Brayton refrigeration cycle for gas turbine inlet air cooling

In this paper, a new approach to enhance the performance of gas turbines operating in hot climates is investigated. Cooling the intake air at the compressor bell mouth is achieved by an air Brayton refrigerator (reverse Joule Brayton cycle) driven by the gas turbine and uses air as the working fluid. Fraction of the air is extracted from the compressor at an intermediate pressure, cooled and then expands to obtain a cold air stream, which mixes with the ambient intake. Mass and energy balance analysis of the gas turbine and the coupled Brayton refrigerator are performed. Relationships are derived for a simple open gas turbine coupled to Brayton refrigeration cycle, the heat rejected from the cooling cycle can be utilized by an industrial process such as a desalination plant. The performance improvement in terms of power gain ratio (PGR) and thermal efficiency change (TEC) factor is calculated. The results show that for fixed pressure ratio and ambient conditions, power and efficiency improvements are functions of the extraction pressure ratio and the fraction of mass extracted from the air compressor. The performance improvement is calculated for ambient temperature of 45°C and 43.4% relative humidity. The results indicated that the intake temperature could be lowered below the ISO standard with power increase up to 19.58% and appreciable decrease in the thermal efficiency (5.76% of the site value). Additionally, the present approach improved both power gain and thermal efficiency factors if air is extracted at 2 bar which is unlike all other mechanical chilling methods. Copyright © 2007 John Wiley & Sons, Ltd.     

Conjugate heat transfer investigation on the cooling performance of air cooled turbine blade with thermal barrier coating

A hot wind tunnel of annular cascade test rig is established for measuring temperature distribution on a real gas turbine blade surface with infrared camera. Besides, conjugate heat transfer numerical simulation is performed to obtain cooling efficiency distribution on both blade substrate surface and coating surface for comparison. The effect of thermal barrier coating on the overall cooling performance for blades is compared under varied mass flow rate of coolant, and spatial difference is also discussed. Results indicate that the cooling efficiency in the leading edge and trailing edge areas of the blade is the lowest. The cooling performance is not only influenced by the internal cooling structures layout inside the blade but also by the flow condition of the mainstream in the external cascade path. Thermal barrier effects of the coating vary at different regions of the blade surface, where higher internal cooling performance exists, more effective the thermal barrier will be, which means the thermal protection effect of coatings is remarkable in these regions. At the designed mass flow ratio condition, the cooling efficiency on the pressure side varies by 0.13 for the coating surface and substrate surface, while this value is 0.09 on the suction side.     

航空发动机涡轮叶片冷却技术综述

本文综述了当前航空发动机涡轮叶片冷却技术的研究情况,着重介绍了气膜冷却、涡轮叶片内流冷却技术和气膜孔流量系数的研究进展,指出了内流冷却和外部气膜冷却相互影响,在冷却结构设计中应予以考虑。     

冷却空气量对涡轮冷却性能影响综述

涡轮冷却技术被广泛应用于航空发动机及燃气轮机涡轮研发中,冷却空气的引气量成为影响整机效率的重要因素之一。本文基于现代燃气轮机及航空发动机涡轮叶片采用外部冷却与内部冷却结合的复合冷却的技术发展背景,综述了国内外在冷却空气量对涡轮叶片冷却性能影响方面的研究进展,分析并总结了冷却空气量对气膜冷却、交错肋冷却以及对综合冷却效率的影响规律,并对未来的研究方向给出了一定的建议。分析表明：对气膜孔形状的探索是未来气膜冷却技术研究的重点;交错肋研究主要处于定性研究阶段,对定量研究方法的探索是目前的发展趋势;对综合冷却效率的研究还处于起步阶段,未来可以从外部冷却和内部冷却之间的相互作用关系方面对综合冷却效率开展进一步的研究。     

用于汽轮机排汽冷却的蒸发式冷凝器模型及性能分析

蒸发式冷凝器兼具传热性能好和节水的优势,在大型动力系统冷却中具有广阔的应用前景。建立了蒸发冷凝器的理论分析模型,提出了蒸发式冷凝器用于冷却小型汽轮机排汽的设计方案;获得了喷淋水温度、空气和蒸汽的焓值在冷凝器内沿程的变化规律,并对喷淋水量、配风量和空气温度等影响冷凝器性能的影响因素进行了分析。研究结果对蒸发式冷凝器在火力发电行业的应用具有参考意义。     

