No abstract

No abstract

Time frequency analysis of the surge onset was performed in the centrifugal blower. A pressure signal was registered at the blower inlet, outlet and three locations at the impeller shroud. The time-frequency scalograms were obtained by means of the Continuous Wavelet Transform (CWT). The blower was found to successively operate in four different conditions: stable working condition, inlet recirculation, transient phase and deep surge. Scalograms revealed different spectral structures of aforementioned phases and suggest possible ways of detecting the surge predecessors.

Centrifugal compressor machinery is subject to a potentially damaging phenomenon called surge at low mass flow rates. This effect may be preceded by a phenomena known as inlet recirculation -a flow reversal upstream of the impeller. A methodology to isolate inlet recirculation as a characteristic feature for monitoring of centrifugal compressor instability is presented in this study. The methodology is based on a nonparametric time series analysis technique called as singular spectrum analysis (SSA). SSA decomposes a signal into a number of Reconstructive Components (RCs), from which data trends and oscillatory components may be extracted. The frequency spectra of each RC and their relative contributions to the reconstruction of the original signal were examined and comparisons were made with spectral maps in existing literature. Individual and independent RCs were chosen to construct a compressor's instability monitoring system. Additionally, the performance of SSA was determined by the Window length parameter. The effect of modification of this parameter was also studied, and the various viable choices of component for the basis of inlet recirculation diagnosis were considered. The methodology was implemented in pressure dynamical signals measured in an experimental centrifugal compressor rig. High frequency pressure measurements were taken at a number of flow conditions and locations within the compressor. The results demonstrated the potential of a methodology based on SSA to identify and extract oscillatory components with information about the local effect of inlet recirculation and eventually successfully monitor centrifugal compressor's instability.

The aim of this article is to present the application of empirical mode decomposition (EMD) for centrifugal blower flow instabilities detection. The analysis of pressure signal features extracted by EMD technique provides indicators of flow phenomena, which could be used for creating an efficient data-based controller. Quasi-dynamic pressure signals from industrial-size blower are used as an input data for EMD algorithms. An energy-based approach to intrinsic mode functions (IMF) is applied, showing the possibility of condition monitoring and instabilities detection, distinctly displaying surge conditions and inlet recirculation. Different intrinsic mode functions (IMFs) are used to detect different instabilities. EMD also presents some potential in detection of optimal operation conditions for impeller, providing additional benefit for a control system. The possibilities of EMD analysis applied to centrifugal blowers and compressors will be further investigated.

The citations count is flawed but it still the most common way of measuring the academic impact used by scholarly journals (Impact Factor), individual researchers (h-index) and funding agencies (a proxy for quality of research). Individual papers should attract citations depending upon the importance and usefulness of the results presented. However, large enough data sets reveal that there are parameters independent of individual papers' quality that can determine an average citation rate. Here, we examine papers (4756 in total) published in six selected tribology journals in a six-year window between January 2010 and December 2015. Citations were retrieved from the Web of Science and compared with their (1) manuscript length, (2) number of authors, (3) number of affiliated institutions, (4) number of international co-authors, (5) number of cited references, (6) number of words in the title, and (7) mode of publication (open versus paid access). The results revealed that citations received by papers published in tribology journals are affected by all of these parameters. This is a significant finding for authors wishing to increase the impact of their research. This knowledge can be used effectively at the manuscript planning and writing stages to support scientific merit. We suggest that the significance of parameters not directly related to the quality of a scholarly paper will become more critical with the rise of alternative ways of measuring impact including novel generation of paper metrics (e.g., Eigenfactor, SJR), social mentions, and viral outreach.

Methods of dynamical system analysis were employed to analyze unsteady phenomena in a centrifugal blower. Pressure signals gathered at different control points were decomposed into their Principal Components (PCs) by means of Singular Spectrum Analysis (SSA). Certain number of PCs was considered in the analysis based on their statistical correlation. Projection of the original signal onto its PCs allowed to draw the phase trajectory that clearly separated non-stable blower working conditions from its regular operation.

The article is devoted to the experimental investigation of the interactions between the amplitudes and frequencies of surge in a single-stage centrifugal blower and the configuration of its inlet duct. In this work, the term 'configuration' implies the combination of the following: the volume of the duct, the presence of the filter inside the duct and the inlet guide vane position. The high-response pressure measurements were performed at three points along the impeller shroud (inlet, middle, outlet) and at a single point downstream the volute outlet and then processed with the use of fast Fourier transform (FFT). The results of the measurements show that the response of the surging system to a change introduced into the duct's configuration is complex. The closure of the inlet guide vane typically causes a drop in the amplitude and frequency of fluctuating pressure. The introduction of a filter body into the duct most often damps the amplitudes of fluctuations, but leaves the frequencies unaltered. The change of the duct's volume controls the rate of this damping.