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Vol 17, No 4 (2023)
- Year: 2023
- Articles: 12
- URL: https://journals.eco-vector.com/2074-0530/issue/view/6144
- DOI: https://doi.org/10.17816/2074-0530-2023.17.4
Heat engines
Exergy analysis of thermodynamic performance of a gas turbine unit
Abstract
BACKGROUND: Gas turbine units are the most widespread type of power plants used in almost all industries. Such a wide distribution in combination with a high level of energy characteristics, high specific power and flexibility determine the relevance of research in the field of assessing their operating parameters.
AIM: Determining the exergy characteristics (exergy efficiency and exergy dissipation factor) of a gas turbine plant and evaluation the efficiency of energy use in a gas turbine plant, as well as analysis of the influence of ambient temperature on the selected parameters.
METHODS: The paper presents the results of an exergy analysis of the gas turbine plant as part of the Jandar Thermal Power Plant, Syria. To evaluate the described parameters, the method of exergy analysis of the thermodynamic characteristics of a gas turbine plant based on the first and second laws of thermodynamics in conjunction with the laws of conservation of mass and energy was used. An important feature of the study, which also emphasizes its novelty, is taking into account the chemical exergy of combustion gases during the exergy analysis.
RESULTS: Based on the results of the study, it was found that the maximum exergy efficiency was 92.8% and was typical for a turbine as part of a gas turbine, while the highest exergy dissipation was observed in the process of fuel combustion in the combustion chamber and was equal to 80% (117.3 MW). The lowest exergy values corresponded to the compressor — 6.0% (9 MW). For the gas turbine unit as a whole, the total exergy dissipation was 147.3 MW and the exergy efficiency was 53.3%. In this case, the main sources of irreversibility in the gas turbine unit are the combustion chamber and combustion gases.
CONCLUSION: Exergy analysis is a convenient method for evaluating the thermodynamic perfection of gas turbine units. As a further line of the study, it is necessary to evaluate the effects of various conditions, such as air humidity or compressor pressure ratio, on the exergy characteristics of the gas turbine fuller.
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Identification of maximal cyclic pressure with the non-motorized method based on specific refraction
Abstract
ВACKGROUND: Russian scientists constantly deal with the issues of the engine performance evaluation with non-standard methods, as they are commonly called “express methods”. In many cases, if the initial components retain the relative constancy of their physicochemical properties, the determination of performance indicators can be carried out with simple classical methods of refractometry, magneto-optics, densimetry, interfacial tensiometry or their combination (aggregation).
AIM: Identification of the maximal cycle pressure of an operating diesel engine with the non-motorized method based on the values of specific refraction for each type of biofuel.
METHODS: The object of research was the D-245.5S2 turbocharged four-stroke engine with intercooler. Mixtures of DT with ethanol, rapeseed oil and surep oil were prepared for the study. The mass fraction of oils and ethanol in the mixture varied from 0% to 50%. Density d and refractive index were measured for each sample. The measurements were carried out at an ambient temperature of 20˚C. The refractive index of the samples was measured using the IRF – 454b refractometer. The density was determined using the PZh-2-25 pycnometer and the VIBRAAJH-620CE laboratory scales according to GOST 3900-85 “Oil and petroleum products. Methods for determining density”.
RESULTS: Data analysis showed that there is a strong correlation between the specific refraction sR and the maximal pressure in a cylinder Pz (MPa). Linear regression models for various alternative fuel mixtures have been developed to determine the maximal cycle pressure during diesel operation.
CONCLUSION: The application of the proposed dependencies makes it possible to identify the maximal cycle pressure of an operating a diesel engine with sufficient accuracy in a non-motorized way.
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Hydraulic and pneumatic systems
Study of dependence of lubrication layer thickness in a plain thrust bearing of a sealed pump with a magnetic clutch on area of the working wheel equalizing holes
Abstract
BACKGROUND: Nowadays, using sealed pumps for transferring various liquids is widespread. Increasing the service life and operation reliability of sealed pumps with a magnetic clutch is a relevant technical task.
