Evaluation of Compressor Blading With Blade End Slots and Full-Span Slots in a Highly Loaded Compressor Cascade

2019 ◽  
Author(s):  
Yumeng Tang ◽  
Yangwei Liu ◽  
Lipeng Lu
Keyword(s):  
Incidence Angle ◽  
Three Dimensional ◽  
Main Flow ◽  
The Self ◽  
Flow Structures ◽  
Two Dimensional ◽  
Compressor Cascade ◽  
Aero Engine ◽  
Compressor Performance ◽  
Highly Loaded

Abstract High loading design is a permanent pursuit in the field of the modern compressors to reduce the size and weight of the aero-engine. Blading with slots is a potential way to improve compressor performance. An innovative double-slot scheme was proposed and validated to control corner separation in a highly loaded compressor cascade in our previous studies. To evaluate the three-dimensional (3D) performance of blading with slots, the current research compares the performance of blading with full-span slots to that with blade end slots. First, the two-dimensional (2D) configuration performance is evaluated both for the datum and slotted profiles. The slotted configuration could effectively supress separation, especially under positive incidence conditions where the separation of the datum profile is large. Thus, two 3D blading forms, the full-span slots and the blade end slots (covering 20% of the span from the endwall), are compared within. Results show that blading with full-span slots could effectively reduce the loss under positive incidence angles, while blading with blade end slots could effectively reduce the loss above an incidence angle of −4°. The loss for the end slotted blade is lower than that of the full-span slotted blade under most incidence angles (within the range of 4°). The additional mixing loss of the jet and the main flow are caused by the full-span slots at the mid-span regions where the flow remains attached for the unslotted geometry. Blading with slots alters the flow structures and reorganises the flow in the blade end regions. The self-adaptive jets from the slot outlet push the accumulated low-momentum flow downstream and restrain its migration toward the mid-span, such that the uniform main flow in the blade mid-span region is enhanced.

Evaluation of Compressor Blading With Blade End Slots and Full-Span Slots in a Highly Loaded Compressor Cascade

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Yumeng Tang ◽  
Yangwei Liu ◽  
Lipeng Lu
Keyword(s):  
Incidence Angle ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Main Flow ◽  
The Self ◽  
Flow Structures ◽  
Compressor Cascade ◽  
Corner Separation ◽  
High Incidence ◽  
Highly Loaded

Abstract Blade end slots were proposed to control corner separation in a highly loaded compressor cascade in our previous studies. This study focuses on the evaluation of compressor blading with blade end slots and full-span slots. First, the two-dimensional configuration performance is evaluated both for the datum and slotted profiles. The slotted configuration could effectively suppress separation, especially under positive incidence conditions when the separation is large. Thus, two three-dimensional blading with full-span slots and blade end slots (20% span height from the endwall) are compared. Results show that blading with full-span slots could effectively reduce the loss and enlarge pressure rise under relative high incidence angles, while blading with blade end slots could effectively reduce the loss and enlarge pressure rise above an incidence angle of −4 deg. Blading with slots alters the flow structures and reorganizes the flow in the blade end regions. The self-adaptive jets from the slots reenergize the low-momentum flow downstream and restrain its migration toward the mid-span, so that the corner separation is reduced and the performance is enhanced. The loss for the end slotted blade is lower than that of the full-span slotted blade under incidence angles within 4 deg. This is because the additional mixing loss of the jet and the main flow are caused by the full-span slots at the mid-span regions where the flow remains attached for the blade end slots.

scholarly journals Forest Height Estimation Based on P-Band Pol-InSAR Modeling and Multi-Baseline Inversion

2020 ◽  
Vol 12 (8) ◽  
pp. 1319
Author(s):  
Xiaofan Sun ◽  
Bingnan Wang ◽  
Maosheng Xiang ◽  
Liangjiang Zhou ◽  
Shuai Jiang
Keyword(s):  
Standard Deviation ◽  
Vertical Structure ◽  
Incidence Angle ◽  
Three Dimensional ◽  
Solution Space ◽  
Model Complexity ◽  
Two Dimensional ◽  
Dimensional Parameter ◽  
Model Inversion ◽  
Forest Height

The Gaussian vertical backscatter (GVB) model has a pivotal role in describing the forest vertical structure more accurately, which is reflected by P-band polarimetric interferometric synthetic aperture radar (Pol-InSAR) with strong penetrability. The model uses a three-dimensional parameter space (forest height, Gaussian mean representing the strongest backscattered power elevation, and the corresponding standard deviation) to interpret the forest vertical structure. This paper establishes a two-dimensional GVB model by simplifying the three-dimensional one. Specifically, the two-dimensional GVB model includes the following three cases: the Gaussian mean is located at the bottom of the canopy, the Gaussian mean is located at the top of the canopy, as well as a constant volume profile. In the first two cases, only the forest height and the Gaussian standard deviation are variable. The above approximation operation generates a two-dimensional volume only coherence solution space on the complex plane. Based on the established two-dimensional GVB model, the three-baseline inversion is achieved without the null ground-to-volume ratio assumption. The proposed method improves the performance by 18.62% compared to the three-baseline Random Volume over Ground (RVoG) model inversion. In particular, in the area where the radar incidence angle is less than 0.6 rad, the proposed method improves the inversion accuracy by 34.71%. It suggests that the two-dimensional GVB model reduces the GVB model complexity while maintaining a strong description ability.

