High-Speed Centrifugal Compressor Aeromechanics - Impeller Unsteady Aerodynamics

Ramakrishnan, Kishore Ranganath; Lawless, Patrick B.; Fleeter, Sanford

doi:10.2514/6.2007-5020

Cited by 3 publications

(13 citation statements)

References 8 publications

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“…15b contributes to the increased efficiency of the ABT tandem impeller. These observations of reversed tip clearance flow phenomena near the surge point agree well with those simulation and measurement findings for the centrifugal impeller with splitter blades [25,26]. The contour plots of the gap flowfield are also investigated.…”

Section: Optimization Results and Discussionsupporting

confidence: 84%

Design Optimization and Experimental Study of Tandem Impeller for Centrifugal Compressor

Zhang

2014

Journal of Propulsion and Power

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Although significant advances have been made in tandem-blade technology for axial compressors, few efforts were devoted to its application in centrifugal compressors. Based on detailed computational fluid dynamics simulations and sensitivity analysis, multiobjective design optimization is conducted for a tandem impeller. An optimized tandem impeller, for which the objectives are all better than those of the baseline, is fabricated and tested on a high-speed centrifugal compressor rig. The numerical results show that the baseline tandem impeller has more uniform discharge flow but lower efficiency than the corresponding splitter impeller. The geometries of the inducer blade profile and inducer-exducer gap are found to have the greatest impact on the tandem impeller efficiencies. By optimization, the tandem impeller efficiency can be increased through reduced curvature of the blade profile at the inducer hub, S-shaped blade angle distribution at the inducer tip, and increased blade angle at the exducer tip near the leading edge. The measured performance of the centrifugal compressor with the optimized tandem impeller agrees well with the computational fluid dynamics calculations, and the compressor peak efficiency is 0.796 at the design speed (45,000 rpm). Nomenclature C p = total pressure loss coefficient (C p P t;3 − P t ∕P t;3 − P s;3 , three-diffuser inlet) H 11 ∼ H 14 = Bézier control points at the inducer hub side H 21 ∼ H 24 = Bézier control points at the exducer hub side m = meridional length, mm _ m = mass flow rate, kg∕s N = shaft speed, rpm P = pressure, Pa PS = pressure surface R = radius, mm SS = suction surface T = temperature, K T 11 ∼ T 14 = Bézier control points of the blade angle distribution at the inducer tip T 21 ∼ T 25 = Bézier control points of the blade angle distribution at the exducer tip V 1 ∼ V 5 = design variables y = nondimensional distance of the first node from the wall α = absolute flow velocity angle, deg β = blade angle from meridional plane, deg ε = total to total pressure ratio η = total to total polytropic efficiency θ = blade tangential coordinate, deg Subscripts des = design point value in = computational inlet section s = static value t = total value

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Section: Optimization Results and Discussionsupporting

confidence: 84%

Design Optimization and Experimental Study of Tandem Impeller for Centrifugal Compressor

Zhang

2014

Journal of Propulsion and Power

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“…The excitation frequency is proportional to the engine speed and the spatial nature of the excitation is in the form of a traveling wave [17,39]. The unsteady force generated from the interaction is mainly acting near the trailing edges of blades [25,27]. According to the Fourier analysis of the static pressure distribution at the impeller exit, the first harmonic pressure is dominant and the higher order pressures attenuate rapidly [40].…”

Section: Simplified Diffuser-induced Engine Order Excitationmentioning

confidence: 99%

“…According to the Fourier analysis of the static pressure distribution at the impeller exit, the first harmonic pressure is dominant and the higher order pressures attenuate rapidly [40]. Thus, we can only use the first harmonic pressure in forced response calculation as a kind of simplification [27,41]. Unlike the conventionally designed impellers, the amplitude of the aerodynamic force acting on the main blades is usually higher than that on the splitter blades [25][26][27].…”

