叶片反弯曲对涡轮静叶栅流场影响的试验研究

对一典型涡轮静叶型开展了叶片反弯曲对涡轮静叶栅流场性能影响的试验研究。测量了直叶片叶栅和-10°、-20°弯曲叶片叶栅出口流场。结果表明,对该叶型叶栅,随着叶片反弯曲角的增加,叶栅出口通道涡的强度和尺度稍有增大,但位置变化不太明显,尾缘涡有所减弱,叶栅中部和端部横向二次流均增强;随着叶片反弯曲角的增加,叶栅中部损失变化不大,而端部附近损失明显增大,使叶栅总损失增大,直叶栅总损失最小。     

低展弦比涡轮静叶栅叶片正弯曲作用的试验研究

对弯曲叶片研究中代表性的HIT涡轮静叶型重新开展了叶片弯曲对低展弦比涡轮静叶栅流场影响的试验研 究。测量了直叶片叶栅、+10°、+20°和+30°弯曲叶片叶栅的进、出口流场,分析了叶片弯曲对叶栅出口二次流、 总压损失和气流角的影响。结果表明:对该叶型叶栅,叶片正弯曲既不能大幅度降低叶栅二次流损失,也不能改 善叶栅出口气流角沿叶高的分布:叶栅出口二次流动、尾缘涡及壁角涡随叶片正弯曲角的增大而增强,而通道涡 强度和位置变化不大;该研究结果同以往有关文献的研究结果完全不同。     

正/反弯曲对高负荷压气机叶栅流场影响机理

弯曲叶片是改善压气机近端壁流动的有效技术手段之一。为探索叶片弯曲对高负荷压气机叶栅流场的影响机理,在初始高负荷直列叶栅的基础上,设计了不同正/反弯曲水平的叶栅,并采用数值模拟方法对系列叶栅进行研究。研究发现:叶片正弯曲形成了中间静压低、两端静压高的"C"形静压分布,可有效改善压气机叶栅近端壁流场,显著抑制角区分离,使得端壁区域扩压能力提高;正弯曲可增大叶展中部区域负荷,恶化叶中流场,增大流动分离;叶片反弯曲形成了中间静压高、两端静压低的反"C"形静压分布,可显著恶化近端壁区流场,角区分离区增大,端壁区域扩压能力降低,叶中流场有所改善。     

涡轮叶栅通道中的流动显示

在大尺寸低速叶栅传热风洞中对一种高压涡轮导向叶栅的流场进行了流动显示实验研究。分别采用线簇和小球浮动法对五个雷诺数下的叶栅端壁区三维流场、叶片表面和端壁表面的流动进行了显示。实验结果表明 :涡轮叶栅中有强烈的二次流动 ,并存在复杂的涡系 ;三维流动区约占叶栅通道的 40 % ;雷诺数的增大将增强端壁区的三维流动。流场显示图片说明 :叶片吸力面靠近端壁有角涡形成与发展 ,并存在一个三角形区域 ;流场显示的通道涡大小与流场测量结果吻合。本文的实验结果可用于分析端壁表面和叶片表面换热特性的形成机理     

轴向掠叶片对涡轮静叶栅流场气动及声学特性的影响喔

通过数值模拟计算了采用轴向前掠、后掠及径向三种不同叶片型式的涡轮静叶栅流场 ,并根据计算结果分析了各流场流动参数沿流向、径向的分布特点 ,以及轴向前掠涡轮叶栅降噪增效、轴向后掠叶片恶化涡轮静叶栅气动及噪声特性的根本原因     

涡轮叶栅叶型的数字化设计

分析了叶栅内部流场理想分布点的情况，根据流场内速度变化特点，找出其速度和流道通道宽度变化规律，将涡轮叶栅的几何特征离散为一系列的点。突破了传统的作图法和解析法中线型选择的盲目性，减少了以往设计、台架实验，修改，再实验的次数，节约了大量的人力物力。     

大膨胀比局部进气涡轮叶栅流场数值模拟研究

为探究局部进气对涡轮叶栅内部流场的影响机理,本文针对某大膨胀比涡轮叶栅,采用数值模拟方法,对局部进气条件下涡轮叶栅内部流场开展了详细的研究与分析,并研究了不同的出口马赫数与来流攻角下局部进气涡轮叶栅内部流动规律和机理.结果表明:局部进气导致涡轮叶栅中马赫数分布发生变化,在涡轮叶栅进口出现高马赫数区域和弓形激波,进口气流...     

