Optimization study for high speed radial turbine with special reference to design variables

Numerical results of a theoretical investigation are presented to provide information about the effect of variation of the different design and operating parameters on radial inflow turbine performance. The effects of variations in the mass flow rate, rotor tip Mach number, inlet flow angles, number of rotor blades and hub to shroud radius ratio, on the internal fluid dynamics of turbine rotors, was investigated. A procedure to estimate the flow deviation angles at the turbine exit is also presented and used to examine the influence of the operating conditions and the rotor geometrical configuration on these deviations. The significance of the results obtained is discussed with respect to improved turbine performance

A calculation procedure for viscous flow in turbomachines, volume 1

A method for analyzing the nonadiabatic viscous flow through turbomachine rotors is presented. The field analysis is based upon the numerical integration of the full incompressible stream function vorticity form of the Navier-Stokes equations, together with the energy equation, over the rotor blade-to-blade stream channels. The numerical code used to solve the governing equations employs a nonorthogonal boundary fitted coordinate system that suits the most complicated blade geometries. A numerical scheme is used to carry out the necessary integration of the elliptic governing equations. The flow characteristics within the rotor of a radial inflow turbine are investigated over a wide range of operating conditions. The calculated results are compared to existing experimental data. The flow in a radial compressor is analyzed in order to study the behavior of viscous flow in diffusing cascades. The results are compared qualitatively to known experimental trends. The solution obtained provides insight into the flow phenomena in this type of turbomachine. It is concluded that the method of analysis is quite general and gives a good representation of the actual flow behavior within turbomachine passages

An investigation of viscous losses in radial inflow turbine nozzles

A theoretical model is developed to predict losses in radial inflow turbine nozzles. The analysis is presented in two parts. The first one evaluates the losses which occur across the vaned region of the nozzle, while the second part deals with the losses which take place in the vaneless field. It is concluded that the losses in a radial nozzle would not be greatly affected by the addition of a large vaneless space

A calculation procedure for viscous flow in turbomachines, volume 3

A method for analyzing the nonadiabatic viscous flow through turbomachine blade passages was developed. The field analysis is based upon the numerical integration of the full incompressible Navier-Stokes equations, together with the energy equation on the blade-to-blade surface. A FORTRAN IV computer program was written based on this method. The numerical code used to solve the governing equations employs a nonorthogonal boundary fitted coordinate system. The flow may be axial, radial or mixed and there may be a change in stream channel thickness in the through-flow direction. The inputs required for two FORTRAN IV programs are presented. The first program considers laminar flows and the second can handle turbulent flows. Numerical examples are included to illustrate the use of the program, and to show the results that are obtained

Lead Isotope Determinations by Mass Spectrometry and Its Application by Isotope Dilution Technique

A method for the determination of Lead isotope ratios by thermal ionization mass spectrometry (TIMS). This method also describes the application of isotope dilution mass spectrometry (IDMS) to the field of reference material (RM) characterization focusing on the approach. Emphasis is placed on IDMS measurements of highest analytical quality. Basic principles as well as the equation system are being recalled. The evaporation and ionization currents are determined for a measurement of isotopic ratios of head, employing double rhenium filament assembly in the ion source and Faraday cup as the detector using the presently available RM.         

Existence and Uniqueness of Limit Cycles in a Class of Planar Differential Systems

This paper is an extension to the recent results presented by M. Sabatini about the existence and uniqueness of limit cycles of a certain class of planar differential systems in order to include other new classes. A concrete example exhibiting the applicability of the result is introduced

Image Data Compression Based on Two Hybrids Algorithms

Image compression is a way to reduce the storage space of images. Therefore, image compression process increases the performance of such as the data transmission process.  This paper aims to present a new technique to compress digital image data. In this technique, two-hybrid algorithms were used to compress the image data.  The first system consists of one-dimensional discrete cosine transform (DCT), differential pulse code modulation (DPCM), and Huffman code for difference signal. The second hybrid system utilizes an expert system called Learning Automata (LA) to code the difference signal obtained from the first system. A compression ratio of about (10.8:1) was obtained from the first system. The second system provides a (20.6:1) compression ratio with non-noticeable impairment. The information loss is caused by a hybrid (DCT/DPCM) system, not by the LA system. The conclusion drawn is that using two-hybrid systems to compress the image data provides a high compression ratio. Furthermore, learning automata is preferable since it removes all the redundancy in the row data. However, in learning automata,  a Huffman code is determined pixel by pixel which takes a long time

The antimicrobial activity of oil-in-water microemulsions is predicted by their position within the microemulsion stability zone

It has been shown previously that thermodynamically stable oil-in-water microemulsions have significant antimicrobial activity against planktonic cells and biofilm cells over short periods of exposure. It was the aim of this study to identify whether the position of the microemulsion within the microemulsion stability zone of the pseudo-ternary phase structure predicts the efficiency of the antimicrobial action of the microemulsion. Microemulsions were formulated at different points within the microemulsion stability zone. Experiments were performed to observe the kinetics of killing of these microemulsions against selected test microorganisms (Pseudomonas aeruginosa ATCC 9027, Candida albicans ATCC 10231, Staphylococcus aureus ATCC 6538 and Aspergillus niger ATCC 16404). The results indicated that the antimicrobial activity of the microemulsion is dependant upon its position within the zone of stability and is greater nearer the centre of that zone. The results indicate that significant antimicrobial activity can be observed at all points within the zone of microemulsion stability, but that maximal activity is to be found at the centre of that area