Dušan Gordić

Modelling of Spool Position Feedback Servovalves

Abstract Based on a critical review of the previous research and the comprehensive theoretical analysis of all functional parts of two-stage electrohydraulic servovalves with a spool position feedback (a current amplifier, a torque motor, the first and the second stage of hydraulic amplification) a detailed mathematical model of the servovalves was created. The analysis was based on the fundamental laws of electromagnetism, fluid mechanics and general mechanics. The model parameters are physical quantities and the complexity of the model is only limited by the possibility of the correct numerical integration. It includes phenomena and quantities that are of influence on the behaviour of the servovalves, so it can predict their function in a wide range of expected working regimes. Results obtained with the numerical modelling on a personal computer were compared with the appropriate experimental data and the validity of the proposed model was confirmed with satisfactory accuracy.

Spool valve leakage behaviour

A four-way axial spool servovalve has such a design that flows through its restrictions can be presented by means of a hydraulic bridge. The characteristics analytically describe the fluid flow through spool orifices in the most of working regimes. The exceptions are regimes around the null characterised by an overlap existence when internal leakages dominate. Several mathematical models for the calculation of the internal leakage flows are presented in this paper including theoretical model worked out by authors. Modelling results are compared with appropriate experimental.

An implementation of infrared thermography in maintenance plans within a world class manufacturing strategy

The objective of the paper is to show the implementation of infrared thermography within World Class Manufacturing (WCM) maintenance strategy. The results from infrared thermography inspections in a food processing and packaging solutions company were presented. Applicability of the infrared thermography, during a two-year period, caused a substantial reduction the potential breakdown in the pilot area. Upon feasibility confirmation, the proposed method was spread to other production equipment of the company.

Review of efficiencies of cogeneration units using internal combustion engines

ABSTRACT The most frequently used technology in cogeneration units up to 10 MWe are internal combustion engines and the majority of the models are up to 500 kWe. There are dozens of reciprocating internal combustion engine–based cogeneration unit manufacturers and more than hundred suppliers in the market. In the article, data from supplier technical specifications of 583 units (34 manufacturers) is collected and analyzed. The authors proposed mathematical relations that show dependence of efficiencies on electric power that can be used for initial feasibility studies. Authors also have showed that value of 0.75 for power-to-heat ratio (proposed by EU Directive 2004/8/EC) does not always correspond to current market situation.

Integrating Energy and Environmental Management in Wood Furniture Industry

As energy costs continue to rise, industrial plants (even those of energy nonintensive industries such as furniture industry) need effective way to reduce the amount of energy they consume. Besides, there are a number of economic and environmental reasons why a company should consider environmental management initiatives. This paper provides a detailed guideline for implementing joint energy and environmental management system in wood furniture industrial company. It covers in detail all essential aspects of the system: initial system assessment, organization, policy development, energy and environmental auditing, action plan development, system promotion, checking system performance, and management review.

Energy efficiency in buildings, industry and transportation

This paper reviews the literature concerning the energy saving and outlines the importance of energy efficiency, particularly in three the most important areas: buildings, industry and transportation. Improving energy efficiency plays a crucial role in minimizing the societal and environmental impacts of economic growth and offers a powerful tool for achieving sustainable development by reducing the need for investment in new infrastructure, by cutting fuel costs, and by increasing competitiveness for businesses and welfare for consumers. It creates environmental benefits through reduced emissions of greenhouse gases and local air pollutants. It can offer social benefits in the form of increased energy security (through reduced dependence on fossil fuels, particularly when imported) and better energy services.

Energy Efficiency, Environmental Protection and Sustainable Development in Kragujevac (Serbia)

This paper presents a methodology development and the results achieved in the process of establishing energy management system in the City of Kragujevac (Serbia) and in its public services. The paper is an overview of influential factors in the field of energy management, analyzing their impact on raising the energy efficiency of individual utility service and the city of Kragujevac, as a whole. The paper also presents the most interesting scientific and research projects realized in the cooperation of several actors which were coordinated by Regional Euro Energy Efficiency Center Kragujevac. The municipal companies together with the city administration are the direct beneficiaries of the results realized in the following areas: ‐ Development of energy management in municipalities and the establishment of energy planning at the local level; ‐ Improvement of municipal services by applying energy efficiency measures in public enterprises: ‐ “Energetika” (heating), ‐ “Cistoca” (communal waste management), ‐ “Vodovod i kanalizacija” (water and waste water management); Promotion of ideas and projects realized in the field of energy management, environmental protection and sustainable development at the Festival of energy efficiency (starting from this year) held during the April.