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This study represents the first phase of research into the relationship between indoor air quality and the architectural and thermotechnical characteristics of buildings. The focus is on specific categories of users such as the elderly. The research methodology based on the scientific method is presented, which examines the condition of real objects on the territory of the Republic of Serbia. The aim is to provide a structured methodology for establishing the link between architecture, mechanical systems and indoor air quality, on evidence-based design principles, in order to propose guidelines for future interventions in the construction or adaptation of facilities for the elderly. Second objective of the study is to point to the relevance of contextualized interventions according to the target user groups and reinforce application of scientific evidence in contemporary building design. Namely, tailor-made solutions would be necessary in the future, and consideration towards different user needs should be framed and structured to meaningfully operationalize the design.

Purpose The purpose of this paper is to improve the lubrication and remove as much as possible of the heat generated in the bearing assembly, embedded in the jet engine. Design/methodology/approach To determine the necessary values of the air pressure and oil amount, an experimental approach is used. For that purpose, a custom made test rig is developed. Findings Less amount of oil makes better lubrication conditions, reflected in the smaller temperature of the bearings. Concerning the air pressure, too high and too low air pressure deteriorates the lubrication parameters. An optimum value should be determined experimentally. The influence of oil amount is remarkably bigger than the influence of air pressure. Originality/value This experimental investigation provides an easy and fast way to improve the high-speed bearings lubrication parameters.

An increased number of requirements for supersonic wind tunnel tests at high angles of attack (AoA) opened the problem of the validation of a high-AoA wind tunnel setup in the Experimental Aerodynamics Laboratory of VTI (Military Technical Institute) in Belgrade. Tests of the supersonic-hypersonic HB-2 models were performed at Mach numbers 1.5 to 4 at AoA up to +30°. A new bent sting was used as the model support, shifting the AoA range of the wind tunnel model support. Obtained data were correlated with results of previous tests performed in the same wind tunnel in the lower-angle-of-attack range and with available test results from other wind tunnel facilities. The results are found to be useful as supersonic test cases for both experimental and numerical researchers

This paper describes a new approach for measuring the axial force on a turbo-jet engine rotor from the Phoenix family. The axial force occurs due to pressure distribution from the operating fluid along the surfaces of the rotor structure. The case study is the Phoenix 100 turbo-jet engine which is specific because it has a high axial force that loads a relatively small, high speed bearings set. In order to define the maintenance period of the bearing system, it was crucial to measure this force. Since the conventional and commercial sensors were not applicable to this construction, a specific solution was created and implemented in the acquisition system and experimentally verified during the engine run on its test stand.

The multifunctional bulkhead is an assembly which divides the compressor and turbine space (cold and very hot area) in the gas-generator for turbo-jet and turbo-haft engines. The loads of this bulkhead present an interaction of mechanical, thermal, fluid stream and pressure effects which produce extreme operating conditions and specific kinds of failures. Additional unfavorable effects produce a high gradient and a variation of these loads. The article contains a numerical identification of bulkhead operating conditions and an innovative design of the bulkhead for this purpose. Design development is based on the specific failures which are analyzed together with causes and design possibilities for failure prevention. For this purpose, in the existing design approach “Property-based Design”, a specific procedure named Failure-based design – FBD is applied. The paper also includes CFD analysis, numerical analyses of temperature, stress and deflection distribution of the multifunctional bulkhead. The presentation of the test stand and results of gas-generator testing together with the design solution of the multifunctional bulkhead, are also part of the article.

The paper defines the minimum number of parameters which are sufficient for monitoring and controlling the gas generator operation in an innovative design of a tip-jet helicopter propulsion system. Firstly, the gas generator is tested separately on its test stand installation with several selected measuring and controlling parameters. Some ideas for implementing sensors for measuring certain parameters are presented in the paper. Then, a few parameters are selected as sufficient for controlling the tip-jet helicopter and experimentally verified on a helicopter hovering test as the minimum required parameters.

