scholarly journals Design Guidelines for Axial Turbines Operating With Non-Ideal Compressible Flows

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Andrea Giuffre' ◽  
Matteo Pini
Keyword(s):  
Compressible Flows ◽  
Control Volume ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Design Guidelines ◽  
Design Parameters ◽  
Stage Model ◽  
Turbine Stage ◽  
Similarity Equation ◽  
The Impact

Abstract The impact of non-ideal compressible flows on the fluid-dynamic design of axial turbine stages is examined. First, the classical similarity equation (CSE) is revised and extended to account for the effect of flow non-ideality. Then, the influence of the most relevant design parameters is investigated through the application of a dimensionless turbine stage model embedding a first-principles loss model. The results show that compressibility effects induced by the fluid molecular complexity and the stage volumetric flow ratio produce an offset in the efficiency trends and in the optimal stage layout. Furthermore, flow non-ideality can lead to either an increase or a decrease of stage efficiency up to 3–4% relative to turbines designed to operate in dilute gas state. This effect can be predicted at preliminary design phase through the evaluation of the isentropic pressure–volume exponent. Three-dimensional (3D) RANS simulations of selected test cases corroborate the trends predicted with the reduced-order turbine stage model. URANS computations provide equivalent trends, except for case study niMM1, featuring a non-monotonic variation of the generalized isentropic exponent. For such turbine stage, the efficiency is predicted to be higher than the one computed with any steady-state model based on the control volume approach.

scholarly journals Design Guidelines for Axial Turbines Operating With Non-Ideal Compressible Flows

2020 ◽  
Author(s):  
Andrea Giuffre’ ◽  
Matteo Pini
Keyword(s):  
Compressible Flows ◽  
Fluid Dynamic ◽  
Design Guidelines ◽  
Flow Coefficient ◽  
Design Parameters ◽  
Working Fluid ◽  
Stage Model ◽  
Turbine Stage ◽  
Similarity Equation ◽  
The Impact

Abstract The impact of non-ideal compressible flows on the fluid-dynamic design of axial turbine stages is examined. First, the classical similarity equation is revised and extended to account for the effect of flow non-ideality and compressibility. Then, the influence of the most relevant design parameters is investigated through the application of a dimensionless turbine stage model embedding a first-principles loss model. The results show that the selection of optimal duty coefficients is scarcely affected by the molecular complexity of the working fluid, whereas compressibility effects produce an offset in the efficiency trends and in the optimal flow coefficient. Furthermore, flow non-ideality can lead to either an increase or a decrease of stage efficiency of the order of 2–3% relative to turbines designed to operate in dilute gas state. This effect can be predicted at preliminary design phase through the evaluation of the isentropic pressure-volume exponent. 3D RANS simulations of selected test cases corroborate the trends predicted with the reduced-order turbine stage model.

Estimating the Loss Associated With Film Cooling for a Turbine Stage

2010 ◽  
Author(s):  
Chia Hui Lim ◽  
Graham Pullan ◽  
John Northall
Keyword(s):  
Film Cooling ◽  
Control Volume ◽  
Flow Direction ◽  
Three Dimensional ◽  
Turbine Stage ◽  
Flow Properties ◽  
Pragmatic Approach ◽  
Turbine Efficiency ◽  
Mainstream Flow ◽  
The Impact

A methodology is presented to allow designers to estimate the penalty for turbine efficiency associated with film cooling. The approach is based on the control volume analysis of Hartsel and the entropy-based formulations of Young and Wilcock. The present work extends these techniques to include flow ejected at compound angles and uses three-dimensional CFD to provide the mainstream flow properties. The method allows the loss contribution from each hole to be identified separately. The proposed method is applied to an aeroengine high-pressure turbine stage. It is found that, if the efficiency definition includes all irreversibilities, the penalty associated with film cooling would be 8.0%. However, if the pragmatic approach is adopted whereby the unavoidable entropy generated due to the equilibration of coolant and mainstream static temperatures is ignored, the efficiency penalty is 0.7%. Finally, a series of case studies is used to quantify the impact of changes to the local mainstream flow direction and coolant ejection angle on the predicted turbine efficiency. It is shown, quantitatively, that reducing the angle between the directions of the coolant and mainstream flows offers the greatest potential for the designer to improve film cooled turbine efficiency.

