预旋角对径流涡轮背盘射流冷却的影响

采用背盘射流冷却技术对径流式涡轮机热负荷较大的区域进行冷却。采用气热耦合的方法,研究了该冷却技术在预旋角为60°～120°内对背盘冷却特性的影响。结果表明:背盘射流冷却可以大幅提高径流涡轮背盘的冷却效率;预旋角为60°时背盘冷却效果最好,随着预旋角的增加,背盘冷却效果变差;相同径向位置时,冷却系数在0.01～0.02,预旋角每增加15°,背盘平均冷却效率约降低0.003,当冷却系数为0.02～0.04时,预旋角每增加15°,背盘平均冷却效率降低0.016～0.050;冷却流体流入涡轮主流流道后,涡轮机效率受到冷却流体的影响而降低,当预旋角为60°时,冷却流体对涡轮机效率影响最小。     

燃气轮机轮盘预旋冲击冷却特性研究

为提高冷却空气对涡轮轮盘的冷却效果,以某型燃气轮机低压涡轮为研究对象,提出了一种带有预旋冲击的轮盘冷却结构。当冷却空气流过该结构时,冷却空气的流动方向发生改变,提高了轮盘的换热效果,降低轮盘温度进而提高了轮盘强度储备。使用CFX有限元计算软件,对该冷却结构和轮盘进行了气-热-固耦合计算,结果表明:带有预旋冲击的冷却结构比非预旋冲击的冷却结构具有更高效的冷却效率;轮盘在预旋冲击冷却作用下,轮盘换热表面温度降低显著;当冷却空气进口温度降低60 K时,轮盘换热表面温度降低37 K;冷却空气进口压力增加0.39 MPa时,轮盘换热表面温度降低10 K。     

射流孔分布对径流涡轮背盘冷效均匀性的改善

由于可靠性和成本限制,微型燃气轮机涡轮冷却问题尚未形成成熟的解决方案。本文提出了一种简单、高可靠性的径流涡轮背盘冲击冷却技术,并针对由于涡壳几何周向不均匀导致的涡轮背盘冷效不均匀的问题,采用射流孔周向非均匀布置措施对其进行了改善。研究结果表明,在涡舌附近加密射流孔,使其附近对应的冷效极大和极小值均明显提升,冷效均匀性最高改善17.9%。不同非均布射流孔方案对涡轮背盘平均冷效及涡轮整机膨胀比的影响可忽略,对涡轮整机的效率影响不超过0.5%。     

高压涡轮工作叶片综合冷却效果试验研究

为探究不同气动参数对涡轮工作叶片冷却性能的影响,通过试验研究了中温中压工况下高压涡轮工作叶片综合冷却效果分布,主要讨论燃气与冷气的温比、冷气与燃气的质量流量比和栅后雷诺数对综合冷却效果的影响。试验温比变化范围为1.3～2.1,质量流量比变化范围为0.002～0.02,栅后雷诺数变化范围为2.9×10⁵～4.8×10⁵。结果表明：不同气动参数下,综合冷却效果较低位置出现在叶片前缘和尾缘,较高冷却效果出现在叶背1/4和1/2相对弧长位置;当质量流量比从0.008增加到0.014、温比分别为1.40,1.67和1.90时的综合冷却效果分别提高了44.4%,44.5%和34.4%;当温比从1.8增加到2.1、质量流量比为0.008,0.011和0.015时的综合冷却效果分别降低了3.6%,1.6%和4.2%;当栅后雷诺数从2.9×10⁵增加到4.8×10⁵、温比为0.011、质量流量比为1.67时,综合冷却效果降低了20.7%。     

冷却流量对涂层叶片冷却性能影响的数值研究

采用气热耦合数值方法研究冷却流量对热障涂层气冷涡轮叶片冷却性能的影响。分析表明：叶片的冷却效率随冷却流量的增加而增大,但增幅则逐渐下降。吸力面上,附加热障涂层的效果更好。基准工况下,温度的降幅为72.6K,冷却效率的增幅为6.5%。尾部部分区域内部冷却不足,热障涂层阻碍热量从金属表面向流体传递,金属表面温度升高,综合冷却性能下降,因此,只有配合高效的内冷技术,才能达到理想的冷却效果。     

回流式冷却叶片流热耦合数值分析

建立了某型回流式涡轮冷却叶片流热耦合分析模型,采用P-1辐射模型将辐射热流作为源项加入到方程中,对未考虑辐射和考虑辐射的不带热障涂层冷却的叶片进行了流热耦合分析,结果发现,占总燃气质量流量3.76%的冷却气体可以使回流式冷却结构对叶片的降温达到200 K。在入口最高温度为1 655和1 555 K时,通过对两种计算模型下叶片温度分布的比较,发现辐射对叶片壁面温度的影响具有显著性,回流式冷却叶片较易在尾缘叶尖位置形成最高温度点。     

