Surge-Induced Structural Loads in Gas Turbines

Mazzawy, R. S.

doi:10.1115/1.3230217

Cited by 34 publications

(10 citation statements)

References 6 publications

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“…In an engine the greatly decreased mass flow through the system can also cause turbine overtemperatures. Surge can be intolerable from the point of view of system operation and can also lead to high blade and casing stress levels [15]. Thus, no matter which type of instability appears when the stall line is crossed, the stall line generally represents a limit to the useful operation of the machine and is therefore to be avoided.…”

Section: Axial Compressor Pumping Systemsmentioning

confidence: 99%

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The Stability of Pumping Systems—The 1980 Freeman Scholar Lecture

Greitzer

1981

Journal of Fluids Engineering

285

131

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A review is presented of the types of instabilities which are encountered in pumping systems of technological interest. These include axial and centrifugal compression systems, pumping systems involving cavitation, systems with two-phase flow, systems with combustion, hydraulic systems, and systems which have two or more pumping elements in parallel. All of the above will be seen to exhibit instabilities under certain operating conditions, although the mechanism of instability, as well as the particular system element that is responsible for the instability, will be quite different in the different systems. However, several basic concepts, such as the idea of negative damping which is associated with dynamic instability, will be seen to be common to the different systems. The review is organized around the different types of systems that are discussed, and includes descriptions of the steady-state performance, the regimes in which one would expect instability, and the mechanisms of instability. An idealized pumping system is first examined to illustrate some of the basic concepts. More realistic systems are then treated in the same manner of showing steady-state performance, regimes of instability and mechanisms. In the review attention is given mainly to those areas in which there is high current engineering interest, and an attempt is made to describe those areas of research which can be most fruitfully pursued. In general, it is suggested that efforts should be directed toward obtaining an improved understanding of the transient behavior of the active (instability causing) elements within the system, since it is lack of knowledge of this aspect that currently limits the accuracy of system stability predictions.

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Section: Axial Compressor Pumping Systemsmentioning

confidence: 99%

“…The results are typified by Fig. 43 which shows polynomial curve fits 15 to the measured pump transfer matrix for a particular impeller [108], [111] (the one whose performance is shown in Figs. 40 and 41).…”

Section: Dynamic Performance Of Cavitating Pumpsmentioning

confidence: 99%

The Stability of Pumping Systems—The 1980 Freeman Scholar Lecture

Greitzer

1981

Journal of Fluids Engineering

285

131

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“…In the past it has been suggested that this type of high speed surge consists of a blast wave which starts at the back of the compressor and sweeps through to the inlet at near sonic speed, the pressure difference across the shock front increasing as the wave approaches the front of the compressor, see Mazzawy (1980) and Cargill and Freeman (1990). In the current tests some evidence of a blast wave has been detected, but there are two other features of these tests which need to be considered first.…”

Section: Surge At High Speed In the Engine Compressormentioning

confidence: 99%

“…Until now there has not been a systematic study to prove that this assumption is correct. Some highspeed data does exist, e.g., Mazzawy (1980), Riess et al (1987), Small and Lewis (1985) and Hosny and Steenken (1986), but, in general, the effects of compressibility have not been studied in any detail.…”

Section: Introductionmentioning

confidence: 99%

The Unstable Behavior of Low and High Speed Compressors

Day

Freeman

1993

Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery

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By far the greater part of our understanding about stall and surge in axial compressors comes from work on low-speed laboratory machines. As a general rule, these machines do not model the compressibility effects present in high-speed compressors and therefore doubt has always existed about the application of low-speed results to high-speed machines. In recent years interest in active control has led to a number of studies of compressor stability in engine type compressors. The instrumentation used in these experiments has been sufficiently detailed that, for the first time, adequate data is available to make direct comparisons between highspeed and low-speed compressors. This paper presents new data from an eight-stage fixed geometry engine compressor and compares this with low-speed laboratory data. The results show remarkable similarities in both the stalling and surging behaviour of the two machines, particularly when the engine compressor is run at intermediate speeds. The engine results also show that, as in the laboratory tests, surge is precipitated by the onset of rotating stall. This is true even at very high speeds where it had previously been thought that surge might be the result of a blast wave moving through the compressor. This paper therefore contains new information about high-speed compressors and confirms that low speed testing is an effective means of obtaining insight into the behaviour of high-speed machines.

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“…When the pressure is increased and the surge line is reached, the pressure wave (hammershock) leads to a first loading of the blade. This is described in some papers, the most important one from Mazzawy [1]. After this, the flow is reversed until the volumes associated with the compressor are empty.…”

Section: Introductionmentioning

confidence: 99%

Aeroelasticity at Reversed Flow Conditions: Part 2—Application to Compressor Surge

Schoenenborn

Breuer

2011

Volume 6: Structures and Dynamics, Parts a and B

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The prediction of blade loads during surge is still a challenging task. In literature the blade loading during surge is often referred to as “surge load”, which suggests that there is a single source of blade loading. In the second part of the paper it is shown that the “surge load” in reality may consist of two physically different mechanisms: the pressure shock when the pressure breaks down and aeroelastic excitation (flutter) during the blow-down phase in certain cases. This leads to a new understanding of blade loading during surge. The front block of a multistage compressor is investigated. For some points of the backflow characteristic the quasi steady-state flow conditions are calculated using a RANS-solver. The flow enters at the last blade row, goes backwards through the compressor and leaves the compressor in front of the inlet guide vane. The results show a very complex flow field characterized by large recirculation regions on the suction sides of the airfoils and stagnation regions close to the trailing edges of the airfoils. Based on these steady solutions unsteady calculations are performed with a linearized aeroelasticity code. It can be shown that some of the rotor stages are aerodynamically unstable in the first torsional mode. Thus, in addition to the pressure shock the blades may be excited by flutter during the surge blow-down phase. In spite of the short blow-down phase typical for aero-engine high pressure compressors, this may lead to very high blade stresses due to high aeroelastic excitation at these special flow conditions. The analytical results compare very well with the observations during rig testing. The correct nodal diameter of the blade vibration is reproduced and the growth rate of the blade vibration is predicted quite well, as a comparison with tip-timing measurements shows. A new flutter region in the compressor map was detected experimentally and analytically.

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Surge-Induced Structural Loads in Gas Turbines

Cited by 34 publications

References 6 publications

The Stability of Pumping Systems—The 1980 Freeman Scholar Lecture

The Stability of Pumping Systems—The 1980 Freeman Scholar Lecture

The Unstable Behavior of Low and High Speed Compressors

Aeroelasticity at Reversed Flow Conditions: Part 2—Application to Compressor Surge

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