AIM: Search for relatively simple ways of increasing the service life and operation reliability of sealed pumps with a magnetic clutch, in particular, study of influence of area of the working wheel equalizing holes on lubrication layer thickness in a thrust bearing.
METHODS: In the mathematical model, the diagram of forces acting at a rotor of a centrifugal pump with hydrostatic bearings operating with the transferred liquid was analyzed and the equilibrium equation was obtained. The influence of such centrifugal pump geometric parameters as area of the working wheel equalizing holes on lubrication layer thickness in a thrust hydrostatic bearing was taken into account in the calculation.
RESULTS: In the paper’s conclusion, there is dependency graph of lubrication layer thickness in a thrust bearing on area of the working wheel equalizing holes. As it is shown in the graph, the axial force is quite sensible to area of an equalizing hole of a centrifugal pump working wheel.
CONCLUSION: The practical value of the study lies in the formulated influence of area of the working wheel equalizing holes on lubrication layer thickness in a thrust bearing of a centrifugal pump, given in the paper’s conclusion.
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Development of an algorithm for controlling the suspension of a heavy-duty vehicle using the technology of systems embedding
Abstract
BACKGROUND: The article is devoted to the development of an algorithm for controlling the suspension of a heavy-duty vehicle. The paper presents a suspension control system for a heavy-duty vehicle. The relevance is linked to the fact that by 2025, industry cooperation between representatives of the high-tech industry and scientists in the field of developing intelligent vehicle control systems is planned within the Autonet ecosystem. The control systems of modernized units with a high degree of electrification and digitalization are of the greatest interest to Russian automakers. This paper describes the results of a study of the active suspension of a heavy-duty vehicle from the side of control theory.
AIM: Development of an algorithm for controlling the suspension of a heavy-duty vehicle. A technical requirement for the monotony of the transition process was formed, since this is the main indicator of improvement of the operational properties of a vehicle, which becomes obvious especially clearly in the smoothness of the suspension.
METHODS: In the study, the fundamentals of the theory of automatic control, the theory of linear algebra, the concept of the state space, as well as methods of systems embedding based on modern achievements of algebra were used. Computer simulation was carried out in the environment of the MATLAB/Scilab/SimInTech kind.
RESULTS: A mathematical and computer model of a half of a four-point suspension of a heavy-duty vehicle has been developed. The paper presents a suspension control system for a heavy-duty vehicle. The control algorithm is developed using the systems nesting technology. The properties of the synthesized control system more than doubled the quality of the system compared to the characteristics of the control object.
CONCLUSION: The practical value lies in the ability of using the results of the study in the production and testing of adaptive suspension of a heavy-duty vehicle.
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Mathematical model of the hovercraft lift system
Abstract
BACKGROUND: Currently, hovercrafts are used worldwide thanks to their amphibian capabilities and mobility at water and slightly prepared areas with low supporting properties. Whereas, in practice, hovercrafts have two main systems ensuring motion, lift and traction which can be combined (operating from a common source of mechanical energy) as well as separated.
This paper considers a hovercraft with separated lift and traction systems. The lift system of this hovercraft consist of piston diesel internal combustion engine (ICE), hydrostatic transmission, axial fans, feeding channel and an air-cushion plenum. The considered variant is chosen because hydrostatic transmission has a number of sufficient advantages in comparison with mechanical transmission with universal shafts and pulley drives, widely used at present time. The paper considers the open plenum lift system.
AIM: Development of the combined mathematical model of the hovercraft lift system consisting of piston diesel ICE, hydrostatic transmission and a fan supplying air into the air-cushion plenum.