基于响应面模型涡轮叶片冷却性能的数值研究

为了给我国自主研发涡轮叶片提供理论基础,基于试验设计和响应面模型对某型叶片的冷却性能进行了数值研究。对某型涡轮叶片的设计参数进行了试验设计,数值研究了主流出口压力、主流进出口压比、冷气与主流温度比及流量比对叶片表面的无量纲温度分布的影响规律,并根据响应面模型拟合得到了叶片平均无量纲温度的经验公式。结果表明：根据试验设计和响应面模型拟合得到的叶片平均无量纲温度的经验公式有较高的精度;在设计参数范围内,涡轮叶片的平均无量纲温度随着主流出口压力(120～140 kPa)和冷气与主流温度比(0.6～0.7)的增大分别提高了0.57%和2.81%,随着主流进出口压比(1.3～1.5)和冷气与主流流量比(3～8)的增大分别降低了1.14%和3.68%。     

涡轮导叶冷却结构设计及性能分析

按照涡轮传热分层设计流程,对某型燃气轮机高压涡轮导叶进行了冷却结构设计。利用管网设计方法快速得到符合设计要求的基本冷却结构,采用UG建模与自编程序相结合快速生成实体模型,并选取两种典型冷却方案进行全三维气热耦合计算。计算结果表明：两种冷却方案总冷气量基本相同时,前腔冷气流量更大的方案2满足设计要求,其前腔无量纲流量为0.052 7,后腔无量纲流量为0.049 4,叶片表面无量纲平均温度为0.666 7,无量纲最大温度为0.737 1;增大吸力面“簸箕”形状气膜孔的冷气流量,可以有效降低吸力面中后部高温区域的温度;利用管网设计可以快速搜寻合理的冷却结构方案,该设计方法显著地缩短了设计周期。     

非均匀热负荷条件下的平板冲击冷却优化

冲击冷却是涡轮冷却中常见的方式,其优化设计涉及多种几何参数,是典型的高维问题。在冲击冷却结构的设计过程中,需要根据涡轮的热负荷情况适应性地设计冷却结构,以提高综合冷却效率和表面温度的均匀性。实验或数值模拟耗时长且成本高,而代理模型可以快速预测结果,配合计算机自动寻优算法可显著提高设计效率和效果。为了降低优化设计的成本、提高优化过程的效率,以平板冲击冷却为研究对象,同时考虑非均匀热负荷的影响,通过数值模拟构建数据集,建立了基于迭代算子神经网络的代理模型,并使用遗传算法对斑状非均匀热载荷条件下孔位置排布进行了优化。优化结果显示：对于优化潜力较低的结构,优化策略保持了靶板平均温度水平不变;对于优化潜力较高的结构,可以降低靶板平均温度约2.6 K;所研究各结构的表面温度标准差普遍降低70%以上。     

前轮缘封严气流对动叶端区流动及冷却的非定常作用

为研究涡轮盘腔出流的非定常特征,通过求解非定常RANS方程组和SST湍流模型,得到了不同冷气质量流量比(MFR)下高压涡轮级内部的流场特征。结果表明:泄漏流的影响区域主要位于动叶栅内;动静叶片相对运动所带来的非定常干涉使得封严出口周向压差系数增大,MFR为0.4%时发生燃气倒灌,此时泄漏气体与高温主流在端区交替流动;当MFR增大至1%时,燃气入侵得到抑制,且动叶前缘绝热气膜有效度增大近2倍,但该区域的温度脉动加剧;MFR为0.4%时绝热气膜有效度脉动相对高值区域主要位于流道中间,MFR为1%时则位于叶片壁角区域。     

A new approach for enhancing performance of a gas turbine (case study: Khangiran refinery)

There are various methods which are commercially available for turbine air inlet cooling aiming to improve gas turbine efficiency. In this study a new approach has been proposed to improve performance of a gas turbine. The approach has been applied to one of the Khangiran refinery gas turbines. The idea is to cool inlet air of the gas turbine by potential cooling capacity of the refinery natural-gas pressure drop station. The study is part of a comprehensive program aimed to enhance gas turbines performance of the Khangiran gas refinery. The results show that the gas turbine inlet air temperature could be reduced in range of 4–25 K and the performance could be improved in range of 1.5–5% for almost 10 months.     