Aerodynamic characteristics of an AGARD-C model in the transonic Mach number range in the 1.5 m T-38 trisonic wind tunnel of the Military Technical Institute (VTI) in Belgrade were compared with those from other wind tunnel laboratories. Inter-facility correlations were based on test results of physically the same model in the NRC and INCREST trisonic wind tunnels and in the T-38 wind tunnel during its early period. Analysis of test results confirmed an excellent measurement chain in the T-38 wind tunnel, except small differences in the pitching moment coefficient data obtained in inverted runs procedurally performed for test section symmetry check. The AGARD-C model is being known for the high sensitivity of the pitching moment to local conditions and it has been concluded that the effects may have been caused by the asymmetry of the model support mechanism

Current trends in the development of control systems involve disproportionately high costs for embedded software integration and testing techniques that rely almost exclusively on exhaustive testing of more or less complete versions of complex systems. Wind tunnel control systems are not an exception. A formal methodology for supersonic flow control does not exist, which is not acceptable from a perspective of cost, reliability and safety of wind tunnel operations. The cascade nonlinear feedforward-feedback stagnation pressure controller proposed here is intended to address this deficiency in the operation of a supersonic blowdown wind tunnel. By focusing on a model-based approach using physical principles and hierarchical design methodologies, a systematic design method is offered for stagnation pressure control in particular, and control of flow parameters in general. The suggested mathematical model of supersonic flow in a blowdown wind tunnel is analyzed and main challenges of using a model-based approach are identified, with an emphasis on high process nonlinearity and an infinite number of possible operating conditions. The model is applied to the VTI Belgrade T-38 blowdown wind tunnel to identify the feedforward component that accurately predicts the nonlinear response of the facility. The Simulink® models of the facility and the proposed controller are developed to tune the feedback component in numerical simulations and verify the controller. The wind tunnel control system is implemented as an embedded distributed hierarchical system and experiments to verify the suggested control method are realized at Mach numbers 1.0–4.0. Both simulations and experiments demonstrate that feedback calculation successfully captures nonlinearities in the facility response, enabling a simple linear feedback controller with a single set of control terms to be used only to trim out additional deviations for an entire operating range of the facility. The feedforward-feedback architecture thus improves setpoint reference tracking, while the cascade architecture improves disturbance rejection performance compared to common single loop solutions. Combined within a single system, they eliminate large transient pressure overshoots typical for blowdown facilities, decrease the setpoint settling time and improve overall stagnation pressure control accuracy. In addition, system integration and testing time and costs are significantly reduced by analyzing physical properties of the process and taking them into consideration during early stages of the system development.

The paper critically analyzes the process of realization of energy efficient kindergartens in the City of Belgrade whose designs are obtained in the open public urban architectural competition. The process initiated, financed and realized by the city government of the City of Belgrade is an example of an effort toward meeting the EU directives and achieving the Energy Community objectives in the field of energy efficiency and usage of renewable energy sources, where facilities for public use must lead and be examples of the best practice. The whole process is analyzed, starting from planned conditionality of urban-architectural competition announcement through special conditions concerning energy efficiency and usage of renewable energy sources to construction and use of zero energy kindergartens, with a special analysis of the energy efficiency parameters of one of the kindergartens chosen as a representative of a good practice of competition solutions implementation of energy efficient facilities for the public use.

Tests of standard models serve to confirm the overall accuracy and measurement quality in a wind tunnel facility and to confirm confidence in results obtained. The wide-accepted criteria for evaluation of the wind tunnel measurement quality are based on methodology of a few supposedly identical tests of the standard model. Wind tunnel data uncertainty is being considered in the form of test data repeatability. Based on this methodology the overall reliability of the Serbian trisonic wind tunnel is certified and verified. Test data are also correlated with those from other wind tunnel facilities.

