Vol 11, No 3 (2017)
- Year: 2017
- Articles: 11
- URL: https://journals.rcsi.science/2074-0530/issue/view/3709
Articles
The choice of the concept of automobile with combined energy transmission of expanded functionality
Abstract
The article is devoted to the issues of improving the transmission schemes and the transmission of electric power of combined energy transmissions (CET) of automobiles. Ideology of CET consists in the rational choice of the mode of operation of ICE - the efficient use of the energy it generates, but the presence of the CET on the vehicle can also be used to expand its functionality. The authors develop and justify the idea of expanding the scope of vehicles with combined energy transmission (CET), ensuring their universality and expanding the possible applications and areas of use, due to the specifics of the road and climate conditions in Russia. The authors see the possibility of accomplishing the goal in the application of a combined power transmissions of advanced functional capabilities on vehicles. In the drive of the driving wheels of vehicle equipped with such an installation, there are two reversible electric machines, each of which is individually kinematically connected to one of the wheels of the driving axle. The concept of the vehicle with the CET of extended functionality, on the scheme of which a patent for the invention was issued, the authors suggested in previous publications. The material of this article contains options for the development of design schemes for the execution of combined energy transmissions of enhanced functionality, which can be equipped with cars with different drive variants of the driving wheels. Authors offer schemes of assemblies, composition of units and systems when using vehicles equipped with them, under various road conditions. The algorithms for the operation of CET of extended functionality in various road and climate conditions are described. The variants of constructive execution of the main units and aggregates, which are part of the CET of the expanded functional capabilities, are proposed. In the final part of the article, the positive impact of the recommended options for the performance of the expanded CET on the performance characteristics of vehicles equipped with such facilities is noted.
Izvestiya MGTU MAMI. 2017;11(3):2-8
2-8
Design of an independent vehicle suspension guide using the topological optimization method
Abstract
Reducing the mass of automobile aggregates is an urgent task: fuel consumption and emissions to the atmosphere are reduced, material intensity, energy intensity, production costs are reduced, the ratio of the mass of the cargo to the curb weight of the vehicle is increased, etc. The solution of such a problem by the method of topological optimization makes it possible to obtain strong and rigid constructions of minimum mass. The article considers an example of reducing the mass of the chassis of vehicle by synthesizing the power scheme of double wishbones of an independent suspension of an all-wheel drive 4x4 automobile by topological optimization. The peculiarity of the design scheme is the use of a complex finite-element suspension model that allows the synthesis of the power circuit of the upper and lower arms simultaneously and the loading of the suspension is carried out as part of a common beam-rod independent suspension model and with a wheel. The power circuit of the upper arm obtained as a result of solving the optimization problem is a flat construction in the form of the letter A, which is explained by: 1) the absence of forces acting outside the plane of the upper arm of the suspension; 2) a small distance between the hinges of attaching the arm to the body. The power circuit of the lower arm of the suspension also has the shape of an isosceles triangle in plan, however one branch of the triangle has a large construction height in a direction perpendicular to the plane of the arm, which is explained by the high force created by the elastic suspension element resting in this zone on the lower arm. In the absence of forces emerging from the plane of the suspension arm, the task of synthesizing the power circuit is reduced to a flat problem and provides uniquely interpreted power circuits that are easy to implement in the construction of arms. When forces acting perpendicular to the plane of the arm, for example, in the zone of support of the spring-damping suspension element, are applied, it is necessary to increase the construction height of the arm in the zone of action of this force. The overall assessment of the weight of the resulting lever structures in comparison with existing analogs shows a reduction in the weight of the arms by up to 30%.
Izvestiya MGTU MAMI. 2017;11(3):9-13
9-13
Optimization and debugging of a low-toxic combustion chamber with the use of numerical modeling of intrachamber processes
Abstract
In recent years, there has been a trend towards an increase in demand for microturbines. The microturbine application area is very wide. These are hybrid power plants for transport and specialized equipment, as well as power plants for providing electricity to homes, towns, businesses. When developing advanced gas turbine units, it is necessary to take into account sufficiently high requirements for economic and operational indicators. To improve the performance of microturbines, it is necessary to optimize and refine the basic elements. In particular, to reduce the emission of harmful substances, it is necessary to develop low-toxic combustion chambers. In this paper, we present the results of optimization and fine-tuning of a low-toxic combustion chamber with the use of numerical modeling of intra-chamber processes. The applied models of flow, combustion, radiation, NOx emission are described. The main parameters of the computational grid built for ¼ of the full-size combustion chamber are given. The boundary conditions necessary for the development of mathematical modeling of the flow and combustion processes are formulated. The results of comparison of the initial and optimized geometry of the combustion chamber in the form of patterns of temperature distribution, velocities, total pressure in the swirler, and the distribution of the mass fraction of nitrogen oxides NOx are presented. According to the results of optimization calculations, it can be concluded that relatively small changes in the size, shape and number of secondary air holes, the shape and dimensions of the flame tube, the diameter of the blade swirler and the shape and size of the nozzles of the gas injector have a significant effect on such indicators of the working process as: form, volume and location of the combustion zone; location and intensity of the mixing zone, which, as a consequence, greatly affects the integral parameters of the combustion chamber.
