Abstract This study utilized a transparent direct methanol fuel cell, with serpentine channels with a width of 2 mm and an initial depth of 2 mm, and investigated the relationship between the behaviours of carbon dioxide (CO2) slugs, product water accumulations, and voltage fluctuation. It examined the exhaust volumes of CO2 slugs and product water accumulations from the channels over time, comparing an anode channel with a depth of 1.2 mm to one with a depth of 2 mm (without changing the cathode depth of 2 mm, nor the width of 2 mm in both the anode and the cathode). Results indicated that cell voltage fluctuated, rising while CO2 slugs were ejected, and falling between ejections. In the case of an anode channel depth of 2 mm and a lower methanol-water solution flow rate, CO2 slugs were ejected less frequently, so cell voltage fluctuated widely. (Product water accumulations in the cathode had a minimum effect on this cell voltage fluctuation.) In the case of a higher methanol-water solution flow rate, CO2 slugs were ejected more frequently, with less exhaust volume per CO2 slug, reducing the fluctuation in cell voltage. Finally, with an anode channel depth of 1.2 mm, the exhaust volume per CO2 slug became even smaller, and these small CO2 slugs were rapidly ejected. With this shallow depth, the cell voltage increased with a lower methanol-water solution flow rate, but decreased with a higher methanol-water solution flow rate by crossover.
Abstract The methodology of simulation of a rotorcraft flight has been developed and applied to simulate several stages of flight of light helicopter. The methodology is based on coupling of several computational models of Computational Fluid Dynamics, Flight Dynamic. The essence of the methodology consists in calculation of aerodynamic forces acting on the flying rotorcraft by solving during the simulation the Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations. In this approach, the rotorcraft is flying inside the computational 3D mesh modelling the space filled with the air. The flight simulation procedure is completely embedded in the URANS solver ANSYS FLUENT. Flow effects caused by rotating blades of main or tail rotor are modelled by application of the developed Virtual Blade Model (VBM). In this approach, real rotors are replaced by volume discs influencing the flow field similarly as rotating blades. Time-averaged aerodynamic effects of rotating blades are modelled using momentum source terms placed inside the volume-disc zones. The momentum sources are evaluated based on the Blade Element Theory, which associates local flow parameters in the blade sections with databases of 2D-aerodynamic characteristics of these sections. Apart of the VBM module, two additional UDF modules support the simulation of helicopter flight: the module responsible for modelling of all kinematic aspects of the flight and the module gathering the momentary aerodynamic loads and solves 6 DOF-Equations describing a motion of the helicopter seen as solid body. Exemplary simulation of helicopter flight, starting from a hover, through an acceleration and fast flight until a deceleration and steep descent, has been discussed.
Abstract Transport telematics systems integrate information technology with telecommunications for their use in various transport systems. Thanks to the use of advanced technical solutions and modern telecommunications and IT systems, it is possible to implement additional innovative services. They can be used to rationalize the process of using and maintaining means of transport. Modern vehicles are equipped with telematic on-board systems. Such solutions combine various electronic devices used in the vehicle. For this purpose, bus solutions are used, thanks to which it is possible to control individual systems and devices. It is also possible to use the transmitted data to detect negative exploitation phenomena during vehicle use (e.g. glazing phenomenon, work in the upper engine rev range with too low coolant temperature, intensive work compressor of the high air pressure system being a symptom of inability of pneumatic systems). This is possible because the data being sent has a specific information resource. Thanks to this, to can be concluded about the loss of the exploitation potential of the vehicle. This approach will be used to rationalize the technical service of the vehicle fleet, with regard to profiling. Using exploitation data, received via a telematic interface from vehicles, it is possible to profile the rolling stock. It consists in distinguishing individual sets of vehicles due to certain reliability and exploitation properties. This approach allows for the specification of the rolling stock exploitation, giving the opportunity to rationalize the use and exploitation. The publication presents the author’s graph of the exploitation process taking into account the profiling of the vehicle fleet. The application of the presented approach will contribute to the improvement of the value of certain vehicle reliability and exploitation indicators.
