Session: 21-05 Operational Flexibility

Submission Number: 175962

Enabling Operational Flexibility of Power Generation Systems: Novel Hybrid Thermal Field and Gradient Optimization 

Flexible power generation is crucial for enabling the accelerated penetration of renewables, adapting to their intermittent nature while ensuring global energy security. Directly, the associated rapid start-up, shut-down, and high ramp rates amplify thermal stresses and impact plant cyclic life. To control these stresses and preserve plant life, novel optimization and plant control methods are required. However, the complexities of turbine thermal and cavity flow fields, which evolve from forced to mixed and natural convection, make the field resolution computationally demanding and challenging to validate for industrial applications. The spatio-temporal optimization problem is even more difficult due to the complexity of the thermal and flow fields. This paper presents a novel and realistic design philosophy for the multi-objective function of turbine cases to optimize and control thermal gradients and stresses. It demonstrates Reynolds-averaged Navier-Stokes conjugate heat transfer (RANS-CHT), thermal gradient models as objective functions, with controlled heat flux as variables, and utilizing discrete turbine casing blocks to reduce thermal gradients. The automated multi-objective optimization reduces thermal gradients by up to 70% in the critical zones, with a heater power consumption equivalent to less than 1% of the plant capacity. A hybrid control methodology comprising active control and thermal bridge passive components, to decrease the overall turbine thermal gradient by 80\%, is presented. Thermal bridge materials, such as copper, are utilized in a novel electrical equivalence circuit for this hybrid analysis. Physical measurements on the Oxford Turbine Casing Rig (OTCR) platform facility experiments validate the active numerical analysis. Heater pads and automated controls are designed to control power and flux boundary conditions. The validation measurement results correspond to the expected trend from the numerical analysis. Thermal gradient reduction and the validation framework are critical enablers for flexible power generation. 

Presenting Author: Emeka Nwangele University of Oxford

Presenting Author Biography: Emeka is a Rhodes Scholar and a DPhil candidate in Engineering Sciences at the University of Oxford. He is researching how to improve power plant flexibility for renewable penetration in a transitioning energy system. He obtained the MSc in Energy Systems with Distinction at the University of Oxford in 2021. In 2017, he obtained a B.Eng in Electrical Engineering with a First Class from the University of Nigeria, Nsukka.

Authors:

Emeka Nwangele University of Oxford
Koichi Tanimoto Research and Innovation Centre, Mitsubishi Heavy Industries, Japan
Ryo Egami Research and Innovation Centre, Mitsubishi Heavy Industries, Japan
Budimir Rosic University of Oxford