Evaluation of Interactions Between Thermal Piles Integrated in Building Foundations

2020 ◽  
Vol 1 (3) ◽  
Author(s):  
Byung Kwag ◽  
Moncef Krarti
Keyword(s):  
Three Dimensional ◽  
Design Guidelines ◽  
Interactive Effects ◽  
Design Parameters ◽  
Calculation Methods ◽  
Soil Medium ◽  
Operation Conditions ◽  
Heating And Cooling ◽  
Simplified Calculation ◽  
The Impact

Abstract This paper investigates the impact of thermal interactions between heat exchangers integrated within building foundation piles to meet space heating and cooling needs of buildings. Specifically, a three-dimensional transient numerical model is developed to evaluate the thermal performance of the foundation piles. The model is used to estimate the temperature variations within the soil medium under various operation conditions of thermo-active foundation (TAF) systems. Then, a series of parametric analyses is carried out to evaluate the influence of design parameters of the piles on the performance of TAF systems, including the interactive effects between piles as well as the impact of these piles on the building slab heat transfer. Then, the parametric analysis results are utilized to develop simplified calculation methods to assess the thermal impacts of the geometric features for the piles on both the performance of TAF systems as well as the building slab heat losses and/or gains. The developed simplified calculation methods are suitable to develop design guidelines in order to enhance the performance of thermal piles to heat and cool buildings.

On the Coupling of Inverse Design and Optimization Techniques for the Multiobjective, Multipoint Design of Turbomachinery Blades

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Duccio Bonaiuti ◽  
Mehrdad Zangeneh
Keyword(s):  
Design Method ◽  
Computational Cost ◽  
Three Dimensional ◽  
Design Strategy ◽  
Design Guidelines ◽  
Optimization Techniques ◽  
Inverse Design ◽  
Design Parameters ◽  
Turbomachinery Blades ◽  
The Impact

Automatic optimization techniques have been used in recent years for the aerodynamic and mechanical design of turbomachine components. Despite the many advantages, their use is usually limited to simple applications in industrial practice, because of their high computational cost. In this paper, an optimization strategy is presented, which enables the three-dimensional multipoint, multiobjective aerodynamic optimization of turbomachinery blades in a time frame compatible with industrial standards. The design strategy is based on the coupling of three-dimensional inverse design, response surface method, multiobjective evolutionary algorithms, and computational fluid dynamics analyses. The blade parametrization is performed by means of a three-dimensional inverse design method, where aerodynamic parameters, such as the blade loading, are used to describe the blade shape. Such a parametrization allows for a direct control of the aerodynamic flow field and performance, leading to a major advantage in the optimization process. The design method was applied to the redesign of a centrifugal and of an axial compressor stage. The two examples confirmed the validity of the design strategy to perform the three-dimensional optimization of turbomachine components, accounting for both design and off-design performance, in a time-efficient manner. The coupling of response functions and inverse design parametrization also allowed for an easy sensitivity analysis of the impact of the design parameters on the performance ones, contributing to the development of design guidelines that can be exploited for similar design applications.

Estimating the Loss Associated With Film Cooling for a Turbine Stage

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Chia Hui Lim ◽  
Graham Pullan ◽  
John Northall
Keyword(s):  
Film Cooling ◽  
Control Volume ◽  
Flow Direction ◽  
Three Dimensional ◽  
Turbine Stage ◽  
Flow Properties ◽  
Turbine Efficiency ◽  
Mainstream Flow ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact

A methodology is presented to allow designers to estimate the penalty for turbine efficiency associated with film cooling. The approach is based on the control volume analysis of Hartsel and the entropy-based formulations of Young and Wilcock. The present work extends these techniques to include flow ejected at compound angles and uses three-dimensional computational fluid dynamics (CFD) to provide the mainstream flow properties. The method allows the loss contribution from each hole to be identified separately. The proposed method is applied to an aeroengine high-pressure turbine stage. It is found that, if the efficiency definition includes all irreversibilities, the penalty associated with film cooling would be 8.0%. However, if the pragmatic approach is adopted whereby the unavoidable entropy generated due to the equilibration of coolant and mainstream static temperatures is ignored, the efficiency penalty is 0.7%. Finally, a series of case studies is used to quantify the impact of changes to the local mainstream flow direction and coolant ejection angle on the predicted turbine efficiency. It is shown, quantitatively, that reducing the angle between the directions of the coolant and mainstream flows offers the greatest potential for the designer to improve film-cooled turbine efficiency.

Modeling Partial Admission in Control Stages of Small Steam Turbines With CFD

2018 ◽  
Author(s):  
Juri Bellucci ◽  
Filippo Rubechini ◽  
Andrea Arnone
Keyword(s):  
Steam Turbine ◽  
Three Dimensional ◽  
Admission Rate ◽  
Point Of View ◽  
Test Case ◽  
Steam Turbines ◽  
Turbine Stage ◽  
Performance Curves ◽  
Partial Admission ◽  
The Impact

This work aims at investigating the impact of partial admission on a steam turbine stage, focusing on the aerodynamic performance and the mechanical behavior. The partialized stage of a small steam turbine was chosen as test case. A block of nozzles was glued in a single “thick nozzle” in order to mimic the effect of a partial admission arc. Numerical analyses in full and in partial admission cases were carried out by means of three-dimensional, viscous, unsteady simulations. Several cases were tested by varying the admission rate, that is the length of the partial arc, and the number of active sectors of the wheel. The goal was to study the effect of partial admission conditions on the stage operation, and, in particular on the shape of stage performance curves as well as on the forces acting on bucket row. First of all, a comparison between the flow field of the full and the partial admission case is presented, in order to point out the main aspects related to the presence of a partial arc. Then, from an aerodynamic point of view, a detailed discussion of the modifications of unsteady rows interaction (potential, shock/wake), and how these ones propagate downstream, is provided. The attention is focused on the phenomena experienced in the filling/emptying region, which represent an important source of aerodynamic losses. The results try to deepen the understanding in the loss mechanisms involved in this type of stage. Finally, some mechanical aspects are addressed, and the effects on bucket loading and on aeromechanical forcing are investigated.

The Impact of Modelling Air Compressibility in the Selection of Optimal OWC Design Parameters in Site Specific Wave Conditions

2019 ◽  
Author(s):  
Irene Simonetti ◽  
Lorenzo Cappietti
Keyword(s):  
Fluid Dynamic ◽  
Experimental Tests ◽  
Design Parameters ◽  
Dynamic Simulations ◽  
Regression Approach ◽  
Wave Conditions ◽  
A Site ◽  
The Impact ◽  
Period Wave ◽  
Selection Of

Abstract The importance of properly modelling the effects of air compressibility in the selection of the optimal design parameters for an Oscillating Water Column wave energy converter is investigated. For this purpose, a wide dataset of capture width ratios, obtained from both experimental tests and Computational Fluid Dynamic simulations, is used to formulate an empirical model able to predict the performance of the device as a function of its basic design parameters (chamber width and draught, turbine damping) and of the wave conditions (wave period, wave height). A multiple non-linear regression approach is used to determine the model numerical coefficients. The data used to formulate the model include the effects of air compressibility. The impact of considering such effects on the selection of the optimal geometry of the device is evaluated and discussed by means of the model application for the optimization of a device to be installed in a site located in the Mediterranean Sea (in front of the coast of Tuscany, Italy).

scholarly journals Simulation Technique of Kinematic Processes in the Vehicle Steering Linkage

2018 ◽  
Vol 7 (4.3) ◽  
pp. 120 ◽  
Author(s):  
Sergii Chernenko ◽  
Eduard Klimov ◽  
Andrii Chernish ◽  
Olexandr Pavlenko ◽  
Volodymyr Kukhar
Keyword(s):  
Three Dimensional ◽  
Simulation Technique ◽  
Design Parameters ◽  
Three Dimensional Model ◽  
Design Data ◽  
Power Characteristics ◽  
Left And Right ◽  
Turning Radius ◽  
The Impact ◽  
The Mathematical Model

