Session: 20-02: Gas Turbine Operation and Maintenance

Paper Number: 153661

Design of Integrated Bleed System for Aeroderivative Gas Turbine 

In some multi-shaft gas turbines (GT), low pressure compressor (LPC) bleed air vents via the LPC bleed air collector to ambient in order to adjust airflow to the high pressure compressor (HPC) during part-load operation and transients. This bleed air is controlled by a variable bypass valve (VBV) and must be ducted outside the enclosure through a dedicated duct.

Traditionally, this implies the design of an external duct mounted on the top of the enclosure, which needs to withstand the thermal loads, to respect the acoustic requirements and to allow a proper operation of the engine in all conditions.

This work describes an innovative design of the VBV discharge system, by integrating it with the GT exhaust duct, instead of having a separated duct installed outside. In such configuration the LPC bleed air is routed in a duct placed inside the enclosure and connected to the GT exhaust stack, helping to reduce weight, volume and cost of the entire unit.

However, this solution comes with several technical challenges such as the coupling of the bleed airflow with the GT exhaust flow, which needs to be optimized. solved. When the VBV is open, even partially, the bleed flow and the GT exhaust gases are mixed in the same duct and there is the necessity to guarantee a proper uniformity of temperature and velocity, in order to reduce thermal stresses to the silencer panels and eventually also waste heat recovery units (WHRU). On the other hand, when the VBV is closed, there is a possible backflow of hot exhaust gases from the GT stack towards the VBV collector, which may damage the components installed in that area.

The proposed solution has been designed using CFD simulations and validated by experimental data. An extensive campaign of numerical analyses has been performed to understand the most impacting fluid dynamic phenomena that affect the integrated system. Consequently, a series of different conceptual designs have been analyzed and finally the winning solution has been optimized in all its features.

Presenting Author: Gabriele Lucherini Baker Hughes

Presenting Author Biography: After earning my Master's Degree in Aerospace Engineering at Università di Pisa and a Short Training Program at von Karman Institute of Fluid Dynamics in Belgium, I moved to Torino to work for FIAT, the biggest automotive company in Italy. One year later I joined Baker Hughes in Firenze, where I started to work on gas turbines as fluid dynamics and CFD specialist. During the last 10 years I have worked and gained experience in all kinds of applications for gas turbines, developing a strong knowledge in ventilation and cooling systems and trying to drive new technological solutions. Additionally, I gained expertise in the field of safety, especially related to applications where hydrogen is used as main fuel.

Authors:

Gabriele Lucherini Baker Hughes
Stefano Gimmi Baker Hughes
Stefano Minotti Baker Hughes
Rajnish Kumar Singh Baker Hughes