Pressure and force on a blade row operated in partial admission with different solidity

Partial admission has advantages over full admission for some operating conditions of turbine. However, additional losses such as expansion, mixing, or pumping are generated in partial admission compared to full admission. Thus, an experiment was conducted in a linear cascade apparatus having a partial admission region in order to investigate the effect of partial admission on a blade row. The admission region was formed by a spouting nozzle installed at the inlet of the linear cascade apparatus. Its cross section was circular, and its diameter was 180 mm. The nozzle was set to have a flow angle of 65°. The tested blade was axial-type, and its chord was 200 mm. The experiment was conducted at a Reynolds number of 3 × 10⁵ based on the chord. One blade row of nineteen identical blades was applied to the linear cascade for the partial admission experiment, and this blade row moved along the pitchwise direction in front of the admission region. The operating forces and surface pressures on a blade were measured along the direction at the steady state. For investigating the effect of solidity, three different solidities of 1.25, 1.38, and 1.67 were applied to the blade row. From the experimental results, the maximum rotational force and axial force increased for a larger solidity.     

偏心及部分进汽下密封间隙流体激振力数值研究

喷嘴配汽汽轮机在部分进汽时调节级附近会形成极不均匀的流场,不仅影响调节级动叶轮周力的分布,还会对临近密封间隙内的流场及流体对转子的作用力产生扰动。以某国产300MW汽轮机端部汽封间隙为参考,建立密封间隙CFD模型,求解三维、粘性、可压缩N-S方程,研究了不同进汽方式、偏心情况下流场特性及流体对转子作用力。结果表明:部分进汽的位置、转子的偏心距及两者的相对位置对汽流力的大小、方向和变化趋势产生了较大的影响。在某些部分进汽情况下,偏心距增大也会减小汽流力。     

Flow Field Characteristics of the Rotor Cage in Turbo Air Classifiers

The turbo air classifier is widely used powder classification equipment in a variety of fields. The flow field characteristics of the turbo air classifier are important basis for the improvement of the turbo air classifier's structural design. The flow field characteristics of the rotor cage in turbo air classifiers were investigated under different operating conditions by laser Doppler velocimeter(LDV), and a measure diminishing the axial velocity is proposed. The investigation results show that the tangential velocity of the air flow inside the rotor cage is different from the rotary speed of the rotor cage on the same measurement point due to the influences of both the negative pressure at the exit and the rotation of the rotor cage. The tangential velocity of the air flow likewise decreases as the radius decreases in the case of the rotor cage's low rotary speed. In contrast, the tangential velocity of the air flow increases as the radius decreases in the case of the rotor cage's high rotary speed. Meanwhile, the vortex inside the rotor cage is found to occur near the pressure side of the blade when the rotor cage's rotary speed is less than the tangential velocity of air flow. On the contrary, the vortex is found to occur near the blade suction side once the rotor cage's rotary speed is higher than the tangential velocity of air flow. Inside the rotor cage, the axial velocity could not be disregarded and is largely determined by the distances between the measurement point and the exit.     

汽轮机再热后级内颗粒冲蚀特性

汽轮机再热后级内叶片受到固体颗粒冲蚀,严重影响着汽轮机的安全经济运行。以某超临界汽轮机再热后第1+1/2级(第一级与相邻级的喷嘴)扭叶片为研究对象,通过拉格朗日法模拟不同粒径颗粒三维运动轨迹,并采用Finnie冲蚀模型,研究不同动静轴向间隙及不同负荷下颗粒对叶片的冲蚀特性。结果表明,由于动叶高速旋转,颗粒撞击到动叶时会获得与主流方向相反的速度,进而又反弹回静叶。较大粒径颗粒在动静叶片轴向间隙内"反复反弹"是造成再热后级内冲蚀的主要原因。适当增大动静轴向间隙可以有效地减少反弹回静叶的颗粒数量。当动静轴向间隙为5 mm时,反弹回静叶的颗粒为10%,轴向间隙增大为8 mm时,没有颗粒反弹回静叶。当机组负荷降低时,固体颗粒撞击叶片后的反弹角增大、反弹回静叶的数量增多,颗粒在动叶和下级静叶轴向间隙内反弹后,只有极少颗粒能够流出下级静叶。     

