单丝斜热线探针叉杆的气动干扰分析及应用

对单丝斜热线探针在测量垂直来流时的响应进行了研究。实验测量值和Jorgenson理论曲线的偏差表明，当热线处于长叉杆的尾迹中时，测量的有效冷却速度明显低于理论曲线。本文对此提出了修正的方法。实验表明修正的方法可以得到更加精确的结果。     

涡轮叶栅二次流的热线实验研究

采用旋转单丝斜热线测量涡轮平面叶栅出口周期性三维流场,借助于Matlab的Lsqnonlin最优化函数对热线测量数据进行最小二乘拟合以求解三维速度平均量。搭建了亚音速叶栅试验风洞,研究在2种不同进口流量和3种不同的叶片高度下,热线测得的叶栅出口瞬态速度场,并分析叶栅出口的二次涡流动情况。通过比较不同的叶栅工况,发现高速进口较低速进口叶栅尾迹明显,二次流强度较大;而较小的叶高下二次流较为剧烈,导致叶栅出口平面内径向流动速度(u)、垂直于出口平面的轴向速度(w)的迅速增大和出口平面内周向流动速度(v)的显著降低。叶高的减小和气动负荷(速度)的增加都会极大地提高叶栅的二次流损失,本质上都归咎于叶栅横向压力梯度的增大。     

内燃机气缸和燃烧室中紊流运动的测量和紊流参数的计算

摘要本文介绍了用热线风速仪测量内燃机气缸及燃烧室中的紊流运动的方法和数据的采集及处理过程.对紊流参数的计算方法进行了分析比较,讨论了平均速度和紊流强度的不同求法,探讨了采样频率的时窗宽度对计算紊流参数的影响,并对全方位测量及三维测量方法进行了比较.     

热线式空气流量计的研究

热线式空气流量计是测量空气质量流量的一种重要工具。本文设计了一种广泛应用于电控发动机的热线式空气流量计。介绍了热线式空气流量计的理论依据、基本原理、设计和使用方面的问题 ,还对恒温反馈控制和温度补偿作了说明。在电控喷射发动机的汽车上作进气流量检测时 ,不用对进气压力和温度的变化作修正 ,因为它直接测得的是质量流量 ,在用作通用流量计时 ,应对测量区作线性化处理。     

用热线风速仪测量内燃机气缸内的空气流速

用定温式热线风速仪测量内燃机气缸内空气流速时,由于空气温度、压力和补充热线传热损失的变化,必须对热线风速仪的输出进行修正。热线的传热损失依靠供给热线顶端的热量来补充。在内燃机气缸内,供给热线顶端的热量随曲柄转角而变化。前文已经介绍了稳定流动状态下,随空气温度和热线传热损失变化的一种实际修正方法。本文研究压力对空气和补充传热损失之间的对流传热损失的作用。此外还研究了内燃机气缸内供给热线的热量的情况。根据这个研究结果,提出了一种随空气温度、压力及补充热线的热损失的变化而对热线风速仪输出进行补偿的实际方法。     

热线式空气流量计在便携式尾气分析仪中的应用研究

介绍了一种广泛应用于桑塔纳发动机的热线式空气流量计在摩托车工况排放分析仪中的应用.介绍了热线式空气流量计的理论依据、基本原理和使用方面的问题,通过最小二乘法将标准数据进行拟合,作出拟合曲线从而对流量计进行精确标定,再通过标准测试,将流量计的输出结果与标准流量进行比较,从而表明热线式空气流量计在尾气分析仪中能够进行空气流量的准确测量.     

