Thermoeconomic optimization of an ice thermal storage system for gas turbine inlet cooling

The gas turbine power output and efficiency decrease with increasing ambient temperature. With compressor inlet air cooling, the air density and mass flow rate as well as the gas turbine net power output increase. The inlet cooling techniques include vapor or absorption refrigeration systems, evaporative cooling systems and thermal energy storage (TES) systems. In this paper the thermoeconomic analysis of ice (latent) thermal energy storage system for gas turbine inlet cooling application was performed. The optimum values of system design parameters were obtained using genetic algorithm optimization technique. The objective function included the capital and operational costs of the gas turbine, vapor compression refrigeration system, without (objective function I) and with (objective function II) corresponding cost due to the system exergy destruction. For gas turbines with net power output in the range of 25-100 MW, the inlet air cooling using a TES system increased the power output in the range of 3.9-25.7%, increased the efficiency in the range 2.1-5.2%, while increased the payback period from about 4 to 7.7 years.     

Maisotsenko循环在燃气轮机进气冷却中的应用研究

采用基于Maisotsenko循环的露点间接蒸发式冷却作为进气冷却的手段,研究了不同环境条件下其对燃气轮机性能的提升效果。建立了针对某9E级燃气轮机的热力循环过程的计算模型,并利用该热力模型分析了进气温度变化对燃机出力的影响。基于Maisotsenko循环的原理,以温降为指标对露点间接蒸发冷却器的性能进行了分析。以功率和效率作为指标,对燃气轮机性能随环境条件的变化情况做了数值模拟,对露点蒸发式冷却与无进气冷却、直接喷雾式冷却对燃机性能的影响进行了计算分析。结果表明,在高温低湿度的条件下,露点间接蒸发式冷却能有效提升燃机性能。     

Effects of evaporative inlet and aftercooling on the recuperated gas turbine cycle

Inlet air cooling and cooling of the compressor discharge using water injection boost both efficiency and power of gas turbine cycles. Four different layouts of the recuperated gas turbine cycle are presented. Those layouts include the effect of evaporative inlet and aftercooling (evaporative cooling of the compressor discharge). A parametric study of the effect of turbine inlet temperature (TIT), ambient temperature, and relative humidity on the performance of all four layouts is investigated. The results indicate that as TIT increases the optimum pressure ratio increases by 0.45 per 100 K for the regular recuperated cycle and by 1.4 per 100 K for the recuperated cycle with evaporative aftercooling. The cycles with evaporative aftercooling have distinctive pattern of performance curves and higher values of optimum pressure ratios. The results also showed that evaporative cooling of the inlet air could boost the efficiency by up to 3.2% and that evaporative aftercooling could increase the power by up to about 110% and cycle efficiency by up to 16%.     

Performance enhancement of gas turbines by inlet air‐cooling in hot and humid climates

In this paper, a model to study the effect of inlet air‐cooling on gas turbines power and efficiency is developed for two different cooling techniques, direct mechanical refrigeration and an evaporative water spray cooler. Energy analysis is used to present the performance improvement in terms of power gain ratio and thermal efficiency change factors. Relationships are derived for an open gas turbine cycle with irreversible compression and expansion processes coupled to air‐cooling systems. The obtained results show that the power and efficiency improvements are functions of the ambient conditions and the gas turbine pressure ratio. The performance improvement is calculated for, ambient temperatures from 30 to 50°C, the whole range of humidity ratio (10–100%) and pressure ratio from 8 to 12. For direct mechanical refrigeration air‐cooling, the power improvement is associated with appreciable drop in the thermal efficiency. The maximum power gain can be obtained if the air temperature is reduced to its lowest limit that is the refrigerant evaporation temperature plus the evaporator design temperature difference. Water spray cooling process is sensitive to the ambient relative humidity and is suitable for dry air conditions. The power gain and efficiency enhancement are limited by the wet bulb temperature. The performance of spray evaporative cooler is presented in a dimensionless working graph. The daily performance of the cooling methods is examined for an ABB‐11D5 gas turbine operating under the hot humid conditions of Jeddah, Saudi Arabia. The results indicate that the direct mechanical refrigeration increased the daily power output by 6.77% versus 2.57% for the spray air‐cooling. Copyright © 2005 John Wiley & Sons, Ltd.     

