Oguz Salim Sogut

The effects of intercooling and regeneration on the thermo-ecological performance analysis of an irreversible-closed Brayton heat engine with variable-temperature thermal reservoirs

A thermo-ecological performance analysis of an irreversible intercooled and regenerated closed Brayton heat engine exchanging heat with variable-temperature thermal reservoirs is presented. The effects of intercooling and regeneration are given special emphasis and investigated in detail. A comparative performance analysis considering the objective functions of an ecological coefficient of performance, an ecological function proposed by Angulo-Brown and power output is also carried out. The results indicate that the optimal total isentropic temperature ratio and intercooling isentropic temperature ratio at the maximum ecological coefficient of performance conditions (ECOPmax) are always less than those of at the maximum ecological function ( ) and the maximum power output conditions ( ) leading to a design that requires less investment cost. It is also concluded that a design at ECOPmax conditions has the advantage of higher thermal efficiency and a lesser entropy generation rate, but at the cost of a slight power loss.

Ecological coefficient of performance (ECOP) optimization for an irreversible Brayton heat engine with variable-temperature thermal reservoirs

An ecological performance analysis for an irreversible Brayton heat engine with variabletemperature thermal reservoirs based on the ecological criterion called Ecological Coefficient of Performance (ECOP) is presented. The model considered includes irreversibilities due to finiterate heat transfer and internal dissipations. The effects of design parameters such as isentropic temperature ratio, heat exchanger effectiveness, thermal reservoir inlet temperature ratio and the ratio of hot-to-cold thermal capacity rates of thermal reservoirs, on the general and optimal ecological performances have been investigated in detail. Comparisons of the results with those of an alternative ecological objective function defined in the literature, the maximum power output conditions, and thermal efficiency are also provided.

A comparative performance analysis of endoreversible dual cycle under maximum ecological function and maximum power conditions

Abstract In this paper, a performance analysis and optimization based on the ecological criterion has been performed for an air-standard endoreversible internal combustion engine dual cycle coupled to constant temperature heat reservoirs. The ecological objective function, defined as the power output minus the loss rate of availability is taken as the optimization criterion. The optimal performances and design parameters, such as compression ratio, pressure ratio, cut-off ratio and NTU allocation ratio, which maximize the ecological objective function are investigated. The obtained results are compared with those of the maximum power performance criterion. Since the ecological optimization technique for a dual cycle consists of both power and entropy generation rate, the obtained results lead more realistic design from the point of view of preservation of natural resources.

Ecological performance optimisation of a solar driven heat engine

An optimal performance analysis of a parabolic trough direct steam generation solar driven Rankine cycle power plant at maximum ecological objective function conditions is performed numerically to investigate the optimum design parameters and the optimal ecological performances. Comparisons for thermal efficiencies of the heat engines at maximum power and maximum power density conditions are provided. The effect of different heat transfer mechanisms between thermal reservoirs and working fluid is also investigated and the results are discussed in detail. The main finding of the present paper is that the thermal efficiency of the solar driven power plant at maximum ecological function conditions considered in the present study is always higher than those of the heat engines at maximum power and maximum power density conditions for all values of the allocation parameters concerned and the realistic range of thermal reservoir temperature ratio.

Effect of heat leakage on the performance of a twin-spool turbofan engine

The effect of heat leakage from a twin-spool turbofan engine to the ambient air on the performance of the engine for a commercial aircraft is investigated. Effects of heat leakage on the variation of the performance indicators of coefficient of ecological performance, overall efficiency, exergy destruction factor, thrust specific fuel consumption and entropy generation rate with respect to the design parameters of compressor and fan pressure ratios, by-pass ratio and turbine inlet temperature are investigated numerically. The main findings are as follows: (i) Effect of heat leakage from the combustion chamber to the by-pass air on the coefficient of ecological performance, exergy destruction factor and entropy generation rate is considerably large when compared to that on the other performance indicators especially for small values of design parameters except for turbine inlet temperature. (ii) Effect of heat leakage on the performance indicators is significant for small values of turbine inlet temperature and large values of the other design parameters.

Exergy–based ecological optimisation of a turbofan engine

A novel ecological optimisation is performed by introducing a new coefficient of ecological performance (CEP) defined by propulsive power per unit exergy destruction rate as the objective function for a single spool turbofan engine with an unmixed exhaust considering finite–rate heat transfer from a thermal reservoir at constant temperature. The optimum values for the selected design parameters of compressor pressure ratio, fan pressure ratio, bypass ratio and turbine inlet temperature are determined numerically to maximise this objective function. Furthermore, the overall efficiency, specific thrust, exergy destruction factor, and exergetic sustainability index are considered as the additional objective functions and optimised with respect to the same parameters for comparison. The results show that: i) the compressor pressure ratio range of 15–25.8 provides a good compromise between energy efficiency and ecological performance; ii) a relatively high pressure ratio with a limited flow rate of air through the fan increases ecological performance of the turbofan engine for commercial aircrafts.