Exile Vol. XXVI No. 1

Photo: Untitled by Jamie Bailey 3 Poem: Hi, My Name Is by Kathy Andrews 4 Poem: Untitled by Willi Haworth 5 Photo: Stratified Snow by Jim Lundy 6 Poem: Untitled by A. Pence 7 Poem: Akua\u27ba by Tona Dickerson 8 Photo: Untitled by Jim Lundy 9 Story: The Dogcatchers of Portimao by Debora Papierski 10-13 Photo: Untitled by Holly Hall 14 Poem: Tocopold Bloom: A Working Class Hero by Mary Ladky 15 Photo: Untitled by Cory Easter 16 Poem: A Mortal Wound by Peter Fish 17 Poem: Let Me Sleep by R. G. Trub 18-19 Photo: Modified Cube by Jim Lundy 20 Story: Untitled by Kathy Desmond 21-23 Photo: Untitled by Holly Hall 24 Poem: Untitled by Sharon McCartney 25 Photo: Untitled by Him Lundy 26 Poem: Every Morning I Wake by Peter Fish 27 Photo: Untitled by Rof Smith 28 Poem: For Mark Some Words by Bonny Lowe 29 Photo: Untitled by Jim Lundy 30 Poem: A Flash of Crooked Light by Lisa Minacci 31 Photo: Untitled by Jim Lundy 32 Poem: Paper Hearts by W. Dulles 33 Drawing: Untitled by Roger Weisman 34 Story: Untitled by Dane Lavin 35-42 Photo: Untitled by Jim Lundy 43 Special Thanks To Laurie Howard -

Wielokryterialna optymalizacja półotwartego wirnika odśrodkowej pompy metodą wielopoziomową

The complete optimization task for the case of the semi-open impeller with straight blades requires description of its geometry by means of, at least, eighteen design variables. In the case of constant meridional cross-section, required are at least eight design variables. Solution of the task with such a great vector of design variables requires much more time. One of the ways to obtain solutions with great variety of design variables is a comprehensive approach to the task including on the partition into minor subtasks. After decomposing the optimization task, one should choose a procedure for solving it. One of such procedures is parametric optimization, which is a two-stage minimization (maximization) method. This optimization is carried out in two levels. On the lower level, the multi-optimization of the decomposed parts of the tasks, depending on design variables, is being held. The solution of the lower level is used in the upper level (coordinating level) to find optimal coordination variables. It has been shown that the result of multi-level optimization and the whole task optimization is the same in limits of accepted accuracy of calculation of the objective functions. Time of the calculation for the multilevel optimization task is over four times shorter than the time of the undecomposed task.Pełne zadanie optymalizacyjne dla przypadku półotwartego wirnika wymaga z łopatkami o pojedynczej krzywiźnie wymaga opisania jego geometrii za pomocą co najmniej 18 zmiennymi decyzyjnymi, a w przypadku niezmiennego przekroju merydionalnego potrzeba co najmniej 8 zmiennych decyzyjnych. Czas rozwiązania zadania o tak wielkim wymiarze wektora zmiennych decyzyjnych jest bardzo duży. Jednym ze sposobów rozwiązania zadań z dużą ilością zmiennych decyzyjnych jest systemowe podejście do zagadnienia polegające na podziale problemu na mniejsze części. Po zdekomponowaniu problemu optymalizacyjnego należy wybrać metodę rozwiązania zadania. Jedną z takich metod jest metoda optymalizacji parametrycznej, która jest dwuetapową metodą minimalizacji (maksymalizacji). Optymalizacja ta polega na tym, że dokonujemy jej na dwóch poziomach. Na poziomie dolnym przeprowadza się wielokrotną optymalizację zdekomponowanych części problemu względem ich zmiennych decyzyjnych. Wynik optymalizacji na poziomie dolnym jest wykorzystywany na poziomie górnym, zwanym koordynacyjnym, do znajdowania optymalnych wartości zmiennych koordynacyjnych. Wykazano, że wynik optymalizacji wielopoziomowej i pełnego zadania optymalizacji jest taki sam w granicach przyjętej dokładności obliczeń funkcji celu. Czas obliczeń zadania optymalizacji wielopoziomowej jest ponad czterokrotnie mniejszy niż zadania niezdekompowanego

