Blade stacking and clocking effects in two-stage high-pressure axial turbine

2019 ◽  
Vol 91 (8) ◽  
pp. 1133-1146
Author(s):  
Kaddour Touil ◽  
Adel Ghenaiet
Keyword(s):  
High Pressure ◽  
Leading Edge ◽  
Maximum Efficiency ◽  
Two Stage ◽  
Axial Turbine ◽  
Content Type ◽  
Second Stage ◽  
Blade Row ◽  
Practical Implications ◽  
Isentropic Efficiency

Purpose The purpose of this paper is to characterize the blade–row interaction and investigate the effects of axial spacing and clocking in a two-stage high-pressure axial turbine. Design/methodology/approach Flow simulations were performed by means of Ansys-CFX code. First, the effects of blade–row stacking on the expansion performance were investigated by considering the stage interface. Second the axial spacing and the clocking positions between successive blade–rows were varied, the flow field considering the frozen interface was solved, and the flow interaction was assessed. Findings The axial spacing seems affecting the turbine isentropic efficiency in both design and off-design operating conditions. Besides, there are differences in aerodynamic loading and isentropic efficiency between the maximum efficiency clocking positions where the wakes of the first-stage vanes impinge around the leading edge of the second-stage vanes, compared to the clocking position of minimum efficiency where the ingested wakes pass halfway of the second-stage vanes. Research limitations/implications Research implications include understanding the effects of stacking, axial spacing and clocking in axial turbine stages, improving the expansion properties by determining the adequate spacing and locating the leading edge of vanes and blades in both first and second stages with respect to the maximum efficiency clocking positions. Practical implications Practical implications include improving the aerodynamic design of high-pressure axial turbine stages. Originality/value The expansion process in a two-stage high-pressure axial turbine and the effects of blade–row spacing and clocking are elucidated thoroughly.

Flow unsteadiness and rotor-stator interaction in a two-stage axial turbine

2021 ◽  
pp. 095765092096162
Author(s):  
Kaddour Touil ◽  
Adel Ghenaiet
Keyword(s):  
Pressure Ratio ◽  
Potential Effect ◽  
Navier Stokes ◽  
Two Stage ◽  
Axial Turbine ◽  
Second Stage ◽  
Blade Row ◽  
Rotor Stator Interaction ◽  
Nozzle Guide ◽  
Isentropic Efficiency

This paper presents an in-depth investigation of the unsteady flows through two-stage high-pressure (hp) axial turbine with analyses of the rotor-stator interaction effects on the aerothermodynamic performance. The unsteady flow structures are characterized by the formation and convection of the tip leakage vortex and the hub corner vortices from the first stage blade-row through the second stage nozzle guide vanes (NGV) and blade-row. The modal decomposition of the circumferential distributions of static pressure depicts the modulation of the potential effect in the form of lobed structure propagating in both sides. Moreover, the blade pressure field shows that the first blade-row is exposed to a periodic overpressure induced by the first NGV while in the second blade-row the linear combination of both potential effects is dominant and results in a complex unsteady blade loading. FFT analyses of unsteady turbine performance for two-stage and part stages reveal that the total-to-total isentropic efficiency, torque-based efficiency and pressure ratio of the first stage depend strongly on the first blade-row passing frequency (BPF), whereas the total-to-total isentropic efficiency in second stage and two-stage turbine is related to the second blade-row BPF while the pressure ratio and the torque-based efficiency depend on the two rotors BPFs. Finally, the torque oscillations are mainly associated with the combination of frequencies of first stage NGV with that of second stage NGV. Furthermore, the obtained results show that Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations are essential in analyzing the complex wakes and vortical structures through the two-stage turbine components and may produce better estimation of the performance.