A new design of gear transmission unit with continual variation of gear transmission ratio, for application in wind turbines (WT), has been developed. By variation of transmission ratio the speed of output shaft is 1500 rpm, constant independently of the wind speed. The article contains the presentation of a testing rig and the testing procedure of this design. The testing rig is based on back-to-back connection and power circulation and the testing procedure on simulation of the WT service conditions. The objective of testing process is identification of gearbox operating features and behavior, gearbox reliability and durability.

Fretting is an insidious failure difficult to predict when it will occur along the service life of a mechanical structure and to take it into consideration in the design stage. The article contains presentation of some of these failures, the analysis of causes which produce fretting fatigue and fretting wear. Testing methodology for fretting fatigue is developed but not in a full sense for fretting wear testing. The main objective of the work is the development of the testing device for fretting wear failure probability identification and analysis of the possibility to include this probability in reliability for design of the mechanical structure.

Research in the area of wind tunnel flow parameters control has been intensified in recent years, in an attempt to improve quality and efficiency of the wind tunnel operation. In this paper, stagnation pressure transient control in a supersonic blowdown-type wind tunnel is considered, with the aim of increasing available measurement time and bringing improvement in the operation efficiency. The stagnation pressure control strategy in the VTI Belgrade T-38 wind tunnel is analyzed. A mathematical model of a blowdown wind tunnel is developed and applied to the T-38 test facility. The model is used to incorporate a modified stagnation pressure transient control in the original T-38 control system, in order to establish the required stagnation pressure with the shortest possible settling time. The actual wind tunnel tests confirm model-predicted decrease of the pressure settling time and increase of available measurement time, bringing significant improvement in the facility operation efficiency.

The flow parameters control in wind tunnels is an area of intense research in recent years, with the aim of improving quality and efficiency of the wind tunnel operation. In this paper, an attempt is made to contribute to a better understanding of the stagnation pressure control in supersonic blowdown-type facilities. The stagnation pressure control strategy in the VTI Belgrade T-38 wind tunnel is discussed. An improved mathematical model for a supersonic wind tunnel is suggested and applied to the T-38 facility. Comparisons of simulation and experimental data are made to demonstrate accurate prediction of the facility response in supersonic flow conditions by the mathematical model. The model is used to incorporate a modified feedforward control in the original T-38 wind tunnel control system. The actual wind tunnel tests confirm model-predicted decrease of flow stabilization time and increase of available measurement time, bringing significant improvement in the wind tunnel operation efficiency.

This paper presents all the significant nonlinearities that exist in the description of an electro hydraulic actuator for flexible nozzle thrust vector control. Starting from practical possibilities of the theory of a nonlinear system (which are based on the analyses of one nonlinearity or one equivalent nonlinearity in the proximity of the linear description of an actuator), this paper explores the possibilities of additional analyses of a nonlinear electro hydraulic actuator for flexible nozzle thrust vector control. These explored possibilities can provide information that is useful for the design of the control algorithm, as well as for the general design of a flexible nozzle and actuator system.

The paper analyzes the potential of renewable energy sources within the area of City of Belgrade, and explores the possibilities of their further implementation in the field of renewable energy sources and energy efficiency, in line with mandatory EU Directives. A synergetic approach has been proposed in the recommendations for the implementation of goals/targets and policies in the fields of renewable energy sources and energy efficiency in the City of Belgrade. They put an emphasis on the importance of implementation of the strategic documents of the City. Recommendations on have been provided regarding the required institutional preconditions that have to be met in order for these goals to be achieved, as well as urbanistic and building design-related measures/standards in achieving energy efficiency. Key words: energy efficiency, renewable energy sources, strategies related to energy, sustainable development, the City of Belgrade

