Calculation of the coefficient of local hydraulic diaphragm resistance in transitional and laminar areas of flow

The local hydraulic resistances in the case of hydraulic machines and devices, as a rule, constitute the determining part of the total head losses during the operation of any hydraulic machine. The most detailed reference book, which has gone through many editions in our country and published abroad, is the “Reference book on hydraulic resistance” by I.E. Idelchik. At the same time, the analysis carried out in the cited literature showed that, depending on the year of publication of the I.E. Idelchik reference book, for the same local resistance, the difference in the numerical values of the same local hydraulic resistance can reach a multiplicity. The purpose of this work is to analyze the recommendations given in the reference book for calculating the hydraulic resistance coefficient of diaphragms (holes) with any edge shapes for various flow conditions in the transitional and lami-nar regions inside a pipeline of constant cross-section. In particular, it is shown that tabular values are recommended for calculating the filling factor of the diaphragm section. There is given an ana-lytical dependence of the differences in the numerical values that reaches 15%, which introduces uncertainty in the results of specific calculations. To a much greater extent, a similar situation takes place when using the recommendations for calculating the coefficient of hydraulic resistance. In this case, the given numerical tabular values of the coefficients of hydraulic friction resistance when the flow passes through the hole and calculated from the given analytical dependence, differ in multi-plicity, which indicates the absence of a connection between them. This issue requires further special consideration.

Numerical simulation of dynamic processes in transmission of vehicle

The article considers the issues of digital modeling of dynamic processes in the transmissions of vehicles. The purpose of this research was to develop an algorithm for numerical mathematical modeling of dynamic processes in the transmissions of transport vehicles using modern digital software packages. The method includes a systematic approach to the study of dynamic processes during switching, based on modeling the operation of the gearbox together with the internal com-bustion engine (taking into account its dynamic, speed and load characteristics). The order of appli-cation of the MATLab – Simulink, Simscape software for numerical simulation of dynamic pro-cesses is considered. Using the fundamental blocks of these applications, models of physical com-ponents are created: the internal combustion engine, friction clutches, gearboxes, elastic shafts, damping devices, and tractor power transmission control systems. A digital model of the tractor transmission is created, its design scheme is given, and the initial characteristics are set. It was used to simulate dynamic processes in the tractor gearbox. The main attention in this paper is paid to the application of the proposed method for calculating the dynamic processes in the gearbox during gear changes under load with forward and reverse switching, including the simultaneous use of several friction clutches.

Numerical study of the effect of droplet coagulation intensity on polydisperse aerosol fraction distribution

The paper is devoted to the study of the effect of the intensity of aerosol fluctuations on the dis-tribution of fractions of the dispersed component of the coagulating aerosol. Oscillations of aerosol in closed channel are numerically modeled in operation. To describe the dynamics of the carrier medium, a two-dimensional non-stationary system of Navier-Stokes equations for compressed gas is used. They are written taking into account interfacial power interaction and interfacial heat ex-change. To describe the dynamics of the dispersed phase, a system of equations is solved for each of its fractions. It includes an equation of continuity for the “average density” of the fraction, equa-tions of preservation of spatial components of the pulse and an equation of preservation of thermal energy of the fraction of the dispersed phase of the gas suspension. Phase-to-phase power interac-tion included Archimedes force, attached mass force, and aerodynamic drag force. Heat exchange between the carrier medium-gas and each of the fractions of the dispersed phase was also taken into account. The mathematical model of dynamics of polydisperse aerosol was supplemented by the mathematical model of collision coagulation of aerosol. For the velocity components of the mixture, uniform Dirichlet boundary conditions were set. For the remaining functions of the dynamics of the multiphase mixture, uniform Neumann boundary conditions were set. The equations were solved by the explicit McCormack method with a nonlinear correction scheme that allows to obtain a mono-tone solution. As a result of numerical calculations, it was determined that in the vicinity of the os-cillating piston, an area with an increased content of coarse particles is formed. The coagulation process results in a monotonous increase in volume content of the coarse particle fraction and a mo-notonous decrease in volume content of fine particles. Increasing the intensity of gas fluctuations leads to intensification of the process of coagulation of aerosol droplets.

Simulation of the insulation monitoring system of the high-voltage electrical network of a vehicle with a hybrid power plant