Izvestiya MGTU MAMI. 2017;11(3):14-20
14-20
Optimization of the turbine diffuser of a multipurpose microturbine
Abstract
One of the applications of microturbines is their use as part of a hybrid transmission. This will significantly improve the environmental friendliness of vehicles. One of the problems of microturbines with a radial turbine and heat exchanger is the effective braking of the gas flow behind the turbine in the turbine diffuser. The purpose of this paper is a design study of the flow of gas in diffusers of various designs in order to determine the optimal (for losses of the total pressure and uniformity of the velocity field) structure. For the study, two variants of the layout of the microturbine were taken. In the first case, the axis of rotation of the heat exchanger was located parallel to the axis of rotation of the impeller of the turbine stage, in the second case - perpendicular. In order to minimize losses, the geometry of the output device of the first variant of the arrangement of the microturbine was varied, in particular, the output device without and with deflectors was considered. From the results of calculations it follows that the introduction of deflectors into the geometry of the output device makes it possible to reduce the vortex formation and, correspondingly, the total pressure loss. To determine the loss and the optimal value of the diffuser opening angle, a series of flow computations in the stage of the radial-axial turbine with a variation in the slope angle of the upper generator of the output diffuser α (0.0°, 2.5°, 4.0°, 6.0°, 7.0°) were conducted. A preliminary study was made of the effect of the selected model of turbulence and the size of the grid on the results of the calculation. Analysis of the results of calculations showed that the minimum losses of the total pressure and the maximum increase in static pressure are provided by the diffuser with an angle of inclination of the upper generatrix of 6°. An increase in the angle of inclination of the upper generatrix of 7° leads to developed detachment currents and an increase in losses. A comparative analysis of the obtained data for different versions of the diffuser showed that the second version of the layout of the microturbine (with a straight circular annular baffle diffuser) has significantly lower total pressure losses in the turbine output device.
Izvestiya MGTU MAMI. 2017;11(3):21-27
21-27
Technique for evaluating the efficiency of a V-belt variator in a light vehicle
Abstract
V-belt variators with automatic pressure mechanisms have prevailed in light vehicles, such as scooters, snowmobiles, quads, all-terrain vehicles, etc. In this regard, it is necessary to develop a methodology for assessing the efficiency of the variator to determine the necessary parameters and performance of the V-belt variator of light vehicles. These vehicles have a small mass (up to 750 kg) and cost and, as a rule, are equipped with engines of low power (up to 75 kW). The constructive simplicity and high manufacturability of the manufacture of a few parts of the V-belt variator, and therefore the lowest cost of them, with a sufficiently high reliability level today provided the variator with the maximum value of the indicator in the form of the “reliability / cost” ratio. This is one of the factors that allowed the V-belt variators to gain leadership in the transmissions of these vehicles. To assess the efficiency of the V-belt variator of a vehicle, a method for estimating the instantaneous positions of the variator operation is necessary, which will help determine the instantaneous values of the necessary parameters and give an opinion on the performance of the variator in this state and the subsequent transient, its speed and efficiency. The technique is based on the determination of the axial forces created by the pressure mechanisms and the radial forces arising from them, the tension forces of the belt branches, taking into account the circumferential force from the transmitted torque. The peculiarity of this technique is to determine the exact position (angles of inclination and direction) of these forces both in the plane of the belt contour and perpendicular to it. The developed technique allows to estimate the work of the designed V-belt variator in all possible engine modes. In addition, the methodology shows the reasons for the inefficient operation of the variator, and also provides recommendations for their elimination. Further development of this technique will allow the design of new constructions of variators with the necessary properties.
