Power and efficiency optimization for combined Brayton and two parallel inverse Brayton cycles. Part 2: Performance optimization

Abstract

The power and efficiency of the open combined Brayton and two parallel inverse Brayton cycles are analysed and optimized based on the model established using finite-time thermodynamics in Part 1 of the current paper by adjusting the compressor inlet pressure of the two parallel inverse Brayton cycles, the mass flowrate and the distribution of pressure losses along the flow path. It is shown that the power output has a maximum with respect to the compressor inlet pressures of the two parallel inverse Brayton cycles, the air mass flowrate or any of the overall pressure drops, and the maximized power output has an additional maximum with respect to the compressor pressure ratio of the top cycle. The power output and the thermal conversion efficiency have the maximum values when the mass flowrates of the first and the second inverse Brayton cycles are the same. When the optimization is performed with the constraints of a fixed fuel flowrate and the power plant size, the power output and thermal conversion efficiency can be maximized again by properly allocating the fixed overall flow area among the compressor inlet of the top cycle and the turbine outlets of the two parallel inverse Brayton cycles. The numerical examples show the effects of design parameters on the power output and heat conversion efficiency.

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

“…These resistances control the air flow rate m and the net power output W [26][27][28][29][30][31][32][33][34][35][36][37][38][39][43][44][45][46]. For example, the pressure drop at the compressor inlet of the top cycle is given by:…”

“…The power and the thermal efficiency were optimized by adjusting the bottom cycle pressure ratio and the mass flow rate. Moreover, they studied the performance of the combined Brayton and two parallel inverse Brayton cycles [45,46]. A further step of this paper beyond [37,42,[44][45][46] is to analyze and optimize the performance of the combined regenerative Brayton and inverse Brayton cycles proposed in [42] with consideration of the pressure drops and the size constraints by using similar principles and methods as used in [25][26][27][28][29][30][31].…”

Electrical Generation from Thermal Solar Energy Using a Turbocharger with the Brayton Thermodynamic Cycle

“…The compression of a compressible fluid is not simple: piston engines solved the problem confining the gas in a closed Chamber -cylinder-, and by reducing the volume with a piston, thus increasing the pressure; however, this requires heavy and large engines for big powers, and calls for a high mechanical inertia in order to guarantee its continuous operation. [2] The gas turbine uses a compressor, consisting of one or more steps of rotating blades that transmit a kinetic energy to the gas by accelerating it and then, through some fixed blades or diverting passages that slow it down to convert the added energy into pressure. It was also the advance of technology, the development of new materials and getting a better understanding of fluid mechanics for men to produce the first truly effective compressors, and with that, the first gas turbines.…”

“…In Real Cycles, compression is not completely isoentropical (1-2), but politropical (1-2a), and this is due to friction losses mostly. Heating is not isobarical (2)(3), also due to friction losses within the Heater (2a-3a). Expansion is also politropical (3a-4a).…”

“…+52 81 1997 6516. e.mariscal.phd.mty@itesm.mxThe closed Brayton cycle:Fig. 1Temperature as a function of Entropy in the Closed Brayton Cycle It is assumed as an ideal cycle therefore the working fluid undergoes the four internally reversible processes [2,3]…”