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Optimisation of Flow Rates in Lubrication Systems with Progressive Distributors by means of Genetic Algorithms
Vepřek, Jiří ; Pavlok, Bohuslav (referee) ; Bauer, František (referee) ; Habán, Vladimír (referee) ; Nevrlý, Josef (advisor)
This doctoral thesis presents the results of the development of two software programs for the design of progressive distributors and progressive lubrication systems. One of these programs implements a genetic algorithm and the other, which is used to design progressive lubrication systems, implements a parallel genetic algorithm of the island model. The program for the design of progressive distributors was implemented in Java using the NetBeans development environment and the other program was created in Matlab. The thesis further focuses on analytical and computational solutions of the flow of compressible greases seen as viscoplastic fluids. Equations for the numerical solution of the non-steady flow of compressible viscoplastic Bingham fluids were derived and solved by the Lax-Wendroff method in Matlab. As several constants had to be set in the equations, experiments were conducted with the ecological grease Plantogel 2S in the laboratory of the Kaplan Department of Hydraulic Machines, mainly to determine the sound velocity in this grease. The sound velocity was calculated based on the experimental results by applying Fourier transformation and the transition matrix method. In addition to this, the rheological measurements of greases were used. As seen from the results, the ecological greases are actually thixotropic viscoplastic fluids with a significant elastic element. Since a Newton fluid was assumed when calculating the sound velocity, the possibilities of using the transition matrix method for viscoplastic fluids were then considered. No analytical solution of the flow of viscoplastic fluids in a frequency spectrum has been published so far. Because it emerged that greases had a significant elastic stress factor, the problem of the non-steady flow of elastic-viscoplastic fluids was solved numerically between two infinite parallel plates by applying the finite difference method (FDM). The computation was done in Matlab. This doctoral thesis makes a contribution to solving problems related to the design of progressive distributors and progressive lubrication systems used to distribute compressible greases. Considering the complex approach to this field and the achieved results, the thesis also represents a significant contribution to design work.
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Vehicle Kinematics and Dynamics Simulations
Zháňal, Lubor ; Bauer, František (referee) ; Píštěk, Václav (referee) ; Kaplan, Zdeněk (advisor)
This paper focuses on the kinematic and dynamic numerical simulation of mechanisms by applying a numerical method, and a complex simulation programme built on it, developed by the author. Described are mathematical principles of the numerical method used and also the programming progression of the important parts of the application and its optimization. The final part includes comparative measuring of the accuracy and performance.
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Analysis of Zetor tractor output parameters with different gearbox design
Orság, Josef ; Škopán, Miroslav (referee) ; Bauer, František (advisor)
This thesis deals with energetical and efficiency comparison of two tractor transmission types, used by the Zetor company. The description of transmission construction types of various tractor producers is given, with focus on Zetor tractors transmission construction. The laboratory methodology and operating tractor and tractor sets measurement is described. The individual results are introduced in tables and graphs and subsequently evaluated.
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Powertrain Vibration Modelling using Virtual Prototypes
Prokop, Aleš ; Bauer, František (referee) ; Dundálek, Radim (referee) ; Novotný, Pavel (advisor)
This work deals with the matter of powertrain vibration reduction, focusing on the transmission. These units, depending on the purpose of utilization, consist of a high number of dimensionally complex components. These need to possess features, selected already in the design phase, which would guarantee smooth and quiet operation. A properly designed tooth profile and the related specified accuracy of manufacturing are one of the most important features. The basic function and the purpose of transmissions application indicate a relatively wide range of operating speeds and transmitted loads. Moreover, combination of both loading with improperly designed string’s parameter can cause a number of various problems. The vibration initiation with related noise from gear mesh belong to the most significant sources of issues. There are multiple mechanisms of oscillation initiation. Even when using the latest trends in the development of teeth, when their shape is upgraded and developed to meet specifically given load range, the above mentioned irregularity of transferred torque cannot be completely eliminated. Therefore, it is necessary, already in the design phase, to eliminate the transmission paths by which are vibrations transmitting to other components. People perceive this action in the form of vibration, noise, or temperature change in the surroundings. With the increasing comfort levels and number of produced vehicles the reduction of vibration and noise of machinery parts becomes stricter, including gears. The experimental approach is primarily used to assess the accuracy of designed gearboxes, but it is a very expensive and a time consuming method. Therefore, it is necessary to develop a process that utilizes both numerical simulation and experimental approach but also combines the advantages of both, particularly time and cost savings and comparability of results. For this purpose, the experimental gearbox is designed and manufactured including the single-stage gear enabling variable configurations in terms of the ratio change. The gearbox is subjected to numerical simulation of different complexity levels, as well as technical experiment. Furthermore, the universal virtual prototype in Multi-Body System ADAMS is created, which reflects the impact of several key parameters for proper functionality, such as axial distance, backlash, gear mesh stiffness, shaft mounting stiffness (bearings) and modal properties of the shafts and gearbox housing. Last but not least, the impact of imbalance or irregularity of input shaft speed is incorporated. The last part focuses on a brief description of the application of the presented methodology – modelling of vibrations on the tractor gearbox.
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Limiting and Degradation Processes of Magnetorheological Suspension Dampers
Roupec, Jakub ; Bauer, František (referee) ; Ondrůšek, Čestmír (referee) ; Dobeš, Petr (referee) ; Mazůrek, Ivan (advisor)
This work deals with the research of degradation of magnetorheological (MR) fluid during long-term loading under conditions that correspond to the real load in the linear MR devices such as dampers. The behaviour of MR fluid is described by a Bingham model of viscoplastic fluid. The parameters of this model are the yield stress and viscosity. Their values are determined by the shear rate from 1 to 2,8104 s-1. Results of durability tests show a significant decrease in viscosity of MR fluid, a gradual increase in yield stress in the off-state and a significant decrease in MR effect. The paper also described the effect of temperature on these parameters and there is also designed a method of non-assembly diagnostic of the MR fluid state in the damper using the "rate of pulsation."
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The influence of the chassis to the power and performance characteristics of tractors
Rašovská, Hana ; Slimařík, Dušan (referee) ; Bauer, František (advisor)
This master thesis deals with the influence of the type of tractor chassis on its utility properties. For the rating were used tractors John Deere 8 – series with wheel and track chassis, equipped with the same engine and gearbox, which were carried out for laboratory and field tests. The aim of laboratory tests was the exclusion of the difference in engine power of both tractors and the aim of field tests was to evaluate the drawbar properties of tractors with a different type of chassis. The reference parameter was especially drawbar pull, further drawbar power, slip and fuel consumption. Based on the tabular and graphical elaboration of the measured values were evaluated results.
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The effect of tyres on the output parameters of tractors
Kopečný, Aleš ; Havlíček, Miroslav (referee) ; Bauer, František (advisor)
The thesis summarizes the results of the measurement of the output parameters of the tractor, on which were mounted three different types of tires. The measured parameters are the maximum pulling power, slippage, specific effective fuel consumption at the maximum pulling performance. The final measured and calculated results are presented in tables and graphs. The results of the measurements were processed by the use of regressive analysis.
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The influence of the chassis on drawbar properties of tractors
Chmelař, Zdeněk ; Havlíček, Miroslav (referee) ; Bauer, František (advisor)
In this master thesis is analyzed the current situation in the construction chassis of tractors, in addition, a methodology for evaluating the impact of influences on drawbar properties of tractors. The main objective of this work was to analyze and conclude the measured drawbar properties of selected tractor same power and weight categories with different chassis designs. Measured and calculated values were tabular and graphically presented. When evaluating the drawbar properties were determined according tractive power and slip depending on the drawbar forces.
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