跨音速涡轮叶栅数值计算方法研究与试验验证

以某跨音速涡轮叶栅为对象,研究计算流体动力学数值计算方法,应用CFD软件ANSYS CFX,分析不同网格量和不同湍流模型对数值计算结果的影响,得到最理想且最吻合试验结果的数值计算方法,并与试验结果进行对比分析。结果表明,考虑权衡数值计算结果与试验值吻合度和所耗时间的均衡性,三维网格的S1流面网格量为1万最为合适,SST湍流模型的模拟结果最为理想。     

不同前缘气膜冷气流下某涡轮叶栅流场分析

针对引入前缘气膜冷却的某高压涡轮转子叶片,运用NUMECA进行建模,对引入气膜冷却后的涡轮叶栅流场进行分析,得到了加入前缘气冷后温度、速度、总压等参数的变化。再改变前缘气膜冷气流量,得到了不同流量工况下涡轮叶栅流场的变化情况。通过计算得到结论,冷气流量增大,气膜与叶片壁面分离位置提前,整体流速更快到达最大值且沿着壁面下降更快。冷气流量减小,冷却效率降低;吹风比越大,不同冷气流下冷却效率的变化更为集中;但随着冷气流的改变,总压恢复系数没有发生本质变化。     

串列叶栅和叶片弯曲对角区失速和叶尖泄漏流的耦合作用

为了提高压气机叶栅的气动性能,本文针对高负荷串列叶栅进行数值模拟,研究了叶片正弯和串列叶栅对角区失速和叶尖泄漏流的耦合作用.结果表明,在串列叶栅前叶排存在比较严重的角区失速,叶片正弯能有效控制高负荷串列叶栅中的角区失速,在最优工况叶栅总损失降低了37.6％.串列叶栅中只有"前排叶片弯曲"的方案能取得与"两排叶片都弯曲"...     

立式轴流泵出水流道流场试验研究

大型低扬程水泵采用渐扩出水流道,出水流道水力损失占泵扬程的15%～20%左右。为立式轴流泵设计制作了不同扩散角、无中隔板和有中隔板多种透明出水流道,采用五孔探针测定和丝线观测出水流道内流场,研究流场形成机理,分析流动规律,并与等圆出水管内流动比较。结果表明,由于后导叶出流环量、泵轴旋转诱导、出水弯管二次流和扩散的影响,出水流道内为复杂的螺旋流,断面轴向流速和周向流速分布不均匀、不对称,不均匀程度大于等圆出水管内流动,断面环量有向周边集中的趋势。成果对大型轴流泵装置出水部分的优化水力设计,提高泵装置效率有重大意义。     

涡轮流量传感器特性的试验研究

在高精度的粘度、流量可调整的柴油流量试验装置和水流量试验装置上,对涡轮流量传感器特性曲线进行了试验研究。发现在不同的传感器个体中和不同特性的被测介质情况下,传感器特性曲线在小流量时均具有“锯齿”形变化,其变化幅度达到±0.5％以上;“锯齿”形特性曲线出现第二个峰值所对应的管道Re,随被测流体特性和传感器的不同而不同。对此现象进行了分析,并对涡轮流量传感器的叶轮进行了受力分析。流体流经叶轮时形成边界层流动。边界层流动型态发生转换时,流体对叶轮的旋转力矩会突然增加,可能是出现“锯齿”形变化的原因。     

EXPERIMENTAL INVESTIGATION FOR THE EFFECT OF ROTATION ON THREE-DIMENSIONAL FLOW FIELD IN FILM-COOLED TURBINE

An experimental investigation of three-dimensional flow field in a film-cooled turbine model is carried out by using particle image velocimeter (PIV) in a low-speed wind tunnel. The effects of different blowing ratios (M=1.5, 2) on the flow field are studied. The experimental results reveal the classical phenomena of the formation of kidney vortex pair and secondary flow in wake region behind the jet hole. And the changes of the kidney vortex pair and the wake at different locations away from the hole on the suction and pressure sides are also studied. Compared with the flow field in stationary cascade, there are centrifugal force and Coriolis force existing in the flow field of rotating turbine, and these forces bring the radial velocity in the jet flow. The effect of rotation on the flow field of the pressure side is more distinct than that on the suction side from the measured flow fields in Y-Z plane and radial velocity contours. The increase of blowing ratio makes the kidney vortex pair and the secondary flow in the wake region stronger and makes the range of the wake region enlarged.     