The results of the investigation of the turning kinematics of the steerable wheels of the KrAZ-7634NE off-road vehicle with a wheel formula 8x8 and two front steer axles are given. The theoretical relations between the steer angles of the steerable wheels on the basis of the scheme of double-axle steering turning of the vehicle are shown. The mathematical model of flat four-bar vehicle steering linkage is developed, it determines the relation between the steering linkage left and right steering arms turning angles at any turning radius of the vehicle. KrAZ-7634HE steering three-dimensional model was created and simulation technique of its work was carried out using Creo software. It has been shown that the flat steering linkage model provides sufficient accuracy of calculations in analysis of turning kinematics. The design data can be used for any vehicles that have a similar steering linkage, they allow to analyze the impact of the vehicle design parameters on the turning kinematics and optimize them. Further study of the impact of the kingpin inclinations on the steering linkage kinematic and power characteristics are required.  

A performance investigation of small-bore sewers

2007 ◽  
Vol 55 (4) ◽  
pp. 85-91 ◽  
Author(s):  
F.A. Memon ◽  
A. Fidar ◽  
K. Littlewood ◽  
D. Butler ◽  
C. Makropoulos ◽  
...  
Keyword(s):  
Physical Model ◽  
Water Cycle ◽  
Design Guidelines ◽  
Design Parameters ◽  
New Developments ◽  
Tissue Paper ◽  
Solids Transport ◽  
Implementation Methodology ◽  
Gradient Variation ◽  
The Impact

This paper describes a full-scale physical model and its application to investigate the effectiveness/performance of small-bore sewers for a range of operational and design parameters. The implementation methodology involves observing the movement of synthetic gross solids in three small bore sewers (150, 100 and 75 mm diameter) for different volumes of simulated flush waves and gradients. The simulated flush waves were generated, using an automated wave sequencer, for three different flush volumes (3, 4.5 and 6 litres). To investigate the impact of solid shape factor, a number of tests were carried out using synthetic solids in combination with toilet tissue paper. In total, more than 1,000 tests were performed for different operational and design parameter combinations. Results obtained to date have confirmed earlier studies, particularly with respect to the role of flush volume in solids transport, and identified the impact of gradient variation and its significance particularly in small-bore sewers receiving low flush volume. Results from the physical model application exercise will be used to propose new design guidelines for wastewater collection systems with specific consideration to new developments and inform the decision support system, currently being developed as part of a research project on water cycle management for new developments (WaND).

Computational Study of Edge Cooling for Open-Cathode Polymer Electrolyte Fuel Cell Stacks

2012 ◽  
Vol 9 (6) ◽  
Author(s):  
Agus P. Sasmito ◽  
Tariq Shamim ◽  
Erik Birgersson ◽  
Arun S. Mujumdar
Keyword(s):  
Fuel Cell ◽  
Polymer Electrolyte ◽  
Thermal Management ◽  
Computational Study ◽  
Three Dimensional ◽  
Polymer Electrolyte Fuel Cell ◽  
Design Parameters ◽  
Two Phase ◽  
Practical Applications ◽  
The Impact

In open-cathode polymer electrolyte fuel cell (PEFC) stacks, a significant temperature rise can exist due to insufficient cooling, especially at higher current densities. To improve stack thermal management while reducing the cost of cooling, we propose a forced air-convection open-cathode fuel cell stack with edge cooling (fins). The impact of the edge cooling is studied via a mathematical model of the three-dimensional two-phase flow and the associated conservation equations of mass, momentum, species, energy, and charge. The model includes the stack, ambient, fan, and fins used for cooling. The model results predict better thermal management and stack performance for the proposed design as compared to the conventional open-cathode stack design, which shows potential for practical applications. Several key design parameters—fin material and fin geometry—are also investigated with regard to the stack performance and thermal management.

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