烟气轮机叶片失效分析

分析了烟气轮机叶片失效原因,对叶片裂纹,断口,组织及成分分析的结果表明,叶片失效属共振和冲刷穿孔导致的高周疲劳破裂;叶片涂层结构,组织缺陷分布以及烟气硬粒子是降低叶片使用寿命的重要因素。     

大型燃气轮机透平冷却空气量估算

大型燃气轮机透平冷却空气量一般难以直接获得。本文从燃机总体物质与能量平衡的角度,结合透平一级静叶的冷却模型,给出了一种估算大型燃气轮机冷却空气量的方法,并对GE公司系列燃气轮机和西门子公司V94．3燃气轮机冷却空气量进行了估算。结果表明采用本文的方法估算的燃气轮机透平冷却空气量是合理的。     

Indirect evaporative cooling and economy cycle in summer air conditioning

The air‐side economy cycle has a large application in warm and dry climates, where the simple increase in the amount of outside air supplied to the conditioned space can substantially reduce the cooling load. Although the dry‐bulb economy cycle is the simplest implementation, requiring only a dry‐bulb temperature comparison to operate the air flow rate regulation, the greatest potential in cost reduction is achieved by the wet‐bulb economizer (WBE). Indirect evaporative cooling (IEC), based on energy recovery from the saturated exhaust airflow, is another technique to be applied in the reduction of a building cooling load. Preconditioning the outdoor airflow by IEC actually extends the applicability of the WBE. In such a way, specific synergies can be exploited when WBE and IEC are combined, even in humid climates. On the other hand, the largest benefits can be accomplished only by redefining the control strategy of the outside air flow rate. In the present paper, the outside air flow rate control strategies are described both for simple WBE and for preconditioned WBE cycles. Different regulation regions are defined on the psychrometric chart together with the relative control strategies. The incidence of these regions is evaluated for 14 different European and American climates. Finally, the seasonal cooling energy requirements are determined for the dehumidification by cooling process, which can be considered as mainly responsible for cooling energy costs in the considered localities. Traditional, preconditioned by heat recovery and IEC on the exhaust airflow, WBE and PWBE air conditioning cycles are compared. Copyright © 2003 John Wiley & Sons, Ltd.     

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.     

西门子公司V94.3燃气轮机冷却空气信息推测

作为建立燃用低热值合成气的燃气轮机变工况模型的一个关键步骤，对西门子V94.3燃气轮机冷却空气参数及其分配进行了研究，试图从公开发表的燃气轮机功率、压比、排气温度、三亿透平初温等数据中推测出冷却空气量的分配规律。计算和推测所得到的冷却空气参数和分配规律与燃机净功率以及ISO温度基本吻合。     

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.     

燃气轮机进气冷却技术发展现状及前景分析

分析了燃气轮机进气冷却的必要性，介绍了国内外目前应用的几种燃气轮机进气冷却技术的发展现状，分析了各自特点并对发展前景进行了展望。     

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.     

透平叶顶气膜冷却效果数值研究

采用三维数值模拟方法,研究了GE E3发动机第一级透平动叶叶顶间隙内的气膜流动与换热特性,评估了气膜吹风比M分别为0.5、1.0和1.5时,对叶顶换热系数以及冷却效率的影响.计算结果表明:叶顶气膜冷却空气改变了叶顶泄漏流动特性,随着吹风比的增加,叶顶间隙内的泄漏流动区域不断缩小,从而导致叶顶间隙泄漏量不断减小;随着气膜冷却吹风比的增大,叶顶平均换热系数逐步降低;在M=1时,冷却效果最佳.     

TMT40.3大型风力机叶片气动性能分析

基于BLADED软件平台,对TMT40.3大型风力机叶片的气动性能进行了分析.分析结果表明:TMT40.3大型风力机叶片应用在GL3A风场时的额定功率能达到1 650 kW,所承受的疲劳强度和极限载荷均能满足该款风力机叶片的设计要求,在叶尖速比为7.8～11.4的风能利用系数均在0.46以上,最高可达0.486,具有较好的气动性能和较宽的风速适应范围.     

