computational surface roughness with compressor operating hours.

Scaling of Gas Turbine From Air to Refrigerants for Organic Rankine Cycle Using Similarity Concept

2015 ◽  
Vol 138 (6) ◽  
Author(s):  
Choon Seng Wong ◽  
Susan Krumdieck
Keyword(s):  
Gas Turbine ◽  
Test Bench ◽  
Pressure Ratio ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Expansion Ratio ◽  
Performance Estimation ◽  
Working Fluids ◽  
Turbine Performance ◽  
Performance Map

Similitude, or similarity concept, is an essential concept in turbomachinery to allow the designer to scale a turbine design to different sizes or different working fluids without repeating the whole design and development process. Similarity concept allows the testing of a turbomachine in a simple air test bench instead of a full-scale organic Rankine cycle (ORC) test bench. The concept can be further applied to adapt an existing gas turbine as an ORC turbine using different working fluids. This paper aims to scale an industrial gas turbine to different working fluids, other than the fluid the turbine was originally designed for. The turbine performance map for air was generated using the 3D computational fluid dynamics (CFD) analysis tools. Three different approaches using the similarity concept were applied to scale the turbine performance map using air and generate the performance map for two refrigerants: R134a and R245fa. The scaled performance curves derived from the air performance data were compared to the performance map generated using CFD analysis tools for R134a and R245fa. The three approaches were compared in terms of the accuracy of the performance estimation, and the most feasible approach was selected. The result shows that complete similarity cannot be achieved for the same turbomachine with two different working fluids, even at the best efficiency point for particular expansion ratio. If the constant pressure ratio is imposed, the location of the optimal velocity ratio and optimal specific speed would be underestimated with calculation error over 20%. Constant Δh0s/a012 was found to provide the highest accuracy in the performance estimation, but the expansion ratio (or pressure ratio) is varying using different working fluids due to the variation of sound speed. The differences in the fluid properties and the expansion ratio lead to the deviation in turbine performance parameters, velocity diagram, turbine's exit swirl angle, and entropy generation. The use of Δh0s/a012 further limits the application of the gas turbine for refrigerants with heavier molecular weight to a pressure ratio less than the designed pressure ratio using air. The specific speed at the best efficiency point was shifted to a higher value if higher expansion ratio was imposed. A correction chart for R245fa was attempted to estimate the turbine's performance at higher expansion ratio as a function of volumetric flow ratio.

Application of a Computational Code to Simulate Interstage Injection Effects on GE Frame 7EA Gas Turbine

2006 ◽  
Author(s):  
M. Bagnoli ◽  
M. Bianchi ◽  
F. Melino ◽  
A. Peretto ◽  
P. R. Spina ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Thermodynamic Modeling ◽  
Water Injection ◽  
Compressor Stage ◽  
Performance Parameters ◽  
Turbine Performance ◽  
Computational Code ◽  
Compressor Performance ◽  
Fortran 90 ◽  
Injection Location

This paper investigates effects of interstage water injection on the performance of a GE Frame 7EA gas turbine using aero-thermodynamic modeling. To accomplish this objective a computational code, written in Fortran 90 language and developed by DIEM – University of Bologna, has been used. The calculation procedure considers effects of evaporation of injected water within the compressor including droplets dynamics which are necessary in order to fully evaluate effects of wet compression on the gas turbine performance. The robustness of the computational code is demonstrated by evaluating stage-by-stage compressor performance and the overall gas turbine performance in presence of inlet evaporative fogging, overspray fogging and interstage water injection. The presented results show that water injection location influences compressor stage loading redistribution differently. The plausible explanations to the observed trends of various performance parameters are presented in the paper.

