Evaluating the Use of Leaned Stator Vanes to Produce a Non-Uniform Flow Distribution Across the Inlet Span of a Mixed Flow Turbine Rotor

Morrison, Rebecca; Spence, Stephen; Kim, Sung In; Leonard, Thomas M.; Starke, Andre

doi:10.1115/1.4047811

Cited by 4 publications

(9 citation statements)

References 17 publications

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“…The stator tilting endwall designs were numerically analyzed in this paper using the commercial CFD software ANSYS 19.5-CFX. The same computational domains as [17] were utilized, as shown in Figure 3b. To reduce the computational effort, steady-state single passage domains were used and they were connected by interfaces.…”

Section: Cfd Modeling Methods and Validationmentioning

confidence: 99%

“…This approach led to an advantage in CFD validation because a single-passage model can be used and thereby greatly reducing the computational effort. More details about this test rig can be found in [17]. Section 2.2 describes the CFD method followed by the validation of the method by comparing the CFD results with the experimental data.…”

Section: Baseline Turbine Stagementioning

confidence: 99%

“…This approach led to an advantage in CFD validation because a single-passage model can be used and thereby greatly reducing the computational effort. More details about this test rig can be found in [17]. This baseline MFT was numerically studied in [17], where it was found that the tip leakage vortex (TLV) was one of the main loss sources in the flow field.…”

Section: Baseline Turbine Stagementioning

confidence: 99%

“…More details about this test rig can be found in [17]. This baseline MFT was numerically studied in [17], where it was found that the tip leakage vortex (TLV) was one of the main loss sources in the flow field. But it was also noted in [17] that the losses due to the TLV could be reduced by modifying the upstream stator vane with a leaned design, which led to significant improvement of the turbine performance.…”

Section: Baseline Turbine Stagementioning

confidence: 99%

“…This baseline MFT was numerically studied in [17], where it was found that the tip leakage vortex (TLV) was one of the main loss sources in the flow field. But it was also noted in [17] that the losses due to the TLV could be reduced by modifying the upstream stator vane with a leaned design, which led to significant improvement of the turbine performance. Therefore, the TLV has been carefully considered in this study when different stator tilting endwall designs were implemented.…”

Section: Baseline Turbine Stagementioning

confidence: 99%

See 4 more Smart Citations

Numerical Investigation of the Performance Impact of Stator Tilting Endwall Designs on a Mixed Flow Turbine

Fridh

Morrison

Ren

et al. 2021

IJTPP

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This paper numerically investigates stator endwall designs for a mixed flow turbine. One key design parameter studied is the tilting angle of the stator endwall. By examining stator designs with different tilting angles, the aim of this paper is to improve the efficiency of the studied mixed flow turbine at low velocity ratio working conditions. The performance curve at the design speed was chosen for the comparison between the baseline design and the tilted endwall designs. First, the numerical predictions for the baseline design were validated with experimental data. Then, to understand the mechanism of the performance variation between the different designs, the internal flow field was analyzed in detail. It was found that the tilting stator endwall could form a geometric “kink” in the endwall profiles. On the shroud side, certain designs with such kink caused local flow separations upstream the rotor leading edge. This separation could have the effect of reducing the intensity of the tip leakage vortex and the exit kinetic energy losses at the rotor outlet and may also improve the performance of the exhaust diffuser. As a result, the peak of the efficiency curve shifted toward lower velocity ratio. If the turbine stage incorporated a downstream exhaust diffuser, the optimal design in this study showed a shift of the velocity ratio of the peak efficiency point from 0.62 to 0.60 compared with the baseline. The maximum efficiency improvement was 1.3% points, which occurred at low velocity ratio. Meanwhile, the peak efficiency was 0.2% points higher than the baseline. If the exhaust diffuser was removed, a similar shift of the efficiency curve was observed but less efficiency gain was achieved at the low velocity ratio condition. A preliminary unsteady simulation was also conducted for the optimal design in this study.