METHODS: Using the MATLAB/Simulink environment, the engine power adjustment at hovercraft motion on various ground surfaces is studied with regard to increasing the efficiency of the fan and the whole system. Analytical scheme of the system is given, acceptable transient characteristics are obtained. Efficiency and range of optimal operation of the Sauer-Danfoss pump and hydraulic motor are estimated. The process of hovercraft adjustment from the established mode to a new state when motion condition change is considered.
RESULTS: According to the simulation results, there is influence of the income control signal (adjustment parameter of engine operation modes) and disturbance signal (pressure change coefficient that defines properties of ground surface) on parameters describing the hovercraft motion.
CONCLUSION: The developed mathematical model helps to choose and evaluate adjustment parameters of engine operation modes at hovercraft motion on various ground surfaces, to analyze and to improve the system energy efficiency.
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Influence of the centrifugal pump impeller vanes parameters on its energy performance at operating with high-viscosity liquid
Abstract
BACKGROUND: The currently existing methods for recalculating the operation of centrifugal pumps for viscous fluids cover a sufficiently small range of viscosities. In addition, the considered papers cover the recalculation only, not the search for the optimal geometry of the centrifugal pump for high-viscosity liquids. In this paper, computational fluid dynamics tools were used to test the ability of centrifugal impellers to pump liquids with a viscosity of up to 20,000 sSt, as well as to search for the optimal geometry of the flow path.
AIM: Determination the dependence pattern of the geometric parameters, including vanes, of the optimal geometry of the centrifugal pump flow path at various values of flow rate and viscosity.
METHODS: A numerical modeling method based on the solving of discrete analogs of the basic equations of hydrodynamics is used in this paper.
RESULTS: It was proved that, with the considered viscosities, an impeller with a profiled vane, but with a smaller wrap angle and height, is capable of more efficient operation than a disk impeller. The dependences of the parameters of the optimal flow paths on the characteristics for which their optimization was carried out are given.
CONCLUSION: Based on the study results, it can be stated that it is advisable to use centrifugal impellers in case of high viscosity of the liquid, taking into account the choice of non-classical values of the geometric parameters of the flow path, including the height and angle of its vanes.
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Transport and transport-technological complexes
Load mode control of test rigs for rubber-metal vibration isolators
Abstract
BACKGROUND: Confirmation of the effective performance of vibration isolators of the suspension system for cabins of wheeled and tracked vehicles is obtained on the basis of bench tests. The development of loading devices and load mode control systems for bench testing of vibration isolators based on operating modes is a relevant technical task.
AIM: Development of load mode control systems for bench testing of vibration isolators based on the analysis of their operational loads.
METHODS: Based on the analysis of the operational loads of vibration isolators of suspension systems for cabins of wheeled and tracked vehicles, technical solutions for loading devices of rigs and load mode control systems have been developed that make it possible to reproduce load modes with parameters statistically equivalent to operational load modes on the tested vibration isolators.
RESULTS: The technical solution of the rig for durability testing of rubber-metal vibration isolators with reproduction of operational loads in the vertical, longitudinal and lateral directions on the tested vibration isolator is proposed. A technical solution for the rig ensuring reproduction of load modes at durability testing of vibration isolators, in which the dynamic component of the load contains forced and natural vibrations of the protected object, is also proposed. Load mode control of the proposed rigs ensures more reliable test results due to the approximation of the load conditions of vibration isolators on the rigs to the operational ones.
CONCLUSION: The practical value of the study lies in the opportunity of using the proposed technical solutions of test rigs and load control systems for testing vibration isolators of the suspension system for cabins of wheeled and tracked vehicles with an increase in the degree of reliability of their results due to the approximation of load conditions to the operational ones.
