Determination of the optimum performance of gas turbines

Sun

International Journal of Green Energy

2005

In this paper, the power output of the cycle is taken as objective for performance optimization of an irreversible regenerated closed Brayton cycle coupled to constant-temperature thermal energy reservoirs in the viewpoint of finite time thermodynamics (FTT) or entropy generation minimization (EGM). The analytical formulae about the relations between power output and pressure ratio are derived with the heat resistance losses in the hot-and cold-side heat exchangers and the regenerator, the irreversible compression and expansion losses in the compressor and turbine, and the pressure drop loss in the piping. The maximum power output optimization is performed by searching the optimum heat conductance distribution corresponding to the optimum power output among the hot-and cold-side heat exchangers and the regenerator for the fixed total heat exchanger inventory. The influence of some design parameters, including the temperature ratio of the heat reservoirs, the total heat exchanger inventory, the efficiencies of the compressor and the turbine, and the pressure recovery coefficient, on the optimum heat conductance distribution and the maximum power output are provided. The power plant design with optimization leads to smaller size including the compressor, turbine, and the hot-and cold-side heat exchangers and the regenerator.

Section: Figuresupporting

confidence: 75%

Optimum Heat Conductance Distribution for Power Optimization of a Regenerated Closed Brayton Cycle

Sun

International Journal of Green Energy

2005

Proceedings of the Institution of Mechanical Engineers, Part A:

“…28 to allow for multiple intercooling and reheating stages. More recently, Horlock and Woods 29 provided a new analytical formulation for the maximum efficiency and net-work of the simple recuperative-cycle by introducing non-perfect gas and pressure losses effects. This approach stemmed from the work of Woods et al., 30 which adopted isentropic efficiencies for the irreversibility analysis.…”

Section: Introductionmentioning

confidence: 99%

Efficiency optimisation of advanced gas turbine recuperative-cycles

Bontempo

Manna

2019

The paper presents a theoretical analysis of three advanced gas turbine recuperative-cycles, that is, the intercooled, the reheat and the intercooled and reheat cycles. The internal irreversibilities, which characterise the compression and expansion processes, are taken into account through the polytropic efficiencies of the compressors and turbines. As customary in simplified analytical approaches, the study is carried out for an uncooled closed-circuit gas turbine without pressure losses in the heat exchangers and using a calorically perfect gas as working fluid. Although the accurate performance prediction of a real-gas turbine is prevented by these simplifying assumptions, this analysis provides a fast and simple approach which can be used to theoretically explain the main features of the three advanced cycles and to compare them highlighting pros and contra. The effect of the heat recuperation is investigated comparing the thermal efficiency of a given cycle type with those of two reference cycles, namely, the non-recuperative version of the analysed cycle and the simple cycle. As a result, the ranges of the intermediate pressure ratios returning a benefit in the thermal efficiency in comparison with the two reference cycles have been obtained for the first time. Finally, for the sole intercooled and reheat recuperative-cycle, a novel analytical expression for the intermediate pressure ratios yielding the maximum thermal efficiency is also given.

“…The Braysson cycle is a hybrid power cycle based on a conventional Brayton cycle for the high tempe rature heat addition while adopting the Ericsson cycle for the low temperature heat rejection as proposed and investigated by Frost et al [1] using the first law of thermodynamics. Very recently, some workers [2][3] have investigated the performance of an endoreversible Braysson cycle based on the analysis of the Brayton [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] and Ericsson [24][25][26][27][28] cycles using the concept of finite time thermodynamics [29][30][31][32][33] for a typical set of operating conditions and obtained some significant results.…”

Section: Introductionmentioning

confidence: 99%

Optimum Criteria on the Performance of an Irreversible Braysson Heat Engine Based on the new Thermoeconomic Approach

Tyagi

Zhou

2004

Entropy

An irreversible cycle model of a Braysson heat engine operating between two heat reservoirs is used to investigate the thermoeconomic performance of the cycle affected by the finite-rate heat transfer between the working fluid and the heat reservoirs, heat leak loss from the heat source to the ambient and the irreversibility within the cycle. The thermoeconomic objective function, defined as the total cost per unit power output, is minimized with respect to the cycle temperatures along with the isobaric temperature ratio for a given set of operating parameters. The objective function is found to be an increasing function of the internal irreversibility parameter, economic parameters and the isobaric temperature ratio. On the other hand, there exist the optimal values of the state point temperatures, power output and thermal efficiency at which the objective function attains its minimum for a typical set of operating parameters. Moreover, the objective function and the corresponding power output are also plotted against the state point temperature and thermal efficiency for a different set of operating parameters. The optimally operating regions of these important parameters in the cycle are also determined. The results obtained here may provide some useful criteria for the optimal design and performance improvements, from the point of view of economics as well as from the point of view of thermodynamics of an irreversible Braysson heat engine cycle and other similar cycles as well