DATE:                       Thursday, 10.19.23 

TIME:                        4:00pm

LOCATION:              33-206

SPEAKER:                Aniwat Tiralap, Ph.D.

TOPIC:                      Aero-Thermal-Mechanical Interactions in Ultra High-Speed Micro Gas Turbines

ABSTRACT:

Aero-thermal induced mechanical response of engine components in an ultra high-speed micro gas turbine engine system is assessed. Scaling down gas turbine engines for high performance requirements dictates substantial thermal-induced effects on engine operation due to high temperature gradient relative to that in conventional large gas turbine engines. Experiments indicate that sustainable operation is limited by the mechanical response of the shaft-bearing housing system. It is hypothesized that this is due to thermal-induced mechanical deformation of the shaft-bearing housing that results in bearing clearance variation that differs from the design intent. An unsteady CFD conjugate heat transfer computation of flow and temperature distribution in the engine system is first implemented; this is followed by determining the corresponding mechanical deformation of engine components based on finite element analysis. The computed result shows that at the beginning of the engine start-up process, the radial expansion of the shaft is larger than that of the bearing housing, resulting in a smaller bearing clearance. Toward steady-state operation, a larger bearing clearance is observed. The computed results and experimental observation are in agreement thus confirming the hypothesis. The key controlling non-dimensional parameters characterizing the aerothermal-mechanical interaction and response are identified using a reduced order model that yields thermal-induced mechanical deformation in agreement with the unsteady computations. For a geometrically similar engine system, the controlling thermal and structural parameters consist of: (1) shaft fin parameter, (2) housing fin parameter, (3) ratio of heat diffusivity of housing to that of the shaft, (4) 3 cooling flow parameters, and (5) ratio of the coefficient of thermal expansion of the housing to that of the shaft. The non-dimensional parameters serve as a guideline for developing strategies for controlling bearing clearance under the acceptable margin, including selecting shaft and housing materials with appropriate properties as well as tailoring the cooling flow. An approximate scaling rule for thermal-induced shaft-bearing housing clearance variation in engines of various sizing is formulated.

BIO:
Dr. Aniwat Tiralap is a mechanical engineer with expertise in thermal-fluid engineering. Aniwat graduated from MIT with a Master’s Degree in Mechanical Engineering in 2015. He conducted research on tip leakage flow loss reduction for axial compressors. Aniwat obtained his PhD degree in Mechanical Engineering from MIT in 2020. His PhD thesis focused on aero-thermal-mechanical interactions in ultra high-speed micro gas turbines. His most recent role was as a compressor aerodynamics engineer for Doosan Heavy Industries. His responsibilities included designing new compressors, monitoring rig tests, and developing tools and processes for predicting compressor performance and operability with high accuracy.