一种热线式空气流量传感器非线性静态模型辨识

根据在流量计标定试验台上对一种热线式空气流量传感器静态标定的数据,用解析建模法和数值建模法建立了热线式传感器的非线性静态模型。文中对比分析了几种模型的辨识精度。结果表明,基于多项式最小二乘和FLANN网络的模型基本相同,能够满足测量的要求,而基于BP网络的模型有着更高的辨识精度。     

基于数据融合的燃料量软测量及煤质发热量在线校正

为了提高燃料量测量的准确性和可靠性,提出了基于数据融合的燃料量软测量方法。主要通过与燃料量相关的测量值和对现场运行数据的统计分析,建立了燃料量软测量模型。利用数据融合技术对多个传感器的数据进行了处理,有效提高了软测量数据的准确性。通过仿真验证,建立的燃料量软测量模型能够较好反映实际燃料量的变化,提高了系统的安全性和可靠性。同时针对煤质时变的现状,通过统计分析56种不同煤质的元素和工业分析结果,发现了低位发热量与理论空气量的关系,及煤质收到基水分和灰分与低位发热量之间的关系,由此提出了两种低位发热量在线校正的方法,以低位发热量的变化表征煤质的变化,优化风煤配比,为性能计算和燃烧优化提供了煤质变化的在线依据。     

用热线风速仪测量内燃机缸内流场时热线探针的方向敏感性研究

在应用热线探针测量内燃机缸内空间流场时，探针的方向敏感性受到许多因素的影响，本文介绍了在气流试验台上对几种结构进行的方向敏感性因素（气流速度，。方向偏角，支杆倾角等）试验。总结了各种因素变化时可能产生的热线测值偏差及其修正方法；观察分析了产生这些偏差的主要原因，主要是气流在热线支柱影响下生成的旋涡和流动死区，最后，介绍了用热线探针在一台二行程直流扫气柴油机上进行的缸内流场稳态分布测量结果。     

一种热线式空气流量传感器非线性静态模型辨识

根据在流量计标定试验台上对一种热线式空气流量传感器静态标定的数据,用解析建模法和数值建模法建立了热线式传感器的非线性静态模型.文中对比分析了几种模型的辨识精度.结果表明,基于多项式最小二乘和FLANN网络的模型基本相同,能够满足测量的要求,而基于BP网络的模型有着更高的辨识精度.     

Ethanol drop impact on an inclined moving surface

This experiment investigates the impact outcomes of ethanol drop on a moving inclined surface at the various inclined angles and moving velocities. The gravity not only can promote the instability of the expanding film at downward flow but also can stabilize the film at upward flow during the drop impact onto a stationary inclined surface. Considering the horizontal moving surface, the surface velocity excites the occurrence of splashing that is toward the opposite direction of surface movement, whereas it suppresses the splashing in the same direction of surface movement. When the inclined surface moves downward at a proper surface velocity, the impact outcomes can be changed from downward splashing to deposition, and furthermore, the direction of splashing also can be changed to upward by increasing the surface velocity. The regime of deposition will be enlarged by an appropriate surface velocity, and this tendency is more obvious with a larger inclined angle.     

超临界CO2倾斜螺旋槽管内冷却换热特性研究

为了提高气体冷却器内换热效率,对不同倾斜角下(-90°,-45°,0°,45°,90°)螺旋槽管内超临界CO2冷却对流换热特性进行了数值模拟,分析了各槽管内的湍动能和速度分布随倾斜角的变化趋势,并研究了不同螺旋角下倾斜角对换热特性的影响。结果表明:浮升力沿流动方向分量和垂直于流动方向分量对流动特性的影响并不相同;在类气区,流体速度对流动特性起主要作用,且换热系数随倾斜角的减小而增大;在类液区,流动特性的主要影响因素是速度梯度,此时换热系数随倾斜角的变化与类气区相反;螺旋角越大即螺旋程度越小,当流体倾斜向上流动时浮升力效应越为显著;当螺旋角为 0.70 rad时,最优倾斜角度为-45°,当螺旋角为0.94 rad时,最优倾斜角为45°。     

Bio-inspired leaf-vein type fins for performance enhancement of metal hydride reactors