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Section: Cfd Modeling Methods and Validationmentioning

confidence: 99%

Section: Baseline Turbine Stagementioning

confidence: 99%

“…This approach led to an advantage in CFD validation because a single-passage model can be used and thereby greatly reducing the computational effort. More details about this test rig can be found in [17]. This baseline MFT was numerically studied in [17], where it was found that the tip leakage vortex (TLV) was one of the main loss sources in the flow field.…”

Section: Baseline Turbine Stagementioning

confidence: 99%

Section: Baseline Turbine Stagementioning

confidence: 99%

Section: Baseline Turbine Stagementioning

confidence: 99%

See 3 more Smart Citations

Numerical Investigation of the Performance Impact of Stator Tilting Endwall Designs on a Mixed Flow Turbine

Fridh

Morrison

Ren

et al. 2021

IJTPP

Self Cite

View full text Add to dashboard Cite

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Performance Improvement of a Mixed Flow Turbine Using 3D Blading

Elliott

Spence

Seiler

et al. 2022

Journal of Turbomachinery

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Mixed flow turbines have reached a level of maturity where iterative performance improvements are small, with real performance benefits coming from better matching to a given application as opposed to improvements in technology. One design feature of mixed flow turbines used to control rotor stress is the radial fibre constraint, wherein blade material is stacked radially outward along the blade. While this constraint yields a mechanical benefit, it constrains the aerodynamic design significantly, with the blade shape defined by one camberline. One potential means of realizing a performance improvement is the use of 3D blading, where the blade is not constrained to a radially fibred structure. In such a design, the blade shape could be freely modified to better control blade loading and secondary flows. This study investigated the viability of such 3D blading through optimization of a state of the art mixed flow turbine. An equivalent design was ensured by maintaining the meridional shape and operating conditions of the baseline wheel, facilitating a fair comparison between the radial and 3D wheels. The paper details the optimization including an innovative constraint-driven geometry modification tool, experimental validation of performance predictions, and an investigation into why 3D blading facilitated a performance improvement. The optimization process identified a performance improvement across the turbocharger operating line. With improvements facilitated through a reduction in tip leakage loss, and improved pressure recovery within the diffuser. Importantly, the optimized design met targets for mass flow, stress levels and modal behaviour, through the novel geometry modification process.

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Investigation of a Novel Turbine Housing to Produce a Nonuniform Spanwise Flow Field at the Inlet to a Mixed Flow Turbine and Provide Variable Geometry Capabilities

Morrison¹,

Stuart

Kim³

et al. 2023

Journal of Turbomachinery

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Automotive engine downsizing has placed an increased focus on the ability of the turbocharger to provide adequate boost levels across the full engine operating rage. To achieve the desired levels of turbocharger performance the turbine must be capable of operating effectively at the intended design point and also at off-design conditions. Mixed flow turbines (MFTs) provide a potential method to improve performance at off-design conditions and during transient engine operation. A unique feature of a MFT is the spanwise variation of incidence angle at the rotor leading edge. This results in additional flow separation from the blade suction surface near the hub under a wide range of operating conditions. The flow separation generates additional loss and has a detrimental impact on turbine performance. A novel turbine volute was designed to produce a spanwise variation in flow conditions at the rotor inlet. The primary objective was to reduce the incidence angle and increase the mass flow rate at the hub side of the passage relative to the shroud side, as it has previously been identified that this can be beneficial for MFT performance. A number of different volute geometries were examined by numerical analysis to determine the impact of key parameters on turbine performance. The results indicated that generating a suitable spanwise flow distribution could produce a moderate improvement in turbine efficiency at off-design operating conditions. The novel volute design also provided a means of achieving a degree of variable geometry operation to further improve off-design performance.

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Evaluating the Use of Leaned Stator Vanes to Produce a Non-Uniform Flow Distribution Across the Inlet Span of a Mixed Flow Turbine Rotor

Cited by 4 publications

References 17 publications

Numerical Investigation of the Performance Impact of Stator Tilting Endwall Designs on a Mixed Flow Turbine

Numerical Investigation of the Performance Impact of Stator Tilting Endwall Designs on a Mixed Flow Turbine

Performance Improvement of a Mixed Flow Turbine Using 3D Blading

Investigation of a Novel Turbine Housing to Produce a Nonuniform Spanwise Flow Field at the Inlet to a Mixed Flow Turbine and Provide Variable Geometry Capabilities

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