Aleksandrs Urbahs, Konstantīns Savkovs, Gints Rijkuris and Darja Andrejeva
Corrosion is one of the most common naturally occurring processes studied by thermodynamics, which includes oxidation process, metal disruption, and its chemical and electrochemical effects under environmental influence. Corrosion of metal and equipment accounts for a considerable proportion of total corrosion losses, thus providing the impetus for further investigation and developments related to corrosion protection in order to provide transport systems and industry with corrosion preventive materials and tools.
Volodymir Kharchenko, Andrii Grekhov, Vasyl Kondratiuk and Karina Nagorna
Original models of “Aircraft-Satellite-Ground Station” communication channel based on IEEE 802.16 standard were built by using MATLAB Simulink. The influence of aircraft transmitter nonlinearity for different types of fading in the channel (Rayleigh and Rician) was studied and the possibility of correcting nonlinearity by using pre-distortion was revealed. The impact of space-time diversity (MISO 2 × 1) for different types of fading in channels was investigated. The effect of the Doppler frequency shift on the operation of communication channels was analyzed.
Aleksandrs Urbahs, Margarita Urbaha and Kristīne Carjova
The aim of this research is to develop a vertical rotation axis variable geometry wind turbine (WT). The experimental prototype is being manufactured with the help of CAM (Computer-aided manufacturing) technologies – computer-based preparation of the product manufacturing process. The Institute of Aeronautics of Riga Technical University is using CNC (Computer Numerical Control) machines for manufacturing the innovative WT and its components. The aerodynamic research has been done in T-4 wind tunnel at an air flow rate from 5 m/s to 30 m/s. The power increase of the variable geometry WT is a topical issue. Installation of such WTs in wind farms is possible and is subject to further research.
The rotating stall inception data analysis using Analytic Wavelet Transform (AWT) in a low-speed axial compressor was presented in the authors’ previous studies , . These studies focused on the detection of instability inception in an axial flow compressor when it enters into the instability regime due to the modal type of stall perturbation. In this paper, the effectiveness of AWT is further studied by applying it under different testing conditions. In order to examine the results of AWT on highly sampled data, at first, the stall data were acquired at a high sampling frequency and the results were compared with the conventional filtered signals. Secondly, the AWT analysis of stall data was carried out for the condition when compressor experienced a spike type rotating stall disturbance. The stall inception information obtained from the AWT analysis was then compared with the commonly used stall detection techniques. The results show that AWT is equally beneficial for the diagnostic of compressor instability regardless of the data sampling rate and represents an outstanding ability to detect stall disturbance irrespective of the type of stall precursor, i.e. the modal wave or spike.
Sigurdur Hrafn Gislason, Ruta Bogdane and Inese Vasiļevska-Nesbita
A Fatigue Monitoring Tool (FMT) model was constructed for an operational airline in order to manage the fatigue levels of their crews in accordance with Fatigue Risk Management System (FRMS) practices. This article describes the implementation of the Fatigue Monitoring Tool model and the airline’s aims to put the recent scientific findings on aviation fatigue into practical use. The model consists of proxy points allotted to various duties and rest periods.
Vasyl Kondratiuk, Eduard Kovalevskiy and Svitlana Ilnytska
Global satellite navigation system (GNSS) is by far the most cost-effective outdoor positioning technology currently available and used for many types of applications. In some cases a user may face difficult conditions, like restricted access to the navigation satellites due to natural or man-made phenomena. This paper presents an idea of an integrated positioning system capable of functioning under limited visibility conditions of navigation satellites. The system includes a digital antenna array, channels for converting radio navigation signals, a phase difference meter, a gyro platform with 3 gyros, an altimeter and a special calculator. With the help of mathematical modeling, the accuracy characteristics of the system are investigated by determining the coordinates of the carrier under conditions of a small number of available satellite signals.
Aleksandrs Urbahs, Sudip Das, Shravan Koundinya Vutukuru and Kristīne Carjova
Experiments and computational studies were carried out to get an understanding of the flow field around a rectangular supersonic intake with pointed cowl shape. Experiments include quantitative pressure measurements and flow visualization studies by using schlieren techniques. The effects of the presence of various cowl shapes on ramp surface have been obtained computationally at Mach 2.0. The experiments were carried out only for the pointed cowl. Schlieren Photographs were taken. Three-Dimensional simulations were made by using FLUENT at supersonic speed. The details of the experiments and computations are discussed.
Andrzej Ambrozik, Dariusz Kurczyński and Piotr Łagowski
Modern means of transport are basically powered by piston internal combustion engines. Increasingly rigorous demands are placed on IC engines in order to minimise the detrimental impact they have on the natural environment. That stimulates the development of research on piston internal combustion engines. The research involves experimental and theoretical investigations carried out using computer technologies. While being filled, the cylinder is considered to be an open thermodynamic system, in which non-stationary processes occur. To make calculations of thermodynamic parameters of the engine operating cycle, based on the comparison of cycles, it is necessary to know the mean constant value of cylinder pressure throughout this process. Because of the character of in-cylinder pressure pattern and difficulties in pressure experimental determination, in the present paper, a novel method for the determination of this quantity was presented. In the new approach, the iteration method was used. In the method developed for determining the volumetric efficiency, the following equations were employed: the law of conservation of the amount of substance, the first law of thermodynamics for open system, dependences for changes in the cylinder volume vs. the crankshaft rotation angle, and the state equation. The results of calculations performed with this method were validated by means of experimental investigations carried out for a selected engine at the engine test bench. A satisfactory congruence of computational and experimental results as regards determining the volumetric efficiency was obtained. The method for determining the volumetric efficiency presented in the paper can be used to investigate the processes taking place in the cylinder of an IC engine.
A technique is proposed to enhance the professionally important qualities of air traffic controllers at the stage of training on the basis of training group formation. The methodology is based on cluster analysis. The proposed criteria are based on the measure of the similarity of student qualities.
The research focuses on the development of an Unmanned Aircraft System. For design purposes, a rather new design method called Systems Engineering Approach is used. Development of the whole system takes much time and effort. This paper contains a concise description of the research on the preliminary development phase of Unmanned Aircraft System air vehicle. The method was first introduced by NASA and later developed by authors of books on aircraft design used for information purposes for design and are mentioned in references. The obtained results are rather realistic and promising for further design process. The method is simple and understandable, and it should be used more often to make it more steady and reliable.