Investigation on a cooling channel design for a high heat flux oxy-fuel direct power extraction combustor
The implementation of oxy-fuel technology in fossil-fuel power generation could result in a drastic increase of system efficiencies and a reduction of emissions. While typical system temperatures are dictated by material constraints, open-cycle magnetohydrodynamic (MHD) power generators have the potential to utilize the energy of undiluted flames. This work presents design and modeling strategies to develop steady-state supersonic MHD combustors operating at temperatures exceeding 3000 K. Throughout the study, computational fluid dynamics (CFD) models were extensively used as a design and optimization tool. A proof-of-concept 60 kWth model was designed, manufactured and tested in accordance to methods relevant to rocket engine technologies. A fully-coupled numerical method was developed in ANSYS FLUENT to characterize the heat transfer in the system; this study revealed that nozzle heat transfer may be predicted through a 40% reduction of the semi-empirical Bartz correlation. Experimental results showed good agreement with the numerical evaluation, with the combustor exhibiting a favorable performance when tested during extended time periods. The results observed in the proof-of-concept system were employed to develop a 1-MW scaled prototype. Scaling methods were based on critical design criteria found in similar systems, aimed at replicating combustion flow fields and reducing possible instabilities. The scaled prototype was manufactured through selective laser melting (SLM)-based additive manufacturing to reduce lead times and increase geometrical complexity. Additional CFD models were developed to optimize coolant manifold system parameters and perform a parametric study on channel geometry. An investigation on coolant manifold geometry demonstrated improvements in channel flow distribution when enlarging manifold lengths and increasing the number of tubes feeding into the flow. A three-dimensional model based on a single channel was developed to capture the effect of variable properties and thermal stratification. All cases in the simulation exhibited higher wall temperatures and lower convective coefficients than those determined through 1-D analytical means. This implies pressure and velocity safety factors must be implemented in system operation. Overall, the findings made in this investigation are thought to be of value to researchers and industrial practitioners when designing thermal protection devices for high temperature, high heat flux systems. In addition to this, the implementation of the developed technology at pilot and commercial scales could result in a significant improvement in the efficiencies of heritage and next-generation power cycles.
Cabrera Maynez, Luisa Alejandra, "Investigation on a cooling channel design for a high heat flux oxy-fuel direct power extraction combustor" (2017). ETD Collection for University of Texas, El Paso. AAI10618317.