TRANSIT CODE FOR UNSTEADY FLOWS IN SOLAR-GRAVITY DRAUGHT TURBINE TOWERS

摘要

Unsteady, non-isentropic, discontinuous flows with energyexchange, during solar heating transients of air turbine towersare approached through a proprietary computational frontmethod, initially developed for the study of ignition in solidpropellant rocket motors. Its application in the discontinuousflows with energy exchange also proves highly efficient.Computational efficiency is demonstrated by CFD simulation oftransients in the air accelerator of the SEATTLER solar mirror,turbine tower. This is a typically unsteady flow simulation forslender channels. A 1-D computational scheme was developedto simulate the interference between zones with different flowconditions. Given values for the thermochemical properties ofthe working gas are considered and two zones of different flowcharacteristics are identified. The first zone is the heatexchanger, where a nonisentropic flow develops. At the aft endof this heating zone a second zone of the channel is encounteredafter a blunt passage, where an isentropic expansion of the gasbegins and extends along the tower up to the upper exit. Into the1-D, unsteady flow scheme of computation, the discontinuity ofequations of motion at the interface between the two zonesinduces very specific precautions and this methodology isdetailed into the paper. Consequently, the computational frontscheme covers the dual behavior of the fully non-isentropicflow with mass addition and mixing in the heater and of thefully isentropic flow at the exhaust of the gravity draught talltower, typical for the solar-gravity draught power plants. Smallperturbations of the flow, in the form of developing weakshocks, and blunt discontinuities are simultaneously covered.Code robustness is demonstrated and revealed throughdiagrams. The 1-D numerical scheme is based on the enhancedmethod of the computational front with resolution of theexpansion wave development.