Investigation on the Effects of Nozzle Openings for a Radial Turbine with Variable Nozzle

Liu, Yinhong; Lao, Dazhong; Liu, Yixiong; Yang, Ce; Qi, Mingxu

doi:10.4271/2014-01-1648

Cited by 7 publications

(3 citation statements)

References 10 publications

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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]. Rubechini et al [21] found that the strength of the unsteady interaction is related to the shock wave pattern at the region between the nozzle and the rotor.…”

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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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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“…Beside of reducing the efficiency, 17,18 the pressure fluctuation in the rotor blade can cause resonance and increase the possibility of high cycle fatigue fracture. [19][20][21][22] Such a risk can also be product of the propagation of secondary flow patterns as corner vortices and horseshoe vortices from the stator vane leading edge to the rotor. 23,24 Rubechini et al 25 highlighted that the strength of the unsteady interaction is related with the pattern of the shock wave at the region between the nozzle and the rotor, such pattern depend on the nozzle geometry.…”

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

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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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“…A specific design was developed to strengthen the reliability of rotor blades. Liu et al 14 investigated the effects of shock wave and clearance flow on aerodynamic losses and forced response of rotor blades by numerical method. The results showed that the forced response of the rotor blade is increased due to the interaction of shock wave and clearance flow.…”

Section: Introductionmentioning

confidence: 99%

Investigation on the flow characteristics of a VNT turbine under pulsating flow conditions

Lei

Wang

et al. 2017

Proceedings of the Institution of Mechanical Engineers, Part D:

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The turbines used in turbochargers naturally experience unsteadiness caused by inlet pulsating flow conditions and stator–rotor interaction. The unsteadiness has an influence on turbine performance. Meanwhile, under certain small-nozzle opening conditions, strong shock waves can be generated. The synergistic effect of turbine inlet pulsation and shock waves has a significant influence on the turbine performance, rotor blade loading as well as the excitation force exerted on the turbine rotor, which is responsible for turbine rotor high cycle fatigue. In order to understand the influence of pulsating flows on turbine performance and the shock wave characteristic at nozzle trailing edge as well as the incidence angle characteristic of the rotor blade, unsteady numerical simulations were performed to investigate the effect of pulsating flow conditions on the performance, flow characteristics in frequency domain and shock wave behavior in a variable nozzle turbine. The results indicate that the turbine inlet pressure pulsation has strong influence on the turbine performances. Meanwhile, the turbine inlet pulsation flow has a strong influence on the intensity of the shock wave and clearance leakage flow in the nozzle, which causes significant flow losses in the turbine. In addition, at the turbine rotor inlet, the unsteadiness caused by the turbine inlet pulsation varies significantly along the circumferential direction and spanwise. Up to two-thirds of the unsteadiness caused by the turbine inlet pulsation dissipates before entering the rotor due to the flow dissipation and mixing process along the nozzle streamwise. The excitation force exerted on the rotor blade leading edge caused by the turbine inlet pulsation is about the same level as that caused by the stator–rotor interaction.

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Investigation on the Effects of Nozzle Openings for a Radial Turbine with Variable Nozzle

Cited by 7 publications

References 10 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

Development of Choked Flow in Variable Nozzle Radial Turbines

Investigation on the flow characteristics of a VNT turbine under pulsating flow conditions

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