Experimental Investigation of Vibrational and Acoustic Phenomena for Detecting the Stall and Surge of a Multistage Compressor

Abstract

Nowadays, the operative range limit of compressors is still a key aspect of the research into turbomachinery. In particular, the study of the mass flow rate lower limit represents a significant factor in order to predict and avoid the inception of critical working conditions and instabilities such as stall and surge. The identification of these instabilities and typical precursors of these two phenomena can imply many advantages, in both stationary and aeronautic applications, such as avoiding the loss of production (in industry) and efficiency of systems and reducing the maintenance and repairing cost. Many approaches can be adopted to achieve this target, but one of the most fascinating is the vibro-acoustic analysis of the compressor response during operation. At the Engineering Department of the University of Ferrara, a test bench, dedicated to the study of the performance of an aeronautic turboshaft engine multistage compressor, has been equipped with a high frequency data acquisition system. A set of triaxle accelerometers and microphones, suitable for capturing broad-band vibration and acoustic phenomena, were installed in strategic positions along the compressor and the test rig. A great amount of vibro-acoustic data were first processed through an innovative data analysis technique, and then correlated to the thermodynamic data recorded. Subsequently, the precursor signals of surge were detected and identified demonstrating the reliability of the methodology used for studying compressor instabilities. The experimental data and results offer a valid alternative way of analyzing and detecting unstable compressor behavior characteristics by means of nonintrusive measurements.

Early surge detection on a turbocharger used to pressurize a SOFC plant emulator

“…In the literature there are numerous theoretical studies and experimental investigations about surge inception where the aim is to allow full control of compressor behavior in the low flow range; indeed, the ultimate goal is to obtain a wider compressor functionality to supply boost pressure at all the required operating conditions [1][2][3][4][5]. Experimental investigations about compressor performance together with analysis of its vibro-acoustic behavior provide useful diagnostic insights; indeed, they enable a reliable early detection of low mass flow rate instabilities [6][7][8][9][10]. Munari et al [6] investigated aeronautic turboshaft gas turbine axial-centrifugal compressor behaviour by developing an experimental activity in operating conditions close to surge line.…”

“…Three peculiar plant configurations characterized by different volume sizes between turbine compressor outlet and recuperator inlet were investigated; the software developed was able to successfully predict surge inception in all operating conditions tested. In [10] the authors developed a vibro-acoustic experimental investigation into fluid-dynamic instability occurring in a compressor made up of six axial stages and a centrifugal one. A sub-synchronous spectral content was detected in system structural response at a low mass flow rate; its energy considerably increased when the valve used to tune external circuit characteristic curve was nearest its closure position.…”

Experimental investigation on the vibrational and fluid dynamics behaviour of a turbocharger compressor in the transition to surge operation

“…In the open literature a lot of theoretical studies and experimental investigations on surge inception are available, with the aim of achieving the full control of the compressor behaviour in low flow range in order to obtain a wider compressor functionality to supply boost pressure at all required operating conditions [2][3][4][5][6]. Experimental investigations on compressor performance together with the analysis of its vibro-acoustic behaviour provide useful diagnostic tools to enable early reliable detection of low mass flow rate instabilities [7][8][9][10][11][12]. In these works, the analysis of the compressor vibro-acoustic response during its operation seems to confirm the possibility of developing reliable diagnostic tools to allow a correct early detection of instability phenomena.…”