EDITORIAL
Mechanical engineering and theory of machines
The main focus in the design of weighing and batching devices is to create a gravimetric technique, capable of providing not only mass measurement – weighing with the required accuracy and speed, but also automatic control of technological processes and their control and regulation. In this case, the opportunity of two-way communication with a computer when designing the load measuring devices is realized, allowing remote monitoring and solution of logical problems associated with the management process. Modern automatic weighing and batching devices are important parts of comprehensive automation in different branches of industry. Existing developments of electrical, electronic, computing and other branches of instrument engineering techniques allow to implement transformations of the measured quantity with a very high degree of accuracy. However, if the measured quantity in the weighing process is perceived by the elastic sensing element of low quality, then no matter how high the accuracy of further changes is; the characteristics of the elastic element will limit the accuracy of the instrument as a whole. Although the elastic elements are simple mechanical parts, and many types of elastic elements are known and are widely used for many decades, their performance often does not meet the requirements, and hampers the device creation of high accuracy classes. Growing requirements for primary transformer makes actual the problem solution of improving the quality of elastic sensing elements not only in the manufacture but in the design. This led to the appearance of projects aimed at the development of computational and experimental methods that have altered the methodology for the design of force measuring devices.
Aviation, rocket and space technology
The aerodynamic characteristics of the detachable elements of transport systems are introduced, they allow to calculate the trajectories of these elements after their separation and determine the size of elements impact areas. Special consideration is given to head fairing shells, containing cylindrical, conical and spherical sections. Head fairing shells have high lift-to-drag ratio and the widest impact areas. Aerodynamics of bodies of such configurations has been insufficiently studied. The paper presents the numerical results of modeling the flow around a typical head fairing shell in free flight. Open source OpenFOAM package is used for numerical simulation. The aerodynamic characteristics at trans- and supersonic velocities are obtained, flow pattern transformation with the change of the angle of attack and Mach number is analyzed. The possibility of OpenFOAM package for aerodynamic calculations of thin shells is shown. The analysis of the obtained results demonstrate that there are many complex shock waves interacting with each other at flow supersonic speeds, at subsonic speeds vast regions of flow separations are observed. The authors identify intervals of angles of attack, where different types of flow structures are realized, both for trans- and supersonic flow speeds. The flow pattern change affects the aerodynamic characteristics, the aerodynamic coefficients significantly change with increase of the angle of attack. There are two trim angles of attack at all examined flow velocities. The results obtained can be used to develop a passive stabilization system for fairing shell that will balance the body at the angle of attack with minimum lift-to-drag ratio and will reduce random deviations.
The main technical and economic characteristics of the future aircraft are introduced at the early stages of the design process. The high responsibility of these stages is explained by the necessity to make more than 70% of the conceptual decisions on the project, and the mistakes made at this moment, as well as various inaccuracies can entail great economic costs when they are revealed and corrected at later stages of the project development. To reduce the design risks of obtaining an uncompetitive aircraft, there is a need to increase the efficiency of the preliminary design stage targeted to increasing the accuracy and reliability of the results obtained. Special attention should be paid to methods for determining the aerodynamic properties of an aircraft.
An evaluation technique for the aerodynamic properties of aircraft with high-aspect-ratio wing was considered, taking the static aeroelasticity into account. The technique is intended for the initial stages of design. The calculation of elastic deformations of the wing for the analysis of the aerodynamic properties of aircraft is provided in order to improve the accuracy of the results and, as a consequence, the accuracy of the choice of the aircraft shape. The application of the technique may allow to increase the efficiency of the preliminary design stage of aircraft. The technique is based on numerical multidisciplinary mathematical modeling using the discrete vortex method and the topology optimization algorithm based on the variable density body model. The main feature of the technique is the use of the algorithm of topology optimization, which makes it possible to determine the elastic-strength characteristics of the full-tension wing design under the conditions of the initial stages of design, when the power circuit is still unknown. Using the example of the demonstration task solution of the aerodynamic properties estimation for an unmanned aircraft with a high-aspect-ratio wing, the importance of taking into account the elastic deformations of the wing design at the initial design stages is shown. The integral and distributed aerodynamic characteristics of the wing of the aircraft are evaluated and compared with and without deformations.