Hydrogen Combustion Within a Gas Turbine Reheat Combustor

2012 ◽  
Author(s):  
Madhavan Poyyapakkam ◽  
John Wood ◽  
Steven Mayers ◽  
Andrea Ciani ◽  
Felix Guethe ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Natural Gas ◽  
Gas Turbine ◽  
Dynamic Properties ◽  
Fluid Dynamic ◽  
Fold Increase ◽  
Inlet Temperature ◽  
Turbine Performance ◽  
Auto Ignition ◽  
Operating Window

This paper describes a novel lean premixed reheat burner technology suitable for Hydrogen-rich fuels. The inlet temperature for such a combustor is very high and reaction of the fuel/oxidant mixture is initiated through auto-ignition, the delay time for which reduces significantly for Hydrogen-rich fuels in comparison to natural gases. Therefore the residence time available for premixing within the burner is reduced. The new reheat burner concept has been optimized to allow rapid fuel/oxidant mixing, to have a high flashback margin and to limit the pressure drop penalty. The performance of the burner is described, initially in terms of its fluid dynamic properties and then its combustion characteristics. The latter are based upon full-scale high-pressure tests, where results are shown for two variants of the concept, one with a pressure drop comparable to today’s natural gas burners, and the other with a two-fold increase in pressure drop. Both burners indicated that Low NOx emissions, comparable to today’s natural gas burners, were feasible at reheat engine conditions (ca. 20 Bars and ca. 1000C inlet temperature). The higher pressure drop variant allowed a wider operating window. However the achievement of the lower pressure drop burner shows that the targeted Hydrogen-rich fuel (70/30 H2/N2 by volume) can be used within a reheat combustor without any penalty on gas turbine performance.

The Stacking of Compressor Stage Characteristics to Give an Overall Compressor Performance Map

1962 ◽  
Vol 13 (4) ◽  
pp. 349-367 ◽  
Author(s):  
M. D. C. Doyle ◽  
S. L. Dixon
Keyword(s):  
Axial Compressor ◽  
Compressor Stage ◽  
Individual Stage ◽  
Optimum Performance ◽  
Method Of Calculation ◽  
Multi Stage ◽  
Performance Map ◽  
Compressor Performance ◽  
Overall Performance ◽  
The Individual

SummaryA method of calculation is developed to compute the overall performance of a multi-stage axial compressor, from a knowledge of the individual stage characteristics, by a “stacking” technique. Compressor models are designed and their overall performance calculated. These results are compared to show, qualitatively, the effect of alterations in design and stage performance on overall performance and to find how compressors should be designed for optimum performance.

scholarly journals Investigating of Turbine Blades Geometrical Change Effects on Dynamic Performance of IGT-25 Gas Turbine

2019 ◽  
Author(s):  
Nima Zamani Meymian ◽  
Hossein Rabiei
Keyword(s):  
Gas Turbine ◽  
Mass Flow ◽  
Gas Flow ◽  
Fluid Dynamic ◽  
Dynamic Performance ◽  
Turbine Blades ◽  
Gas Generator ◽  
Air Compressor ◽  
Power Turbine ◽  
Geometrical Change

In the paper, the effect of gas generator turbine blades’ geometrical change has been studied on the overall performance of a twin-shaft 25MW gas turbine with industrial application, under dynamic conditions. Geometrical changes include change of thickness and height of gas generator turbine blades which in turn would result in the change in the mass flow rate of passing hot gas, as well as isentropic efficiency in each stage of the turbine. Gas turbine modeling in the paper is zero-dimensional and takes place with consideration of dynamic effects of volume on air compressor components, combustion chamber, gas generator turbine, power turbine, fuel system, as well as effects of heat transfer dynamics between blades, gas path, and effects of operators on inlet guide vanes, fuel valves, and air compressor discharge valve. In the mathematical model of each of the components, steady-state characteristics curves have been used, extracted from 3-Dimensional computational fluid dynamics (CFD). To do so, characteristic curves of the first and second stages of the four-stage turbine have been updated through 3-D fluid dynamic analysis so that the effect of geometrical changes in turbine blades would be applied. Results from effects of these changes on characteristics of transient gas flow including output power of gas generator turbine and power turbine, inlet and outlet temperatures of turbine stages, as well as air and fuel mass flow rates have been provided from the start-ups until reaching the nominal load would be achieved.

