3 CFD for industrial turbomachinery design

Author(s):  
C. Xu ◽  
R. S. Amano
Author(s):  
H. Perez-Blanco ◽  
A. Rigg ◽  
L. Moroz

Whereas turbomachinery design has evolved over the last two decades, updating instruction on the topic to reflect the new prevailing methods and techniques remains a challenge. Part of this challenge stems from the diversity of technologies covered in the courses; part of it ensues from the extensive use of software by industry designers. A review of the literature shows that varying degrees of complexity in software have been adopted for teaching, and that numerical experimentation has in some universities replaced laboratory experimentation. This paper describes the experience and outcomes of teaching turbomachinery to senior engineering students using advanced design software. The cases and results analyzed by the students for axial compressors and turbines are discussed, and the results of the effort are evaluated from the somewhat different perspectives of the students and of the instructor. Whereas the use of the program must be viewed in the context of the entire course (two hardware labs are held along with conventional lectures and homework), the use of design software could be seen to multiply the skills of the students, enabling broad 3-D design considerations and visualization seldom possible otherwise. In addition, an understanding of prevailing stresses is initiated with the software.


Author(s):  
Bugra Ertas

Abstract The following paper presents a new type of gas lubricated thrust bearing fabricated using additive manufacturing or direct metal laser melting (DMLM). The motivation for the new bearing concept is derived from the need for highly efficient supercritical carbon dioxide turbomachinery in the mega-watt power range. The paper provides a review of existing gas thrust bearing technologies, outlines the need for the new DMLM concept, and discusses proof of concept testing results. The new concept combines hydrostatic pressurization with individual flexibly mounted pads using hermetic squeeze film dampers in the bearing-pad support. Proof-of-concept testing in air for a 6.8" (173mm) outer diameter thrust bearing was performed; with loads up to 1,500 lbs (6.67kN) and a rotating speed of 10krpm (91 m/s tip speed). The experiments were performed with a bent shaft resulting in thrust runner axial vibration magnitudes of 2.9mils (74microns) p-p and dynamic thrust loads of 270 lbs (1.2kN) p-p. In addition, force deflection characteristics of the bearing system are presented for an inlet hydrostatic pressure of 380psi (2.62MPa). Results at 10krpm show that the pad support architecture was able to sustain high levels of dynamic misalignment equaling 6 times the nominal film clearance while demonstrating a unit load carrying capacity of 55psi (0.34Mpa). Gas-film force-deflection tests portrayed nonlinear behavior like a hardening spring, while the pad support stiffness was measured to be linear and independent of film thickness.


Author(s):  
Johann Gross ◽  
Malte Krack ◽  
Harald Schoenenborn

The prediction of aerodynamic blade forcing is a very important topic in turbomachinery design. Usually, the wake from the upstream blade row and the potential field from the downstream blade row are considered as the main causes for excitation, which in conjunction with relative rotation of neighboring blade rows, give rise to dynamic forcing of the blades. In addition to those two mechanisms so-called Tyler-Sofrin (or scattered or spinning) modes, which refer to the acoustic interaction with blade rows further up- or downstream, may have a significant impact on blade forcing. In particular, they lead to considerable blade-to-blade variations of the aerodynamic loading. In part 1 of the paper a study of these effects is performed on the basis of a quasi 3D multi-row and multi-passage compressor configuration. Part 2 of the paper proposes a method to analyze the interaction of the aerodynamic forcing asymmetries with the already well-studied effects of random mistuning stemming from blade-to-blade variations of structural properties. Based on a finite element model of a sector, the equations governing the dynamic behavior of the entire bladed disk can be efficiently derived using substructuring techniques. The disk substructure is assumed as cyclically symmetric, while the blades exhibit structural mistuning and linear aeroelastic coupling. In order to avoid the costly multi-stage analysis, the variation of the aerodynamic loading is treated as an epistemic uncertainty, leading to a stochastic description of the annular force pattern. The effects of structural mistuning and stochastic aerodynamic forcing are first studied separately and then in a combined manner for a blisk of a research compressor without and with aeroelastic coupling.


Author(s):  
Ricardo Puente ◽  
Roque Corral ◽  
Jorge Parra

In this paper a fast automatic design environment is developed, making use of a well established and validated turbomachinery design software system for geometry generation and flow analysis. The design is updated via a gradient based algorithm, where gradients are obtained via the adjoint method. The computational advantages of Graphics Processing Units are used to accelerate the mesh generation and flow analysis stages. The capabilities of the system are illustrated by automatically generating two Low Pressure Turbine vanes, and comparing them to the ones arrived at by a human designer, respecting the same explicit design criteria. The quality of the automatically designed airfoils is assessed against the human generated ones, and insight on the influence of implicit criteria is extracted. It is concluded that acceptable quality geometries can be designed automatically in a short time. For instance, the automatic procedure takes of the order of two days for an equivalent human driven case, where the designer took of the order of two weeks.


