# Thermal Performance Evaluation in Gas Turbine Aero Engines Accessory Gearbox

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## Abstract

**:**

## 1. Introduction

_{2}emissions and a 90% reduction of NOx emissions by 2050) [1,2]. One of these challenges is to deal with huge thermal loads generated by advanced GTEs components. The engine thermal management system (TMS) should be able to manage these heat loads in an optimal feature to get a safe and reliable operation for the engine. In other words, the main duty of the GTE TMS is to use engine heat sinks (oil, fuel, and air) to manage the thermal loads generated by engine heat sources (gearboxes, bearings, generators, pumps, etc.). There are a few studies in the literature focusing on the thermal management challenges and potential solutions for GTEs. An analytic review on this topic has recently been done by the authors [3], in which the different aspects, current challenges, and potential solutions for the TMS design procedure in new and next generation of GTEs were studied in detail. One of the main challenges in this field is the lack of physics-based models for thermal loads calculation in different TMS components to enable researchers and manufacturers to predict and analyze the thermal loads in each component at different flight phases, based on the geometry, mechanical loads, input and output powers, and other design parameters. This kind of model will enable TMS designers to do a precise sensitive analysis on design and operational parameters, as well as to get a reliable vision about the next generation of TMSs for GTEs [4].

## 2. Accessory Gearbox Heat Loss Mechanisms

## 3. Mathematical Modelling of Heat Losses

#### 3.1. No-Load Dependent Losses

#### 3.1.1. Gears Churning Loss

#### 3.1.2. Bearings Churning Loss

#### 3.1.3. Seals Churning Loss

#### 3.2. Load Dependent Losses

#### 3.2.1. Power Loss in Meshing Gears

#### 3.2.2. Power Loss in Bearings

## 4. Results Analysis

- The gear set connected to the generator creates the highest value of loss in comparison with other elements due to the high power transmitted which causes high friction between the gears as the friction coefficient change with power transmitted.
- The oil and fuel pump gear sets have the next ranks in generating heat loads. The loss in hydraulic pump is less than 2 kW in all flight phases.
- The assumption of neglecting other elements (e.g., de-oiler and heat transfer from the engine components) is valid, as the generated heat loads would be very small (in the order of 1 kW and less).

## 5. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

## References

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Component | Speed Ratio to HP Spool |
---|---|

Oil Pump | 0.62 |

Generator | 1.79 |

Fuel Pump | 0.9 |

Hydraulic Pump | 0.5 |

Conditions | Idle | Take Off | Begin Climb | Climb | End Climb | Start Cruise | End Cruise | Begin Descent | End Descent | Approach |
---|---|---|---|---|---|---|---|---|---|---|

HP Power (kW) | 825 | 24700 | 23200 | 14100 | 9700 | 8570 | 7260 | 5080 | 1090 | 6870 |

Speed (%) | 0.28 | 0.88 | 0.88 | 0.92 | 0.91 | 0.88 | 0.88 | 0.80 | 0.69 | 058 |

Parameter | Index | Unites | Value |
---|---|---|---|

Base helix angle | $\beta $ | $\xb0$ | 10 |

Bearing mean diameter | ${d}_{m}$ | $m$ | 0.20 |

Pitch diameter | $d$ | $m$ | 0.35 |

Immersed area | ${A}_{i}$ | ${m}^{2}$ | 1.0996 × 10^{−6} |

Gear immersion depth | $h$ | $m$ | 0.22 |

Shaft diameter | ${d}_{i}$ | $m$ | 0.2 |

Oil volume | ${V}_{oil}$ | ${m}^{3}$ | 0.0012 |

N of teeth (Oil Pump) | z | - | 77 |

N of teeth (Fuel Pump) | z | - | 75 |

N of teeth (Generator) | z | - | 20 |

N of teeth (Hydraulic Pump) | z | - | 67 |

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**MDPI and ACS Style**

Jafari, S.; Bouchareb, A.; Nikolaidis, T.
Thermal Performance Evaluation in Gas Turbine Aero Engines Accessory Gearbox. *Int. J. Turbomach. Propuls. Power* **2020**, *5*, 21.
https://doi.org/10.3390/ijtpp5030021

**AMA Style**

Jafari S, Bouchareb A, Nikolaidis T.
Thermal Performance Evaluation in Gas Turbine Aero Engines Accessory Gearbox. *International Journal of Turbomachinery, Propulsion and Power*. 2020; 5(3):21.
https://doi.org/10.3390/ijtpp5030021

**Chicago/Turabian Style**

Jafari, Soheil, Ahmed Bouchareb, and Theoklis Nikolaidis.
2020. "Thermal Performance Evaluation in Gas Turbine Aero Engines Accessory Gearbox" *International Journal of Turbomachinery, Propulsion and Power* 5, no. 3: 21.
https://doi.org/10.3390/ijtpp5030021