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Reducing Secondary Flow Losses in Low-Pressure Turbines: The “Snaked” Blade^{ †}

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## Abstract

**:**

## 1. Introduction

## 2. The “Snaked” Blade Concept

## 3. Design of a “Snaked” Blade

^{+}of the first grid points from the wall is always kept around 1. The capability of the present numerical setup in assessing secondary flows for LPT blades has been recently discussed by [18,19,20]. These previous works show numerical accuracy comparing RANS results with both measurements and high fidelity data, showing the reliability of the present approach in predicting secondary flow vortex pattern and the associated secondary losses.

#### 3.1. Results of the Optimization

#### 3.2. Design Assessment: Impact of Numerical Modelling

#### 3.3. Accounting for the Cavity Purge Flows

## 4. Experimental Validation

#### 4.1. Linear Stage Environment

#### 4.2. Performance at Varying Inlet BLs

## 5. Design of a Whole LPT Module

## 6. Conclusions

## 7. Patents

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## Abbreviations

BL | Boundary Layer |

CFD | Computational Fluid Dynamics |

LPT | Low Pressure Turbine |

RANS | Reynolds Averaged Navier-Stokes (equations) |

RMS | Root Mean Square |

TE | Trailing Edge |

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**Figure 5.**Results of the “snaked” blade design: (

**a**) optimization clouds; (

**b**) morphing parameter distribution along the span; (

**c**) swirl angle distribution for the original and the optimized stator; (

**d**) spanwise distribution of the rotor total pressure loss coefficient.

**Figure 7.**Performance of the “snaked” blade at varying Reynolds number: (

**a**) stage efficiency; (

**b**) vane losses.

**Figure 8.**Boundary layer (BL) streamlines on the blade suction side at Re = 100,000 (

**a**) orig blade; (

**b**) snaked blade.

**Figure 12.**Results of the design campaign with cavity purge flows included: (

**a**) swirl angle distribution at stator exit; (

**b**) morphing parameter distribution along the span; (

**c**) optimization clouds.

**Figure 14.**Comparison between numerical and experimental results: (

**a**) pitch-wise averaged swirl angle distribution; (

**b**) pitch-wise averaged total pressure loss coefficient ; (

**c**) 2D contour-plots of total pressure losses downstream of the snaked blade.

**Figure 17.**“Snaked” blade robustness: measured and computed spanwise distributions of the exit blade-to-blade angle at varying inlet conditions

Steady | $\mathsf{\Delta}{\mathit{Y}}_{\mathit{stator}}$ | $\mathsf{\Delta}{\mathit{\eta}}_{\mathit{stage}}$ |
---|---|---|

$k-\omega $ fully turb | 0.08 | 0.30 |

$k-\omega $ low-Re | 0.09 | 0.32 |

$k-\omega $$\gamma -{\tilde{Re}}_{\theta t}$ | 0.09 | 0.30 |

Unsteady | $\mathsf{\Delta}{\mathit{Y}}_{\mathit{stator}}$ | $\mathsf{\Delta}{\mathit{\eta}}_{\mathit{stage}}$ |

$k-\omega $ low-Re | 0.04 | 0.45 |

Unsteady $\mathit{\gamma}-{\tilde{\mathit{Re}}}_{\mathit{\theta}\mathit{t}}$ | |
---|---|

$\mathsf{\Delta}{Y}_{stator}$ | $\mathsf{\Delta}{\eta}_{stage}$ |

0.08 | 0.38 |

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**MDPI and ACS Style**

Giovannini, M.; Rubechini, F.; Marconcini, M.; Arnone, A.; Bertini, F. Reducing Secondary Flow Losses in Low-Pressure Turbines: The “Snaked” Blade. *Int. J. Turbomach. Propuls. Power* **2019**, *4*, 28.
https://doi.org/10.3390/ijtpp4030028

**AMA Style**

Giovannini M, Rubechini F, Marconcini M, Arnone A, Bertini F. Reducing Secondary Flow Losses in Low-Pressure Turbines: The “Snaked” Blade. *International Journal of Turbomachinery, Propulsion and Power*. 2019; 4(3):28.
https://doi.org/10.3390/ijtpp4030028

**Chicago/Turabian Style**

Giovannini, Matteo, Filippo Rubechini, Michele Marconcini, Andrea Arnone, and Francesco Bertini. 2019. "Reducing Secondary Flow Losses in Low-Pressure Turbines: The “Snaked” Blade" *International Journal of Turbomachinery, Propulsion and Power* 4, no. 3: 28.
https://doi.org/10.3390/ijtpp4030028