叶轮机械三维弯叶片粘性流场的数值模拟

提出了一种在时间方向具有二阶精度的隐式方法,该方法是关于ｎ个标量方程的隐式算式,算法简单。利用此方法对三维弯叶片定常粘性流场进行了数值模拟,成功地捕捉到了流场中的各种波系和涡系结构。通过与直叶片流场中的涡系结构对比发现,弯叶片降低损失的另一个主要原因是弯叶片能将对二次流起主要作用的通道涡限定在一个稳定的范围内     

锥阀阀口气穴流场的数值模拟与试验研究

采用NNGk-ε湍流模型数值模拟了锥阀阀口的气穴流动。运用工业纤维镜与高速摄像机等组成流场可视化试验系统,多方位地观察了阀口附近的气穴现象,对其进行数字图像处理后,获得了气穴流场的分布信息,与仿真结果比较,吻合良好,表明RNGk-ε湍流模型能有效地描述锥阀等液压元件的阀口气穴流动。同时采用涡流式位移传感器、激光位移器和数字应变测量仪等构成的检测系统,研究了气穴流场诱发的阀体与阀芯振动。     

Rushton桨搅拌槽内平均流场的二维PIV试验研究

用粒子图像测速技术(Particle image velocimetry,简称PIV)对带有Rushton桨叶的,无挡板搅拌槽内的流场进行研究。在叶轮转速240 r/min下,流动的雷诺数Re=1 527时,获取了桨叶处以及桨叶转过5个不同角度处的粒子图像。在对粒子图像进行处理和计算后,得到了相平均速度场和系综平均速度场,并给出了速度分布剖面图。结果表明,所研究的Rushton桨搅拌槽内径向喷射流动沿桨叶垂直方向是非对称的,而是向下方倾斜。在桨叶附近,径向流动速度高。随着流动远离桨叶,径向速度在降低。因此径向喷射流动作用就相当于自由射流:叶轮桨叶喷射出的流体进入周围大量低速运动的流体中,卷吸周围流体,并沿轴向和径向扩散,从而使更多的流体参与混合和反应。所作研究对于深入了解搅拌槽内流场结构具有实际意义。     

EXPERIMENTAL STUDY OF EFFECTS OF OPERATING CONDITIONS ON THE FLOW CHARACTERISTICS OF WATER HYDRAULIC THROTTLE

Experimental investigations are made on the effects of operating conditions on the flow characteristics of throttle when tap water is used as the working media. The researched throttles include cone poppet valve, ball valve, disc valve and dumping orifice. Operating condition includes poppet lift, working media, back pressure, medium temperature, etc. Because the vapourous pressure of water is much higher than that of oil, cavitation is easier to occur in water hydraulic elements and systems, so the effects of operating conditions on the cavitation characteristics of throttle are also researched.     

EFFECTS OF SPLITTER BLADES ON THE LAW OF INNER FLOW WITHIN CENTRIFUGAL PUMP IMPELLER

Analysis on the inner flow field of a centrifugal pump impeller with splitter blades is carried out by numerical simulation. Based on this analysis, the principle of increasing pump head and efficiency are discussed. New results are obtained from the analysis of turbulence kinetic energy and relative velocity distribution: Firstly, unreasonable length or deviation design of the splitter blades may cause great turbulent fluctuation in impeller channel, which has a great effect on the stability of impeller outlet flow; Secondly, it is found that the occurrence of flow separation can be decreased or delayed with splitter blades from the analysis of blade loading; Thirdly, the effect of splitter blades on reforming the structure of "jet-wake" is explained from the relative velocity distribution at different flow cross-sections, which shows the flow process in the impeller. The inner flow analysis verifies the results of performance tests results and the PIV test.     

EXPERIMENTAL INVESTIGATIONS OF CAVITATION EFFECTS ON FLOW CHARACTERISTICS OF SMALL ORIFICES AND VALVES IN WATER HYDRAULICS

The flow characteristics and cavitation effects of water passing through small sharp-edged cylindrical orificesand valves of different shapes in water hydraulics are investigated. The test results using orifices with different aspect ratios and different diameters show that the flow coefficients in the case of non-cavitating flow are larger than that of flow inthe case of cavitation occurrence. The flow coefficients of flow with cavitation initially decrease as Reynolds number increases and ultimately tend to be of constant values close to contraction coefficient. Large aspect ratio has an effect ofsuppressing cavitation. The experimental results about disc valves illustrate that the valves with sharp edge at large opening are less affected by cavitation than that at small opening. Throttle with triangle notch has better anti-cavitation abilitythan that with square notch. The flowrate of the throttle with square notch is significantly affected by the flow direction orthe flow passage shape.