Thermodynamic Modeling for Open Combined Regenerative Brayton and Inverse Brayton Cycles with Regeneration before the Inverse Cycle

Abstract

A thermodynamic model of an open combined regenerative Brayton and inverse Brayton cycles with regeneration before the inverse cycle is established in this paper by using thermodynamic optimization theory. The flow processes of the working fluid with the pressure drops and the size constraint of the real power plant are modeled. There are 13 flow resistances encountered by the working fluid stream for the cycle model. Four of these, the friction through the blades and vanes of the compressors and the turbines, are related to the isentropic efficiencies. The remaining nine flow resistances are always present because of the changes in flow cross-section at the compressor inlet of the top cycle, regenerator inlet and outlet, combustion chamber inlet and outlet, turbine outlet of the top cycle, turbine outlet of the bottom cycle, heat exchanger inlet, and compressor inlet of the bottom cycle. These resistances associated with the flow through various cross-sectional areas are derived as functions of the compressor inlet relative pressure drop of the top cycle, and control the air flow rate, the net power output and the thermal efficiency. The analytical formulae about the power output, efficiency and other coefficients are derived with 13 pressure drop losses. It is found that the combined cycle with regenerator can reach higher thermal efficiency but smaller power output than those of the base combined cycle at small compressor inlet relative pressure drop of the top cycle.

Power and Efficiency Optimization for Open Combined Regenerative Brayton and Inverse Brayton Cycles with Regeneration before the Inverse Cycle

“…A theoretical model of an open combined Brayton cycle (OCBC) was built by Chen et al [ 1 ] on the bases of the models provided by Refs. [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ].…”

“…In the OCBC model built in Ref. [ 1 ], an inverse Brayton cycle was introduced into regenerative Brayton cycle by resorting to the finite-time thermodynamics (FTT) [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ], which has been applied for various processes and cycles [ 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ]. The thermodynamic indexes of the OCBC have been analyzed in Ref.…”

“…The thermodynamic indexes of the OCBC have been analyzed in Ref. [ 1 ]. In order to further optimize the thermodynamic indexes, such as the power output (PO), thermal efficiency (TE), and pressure ratio (PR) of top cycle compressor (TCC), the analytical formulae related with 13 kinds of pressure drop losses (PDLs) are yielded.…”

Thermodynamic analysis and optimization of an air Brayton cycle for recovering waste heat of blast furnace slag

“…With consideration of irreversibilities in flow, mass and heat transfer, the results obtained by using FTT are closer to those of the real devices. FTT can also be well used in the performance analysis of direct and reverse Brayton cycles [24,[26][27][28][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44].…”

“…The similar studies for various open direct and reverse Brayton cycles were performed in Refs [30][31][32][33][34][35][36][37][38][39][40][41][42]…”