The contribution of project management offices to addressing complexities in principal construction contracting

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mahmoud Ershadi ◽  
Marcus Jefferies ◽  
Peter Rex Davis ◽  
Mohammad Mojtahedi
Keyword(s):  
Project Management ◽  
Survey Study ◽  
Two Stage ◽  
Content Type ◽  
Qualitative Survey ◽  
Functional Areas ◽  
Larger Sample ◽  
Practical Implications ◽  
Major Project ◽  
Construction Contracting

PurposeThe purpose of this study is twofold: first, to identify major project management (PM) complexities in principal construction contracting; and second, to study the contribution of project management offices (PMOs) to addressing such complexities.Design/methodology/approachA two-stage research design was adopted through a structured literature review (SLR) and a qualitative survey study.FindingsThe two-stage study resulted in mapping out the contribution of 10 functional areas to 15 complexity factors that were retrieved from the literature and categorized using the TOE (technical, organizational and environmental) framework. Six outcomes including (1) facilitated processes, (2) improved decisions, (3) improved coordination, (4) enhanced alignment, (5) addressed uncertainties and (6) integrated oversight were identified that describe how PMOs can contribute to tackling complexities.Research limitations/implicationsSimilar to other qualitative studies, this study has some limitations in terms of the replicability of results. Regarding the exploratory nature of this study to explain the contribution of PMO to complexity, further quantitative surveys can be conducted using a larger sample to statistically examine the significance of proposed relations between capabilities and complexity factors.Practical implicationsThis study provides an understanding of the contribution of PMOs to tackling ever-increasing complexities embedded in construction contracting. The authors suggest requirements to be considered by professionals toward overcoming such complexities.Originality/valueAlthough prior studies have separately investigated PMO functions and PM complexities, this study explores the link between these two spheres to discuss one important application of PMO in this context.

Benchmarking the efficiencies of Indonesia’s municipal water utilities using Stackelberg data envelopment analysis

2015 ◽  
Vol 22 (4) ◽  
pp. 588-609 ◽  
Author(s):  
Andreas Wibowo ◽  
Hans Wilhelm Alfen
Keyword(s):  
Data Envelopment Analysis ◽  
The Body ◽  
Water Utilities ◽  
Data Envelopment ◽  
Two Stage ◽  
Restrictive Assumption ◽  
Content Type ◽  
Second Stage ◽  
Municipal Water ◽  
The Impact

Purpose – The purpose of this paper is to present a yardstick efficiency comparison of 269 Indonesian municipal water utilities (MWUs) and measures the impact of exogenous environmental variables on efficiency scores. Design/methodology/approach – Two-stage Stackelberg leader-follower data envelopment analysis (DEA) and artificial neural networks (ANN) were employed. Findings – Given that serviceability was treated as the leader and profitability as the follower, the first and second stage DEA scores were 55 and 32 percent (0 percent = totally inefficient, 100 percent = perfectly efficient), respectively. This indicates sizeable opportunities for improvement, with 39 percent of the total sample facing serious problems in both first- and second-stage efficiencies. When profitability instead leads serviceability, this results in more decreased efficiency. The size of the population served was the most important exogenous environmental variable affecting DEA efficiency scores in both the first and second stages. Research limitations/implications – The present study was limited by the overly restrictive assumption that all MWUs operate at a constant-return-to-scale. Practical implications – These research findings will enable better management of the MWUs in question, allowing their current level of performance to be objectively compared with that of their peers, both in terms of scale and area of operation. These findings will also help the government prioritize assistance measures for MWUs that are suffering from acute performance gaps, and to devise a strategic national plan to revitalize Indonesia’s water sector. Originality/value – This paper enriches the body of knowledge by filling in knowledge gaps relating to benchmarking in Indonesia’s water industry, as well as in the application of ensemble two-stage DEA and ANN, which are still rare in the literature.

Effects of the Clocking on the Internal Flow in a 1.5 Stage Axial Turbine

2006 ◽  
Author(s):  
Jongil Park ◽  
Minsuk Choi ◽  
Jehyun Baek
Keyword(s):  
Unsteady Flow ◽  
Relative Efficiency ◽  
Message Passing Interface ◽  
Flow Simulation ◽  
Internal Flow ◽  
Leading Edge ◽  
Maximum Efficiency ◽  
Axial Turbine ◽  
Flow Solver ◽  
Local Efficiency