MAT, a novel, open cycle gas turbine for power augmentation

A Moisture Air Turbine (MAT) cycle is proposed for improving the characteristics of land-based gas turbines by injecting atomized water through an inlet into a compressor. Compressor work of isentropic compression for moist air mixtures with phase change is theoretically considered, which has revealed that water evaporation may reduce compressor work. An experiment using a 15 MW class axial flow load compressor has also verified the theory. Realistic cycle model calculations predict that a 10% power increment by a ratio of 1% water to compressor intake air is expected and also that the amount of water consumption is much less than that of conventional inlet air cooling systems, used for heat rejection at the cooling tower. In addition, thermal efficiency is anticipated to be improved mainly due to the reduction of compressor work. Contrary to the conventional evaporative cooler, a MAT cycle could provide power output at a desired value within its capability regardless of ambient humidity condition.     

Energetic and exergetic performance analyses of a combined heat and power plant with absorption inlet cooling and evaporative aftercooling

In this paper, exergy method is applied to analyze the gas turbine cycle cogeneration with inlet air cooling and evaporative aftercooling of the compressor discharge. The exergy destruction rate in each component of cogeneration is evaluated in detail. The effects of some main parameters on the exergy destruction and exergy efficiency of the cycle are investigated. The most significant exergy destruction rates in the cycle are in combustion chamber, heat recovery steam generator and regenerative heat exchanger. The overall pressure ratio and turbine inlet temperature have significant effect on exergy destruction in most of the components of cogeneration. The results obtained from the analysis show that inlet air cooling along with evaporative aftercooling has an obvious increase in the energy and exergy efficiency compared to the basic gas turbine cycle cogeneration. It is further shown that the first-law efficiency, power to heat ratio and exergy efficiency of the cogeneration cycle significantly vary with the change in overall pressure ratio and turbine inlet temperature but the change in process heat pressure shows small variation in these parameters.     

Analysis of parameters affecting the performance of gas turbines and combined cycle plants with vapor absorption inlet air cooling

The integration of an aqua‐ammonia inlet air‐cooling scheme to a cooled gas turbine‐based combined cycle has been analyzed. The heat energy of the exhaust gas prior to the exit of the heat recovery steam generator has been chosen to power the inlet air‐cooling system. Dual pressure reheat heat recovery steam generator is chosen as the combined cycle configuration. Air film cooling has been adopted as the cooling technique for gas turbine blades. A parametric study of the effect of compressor–pressure ratio, compressor inlet temperature, turbine inlet temperature, ambient relative humidity, and ambient temperature on performance parameters of plants has been carried out. It has been observed that vapor absorption inlet air cooling improves the efficiency of gas turbine by upto 7.48% and specific work by more than 18%, respectively. However, on the adoption of this scheme for combined cycles, the plant efficiency has been observed to be adversely affected, although the addition of absorption inlet air cooling results in an increase in plant output by more than 7%. The optimum value of compressor inlet temperature for maximum specific work output has been observed to be 25 °C for the chosen set of conditions. Further reduction of compressor inlet temperature below this optimum value has been observed to adversely affect plant efficiency. Copyright © 2013 John Wiley & Sons, Ltd.     

Power and efficiency optimization for combined Brayton and inverse Brayton cycles

