Using tandem blades to break loading limit of highly loaded axial compressors

The clearance size of cantilevered stators affects the performance and stability of axial compressors significantly. Numerical calculations were carried out using the commercial software FINE/Turbo for a 2.5-stage highly loaded transonic axial compressor, which is of cantilevered stator for the first stage, at varying hub clearance sizes. The aim of this work is to improve understanding of the impact mechanism of hub clearance on the performance and the flow field in high flow turning conditions. The performance of the front stage and the compressor with different hub clearance sizes of the first stator has been analyzed firstly. Results show that the efficiency decreases as clearance size varies from 0 to 3% of hub chordlength, but the operating range has been extended. For the first stage, the efficiency decreases about 0.5% and the stall margin is extended. The following analysis of detailed flow field in the first stator shows that the clearance leakage flow and elimination of hub corner separation is responsible for the increasing loss and stall margin extending respectively. The effects of hub clearance on the downstream rotor have been discussed lastly. It indicates that the loss of the rotor increases and the flow deteriorates due to increasing of clearance size and hence the leakage mass flow rate, which mainly results from the interaction of upstream leakage flow with the passage flow near pressure surface. The affected region of rotor passage flow field expands in spanwise and streamwise direction as clearance size grows. The hub clearance leakage flow moves upward in span as it flows toward downstream.

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Effects of Reynolds Number on Performance of Highly Loaded Multi-Stage Axial Compressors

10.1115/1.0002644v ◽

2021 ◽

Author(s):

Xiaoshi Zhang

Keyword(s):

Reynolds Number ◽

Axial Compressors ◽

Multi Stage ◽

Highly Loaded

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Effect of Backward Sweep on Aerodynamic Performance of a 1.5-Stage Highly Loaded Axial Compressor

Volume 2A: Turbomachinery ◽

10.1115/gt2020-14262 ◽

2020 ◽

Author(s):

Song Huang ◽

Chuangxin Zhou ◽

Chengwu Yang ◽

Shengfeng Zhao ◽

Mingyang Wang ◽

...

Keyword(s):

Total Pressure ◽

Pressure Ratio ◽

Axial Compressor ◽

Aerodynamic Performance ◽

Blade Loading ◽

Stall Margin ◽

Axial Compressors ◽

Design Speed ◽

Total Pressure Ratio ◽

Highly Loaded

Abstract As a degree of freedom in the three-dimensional blade design of axial compressors, the sweep technique significantly affects the aerodynamic performance of axial compressors. In this paper, the effects of backward sweep rotor configurations on the aerodynamic performance of a 1.5-stage highly loaded axial compressor at different rotational design speeds are studied by numerical simulation. The aim of this work is to improve understanding of the flow mechanism of backward sweep on the aerodynamic performance of a highly loaded axial compressor. A commercial CFD package is employed for flow simulations and analysis. The study found that at the design rotational speed, compared with baseline, backward sweep rotor configurations reduce the blade loading near the leading edge but slightly increases the blade loading near the trailing edge in the hub region. As the degree of backward sweep increases, the stall margin of the 1.5-stage axial compressor increase first and then decrease. Among different backward sweep rotor configurations, the 10% backward sweep rotor configuration has the highest stall margin, which is about 2.5% higher than that of baseline. This is due to the change of downstream stator incidence, which improves flow capacity near the hub region. At 80% rotational design speed, backward sweep rotor configurations improve stall margin and total pressure ratio of the compressor. It’s mainly due to the decreases of the rotor incidence near the middle span, which results in the decreases of separation on the suction surface. At 60% rotational design speed, detached shock disappears. Backward sweep rotor configurations deteriorate stall margin of the compressor, but increase total pressure ratio and adiabatic efficiency when the flow rate is lower than that at peak efficiency condition. Therefore, it’s necessary to consider the flow field structure of axial compressors at whole operating conditions in the design process and use the design freedom of sweep to improve the aerodynamic performance.