A three-dimensional unsteady flow simulation is conducted to investigate clocking effects of a row of stators on the performance and internal flow in a 1.5 stage axial turbine. Although the original turbine has 22 blades of the first stator, 28 blades of the rotor and 28 blades of the second stator, the first stator is reduced by a factor of 22/28 to fit the blade ratio 1:1:1. The unsteady flow solver is implemented using the second order time marching and sliding mesh scheme between blade rows. And then, this flow solver is parallelized using MPI (Message Passing Interface) libraries to overcome the limitation of memories and to save the calculation time. Six relative positions of two rows of stators are investigated by positioning the second stator being clocked in a step of 1/6 pitch. The relative efficiency benefit of about 1% is obtained depending on clocking positions. At mid-span, the first stator wake is mixed up with the rotor wake before arriving at the leading edge of the second stator. The time-averaged local efficiency along the span at the maximum efficiency shows more uniform distribution than that at the minimum efficiency. Moreover, the variation of local efficiency at the mid-span does not coincide with that of overall efficiency. Therefore, it is found in this case that the only wake trajectory of the first stator is not a proper means of predicting the best and worst efficiency positions. This is why the relative efficiency benefit depending on the clocking position is obtained near the hub and casing in this study. So, it is necessary to find a general cause of the clocking effect which is applicable to every test case. The difference between maximum and minimum instantaneous efficiencies during one period is found to be smaller at the maximum efficiency than at the minimum efficiency.

Preparing a framework for two-stage target-cost arrangement formulation

2016 ◽  
Vol 9 (1) ◽  
pp. 123-146 ◽  
Author(s):  
Pertti Lahdenperä
Keyword(s):  
Service Provider ◽  
Development Process ◽  
Cost Effective ◽  
Two Stage ◽  
Content Type ◽  
Investment Projects ◽  
Second Stage ◽  
Target Cost ◽  
The Cost ◽  
Concrete Model

Purpose – Early involvement of the project team with the construction resources seems to be gaining popularity as it aims to improve the cost efficiency of a project as there is significantly more potential to influence the project solution at that point in time. The missing price during early involvement/selection and the principal-agent setting, however, tend to leave the project owner in doubt of the reasonableness of pricing when it is fixed only later after the joint design phase involving the service provider and the owner. The purpose of this paper is to find a solution for this challenge. Design/methodology/approach – A two-stage target-cost (2STC) arrangement has been proposed as the solution. In this model the service provider earns a bonus by suggesting a lower target cost than the reference set at the time of the involvement of the provider. The amount of bonus also impacts the cost over-run risk transferred to the service provider to avoid overly optimistic promises. The proposition encompassed just the basic idea, and did not really delve into actual model formulations and their functioning under practical realities. Therefore, the required work is presented here in the form of a conceptual, discursive study focusing on relevant theories and empirical findings from major investment projects. Findings – The study produces a requirement framework for the 2STC model to allow functioning models to be formulated and tested. The framework incorporates numerous requirements, constraints and a suggested path forward. For instance, while the model may not be manipulatable, it must incentivise the service provider to seek more cost-effective project solutions, be feasible also from the view of the project owner and adapt to various project risk profiles and ranges of efficiency improvements. Research limitations/implications – The study suggests more concrete model formulations to be provided under the guidance of the presented framework. Originality/value – The 2STC model is a unique concept and no comparable construct is known to exist. Besides the requirement framework, the study also strengthens the foundation of and need for the 2STC model by a thorough survey of its theoretical linkages. Accordingly, the study presented in this paper forms the second stage in the overall 2STC development process focused on benefiting project owners and the industry.

