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.
*The influence of plenum volume on surge phenomenon in a centrifugal blower was studied by means of quasidynamic analysis. In this procedure, signals were gathered at 5 pressure tappings at 146 different positions of the throttling valve controlling the mass flow rate. Frequency spectra obtained by means of Fourier analysis are combined together in the form of colour maps with frequency as the abscissa and valve position as the ordinate. Such a map provides high-resolution information about spectral structures of pressure signals attained at different mass flow rates. Analysis was conducted at two system configurations characterized by different volumes between the blower and the valve i.e. plenum volume. Research confirmed that in both cases the first disturbances appear in the vicinity of the impeller leading edge in the same position of a throttling valve before the surge. Arising flow structure is characterized by strong and random pressure jumps and does not have any dominating frequency. At further valve closure pressure disturbances propagate towards the volute and at deep surge the strongest peaks are observed at the outlet. The moment of deep surge onset is also independent of the plenum volume, however, a difference is observed in the frequency and amplitude of the main modes. With the higher outlet volume the observed oscillations fit well to the frequency of a Helmholtz resonator while, in the case of the smaller volume, the frequency is higher than the frequency of a corresponding Helmholtz resonator. † ASME member
The paper focuses on experimental investigation of the influence of outlet network volume and type on the course of surge in a single-stage low-speed centrifugal compressor. The test rig design is based on a 330 mm impeller (tip Mach number of 0.33) coupled with a vaneless diffuser and a scroll. During the measurements, the rig has been successively connected to a four meter long pipe and to an 11.8 m deep well. Time-averaged probing of pressures and temperatures has served to obtain the performance maps with both networks at three different positions of inlet guide vanes. Timeresolved measurements of static pressure were done in three chosen locations of the rig and enabled to trace the formation of flow instabilities at low flow rates. The analysis of received dataset revealed a reasonable impact of network design on the inception moment, quantitative and qualitative traits of deep surge. The most significant changes concerned the frequencies of the first surge harmonics and the nature of the process. ''Pipeline-surge'' reminded more of a standing wave whereas ''plenum-surge''-of a periodic process similar to the ones reported in the referenced studies.
The paper presents the results of mathematical simulation of the characteristics of a vane diffuser of a centrifugal compressor intermediate stage, such as the loss coefficient and the deviation angle versus the outlet vane angle of the diffuser. The simulation of these characteristics was made on the basis of processing the results of studies performed by the Research Laboratory “Gas Dynamics of Turbomachines” of Peter the Great St.Petersburg Polytechnic University at the model characteristics of vane diffusers. Given the almost complete absence of recommendations in the literature, the paper describes the technology for constructing neural network models, which includes preparing a sample of input data and determining the optimal structure of the neural network. Based on the obtained mathematical models, a computational experiment was carried out in order to determine the influence of the main geometric and gas-dynamic parameters on the efficiency of vane diffusers. The results of the computational experiment on neural models of the efficiency of a vane diffuser are analyzed according to the existing ideas about the physics of the processes of energy conversion in a vane diffuser.
The article is devoted to the description of the modernization of a multihull process centrifugal compressor for synthesis gas. The main reason for the revamp was the desire to adapt the conventional machine (45 years of operation) for newer operational requirements: the decrease of compressor discharge pressure to the level of 140 bar from the level of 211 bar with the corresponding alteration of the mass flow rate. The scheme accepted as a final modernization conception required the manufacturing of three completely new rotor and casing assemblies. Major design modifications concerned the impellers' geometry, introduction of vaneless diffusers and the abradable labyrinth seals. Most of the stages were "optimized" using the in-house semi-empirical 1D code and ANSYS CFX commercial code. The performance of a single optimized stage was tested experimentally. The paper reveals the main results of these measurements and their comparison to numerical simulations results. The start-up tests of the modernized assembly showed its almost 100% conformity to the requirements in the output and the efficiency rise of about 5%.
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