A thermodynamic model for open combined Brayton and inverse Brayton cycles is established considering the pressure drops of the working fluid along the flow processes and the size constraints of the real power plant using finite time thermodynamics in this paper. There are 11 flow resistances encountered by the gas stream for the combined Brayton and inverse Brayton cycles. Four of these, the friction through the blades and vanes of the compressors and the turbines, are related to the isentropic efficiencies. The remaining flow resistances are always present because of the changes in flow cross-section at the compressor inlet of the top cycle, combustion inlet and outlet, turbine outlet of the top cycle, turbine outlet of the bottom cycle, heat exchanger inlet, and compressor inlet of the bottom cycle. These resistances control the air flow rate and the net power output. The relative pressure drops associated with the flow through various cross-sectional areas are derived as functions of the compressor inlet relative pressure drop of the top cycle. The analytical formulae about the relations between power output, thermal conversion efficiency, and the compressor pressure ratio of the top cycle are derived with the 11 pressure drop losses in the intake, compression, combustion, expansion, and flow process in the piping, the heat transfer loss to the ambient, the irreversible compression and expansion losses in the compressors and the turbines, and the irreversible combustion loss in the combustion chamber. The performance of the model cycle is optimized by adjusting the compressor inlet pressure of the bottom cycle, the air mass flow rate 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 pressure of the bottom cycle, the air mass flow rate 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. When the optimization is performed with the constraints of a fixed fuel flow rate and the power plant size, the power output and efficiency can be maximized again by properly allocating the fixed overall flow area among the compressor inlet of the top cycle and the turbine outlet of the bottom cycle.     

Comparison of evaporative inlet air cooling systems to enhance the gas turbine generated power

The gas turbine performance is highly sensitive to the compressor inlet temperature. The output of gas turbine falls to a value that is less than the rated output under high temperature conditions. In fact increase in inlet air temperature by 1°C will decrease the output power by 0.7% approximately. The solution of this problem is very important because the peak demand season also happens in the summer. One of the convenient methods of inlet air cooling is evaporating cooling which is appropriate for warm and dry weather. As most of the gas turbines in Iran are installed in such ambient conditions regions, therefore this method can be used to enhance the performance of the gas turbines. In this paper, an overview of technical and economic comparison of media system and fog system is given. The performance test results show that the mean output power of Frame‐9 gas turbines is increased by 11 MW (14.5%) by the application of media cooling system in Fars power plant and 8.1 MW (8.9%) and 9.5 MW (11%) by the application of fog cooling system in Ghom and Shahid Rajaie power plants, respectively. The total enhanced power generation in the summer of 2004 was 2970, 1701 and 1340 MWh for the Fars, Ghom and Shahid Rajaie power plants, respectively. The economical studies show that the payback periods are estimated to be around 2 and 3 years for fog and media systems, respectively. This study has shown that both methods are suitable for the dry and hot areas for gas turbine power augmentation. Copyright © 2007 John Wiley & Sons, Ltd.     

Analytical method for evaluation of gas turbine inlet air cooling in combined cycle power plant

Gas turbine inlet air cooling technologies (GTIAC), mainly including chilling with LiBr/water absorption chiller and fogging as well, are being used during hot seasons to augment the power output. To evaluate the general applicability of inlet air cooling for gas–steam combined cycle power plant (GTCCIAC), parameters such as efficiency ratio, profit ratio and relative payback period were defined and analyzed through off-design performances of both gas turbine and inlet air cooling systems. An analytical method for applicability evaluation of GTCCIAC with absorption chiller (inlet chilling) and saturated evaporative cooler (inlet fogging) was presented. The applicability study based on typical off-design performances of the components in GTCCIAC shows that, the applicability of GTCCIAC with chilling and fogging depends on the design economic efficiency of GTCC power plant. In addition, it relies heavily on the climatic data and the design capacity of inlet air cooling systems. Generally, GTCCIAC is preferable in the zones with high ambient air temperature and low humidity. Furthermore, it is more appropriate for those GTCC units with lower design economic efficiency. Comparison of the applicability between chilling and fogging shows that, inlet fogging is superior in power efficiency at t_a = 15–20 °C though it gains smaller profit margin than inlet chilling. GTCC inlet chilling with absorption chiller is preferable in the zones with t_a > 25 °C and RH > 0.4.     