Izvestiya MGTU MAMI. 2017;11(3):28-40
28-40
Problems in the implementation of the control system for vertical reactions of vehicle wheels
Abstract
One of the new active safety systems of the automobile is a system for stabilizing the vertical reactions of the wheels when moving along a periodic profile. The effectiveness of this system largely depends on the success of measuring the values of the vertical reactions of the wheels of the vehicle in motion. The possibility of solving this problem is considered in the article. As a first method for determining the radial reaction in a tire, the method for estimating the radial force from the change in internal pressure in it is considered. Theoretical analysis of this problem based on solving the simplest models, as well as more advanced models using the finite element method, is presented in the article. Another method for determining the radial force in the tire is to measure the radial deformation of the tire in the area of the contact spot. Two methods for determining radial deformation of a tire are considered in the article. One way is to use laser technology. The laser sensor is fixed to the rim of the vehicle wheel, which ensures a constant measurement of radial deformation at one point of the rotating tire. The use of such a device in the system of stabilizing the vertical reactions of the wheels of the automobile is almost impossible, because the frequency of the desired signal is too small. A more advanced version of the measuring device with a gyroscope ensures the continuity of the direction of the laser beam at one point - the center of the contact spot. This ensures the continuity of measuring the radial deformation of the tire during the movement. Another way is to use an annular chamber with a fluid supported on a ring like a ring fixed on the rim of a so-called “safe” wheel. Increasing the pressure in the chamber during radial deformation of the tire makes it possible to evaluate it. Another method of continuous measurement of radial force on the wheel is associated with performing measurements of the vertical acceleration of the center of the wheel and the total force transferred by the suspension to the wheel of the vehicle.
Izvestiya MGTU MAMI. 2017;11(3):41-48
41-48
Modern methods of synthesis of automatic planetary gearboxes
Abstract
An increase in the number of gears in automotive transmissions is the most efficient way to reduce fuel consumption and improve the efficiency of automotive vehicles equipped with internal combustion engines. The more gears in the gearbox, the more complicated become the used mechanisms and their number increases as well. The article is devoted to the currently used methods of synthesis and design of automotive multi-speed transmissions consisting of planetary mechanisms. Restrictions on the type of planetary mechanisms used and the number of degrees of freedom of synthesized boxes led to a low efficiency of using mathematical and graphoanalytical methods of synthesis developed in the USSR. Currently analytical synthesis method is an exhaustive search of the possible embodiments of joining planetary mechanisms and control elements. This method provides the possibility of using only single-row three-link planetary mechanisms with correct mathematical description. The second basic way of designing planetary gearboxes is the modular principle of synthesis, which consists in attaching and combining some known and used designs with others. In this case, the main modules are single-row planetary gears with single-pair or pair-wise satellites and planetary gears developed by Simpson and Ravigneaux. Most gearboxes developed by German companies are obtained using this particular approach. The article presents kinematic schemes of gearboxes, currently used in transmissions of modern cars, which are obtained as a result of using the described methods of synthesis.
Izvestiya MGTU MAMI. 2017;11(3):49-55
49-55
Optimization of vehicle acceleration process, taking into account the mode of operation of its engine
Abstract
Automotive vehicles are widely used in agriculture for various works. The technique of a choice of optimum gear ratio of a continuously variable transmission of vehicle taking into account the modes of movement and work of its engine is offered. With the purpose of efficient use of engine power resources and implementation of the required indicators of traction-speed and fuel-economic properties of the automobile, manufacturers are trying to impart certain properties to the transmission design that will ensure the most complete coordination of their joint work. The efficiency of the process of coordinating the joint operation of the engine and transmission, determined by the conformity of the designed vehicle to its functional purpose, largely depends on the design methods used. To improve this process, it is necessary to use methods of optimal design. Analytical expressions for the equation of traction balance and, correspondingly, the mathematical model of the vehicle acceleration, depending on the tasks, can and should become complicated. This is indisputable and is determined only by the permissible error in the calculations in each particular case. The paper shows that the regularity of the change in the transmission ratio of a continuously variable transmission can be controlled, and, most importantly, optimal, depending on the mode of vehicle movement. The modern level of development of automation and control means allows to implement this process in practice. The results of calculating the traction-dynamic and fuel-economic parameters of vehicle with continuously variable transmission, the gear ratios of which changed during the movement in accordance with the proposed procedure, in comparison with the actual prototype, confirmed the previously accepted optimization hypothesis and lead to recommendation of the application of this technique in practice when choosing the gear ratios of a continuously variable transmission, depending on the driving mode of the vehicle.