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The method of virtual bench tests conducting to analyze the vehicle technical characteristics compatibility to detect and prevent the risk of resonant phenomena in the sprung cab
Abstract
BACKGROUND: A relevant issue when designing vehicles with multiple levels of suspension systems is collaborative operation of these systems, which ensures the required vehicle dynamics and smoothness parameters, as well as the absence of risk for the occurrence of resonance phenomena. The vehicle cab is a dynamic system with 6 degrees of freedom, so its oscillatory motions have a complex spatial character with the oscillation energies overflow from one direction to another. The solving of problems of the sprung cab dynamics should be conducted in a spatial nonlinear formulation, which makes it possible to take into account the phenomena of redistribution of oscillation energy between the directions of space. This approach can be put into operation with simulation modeling methods through creating a spatial virtual rig of the cab with a suspension system and modeling its dynamics with the application of appropriate external inputs.
AIM: Development of the method of using virtual tests to analyze the compatibility of technical characteristics of the cab suspension system, the frame system and the primary vehicle suspension systems to detect and prevent the risk of resonant phenomena in the cab.
METHODS: Building a virtual test rig of a vehicle cab as a multibody dynamics system of connected bodies in space, mounted at the movable vehicle frame with spring-dampers. Virtual tests are conducted by simulation modeling methods according to the method for analyzing nonlinear phenomena when spatial resonances occur in the secondary suspension system of a vehicle cab.
RESULTS: The method of vehicle cab virtual tests conducting for analyzing oscillatory processes occurring in the cab, including resonances, using a virtual test rig in a multibody dyamics software package.
CONCLUSION: The developed method ensures an ability to take measures to detect and prevent the risk of spatial resonance phenomena in the vehicle cab at all stages of the components design and the cab suspension systems study.
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Assessment of influence of considering the flexibility of the front loader frame on the emerging loads in the multibody system
Abstract
BACKGROUND: Dynamic models are widely used for vehicle dynamics simulation. Increase of simulation accuracy is achieved with adding flexible bodies in a model, making problem solving more complicated. Therefore, assessment of influence of considering the flexibility of the front loader frame on the emerging loads in the multibody system becomes necessary.
AIM: Assessment of considering the flexibility of the front loader frame on the emerging loads in the multibody system becomes necessary.
METHODS: The solution of the problem is presented with the example of a multibody model of a 14.5-ton front loader (FL) with a frame coupled with wheel movers rigidly fixed to the front half-frame and a swinging axle at the rear half-frame. This method of coupling makes it possible to assess the effect of the flexibility of the elements of the FL by comparing the vertical forces that occur in the contact patch of the wheels with the support surface. The multibody models are built in the NX Motion application of the NX 2206 software package.
RESULTS: The comparison of vertical wheel forces in given load conditions (symmetrical and skew-symmetric) using absolutely rigid and flexible models of the frame is carried out. It is found that the forces for skew-symmetric loading modes can differ by up to 20% depending on the frame stiffness.
CONCLUSION: As a result of the conducted research, it can be stated that taking into account the suppleness of the load-bearing system of the vehicle significantly affects the results obtained in the process of modeling.
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Electrotechnical complexes and systems
Diagnostics of inter-turn short circuits in phase stator windings of permanent magnet synchronous machines
Abstract
BACKGROUND: Currently, electric buses are becoming more widespread in the segment of urban passenger transportation due to the absence of harmful emissions and low noise levels. Permanent magnet synchronous machines (PMSM) are widely used as a traction motor.
One of the most promising methods of monitoring the technical condition of traction motors is diagnostics using monitoring tools installed on board of a vehicle. The advantages of such methods include the possibility of regular frequent condition checks (as opposed to much rarer diagnostics in stationary maintenance points) and a more rapid response to the development of identified malfunctions, which significantly reduces the cost of maintenance and repair of expensive equipment. The disadvantages include limitations associated with a shortage of layout space for the placement of diagnostic equipment, with the limited capabilities of on-board computer facilities for the transmission and storage of diagnostic information and with the complexity of computational procedures of built-in expert diagnostic systems.
Concerning the types of operational failures of PMSMs, which are the most common and the most severe in terms of the cost of restoring operability, these are inter-turn short circuits in the stator windings, increased eccentricity of the air gap between the stator and the rotor, bearing damage, as well as damage of the mechanical gearbox coupled with the electric motor.