The authors are of the opinion that there is no alternative to sustainable development, and discuss on thesis that sustainability is now a key driver of innovation, but also its essential requirement. This paper discusses the sustainability as a concept that has, above all, the environmental, economic, social and cultural dimension. The aim of the study was to understand sustainability as a fundamental development principle and key benchmark in organisation and development of cities in the future. This paper explores the meaning of innovation processes, sustainability and innovation in urban planning, innovative approaches to sustainable urban development, initiatives in urban sustainability, the key elements of the implementation, modalities of providing financial resources for sustainable projects of public interest, as well as identification of areas suitable for innovation in urban planning, relying on the good practices implemented through multi-sector sustainable projects. In a broader sense, the objective of this paper is to emphasize the need: to promote concept of human dimension in urban development, to direct continual urban development towards 'green' orientation, to implement innovative and smart technologies in the management of modern cities; to promote public participation and multi-sectoral policies in urban development, and to encourage and stimulate sustainable (urban) innovation.

The emerging interdisciplinary field of mechatronics and integrated technical systems is becoming increasingly important to architecture. Technology comprised of sensors, controllers and actuators allows architects to reconsider the relationship between buildings and their environment, as well as between buildings and their users. The architectural education is finding itself on an uncharted territory while trying to introduce interdisciplinary collaboration into its own curricula. This paper will present outcomes of the research seminar conducted at University of Belgrade, Faculty of Architecture focused on the role of mechatronics and integrated technical systems in architecture. The discussion will focus on the notion of spatial adaptability and three possible reasons why architectural elements should move: efficiency, aesthetics and functionality.

U ovom radu se predlaže inovativnu konstrukciju ispitnog stola za precizno mjerenje vektora potiska raketnog motora tijekom njegovog rada. Jasno je izložena konstrukcija ispitnog stola kao i procedure te matematički model za kalibraciju ispitnog stola. Metoda obrade podataka dobivenih ispitivanjem kao i rezultati ispitivanja "jet tab" sustava za upravljanje vektorom potiska detaljno su prezentirani. Eksperimenti su pokazali da je ispitni stol iznimno funkcionalan, a da dobineni rezultati imaju odličnu ponovljivost i poklapanje s rezultatima autora koji su koristili ispitne stolove drugačije konstrukcije za mjerenje istog ili sličnog mehanizma za upravljanje vektorom potiska., This study proposes an innovative test stand design to accurately measure rocket motor thrust vector during its operation. Test stand design is clearly presented as well as procedure and mathematical model for its calibration. A method of processing data obtained from the experiments and the results of the jet tab system for thrust vector control are presented in detail. Experiments have shown that the test stand is highly functional and the results obtained have excellent repeatability and matching with the results of the other authors who have used different construction test stands for measurement of the same or a similar mechanism for thrust vector control.

Ustrojen je fizički model spojlera i kupolastog deflektora u sustavu upravljanja vektorom potiska (UVP) razmatrajući zaključke prethodnih i sadašnjih ispitivanja. Prema logici fizičkog modela razvijen je matematički model. Algoritam modela i rezultati su analizirani i objašnjeni. Konačno, rezultati modela su potvrđeni testovima realnog motora., Physical model of spoiler and dome deflector thrust vector control (TVC) system was established considering previous and current research observations. According to logic of physical model an engineering mathematical model is derived. Model algorithm and results were analysed and explained. Finally, model data were confirmed with real motor tests.