Thermodynamic performance assessment of an indirect intercooled reheat regenerative gas turbine cycle with inlet air cooling and evaporative aftercooling of the compressor discharge

This study provides a computational analysis to investigate the effects of cycle pressure ratio, turbine inlet temperature (TIT), and ambient relative humidity (φ) on the thermodynamic performance of an indirect intercooled reheat regenerative gas turbine cycle with indirect evaporative cooling of the inlet air and evaporative aftercooling of the compressor discharge. Combined first and second‐law analysis indicates that the exergy destruction in various components of gas turbine cycles is significantly affected by compressor pressure ratio and turbine inlet temperature, and is not at all affected by ambient relative humidity. It also indicates that the maximum exergy is destroyed in the combustion chamber; which represents over 60% of the total exergy destruction in the overall system. The net work output, first‐law efficiency, and the second‐law efficiency of the cycle significantly varies with the change in the pressure ratio, turbine inlet temperature and ambient relative humidity. Results clearly shows that performance evaluation based on first‐law analysis alone is not adequate, and hence more meaningful evaluation must include second‐law analysis. Decision makers should find the methodology contained in this paper useful in the comparison and selection of gas turbine systems. Copyright © 2006 John Wiley & Sons, Ltd.     

The wet compression technology for gas turbine power plants: Thermodynamic model

This paper examines from a thermodynamic point of view the effects of wet compression on gas turbine power plants, particularly analysing the influence of ambient conditions on the plant performance.The results of the mathematical model, implemented in “Matlab” software, have been compared with the simulation results presented in literature and in particular the values of the “evaporative rate”, proposed in Araimo et al. [L. Araimo, A. Torelli, Thermodynamic analysis of the wet compression process in heavy duty gas turbine compressors, in: Proceedings of the 59th ATI Annual Congress, Genova, 2004, pp. 1249–1263; L. Araimo, A. Torelli, Wet compression technology applied to heavy duty gas turbines – GT power augmentation and efficiency upgrade, in: Proceedings of the 59th ATI Annual Congress, Genova, 2004, pp. 1265–1277] by “Gas Turbines Department” of Ansaldo Energia S.p.A., have been taken into account to validate the model.The simulator permits to investigate the effects of the fogging and wet compression techniques and estimate the power and efficiency gain of heavy duty gas turbines operating in hot and arid conditions.     

Improvement of part load efficiency of a combined cycle power plant provisioning ancillary services

According to the type of ancillary service provisioned, operation mode of a power plant may change to part load operation. In this contribution, part load operation is understood as delivering a lower power output than possible at given ambient temperature because of gas turbine power output control. If it is economically justified, a power plant may operate in the part load mode for longer time. Part load performance of a newly built 80 MW combined cycle in Slovakia was studied in order to assess the possibilities for fuel savings. Based on online monitoring data three possibilities were identified: condensate preheating by activation of the currently idle hot water section; change in steam condensing pressure regulation strategy; and the most important gas turbine inlet air preheating. It may seem to be in contradiction with the well proven concept of gas turbine inlet air cooling, which has however been developed for boosting the gas turbine cycles in full load operation. On the contrary, in a combined cycle in the part load operation mode, elevated inlet air temperature does not affect the part load operation of gas turbines but it causes more high pressure steam to be raised in HRSG, which leads to higher steam turbine power output. As a result, less fuel needs to be combusted in gas turbines in order to achieve the requested combined cycle’s power output. By simultaneous application of all three proposals, more than a 2% decrease in the power plant’s natural gas consumption can be achieved with only minor capital expenses needed.     

Effect of various inlet air cooling methods on gas turbine performance

Turbine air inlet cooling is one of many available commercial methods to improve the efficiency of an existing gas turbine. The method has various configurations which could be utilized for almost all installed gas turbines. This paper presents a comparison between two commons and one novel inlet air cooling method using turbo-expanders to improve performance of a gas turbine located at the Khangiran refinery in Iran. These methods have been applied to one of the refinery gas turbines located at the Khangiran refinery in Iran. Two common air cooling methods use evaporative media or a mechanical chiller. The idea behind the novel method is to utilize the potential cooling and power capacity of the refinery natural gas pressure drop station by replacing throttling valves with a turbo-expander. The study is part of a comprehensive program with the goal of enhancing gas turbine performance at the Khangiran gas refinery. Based on the results, it is found that using turbo-expanders is the most economically feasible option and so is recommended to be utilized for improving gas turbine performance at the Khangiran refinery.     

