Influence of Compressor Deterioration on Engine Dynamic Behavior and Transient Stall-Margin

1999 ◽  
Author(s):  
Z. S. Spakovszky ◽  
J. B. Gertz ◽  
O. P. Sharma ◽  
J. D. Paduano ◽  
A. H. Epstein ◽  
...  
Keyword(s):  
Analytical Investigation ◽  
Tip Clearance ◽  
Shaft Speed ◽  
Rotor Speed ◽  
Commercial Aircraft ◽  
Stall Inception ◽  
Stall Margin ◽  
Engine Dynamic ◽  
System Mode ◽  
Flow Blockage

This paper presents an experimental and analytical investigation of compressor stability assessment during engine transient operation. A 2-dimensional, linear, compressible, state-space analysis of stall-inception (Feulner et al. (1996)) was modified to account for engine transients and deterioration, with the latter modeled as increased tip-clearance and flow blockage. Experiments were performed on large commercial aircraft engines in both undeteriorated and deteriorated states. Unsteady measurements of pressure in these test engines during rapid accelerations revealed the growth of pre-stall disturbances, which rotate at rotor speed and at approximately half rotor speed. These disturbances are stronger in deteriorated engines. The model showed that the signal at shaft speed was the first compressible system mode, whose frequency is near shaft speed, excited by geometric nonuniformities. The computed behavior of this mode during throttle transients closely matched engine data. The signal increased in strength as stall was approached and as the engine deteriorated. This work firmly establishes the connection between observed signals in the these engines and first principles stability models.

Influence of Compressor Deterioration on Engine Dynamic Behavior and Transient Stall-Margin

1999 ◽  
Vol 122 (3) ◽  
pp. 477-484 ◽  
Author(s):  
Z. S. Spakovszky ◽  
J. B. Gertz ◽  
O. P. Sharma ◽  
J. D. Paduano ◽  
A. H. Epstein ◽  
...  
Keyword(s):  
Analytical Investigation ◽  
Tip Clearance ◽  
Shaft Speed ◽  
Rotor Speed ◽  
Commercial Aircraft ◽  
Stall Inception ◽  
Stall Margin ◽  
Engine Dynamic ◽  
System Mode ◽  
Flow Blockage

This paper presents an experimental and analytical investigation of compressor stability assessment during engine transient operation. A two-dimensional, linear, compressible, state-space analysis of stall-inception (Feulner et al., 1996, ASME J. Turbomach., 118, pp. 1–10) was modified to account for engine transients and deterioration, with the latter modeled as increased tip-clearance and flow blockage. Experiments were performed on large commercial aircraft engines in both undeteriorated and deteriorated states. Unsteady measurements of pressure in these test engines during rapid accelerations revealed the growth of pre-stall disturbances, which rotate at rotor speed and at approximately half rotor speed. These disturbances are stronger in deteriorated engines. The model showed that the signal at shaft speed was the first compressible system mode, whose frequency is near shaft speed, excited by geometric nonuniformities. The computed behavior of this mode during throttle transients closely matched engine data. The signal increased in strength as stall was approached and as the engine deteriorated. This work firmly establishes the connection between observed signals in the these engines and first principles stability models. [S0889-504X(00)01603-2]

Effects of Rotating Inlet Distortion on Multisage Compressor Stability

1994 ◽  
Author(s):  
J. P. Longley ◽  
H.-W. Shin ◽  
R. E. Plumley ◽  
P. D. Silkowski ◽  
I. J. Day ◽  
...  
Keyword(s):  
Theoretical Model ◽  
Stability Margin ◽  
Rotating Stall ◽  
Forced Response ◽  
Single Peak ◽  
Rotor Speed ◽  
Stall Inception ◽  
Stall Margin ◽  
Inlet Distortion ◽  
Two Peaks

In multi-spool engines, rotating stall in an upstream compressor will impose a rotating distortion on the downstream compressor, thereby affecting its stability margin. In this paper experiments are described in which this effect was simulated by a rotating screen upstream of several multistage low-speed compressors. The measurements are complemented by, and compared with, a theoretical model of multistage compressor response to speed and direction of rotation of an inlet distortion. For co-rotating distortions (i.e., distortions rotating in the same direction as rotor rotation), experiments show that the compressors exhibited significant loss in stability margin and that they could be divided into two groups according to their response. The first group exhibited a single peak in stall margin degradation when the distortion speed corresponded to roughly 50% of rotor speed. The second group showed two peaks in stall margin degradation corresponding to distortion speeds of approximately 25–35% and 70–75% of rotor speed. These new results demonstrate that multistage compressors can have more than a single resonant response. Detailed measurements suggest that the two types of behavior are linked to differences between the stall inception processes observed for the two groups of compressors and that a direct connection thus exists between the observed forced response and the unsteady flow phenomena at stall onset. For counter-rotational distortions, all the compressors tested showed minimal loss of stability margin. The results imply that counter-rotation of the fan and core compressor, or LP and HP compressors, could be a worthwhile design choice. Calculations based on the two-dimensional theoretical model show excellent agreement for the compressors which had a single peak for stall margin degradation. We take this first-of-a-kind comparison as showing that the model, though simplified, captures the essential fluid dynamic features of the phenomena. Agreement is not good for compressors which had two peaks in the curve of stall margin shift versus distortion rotation speed. The discrepancy is attributed to the three-dimensional and short length scale nature of the stall inception process in these machines; this includes phenomena that have not yet been addressed in any model.