scholarly journals Surface Roughness Prediction and Minimization in 5-Axis Milling Operations of Gas Turbine Blades

2021 ◽  
Author(s):  
Arameh Eyvazian ◽  
Farayi Musharavati ◽  
Afrasyab Khan ◽  
Mohsen Soori ◽  
Tamer A. Sebaey ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Gas Turbine ◽  
Turbine Blades ◽  
Machining Process ◽  
Machining Parameters ◽  
Gas Turbine Blades ◽  
Virtual Machining ◽  
Machined Parts ◽  
Machining System

Abstract To enhance the quality of machined parts, virtual machining systems are presented in this study. In the turbine blades, the minimization of the surface roughness of the blades can decrease the Reynolds number to decrease the loss of energy in power generation. Due to difficulties of polishing process in minimizing the surface roughness of machined blades, the optimized machining parameters for minimizing the surface roughness is an effective solution for the problem. In this study, a virtual machining system is developed to predict and minimize the surface roughness in 5-Axis machining operations of gas turbine blades. To minimize the surface roughness, the machining parameters were optimized by the Genetic algorithm. To validate the developed system, the turbine blades were machined using a 5-Axis CNC machine tool and the machined blades were measured using the CMM machine to obtain the surface roughness of machined parts. So, a 41.29% reduction in the measured surface roughness and a 42.09% reduction in the predicted surface roughness are obtained using the optimized machining parameters. The developed virtual machining system can be applied in the machining process of turbine blades to enhance the surface quality of machined blades and thus improve the efficiency of gas turbines.

Formation Process of Water Film and Performance Effect on Compressor Stage

2016 ◽  
Author(s):  
Hai Zhang ◽  
Xiaojiang Tian ◽  
Xiaojun Pan ◽  
Jie Zhou ◽  
Qun Zheng
Keyword(s):  
Gas Turbine ◽  
Formation Process ◽  
Water Injection ◽  
Water Film ◽  
Compressor Stage ◽  
Blade Surface ◽  
Water Droplets ◽  
Compression Process ◽  
Turbine Performance ◽  
Wet Compression

In process of wet compression, gas turbine engine will ingest a certain amount of water, which can influence the overall performance of the engine. This phenomenon is particularly significant in the cleaning process of industrial gas turbine and water injection of aero-engine. When the quantity of water ingestion is quite large, the performance of gas turbine will appear deterioration and may lead to flameout, power reduce or even shutdown of the engine, causing accidents. Water droplets will be accumulated on the blade surface where water films could be formed on pressure surface in the wet compression process. The effects of water film on gas turbine engines are aerodynamic, thermodynamic and mechanical. The above-mentioned effects occur simultaneously and be affected by each other. Considering the above effects and the fact that they are time dependent, there are few gas turbine performance researches, which take into account the water film phenomenon. This study is a new research of investigating theoretically the water film effects on a gas turbine performance. It focuses on the aerodynamic and thermodynamic effects of the phenomenon on the compressor stage. The computation of water film thickness, which frequently be formed on the surface of compressor blade, its movement and extra torque demand, are provided by a simulation model of the code. Considering the change in blade’s profile and the thickness feature of the water film, the compressor stage’s performance deterioration is analyzed. In addition to this, movement and the formation of the water film on a compressor stage are simulated and analyzed by using unsteady numerical methods under different water injecting conditions in this paper. The movement characteristics of water droplets in compressor passage are investigated to understand the flow mechanisms responsible for water film formation process. The forming and the tearing process of water film on blade surface are analyzed at different injection conditions. For simulating the real situation, The maximum quantity of injected water can reach 12%. The results indicate that continuity and region of the water film on the blade surface will be developed with the increment of droplet size and injection rate. It is also found that the flow losses near blade surface increases with the tearing process of water film due to the increment of surface roughness.

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