Težište ovog rada je upravljanje elektromehaničkim aktuatorom (EMA) za primjene u zračnom prostoru. Upravljanje EMA je ostvareno uporabom pozicijskog regulatora i upravljanja koje kombinira položaj i brzinu regulatora. Osnovna smjernica bila je smanjenje gubitaka snage, zagrijavanja i potrošnje struje u sustavu. Jedno od važnih područja u okviru pogona promjenljivim brzinama motora su operativne granice sustava. Danas se operativne granice pogona s promjenljivim brzinama motora postavljaju na osnovu operativnih granica pogona na bazi prosječnih vrijednosti, npr. ograničenjima struje i snage na preporučene vrijednosti. To dovodi do nedovoljne iskorištenosti sustava i velikih gubitaka korisne snage. U ovom radu, u prvom dijelu je predstavljen osnovni koncept elektromehaničkog aktuatora (EMA) i njegov matematički model, zatim je prikazano upravljanje položajem i brzinom elektromehaničkog actuatora uporabom PID regulatora. U drugom dijelu usporedo se daje prikaz simulacija vlastite konstrukcije upravljanja položajem i brzinom pomoću PID regulatora, uporabom SIMULINK-a u MATLAB-u., Main focus of this paper is control of electromechanical actuator (EMA) for aerospace applications. Control of EMA done using position regulator and control which combine position and speed regulator is shown. The main guideline is to decrease power losses, heating and current consumption in the system. One of the important areas within the field of variable speed motor drives are the system’s operational boundaries. Presently, the operational boundaries of variable speed motor drives are set based on the operational boundaries of single speed motors, i.e. by limiting current and power to rated values. This results in under-utilization of the system, and places the motor at risk of excessive power losses. In this paper, the first part represents general concept of electromechanical actuators and mathematical modelling of the system; then the control of position and speed of electromechanical actuator (EMA) by using PID controller is presented. The second part shows simulations of our own design of control speed and position by PID controller using SIMULINK and MATLAB software.

This paper introduces a new physical model of the gas flow through the 2D nozzle with the tilted obstacle in exit section. Experimental research on the 2D full span model in the supersonic indraft tunnel, which includes over three hundred tunnel runs, are presented. Variable geometric parameters were: nozzle shadow area, obstacle-nozzle wall angle, obstacle-nozzle gap and nozzle area ratio. In its conclusion, the paper discusses results and presents some suggestions for the future research., Rad predstavlja novi fizički model strujanja u 2D mlažnjaku sa preprekom u izlaznom presjeku. Predstvljeno je eksperimentalno istraživanje koje uključuje preko 300 testova realiziranih s 2D mlažnjakom realnih dimenzija u supersonicnom tunelu. Promjenjivi geometrijski parametri tijekom eksperimenata: zasjenčena površina mlažnjaka, kut između prepreke i zida mlažnjaka, razmak između prepreke i izlaznog presjeka mlažnjaka, geometrijski stupanj širenja mlažnjaka. U zaključku su komentirani rezultati i date preporuke za dalji rad.

The paper mainly focuses two major areas of electromechanical actuator system composed of power screw, spur gear train and Brushless DC Servo Motor. First it describes control of electromechanical actuator system with three level of current controller which is composed of power amplifier, DSP module and interfacing circuitry. The non-linear model of the three level controllers developed in SIMULINK environment is presented. A second point which was included in this study is the comparison of two control strategies i.e. three level controller and PWM current controller. The main outcomes of the study is that three level controller is simple in construction and much more stable. This is much suitable for higher reduction systems, short missions and low power density actuators; however it has few limitation that make it unsuitable for applications such as high power density, long missions and direct drive system., Ovaj se rad u osnovi fokusira na dvjema glavnim područjima vezanih za elektro mehanički pokretački sustav, koji je sačinjen od pogonskog vijka, prijenosnog sistema i istosmjernog motora bez četkica. Prvo je opisano upravljanje elektro mehaničkim pokretačkim sustavom pomoću kontrolera sa tri nivoa struje, koji je sačinjen od DSP procesorskog modula i elektronskog kola sa pojačivačem. Prikazan je i nelinearan model kontrolera sa tri nivoa struje koji je razvijen u SIMULINK okruženju. U radu je također prikazana usporedba dvaju tipova kontrole: kontroler sa tri nivoa struje i PWM strujni kontroler. Glavni zaključci na osnovi dobijenih rezultata su da je kontroler sa tri nivoa struje jednostavniji za izradu i mnogo stabilniji. Njegova primjena posebno je pogodna u sustavima sa velikom redukcijom, u kratkotrajnim misijama i sustavima s manjom izlaznom snagom; ipak ukazano je i na nekoliko nedostataka: nije preporučljivo koristiti ga pri većim snagama i u dužem vremenskom razdoblju uslijed većih toplotnih gubitaka.