Pre-Stall Disturbances and Stall Inception for an Eccentric Low-Speed Axial Compressor with Inlet Swirl

2020 ◽  
Author(s):  
Xuegao Wang ◽  
Jun Hu ◽  
Jin Guo ◽  
Chao Jiang ◽  
Zhiqiang Wang
Keyword(s):  
Axial Compressor ◽  
Tip Clearance ◽  
Tip Leakage Flow ◽  
Stall Inception ◽  
Stall Margin ◽  
Flow Unsteadiness ◽  
Time Operation ◽  
Long Time ◽  
Inlet Swirl ◽  
Assembly Error

Abstract Owing to the manufacturing and assembly error or the fatigue of long-time operation, nonaxisymmetric tip clearance is actually a common phenomenon in compressors. It's also well accepted that tip leakage flow, associated with tip clearance size and loading, has a strong influence on the performance and stall inception of compressors. The work of this paper, based on an eccentric compressor with/without inlet swirl distortion, is aimed at strengthening the understanding of stall inception for a real geometry compressor experimentally. Results indicate that rotor tip blockage and flow unsteadiness vary evidently around the circumference. For this compressor, the maximum tip flow unsteadiness and blockage happens at the location near the minimum clearance under the condition of clean inlet flow. Before the occurrence of stall inception, disturbances arise and vanish intermittently within the region of high unsteadiness. However, it fails to rotate due to the inhibition of the low unsteadiness region. Once the most robust region is no longer able to suppress disturbances, stability finally breaks down and stall inception generates. After exerted inlet paired swirl, unsteadiness within the region of positive pre-swirl decreases significantly and the maximum unsteadiness location shifts, while the increase for the region with negative pre-swirl is nearly negligible. As a result of that, stall margin of the compressor is improved.

Experimental Study of Modal Disturbance and Rotating Stall Distribution

2013 ◽  
Vol 718-720 ◽  
pp. 1804-1810
Author(s):  
An Qing Lai ◽  
Jun Hu ◽  
Liang Li ◽  
Ju Luo
Keyword(s):  
Axial Compressor ◽  
Leading Edge ◽  
Propagation Speed ◽  
Axial Direction ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Rotor Speed ◽  
Stall Inception ◽  
Tip Clearance Flow ◽  
Modal Type

To execute stall active control technology effectively and make clear of stall inception induced by modal disturbance, this paper carries out the correlative research on modal disturbance and rotating stall on the two-stage low-speed axial compressor. The results indicate that the stall inception of the compressor is modal style and the modal oscillation propagates at 38% rotor speed while the stall cell propagation speed is 42% rotor speed. The phase angles of modal oscillation and rotating stall along the axial direction are different, but their trajectories are both similar to the blade passage shape. The stall mechanisms of modal-type and spike-type inceptions are different. It doesnt appear that leading-edge tip clearance flow spillage blow the blade tip while the modal-type stall formation.

Numerical Investigation of Cut-Corner in Recess Vaned Casing Treatment

2019 ◽  
Author(s):  
Xiangyi Chen ◽  
Wuli Chu ◽  
Haoguang Zhang ◽  
Bo Luo
Keyword(s):  
Main Flow ◽  
Tip Clearance ◽  
Axial Fan ◽  
Stall Margin ◽  
Casing Treatment ◽  
Stable Operating ◽  
Flow Circulation ◽  
Blade Tip ◽  
Flow Blockage ◽  
Blade Tip Clearance

Abstract This paper studies the effects of cut-corner in the recess vaned casing treatment (RVCT) on the performance of a low-speed axial fan. The solid casing fan and fans with corner-cut RVCT have been simulated respectively. The numerical simulation shows that the introduction of the RVCT and the modification of RVCT cut-corner size bring about obvious changes in fan performance. The RVCT establishes a connection between the RVCT channel and the main flow, contributing to the extra flow circulation in the tip region and resulting in an efficiency penalty for each RVCT configuration. The cut-corner is not necessarily beneficial to the improvement of the stable operating range. With the increase of cut-corner size at the rear wall of RVCT, the improvement of stall margin firstly demonstrates a drop to −8.82% before jumping to over 60%. RVCTs with different cut-corner sizes play different roles in the flow interaction between RVCT channel and main flow, and the stall margin poses a positive relationship with the mass flow passing through RVCT. The size of the cut-corner is responsible for the flow field in RVCT. The RVCT with small cut-corner size functions as a larger blade tip clearance and results in a smaller stall margin than the solid casing fan. Therefore, the size of the cut-corner in RVCT should be large enough to dredge the flow blockage in the tip region and delay the origin of stall.