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Maximum Loading Capacity of Tandem Blades in Axial Compressors

Volume 2C: Turbomachinery ◽

10.1115/gt2018-76770 ◽

2018 ◽

Author(s):

Baojie Liu ◽

Du Fu ◽

Xianjun Yu

Keyword(s):

Axial Compressor ◽

Pressure Rise ◽

Design Tool ◽

Stable Operation ◽

Loading Capacity ◽

Axial Compressors ◽

Maximum Loading ◽

Work Input ◽

Dimensional Parameters ◽

Highly Loaded

Tandem blades are widely reported to be superior to a single-blade configuration under the aerodynamic circumstance with a large flow turning in a stator or a high work input in a rotor. Aiming at the design of a highly loaded rear stage of a high pressure compressor with the advanced concept, the maximum loading capacity of a tandem-blade configuration, which is rarely described in open literature, is fundamentally necessary to be explicit in order to determine a stable operation range. A diffuser analogy is carefully carried out between the tandem-blade geometry and the diffuser passage using a reliable and robust numerical method. The analysis approach to effectively predicting the maximum static pressure rise is verified by the limited results of computational fluid dynamics (CFD) and experiments. In addition, the maximum loading capacity of the tandem-blade configuration is compared with that of the single-blade configuration to define a more favorable design range of meanline parameters. The results indicate that the tandem blade outperforms the conventional blade in a specific design space and the approach can be a potential design tool to guide the selection of one-dimensional parameters of tandem blades in a highly loaded axial compressor.

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The Design of Highly Loaded Axial Compressors

Journal of Turbomachinery ◽

10.1115/1.4001226 ◽

2010 ◽

Vol 133 (3) ◽

Cited By ~ 21

Author(s):

Tony Dickens ◽

Ivor Day

Keyword(s):

Pressure Rise ◽

High Loading ◽

Axial Compressors ◽

Pressure Surface ◽

High Stage ◽

Computational Fluid Dynamics Cfd ◽

Cycle Efficiency ◽

Stage Efficiency ◽

Highly Loaded ◽

Additional Loss

Increasing compressor pressure ratios (thereby gaining a benefit in cycle efficiency), or reducing the number of stages (to reduce weight, cost, etc.), will require an increase in pressure rise per stage. One method of increasing the pressure rise per stage is by increasing the stage loading coefficient, and it is this topic, which forms the focus of the present paper. In the past, a great deal of effort has been expended in trying to design highly loaded blade rows. Most of this work has focused on optimizing a particular design, rather than looking at the fundamental problems associated with high loading. This paper looks at the flow physics behind the problem, makes proposals for a new design strategy, and explains sources of additional loss specific to highly loaded designs. Detailed experimental measurements of three highly loaded stages (Δh0/U2≈0.65) have been used to validate a computational fluid dynamics (CFD) code. The calibrated CFD has then been used to show that, as the stage loading is increased, the flow in the stator passages breaks down first. This happens via a large corner separation, which significantly impairs the stage efficiency. The stator can be relieved by increasing stage reaction, thus shifting the burden to the rotor. Fortunately, the CFD calculations show that the rotor is generally more tolerant of high loading than the stator. Thus, when stage loading is increased, it is necessary to increase the reaction to achieve the optimum efficiency. However, the design exercise using the calibrated CFD also shows that the stage efficiency is inevitably reduced as the stage loading is increased (in agreement with the experimental results). In the second part of the paper, the role that the profile loss plays in the reduction in efficiency at high stage loading is considered. A simple generic velocity distribution is developed from first principles to demonstrate the hitherto neglected importance of the pressure surface losses in highly loaded compressors.

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The Design of Highly Loaded Axial Compressors

Volume 7: Turbomachinery, Parts A and B ◽

10.1115/gt2009-59291 ◽

2009 ◽

Cited By ~ 2

Author(s):

Tony Dickens ◽

Ivor Day

Keyword(s):

Pressure Rise ◽

High Loading ◽

Axial Compressors ◽

Pressure Surface ◽

High Stage ◽

Cycle Efficiency ◽

Profile Loss ◽

Stage Efficiency ◽

Highly Loaded ◽

Additional Loss

Increasing compressor pressure ratios (thereby gaining a benefit in cycle efficiency), or reducing the number of stages (to reduce weight, cost, etc.), will require an increase in pressure rise per stage. One method of increasing the pressure rise per stage is by increasing the stage-loading coefficient and it is this topic which forms the focus of the present paper. In the past, a great deal of effort has been expended in trying to design highly loaded blade rows. Most of this work has focused on optimizing a particular design rather than looking at the fundamental problems associated with high loading. This paper looks at the flow physics behind the problem, makes proposals for a new design strategy and explains sources of additional loss specific to highly loaded designs. Detailed experimental measurements of three highly loaded stages (Δh0/U2 ≈ 0.65) have been used to validate a CFD code. The calibrated CFD has then been used to show that as the stage loading is increased the flow in the stator passages breaks down first. This happens via a large corner separation which significantly impairs the stage efficiency. The stator can be relieved by increasing stage reaction, thus shifting the burden to the rotor. Fortunately, the CFD calculations show that the rotor is generally more tolerant of high loading than the stator. Thus, when stage loading is increased, it is necessary to increase the reaction to achieve the optimum efficiency. However, the design exercise using the calibrated CFD also shows that the stage efficiency is inevitably reduced as the stage loading is increased (in agreement with the experimental results). In the second part of the paper, the role profile loss plays in the reduction in efficiency at high stage loading is considered. A simple generic velocity distribution is developed from first principles to demonstrate the hitherto neglected importance of the pressure surface losses in highly loaded compressors.