Abstract In this article a review of rotor, hub constructions were presented. Discussed rotor’s hub is made of composite or aluminum alloys materials. Two types of rotor hub were presented (four-blades and two-blades teetering rotor hub), each of them are dedicated to gyroplanes. Typical gyroplane main rotors are characterized by simple design, especially in case of rotors for light gyroplanes. In the following part of the article the type of strength tests required by certification process were shown. The test programs based on legal aspects of admission to the flight tests taking into account legislation such as CS 27 (Subpart C – Strength Requirements), CAP 643 British Civil Airworthiness requirements Section T Light gyroplanes, ASTM F2972. Furthermore, this article discusses strength tests of gyroplane rotor hub such as measured parameters, methodology of measurement, types of sensors, course of test, test stands, and limit loads. The loads during “pull-up from level flight” manoeuvre are limit loads during tests. Required additional processes, like a verification the same parameters by two types of method were shown i.e. deformation of structure were tested by strain gauges and reverse engineering. Strength tests had to be made before flight test, based on results of them aircrafts are flight authorized. In conclusion, the results of tests were presented and fulfilment of legal assumptions and requirements were shown.
Abstract The paper presents a review of the suspension solutions used on the street vehicle up to the now a days, finalising with presentation of their damping characteristics and with evaluation of their advantages or disadvantages. Long time the suspension systems have been dominated by the classic passive suspensions realized with metallic springs, shock absorbers with constant damping coefficients and anti-roll bars, excepting some luxury and sport cars using semi-active and active suspensions. There are presented some semi-active suspension solutions with continuous or discontinuous damping characteristics adjustment and the evolution of the Citroen and other active suspensions. All of them improve in some matter the performances but all of them have not ability to recuperate energy and has auxiliary energy consumption so last period the electromagnetically shock absorbers are researched, the paper presenting some of them. The paper also presents magneto rheological MR damper, solutions for adjustable passive shock absorbers and solutions for passive shock absorbers with variable damping coefficient with the stroke, e.g. Monroe Sensa Trac, Citroën Solution and VZN solution, with their damping characteristics and performances.
Abstract Thin-walled structures are very popular in industries, especially in the field of shipbuilding. There are many types of equipment and structures of ships, which are made up of thin-walled structures such as hull, deck and superstructure. Therefore, the analysis and understanding of the static and dynamic characteristics of a thin-walled structure are very important. In this article, we focus on vibration analysis of a typical thin-walled structure-rectangular plate, a basic structure of the hull. Vibration analysis of a rectangular thin plate is conducted by two methods: numerical modelling method of the finite element on Patran-Nastran software platform and experimental method implemented in the laboratory of Gdynia Maritime University. Thin rectangular plate is fixed one end by four clamping plates and is modelled with finite elements and different meshing densities. The numerical model of thin rectangular plate is divided into four cases. Case 1, thin rectangular plate, and clamping plates are modelled with two-dimensional elements. Case 2, the rectangular thin plate is modelled with two-dimensional elements; the clamping plates are modelled with three-dimensional elements. Case 3, both the rectangular thin plate and clamping plates are modelled with three-dimensional elements. Case 4, the rectangular thin plate, and clamping plates are modelled with three-dimensional elements with larger mesh density to increase the accuracy of the calculation results. After that, the results of vibration analysis according to the numerical modelling method on Patran-Nastran software platform for these cases were compared with the measurement results. From there, assess the accuracy of analysis results of selected numerical model methods and the ability to widely apply this numerical model method to other marine structures.