Compressor Performance 2D Modelling at Reverse Flow Conditions

2010 ◽  
Author(s):  
L. Gallar ◽  
I. Tzagarakis ◽  
V. Pachidis ◽  
R. Singh
Keyword(s):  
Experimental Data ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Engine Performance ◽  
Two Dimensional ◽  
Flow Conditions ◽  
Compressor Surge ◽  
Compressor Performance ◽  
Shaft Failure

After a shaft failure the compression system of a gas turbine is likely to surge due to the heavy vibrations induced on the engine after the breakage. Unlike at any other conditions of operation, compressor surge during a shaft over-speed event is regarded as desirable as it limits the air flow across the engine and hence the power available to accelerate the free turbine. It is for this reason that the proper prediction of the engine performance during a shaft over-speed event claims for an accurate modelling of the compressor operation at reverse flow conditions. The present study investigates the ability of the existent two dimensional algorithms to simulate the compressor performance in backflow conditions. Results for a three stage axial compressor at reverse flow were produced and compared against stage by stage experimental data published by Gamache. The research shows that due to the strong radial fluxes present over the blades, two dimensional approaches are inadequate to provide satisfactory results. Three dimensional effects and inaccuracies are accounted for by the introduction of a correction parameter that is a measure of the pressure loss across the blades. Such parameter is tailored for rotors and stators and enables the satisfactory agreement between calculations and experiments in a stage by stage basis. The paper concludes with the comparison of the numerical results with the experimental data supplied by Day on a four stage axial compressor.

Improving a one-dimensional centrifugal compressor performance prediction method

2005 ◽  
Vol 219 (8) ◽  
pp. 653-659 ◽  
Author(s):  
E Swain
Keyword(s):  
Centrifugal Compressor ◽  
Performance Prediction ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Prediction Method ◽  
Compressor Cascade ◽  
One Dimensional ◽  
Compressor Performance ◽  
Cfd Analyses

A one-dimensional centrifugal compressor performance prediction technique that has been available for some time is updated as a result of extracting the component performance from three-dimensional computational fluid dynamic (CFD) analyses. Confidence in the CFD results is provided by comparison of overall performance for one of the compressor examples. The extracted impeller characteristic is compared with the original impeller loss model, and this indicated that some improvement was desirable. The position of least impeller loss was determined using a traditional axial compressor cascade method, and suitable algebraic expressions were derived to match the CFD data. The merit of the approach lies with the relative ease that CFD component performance currently can be achieved and adjusting one-dimensional methods to agree with the CFD-derived models.

scholarly journals Effects of Surface Roughness, Freestream Turbulence, and Incidence Angle on the Performance of a 2-D Compressor Cascade

1990 ◽  
Author(s):  
W. C. Elrod ◽  
P. I. King ◽  
E. M. Poniatowski
Keyword(s):  
Surface Roughness ◽  
Total Pressure ◽  
Incidence Angle ◽  
Two Dimensional ◽  
Freestream Turbulence ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Linear Cascade ◽  
Pressure Loss Coefficient ◽  
Total Pressure Loss Coefficient

The effects of surface roughness, freestream turbulence, and incidence angle on the performance of a two-dimensional compressor cascade were investigated. The test section consisted of seven NACA 65-A506 airfoils arranged in a linear cascade. Four different surface roughness conditions were applied to the first 25 percent chord on the suction surface of each of the five middle blades in the cascade. Freestream turbulence levels of approximately one and seven percent were used. Incidence angles of −3, zero and +3 degrees were investigated. Of the three parameters tested, freestream turbulence exerted the largest influence on blade performance. The total pressure loss coefficient increased with increased roughness and was reduced for large turbulence. Changes in flow incidence had a lesser effect on the performance of the blade.

