Reduction of Unsteady Blade Loading by Beneficial Use of Vortical and Potential Disturbances in an Axial Compressor With Rotor Clocking

Hsu, S. T.; Wo, Andrew M.

doi:10.1115/97-gt-086

Cited by 23 publications

(23 citation statements)

References 20 publications

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“…The blades were designed using controlled diffusion concept of Hobbs and Weingold (1984). The measured static-to-static pressure rise characteristic (see Hsu and Wo, 1998) is believed to be representative of highly loaded blade of modem design. If not explicitly stated, results reported are taken with the compressor at near-design loading (C)= 0.60).…”

Section: Compressor Rigmentioning

confidence: 99%

“…Chung and Wo (1997) used both Navier-Stokes and panel codes to split the disturbances between blade rows into vortical and potential contributions and Wo et al (1997) provided details on decomposition of forced response. Hsu and Wo (1998) recently showed that if the blades are clocked properly the potential disturbance from the second rotor row can substantially reduced the upstream stator response caused by wakes from the first rotor blades. This result emphasizes the importance of concrete consideration of blade row interaction.…”

Section: Introductionmentioning

confidence: 99%

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Wake Vorticity Decay and Blade Response in an Axial Compressor With Varying Axial Gap

Chung

Chang

et al. 1999

Volume 4: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation;

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This paper addresses the decay of rotor wake vorticity for a rotor/stator axial compressor, with the axial gap between blade rows being 10, 20 and 30 percent chord, and at both design and high loading levels. Experiments were conducted in a large-scale, low-speed axial compressor. Navier-Stokes calculations were also executed. Both data and Navier-Stokes results reveal that the decay of rotor wake vorticity increases substantially as the axial gap decreases; the decay for 10 percent gap is about twice that of 30 percent. Increased time-mean blade loading causes the vorticity decay to also increase, with this effect more pronounced for large axial gap than small. At the stator inlet mid-pitch location, the wake maximum vorticity for 10 and 30 percent chord gap cases being nearly the same (differ by 3.8%) at design loading. The corresponding stator unsteady force agrees within 5.2%. Variation of vorticity decay with axial gap is directly linked to the change in potential disturbance by the downstream stator on the rotor wake due to the change in gap spacing. This suggests that the stator potential disturbance causes the upstream rotor wake to decay at an increased rate which, in turns, results in a lowered level of stator response compared to that without this stator/wake interaction effect. Thus, in this context, blade row interaction is considered beneficial.

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Section: Compressor Rigmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Wake Vorticity Decay and Blade Response in an Axial Compressor With Varying Axial Gap

Chung

Chang

et al. 1999

Volume 4: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation;

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“…Saren et al (1994Saren et al ( ,1995Saren et al ( ,1997 have used theoretical, computational and experimental techniques to show that airfoil clocking can be used to increase performance and reduce unsteady aerodynamic loads on airfoils. Hsu and Wo (1997) experimentally demonstrated that rotor clocking can be used to reduce the unsteady loads experienced by downstream blade rows, while in another experimental investigation Walker et al (1997) studied the effects of inlet guide vane clocking on the boundary layer quantities and losses of a downstream stator blade row. Barankiewicz and Hathaway (1997) also performed stator clocking experiments, but their data showed only a 0.2\% performance change due to clocking.…”

Section: Introductionmentioning

confidence: 99%

Physics Of Airfoil Clocking In A High-Speed Axial Compressor

Dorney¹,

Sharma²,

Gundy-Burlet³

1998

International Journal of Turbo and Jet Engines

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Axial compressors have inherently unsteady flow fields because of relative motion between rotor and stator airfoils. This relative motion leads to viscous and in viscid (potential) interactions between blade rows. As the number of stages increases in a turbomachine, the buildup of converted wakes can lead to progressively more complex wake/wake and wake/airfoil interactions. Variations in the relative circumferential positions of stators or rotors can change these interactions, leading to different unsteady forcing functions on airfoils and different compressor efficiencies. In addition, as the Mach number increases the interaction between blade rows can be intensified due to potential effects. In the current study an unsteady, quasi-three-dimensional Navier-Stokes analysis has been used to investigate the unsteady aerodynamics of stator clocking in a 1-1/2 stage compressor, typical of back stages used in high-pressure compressors of advanced commercial jet engines. The effects of turbulence have been modeled with both algebraic and two-equation models. The results presented include steady and unsteady surface pressures, efficiencies, boundary layer quantities and turbulence quantities.The main contribution of the current work has been to show that airfoil clocking can produce significant performance variations at the Mach numbers associated with an engine operating environment In addition, the growth of turbulence has been quantified to aid in the development of models for the multi-stage steady analyses used in design systems. The effects of airfoil clocking (or indexing) on turbine performance have been investigated byHuber et al. (1995), Griffin et cd. (1995) and Dorney and Sharma (1996). The studies showed changes in efficiency on the order of 0.5\% as the stators were

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“…η,=· ι-W 7 ;., (2) The efficiency variation according to clocking positions is shown in Figure 6. The efficiency was obtained using mass-averaged values of time-averaged total pressure and total temperature, and it is defined as the follows.…”

Section: Efficiency Variationsmentioning

confidence: 99%

Relation of Clocking Effect and Secondary Flow in a 1.5 Stage Axial Turbine

Choi¹,

Park²,

Chung³

et al. 2009

International Journal of Turbo and Jet Engines

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A three-dimensional unsteady flow simulation was conducted to investigate the relation of clocking effect and secondary flow in a 1.5 stage axial turbine. Six relative positions of two stator rows were investigated by positioning the second stator being clocked in a step of 1/6 pitch. The relative efficiency benefit of about 1% was obtained depending on clocking positions. However, internal flows had some different features from the previous study at maximum and minimum efficiency positions, since the first stator wake was mixed out with the rotor wake before arriving at the leading edge of the second stator at mid-span. Instead of the first stator wake, it was found that the secondary flow plays an important role to the efficiency variation at each clocking position. The time-averaged local efficiency along the span at maximum efficiency was more uniform than that at minimum efficiency. That is, the span-wise efficiency distribution at minimum efficiency has larger values at mid-span but smaller values near the hub and casing compared with the case at maximum efficiency. This spanwise efficiency distribution could be also explained by secondary flow behavior in an axial turbine.

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Reduction of Unsteady Blade Loading by Beneficial Use of Vortical and Potential Disturbances in an Axial Compressor With Rotor Clocking

Cited by 23 publications

References 20 publications

Wake Vorticity Decay and Blade Response in an Axial Compressor With Varying Axial Gap

Wake Vorticity Decay and Blade Response in an Axial Compressor With Varying Axial Gap

Physics Of Airfoil Clocking In A High-Speed Axial Compressor

Relation of Clocking Effect and Secondary Flow in a 1.5 Stage Axial Turbine

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