This article presents the results of investigating the influence of tooth contact ratio in helical cylindrical gears on vibroactivity of the gearbox. Based on the measurements carried out on a laboratory test stand, time-domain and frequency-domain start-up characteristics of vibrations and acoustic pressure were determined, and vibroactivity was assessed for a gearbox in which 4 pairs of gears were successively mounted with different face contact ratios equal to, respectively, ε β =1,001; 1,318; 1,574; 2,636.
Combustion engines are the components of means of transport which during service are exposed to the occurrence of excessive clearances. The diagnosing of the condition of the engine requires developing methods which could be useful during both continuous and single checks of the engine. Application of measurements and acoustic signal processing may facilitate a quick diagnosis of the engine without any additional disassembly work. As part of the study, research was conducted to develop a non-invasive method of diagnosing excessive clearance of the combustion engine. Based on the recorded acoustic signals of the combustion engine and reference signals of the momentary crankshaft position, a method was developed to diagnose an increased valve clearance in the combustion engine. In this method, processing of the recorded acoustic signals by means of the continuous wavelet transform was applied together with a comparison of their instantaneous energy, depending on the crankshaft rotation angle and timing angles, as well as the scale parameters of time and frequency distributions.
Vibration analysis is a very important tool in condition monitoring of operating machines. Many signal processing methods have been developed to extract information about incipient faults from externally measured vibration signals. The article presents the laboratory examinations of some faults in spur and helical gears. In case of spur gears two types of progressing local faults of cracked and chipped gear tooth were simulated and the smoothed pseudo Wigner-Ville distribution was used to demonstrate fault advancement via residual vibration signal analysis. Observing changes in the features of the WV distribution in the contour plots and changes of Kurtosis value monitored the progression of a fault. In case of helical gears some signal changes of transverse vibration velocity of shafts during the process of pitting growth in the tooth working surface have been investigated. Some new indices of pitting wear have been suggested and compared with other non-dimensional discriminants.
Currently, fuel cells are increasingly used in industrial installations, means of transport, and household applications as a source of electricity and heat. The paper presents the results of experimental tests of a Proton Exchange Membrane Fuel Cell (PEMFC) at variable load, which characterizes the cell’s operation in real installations. A detailed analysis of the power needed for operation fuel cell auxiliary devices (own needs power) was carried out. An analysis of net and gross efficiency was carried out in various operating conditions of the device. The measurements made show changes in the performance of the fuel cell during step changing or smooth changing of an electric load. Load was carried out as a change in the current or a change in the resistance of the receiver. The analysis covered the times of reaching steady states and the efficiency of the fuel cell system taking into account auxiliary devices. In the final part of the article, an analysis was made of the influence of the fuel cell duration of use on obtained parameters. The analysis of the measurement results will allow determination of the possibility of using fuel cells in installations with a rapidly changing load profile and indicate possible solutions to improve the performance of the installation.
Currently, fuel cells are increasingly used in industrial installations, means of transport and household applications as a source of electricity and heat. The paper presents the results of experimental tests of PEMFC at variable load, which characterizes the cell's operation in real installations. The measurements made show changes in the performance of the fuel cell during step changing or smooth changing of an electric load. Load was carried out as a change in the current or a change in the resistance of the receiver. The analysis covered the times of reaching steady states and the efficiencyof the fuel cell system taking into account additional devices. The analysis of the measurement results will allow determining the possibility of using fuel cells in installations with a rapidly changingload profile and indicate possible solutions to improve the performance of the installation.
The pump structure may involve using fins on the impeller discs to reduce axial thrust. The fins are also used to reduce pressure acting on the discharge-side stuffing box, throw mechanical impurities away and protect the seal against mechanical impurities at the pump impeller inlet. Extensive laboratory tests were performed on finned discs at the water centrifugal flow for different fin widths and gaps between fins and the casing and for different water flow rates. The resulting change in power consumption was determined compared to unfinned discs. The analysis results indicate that fitting the disc with fins involves an increase in power consumption. The consumption rise depends on the centrifugal volumetric flow rate, the fin width and the size of the gap. The dependence of power consumption on the gap size is nonmonotonic-the gap can be optimized to minimize power consumption. The determination of the rise in the consumption of power resulting from fitting the disc with fins and depending on the centrifugal volumetric flow rate is an original outcome of the analysis presented in this paper. The dependence was defined for fins with different values of width and for different sizes of gap. The presented results of the testing can be used in the analysis of power consumption of both finned and unfinned rotating discs. The analysis of power consumption in the impeller pump axial thrust balancing system using balancing vanes is another example of the application of the obtained results.
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