Gasdynamic behaviours of a radial turbine with pulsating incoming flow

Xue, Yingxian; Yang, Mingyang; Pan, Lei; Deng, Kangyao; Wu, Xin‐Tao; Wang, Cuicui

doi:10.1016/j.energy.2020.119523

Cited by 4 publications

(3 citation statements)

References 14 publications

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“…In order to determine the turbulent eddy viscosity, the turbulence model k-ω SST model [38] is chosen with compressibility correction and Durbin scale limiter for realizability. The k-ω SST model is widely recommended, and well-validated for radial turbomachinery in the literature [39][40][41][42][43] under subsonic, transonic and supersonic conditions [19,44,45]. For the URANS simulations the time step size has been selected as the time that takes the turbine wheel to rotate 2 • depending on the rotational speed [31,46].…”

Section: Methodsmentioning

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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Section: Methodsmentioning

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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“…In order to determine the turbulent eddy viscosity, the turbulence model k-ω SST model [41] is chosen with compressibility correction and Durbin scale limiter for realizability. The k-ω SST model is widely recommended, and well-validated for radial turbomachinery in the literature [42][43][44][45][46] under subsonic, transonic, and supersonic conditions [47][48][49]. The SST model has seen relatively wide application in the aerospace industry, where viscous flows are typically resolved, and turbulence models are applied throughout the boundary layer.…”

Section: Numerical Modelmentioning

confidence: 99%

Numerical Analysis of the Effects of Different Rotor Tip Gaps in a Radial Turbine Operating at High Pressure Ratios Reaching Choked Flow

et al. 2022

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To operate, radial turbines used in turbochargers require a minimum tip gap between the rotor blades and the stationary wall casing (shroud). This gap generates leakage flow driven by the pressure difference between the pressure and suction side. The tip leakage flow is largely unturned, which translates into a reduction of the shaft work due to the decrease in the total pressure. This paper investigates the flow through the rotor blade tip gap and the effects on the main flow when the turbine operates at a lower and higher pressure ratio with the presence of supersonic regions at the rotor trailing edge for two rotational speeds using computational fluid dynamics (CFD). The rotor tip gap has been decreased and increased up to 50% of the original tip gap geometry given by the manufacturer. Depending on the operational point, the results reveal that a reduction of 50% of the tip gap can lead to an increase of almost 3% in the efficiency, whereas a rise in 50% in the gap penalty the efficiency up to 3%. Furthermore, a supersonic region appears in the tip gap just when the flow enters through the pressure side, then the flow accelerates, leaving the suction side with a higher relative Mach number, generating a vortex by mixing with the mainstream. The effects of the vortex with the variation of the tip gap on the choked area at the rotor trailing edge presents a more significant change at higher than lower speeds. At a higher speed, the choked region closer to the shroud is due to the high relative inlet flow angle and the effects of the high relative motion of the shroud wall. Furthermore, this relative motion forces the tip leakage vortex to stay closer to the tip suction side, generating a subsonic region, which increases with the tip gap height. The leakage flow at lower and higher rotational speed does not affect the main flow close to the hub. However, close to the shroud, the velocity profile changes, and the generated entropy increases when the flow goes through the tip gap.

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“…A frozen rotor without mixing plane was chosen in the steady simulations to avoid vanishing of rotor-stator interactions. To obtain turbulence closure the k− ω SST model 44 has been selected, as it is widely recommended and well validated for radial turbomachinery in the literature 45–48 even under transonic and supersonic conditions. 21,49,50 Furthermore, with a finer grid and improved resolution in the near wall region the model generates results that agree well with the experimental data.…”

Section: Numerical Setupmentioning

confidence: 99%

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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Gasdynamic behaviours of a radial turbine with pulsating incoming flow

Cited by 4 publications

References 14 publications

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

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

Numerical Analysis of the Effects of Different Rotor Tip Gaps in a Radial Turbine Operating at High Pressure Ratios Reaching Choked Flow

Development of Choked Flow in Variable Nozzle Radial Turbines

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