Journal of Mechanical Engineering 51 (2005) 6

 

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An Analysis of the Combustion Conditions in the Secondary Chamber of a Pilot-Scale Incinerator Based on Computational Fluid Dynamics

Corresponding author - Filip Kokalj

Authors - Niko Samec - Leopold Škerget

Abstract

A numerical analysis of the combustion in the secondary chamber (thermoreactor) of a two-stage pilot-scale incinerator using computational fluid dynamics (CFD) is presented. The focus of the research was on those physical conditions that ensure complete combustion, i.e., temperature, residence time and turbulent mixing. Various versions of the CFD program package CFX were used; they offer different combustion models for specific types and forms of combustion processes. The selection of an appropriate combustion model was based on a comparison of the numerical results and experimental values of some combustion macro parameters in a thermoreactor. Combustion models based on a one-step bimolecular chemical reaction and models based on multi-step reactions were used; this enabled a more detailed prediction of the combustion conditions in the secondary chamber of a pilot-scale incinerator. The products of incomplete combustion that are very important for the designing and optimization of combustion devices can be predicted by applying multi-step reaction models. An ultimate analysis of the complete combustion conditions was made based on a selected combustion model by considering those different operating conditions, causing variations in the quantity, composition and heating values of the gases coming from the primary chamber. The important conclusions are that the secondary and tertiary air intakes and the relationship between them have the greatest influence on the combustion quality in the thermoreactor.

Keywords - combustion, numerical analysis, combustion models, computational fluid dynmics

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 51(2005)6, 280-303
UDC 662.92:536.46

An Analysis of the Combustion Conditions in the Secondary Chamber of a Pilot-Scale Incinerator Based on Computational Fluid Dynamics (pdf)

 

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Finding and Exploiting the Hidden Logistic Potentials in a Company

Corresponding author - Janez Kušar

Authors - Tomaž Berlec - Jože Duhovnik - Janez Grum - Marko Starbek

Abstract

Companies are nowadays confronted with new challenges: simultaneously they are dealing with the globalization of business and acting on local markets, the standardization and customization of products for fastidious customers and increased competition. In these circumstances the only successful companies are those which can respond quickly to market changes, i.e., they have a short response time for the fulfilment of customer requirements (a short delivery time and reliable delivery in addition to a competitive price and high quality). Consequently, a reduction of the mean inventory, the range and the lead time of the working systems in the company is an ever increasing strategy that ensures the customer’s satisfaction and an increase in growth and profit for the company. The article shows how the tools for modelling the flow of orders through working systems can be used to find and exploit the hidden logistic potentials of working systems in a company. Here we present the results of finding and exploiting the hidden logistic potentials of working systems in the tool-production department of the “ETI Ltd.” company from Izlake, Slovenia.

Keywords - working systems, lead times, inventory systems, performance, logistic potentials

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 51(2005)6, 304-329
UDC 65.012.3:658.286

Finding and Exploiting the Hidden Logistic Potentials in a Company (pdf)

 

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An Improved Method for Determining a Forming Limit Diagram in the Digital Environment

Corresponding author - Aleš Petek

Authors - Tomaž Pepelnjak - Karl Kuzman

Abstract

The deformation limits of sheet metals, which are determined with localization and fracture, represent an important parameter for the analyses of sheet-metal forming processes. The forming limits of sheet metal are represented by a forming limit diagram (FLD), which shows the various deformation states. For an experimental determination of a FLD extensive and expensive tests are necessary. An alternative method for determining the forming limit curve (FLC) is an analysis performed using numerical simulations. This paper introduces a method for determining the forming limit curve for the whole range of the FLD for sheet metal. A simulation of the Marciniak test with the finite element method (FEM) was performed for hot-galvanized steel using the Abaqus program. The criterion for determining the FLD with a numerical simulation is presented. Finally, the numerically obtained forming limit curve is compared with an experimental curve.

Keywords - sheet metal forming, forming limit curves, finite element methods, numerical simulations

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 51(2005)6, 330-345
UDC 621.98.04:539.375

An Improved Method for Determining a Forming Limit Diagram in the Digital Environment (pdf)

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Simulating the Lateral Vibrations of Passenger Wagons

Corresponding author - Žilvinas Bazaras

Authors - Mindaugas Leonavičius

Abstract

In this investigation we look at the dynamics of railway passenger wagons, the methods of providing solutions and the dynamic processes of a carriage. Using the program package ADAMS/Rail, a mathematical model is created to calculate the transversally forced oscillations of the carriage. During the creation of this model the geometrical and mechanical characteristics of the carriage are estimated. In addition, the functions describing the sinusoidal irregularities of the road in the plane are presented for cases when the sinusoidal wavelength is 10 m, 20 m, 30 m and 40 m, and the wave amplitude is 0.0025 m, 0.0035 m, 0.0050 m and 0.0065 m. With the help of these functions the excitation influence on the dynamic system is described.

Keywords - railway passenger cars, dynamics, lateral vibrations, mathematical models

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 51(2005)6, 346-355
UDC 629.4.015:004.94

Simulating the Lateral Vibrations of Passenger Wagons (pdf)

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