The paper presents the results of mathematical and simulation modeling, as well as calculated and experimental dependencies, which make it possible to evaluate the operation of the insulation resistance monitoring system of the high-voltage power grid of a hybrid vehicle. The work also provides circuits for measuring insulation resistance, a mathematical model in the MATLAB Sim-ulink environment, and the peculiarities of the operation of the software and hardware simulation complex. The aim of the work is to obtain the most reliable mathematical and physical model of insulation resistance, to determine the architecture of a high voltage battery with the IRM system included in it, to identify the key functions and characteristics of the IRM system, to test the simulation system. The introduction justifies the importance of the IRM system and provides references to standards that govern the requirements for measuring and identifying utility faults. The block diagram of the high voltage battery control system is presented. The composition of its main elements is described. The functions and key characteristics of the IRM system are considered, typical characteristics of insulation monitoring systems are given. A schematic diagram of determining the insulation resistance of conductors and an electric circuit is clearly considered. An equivalent circuit of a differential DC amplifier with a unipolar power supply is presented, which is used to amplify small differential voltages on a shunt when changing large common-mode voltages, which is part of the measuring circuit. Mathematical and simulation modeling was carried out to evaluate the method for calculating the insulation resistance according to the well-known scheme, which is used when measuring using the three-voltmeter method. There was considered the mode of checking the the insulation control system, when several test procedures performed containing simulation of the fault and operating condition of the insulation by connecting and measuring the test resistance. The results of physical simulation of the IRM system and measurement of insulation resistance, voltage between each of the high voltage supply wires and the high voltage battery case, voltage between the wires, battery voltage were obtained. The actual insulation resistance was calculated. The conclusions explain the effectiveness of physical and simulation modeling, obtaining a reliable mathematical model and low error in modeling the insulation characteristics.

A virtual test bench for determining the loads in the air suspension of the rear trolley of a truck at the early stages of design

To determine the maximum loads acting in the rear air suspension of a truck at the early stages of design there was used computer modeling based on solving equations of dynamics of solids and implemented in the Recurdyn software. The components of the developed virtual test bench, includ-ing hinges, power connections, drive axles, a wheel-hub assembly with a wheel and a support plat-form, are considered in detail. The test bench is controlled using a mathematical model created in the environment for calculating the dynamics of rigid bodies and associated with a solid suspension model by standard software tools of the application. The test bench is controlled using a mathemati-cal model created in the environment for calculating the dynamics of rigid bodies and associated with a solid suspension model by standard software tools of the application. The use of such a test bench makes it possible to determine the loads in the hinges and power connections of the suspen-sion, to determine the mutual positions of the links for each load mode, to increase the accuracy of the calculation of loads in comparison with the flat kinematic and force calculation. The mathemati-cal model of the virtual test bench allows to carry out numerous parametric studies of the suspension without the involvement of expensive full-scale prototypes. This makes it possible at the early stages of design to determine all hazardous modes, select rational parameters of the elements, and reduce design costs. The paper shows the results of modeling the operation of a virtual test bench with an air suspen-sion in the most typical loading modes, identifying the most dangerous modes. The efficiency and adequacy of the mathematical model of the suspension was proved. Examples of determining the force in all the joints of the structure, the choice of maximum loads for design calculations when designing the air suspension of vehicle were shown.

Research on molecular energy storage

This article provides a comparative analysis of various energy storage devices. A detailed review and analysis of molecular energy storage units is carried out, their main characteristics and parame-ters, as well as their application areas, are determined. The main types of molecular energy storage are determined: electric double layer capacitors, pseudo capacitors, hybrid capacitors. Comparison of the characteristics of various batteries is given. The parameters of various energy storage devices are presented. The analysis of molecular energy storage devices and accumulators is carried out. Ttheir advantages and disadvantages are revealed. It has been shown that molecular energy storage or double layer electrochemical capacitors are ideal energy storage systems due to their high specific energy, fast charging and long life compared to conventional capacitors. The article presents oscillograms of a lithium-ion battery with a voltage of 10.8 V at a pulsed load current of 2A of a laptop with and without a molecular energy storage device, as well as oscil-lograms of a laptop with DVD lithium-ion battery with a voltage of 10.8 V with a parallel shutdown of a molecular energy storage device with a capacity of 7 F and without it. The comparative analysis shows that when the molecular energy storage unit with a 7 F capacity is switched on and off, transient processes are significantly improved and there are no supply voltage dips. The dependenc-es of the operating time of a 3.6 V 600 mAh lithium-ion battery at a load of 2 A for powering mo-bile cellular devices with and without a molecular energy storage are given. It is shown that when the molecular energy storage device is switched on, the battery operation time increases by almost 20%.

Selection of the characteristics of the suspension system of the high-speed tracked robot

Currently, the field of mechanical engineering is rapidly developing, including the creation of robotic high-speed vehicles. The design of suspension systems for such vehicles must be accompa-nied by the fulfillment of certain requirements, which are currently not formulated. Considering the thing that there is no person in the body of a high-speed robot, the application of the requirements for the suspensions of crew vehicles is not justified. In order to develop recommendations on the choice of characteristics of suspension systems for high-speed tracked robots, the research objects, which mass is in the range from 1000 to 10000 kg are determined. No suspension system is required for objects weighing less than 1000 kg. Objects weighing more than 10,000 kg will be created on the basis of existing serial vehicles. The study is based on the provision that the considered class of vehicles is not subject to re-strictions on the range of natural frequencies of body vibrations. Considering that one of the main requirements remains for high-speed tracked robots - ensuring a high average speed, it is proposed to increase the suspension stiffness in order to exclude resonance from the range of possible travel speeds. Using the accepted provisions, a study of the suspension system of increased stiffness is carried out. The movement along the tracks of a harmonic profile in resonance mode and a broken dirt road is simulated. The results of the study show that the characteristics of the suspension system, selected accord-ing to the proposed method, make it possible to move along the line of the harmonic profile in the resonant mode without suspension breakdowns. The speed of movement on a broken dirt road is limited to a value, which exceeding leads to sig-nificant vibrations of the body and an increase in the load on the elements of the suspension system. The absence of breakdowns leads to a decrease in the loading of the suspension, which makes it possible to reduce the mass of its elements.