Abstract In this article, the authors present the equations of the hydrodynamic theory for a slide bearing with parabolic-shaped slide surfaces. The lubricating oil is characterized by non-Newtonian properties, i.e. an oil for which, apart from the classic oil viscosity dependence on pressure and temperature, also an effect of the shear rate is taken into account. The first order constitutive equation was adopted for considerations, where the apparent viscosity was described by the Cross equation. The analytical solution uses stochastic equations of the momentum conservation law, the stream continuity and the energy conservation law. The solution takes into account the expected values of the hydrodynamic pressure EX[p(ϕ,ζ)], of the temperature EX[T(ϕ,y,ζ)], of the velocity value of lubricating oil EX[vi(ϕ,y,ζ)], of the viscosity of lubricating oil EX[ηT(ϕ,y,ζ)] and of the lubrication gap height EX[εT(ϕ,ζ)]. It was assumed, that the oil is incompressible and the changes in its density and thermal conductivity were omitted. A flow of lubricating oil was laminar and non-isothermal. The research concerned the parabolic slide bearing of finite length, with a smooth sleeve surface, with a full wrap angle. The aim of this work is to derive the stochastic equations, that allow to determine the temperature distribution, hydrodynamic pressure distribution, velocity vector components, load carrying capacity, friction force and friction coefficient, in the parabolic sliding bearing, lubricated with non-Newton (Cross) oil, including the stochastic changes in the lubrication gap height. The paper presents the results of analytical and numerical calculation of flow and operating parameters in parabolic sliding bearings, taking into account the stochastic height of the lubrication gap. Numerical calculations were performed using the method of successive approximations and finite differences, with own calculation procedures and the Mathcad 15 software.
Abstract The article presents the analysis of anomaly of rotor dynamics in ultra-light helicopter - Robinson R22. Robinson R22 is two-seat, two-blade main rotor and single-engine helicopter, well known as simple and common used aircraft because of low price and high availability. At the same time, large number of accidents and strictly defined rules (recommended piloting technique) and weather condition for safe flight show disadvantages of Robinson R22. The reason for considering this topic is the analysis of different flight properties and helicopter behaviour as well as easy entering into dangerous flight manoeuvre. In the article different flight properties and loss of control during the pull-up, manoeuvre or vertical gusts of wind and mast bumping accidents were analysed. Analysis shows that problem may be caused by construction of three-hinged rotor hub, designed and patented by F. Robinson. Article presents model of rotor hub and review of main rotor and rotor hub construction in light helicopters. Because of number of accidents, caused by the unusual behaviour of Robinson R22, restrictive pilotage rules were introduced: prohibition of flight in certain weather conditions, the necessity of attending additional training conducted by trained instructors. To reduce the probability of an accident a special instruction for specific Robinson R22 properties was created. Moreover, the statistics of accidents resulting from loss of control and review of legal changes caused by Robinson R22 accidents are presented.
Abstract The article discusses the method of modelling of the helicopter main rotor aerodynamic loads during steady state flight and manoeuvres. The ability to determine these loads was created by taking into account the motion of each blade relative to the hinges and was a result of the applied method of aerodynamic loads calculating. The first part of the work discusses the basic relationships that were used to build the mathematical model of helicopter flight. The focus was also on the method of calculating of the aerodynamic forces generated by the rotor blades. The results of simulations dedicated to the “jump to hover” manoeuvre were discussed, showing the possibilities of analysing aerodynamic loads occurring in unsteady flights. The main rotor is considered separately in an “autonomous” way and treated as a source of averaged forces and moments transferred to the hub. The motion of individual blades is neglected, and their aerodynamic characteristics are radically simplified. The motion of individual blades is neglected, and their aerodynamic characteristics are radically simplified. This can lead to significant errors when attempting to model dynamic helicopter manoeuvres. The more complex model of helicopter dynamics is discussed.