The construction of several large wind farms (The Ulyanovsk region, the Republic of Adygea, the Kaliningrad region, the North of the Russian Federation) is planned on the territory of the Russian Federation in 2018–2020. The tasks, connected with the design of new wind farms, are currently important. One of the possible direction in the design is connected with mathematical modeling. Large eddy method (eddy-resolving simulation), developed within the Computational Fluid Dynamics, allows to reproduce unsteady structure of the flow in details and define various integrated characteristics for wind turbines. The mathematical model included the main equations of continuity and momentum equations for incompressible viscous flow. The large-scale vortex structures were calculated by means of integration the filtered equations. The calculation was carried out using lagrangian dynamic Smagorinsky’s model to define turbulent subgrid viscosity. The parallelepiped-shaped numerical domain and 3 different unstructured meshes (with 2,4,8 million cells) were used for numerical simulation.
The geometrical parameters of wind turbine were set proceeding to open sources for BlindTest 2–4 project from Internet. All physical values were defined at the center of computational cell. The approximation of items in the equations was performed with the second order of accuracy for time and space. The equations for coupling of velocity, pressure were solved by means of iterative algorithm PIMPLE. The total quantity of the calculated physical values at each time step was equal 18. So, the resources of a high performance computer were required. As a result of flow simulation in the wake for two three-bladed wind turbines the average and instantaneous values of velocity, pressure, subgrid kinetic energy, turbulent viscosity, components of stress tensor were calculated. The received results qualitatively matching the known results of experiment and numerical simulation testify to an opportunity to adequately calculate flow parameters for several wind turbines.
The introduction of unmanned aerial vehicles is one of the most dynamic areas of civil aviation development over the last years. The main field of their application is the performance of different aerial works. The most part of the aerial works is characterized by a small distance of flying unmanned vehicles from humans, animals, plants and infrastructure. Thus the influence of inductive velocities of these vehicles on the objects and some processes of aerial works is the topical issue. The article considers the problems of evaluation of vortex trace formation and description of inductive velocities field within the flying area of light unmanned multicopters which are the most popular and promising for the performance of the basic aerial works. The studies have been conducted by a numerical experiment using the software package developed in Delphi. On the bases of the defined multicopter parameters, conditions and flight modes created package provides simulation of the vortex trace formation of multicopter as a set of the mutually influencing П-shaped vortices of the multicopter rotors, graphic visualization of the vortex trace and calculations according to the inductive velocities in the flight area with the construction of the vector diagrams as well as some related problems. The article presents the graphic data on the spatial configuration of vortex trace and distribution of inductive velocities in the transverse planes which are unequally distant from the multicopter; for example, light hexacopter "Odonata agro", for which the proximity of experimental and calculation data of drops sedimentation at aerial spraying, received with the use of the package, confirms indirectly the package adequacy as well as configurations of vortex trace which are comparable in flight weight and load upon rotors of quadcopters and octocopters. According to the calculated data the general regularities and features of the vortex trace formation and configuration, distributions of the inductive velocities within the flying area of the light multicopters are formulated in this paper. The results can be used at the evaluation of the parameters and the vortex trace influence of light unmanned aerial vehicles on the surrounding objects and optimization of rational structural designs and multiсopter flight modes while performing aerial works.
Supersonic flow around the system of bodies (lattice wings, a wing near the shielding surface, blades of supersonic stages of the compressor, etc.) is accompanied by complex pictures of shock waves, which depend on several parameters characterizing the mutual arrangement, the bodies of their external shapes and sizes, as well as the Mach number. These patterns are determined by the nature of the interaction of the head shock wave and the shock wave on the lower surface of the profile, caused by a change in the flow direction as a result of deflection of the flap.
The paper presents the results of an investigation of supersonic flow around a profile with a flap near the screen, obtained using the method of hydraulic analog simulation (the method of gas-hydraulic analogy). This method is based on the analogy of the equations of motion describing a planar gas flow and a thin liquid layer and is used in solving a large class of plane problems of stationary and nonstationary gas dynamics.
