Centrifugal Turbocompressors Research Articles

Detection of centrifugal turbocompressor surge by drive motor current

The article deals with the case of surging of a turbocompressor unit. Mathematical modeling of the situation under consideration is carried out and its influence on the stator current of the electric motor is estimated. The analysis of the simulation results with the corresponding conclusions is made. A surge detection device is proposed.

Experimental methodology for turbocompressor in-duct noise evaluation based on beamforming wave decomposition

An experimental methodology is proposed to assess the noise emission of centrifugal turbocompressors like those of automotive turbochargers. A step-by-step procedure is detailed, starting from the theoretical considerations of sound measurement in flow ducts and examining specific experimental setup guidelines and signal processing routines. Special care is taken regarding some limiting factors that adversely affect the measuring of sound intensity in ducts, namely calibration, sensor placement and frequency ranges and restrictions. In order to provide illustrative examples of the proposed techniques and results, the methodology has been applied to the acoustic evaluation of a small automotive turbocharger in a flow bench. Samples of raw pressure spectra, decomposed pressure waves, calibration results, accurate surge characterization and final compressor noise maps and estimated spectrograms are provided. The analysis of selected frequency bands successfully shows how different, known noise phenomena of particular interest such as mid-frequency “whoosh noise” and low-frequency surge onset are correlated with operating conditions of the turbocharger. Comparison against external inlet orifice intensity measurements shows good correlation and improvement with respect to alternative wave decomposition techniques.

On the occurrence of self-synchronization of autooscillations of turbocompressor rotor blades

The self-synchronization of the spectral parameters of turbocompressor blades is studied, as well as its connection with nonlinear resonance during fluttering. The evolution of blade oscillations during the growth of turbocompressor rotor revolutions is characterized by the concurrence of torsional and flexural oscillation modes, a change of the base frequencies of the rotor blades, and the appearance of a common synchronization frequency in their spectrum. Fluttering comes with a loss of stability of the blades’ oscillation mode at the synchronization frequency. Estimates are obtained on the basis of the spectral analysis of the recording of transient processes of axial and centrifugal turbocompressors. The parameters of the blade oscillation modes and their power have been identified by means of the construction of models of the processes on the basis of the technology of Proni spectral analysis.

Rotor Stability of High Pressure Multistage Centrifugal Compressors

A major factor influencing rotor stability of multistage high pressure centrifugal turbocompressors are the forces caused by the fluid-rotor interaction in the interstage and balance piston gas seals. An example of a fully 3-D labyrinth flow solution shows that using time averaged Navier-Stokes solutions are still excessive in computer time and hence cannot be used for practical applications. The paper gives a theory based on a two-volume bulk flow model for the prediction of the rotor-dynamic coefficients used for rotor stability calculation by complex eigenvalue analysis. Comparisons of predicted coefficients with measurements carried out on a high pressure compressor and on labyrinth seal test stands are given. The theoretically predicted phenomenon that labyrinth damping is retained even at zero inlet swirl of the leakage flow is confirmed. An example of a stability analysis of a high pressure natural gas compressor is given, where the stability margin increases with fluid pressure, i.e., density, provided seal swirl is controlled.

Optimization of a pipe-line for the natural gas transportation

This paper deals with the problem of optimizing the management of a natural gas transportation pipe-line. The system is formed by m compressing stations linked by pipe-legs. Each station S i is equipped with N i centrifugal turbocompressors; its behaviour is characterized by the actual number n i of operating turbocompressors and by the values of the machine flow-rate and of the suction and discharge pressures and temperatures. A fraction of the gas passing through the station is used for the feeding of the turbocompressors (fuel-gas). For each station S i it is necessary to find the optimal values of n i and of the discharge pressure so as to minimize the total amount of fuel-gas (inclusive of the quantity needed for turbocompressors start-stop operations), taking into account the constraints on the pressures and temperatures in the stations and along the pipe-legs. Sophisticated simulation models of the stations and of the pipe-legs are presented and justified by means of experimental tests. An algorithm based on a dynamic programming formulation of the problem is proposed; the algorithm utilizes dominance criteria and lower bounds in order to reduce the total number of states. Extensive computational results referring to a set of real situations are given in order to evaluate the saving with respect to the current manual management of the system. The results reported in this article have been applied to the gas transportation pipe-line that is operated by ÖeMV (Austria) and SNAM (Italy).