基于Fluent的传热风洞流场品质研究

基于计算流体动力学分析软件Fluent对一台吸入式直流传热风洞内部流场进行了数值模拟,分析了风洞主要部件(整流段、收缩段和实验段)的长度对风洞流场品质的影响,得出实验段两种雷诺数下的速度曲线,发现Re=500时实验段气流发展并保持得更均匀平稳;而Re=104时,实验段气流速度有明显下降,对试验的结果将会产生一定影响。本研究对该类风洞的优化设计有一定参考价值。     

建筑物清洗机器人气流稳定装置设计分析

介绍了采用钢索悬吊的建筑物外墙清洗机器人的基本结构，重点对该机器人气流稳定装置的工作原理和设计计算进行了详细地理论分析，并通过实验验证了分析结论的正确性。     

机翼型叶片防止积灰的机理与技术

分析了锅炉引风机机翼型叶片积灰的原因，介绍了用气流连续吹扫方法防止引风机叶片积灰的实验结果和现场使用效果。说明了喷嘴组的设计过程。     

旋涡气流光整加工的实验研究

介绍旋涡气流光整加工实验装置的设计,研究了喷嘴直径、喷嘴倾角、磨块粒度和磨块直径等因素对加工效果的影响.实验表明,旋涡气流光整加工工艺可有效降低工件内表面的粗糙度,磨块粒度和磨块直径是影响加工效果的主要因素.     

压缩机排气脉动与气流流动实验研究

脉动喷注噪声是一类重要的噪声源,往复式压缩机和旋转机械的排气噪声均属于脉动喷注噪声。该文通过设计实验,采集实验数据对比分析了高压气体流动、气流噪声与压缩机排气脉动的机理和区别,得出压缩机排气脉动的规律和气流流动的特性,为压缩机减震降噪提供实验依据。从压缩机排气口气流脉动沿管路衰减,衰减规律为3 d B/m。压缩机激发频率存在一个最大的脉动激发频率,随着压缩机的转速升高,气流脉动先增大后减小。压缩机产生的脉动大于高压气体流动产生的脉动值,在高压气体排放流动时,随着压比增大,气流流动脉动与流体噪声逐渐接近,最小值为0.47 d B。     

基于CFD数值模拟的粉煤灰脉冲气流干燥器干燥性能的研究

结合理论和模拟实验的方法对粉煤灰脉冲气流干燥器的干燥性能进行分析,设计了适用于粉煤灰颗粒干燥的脉冲气流干燥器。利用商用有限体积CFD分析软件Fluent 6.3对干燥器内的气固两相流场和传热情况进行模拟实验,实验结果与理论值相一致,表明该粉煤灰脉冲气流干燥器实用可靠。     

气固两相剪切流固壁磨损实验装置的设计和流场测试

叙述了气固两相剪切流固壁磨损装置的设计和研制,对装置实验段的气流场进行了展向均匀性、湍流边界层特性的测量和计算,说明该装置满足了设计要求。     

气流式加速度传感器性能的研究

本文根据研制气流式加速度传感器所遇到的实际问题，用理论和实验的方法对其进行了分析和研究。并研究了工艺结构、供电电源电压和环境温度等因素对气流式加速度传感器性能的影响。分析了使气流式加速度传感吕的性能指标得到了提高的因素。     

矿井局扇风机气流稳定器的改进实验

对在气流稳定器中设置导流叶片对矿井局扇风机性能的影响进行了实验研究,其结果为改进气流稳定器的设计,提高矿井局扇风机不稳定工况特性提供了参考依据。     

双焰火焰光度检测器操作条件的优化

采用正交试验和单纯形最优化方法,以较少实验次数获得双焰磷FPD通道和硫通道兼顾灵敏度、选择性和气流用量等因素的优化操作条件。所设计的目标函数适合于双焰操作条件的优化实验。优化操作条件下所得灵敏度及选择性均优于单因子法。考察了气流流速对双焰FPD的火焰状态,响应信号及烃类干扰的影响。     