Part-Circumference Casing Treatment and the Effect on Compressor Stall

1989 ◽  
Author(s):  
N. A. Cumpsty
Keyword(s):  
Axial Compressor ◽  
Tip Clearance ◽  
Start Time ◽  
Stall Inception ◽  
Stall Margin ◽  
Tip Clearance Flow ◽  
Casing Treatment ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
Stall Margin Improvement

Results are presented and discussed from an axial compressor rotor operated with an axial skewed slot casing treatment over part of the circumference. The compressor was one for which stall was initiated in the tip region and for this type there is some potential for stall margin improvement with lower loss using this. The main significance of the experiments is, however, the possibility of looking at aspects of stall inception. Normally stall inception is a brief transient with an unknown start time and is difficult to study but with the partial casing treatment it was possible to make the untreated section operate continuously in such a way that it underwent the processes normally leading to stall. For a tip stalling rotor the experiments identify the annulus boundary layer as the crucial region of the flow and spillage of the tip-clearance flow forward of the blades as a process leading to the rapid build up of blockage prior to instability and stall.

Effects of Rotating Inlet Distortion on Multistage Compressor Stability

1996 ◽  
Vol 118 (2) ◽  
pp. 181-188 ◽  
Author(s):  
J. P. Longley ◽  
H. -W. Shin ◽  
R. E. Plumley ◽  
P. D. Silkowski ◽  
I. J. Day ◽  
...  
Keyword(s):  
Theoretical Model ◽  
Stability Margin ◽  
Forced Response ◽  
Single Peak ◽  
Rotor Speed ◽  
Stall Inception ◽  
Stall Margin ◽  
Inlet Distortion ◽  
Multistage Compressor ◽  
Two Peaks

In multispool engines, rotating stall in an upstream compressor will impose a rotating distortion on the downstream compressor, thereby affecting its stability margin. In this paper experiments are described in which this effect was simulated by a rotating screen upstream of several multistage low-speed compressors. The measurements are complemented by, and compared with, a theoretical model of multistage compressor response to speed and direction of rotation of an inlet distortion. For corotating distortions (i.e., distortions rotating in the same direction as rotor rotation), experiments show that the compressors exhibited significant loss in stability margin and that they could be divided into two groups according to their response. The first group exhibited a single peak in stall margin degradation when the distortion speed corresponded to roughly 50 percent of rotor speed. The second group showed two peaks in stall margin degradation corresponding to distortion speeds of approximately 25–35 percent and 70–75 percent of rotor speed. These new results demonstrate that multistage compressors can have more than a single resonant response. Detailed measurements suggest that the two types of behavior are linked to differences between the stall inception processes observed for the two groups of compressors and that a direct connection thus exists between the observed forced response and the unsteady flow phenomena at stall onset. For counterrotational distortions, all the compressors tested showed minimal loss of stability margin. The results imply that counterrotation of the fan and core compressor, or LP and HP compressors, could be a worthwhile design choice. Calculations based on the two-dimensional theoretical model show excellent agreement for the compressors, which had a single peak for stall margin degradation. We take this first-of-a-kind comparison as showing that the model, though simplified, captures the essential fluid dynamic features of the phenomena. Agreement is not good for compressors that had two peaks in the curve of stall margin shift versus distortion rotation speed. The discrepancy is attributed to the three-dimensional and short length scale nature of the stall inception process in these machines; this includes phenomena that have not yet been addressed in any model.