Izvestiya MGTU MAMI. 2017;11(3):56-60
56-60
Mathematical models of tires and calculation of contact pressure on soil
Abstract
When developing a new vehicle for certain tasks, their various characteristics are compared: engine power, mass, payload, etc., the calculation of which is sufficiently reliable. The tire pressure on the contact spot is one of the most important characteristics for determining the index of the off-road flotation of a wheeled vehicle, the determination of which directly depends on the mechanical properties of the tire, the roadway and their interaction. Ground pressure is the pressure exerted on the soil by tires or traces of a motorized vehicle, and is one of the indicators of its potential mobility, especially on softer ground. This article is devoted to the study of tire models and methods for determining the pressure of a wheeled propeller on the soil. The article contains information on the interaction of the tire with different support surfaces, as well as various approaches to the issue of determining the flotation of wheeled vehicles. Modeling the real contact area or the contact profile of the tire provides certain difficulties. Most solutions are based on a contact profile using a helix or an equivalent hard wheel, using a larger hypothetical wheel radius. One of the main models for calculating the tire's contact pressure on the soil is the MMP developed by D. Rowland to assess the maximum pressure of various tires intended for off-road and tracks on soft soils. It is established that, despite scientific achievements in the field of vehicle patency, there are still difficulties in determining the optimum parameters of the wheeled propulsion device to achieve the maximum mobility and environmental friendliness.
Izvestiya MGTU MAMI. 2017;11(3):61-69
61-69
Design and calculation of hydrostatic steering
Abstract
Hydrostatic steering is widespread in the construction of modern tractors. In recent years, it began to apply in designs of haulage trucks and high-speed crawler vehicles. This steering allows for the free arrangement of its main units, simplifies the design, reduces the material consumption of the machine and improves the working conditions of the driver. At the same time, the cost of manufacturing a hydrostatic power steering in recent years has significantly decreased due to the development of high technologies for the manufacture of its units. Hydrostatic steering is a purely hydraulic transmission with flexible connecting pipelines (hoses) of relatively high pressure, less reliable in operation than mechanical tractions, this requires increased attention to the reliability and safety of its operation. For this reason, it is not recommended for use on vehicles with transport speeds above 50 ... 60 km / h. In the known scientific literature there are practically no publications on methods for designing and calculating hydrostatic steering. In the educational literature on tractors, published by professors of the Moscow Polytechnic University, information is given on the design and methods for designing and calculating hydrostatic steering. The task of designing and calculating such a steering is selecting the necessary parameters for the hydraulic cylinder, the metering pump and the power source (drive pump) for it. These units are produced serially, from which the hydrostatic steering is designed. The technique of design and calculation of single-circuit and dual-circuit hydrostatic steering is considered. Information is provided on the characteristics of gerotor type metering pumps of foreign and domestic production.
Izvestiya MGTU MAMI. 2017;11(3):70-75
70-75
Experimental verification of the reliability of the method of designing driving wheels of pin gearing with rubber-reinforced caterpillars
Abstract
The obvious advantages of rubber-reinforced caterpillars over tracks of other types make them indispensable for traction and transport vehicles for various purposes. Among other things, such caterpillars are distinguished by the possibility of their installation on the machine in place of metal caterpillars without a significant alteration of the design of chassis. Nevertheless, together with the replacement of the metal caterpillar with rubber reinforced in practice, it is also necessary to replace the existing driving wheel with a specially designed for rubber-reinforced caterpillar. This happens due to the fundamental differences in caterpillar designs and the features of their work. Until recently, there was no unified engineering method for designing the engagement of the driving wheel with the rubber-reinforced caterpillar. In one of the previous works, the authors developed a technique that takes into account the features of rubber-reinforced caterpillars. This article describes the experimental testing of this technique on the example of a specific machine - self-propelled tracked sprayer for agricultural purposes. Designed in accordance with the developed technique, prototypes of driving wheels in the self-propelled caterpillar sprayer passed a complex of factory tests, including static and dynamic phases. At the static phase of the tests, the input and output of the teeth of the drive wheels were checked from engagement during the assembly of the drive system of the chassis. During the dynamic phase, the reliability of the engagement has been checked at various driving regimes and loads of the self-propelled caterpillar sprayer. In addition, a study was made of the engagement in dynamics with the hung side of the chassis. Experimental studies have confirmed the reliability of the driving wheel samples, the reliability and adequacy of the developed methodology. The recommendations for further investigation of the pin gearing and refinement of the design methodology are given in the paper, including the creation of specialized bench equipment.
Izvestiya MGTU MAMI. 2017;11(3):76-81
76-81