涡轮叶片蜂巢式冷却结构减阻能力数值研究

先进航空发动机中高耐温能力涡轮叶片通常要以增加冷却系统的流动阻力来提高冷却效果,但由此导致的二次流系统损失增大可能会引起整机性能的下降。为解决该问题,研究了先进涡轮叶片中典型层板冷却结构的内部流动损失产生机理,并针对性地提出两种(进/出气孔平行式和交叉式)低流动阻力的类蜂巢式冷却结构。基于三维数值仿真方法研究了其流动特点和损失特性,并揭示了该结构可以显著减小通道内气流转折角度、抑制旋涡产生和避免多股气流对撞的减阻强化机理。通过与典型层板结构的对比分析,初步验证了在相同的结构无量纲参数和流量下,两类蜂巢式冷却结构的总压损失分别可降低65~66%和67~69%,在高推重比航空发动机涡轮叶片冷却设计上具有较好的应用前景。     

Experimental investigation on impingement/effusion cooling with short normal injection holes

An experimental investigation on cooling performances of integrally impingement/effusion cooling configurations with film cooling holes angled normal to the mainstream flow is conducted. The adiabatic film cooling effectiveness and the overall cooling effectiveness are measured on a polycarbonate test plate and a stainless steel plate respectively. Effects of the blowing ratio (ranged from 0.6 to 2.4), multi-hole arrangement (inline and staggered), hole-to-hole pitch ratio (ranged from 3 to 5) and jet-to-target spacing ratio (ranged from 2 to 4) on the cooling performance are examined. In addition, jet impingement heat transfer is measured to evaluate the dense array jet impingement behaviors with local extraction of coolant via effusion holes. A new parameter named corrected blowing ratio is introduced in the present to evaluate the cooling effectiveness for different effusion or impingement–effusion configurations under a given quantity of cooling air. In an integrally impingement–effusion cooling configuration, multiple jet impingement with local extraction of coolant via effusion holes is able to produce higher overall heat transfer under lower jet-to-target spacing and denser jet array. The action of additional jet impingement heat transfer on improving overall cooling performance is highly dependant on the blowing ratio, multi-hole arrangement and jet-to-target spacing, which seem to be behaved superior in the situations where the film cooling effect isolating the wall surface from the hot mainstream is weak. For an integrally impingement–effusion cooling configuration, the densest hole-to-hole array is favorable in the situations where the coolant mass flow rate per unit area of cooled surface is low. As the coolant mass flow rate per unit area of cooled surface increases, the hole-to-hole pitches could be gradually enlarged to make effective utilization of array jet impingement.     

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.     

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。     

具有新型双层壁结构的透平叶片流热耦合研究

多通道壁面射流冷却结构是一种新型的燃气透平动叶内部冷却结构,具有消耗冷气少、压力损失小等优点。本文构建了简化的壁面射流冷却叶片与GE-E3冷却结构叶片模型,采用流热耦合方法对比研究了其流动与换热特性。结果表明,壁面射流冷却通道内的狭小空间抑制了横流的产生,冷气在冷却通道中形成了流向涡;前缘冷气流道中的大量冷气流经吸力侧冷却区,并从出口压力更小、面积更大的尾缘排出,使得前缘气膜孔出流的冷气流量和动量较小,冷气在叶片外表面的气膜覆盖特性更好;离心力的影响导致前缘冷气流道中叶根处的压力较低,叶根附近的气膜孔出现燃气主流入侵现象。相比于GE-E3叶片,壁面射流冷却叶片的前缘温度和温度梯度都较小,因此多通道壁面射流冷却在前缘具有更优异的冷却特性。     

涡轮叶片尾缘偏劈缝结构二维模型的冷却研究

对叶片尾缘偏劈缝冷却结构的流动与换热进行了二维的数值模拟,研究了涡轮叶片尾缘无量纲长度L／H(即尾缘长度与冷气流出口的高度比)、偏劈缝喷射角a、吹风比M及Reynolds数(RP)对涡轮叶片尾缘平均冷却效果的影响。     

Blade cooling optimisation in humid-air and steam-injected gas turbines

Humidified gas turbine cycles such as the humidified air turbine (HAT) and the steam-injected gas turbine (STIG) present exciting new prospects for industrial gas turbine technology, potentially offering greatly increased work outputs and cycle efficiencies at moderate costs. The availability of humidified air or steam in such cycles also presents new opportunities in blade and disk cooling architecture. Here, the blade cooling optimisation of a HAT cycle and a STIG cycle is considered, first by optimising the choice of coolant bleeds for a reference cycle, then by a full parametric optimisation of the cycle to consider a range of optimised designs. It was found that the coolant demand reductions which can be achieved in the HAT cycle using humidified or post-aftercooled coolant are compromised by the increase in the required compression work. Furthermore, full parametric optimisation showed that higher water flow-rates were required to prevent boiling within the system. This corresponded to higher work outputs, but lower cycle efficiencies. When optimising the choice of coolant bleeds in the STIG cycle, it was found that bleeding steam for cooling purposes reduced the steam available for power augmentation and thus compromised work output, but that this could largely be overcome by reducing the steam superheat to give useful cycle efficiency gains.     

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.