The Impact of Casing Groove Location on Stall Margin and Tip Clearance Flow in a Low-Speed Axial Compressor

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Du Juan ◽  
Li Jichao ◽  
Gao Lipeng ◽  
Lin Feng ◽  
Chen Jingyi
Keyword(s):  
Axial Compressor ◽  
Leading Edge ◽  
Suction Side ◽  
Tip Clearance ◽  
Tip Leakage Flow ◽  
Stall Inception ◽  
Stall Margin ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
The Impact

In this study, the impact of single grooves at different locations on compressor stability and tip clearance flow are numerically and experimentally investigated. Initially, the numerical stall margin improvement (SMI) curve is examined using experimental data. Then, the evolution of the interface between the tip leakage flow (TLF) and the incoming main flow (MF) in the prestall and stall inception processes for two typical grooves, i.e., the worst and the optimal grooves in terms of their SMI, are compared with the smooth casing. The results show two different interface behaviors throughout the throttling process. The compressor with the worst single groove casing first experiences a long-length-scale disturbance after the interface near the blade suction side spills in front of the rotor leading-edge plane, and then goes through spikes after the whole interface spills. With the smooth casing and the optimal single groove near midchord, the interface reaches the rotor leading edge at the last stable operating point and spikes appear once the whole interface spills over the rotor leading edge. A model that illustrates the spillage patterns of the interface for the two stall precursors is thus proposed accordingly and used to explain their effectiveness in terms of the SMI. At last, the relevance of these results to the preliminary selection of groove locations for multigroove casing treatments (CTs) is verified by test data and discussed.

scholarly journals Axial Flow Compressor Stability Enhancement: Circumferential T-Shape Grooves Performance Investigation

Aerospace ◽  
2021 ◽  
Vol 8 (1) ◽  
pp. 12
Author(s):  
Marco Porro ◽  
Richard Jefferson-Loveday ◽  
Ernesto Benini
Keyword(s):  
Vortex Breakdown ◽  
Pressure Ratio ◽  
Axial Flow ◽  
Suction Side ◽  
Treatment Technique ◽  
Tip Leakage Flow ◽  
Stall Inception ◽  
Stall Margin ◽  
Casing Treatment ◽  
Stall Margin Improvement

This work focuses its attention on possibilities to enhance the stability of an axial compressor using a casing treatment technique. Circumferential grooves machined into the case are considered and their performances evaluated using three-dimensional steady state computational simulations. The effects of rectangular and new T-shape grooves on NASA Rotor 37 performances are investigated, resolving in detail the flow field near the blade tip in order to understand the stall inception delay mechanism produced by the casing treatment. First, a validation of the computational model was carried out analysing a smooth wall case without grooves. The comparisons of the total pressure ratio, total temperature ratio and adiabatic efficiency profiles with experimental data highlighted the accuracy and validity of the model. Then, the results for a rectangular groove chosen as the baseline case demonstrated that the groove interacts with the tip leakage flow, weakening the vortex breakdown and reducing the separation at the blade suction side. These effects delay stall inception, improving compressor stability. New T-shape grooves were designed keeping the volume as a constant parameter and their performances were evaluated in terms of stall margin improvement and efficiency variation. All the configurations showed a common efficiency loss near the peak condition and some of them revealed a stall margin improvement with respect to the baseline. Due to their reduced depth, these new configurations are interesting because they enable the use of a thinner light-weight compressor case as is desirable in aerospace applications.

A Proposal for Passive Wall Treatment Applied in High Performance Axial Flow Compressors

2020 ◽  
Author(s):  
Rubén Bruno Díaz ◽  
Jesuino Takachi Tomita ◽  
Cleverson Bringhenti ◽  
Francisco Carlos Elizio de Paula ◽  
Luiz Henrique Lindquist Whitacker
Keyword(s):  
Stokes Equations ◽  
Axial Compressor ◽  
Axial Flow ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Smooth Wall ◽  
Tip Leakage Flow ◽  
Viscous Effects ◽  
Stall Margin ◽  
Tip Leakage

Abstract Numerical simulations were carried out with the purpose of investigating the effect of applying circumferential grooves at axial compressor casing passive wall treatment to enhance the stall margin and change the tip leakage flow. The tip leakage flow is pointed out as one of the main contributors to stall inception in axial compressors. Hence, it is of major importance to treat appropriately the flow in this region. Circumferential grooves have shown a good performance in enhancing the stall margin in previous researches by changing the flow path in the tip clearance region. In this work, a passive wall treatment with four circumferential grooves was applied in the transonic axial compressor NASA Rotor 37. Its effect on the axial compressor performance and the flow in the tip clearance region was analyzed and set against the results attained for the smooth wall case. A 2.63% increase in the operational range of the axial compressor running at 100%N, was achieved, when compared with the original smooth wall casing configuration. The grooves installed at compressor casing, causes an increase in the flow entropy generation due to the high viscous effects in this gap region, between the rotor tip surface and casing with grooves. These viscous effects cause a drop in the turbomachine efficiency. For the grooves configurations used in this work, an efficiency drop of 0.7% was observed, compared with the original smooth wall. All the simulations were performed based on 3D turbulent flow calculations using Reynolds Averaged Navier-Stokes equations, and the flow eddy viscosity was determined using the two-equation SST turbulence model. The details of the grooves geometrical dimensions and its implementation are described in the paper.

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