Hydrogenation of metals is an exothermic and reversible process. Thus, metal hydride reactors/devices become essentially heat-driven. Excellent heat control in the MH reactor is required to develop metal hydride devices such as H2 storage systems successfully. Few attempts at nature-inspired designs have proven to have good heat transfer capabilities. Based on this idea, the present study investigates novel bio-inspired leaf-vein type fins for the metal hydride reactor. Two reactor designs are proposed for heat transfer fluid flow, namely (i) central straight tube and (ii) narrow trapezoidal channels with 10 kg of LaNi₅ as a sample alloy. Compared to longitudinal finned single tube reactors (LFSTR), these designs provided better heat transmission and temperature uniformity. For LFSTR, Case-1, and Case-2, 90% storage capacity was reached in 210, 145, and 80 s. Different fin configurations, such as parallel, inclined fins, and fins of different thicknesses, are investigated further in the design with narrow trapezoidal channels. The inclined fin configuration shows better performance, and it is further optimized by varying the inclination angle from 3 to 9° and the fin number from 2 to 4. The optimized design with a 7° inclination angle and four fins required 57 s to attain 90% storage capacity and reduced absorption time by 73% compared to LFSTR. The influence of operating parameters such as hydrogen supply pressure, inlet temperature, and velocity of the heat transfer fluid on the performance is evaluated for the optimized design.     

Measurements on a wind turbine wake: 3D effects and bluff body vortex shedding

The velocity field in the wake of a two‐bladed wind turbine model (diameter 180 mm) has been studied under different conditions using a two‐component hot wire. All three velocity components were measured both for the turbine rotor normal to the oncoming flow as well as with the turbine inclined to the freestream direction (the yaw angle was varied from 0° to 20°). The measurements showed, as expected, a wake rotation in the opposite direction to that of the turbine. A yawed turbine is found to clearly deflect the wake flow to the side, showing the potential of controlling the wake by yawing the turbine. An unexpected feature of the flow was that spectra from the time signals showed the appearance of a low‐frequency fluctuation both in the wake and in the flow outside the wake. This fluctuation was found both with and without freestream turbulence and also with a yawed turbine. The frequency expressed as a Strouhal number was shown to be independent of the freestream velocity or turbulence level, but the low frequency was only observed when the tip speed ratio (or equivalently the drag coefficient) was high. The shedding frequency changed also with the yaw angle. This is in agreement with the idea that the turbine sheds structures as a bluff body. The phenomenon, noticeable in all the velocity components, was further investigated using two‐point cross‐correlations of the velocity signals. Copyright © 2005 John Wiley & Sons, Ltd.     

进气道布置对4气门柴油机进气门口三维流场的影响

在稳流模拟试验台上,利用自行研制的单独进气道,4气门柴油机试验缸盖,气门口三维流速测量装置,用热线风速仪测量了不同进气道布置方案下的进气门口三维流场,揭示了进气道的布置对4气门柴油机进气门口三维流场影响的变化规律。进气道布置角度的变化对4气门柴油机各气道气门口流场产生较大影响,螺旋气道布置角度的变化使螺旋气道的各速度大小,切向速度的分布及切向气道的各速度大小发生较大变化。且升程愈大,变化愈明显,切向气道布置角度的变化对螺旋气道和切向气道的速度大小影响均较大。     

On the existence of parallel flow for mixed convection in an inclined duct

The necessary condition for the occurrence of parallel mixed convection flow in an inclined duct is determined by employing the Boussinesq approximation. A sample case involving an inclined infinitely-wide plane channel is discussed to illustrate this condition. It is shown that, according to the necessary condition, parallel flow cannot occur in this case. Indeed, the investigated flow is the superposition of a parallel streamwise flow and a secondary flow. An exponential equation of state for the fluid is assumed and the balance equations are solved analytically to determine the dimensionless velocity distribution, as well as the conditions for the occurrence of flow reversal.     