Impact of Manufacturing Variability on Multistage High-Pressure Compressor Performance

2012 ◽  
Vol 134 (11) ◽  
Author(s):  
Alexander Lange ◽  
Matthias Voigt ◽  
Konrad Vogeler ◽  
Henner Schrapp ◽  
Erik Johann ◽  
...  
Keyword(s):  
High Pressure ◽  
Pressure Rise ◽  
Leading Edge ◽  
Back Pressure ◽  
Operating Conditions ◽  
Geometric Parameters ◽  
Maximum Efficiency ◽  
Novel Approach ◽  
High Pressure Compressor ◽  
Pressure Compressor

The present paper introduces a novel approach for considering manufacturing variability in the numerical simulation of a multistage high-pressure compressor (HPC). The manufacturing process is investigated by analyzing three of a total of ten rotor rows. Therefore, 150 blades of each of the three rows were 3D scanned to obtain surface meshes of real blades. The deviation of a scanned blade to the design intent is quantified by a vector of 14 geometric parameters. Interpolating the statistical properties of these parameters provides the manufacturing scatter for all ten rotor rows expressed by 140 probability density functions. The probabilistic simulation utilizes the parametric scatter information for generating 200 virtual compressors. The CFD analysis provides the performance of these compressors by calculating speed lines. Postprocessing methods are applied to statistically analyze the obtained results. It was found that the global performance parameters show a significantly wider scatter range for higher back pressure levels. The correlation coefficient and the coefficient of importance are utilized to identify the sensitivity of the results to the geometric parameters. It turned out that the sensitivities strongly shift for different operating points. While the leading edge geometry of all rotor rows dominantly influences the overall performance at maximum efficiency, the camber line parameters of the front stages become more important for higher back pressure levels. The analysis of the individual stage performance confirms the determining importance of the front stages—especially for highly throttled operating conditions. This leads to conclusions regarding the robustness of the overall HPC, which is principally determined by the efficiency and pressure rise of the front stages.

Influence of Aerodynamic Loading on Rotor-Stator Aerodynamic Interaction in a Two-Stage Low Pressure Research Turbine

2006 ◽  
Author(s):  
Edward Canepa ◽  
Piergiorgio Formosa ◽  
Davide Lengani ◽  
Daniele Simoni ◽  
Marina Ubaldi ◽  
...  
Keyword(s):  
Turbulence Intensity ◽  
Low Pressure ◽  
Potential Interaction ◽  
Two Stage ◽  
Average Technique ◽  
High Lift ◽  
Second Stage ◽  
Aerodynamic Loading ◽  
Aerodynamic Interaction ◽  
Blade Row

The unsteady flow within a two-stage low-pressure research turbine equipped with high lift profiles has been investigated in detail for three different aerodynamic loading conditions. Experiments have been carried out at low speed. Velocity and turbulence intensity in the blade-to-blade plane at midspan have been measured by means of a crossed hot-wire probe, upstream and downstream of each blade row. The probe has been traversed circumferentially over 1.5 bladings pitch and the phase-locked data acquisition and ensemble average technique have been used to reconstruct the flow in space and time. The effects of multistage configuration have been identified and analyzed by considering the velocity components and turbulence intensity. Potential interaction from the downstream blading in relative motion, periodic wake perturbations from the upstream blading and preceding stage perturbations make the flow in the second stage extremely complex. Overall the flow downstream of rotors is perturbed in space by upstream and downstream stators, while flow downstream of stators is mostly perturbed in time by rotor effects. As expected, high lift profiles are significantly sensitive to incidence variation, with this effect further enhanced by the multistage cumulative interactions.

Morphology of γ' Precipitates in Second Stage High Pressure Turbine Blade of Single Crystal Nickel-Based Superalloy after Serviced

2010 ◽  
Vol 638-642 ◽  
pp. 2291-2296 ◽  
Author(s):  
N. Miura ◽  
K. Nakata ◽  
M. Miyazaki ◽  
Y. Hayashi ◽  
Y. Kondo
Keyword(s):  
High Pressure ◽  
Single Crystal ◽  
Turbine Blade ◽  
Leading Edge ◽  
Aircraft Engine ◽  
Pressure Side ◽  
High Pressure Turbine ◽  
Second Stage ◽  
Nickel Based Superalloy ◽  
The Matrix