An optimal design algorithm for centrifugal fans: Theoretical and experimental studies

This study examines the inverse design problem (IDP) of determining the optimal three-dimensional shape of a centrifugal-flow fan based on a desired airflow rate. The desired volume airflow rate can be obtained by multiplying the airflow rate of an existing fan by a constant greater than unity. The geometry of the redesigned fan is generated using several design variables, which enables the shape of the fan to be constructed completely; thus, the parameter estimation technique used in inverse design problems can be used. Finally, prototypes of the original and optimized centrifugal fans are fabricated, and the fan performance is tested based on the AMCA-210-85 standard, which uses calibrated nozzles and pressure taps within a standardized test chamber, to verify the validity of this work. The experimental results demonstrate that by using the fabricated optimal fan, the airflow rate can be increased by 11.8 % and the fan noise can be reduced by 3.5 %; as a result, the performance of optimal fan is greatly improved.     

Associative learning in plants: light quality history may matter

The possibility of associative learning in plants is a topic of ongoing controversy. In one published study, growing pea plants were reported to associate two stimuli (airflow and light) and thereafter use one (airflow) as an indicator for the other (light), similar to dogs in Pavlov’s famous experiments. However, this observation could not be independently repeated. Here we examine a possible reason for the failure of a published reproduction attempt, which used substantially different light quality during plant cultivation prior to experimental treatments than in the original study. This could have resulted in dramatically different growth characteristics. While the relevance of the original report of plant associative learning remains questionable, greater attention should be paid to good documenting and standardizing the light conditions, in particular spectral quality, not only in studies of plant learning and memory, but also in other areas of experimental plant biology.     

亚音速可调气流温度风洞试验台设计

设计研究的气流模拟试验台是一座小型开口高速风洞,可以对试验段温度进行调节。在气动热力方案设计和计算的基础上,采用软件Fluent对风洞收缩段设计参数进行优化设计并进行了试验段流场的模拟计算,模拟计算流场及温度场结果表明设计合理。在优化设计的基础上加工制作了一座风洞,实际测量表明该风洞的流场品质优良,试验段温度符合设计要求。     

A study of signal noise reduction of the mass air flow sensor using the flow conditioner on the air induction system of heavy-duty truck

The mass air flow meter is a critical sensor that works based on thermal hot wire technology, used to determine the fuel to be injected into the cylinder and calculate the fuel-air ratio. In order to measure the airflow rate accurately, the flow should be uniform and smooth upstream of the sensor. The flow disturbance with a short straight length upstream of the flow meter results in the noise of the sensor signal. This noise causes unstable mass flow measurement on the system. Flow conditioners can be used to smooth the velocity profile of the flow. In this study, experimental and numerical methods were used to characterize the performance and operating accuracy of the mass flow meter used in heavy-duty truck applications. The flow conditioners were implemented to smooth the velocity profile around the mass flow meter that was disrupted by bends. The flow structures with and without flow conditioner were examined using Particle Image Velocimetry (PIV) to measure the time-averaged velocity. As well as the validated computational fluid dynamics (CFD) model provides data to understand the flow uniformity effect of the conditioner on the mass airflow (MAF) sensor. The optimization study was performed using a full factorial design of experiment (DOE) for flow conditioner design. A robust methodology was developed for the flow conditioner characteristics and mass airflow sensor implementation on the air induction system.     

基于CFD方法的轿车车身外围流场分析

用CFD方法进行车辆外围流畅的数值模拟已经在汽车车身设计中得到广泛应用。文中使用CFD软件FLUENT对三种不同车速下的轿车简化模型进行外流场数值模拟,根据计算结果对风阻系数、车身等压线分布等气动性能相关信息分别进行定量分析,以此为车身造型设计提供参考依据。     