Optimization of ammonia injection grid in hybrid selective non-catalyst reduction and selective catalyst reduction system to achieve ultra-low NOx emissions

The uniformity of NH₃ in the flue gas is the main factor improving the efficiency during the hybrid selective non-catalytic reduction (SNCR)-selective catalytic reduction (SCR) denitrification process. This work presents the optimized ammonia injection grid (AIG) to enhance the mixing performance and optimize concentration uniformity. A testing ammonia injected facility with a scale of 1:1 is established to experimentally simulate the NH₃ mixing behavior in the tail flue gas duct employing the tracer gas. A novel injection grid with multiple inclined nozzles is proposed to replace the conventional direct-injection type. The flow field and tracer gas concentration field are studied under the three conditions with various inclined jet angles including 0°, 30° and 45°. From results, mixing enhancement between jet and crossflow for the inclined injection grid is achieved. It is also indicated that the inclined angle plays an important effect on jet rigidity and tracer gas dilution. The flow field and tracer gas mixing performances are quantitatively analyzed by using the root mean square deviation coefficient. Multiple jets with an inclined angle of 30° achieved the best mixing performance. Consequently, optimized AIG design has shown effective NO_x control performance in industrial utility furnace.     

燃烧器角度对W型火焰锅炉空气动力场的影响研究

对配备直流缝隙式燃烧器的法国Stein公司360MW机组的W型火焰锅炉进行了冷态模型的空气动力特性研究。利用热线风速仪测量改变燃烧器角度前后炉内的流场速度,得出了不同工况下炉内W型气流的流场图,并对不同工况下的流场气流速度分布规律、炉内气流的充满度、气流行程、炉膛出口处的气流速度偏差等进行了分析,研究了炉内空气动力场的特性和变化规律。     

A study of the ventilation performance of a series of connected solar chimneys integrated with building

A series of connected solar chimneys consisting of an inclined section on the roof and a vertical section near the south wall was studied in a typical two-floor house. Specifically, the effects of the total length and width of the chimney, the inclined angle of the second floor inlet, the length ratio of the vertical to inclined section, and the chimney inclined angle on the chimney ventilation performance were numerically studied. The results showed that the ventilation was improved with the increase of the total chimney length. The air mass flow rate increased firstly then decreased with the chimney width, indicating that there existed an optimal length to width ratio, which was 12:1. Similarly, the mass flow rate increased firstly then decreased with the inclined angle of the second floor chimney inlet. The optimal inclined angle was found to be 4° from the horizontal. At the fixed total chimney length, the air mass flow rate also varied with the length ratio of the vertical to inclined section, and the maximum mass flow rate can be achieved by choosing the longest vertical length within the restriction of the building code. Finally, with the increase of chimney inclined angle, the velocity distribution inside the chimney was improved and the air flow rate increased. These results may provide the theoretical basis for the practical solar building design.     

Lie symmetry analysis and numerical solutions for thermosolutal chemically reacting radiative micropolar flow from an inclined porous surface

Steady, laminar, incompressible thermosolutal natural convection flow of micropolar fluid from an inclined perforated surface with convective boundary conditions is studied. Thermal radiative flux and chemical reaction effects are included to represent phenomena encountered in high-temperature materials synthesis operations. Rosseland's diffusion approximation is used to describe the radiative heat flux in the energy equation. A Lie scaling group transformation is implemented to derive a self-similar form of the partial differential conservation equations. The resulting coupled nonlinear boundary value problem is solved with Runge-Kutta fourth order numerical quadrature (shooting technique). Validation of solutions with an optimized Adomian decomposition method algorithm is included. Verification of the accuracy of shooting is also conducted as a particular case of nonreactive micropolar flow from a vertical permeable surface. The evolution of velocity, angular velocity (microrotation component), temperature, and concentration are examined for a variety of parameters including coupling number, plate inclination angle, suction/injection parameter, radiation-conduction parameter, Biot number, and reaction parameter. Numerical results for steady-state skin friction coefficient, couple stress coefficient, Nusselt number, and Sherwood number are tabulated and discussed. Interesting features of the hydrodynamic, heat and mass transfer characteristics are examined.