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Numerical Investigation of Passive Flow Control Using Wavy Blades in a Highly-Loaded Compressor Cascade

Volume 2A: Turbomachinery ◽

10.1115/gt2018-76147 ◽

2018 ◽

Cited By ~ 1

Author(s):

Bo Wang ◽

Yanhui Wu ◽

Kai Liu

Keyword(s):

Numerical Investigation ◽

Flow Structure ◽

Cross Flow ◽

Leading Edge ◽

Control Flow ◽

Streamwise Vortices ◽

Compressor Cascade ◽

Control Effect ◽

Suction Surface ◽

Highly Loaded

Driven by the need to control flow separations in highly loaded compressors, a numerical investigation is carried out to study the control effect of wavy blades in a linear compressor cascade. Two types of wavy blades are studied with wavy blade-A having a sinusoidal leading edge, while wavy blade-B having pitchwise sinusoidal variation in the stacking line. The influence of wavy blades on the cascade performance is evaluated at incidences from −1° to +9°. For the wavy blade-A with suitable waviness parameters, the cascade diffusion capacity is enhanced accompanied by the loss reduction under high incidence conditions where 2D separation is the dominant flow structure on the suction surface of the unmodified blade. For well-designed wavy blade-B, the improvement of cascade performance is achieved under low incidence conditions where 3D corner separation is the dominant flow structure on the suction surface of the baseline blade. The influence of waviness parameters on the control effect is also discussed by comparing the performance of cascades with different wavy blade configurations. Detailed analysis of the predicted flow field shows that both the wavy blade-A and wavy blade-B have capacity to control flow separation in the cascade but their control mechanism are different. For wavy blade-A, the wavy leading edge results in the formation of counter-rotating streamwise vortices downstream of trough. These streamwise vortices can not only enhance momentum exchange between the outer flow and blade boundary layer, but also act as the suction surface fence to hamper the upwash of low momentum fluid driven by cross flow. For wavy blade-B, the wavy surface on the blade leads to a reduction of the cross flow upwash by influencing the spanwise distribution of the suction surface static pressure and guiding the upwash flow.

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The Dispersion of Gas Black and the Physical Properties of Rubber Mixtures

Rubber Chemistry and Technology ◽

10.5254/1.3547475 ◽

1931 ◽

Vol 4 (1) ◽

pp. 29-38 ◽

Cited By ~ 1

Author(s):

E. A. Grenquist

Keyword(s):

Tensile Strength ◽

Physical Properties ◽

Good Method ◽

Theoretical Possibility ◽

Homogeneous Surface ◽

Degree Of Dispersion ◽

Highly Loaded

Abstract Many rubber technologists have already shown the importance of the dispersion of pigments in order to obtain the maxima physical properties of rubber mixtures. In a recent publication on the physical properties of gas black Carson and Sebrell state that they do not know of any article based on tests which deals with the relations between the dispersion of gas black and the properties of corresponding mixtures. Wiegand has already shown, in discussing mixtures highly loaded with gas black, that an incomplete dispersion of the pigments is no longer possible if the consistency of rubber falls below a definite value. He states that the lustre on the surface of a sample such as is used to determine tensile strength is a good method of estimating the degree of dispersion. Hauser upholds the idea that certain pigments attain a maximum dispersion during milling. In two preceding communications I studied the distribution of gas black in vulcanized and unvulcanized mixtures. I showed that changes in dispersion occur during milling as well as during vulcanization, and I discussed the theoretical possibility of obtaining the maximum dispersion and reënforcement. On the contrary, I am not concerned in these articles with the actual physical properties of the mixtures examined. In the present work, I wish to attempt to establish the relations between the dispersion of gas black and certain physical properties of rubber mixtures, whether vulcanized or not. The dispersion was determined by means of the microscope on freshly cut surfaces of mixtures vulcanized and unvulcanized, using a Leitz vertical illuminator and a Zeiss arc lamp as the source of light. Magnified about 300 times, the aggregates of gas black appear like a non-homogeneous black mass, while on the smoother and more homogeneous surface of the rubber the reflection is so increased that the field remains lighted.

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