AIM: Identification the diagnostic signs of inter-turn short circuits in the phase windings of a permanent magnet synchronous machine, helping to detect these malfunctions on board of route urban vehicles at an early stage.
METHODS: A mathematical model of a permanent magnet synchronous machine with short-circuited turns of the phase winding, which makes it possible to study the behavior of the motor with a various number of short-circuited turns, has been developed.
RESULTS: For the first time, the requirements for diagnostic features for the on-board diagnostic system of an urban electric bus, making it possible to detect inter-turn short circuits in the phase windings of traction electric motors at the early stages of the origin of a malfunction, are formulated.
The main parameters of the process of digital registration of phase currents have been obtained, helping to do measurements and to transmit signals through the onboard information network of the electric bus.
Using simulation modeling methods, it was found that the peak values of the linear spectrum of the total current vector are stable diagnostic signs that make it possible to detect inter-turn short circuits in the phase windings of traction motors at the early stages of the origin of the malfunction.
CONCLUSION: The practical value of the study lies in the opportunity of using the proposed methods for diagnosing the technical condition of traction electric drive units in urban passenger electric transport.
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Model-based development of software for network control of automotive vehicles’ equipment
Abstract
BACKGROUND: Various devices and systems connected via onboard network with electronic control unit are the part of automotive vehicles’ equipment. Such devices and systems, which ensure the operability of a vehicle or are the elements of technological units, having microprocessor control, are based on various physical principles. Designers of such devices and systems may not have sufficient knowledge and experience to develop the software independently, which applies to the development of software for the network control.
AIM: The development of software for information subsystem of a technical device that interacts with an electronic control unit via onboard network as part of automotive vehicles’ equipment, as well as the demonstration of application of model-based programming tools in this development.
METHODS: A comprehensive description of technical solutions developed to achieve the listed aims using methods of system analysis and methods for developing and debugging of software is given. According to these methods, model-based programming tools are used as handlers for built-in interface modules of microcontroller and elements of software layout. Software elements for processing received messages, performing actions with the data received in them, as well as generation of response messages have been developed in the C language.
RESULTS: Software that processes messages received by a device subordinated to an electronic control unit via the CAN network, generates response messages addressed to this unit, and sends them has been developed. The method of access to the receiving buffer of the network interface and priority of software execution are taken into account.
CONCLUSION: It is shown that model-based programming in combination with programming tools based on structured text is an effective software development technology that is convenient for designers of technical devices and systems based on various physical principles and requiring microprocessor control. In particular, the abovementioned should be attributed to specialists in the field of electrical engineering who develop equipment for automotive vehicles.
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Development and research of the model of a wheel-legged robot
Abstract
BACKGROUND: The development of robots capable of moving in both walking and wheeled modes and distinguishing with a simple design from the already developed robots is a relevant task for some recent years. In order for such a robot to have scientific and commercial success, it is necessary for it to be as structurally complex, smooth, reliable and inexpensive as its wheeled equivalent and, in addition, to be able to move stably and quickly over terrain that is impassable for wheeled robots. The robot dynamics is modeled with the Universal Mechanism and the MATLAB/Simulink software packages. The results of virtual tests of the robot in main motion modes (straight-line motion, turning, step climbing) are given in the paper.
AIM: Increasing the mobility of a wheel-legged robot, equipped with the pseudo-walking propulsion system, using reasonable control laws.
METHODS: In order to evaluate ride performance of the studied robot, methods of numerical simulation of its motion based on the multibody dynamics software packages are used.
RESULTS: The maximal velocity of stable straight-line motion, the turning velocity and the height of the largest climbed step were obtained for the robot with given power of engines.
CONCLUSION: The model of the new mobile robot equipped with the simple-designed propulsion system has been developed. This model demonstrated high cross-country abilities and other mobility indicators according to the results of virtual tests.
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