Aleksander Mazurkow

As the literature indicates, spiroid gears are characterized by a compact design and small space required for their installation, so they are used in modern drive systems of many means of transport. In practice, they constitute an alternative solution to worm gears. It is emphasized that in the...

The efficiency and reliability of the propulsion system of, for example, a vessel equipped with a supercharged combustion engine, largely depend on a properly working turbocharger. Despite the use of a sophisticated bearing system and a turbocharger rotating assembly, its constructors struggle with ensuring its dynamic stability. This study presents a dynamic model of a turbocharger rotating system, along with the corresponding numerical calculations. The model addresses the issue of vibration damping in non-locating plain bearings and its impact on the rotating unit of the turbocharger. As a result of numerical calculations, the areas of stable operation of the rotating unit were obtained. It can be concluded that the floating ring bearings used in the turbocharger effectively suppress the vibroacoustic effects accompanying the operating rotating assembly. Furthermore, the analyses indicate that the causes of turbocharger malfunction can be attributed to excessive imbalance in the rotating assembly and the improper stiffness of the rotating unit. The presented research may be beneficial in practice, providing insight into how to extend the service life of not only the power unit itself, but also the turbocharger.

Viscous torsional vibration dampers are used to dissipate the energy of the periodically varying rotational motion of the crankshaft. The paper discusses the wear processes that can occur during the operation of dampers. The authors defined the static characteristics of a damper, including the thermal power generated by, the t friction forcesemperature of the damper housing, the position of the inertia ring relative to the housing and the oil flow resistance coefficients. The calculated static characteristics take into account the friction occurring in the oil filling the spaces between the cylindrical and frontal surfaces of the inertia ring and the housing. Pressure distributions in the oil film were presented for a given relative velocity. The effect of the relative velocity on the housing temperature was determined and the relative velocity range in which the oil temperature will not exceed the permissible value was determined.

Improving the reliability and durability of internal combustion engines in marine vessels is a complex issue. The vibrations generated in these engines significantly affect their proper operation. One of the current research challenges is identifying effective methods to reduce, among other things, torsional vibrations generated within the crank–piston system. To mitigate these vibrations, viscous dampers are commonly used. The selection of a viscous damper for a high-power multi-cylinder engine, such as those in marine power plants, requires a thorough understanding of the thermo-hydrodynamic properties of oil films formed in the spaces between the damper housing and the inertial mass. The description of the phenomena involved is complicated by the variable positioning of the inertial mass center relative to the housing during operation. Most previous studies assume a concentric alignment between these components. The main novelty of this work lies in highlighting the combined effect of the eccentric motion of the inertial ring on both hydrodynamic resistance and thermal characteristics, which has not been fully addressed in existing studies. This article defines the oil flow resistance coefficients and develops static characteristics of the dampers. Additionally, it evaluates the impact of the size of the frontal and cylindrical surfaces of the damper on its heat dissipation capacity. The presented characteristics can be utilized to assess the performance parameters of this type of damper.

Spiroid gears are used in the drive systems of various types of vehicles and devices. They are characterised by small overall dimensions and significant rotational speed reduction while maintaining the high positioning accuracy of the driven device. Spiroid gears require a lot of lubrication with oils, which separate the mating parts. In the case of spiroid gears, they separate the face wheel teeth and the worm thread. The resulting oil film reduces the coefficient of friction and lowers the temperature of the mating surfaces. The modelling of toothed rim lubrication is a complex problem. To separate the surface of the face wheel mating and the worm, one needs to consider the phenomena of fluid mechanics, heat transfer and tooth deformation. The formation of an elastohydrodynamic oil film of an appropriate height is determined by the type of oil, the mechanical properties of the worm and face wheel materials, relative speed, load and the geometry of the mating surfaces. The issues described in this paper significantly affect the correct operation of gears and have not yet been fully understood for spiroid gears. This paper presents the results of a study on the properties of the elastohydrodynamic oil film and describes its characteristics, with the unknown quantity being the rotational speed of the input shaft that ensures that the oil film separates the mating toothed rims. The calculation results were compared with those of other researchers. The obtained design recommendations can help designers improve the durability and reliability of spiroid gears.

Obtaining the best operating parameters of the internal combustion engine has focused the attention of designers and researchers since the first years of its creation. Initial research focused on increasing engine power and overall efficiency. As time passed, these aspirations became more sophisticated and began to concern other operating parameters of the drive unit. The basic problem, however, remained the improvement of filling the cylinder with the working medium. Turbocharger charging consists in using the energy of the exhaust gases to drive a turbine placed on a common shaft with a compressor supplying air under increased pressure to the cylinders. Over time, the turbocharger became one of the key elements and its technical condition began to play a key role in the operation and performance of modern drive units. Like every element, the turbocharger itself is not without its faults. This procedure is known among manufacturers who, when designing power units and their assemblies, pay special attention to the essence of turbocharger construction. Since it is impossible to predict all the phenomena accompanying a working turbocharger at the design stage, the authors of this paper conducted bench tests of a selected batch of turbochargers, focusing mainly on the vibration measurements of the turbocharger rotating assembly. At the same time, we present a dynamic model of the mentioned system based on the analyses resulting from the solutions of the equations of a numerical model. In order to give the research a practical aspect, the results of the theoretical research were compared with the results of bench tests. It has been shown that the basic problem is to guarantee the correct operating parameters of the bearings in the position of static and dynamic equilibrium. Obtaining such operating parameters requires finding a compromise solution, e.g., between the maximum temperature in oil films and the amplitudes of vibration accelerations in bearing nodes. The research results presented in the article can be used as a field for further discussion in the field of research on the reliability of turbochargers and be helpful in the design process in order to avoid design errors and reduce production costs.

Radial slide bearings are typically used in turbochargers (among other applications), owing to their simple design and advantages, such as good heat dissipation from the working zone, high stability of operation and low resistance to motion. The current research is both experimental and theoretical. In a state of static equilibrium, the operation of a bearing can be described using a system of five coupled differential equations. The bearing’s operating parameters are related to the type of oil used. Two types of oil, VG46 and VG68, were used for testing. In accordance with the applicable standard, the tolerance of kinematic viscosity of oils is ±10%. The results imply a significant influence of the oil class and viscosity tolerance on the resistance to motion caused by internal friction forces in the oil. In conclusion, it seems advisable that the calculation procedures currently in use should include the slide bearing design optimisation by taking the resistance to motion in the bearing into account.

Spiroid gears are used to transfer heavy loads with a significant reduction in input speed. Like most toothed gears, they are lubricated with oil whose physical properties change with temperature fluctuations, affecting the durability and reliability of the gear. Bearing this in mind, gear designers plan systems for measuring oil temperature during gear operation at the design stage. The authors of this paper are of the opinion that, in the case of spiroid gears, it may be insufficient to measure only oil temperature during gear operation. It seems that the working temperature of a pair of mating wheels has a decisive impact on the durability and reliability of the gear. The measurement of oil temperature in a tested gear should be treated as a supplementary measurement with the measurement of temperature on the toothed wheels as the basic measurement. Taking into consideration the above, an innovative test bench was designed and built, making it possible to observe how working parameters of the gear (torque and rotational speed) affect the temperature of the lubricating oil, but most of all, the working temperature of the pair of mating wheels. This paper presents, among others, the results of research on the impact of the rotational speed of the input shaft and load on the distribution of temperature on the toothed rim of the face gear.