Thermodynamic assessment of advanced SOFC-blade cooled gas turbine hybrid cycle

This paper focuses on novel integration of high temperature solid oxide fuel cell coupled with recuperative gas turbine (with air-film cooling of blades) based hybrid power plant (SOFC-blade cooled GT). For realistic analysis of gas turbine cycle air-film blade cooling technique has been adopted. First law thermodynamic analysis investigating the combine effect of film cooling of blades, SOFC, applied to a recuperated gas turbine cycle has been reported. Thermodynamic modeling for the proposed cycle has been presented. Results highlight the influence of film cooling of blades and operating parameters of SOFC on various performance of SOFC-blade cooled GT based hybrid power plant. Moreover, parametric investigation has also been done to examine the effect of compressor pressure ratio, turbine inlet temperature, on hybrid plant efficiency and plant specific work. It has been found that on increasing turbine inlet temperature (TIT) beyond a certain limit, the efficiency of gas turbine starts declining after reaching an optimum value which is compensated by continuous increase in SOFC efficiency with increase in operating temperature. The net result is higher performance of hybrid cycle with increase in maximum cycle temperature. Furthermore, it has been observed that at TIT 1600 K and compression ratio 20, maximum efficiency of 73.46% can been achieved.     

燃气轮机进气喷水减温技术经济分析及滴径计算

夏季环境温度比较高，燃气轮机的出力和热效率都会受到影响，对压气机喷水减温方法和喷水滴径进行了分析和计算，计算结果表明：温度越高，湿度越小，燃气轮机的输出功率和热效率提高得越多，燃油消耗率也降低得越多，喷水减温的效果越好，此外，高的压比和高的透平进气温度提高了喷水减温效果。     

湿压缩过程的热力学指标及湿压缩燃机循环性能分析

给出了评价湿压缩过程完善性的热力学指标－湿压缩效率的定义，研究了压气机入口喷水湿压缩简单燃机循环的性能特点和规律，并与常规简单燃机循环进行了比较，结果表明湿压缩在提高燃机循环性能方面有很大潜力。     

Gas-turbine performance improvements

The use of gas turbines is increasing for producing electricity, operating airplanes and for various industrial applications. In the last three decades, improvements in gas turbines have shown their success in increasing the amount of energy output from power stations. This is because of advances in metallurgical science and especially the materials used in gas turbines, so that it is possible nowadays to have a very efficient gas turbine with longer working life. This study has concentrated on the improvements of parameters concerned with the performances of gas turbines [i.e. net work output, thermal efficiency, specific fuel consumption (SFC), turbine and compressor efficiencies, compressor's inlet temperature and turbine's inlet temperature]. The data were taken for the Rehab power station in Jordan. The results showed that the plant improvements undertaken involve the study of a wide range of different parameters affecting the performance of the turbine, the most important of which are those which increase the plant's efficiency and decrease the energy cost.     

AE94.3A型燃气轮机进气冷却的应用可行性研究

对AE94.3A型燃气轮机燃气-蒸汽联合循环热力系统平衡进行研究进而发现,与同类型、同等级不同型号机组相比,AE94.3A型联合循环机组余热锅炉的排烟温度较高,排烟余热仍有进一步利用的空间。通过设计优化,扩大省煤器受热面,回收烟气余热加热给水,驱动热水型溴化锂制冷机制冷,用于机组满负荷调峰时的压气机进气冷却或厂房及办公区域空调供冷,对改善燃气轮机联合循环的运行性能,实现能源梯级利用,提高能源利用率和机组经济性运行起到了很大作用。     

A combined power cycle with absorption air conditioning

A cogeneration scheme comprising a combined cycle power plant (CCPP) with an absorption chiller used for space cooling is studied. A parametric study investigating the effect of different parameters, such as steam to gas mass flow rate ratio, fraction of turbine steam extraction, ambient temperature, inlet steam turbine temperature, compressor pressure ratio, and gas turbine (GT) combustion efficiency on the performance of the system has been made. In another aspect of the study, the relative advantage of using CCPP with absorption cooling over thermally equivalent mechanical vapor compression (MVC) cooling is also demonstrated.