The interior heat transfer characteristics of gas turbine blade due to sparse film cooling holes

The film cooling technique is one of the most useful cooling methods. At present, the midchord region of gas turbine blades in an aeroengine often adopt a sparse film cooling technique and impingement cooling technique at the same time. So the interior heat transfer characteristics on the inner side of blades due to the sparse film cooling holes have become a very complicated and interesting problem. In this paper, the heat transfer characteristics of impingement‐cooling have been investigated experimentally. Through lots of experimental data, the effect of flow parameters and geometric parameters on heat transfer characteristics has been studied. Correlation equations obtained show good agreement with experimental data. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(3): 197–207, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20052     

Flow structure and heat exchange analysis in internal cooling channel of gas turbine blade

This paper presents the study of the flow structure and heat transfer, and also their correlations on the four walls of a radial cooling passage model of a gas turbine blade. The investigations focus on heat transfer and aerodynamic measurements in the channel, which is an accurate representation of the configuration used in aeroengines. Correlations for the heat transfer coefficient and the pressure drop used in the design of radial cooling passages are often developed from simplified models. It is important to note that real engine passages do not have perfect rectangular cross sections, but include corner fillet, ribs with fillet radii and special orientation. Therefore, this work provides detailed fluid flow and heat transfer data for a model of radial cooling geometry which possesses very realistic features.     

On the technical feasibility of gas turbine inlet air cooling utilizing thermal energy storage

The potential of using thermal energy storage (TES) in the form of ice or chilled water to cool gas turbine inlet air is evaluated for a remote oil field location in the Sultanate of Oman using local hourly typical meteorological year weather data. It is found that under the conditions investigated seasonal TES in chilled water storage tanks or ice bins for the location considered is prohibitively expensive and thus not recommended. Application of partial TES option shows that the cool storage does not result in any noticeable reduction in the chiller size. Hence, TES whether seasonal, partial, or full storage is not a viable option for the considered location, especially in the absence of time‐of‐use utility rate structure. Copyright © 2005 John Wiley & Sons, Ltd.     

仿螺旋肋片内冷通道流动与传热数值分析

利用数值分析方法研究了新型仿螺旋肋片内冷通道的传热与流动特性。采用横截面积为矩形、上下表面带有间断性倾斜矩形肋片叉排且对置的仿螺旋肋片内部冷却通道。分析了在通道宽高比AR=2.9、肋化比Ff/F=2.545、肋高与通道当量直径比e/Dh=0.336、肋间距与肋高比p/e=0.6、肋片与轴面的夹角β=15°及R e在1×104~2×105时的非旋转情况下,R e、肋片与主流方向夹角α等参数对内冷通道强化传热与流动阻力特性的影响。计算结果表明,该仿螺旋矩形肋片作为旋流形成装置起到了迫使流体旋转运动、提高流速和减小层流底层厚度的作用,通道内流体流动达到了预期的螺旋流动效果,通道平均换热系数得到了明显的提高,但同时流动阻力也显著增加。     

微型燃气轮机涡轮背盘冲击冷却特性研究

受可靠性和成本制约,微型燃气轮机冷却技术的发展和应用一直较为缓慢,已成为其进一步提升热效率的主要瓶颈。针对此问题,提出了一种简单可靠的径流涡轮新型冷却技术-背盘冲击冷却,使用气热耦合的方法对该冷却技术的冷却特性进行了仿真研究。结果表明:背盘冲击冷却可以大幅降低径流涡轮背盘的温度。当冷却气体流量为主流的2%时,冷却流体温度从473.0降到323.0 K,背盘平均温度降低了143.0～202.0 K;当冷却温度为323.0 K时,冷却气体消耗量从主流质量流量的1%增加到4%时,背盘平均温度降低150.0～252.0 K。冷却流体流入主流后会对其产生一定的影响,每增加1%的冷却流量,涡轮机效率下降约1%。