The parameters that affect the structure of the flow around the profile near the screen are: the Mach number of the profile movement with the values M∞ = 1.4 ÷ 1.9; relative distance of the profile from the screen with the values Нз = 0.2 ÷ 1.0; angle of flap deflection with values δз = 0 ÷ 40°. In the course of the experimental investigation, the changes in the structure of shock waves were determined and the influence of the above-mentioned parameters on the process was revealed. The results of the experimental study are presented in the form of graphical dependencies of the relative position of the shock wave on the lower surface of the profile for different Mach numbers, the relative position of the profile from the screen, and the angle of deflection of the flap Δ = f (М∞,Нз , δз). On the basis of the analysis of the obtained dependences, a generalized parameter is derived, which makes it possible to determine the boundaries of changes in the structure of shock waves in a given type of problem.
A choice of material and external geometry for gas rudder of the declination system of unmanned aerial vehicle are considered. When selecting material the main criterion is the quantity of the ablative material from the gas rudder surface in a unit of time. That is, the material should be chosen in such a way that when exposed to a gas jet the gas rudder is not burnt immediately, and ensures its efficiency during the entire time allotted to its work. The main material loss occurs at the leading edge of the gas rudder. The thermoerosion-resistant material (graphite, molybdenum, etc.) is chosen to reduce this harmful effect.
Characteristics of the gas flow around the rudder affect the selection of geometric parameters of the gas rudder. Obtaining the reliable results is hampered by uneven gas flow from the nozzle, the presence of unburned particles of the fuel, a blunt profile of the rudder; influence of its side edges on the flow around and interference with the nozzle walls. The configuration of the rudder shall be chosen to provide the desired value of the force at the completion of the work of the rudder with the expected burnout of its leading edge. The final decision on the choice of parameters of the gas rudder is based on the analysis of a large number of model and full-scale tests of the rudders-analogues.
The technique of the structural material choice and the external geometry of the gas rudder of the unmanned aerial vehicle declination system is proposed. The technique is based on the relations obtained on the basis of experimental data processing of gas jets impact on the rudders, made of different structural materials. An example of solving the problem of structural material and the external geometry choice of the gas rudder is given.
The essence of an expert assessment as a scientific method is a rational organization of experts analyzing the problem from a quantitative evaluation of judgments and results processing. A generalized opinion of the expert group is taken as the solution. The diversity of the problems solved by the experts is reduced to two types: a system analysis and a parametric analysis of the design proposal. The system analysis aims to confirm the feasibility (or non-expediency) of creating a new equipment model, to estimate its technical level and economic efficiency, taking into account requirements and possibilities of an upgraded technical system. The parametric analysis of the project proposal is to justify the validity of design parameters and characteristics of the considered technical system, their marketability, the importance of targets. Despite the relatively well-established and proven tools expertise methods, the expert assessment of complex technical systems project proposals still remains a challenge. The main difficulty is the decomposition of tasks, the definition of a hierarchical system of criteria (grounds on which project proposals are compared).
The technique and software for the expert assessment of project proposals for the sake of assessing the quality and competitiveness of aviation and rocketry products are suggested in the article. The technique of expert assessment involves the comparative analysis of project proposals in accordance with the formed system of criteria of products quality. The method of analysis of hierarchies, which is currently one of the most powerful and effective methods of the expert assessment and the decision-making, is used. Thanks to the hierarchical representation of the expert assessment task and the relatively simple procedure for the pairwise estimation of project proposals at each stage of the expert procedure, there is a possibility operatively to carry out the comparative assessment of a large number of alternative design proposals, using arbitrarily complex system of criteria.
An example of using the developed technique and software for the expert assessment of project proposals of aviation and rocketry products in the solution of the problem of choosing the rational option of constructive and technological patterns of a wing is given.
The process of designing aviation electrical power systems (EPS) is related to the need to fulfill a number of requirements of normative and technical documents and to conduct a large number of calculations. Experience has shown that it is not possible to obtain reliable initial data on the nature and magnitude of electricity consumption by electricity receivers (end users) at the early stages of design. The composition of the electric power receivers and the power consumption of electricity during the design process are repeatedly changed. This leads to the need to repeatedly perform tasks related to the synthesis of primary and secondary systems of generation and calculation.
