Abstract
The results are reported of exergoeconomic analyses of a simple gas turbine cycle without a fogging system (SGT), a simple steam injection gas turbine cycle (STIG), and a steam injection gas turbine cycle with inlet fogging cooler (FSTIG). The results show that (1) a gas-turbine cycle with steam injection and simultaneous cooling has a higher power output than the other considered cycle; (2) at maximum energy efficiency conditions the gas turbine has the highest exergy efficiency of the cycle components and the lowest value of exergy efficiency is calculated for the fog cooler, where the mixing of air and water at greatly different temperatures causes the high exergy destruction; and (3) utilization of the fogging cooler in the steam injection cycle increases the exergy destruction in the combustion chamber. Furthermore, the simple gas turbine cycle is found to be more economic as its relative cost difference, total unit product cost, and exergoeconomic factors are less than those for the two other configurations. However, its efficiency and net power output are notably lower than for the gas turbine with steam injection and/or fog cooling. The total unit product cost is highest for the simple gas turbine with steam injection.
Highlights
The performance of a gas turbine, output power and efficiency, is affected significantly by ambient temperature, e.g., the output power of a gas turbine decreases as the ambient temperature rises
This study investigated the results for simple gas
The variation in the total unit product cost with turbine inlet temperature (TIT) is shown for the FSTIG, steam injection gas turbine cycle (STIG) and SGT plants in Figure 11, where it is seen that the total unit product cost decreases with TIT for all the plants
Summary
The performance of a gas turbine, output power and efficiency, is affected significantly by ambient temperature, e.g., the output power of a gas turbine decreases as the ambient temperature rises. An inlet air temperature rise of 1 °C reduces the power output by 1% [13] while raising the heat rate of the turbine This effect is of concern to power producers, resulting in the development of many techniques to cool the inlet air to a gas turbine system. The cooling process by fogging is shown on a psychometric chart by a constant enthalpy line in the direction of saturated air, like the adiabatic cooling process Another method for improving the performance of a gas turbine power plant is steam injection [16]. Such an understanding is required for a rational decision in system designs We address this need in the present paper by carrying out exergoeconomic analyses of gas-turbine cycles utilizing both fogging for inlet cooling and steam injection to improve understanding of the techno-economic behavior of such systems and assist improvement efforts. The findings are validated with corresponding results from the literature
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