风力机动态偏航时对风轮气动性能影响的数值模拟研究

本文是对动态偏航风力机输出功率和风轮表面的压力分布进行了研究。以某S翼型风力机叶片为研究对象,采用有限元方法,模拟叶片在额定工况下以10°/s的旋转速度从正对来流风开始顺时针匀速偏转30°。在动态偏航过程中取10°,20°两个偏航角位置时的风轮表面气动力及5°,10°,15°,20°,25°,30°六个偏航角下风轮的输出功率分别进行气动力及输出功率对比,结果发现:同一偏航角下,风力机动态偏航时,三支叶片间存在不平衡气动力;同一偏航角同一叶片相同径向位置,风轮动态偏航时压力面与吸力面的压强差小于风轮静态偏航时压力面与吸力面的压强差。风力机发生动态偏航时,风力机受气动力变化幅度较大,输出功率会较大波动。     

动静干涉下低压涡轮非定常气动载荷研究

为研究动静干涉下轴向间距和尾缘锯齿结构对低压涡轮叶片非定常气动载荷的控制作用,对高效节能发动机(energy efficient engine,简称E3)低压涡轮最后一级的内部流场进行了数值仿真,研究了不同轴向间距和静叶尾缘锯齿结构两种情况下,下游动叶表面非定常气动载荷的变化规律。研究发现：增大轴向间距可以加强尾迹与主流的掺混,消除气流不均匀性,削弱下游动叶表面的非定常气动载荷;静叶采用尾缘锯齿结构不仅可以加强尾迹与主流的掺混,同时还会改变尾缘处的涡结构,对下游动叶前缘产生破坏性干涉效应,使其最大载荷波动降低约30%,减少静叶尾迹速度亏损75.7 m/s,还能适当提升涡轮的流通能力和时均效率。与采用直尾缘静叶的模型相比,采用锯齿尾缘静叶不仅能大幅度地改善涡轮的转静干涉效应和气动性能,还能在不影响涡轮效率的前提下,将涡轮轴向间距缩短10%。     

叶根倒角对跨音轴流压气机气动性能的影响*

为了获得叶根倒角对跨音轴流压气机气动特性影响规律,研究充分考虑了加工工艺及气动影响两方面,用倒角半径及最小角度两个参数确定倒角几何。研究基于Rotor37分析倒角参数对叶片几何的影响,并从整体性能及内部流场细节两方面对转子气动特性变化进行详细分析,获得了倒角参数变化对气动性能的影响规律。研究结果表明,相对于最小角度,倒角半径是影响转子性能的主要因素;倒角的存在不仅使得叶片根部马蹄涡的分布发生改变,且影响了出口通道涡的强度和尺度。此外倒角存在改变了叶根处的压力分布,使得前缘来流附面层有所增厚,导致根部的做功能力及转子性能下降。     

工业汽轮机调节级部分进汽瞬态数值研究

针对采用喷嘴调节的汽轮机调节级效率和安全性问题,基于时均的N-S方程,采用六面体结构化网格和有限容积法,对某机组调节级内部流动进行了数值计算。给出了不同工况下调节级内部压力和速度分布图,分析了4阀开和3阀开工况下调节级内部流动。给出了动叶旋转一周扭矩的变化,并将非定常扭矩进行了傅里叶变换,得到了频谱图。研究结果表明,部分进汽使调节级内部流动不均匀,4阀开,动叶所承受最大瞬时扭矩是进汽弧段平均扭矩的2.2倍,3阀开,动叶所承受最大瞬时扭矩是进汽弧段平均扭矩的1.8倍,这可以为调节级动叶安全性校核提供参考;频谱图显示,动叶受到与转速相关的低频激振力;3阀开工况下调节级的效率比4阀开工况下降低7%。     

