Contents:

  • Andrzej Ambroziak Numerical Modeling of Elasto-Viscoplastic Chaboche Constitutive Equations Using MSC.Marc   abstract | full text
  • Andrzej Ambroziak Analysis of Non-Linear Elastic Material Properties of PVC-Coated Panama Fabric   abstract | full text
  • Maria Magdoń-Maksymowicz and Andrzej Z. Maksymowicz Simulating the Spread of the BSE Disease: a Cellular Automata Approach   abstract | full text
  • Jerzy Świrydczuk Unsteady Performance of an HP Turbine Stage Optimised for Steady Flow Conditions   abstract | full text
  • Jerzy Głuch Application of Artificial Neural Networks (ANN) as Multiple Degradation Classifiers in Thermal and Flow Diagnostics   abstract | full text
  • Piotr Lampart and Romuald Puzyrewski Numerical Analysis of Adaptive Control in LP Turbines   abstract | full text
  • Andrzej Frąckowiak and Michał Ciałkowski Explicit Estimation of an Integral in a Domain by the Multiple Reciprocity Method with the Use of Inverse Operations   abstract | full text
  • Jiabing Wang, Yingda Ou and Keqi Wu Numerical Analysis of Internal Flow Phenomena in a Multi-Blade Centrifugal Fan   abstract | full text
  • Andrzej Januszajtis At the Threshold of Maturity   abstract | full text

Abstracts:

hAndrzej Ambroziak Numerical Modeling of Elasto-Viscoplastic Chaboche Constitutive Equations Using MSC.Marc

The aim of the present paper is to propose a special kind of finite element procedure for dynamic and static analysis of civil engineering structures (e.g. trusses, beams, shells and spatial structures) including elasto-viscoplastic models. The Chaboche model with damage has been chosen from the wide range of available elasto-viscoplastic constitutive models for numerical calculations. The main advantage of the presented approach is the possibility of interference in subroutines and adjusting them to a particular problem (e.g. altering the form of constitutive equations). A userdefined UVSCPL subroutine has been proposed to introduce the elasto-viscoplastic model into the MSC.Marc system.

 

hAndrzej Ambroziak Analysis of Non-Linear Elastic Material Properties of PVC-Coated Panama Fabric

The aim of the present paper is to propose a method of laboratory tests to determine non-linear elastic properties of coated Panama fabric. The material parameters are specified on the basis of uniaxial tensile tests in the warp and weft directions. Techniques based on the least squares' methods are used in the determination process. Reduction concepts of the strength parameters are proposed in order to take into account rheological effects in the fabric. Numerical applications to MSC.Marc, a commercial program, are presented. A user-defined HOOKLW subroutine is used to introduce the non-linear elastic properties of the PVC-coated fabric into the MSC.Marc system.

 

hMaria Magdoń-Maksymowicz and Andrzej Z. Maksymowicz Simulating the Spread of the BSE Disease: a Cellular Automata Approach

The rules of evolution applied in the cellular automata approach may correspond to the propagation of the mad cow disease. In a computer simulation of the BSE disease's spread both inherited and infectious mechanisms are accounted for. The initial population of items is randomly distributed on a two-dimensional square lattice, Nx × Ny = 1000 × 1000, with a fraction of 1 percent the items already infected. Alternatively, faulty prions may spontaneously develop during the simulation with a very small frequency. Our results indicate a critical probability, pc , of BSE transmission, so that for p below the threshold the population recovers. For p > pc the disease is launched in the population with a dynamic equilibrium between the healthy and infected fractions of the population. The threshold is very sensitive to spatial clustering of the population and the detailed rules for the disease's onset, evolution and propagation.

 

hJerzy Świrydczuk Unsteady Performance of an HP Turbine Stage Optimised for Steady Flow Conditions

The article focuses on the examination of the unsteady performance of an HP turbine stage the blades of which were previously optimised for steady flow conditions. For the purpose of this examination, two pairs of initial and optimised stages of comparable output parameters were selected. The results have revealed that the modification of the blade profile in the optimisation process made the rotor blades more vulnerable to unsteady flow fluctuations, which eventually cancelled a considerable part of the stage efficiency gained from the steady flow optimisation.

 

hJerzy Głuch Application of Artificial Neural Networks (ANN) as Multiple Degradation Classifiers in Thermal and Flow Diagnostics

Application of a neural network of the classifier type for diagnostic purposes is presented. The described ANN solves the task of recognizing causes of degradation of power units' thermal cycle components. Verification of the applied ANN responses is based on the presented research in the numerical simulation of selected power installations. The obtained results could be used in diagnostics of power cycle being properly measured. Considerably good obtained results prove that the ANN technique can be applied as an automatic detector of operational faults. Thus an ANN can serve as a support tool for operational decisions. The present work also offers a way of reducing training time.

 

hPiotr Lampart and Romuald Puzyrewski Numerical Analysis of Adaptive Control in LP Turbines

A new design idea of adaptive control in LP steam turbines under conditions of (1) extraction of steam to the extraction point and (2) seasonal changes of pressure in the condenser is described in the paper. Nozzle blades of a stage located directly downstream of the extraction point or of the exit stage located upstream of the exit diffuser have adjustable trailing edges that can adapt the geometry of the blading system to changing flow conditions. The idea is validated numerically on a group of two exit stages of an extractionćondensation turbine of power 60MW. A series of flow calculations are made using a code FlowER for solving the flow of compressible viscous gas in a 3D turbomachinery environment. As a result of calculations, characteristics of the design, including the mass flow rate, flow angles in characteristic sections, enthalpy losses and turbine power are obtained in a range of given pressure drops and nozzle blade stagger angles. The adequate position of the nozzle blade is found based on these characteristics. Advantages of adaptive control in the form of increase of turbine efficiency and power are also estimated.

 

hAndrzej Frąckowiak and Michał Ciałkowski Explicit Estimation of an Integral in a Domain by the Multiple Reciprocity Method with the Use of Inverse Operations

The paper presents two methods of solving the Poisson equation. One is based on the multiple reciprocity method. An analytical form of the basic solution obtained by means of inverse operation technique enabled assessing the method's error. The other is based on source function expansion into a series according to polyharmonic functions. Further polyharmonic functions have been obtained through inverse operations (with the ∆−1 operator) applied to polyharmonic functions. Numerical results have confirmed perfect efficiency of both methods.

 

hJiabing Wang, Yingda Ou and Keqi Wu Numerical Analysis of Internal Flow Phenomena in a Multi-Blade Centrifugal Fan

A three-dimensional, steady, incompressible, turbulent flow field inside a multi-blade centrifugal fan used in an air-conditioner has been analyzed numerically. Reynolds-averaged NavierStokes equations with the standard k-ε turbulence model have been discretized by the finite volume method. The calculation results have shown complex three-dimensional characteristics of the flow, especially in the blade passages near the shroud side. The results have revealed a boundary layer separation at the leading edge on the blade suction surface, the flow reversal from the high pressure region inside the volute to the low pressure region near the impeller inlet, the flow recirculation near the shroud side, a jet-wake pattern at the rotor exit, the pressure fluctuation on the blade surface, etc. Some of the numerical results agree well with previous experiment.

 

hAndrzej Januszajtis At the Threshold of Maturity

 

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