The desire to improve the efficiency of EPS led to the emergence of new standardized types of electrical energy - 270 V DC and 380 V three-phase AC of stable and unstable frequency. It follows that it is possible to implement a rather large number of options for EPS structures, and there may be several secondary EPS or, in general, EPS of a third or higher level.
The lack of ready-made aviation energy converters implies the impossibility of using ready-made components, and the development of specific devices should be coordinated with the development of EPS. In this case, one of the results of EPS design will be a set of requirements for the devices and units of the EPS projected.
In any case, the design process for EPS aircraft requires a lot of iterations that take into account the change in both the raw data and the constraints on the EPS elements and the design process itself.
The traditional approach to the design of EPS aircraft, assuming the knowledge of the designer of dozens of GOSTs (State All-Union standards) and OSTs (All-Union standarts) regulating the design stages of EPS, as well as the existence of standard EPS structures, from which a specific choice is made, is practically impossible at present. The only way to consciously approach the problem of designing EPS aircraft and take into account all the requirements of the customer and the regulatory and technical documentation is its automation.
Automation of the design of EPS aircraft as an optimization task involves the formalization of the object of optimization, as well as the choice of the criterion of efficiency and control actions. Under the object of optimization in this case we mean the design process of the EPS, the formalization of which includes formalization and the design object – the aircraft power supply system.
The article considers the issue of aerodynamics efficiency implementation taking into account certification requirements for flight safety. Aerodynamics efficiency means high aerodynamic performance (depending on the airplane size), aerodynamic performance in cruise flight, high aerodynamic performance at takeoff, as well as lift performance at landing.
The author estimated the impact on aerodynamics efficiency of both the requirements for aerodynamics performance and requirements for aircraft systems, noncompliance with which may result in significant change of expected operating conditions. It was shown that the use of supercritical wing profiles may result in flight mode limitations due to failure of the required buffeting capacities. It does not allow engaging all the advantages of aerodynamics layout and requires special design solutions to prevent such cases.
There were reviewed certification requirements for flight level pressure altitude accuracy and icing conditions warning sysytem. The research presented the methods of aerodynamic efficiency increase by meeting the requirements for reduced vertical separation minima flights and in icing conditions, including requirements for air data probes. Reduced vertical separation minima flight requirements are met by means of efficient air data probes location. Theoretical methods of flow calculation determine areas on the airplane skin surface where static probes minimize errors depending on angle-of-attack and sideslip. It was shown that if certification requirements are not met and in case of flight out of reduced vertical separation minima area, aerodynamics efficiency is significantly reduced and fuel consumption can be increased by 10% and higher. Suggested approaches implementation allows increasing commercial airplanes competitiveness.
This paper describes the effect of different rotor blades on the X-shaped tail rotor of the Mi-171 LL, observed conducting flight tests. The tests were carried out on the same helicopter in the similar atmospheric conditions.
The objective of the tests was the comparison of flight performance of two sets of rotor blades of the helicopter Mi-171 LL. However, materials test revealed a difference in the angles of the tail rotor at different MRs with the same takeoff weight.
The authors are grateful to I.G. Peskov, S.R. Zamula and A.I. Orlov for assistance in carrying out this work and the preparation of this article.
Noted that the helicopter takeoff weight when hovering out of ground effect in ISA with blades from polymer composite materials (PCM) exceeds the takeoff weight of the helicopter with the serial blades in the nominal mode of the engine operation at ~ 750kg, in the takeoff mode at ~ 700kg.
Knowing the altitude and climatic characteristics of the engine, the obtained dependence allows to determine the balancing value of jрв on hovering at different combinations of pressure altitude and outside air temperature for a given speed of the main rotor (MR).
It follows from the work that when the same value Nпр(95/nнвпр)3 or Nfact the balancing values of jрв for the helicopter with the main rotor blades from the PCM is less than for the helicopters with serial blades by 0.5…0.9°. The difference in the angles of the tail rotor increases with growing of Nепр(95/nнвпр)3 (Nfact). Perhaps this is caused by different induction effect of the main rotor on the tail rotor to the MR from PCM and the serial ones.