Abstract Thanks to their numerous advantages, plastics are becoming more and more widely used in all branches of industry. The quantities of products, their packaging and, consequently, the amount of synthetic polymer waste are steadily increasing, what poses a high risk to the environment due to their long decomposition time. To reduce waste production is practically impossible, therefore it is very important to constantly implement new and improve existing methods of waste treatment. The following article presents one of the alternative methods for synthetic polymer waste treatment, which is low-temperature pyrolysis. Two pyrolysis processes were carried out. During the first experiment a polyethylene plastic material was used, in the second experiment a mixture of typical household recycling waste of codes 1, 2, 4, 5, 6, and 7 were tested. During the thermal processing, the input material undergoes a chemical transformation due to breaking of long hydrocarbon chains. At the same time, high-energy density products, such as petroleum products and gas, are produced. The main advantage of the presented method is that it allows reducing preliminary technological processes to a minimum and it is easily automated, as it reduces the process to one compact installation. The reduction of the amount of stored waste and the recovery of petroleum derivatives, are additional advantages of pyrolysis implementation. That, in consequence allows reducing consumption of fossil fuel resources.
Abstract Regeneration of parts is the most correct form of use of worn out components and contributes, among others, to reduce CO2 emissions. In the case of elements of fuel injector systems, very high precision is required and such regeneration should be carried out using the original parts. It also requires testing on the original testing stands of these manufacturers, which very often characterized by the fact that it is not possible to perform a short test, which means that it is only possible to perform a time-consuming comprehensive test. An unquestionable advantage in some cases would be the possibility of preliminary verification of the correct operation of the regenerated subassembly without the need for a full time-consuming test. In the present situation, only after completing a time-consuming comprehensive test of the diagnosed element of the injection system, it is often necessary to carry out its disassembly, replacement or correction of one of the components and reassembly with the next time-consuming test. In the case of low unemployment in the labour market, this is extremely unfavourable, and it is often not possible to organize work in such a way that the diagnostic test of the subassembly takes place without the participation of an employee. On the basis of the analyses presented in this article, carried out in the research and development department in company whose employee is one of the co-authors, it can be stated that in the current situation on the labour market where skilled workers are required to work and for the development of science is the most purposeful recognition of the possibility of using vibroacoustic signals to shorten time of tests, which with a high probability may end in a negative result. The preliminary analysis carried out, show that limitation of diagnostic time can be over 35%.
Abstract The stochastic processes theory provides concepts, and theorems, which allow to build the probabilistic models concerning accidents. “Counting process” can be applied for modelling the number of road, sea, and railway accidents in the given time intervals. A crucial role in construction of the models plays a Poisson process and its generalizations. The nonhomogeneous Poisson process, and the corresponding nonhomogeneous compound Poisson process are applied for modelling the road accidents number, and number of people injured and killed in Polish roads. To estimate model parameters were used data coming from the annual reports of the Polish police.
Abstract The aim of the article is to look at the possibility of accurately determining the energy efficiency of drive systems thanks to the use of high quality sensors and measuring instruments. The types of measuring instruments used on the test stand are presented. The results of experimentally determined efficiencies and simulationally determined efficiencies of two hydrostatic systems with throttling control were compared, which are fed with a constant capacity pump. The choice of the analysed systems is not accidental. There is still a view in the literature about limited possibilities of energy systems with proportional control. The research stand was very carefully designed and made. The applied measuring instruments were characterized by high accuracy of measurements. The issues related to the determination of energy losses and energy efficiency of the engine or drive system, which should be determined as dependent on the physical quantities independent of these losses, were also discussed. For laboratory verification, measurement methods were developed, the test stand was adapted and automated. It consists of tested system and loaded system. The measurements during the tests were saved on the computer disk. In order to be able to compare the efficiency of the overall system with the efficiency obtained on the basis of the simulation, coefficients ki determining the energy losses of individual elements of the system were calculated. The research showed a large convergence of the mathematical description of energy losses in the elements of the system and the efficiency of the system with reality. The mathematical model enables accurate simulation determination of the energy efficiency of the system at each point of its field of operation, i.e. at each speed and load of the controlled hydraulic motor. The range of motor speed and load variation can also be accurately determined simulationally.