风电机叶片设计参数的整体优化

分析叶片在非设计点的气动性能和功率控制方式,研究叶片在实际运行风速范围内的风能利用系数,建立不同优化模型,设定实度最小或能量输出最大为优化目标,运用数学规划和遗传优化算法,对叶片气动参数进行优化设计,得到了1.2MW风机叶片整体优化的设计结果。经对比和仿真计算,可知整体优化后,叶片气动性能得到改善。     

Enhancement of wind turbine aerodynamic performance by a numerical optimization technique

Sectional aerodynamic design optimization was performed to enhance the aerodynamic performance of horizontal axis wind turbine rotor blades based on a computational fluid dynamics technique. The proposed sectional optimization framework consists of airfoil section contour modeling by the PARSEC shape function and a modified feasible direction search algorithm. To enhance the aerodynamic performance of wind turbine rotor blades, the objective of the design framework was set to maximize the lift-over-drag ratio for each design section. A two-dimensional Navier-Stokes flow solver coupled with a transition turbulence model was used to evaluate the aerodynamic performance during the iterative design optimization procedure. The sectional flow conditions were extracted from the flow of a three-dimensional rotor blade configuration. The design framework was applied to the National Renewable Energy Laboratory Phase VI rotor blade. The design optimization was conducted at nine spanwise sections of the rotor blade. To validate the present methodology, the aerodynamic performances of the original baseline rotor and the rotor after the design optimization were compared by using a three-dimensional Navier-Stokes flow solver. It was found that approximately 11% of torque enhancement was achieved after the aerodynamic shape design optimization.     

板型及机翼型对旋轴流通风机气动性能测试及比较

采用模型性能试验方法,对板型及机翼型叶片的对旋轴流通风机的气动性能进行了比较,通过测量这两种叶型的风机在不同叶片安装角下的流量、全压及轴功率,得到了叶片型线及安装角对风机气动性能的影响规律。试验结果表明机翼型叶片在全压效率、稳定运行范围及高效运行范围比相应的板型叶片具有优越性;在设计工况附近,机翼型风机的第一级叶轮安装角对气动性能的影响较大,而板型风机的第二级叶轮安装角对气动性能影响较大。     

对旋式轴流风机全角度整机数值模拟及试验验证

通过对对旋式轴流风机采用不同的湍流模型进行多角度和多工况点整机数值模拟,并对比试制样机试验数据,探索湍流模型的规律性,为对旋式轴流风机全角度整机数值模拟下湍流模型的合理选择,提供了一定的依据;通过全角度整机数值模拟,有效地验证了全角度下风机的气动性能特性和设计工况点的合理性,并对I、II级叶轮叶片安装角进行正交数值模拟试验,筛选出I、II级叶轮叶片最佳匹配角度,通过进一步分析最佳匹配角度的气动性能,探索了两级叶轮功率最佳匹配关系。     

LP compressor blade vibration characteristics at starting conditions of a 100 MW heavy-duty gas turbine

In this paper are presented the blade vibration characteristics at the starting conditions of the low pressure multistage axial compressor of heavy-duty 100 MW gas turbine. Vibration data have been collected through strain gauges during aerodynamic tests of the model compressor. The influences of operating modes at the starting conditions are investigated upon the compressor blade vibrations. The exciting mechanisms and features of blade vibrations are investigated at the surge, rotating stall, and buffeting flutter. The influences of operating modes upon blade dynamic stresses are investigated for the first and second stages. It is shown that a high dynamic stress peak of 120 MPa can occur in the first stage blades due to resonances with stall cell excitations or with inlet strut wake excitations at the stalled conditions.     

Turbine blade vibration due to partial admission

A method is given for analyzing the vibrations of turbine blades during partial admission. The combined effects of shock loading as the blades enter and leave the arc of admission, and nozzle wake loading in the arc of admission are included. By separating these two effects, the dependence of blade stress on natural frequencies, running speed, number of nozzles, number of blades per row, number of blades per group and damping is illustrated. Apparatus for determining experimentally the exact nature of the steam loading acting on the blades is described.     