Author(s):  
Jerome P. Jarrett ◽  
William N. Dawes ◽  
P. John Clarkson

Aeroengines are designed using fractured processes. Complexity has driven the design of such machines to be subdivided by specialism, customer and function. While this approach has worked well in the past, with component efficiencies, current material performance and the possibilities presented by scaling existing designs for future needs becoming progressively exhausted it is necessary to reverse this process of disintegration. Our research addresses this aim. The strategy we use has two symbiotic arms. The first is an open data architecture from which existing disparate design codes all derive their input and to which all send their output. The second is a dynamic design process management system known as “SignPosting”. Both the design codes and parameters are arranged into complementary multiple level hierarchies: fundamental to the successful implementation of our strategy is the robustness of the mechanisms we have developed to ensure consistency in this environment as the design develops over time. One of the key benefits of adopting a hierarchical structure is that it confers not only the ability to use mean-line, throughflow and fully 3D CFD techniques in the same environment but also to cross specialism boundaries and insert mechanical, material, thermal, electrical and structural codes, enabling exploration of the design space for multi-disciplinary non-linear responses to design changes and their exploitation. We present results from trials of an early version of the system applied to the redesign of a generic civil aeroengine core compressor. SignPosting has allowed us to examine the hardness of design constraints across disciplines which has shown that it is far more profitable not to strive for even higher aerodynamic performance, but rather improve the commercial performance by maintaining design and part speed pressure ratios stability and efficiency while increasing rotor blade creep life by up to 70%.


Author(s):  
Carlo Cravero ◽  
Martino Marini

The authors decided to organize their design/analysis computational tools in an integrated software suite in order to help teaching radial turbine, taking advantage of their research background and a set of codes previously developed. The software is proposed for use during class works and the student can either use a single design/analysis tool or face a complete design loop consisting of iterations between design and analysis tools. The intended users are final year students in mechanical engineering. The codes output are discussed with two practical examples in order to highlight the turbomachinery performance at design and off-design conditions. The above suite gives the student the opportunity of getting used to different concepts (choking, blade loading, performance maps, …) that are encountered in turbomachinery design and of understanding the effects of the main design parameters.


1981 ◽  
Vol 103 (1) ◽  
pp. 65-77 ◽  
Author(s):  
Colin F. McDonald ◽  
Murdo J. Smith

For several years, design studies have been underway in the U.S. on a nuclear closed-cycle gas turbine plant (HTGR-GT). This paper presents design aspects of the helium turbo-machine portion of these studies. Gas dynamic and mechanical design considerations are presented for helium turbomachines in the 400 MWe (non-intercooled) and 600 MWe (intercooled) power range. Design of the turbomachine is a key element in the overall power plant program effort, which is currently directed towards the selection of a reference HTGR-GT commercial plant configuration for the U.S. utility market. A conservative design approach has been emphasized to provide for maximum safety and durability. The studies presented for the integrated plant concept outline the necessary close working relationship between the reactor primary system and turbomachine designers. State-of-the-art technology from large industrial gas turbines developed in the U.S., considered directly applicable to the design of a helium turbomachine, particularly in the areas of design methodology, performance, materials, and fabrication methods, is emphasized.


2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Harald Schoenenborn

The aeroelastic prediction of blade forcing is still a very important topic in turbomachinery design. Usually, the wake from an upstream airfoil and the potential field from a downstream airfoil are considered as the main disturbances. In recent years, it became evident that in addition to those two mechanisms, Tyler–Sofrin modes, also called scattered or spinning modes, may have a significant impact on blade forcing. It was recently shown in literature that in multirow configurations, not only the next but also the next but one blade row is very important as it may create a large circumferential forcing variation, which is fixed in the rotating frame of reference. In the present paper, a study of these effects is performed on the basis of a quasi three-dimensional (3D) multirow and multipassage compressor configuration. For the analysis, a harmonic balancing code, which was developed by DLR Cologne, is used for various setups and the results are compared to full-annulus unsteady calculations. It is shown that the effect of the circumferentially different blade excitation is mainly contributed by the Tyler–Sofrin modes and not to blade-to-blade variation in the steady flow field. The influence of various clocking positions, coupling schemes and number of harmonics onto the forcing is investigated. It is also shown that along a speed-line in the compressor map, the blade-to-blade forcing variation may change significantly. In addition, multirow flutter calculations are performed, showing the influence of the upstream and downstream blade row onto aerodynamic damping. The effect of these forcing variations onto random mistuning effects is investigated in the second part of the paper.


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