Abstract One of the most important and commonly used means of transport in the armed forces of various countries is wheeled armoured personnel carriers. After proper preparation, beside transport tasks, they can carry out special tasks, as part of regular and irregular activities within purpose of supporting actions of troops. This paper presents preliminary results of numerical research of wheeled armoured personnel carrier with 8x8-drive system. The effect of impact of large calibre cannon (120 mm) with reduced recoil force on transporter behaviour was investigated. The research object model consists of shell, solid and discrete elements. The research was carried out in the LS-DYNA software. Considered variant applies to sideways firing (to the left of the vehicle) for cannon elevation angle 16 deg. Numerical model of standing still on the flat ground wheeled armoured personnel carrier was preloaded with the gravitational force. The results of post-firing vehicle behaviour including angular displacement of the hull, dynamic deflections of the suspensions and impact on the stability of the wheeled vehicle were evaluated.
Abstract Nowadays acoustic emission (AE) method is used in many fields of science, including in the diagnosis and monitoring of machining processes such as turning, grinding, milling, etc. Monitoring of turning process allows ensuring stable conditions of treatment. Stable conditions of turning process have a great impact on the quality of the surface. This is especially important during finishing treatment. The research was carried out on a universal ZMM-SLIVEN CU500MRD lathe centre-using tool with removable insert SANDVIK Coromant WNMG 080408 – WMX Wiper. Lathing process was performed on the shaft of 74 mm in diameter made of S235 steel. The research was carried out at constant cutting speed v = 230 m/min. Changed parameters were feed f = 0.1; 0.2; 0.4 mm/rev and cutting depth ap = 0.5; 0.75; 1 mm. In the research was used a set of acoustic emission Vallen System. The kit includes: 4 channel signal recorder AMSY 6, two measurement modules ASIP-2/S, preamplifier with a frequency range 20 kHz – 1 MHz and the strengthening of 34dB and AE signal measurement sensor type VS 150M, with a frequency range 100 – 450 kHz. During the study, the acoustic emission (AE) generated during the lathing process were recorded parameters e.g. amplitude, number of events – hits, the effective value of the signal (RMS). The test results indicate, that the higher instability of the process was during turning with parameters: ap = 0.75 mm and f = 0.1 mm/rev. The study can be the basis for the use of acoustic emission method for monitoring lathing process to ensure stable conditions of that process and the same to obtain a high quality surface.
Abstract Cryptography is a field of science necessary to solve problems with encryption of classified messages. The security of electronic information is an integral part of the digital tachography system. From year to year, there is a noticeable increase in electronic data logging systems in many aspects of life. The control measures created for the purpose of performing roadside checks are not sufficient to detect all violations in the recording equipment. Many violations that have occurred during the use of the vehicle are stored in the device’s memory. The article describes the basic mathematical rules illuminating cryptography. The hazards to which the motion sensor installed in the vehicle may be exposed are described. Breaking safety in transport systems may lead to incorrect results of inspections carried out while the vehicle is stopped by authorized services. The article also provides information on the authorities responsible for issuing cards for digital tachographs. Nowadays, documents are increasingly issued with the use of a digital signature. The digital signature of its origin is based on the principles of cryptography. The security key seems to be complicated for the average user. The article discusses the topic of tachograph construction, in particular the schematic responsible for information encryption.
Abstract The main idea of this article was to compare the results of new design electric brake to the older version of hydraulic brake in laboratory tests. The energy of braking should be very similar due to the same mass of the airplane. That is why the laboratory tests of both brakes were took place in the same stand. Of course, the parameters were similar but not at all. The main idea was to create the solution, which could be used in vehicle like airplane. The electric brakes could replace traditional hydraulic brake solution. The results could be interesting for every researcher who is interested in brakes. Other important idea of this article was to describe the tests of new electric brake prototype. The purpose of the tests was to check designing of electric brakes. The electric brake prototype should ensure sufficient efficiency, safety, reliability and durability during braking, which is required in certification processes and is particularly important when researching innovative solutions. It was really important to verify the design and check the parameters. Of course, there is really important to remember that in every new type of the prototype solutions there are many pros and cons, which are typical only for considered design. Nowadays every electric brake design is different because there is a lot of new concept.