The morphology of the ’ precipitates in the single crystal nickel-based superalloy serviced as the second stage high pressure turbine blade of the aircraft engine was examined. The aim of this work was to estimate the temperature and the stress distribution, and the stress direction of the blade in service. The blade was cut into three parts parallel to (001) plane at 8, 40 and 64mm from the tip. These parts were named as the tip, middle and root parts. Furthermore, these three parts were cut into six parts parallel to {100} which were almost normal to the surface from the leading to the trailing edge at interval of 6mm. Microstructure observations by a FE-SEM were carried out on the thirty portions of each part parallel to (001) and {100} planes at the vicinity of the interface between the coating layer and the matrix in the suction and pressure sides. Most of the ’ precipitates contacted each other toward almost parallel to the surface at the vicinity of the interface in the blade. Especially, at the leading edge of the pressure side of the tip and middle parts, the rafted /’ structures start to collapse. Consequently, the blade in service, at the leading edge of the pressure side of the tip and middle parts were exposed to the highest temperature and stress conditions. And the multi-axial compressive stresses parallel to the blade surface were expected to act on the blade in service.

scholarly journals Development of two-stage multi-anvil apparatus for low-temperature measurements

2019 ◽  
Vol 11 ◽  
pp. 110006
Author(s):  
K. Ishigaki ◽  
J. Gouchi ◽  
S. Nagasaki ◽  
J. G. Cheng ◽  
Y. Uwatoko
Keyword(s):  
High Pressure ◽  
Low Temperature ◽  
Room Temperature ◽  
Edge Length ◽  
Hydraulic Press ◽  
Temperature Measurements ◽  
Two Stage ◽  
Sample Container ◽  
Total Size ◽  
Second Stage

The two-stage 6-8 multi-anvil (MA8) apparatus is an important large-volume, high-pressure technique that has been widely used in the high pressure mineralogy and material synthesis, mainly at room temperature or above. Recently, we have successfully developed a two-stage MA8 apparatus for low-temperature physical property measurements. The first-stage anvils at top and bottom sides are fabricated as a single piece in order to reduce the total size of the cylindrical module, which is put in a top-loading high pressure cryostat and compressed by a 1000 ton hydraulic press. A castable, split octahedral gasket with integrated fin was specifically designed in order to introduce the electrical leads from the inside sample container filled with a liquid pressure transmitting medium. By using tungsten carbide (WC) second-stage cubes with a truncated edge length of 3 mm and an octahedral gasket with an edge length of 6 mm, we have successfully generated pressure over 20 GPa at room temperature. Since the high pressure limit can be pushed to nearly 100 GPa by using the sintered diamond second-stage cubes, our MA8 apparatus has a great potential to expand the current pressure capacity for precise low-temperature measurements with a large sample volume. Edited by: A. Goñi, A. Cantarero, J. S. Reparaz

Aerodynamics and Heat Transfer for a Cooled One and One-Half Stage High-Pressure Turbine—Part III: Impact of Hot-Streak Characteristics on Blade Row Heat Flux

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
R. M. Mathison ◽  
C. W. Haldeman ◽  
M. G. Dunn
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Pressure ◽  
Radial Profile ◽  
Leading Edge ◽  
Coolant Temperature ◽  
High Pressure Turbine ◽  
Blade Row ◽  
Hot Streak ◽  
The Impact

The influence of hot-streak magnitude and alignment relative to the vane leading edge on blade row heat flux is investigated for a one and one-half stage high-pressure turbine with a film-cooled vane, purge cooling, and uncooled blades. The full-stage turbine is operated at design-corrected conditions. In addition to investigating the impact of different hot-streak characteristics, this study also looks at the interaction of cooling flow with the hot streaks. This paper builds on the investigation of profile migration utilizing temperature measurements presented in Part I and the heat transfer measurements presented in Part II. Hot streaks aligned with the vane midpitch have a greater impact on blade temperatures and heat-flux values than hot streaks aligned with the vane leading edge. The leading edge hot streaks tend to be mixed out over the surface of the vane. The magnitude of the hot streak is observed to have the largest influence on the temperature and heat flux for the downstream blade. Time-accurate measurements confirm these conclusions and indicate that further analysis of the time-accurate data is warranted. Film cooling is found to impact a hot-streak profile in a way similar to that observed for a radial profile. Differences in core to coolant temperature ratio cause the uniform profile to show different coolant effects, but the overall spread of the cooling appears similar.

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