Operation extension in gas turbine-based advanced cycles with a surge prevention tool

Abstract

This work aims to present the development and testing of an innovative tool for surge prevention in advanced gas turbine cycles. The presence of additional components, such as a saturator in humid cycles, a heat exchanger for an external combustor, a solar receiver or fuel cell stack in a hybrid system, implies the presence of larger size volumes between compressor outlet and recuperator or expander inlet. This large volume increases the risk of incurring in surge instability, especially during dynamic operations. For these reasons, at the University of Genoa, the Thermochemical Power Group (TPG) has implemented four surge precursors in a new diagnostic real-time software which can recognise a surge incipience condition comparing the precursor values with a set of moving thresholds. The most innovative aspects of this work are: (i) operational range extension and safer management of advanced gas turbine systems for energy generation, (ii) positive impact in energy efficiency due to this range extension of high efficiency systems, (iii) development of a new diagnostic tool for surge prevention using standard probes, (iv) small impact of this tool on the control and sensor costs, (v) software flexibility for adaptation to different conditions and machines. This very important final aspect is obtained with thresholds able to change automatically to adapt themselves to the plant and machine operational regime. From the cost point of view, the utilization of standard measurements is an essential requirement to equip commercial machines without significant impact on the capital costs. The software performance has been demonstrated using experimental data from a test rig composed of a T100 microturbine connected with a modular vessel, which permits to generate the effect of additional components (especially from the volume size point of view). Vibro-acoustic data, collected during machine transients from a stable operative condition to surge, were used to tune all the software parameters and to obtain a good surge predictivity.

Instability Phenomena in Centrifugal Compressors and Strategies to Extend the Operating Range: A Review

“…More recently, a vibrational analysis has been used to identify surge precursors [61][62][63]. Cabral et al [64] proposed a specific method based on the fully acoustic two-port model for the study of centrifugal compressor stall and surge inception.…”

A comparison of strategies to extend the operating range of radial compressors for turbocharging

“…Similar CFD models can be used also for more complex cases like a two-stage radial compressor for air conditioning [33] or for aeroacoustical tonal noise prediction [34]. On the experimental side, the vibrational analysis can be effectively used as surge precursor [35][36][37]. In this work, a centrifugal compressor stage, equipped with various device to extend the surge margin, is studied with a CFD model in order to be understand the effects on performance and on the extension of the operating range of the different casing treatment solutions.…”

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.…”

“…In [8] the authors experimentally investigated vibro-acoustic signature of two automotive centrifugal compressors; the goal was to identify peculiar contents onset in compressor response in incipient surge conditions for early surge detection. Reggio et al [9] introduced an innovative tool for real-time surge prevention in advanced gas turbine cycles which is described in detail and implemented. The software was validated with data from a test rig made up of a micro-turbine connected with a modular vessel.…”