Analysis of leading edge flow characteristics in a mixed flow turbine under pulsating flows

Samuel Lee, Martyn Jupp, Simon Barrans, Ambrose Nickson

Research output: Contribution to journalArticle

Abstract

Current trends in the automotive industry towards engine downsizing means turbocharging now plays a vital role in engine performance. A turbocharger increases charge air density using a turbine to extract waste energy from the exhaust gas to drive a compressor. Most turbocharger applications employ a radial inflow turbine. However, to ensure radial stacking of the blade fibers and avoid excessive blade stresses, the inlet blade angle must remain at zero degrees, creating large incidence angles. Alternately, mixed flow turbines can offer non-zero blade angles while maintaining radial stacking of the blade fibers and reducing leading edge separation at low velocity ratios. Furthermore, the physical blade cone angle introduced reduces the blade mass at the rotor outer diameter reducing rotor inertia and improving turbine transient response. The current paper investigates the performance of a mixed flow turbine under a range of pulsating inlet flow conditions. A significant variation in incidence across the LE span was observed within the pulse, where the distribution of incidence over the LE span was also found to change over the duration of the pulse. Analysis of the secondary flow structures developing within the volute shows the non-uniform flow distribution at the volute outlet is the result of the Dean effect in the housing passage. In-depth analysis of the mixed flow effect is also included, showing that poor axial flow turning ahead of the rotor was evident, particularly at the hub, resulting in modest blade angles. This work shows that the complex secondary flow structures that develop in the turbine volute are heavily influenced by the inlet pulsating flow. In turn, this significantly impacts the rotor inlet conditions and rotor losses.
Original languageEnglish
Pages (from-to)78-95
Number of pages18
JournalProceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy
Volume233
Issue number1
Early online date5 Jun 2018
DOIs
Publication statusPublished - 1 Feb 2019

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Turbines
Rotors
Inlet flow
Secondary flow
Flow structure
Turbomachine blades
Engines
Fibers
Axial flow
Exhaust gases
Automotive industry
Transient analysis
Compressors
Cones
Air

Cite this

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abstract = "Current trends in the automotive industry towards engine downsizing means turbocharging now plays a vital role in engine performance. A turbocharger increases charge air density using a turbine to extract waste energy from the exhaust gas to drive a compressor. Most turbocharger applications employ a radial inflow turbine. However, to ensure radial stacking of the blade fibers and avoid excessive blade stresses, the inlet blade angle must remain at zero degrees, creating large incidence angles. Alternately, mixed flow turbines can offer non-zero blade angles while maintaining radial stacking of the blade fibers and reducing leading edge separation at low velocity ratios. Furthermore, the physical blade cone angle introduced reduces the blade mass at the rotor outer diameter reducing rotor inertia and improving turbine transient response. The current paper investigates the performance of a mixed flow turbine under a range of pulsating inlet flow conditions. A significant variation in incidence across the LE span was observed within the pulse, where the distribution of incidence over the LE span was also found to change over the duration of the pulse. Analysis of the secondary flow structures developing within the volute shows the non-uniform flow distribution at the volute outlet is the result of the Dean effect in the housing passage. In-depth analysis of the mixed flow effect is also included, showing that poor axial flow turning ahead of the rotor was evident, particularly at the hub, resulting in modest blade angles. This work shows that the complex secondary flow structures that develop in the turbine volute are heavily influenced by the inlet pulsating flow. In turn, this significantly impacts the rotor inlet conditions and rotor losses.",
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Analysis of leading edge flow characteristics in a mixed flow turbine under pulsating flows. / Lee, Samuel; Jupp, Martyn; Barrans, Simon; Nickson, Ambrose.

In: Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, Vol. 233, No. 1, 01.02.2019, p. 78-95.

Research output: Contribution to journalArticle

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