Optimum performance of an intercooled reheat regenerative gas turbine power plant. In Gas Turbines: Technology, Efficiency and Performance, Ciafone, D. J. (Ed.), Nova Science Publishers, Hauppauge, New York, (2011).
Optimization of an intercooled reheat regenerative gas turbine power plant combined (ICRHR) is presented in this chapter. The plant consists of eight components, namely LP and HP compressors; intercooler; regenerator; combustor; HP and LP turbines; and reheater. Optimum pressure ratios across the compressors and the turbines are determined. Explicit relationships are derived for the net work and the thermal efficiency of the plant through thermodynamic models of the components, which are expressed as functions of total pressure drop within the cycle, ratio of maximum temperature to minimum temperature of the cycle, efficiencies of the turbines and the compressors, regenerator effectiveness, and overall pressure ratio of the system. It is shown that the maximum thermal efficiency design has the advantages of a higher efficiency, lower emissions, and smaller sizes of turbines and compressors, compared to the maximum work design. Hence, the optimization of the power cycle is carried out by maximizing the thermal efficiency with respect to the overall pressure ratio. The results are presented for the optimal pressure ratio and the corresponding maximum efficiency and the work output versus the ratio of the highest-to-lowest temperatures and the pressure drop factor. Also, a typical comparison is made between the optimum design points of a regenerative gas turbine engine (RGT) and ICRHR cycle in terms of the optimum pressure ratio, optimal thermal efficiency and the corresponding work output under identical conditions.
Multi-criteria optimization of a regenerative gas turbine power cycle. In Gas Turbines: Technology, Efficiency and Performance, Ciafone, D. J. (Ed.), Nova Science Publishers, Hauppauge, New York, (2011).
It is shown in this chapter that to optimize a regenerative gas turbine power plant operating on the basis of an open Brayton cycle by maximization of work output, first law and second law efficiencies, and minimization of total entropy generation rate associated with the power cycle, as fundamental thermodynamic optimization objectives, means to find an optimal for overall pressure ratio of the cycle. The study accounts for components inefficiencies and pressure drop throughout the cycle. It is found that at regenerator effectiveness of 50 percent, maximum work output, maximum 1st law efficiency and minimum entropy generation are coincident; though this value of the effectiveness is irrelevant from practical perspective. However, in general, optimization of any of these four objectives results in different design regimes. It is shown that entropy generation is a basic requirement to drive a Brayton – type heat engine, and it is incorrect to consider the Carnot efficiency as the upper limit of the 1stlaw efficiency of the plant. The results indicate that a real engine must operate at a region imposed by maximum work output and maximum 1st law efficiency. In other words, the pressure ratio of the cycle must lie between pressure ratios obtained by maximization of the work output and maximization of the 1st law efficiency. Furthermore, a criterion is established for utilization of a regenerator, which leads to introduce Critical Pressure Ratio beyond which employing a regenerator would be no longer useful. For the regenerator effectiveness greater than 0.8, the 2nd law efficiency may be considered as a trade-off between the maximum work and maximum 1st law efficiency designs, given that for the regenerator effectiveness around 0.8, a design based on the 2nd law efficiency maximization would be almost equivalent to the maximum work output design.