不均匀来流作用下汽轮机动叶片的动态特性分析——非定常欧拉解法

通过三维欧拉非定常流场与弹性叶片动态响应的迭代计算,研究汽轮机叶片—流场系统的稳定性及其动态特性。对某一蒸汽轮机动叶片排,有一定的流量范围内,根据各自工况下静叶出口的不均匀流场,求得动叶片—流场系统的动态特性,判别其运行的稳定性范围。     

Aerodynamic shape optimization of wind turbine rotor blades considering aeroelastic deformation effect

An aerodynamic shape optimization framework of two modules is developed for improving the aerodynamic performance of wind turbine rotor blades. The first module conducts CFD-based aeroelastic analysis for the complete blade configuration to evaluate the turbine performance and to extract the sectional flow conditions at selected blade sections. The second module performs 2-D shape optimization of blade sections to maximize the lift-to-drag ratio under given sectional flow conditions. When the optimization is completed for all selected blade sections, the performance and sectional flow characteristics of the new blade reconfigured from the optimized sections are evaluated again by the CFD-based aeroelastic analysis. The above procedure is repeated until the solution converges satisfactorily. Applications were made for the NREL phase VI and the NREL 5MW reference wind turbines. The results showed that the optimization framework can be effectively utilized in enhancing the aerodynamic performance of wind turbine blades.

     

Axial-flow pump blade-element loss and deviation angle prediction

Determination of blade row fluid flow total-pressure loss and turning distributions in an axial-flow pump over a range of operating conditions is discussed. Included are a review of related research, correlations of pump rotor data and the results obtained using these data correlations with a computer program for pump off-design performance prediction. A number of the important problems related to determining fluid loss and turning information in a turbomachine and some of the consequences of imprecise prediction are pointed out.     

某热电厂空冷200MW汽轮机改造

通过采用新型调节级静叶栅、高压静叶栅、叶顶汽封、710mm末级叶片对机组进行改造,电厂运行效果明显,汽耗和热耗均有不同程度地下降,在主蒸汽量不变条件下,出力得到了提高。背压适应范围扩大为4．5—34kPa,机组经济性达到国内同类型机组先进水平,可以保证夏季满发和机组的供热要求,全年安全运行。     

静叶尾迹对压气机动叶非定常气动载荷的影响

以某型航空发动机压气机转子系统为研究对象,建立了单级叶盘的三维结构及流场模型。通过对滑移网格(sliding mesh,简称SM)方法与运动坐标系(moving reference frame,简称MRF)方法在计算耗时和收敛性方面的比较,证明了运动坐标系方法的准确性和高效性。考虑前一级静叶尾迹的影响,求解压气机内部在不同时刻的流动特性,得到静叶尾迹对动叶流场的非定常干扰情况。经过对压气机叶顶和轮毂、动叶压力面和吸力面非定常气动载荷的分析发现:在动叶流场的前缘形成了较主流区压力和速度较低的不均匀流场,且在动叶前缘叶顶位置受到的气动载荷最为显著;动叶压力面和吸力面气动载荷的分布规律相反,从叶顶至轮毂、前缘至尾缘,压力面非定常气动载荷的大小和波动幅度逐步递减,而吸力面却与其相反,呈现出逐步递增的趋势。该研究为某型航空发动机压气机叶盘转子系统的动力学设计提供了理论依据。     

考虑轴向速度非均匀性的微型轴流风扇扭叶片设计及其对气动性能的影响

通过推导微型轴流风扇叶片出口轴向速度沿叶高的分布方程,提出了一种考虑轴向速度非均匀性的扭叶片设计方法.通过CFD技术,数值研究了利用该方法所设计的各种形式扭叶片的气动性能及其变工况时的气动特点,并比较了工作于"自模区"与"非自模区"风扇的气动性能的差异.研究结果表明:与"自模区"的风扇相比,就"非自模区"的风扇而言,压力曲线没有最高压力点,随流量减少而压力几乎呈线性增加,且无失速点.效率曲线则显得更为平坦;按"刚性涡"设计的扭叶片虽效率低,但风压高;提高叶轮的轮毂比有助于提升风扇压力与效率.