Investigation of the components of the cornering resistance of a tracked vehicle on a solid support base

The purpose of the study is to increase the completeness and reliability of approaches to deter-mining the components of the cornering resistance a tracked vehicle, as well as to create a method for their assessment, which will be suitable for practical calculations. The article analyzes two components of the moment of cornering resistance of the tracked vehi-cle, which can be distinguished if we consider the interaction of the caterpillar with the support base through separate contact spots (active sections of the tracks located under the road wheels). The first component arises from the linear movement of the active sections of the tracks. The second is caused by the rotational movement of the contact patch about the vertical axis. The paper presents a mathematical model of the interaction of the propeller and a dense support base, which makes it possible to study the dependence of the components of the moment of corner-ing resistance on the geometric parameters of the undercarriage of a tracked vehicle. The horizontal reaction force in this case is presented as a function of the slip coefficient. The possibility of realiz-ing various adhesion qualities of the propulsion unit in the longitudinal and transverse directions of sliding is provided. The model assumes a preliminary division of the contact patch into a finite number of elementary areas. Since the number of elementary sites affects the result, the article con-ducted a study to determine the minimum number of sites to ensure acceptable accuracy. An analysis of the expressions available in the literature was carried out to determine the speci-fied component of the cornering resistance. The new empirical relationships that better agree with the mathematical model were proposed. The study of several existing tracked vehicles, differing in the mass and size of the track support surface, made it possible to conclude that it is advisable to take into account the moment of cornering resistance of the contact patch for various types of tracked vehicles.

The issue of improving the efficiency of nitrogen oxide neutralization systems in diesel internal combustion engines

The most effective method of reducing nitrogen oxides in diesel exhaust gas is selective purifica-tion by the SCR-NH3 method. The method uses ammonia released during thermolysis and hydroly-sis of a urea solution when it is injected through a nozzle into a neutralizer. This method has a rela-tively low efficiency of cleaning the exhaust gas from nitrogen oxides. The main factor hindering the achievement of high efficiency of the NOx neutralization system is the insufficiently high tem-perature during the implementation of this process. The article analyzes various ways to increase the efficiency of the neutralization process and proposes a new method for neutralizing NOx by using urea injection into the cylinders of the inter-nal combustion engine at the expansion stroke in a diesel internal combustion engine. Efficiency can be achieved due to a higher exhaust gas temperature in the cylinder of the internal combustion engine and an increase in the time of the process of thermolysis and hydrolysis of urea. The kinetics of the decomposition of nitrogen oxides, the process of NH3 oxidation, and the cal-culation of temperature conditions in the cylinder of a diesel internal combustion engine at the ex-haust cycle are considered. The experience of neutralization of NOx contained in the flue gases of thermal power plants, where NOx purification takes place at high temperatures without the use of a catalyst, is analyzed. It is shown that the modernization of the SCR-NH3 process, due to the injection of urea at the exhaust stroke in a diesel internal combustion engine, will simplify the existing method of NOx neutralization and at the same time obtain additional advantages for a modern high-speed engine

Vibration levels on operator’s workplace and vibration protection characteristics of seat suspensions

This article analyzes the nature and parameters of the main operational disturbances, which ener-gy is directly or indirectly transferred to the operator's workplace of tractor with a caterpillar or wheeled propeller when performing various technological operations, based on experimental re-search data. The main operating frequency range of these operational disturbances is considered. The contribution of each frequency component to the overall level of vibration at the operator's workplace is assessed. The example of implementation the results of field measurements of real op-erational disturbances and vibration characteristics on a K-744R1 (st.) wheeled tractor, which oper-ated in a unit with a PG-3-5 plane cutter in the mode of plowing stubble at a constant speed of movement was used. The comparative study of vibration-protective properties of various designs of seat suspension was carried out. The technique of field measurements, including specialized equip-ment of the ZETLAB and Assistant companies, the mode, the sensor installation scheme and other conditions are described. Using the numerical Runge-Kutta method and mathematical modeling tools in the Simulink MatLab software environment, the operation of the serial suspension of the K-744R1 (st.) tractor seat, air suspension of the Sibeco seat with a scissor guiding mechanism and the innovative air suspension of the seat (based on Sibeco) with controlled extraction of vibration ener-gy and its subsequent recuperation was simulated. There were obtained the calculated oscillograms and spectra of vertical accelerations on a seat cushion, sprung with each of the considered suspen-sions under the input action of measured real operational disturbances. The results of the analysis of the research results are summed up.