Experimental investigation on separation control by slot jet in highly loaded compressor cascade

2017 ◽  
Vol 232 (9) ◽  
pp. 1704-1714 ◽  
Author(s):  
Hu Jiaguo ◽  
Wang Rugen ◽  
Li Renkang ◽  
He Chen ◽  
Li Qiushi
Keyword(s):  
High Efficiency ◽  
Incidence Angle ◽  
Suction Side ◽  
Separation Control ◽  
Compressor Cascade ◽  
Turning Angle ◽  
Control Approach ◽  
Stable Operating ◽  
Operating Margin ◽  
Highly Loaded

Separation control in compressor cascade is very significant for modern high efficiency compressor. This paper introduces a separation control approach using self-supplied jet in a highly loaded cascade. A novel arc slot is created into the cascade at the full span range, which connects the flow fields between the pressure and suction side. Because of the pressure difference, the slot enables to induce the jet flow into the suction side separation. Experiments are conducted to evaluate the separation control effects and preliminarily study the mechanism. The results show that the slot cascade acquires more ordered outflow by reducing the suction side separation and suppressing the complex vortices. Due to the great reduction of the separation, the total loss significantly decreases by 21.9% and the flow turning angle increases by 2.1° in average. According to the improvements of the cascade performance, the stable operating margin of the highly loaded cascade is greatly improved at least 3° in terms of the incidence angle.

Three-dimensional instabilities over a rectangular open cavity: from linear stability analysis to experimentation

2014 ◽  
Vol 748 ◽  
pp. 189-220 ◽  
Author(s):  
J. de Vicente ◽  
J. Basley ◽  
F. Meseguer-Garrido ◽  
J. Soria ◽  
V. Theofilis
Keyword(s):  
Three Dimensional ◽  
Reynolds Numbers ◽  
Linear Analysis ◽  
Main Flow ◽  
Open Cavity ◽  
Flow Structures ◽  
Cavity Flows ◽  
Final State ◽  
Wave Properties ◽  
Final Expression

AbstractThree-dimensional instabilities arising in open cavity flows are responsible for complex broad-banded dynamics. Existing studies either focus on theoretical properties of ideal simplified flows or observe the final state of experimental flows. This paper aims to establish a connection between the onset of the centrifugal instabilities and their final expression within the fully saturated flow. To that end, a linear three-dimensional modal instability analysis of steady two-dimensional states developing in an open cavity of aspect ratio $L/D=2$ (length over depth) is conducted. This analysis is performed together with an experimental study in the same geometry adding spanwise endwalls. Two different Reynolds numbers are investigated through spectral analyses and modal decomposition. The physics of the flow is thoroughly described exploiting the strengths of each methodology. The main flow structures are identified and salient space and time scales are characterised. Results indicate that the structures obtained from linear analysis are mainly consistent with the fully saturated experimental flow. The analysis also brings to light the selection and alteration of certain wave properties, which could be caused by nonlinearities or the change of spanwise boundary conditions.

On Three and Two-Dimensional Disturbances of Pipe Flow

1960 ◽  
Vol 27 (3) ◽  
pp. 381-389 ◽  
Author(s):  
Kurt Spielberg ◽  
Hans Timan
Keyword(s):  
Order Differential Equation ◽  
Three Dimensional ◽  
Circular Cross Section ◽  
Main Flow ◽  
Two Dimensional ◽  
Straight Pipe ◽  
Special Cases ◽  
Set Up ◽  
The Stability ◽  
The Given

A system of ordinary, coupled differential equations is set up for three-dimensional disturbances of Poiseuille flow in a straight pipe of circular cross section. The commonly treated equations are shown to be special cases arising from particular assumptions. It is shown that in the nonviscous, and therefore also in the general case, there exists, in contrast to the analogous problem in Cartesian co-ordinates, no transformation reducing the given problem to a two-dimensional one. A fourth-order differential equation is derived for disturbances independent of the direction of the main flow. The solutions, which are obtained, show that those two-dimensional disturbances, termed cross disturbances, decay with time and do therefore not disturb the stability of the main flow. Explicit expressions for the cross disturbances are obtained and a discussion of their nature is given.

scholarly journals Lagrangian Coherent Structure Analysis of Terminal Winds: Three-Dimensionality, Intramodel Variations, and Flight Analyses

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Brent Knutson ◽  
Wenbo Tang ◽  
Pak Wai Chan
Keyword(s):  
Coherent Structures ◽  
Three Dimensional ◽  
Light Detection And Ranging ◽  
Flow Structures ◽  
Lidar Data ◽  
Two Dimensional ◽  
Lagrangian Coherent Structure ◽  
Flight Data ◽  
Velocity Information ◽  
Hong Kong International Airport

We present a study of three-dimensional Lagrangian coherent structures (LCS) near the Hong Kong International Airport and relate to previous developments of two-dimensional (2D) LCS analyses. The LCS are contrasted among three independent models and against 2D coherent Doppler light detection and ranging (LIDAR) data. Addition of the velocity information perpendicular to the LIDAR scanning cone helps solidify flow structures inferred from previous studies; contrast among models reveals the intramodel variability; and comparison with flight data evaluates the performance among models in terms of Lagrangian analyses. We find that, while the three models and the LIDAR do recover similar features of the windshear experienced by a landing aircraft (along the landing trajectory), their Lagrangian signatures over the entire domain are quite different—a portion of each numerical model captures certain features resembling those LCS extracted from independent 2D LIDAR analyses based on observations.

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