Abstract Small advanced turboprop and turboshaft engines, with two-stage high-pressure turbine (HPT), need to meet several challenges. Described herein is an exemplary solution adopted for a cantilevered HPT nozzle mounting and sealing system that helped to meet requirements for size constraint and sealing of split lines and mounting features. Since clearances do not scale down with engine size due to manufacturing tolerances, there is a very limited space available between first and second stage rotors to secure HPT nozzle and to provide means of cooling air supply. Due to small diameters, cavities and size of the parts and assembly access becomes very difficult and precluded the use of typical solutions – like supply air spooilers – known from bigger engines. Relatively larger clearances require also efficient solution for sealing leakage, which was achieved by means of high-temperature braided “rope seals”. The nozzle segments have weight effective hook-type outer band mounting to HPT outer casing and are axially retained by HPT shroud with a snap ring. The hook cavities were used as pockets for rope seals that are subsequently compressed during assembly making it more difficult. However, by special design of the pockets and parts engagement sequence, the assembly process was optimized even though it is so called blind assembly. The sealing system function is not only reducing leakages that are detrimental to a turbine efficiency, but also allow for pressurizing the cavity between the nozzle outer band and HPT outer casing with cooling air thus preventing from hot gas ingestion by higher back-flow margin (BFM) resulting in higher durability of the turbine.
Abstract Steel castings are often used in the construction of valve chambers of steam turbines. Stringent requirements are set due to the continuous operation of the material at elevated temperatures, in the order of 300°C to 600°C. The material of the valve chamber must be resistant to fatigue-creep changes as well as corrosion. This material must be also resistant to dynamic damage which occures when the turbine is starting and stopping. Dynamic damage is induced by a short-lasting but intense accumulation of localized stresses. The castings of the valve chambers of the steam turbine are usually made from the “three-component” type CrMoV-cast steel. Mentioned castings of the valve chamber are continuously subjected to high temperatures, either constant and periodically variable stresses. Due to this, the degradation process of material of the castings is taking place. It is caused by physicochemical processes such as: creep, relaxation, thermal fatigue, corrosion, erosion and changes in material properties, e.g. displacement of the critical point of brittleness. Finally, first cracks and deformations can be observed in the material during the operation. The art presents the process of revitalization technology of the steam turbine valve chamber which was subjected to long-term operation at high temperatures. The revitalization process is aimed at improving the plastic properties of the material and, as the result, extending its service life. The research presented in the article show that impact strength of the chamber material after revitalization is very high. Also the strength properties of the valve chamber, after revitalization, are high and in line with the requirements. The study show that the revitalization of the valve chamber was carried out correctly and restored the material to plastic deformation.
Abstract During preliminary tests of locomotive windshield resistance to gravelling, according to the applicable standard PN-EN 15152:2007, carried out in the Institute of Aviation, the problem of the projectile overturning after leaving the cannon barrel was detected. Three tests recorded with a high-speed camera are presented in this article. This problem was found to be due to the incorrect projectile geometry. In order to stabilise the trajectory of the projectile, four types of projectiles were made using military experience. All of them meet relevant test conditions from the point of view of the test piece (locomotive windshield). The best projectile modification was obtained in the tests with an average deviation of the expected impact angle of 11° compared to 75° for a projectile made exactly according to the guidelines of the standard. Each of 22 modified projectiles hit the test piece with the tip, while out of the 12 original projectiles only 4 hit the test piece with the tip. The impact test results confirm that it is possible to perform a gravelling test according to the standard concept, but it seems necessary to clarify the standard requirements and to modify the projectile shape. The article contains a proposal for the projectile modification and highlights inaccuracies in the standard concerning the gravelling test.