Static and dynamic performance of a venturi airflow sensor

Venturi-meters have received limited application to the measurement of human airflow. A 3-D printed Venturi airflow sensor (fV) was integrated to a differential pressure sensor for the purpose to document signal quality, dynamic performance during instantaneous flow, and airflow analysis with subsequent calibration for volume measurement. In addition, we assessed these results for potential use in the measurement of human pulmonary ventilation. The fV was developed via drafting software program and 3-D printer (38 mm ID inlet, 12 mm ID constriction, and 23° conical transition sections). The fV was matched to a differential pressure transducer (0–7 kPa input per 0–10 VDC output). The fV was connected in series with a Pneumotachometer (fP) and Turbine airflow sensor (fT), with 1 m length tracheal tubing (ID: 35 mm), separating the devices. Airflow conditions were controlled by an industrial vacuum for constant flow with a manual-operated ball valve connected in series, and a criterion 3 L calibrated syringe for instantaneous flow. Repeated baseline data were collected for signal stability, and to identify the signal-to-noise ratio for signal quality. Airflow estimates and signal quality analysis was performed on repeated constant airflow conditions that spanned the transducer 0–10 VDC output. Repeated syringe manoeuvres that spanned the transducer 0–10 VDC output were used to determine the dynamic performance of the fV. A paired t-test revealed no statistical difference between fV and fP for signal quality across all airflow conditions (p = 0.2028). A paired t-test of dynamic performance data revealed no statistical significance between response times for the fV Vs fP. A calibration method was tested for validation in volume measurements, which resulted in a mean estimate = 3.032 L; CV = 1.14%; n = 83. The fV is easily manufactured with a durable and simple design, making its potential use for ventilation measurement an affordable and reliable technology. These findings provide a reasonable basis to pursue fV technology in applied validation studies, such as inspired and expired ventilation measurement.     

An optimal design for axial-flow fan blade: theoretical and experimental studies

The technique of inverse design problem (IDP) for optimizing the three-dimensional shape of an axial-flow fan blade based on the desired airflow rate is presented in this work. The desired volume flow rate of air can be obtained from the airflow rate of the existing axialflow fan by multiplying it with a constant which is greater than unity. The geometry of the redesigned fan blade is generated using numerous design variables, which enables the shape of the fan blade to be constructed completely; thus the technique of parameter estimation for the inverse design problem can be used in this study. Results show that with the redesigned optimal fan blade, the airflow rate of fan can be increased, thereby improving the performance of the axial-flow fan. Finally, to verify the validity of this work, the prototypes of the original and optimal axial-flow fan blades are fabricated and fan performance tests are conducted with these blades on the basis of the AMCA-210-99 standard. The algorithm used in the present study can be applied to the blade design problem in any propulsion and power systems.     

人体声带的空气动力学建模

人体声带的空气动力学建模研究,对于人们深入了解发声原理,给言语疾病患者提供辅助诊断和治疗建议,有着重大的意义。通过对由一个按四倍比例放大的三维喉物理模型所产生的气流压力场进行研究分析来得到相关的实验数据。研究结果表明,声门和声门入口半径在很大程度上改变了作用于声带表面的压力和声门处的流场分布,进而对发声产生影响。该研究对言语疾病康复,尤其是对声门重建有着潜在应用价值。     

A design model for circular porous air bearings using the 1D generalized flow method

Although the working principles of porous air bearings have been known for many years, most calculation procedures still involve specialized 3D CFD techniques which are not very useful to design engineers who initially require first-order engineering models for feasibility studies. This paper presents a simple design model for a circular porous air bearing based on well-established 1D generalized flow theory. Understanding porous air bearing mechanics is relatively easy with the proposed design model because it captures the essential physical phenomena governing the airflow. Moreover, the 1D model has a very simple architecture that allows easy design synthesis and requires minimal computational requirements. Comparison with experimental data shows accuracy comparable to specialized 3D techniques.     

Computation and comparison of two electric air heaters for industrial use

The computational results of temperature on the surface of ribbed tubular electric heaters and ribbed pipes of thermosiphons have been presented, the desired airflow rate, and installed electric capacity of fan motors for existing and developed electric air heaters has been determined. The computational results of the temperatures of the ribbed pipes have been compared with the experimental data. The novelty of the development has been confirmed by patents obtained on the invention of the electric air-heater design.