A study on unsteady aerodynamic excitation forces on radial turbine blade due to rotor-stator interaction

Sato, Wataru; Yamagata, Akihiro; Hattori, Hiroaki

doi:10.1533/978081000342.389

Cited by 8 publications

(6 citation statements)

References 4 publications

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“…At open conditions, there is no presence of shock waves but the blade loading is less, however the nozzle clearance contributes to the formation of a strong shock wave on the mid-chord of the impeller SS producing a highly disturbed flow field. Furthermore, as stated by to Sato et al 14 at closed vane position, the effects of shock waves and nozzle clearance flows on excitation force are intensified with increasing pressure ratio and the Mach number, while at opened vane position the excitation force is independent of the pressure ratio but depends on the density at the rotor inlet and the choked flows occurred near the rotor TE. In a turbine with the stator vanes closed and high inlet pressure, Zhao et al 15 found that two shock waves appears, the first shock wave is generated near the throat of nozzle and it is followed by the second shock wave on the SS of the vane near the TE, existing a transonic region between them.…”

Section: Introductionmentioning

confidence: 78%

“…The flow pattern in the stator and rotor passage of a variable geometry turbine operating at different speeds and pressure ratio is presented and gives first approximation of the internal phenomena before carrying out complex experimental tests in a turbocharger gas stand. Furthermore, the results of this paper can contribute to the future development of one-dimensional modeling to estimate excitation forces in a fast and precise way during the turbine design process 14 and also to elaborate extrapolation models of the turbine map at high expansion ratio as the models presented by Serrano et al, 35 Romagnoli and Martinez-Botas 36 or Meroni et al, 37 due to the difficulty to obtain measurements under these off-design conditions. These kind of models can be connected directly to the one-dimensional whole engine models to achieve an optimum engine-turbocharger matching and engine performance.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Development of Choked Flow in Variable Nozzle Radial Turbines

Tiseira

García-Cuevas

Inhestern

et al. 2021

International Journal of Engine Research

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In commonly applied one-dimensional choking models for radial turbines, choked flow is assumed to appear in the geometrical throat of each stator and rotor. Coupled and complex three-dimensional effects are not considered. In order to analyze the internal aerodynamic in a radial turbine at off design conditions and before carrying out experimental tests, which in the case of automotive turbocharger are limited by their compact size, computational fluid dynamics (CFD) simulations stand out as a useful tool. This paper presents the study of a variable geometry turbine (VGT) of a commercial turbocharger at off design conditions reaching choked flow, analyzing the presence of this limiting conditions in the stator and rotor under different operation points and VGT positions. Reynolds-averaged Navier-Stokes (RANS) and unsteady RANS simulation have been performed to obtain the flow structures in stator and rotor. The results reveal that the choked effective area mostly depends on the stator vane position and pressure ratio. For the closed VGT position a standing shock wave appears on the stator suction side and expands through the vaneless space. For the opened VGT position the flow is choked at the rotor outlet. However, the evolution of the choked area highly depends on the rotational speed and the secondary flow. A strong interaction with the tip leakage vortex has been identified.

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Section: Introductionmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Development of Choked Flow in Variable Nozzle Radial Turbines

Tiseira

García-Cuevas

Inhestern

et al. 2021

International Journal of Engine Research

View full text Add to dashboard Cite

show abstract

“…In recent decades, there have been many theories on rotor stator interaction [13][14][15], but two procedures on rotor stator interaction are widely accepted. One was proposed by Kubota [16] and Franke [17] based on the diametrical mode theory.…”

Section: Of 20mentioning

confidence: 99%

Numerical Investigation of the Turbulent Wake-Boundary Interaction in a Translational Cascade of Airfoils and Flat Plate

et al. 2020

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Rotor stator interaction (RSI) is an important phenomenon influencing performances in the pump, turbine, and compressor. In this paper, the correlation-based transition model is used to study the RSI phenomenon between a translational cascade of airfoils and a flat plat. A comparison was made between computational results and experimental results. The computational boundary layer velocity is in reasonable agreement with the experimental velocity. The thickness of boundary layer decreases as the RSI frequency increases and it increases as the fluid flows downstream. The spectral plots of velocity fluctuations at leading edge x/c = 2 under RSI partial flow condition f = 20 Hz and f = 30 Hz are dominated by a narrowband component. RSI frequency mainly affects the turbulence intensity in the freestream region. However, it has little influence on the turbulence intensity of boundary layer near the wall. A secondary vortex is induced by the wake–boundary layer interaction and it leads to the formation of a thickened laminar boundary layer. The negative-vorticity wake also facilitates the formation of a thickened boundary layer while the positive-vorticity wake has a similar effect, like a calmed region which makes the boundary layer thinner.

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“…The shock wave developed on the stator vane can extend to the rotor leading edge (LE), cause high unstable loading on the blades [12], and worsen with increasing pressure ratio [13]. The interaction of the shock wave with the rotor blades generates flow instability in the form of pressure fluctuations at the rotor trailing edge (TE) [14], besides of the decrease in the efficiency [15,16] and increasing the possibility of high cycle fatigue fracture [17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of the Effects of Grooved Stator Vanes in a Radial Turbine Operating at High Pressure Ratios Reaching Choked Flow

et al. 2023

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The flow through the stator vanes of a variable geometry turbocharger turbine can reach supersonic conditions and generates a shock wave on the stator vanes, which has a potential impact on the flow loss as well as on unsteady aerodynamic interaction. The shock wave causes a sudden increase in pressure and can lead to boundary separation and strong excitation force, besides pressure fluctuation in the rotor blades. Thus, in this study, the flat surface of the vanes of a commercial variable geometry turbocharger turbine has been modified to analyze the effects of two grooved surfaces configuration using CFD simulations. The results reveal that the grooves change the turbine efficiency, especially at higher speed, where the increase in the efficiency is between 2% and 6% points. Additionally, the load fluctuation around the rotor leading edge can be reduced and minimize the factors that compromise the integrity of the turbine. Furthermore, the grooves reduce the supersonic pocket developed on the suction side of the vane and diminish the shock wake intensity. Evaluating the effectiveness of the available energy usage in the turbine, on the one hand, at lower speed, the fraction of energy at the inlet destinated to produce power does not change significantly with a grooved surface on the stator vanes. On the other hand, at higher speed and higher pressure ratio with 5 grooves occurs the most effective approach of the maximum energy.

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A study on unsteady aerodynamic excitation forces on radial turbine blade due to rotor-stator interaction

Cited by 8 publications

References 4 publications

Development of Choked Flow in Variable Nozzle Radial Turbines

Development of Choked Flow in Variable Nozzle Radial Turbines

Numerical Investigation of the Turbulent Wake-Boundary Interaction in a Translational Cascade of Airfoils and Flat Plate

Numerical Analysis of the Effects of Grooved Stator Vanes in a Radial Turbine Operating at High Pressure Ratios Reaching Choked Flow

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