Section: Simplified Diffuser-induced Engine Order Excitationmentioning

confidence: 99%

“…Thus, we can only use the first harmonic pressure in forced response calculation as a kind of simplification [27,41]. Unlike the conventionally designed impellers, the amplitude of the aerodynamic force acting on the main blades is usually higher than that on the splitter blades [25][26][27].…”

Section: Simplified Diffuser-induced Engine Order Excitationmentioning

confidence: 99%

“…In terms of aerodynmic forcing, the spatial harmonic contents of the unsteady pressure distribution at the impeller exit for impellers with splitter blades are different from those for conventionally desinged ones [25]. Besides, the load amplitudes of the main and the splitter blades are usually different too [25][26][27].…”

Section: Introductionmentioning

confidence: 99%

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Investigation of the Influence of Splitter Blades on the Resonance Conditions of Impellers

Liu

Cheng

2019

Applied Sciences

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The conventional resonance conditions are derived based on the conventionally designed impellers without splitter blades. This paper proposes the resonance conditions for impellers under the excitation from the impeller–diffuser interaction with attention paid on the influence of splitter blades. A lumped parameter model is established and the modal analysis is carried out. The blade-based representative modal vector (RMV) is defined. The influence of splitter blades on the impeller’s traits of modes is investigated by analyzing the spatial harmonic contents of the RMV. Then, given the specific form of the diffuser-induced engine order excitation acting on the main and splitter blades, the resonance conditions are derived. Tuned and mistuned cases are provided for a practical impeller. The resonance conditions are verified by harmonic response calculations. The applications of the proposed resonance conditions in resonance identification and hazard evaluation of different excitations are given. The differences between the proposed resonance conditions and the conventional ones are discussed. The research indicates that even the RMV of the tuned impeller contains two harmonic components due to the existence of splitter blades. When the excitation frequency equals the natural frequency of the impeller and the excitation order matches with either harmonic index of the two harmonics, the resonance occurs. The results of case studies show that the harmfulness of various engine orders of excitation can be exactly evaluated by the joint use of the spatial harmonic contents analysis result and the proposed resonance conditions; however, analyzing based on the conventional resonance conditions may lead to the misjudgment of the harmfulness of the excitations.

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Effect of Vaned Diffuser on a Modified Turbocharger Centrifugal Compressor Performance

Jawad

Abdullah²,

Zulkifli³

et al. 2014

AMM

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A numerical study that was made in a three-dimensional flow, carried out in a modified centrifugal compressor, having vaned diffuser stage, used as an automotive turbo charger. In order to study the influence of vaned diffuser meridional outlet section with a different width ratio of the modified centrifugal compressor. Moreover, the performance of the centrifugal compressor was dependent on the proper matching between the compressor impeller along the vaned diffuser. The aerodynamic characteristics were compared under different meridional width ratio. In addition, the velocity vectors in diffuser flow passages, and the secondary flow in cross-section near the outlet of diffuser were analysed in detail under different meridional width ratio. Another aim of this research was to study and simulate the effect of vaned diffuser on the performance of a centrifugal compressor. The simulation was undertaken using commercial software so-called ANSYS CFX, to predict numerically the performance charachteristics. The results were generated from CFD and were analysed for better understanding of the fluid flow through centrifugal compressor stage and as a result of the minimum width ratio the flow in diffuser passage tends to be uniformity. Moreover, the backflow and vortex near the pressure surface disappear, and the vortex and detachment near the suction surface decrease. Conclusively, it was observed that the efficiency was increased and both the total pressure ratio and static pressure for minimum width ratio are increased.

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High-Speed Centrifugal Compressor Aeromechanics - Impeller Unsteady Aerodynamics

Cited by 3 publications

References 8 publications

Design Optimization and Experimental Study of Tandem Impeller for Centrifugal Compressor

Design Optimization and Experimental Study of Tandem Impeller for Centrifugal Compressor

Investigation of the Influence of Splitter Blades on the Resonance Conditions of Impellers

Effect of Vaned Diffuser on a Modified Turbocharger Centrifugal Compressor Performance

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