Multiblock parallel computation of an incompressible 3D flow in turbomachines

A finite volume numerical method for the prediction of a fluid flow in complex geometries such as turbomachinery channels has been parallelized using a domain decomposition approach. A mathematical formulation of a 3-D incompressible steady flow has been presented on the basis of the N-S equations in a grid-oriented co-ordinate system with contravariant velocity components. A parallelized pressure-based implicit algorithm with discretization on a staggered grid has been developed. A message exchange system with a boundary exchange, developed by the authors, has been described. Exemplary calculations have been carried out for a laminar flow through a curved duct and for an inviscid flow through a stage of the centrifugal pump. A good agreement has been obtained in both the cases. Despite considerable simplification that has been introduced in the flow through the pump stage, the computations have shown nearly the same pressure rise in the stage as the measurements. Further directions of numerical investigations of a flow through turbomachines, including in particular those devoted to pressure losses related to the rotor-stator interaction, have been mentioned

Suction intakes - the design method for vertical axial-flow pumps

Przedstawiono procedurę projektowania, w której w celu optymalizacji komór ssawnych pomp wykorzystuje się wyniki obliczeń numerycznych przepływu ustalonego w komorze ssawnej oraz aplikacje metod optymalizacji konstrukcji w aspekcie realizacji przyjętych funkcji celu. Zaproponowane przez autorów funkcje celu dotyczą optymalnego napływu czynnika na wirnik.Proposed design procedure is a coherent method in which to optimize intakes there are used numerical steady flow computation results for the suction intake and applications for methods of construction optimization in the aspect of realization of objective functions. Proposed by the authors, objective functions concern the optimal liquid inflow at the pump impeller

CFD code - a useful tool for the turbomachinery designer

The presentation of CFX-TASCflow code possibilities for the turbomachinery design is the main aim of this study. In the first part of the work the compressor design process is presented. Next, CFX-TASCflow possibilities in predicting unstable operating conditions (surge) are shown. The one-stage, radial blower installed in the Institute of Turbomachinery TU of Lodz has been chosen owing to the available numerous experimental data. The pump calculations discussed in the third part concern a comparison of different turbulence models with the experimental results. In the last part devoted to the turbine design, the code usefulness is proved on the examples of the last stage design process

Design Optimization of Centrifugal Pump Using Radial Basis Function Metamodels

Optimization design of centrifugal pump is a typical multiobjective optimization (MOO) problem. This paper presents an MOO design of centrifugal pump with five decision variables and three objective functions, and a set of centrifugal pumps with various impeller shroud shapes are studied by CFD numerical simulations. The important performance indexes for centrifugal pump such as head, efficiency, and required net positive suction head (NPSHr) are investigated, and the results indicate that the geometry shape of impeller shroud has strong effect on the pump's performance indexes. Based on these, radial basis function (RBF) metamodels are constructed to approximate the functional relationship between the shape parameters of impeller shroud and the performance indexes of pump. To achieve the objectives of maximizing head and efficiency and minimizing NPSHr simultaneously, multiobjective evolutionary algorithm based on decomposition (MOEA/D) is applied to solve the triobjective optimization problem, and a final design point is selected from the Pareto solution set by means of robust design. Compared with the values of prototype test and CFD simulation, the solution of the final design point exhibits a good consistency

Radial fan controlled with impeller movable blades – CFD investigations

Modern classical power generation systems, based on power plants in Poland, where coal (hard bituminous coal or lignite) is the primary energy source, operate under variable loading conditions. Thus, all machines working in the technological system of the power generation unit are required to be adapted to variable loading, and, consequently, to operate beyond the design point of their performance characteristics. High efficiency of the process requires the efficiency of individual devices to be high, beyond the design point, as well. For both air and exhaust gases fans, an effective control system is needed to attain a high level of efficiency. As a result of cooperation between two institutes from the Faculty of Mechanical Engineering, Lodz University of Technology, and the Vibroson company, a new design of the radial fan with impeller movable blades, which allows for controlling the device operation within a wide range, has been developed. This new design and determination the performance characteristics for two geometrical variants of blades with computational fluid dynamics methods are presented. The obtained results have been compared to the results of the measurements of fan performance curves conducted on the test stand