As follows from the materials, the thrust of the main rotor with blades from PCM with the same engine power is more in comparison with the serial blades. Consequently inductive speeds of the main rotor are more and the angles of the tail rotor are less. It can be assumed that a large induced velocity of the main rotor increases the thrust of X-shaped tail rotor.
Transport
Vibration monitoring of machines is an integral part of their technical health estimation while in service and prevention of collapse resulting from resonance conditions operation or material fatigue.
Aviation gas-turbine engines and land based gas turbine – typical representatives of the of machines which are subject obligatory vibro-monitoring. In most cases it should be carried out continuously, but, in some cases (for example, power-plants of light helicopters), vibro-monitoring is performed within periods reckoned in dozens of hours. Now one-axial vibration transmitters of various types are thus used. Anyway, the data received as a result of vibro-monitoring are processed, first of all, with the use of range verification and a number of smoothing modes and the estimation of a tendency of vibration change modes while in service, examples of which shown on the engines are displayed in a paper. In some cases, there is a necessity of the simplified estimation of a vibrational condition of the machine for additional points or holding operative primary vibro-monitoring without engaging of a rented control equipment. The possible solution is the use of the modern mobile devices equipped with acceleration transmitters and the specialized software for archiving and vibro-monitoring data presentation in real-time mode. In the training process these devices appear full-scale substitution of vibration pickups and an oscillograph sheaf at estimating critical frequencies of rotors rotation with the possibility of archiving of the monitored data for the further processing.
The vibrational monitoring technique with the use of microelectromechanical systems of modern mobile devices, has a number of advantages over the other ways. Particularly, the simultaneous three-axial estimation of vibration acceleration and a vibration vector with the graphic and character data presentation in real-time mode and more archiving and operative data processing opportunities, is executed.
Within the problems solution of complex research in helicopter controllability, the reasons of changes controllability parameters when transporting cargo using external load have previously been identified.
The next stage of research is to determine how concrete cargo parameters and external load as a whole, as well as their combination influence helicopter controllability parameters.
The article contains research results of the cargo parameters and external load impact on static and dynamic controllability parameters. As a static characteristic of controllability the operation efficiency expressed by the maximal angular acceleration acquired by the helicopter in the case of throttle equal deviations at various flight velocities was considered. Time of the transient process was chosen as a dynamic characteristic with the observable parameter being the movement of the cyclic pitch. For cargo parameters, 16 combinations of ballistic coefficient and cargo mass were considered, while the external load parameter the cable length from 10 to 40 meters was chosen.
According to completed simulation experiments, certain dependencies were found between controllability parameters and external cargo parameters and their various combinations. The analysis of the results showed that the dynamic characteristics are more appropriate for estimating the impact of cargo parameters on helicopter flying qualities, since such estimation fully defines the workload on a pilot. The acquired results may be applied to improve Flight Operations Manuals and Aviation Personnel Training Instructions.
When helicopters fly with suspended load, there may be a need for a load drop. This can be associated with both the abnormal situations in flight and with a regular load drop to a predetermined area. However, under certain conditions, after the external load drop, there may be significant changes in the parameters of the helicopter movement. In this regard, when planning the helicopter flight with suspended load, it is necessary to make sure of safety in case of a load drop. In carrying out this work, theoretical and experimental research methods have been used. The theoretical methods of research include analytical calculations and computational experiments conducted with the help of special software. Experimental methods include flight test methods. Flight experiments allowed to confirm the adequacy of theoretical methods for researching the helicopter dynamics after external load drop. The proposed methodology for ensuring the safety of helicopter operation involves a staged research of the helicopter dynamics after external load drop. At the first stage, an analytical determination of the normal vertical load factor after the load drop according to the formula derived earlier was carried out. At the second stage of the research, computational experiments were performed using the HeliCargo software package, which allowed not only to clarify the values of normal vertical load factor obtained by the analytical calculations, but also to consider the movements of the helicopter mass center and its angular movements after load drop. The conducted research shows that the helicopter dynamics after load drop can be satisfactorily investigated by the previously developed theoretical methods, which is confirmed by comparing the obtained data with the results of the flight experiments. In addition, this paper presents concrete results, stating the safety of external load drop, which can be used in planning the production of work on the delivery of suspended load to a predetermined area.
The concept of the aviation enterprise as a unified system of processes and projects of the aircraft airworthiness maintenance (AAM) is presented. The relevance of project management tools usage, including the transport branch, is noted; the examples of successful implementation of the development projects at domestic enterprises manufacturing aircraft engines are given. A scheme for the classification of the AAM projects and processes, reflecting their interrelationship, is proposed. The operational activity of the enterprise is a combination of its business processes. The company selects plans and implements the relevant projects for the business processes optimization. At the same time, the projects themselves are the objects of management based on standardized processes. The processes of project management and the main processes of the enterprise are also interrelated and can be objects included in the unified regulations of its units. Increasing the efficiency of operational processes and processes of the aviation enterprise management is the goal of development projects, which are divided into investment projects and organizational changes projects.
Limitation of organizational and financial resources of the company requires the identification and systematization of all projects and processes, while the application of project management standards allows to analyze the opportunities and to determine the sequence of their implementation. The importance of accumulating experience of completed projects is shown; the results can become typical methods for planning, organizing the implementation and monitoring of AAM projects. Specific forms of the project management standards implementation for AN-124-100 constructive modification project in LLC Volga-Dnepr Airlines are demonstrated: the control events plan and the project team formation.
Aircraft gas turbine engines during the operation are exposed to damage of flowing parts. The elements of the engine design, appreciably determining operational characteristics are rotor blades. Character of typical damages for various types of engines depends on appointment and a geographical place of the aircraft operation on which one or another engine is installed. For example, the greatest problem for turboshaft engines operated in the dusty air conditions is erosive wear of a rotor blade airfoil. Among principal causes of flowing parts damages of bypass engine compressors are foreign object damages. Independently there are the damages caused by fatigue of a rotor blade material at dangerous blade mode. Pieces of the ice formed in the input unit, birds and the like can also be a source of danger. The foreign objects getting into the engine from runway are nuts, bolts, pieces of tire protectors, lock-wire, elements from earlier flying off aircraft, etc. The entry of foreign objects into the engine depends on both an operation mode (during the operation on the ground, on takeoff, on landing roll using the reverse and so on), and the aircraft engine position.
Thus the foreign objects entered into the flowing path of bypass engine damage blade cascade of low and high pressure. Foreign objects entered into the flowing part of the engine with rotor blades result in dents on edges and blade shroud, deformations of edges, breakage, camber of peripheral parts and are distributed "nonlinear" on path length (steps). The article presents the results of the statistical analysis of three types engine compressors damageability over the period of more than three years. Damages are divided according to types of engines in whole and to their separate steps, depths and lengths, blades damage location. The results of the analysis make it possible to develop recommendations to carry out the optical-visual control procedures.
Functional properties characterize the purpose of the aircraft and are described by its flight performance characteristics such as range and cruising speed, payload, runway characteristics, etc. Functional properties also characterize the aircraft efficiency that determines the objective need for their analysis by both aircraft designers and operators in conditions of permanent and systematic efficiency increase necessity. When choosing the aircraft, it is important for the operator to make sure that a selected aircraft type has a high level of functional properties, which will allow it to provide high operational efficiency without obsolescence in the long term. However, when choosing from several aircraft types the operator has to face the fact that some characteristics of considered aircraft variants are better and the others are worse that does not allow to definitely determine what aircraft type has a higher level of functional properties.
The possibility of applying technical efficiency indicators and a generalized technical level indicator for analyzing the functional properties of civil aviation aircraft is explored in this article. Fuel, weight and target efficiency values as well as the previously improved technical level indicator value were calculated for the different generations and modifications of Boeing 737 and Airbus A320 families of medium-range airplanes, which was followed by the results interpretation within one airplane generation and when moving historically from one airplane generation to another. According to analysis results it is concluded that it is impossible to define the change of the aircraft functional properties level by the change in the values of separate technical efficiency indicators. Thus, it is proposed to use a generalized technical level indicator that determines the level of aircraft technical perfection for purpose and to use efficiency indicators to analyze the cost of providing this level of properties at aircraft production and operation phases.
ISSN 2542-0119 (Online)
