基于CFD的空调室内机的数值模拟

利用CFD软件,对分体式空调室内机的内部流场进行数值模拟,研究进口尺寸、面板与换热器间隙以及风道吸气角与空调风量的关系,从中寻找出各参数与空调风量的变化规律,该结果对今后空调的结构设计具有一定的指导意义。     

热交换器布置方式对家用空调器噪声影响的理论分析

从理论上分析了热交换器布置方式对家用分体式空调器室内机所用横流风机系统的流场和声场的影响，说明了圆弧形为理想的布置方式；并对三种具有不同热交换器布置方式的横流风机系统的流场进行了二维数值模拟，结果与理论分析相吻合，较好的预测了家用分体式空调的内部流场。     

基于Fluent的空调室内机风道结构噪声研究

为了研究风道结构对空调室内机噪声的影响,采用Fluent软件对某型空调室内机的流场进行了仿真,仿真过程考虑了热交换器对气流的阻碍作用,将其模拟为多孔介质流动。通过FW-H模型分别对以蜗舌、蜗壳和叶片为噪声源而产生的噪声进行了计算,并与空调室内机噪声测试实验的结果进行了对比,误差在允许的范围内。在尽量保持足够气体流量的前提下,以此模型为基础,通过调整蜗舌间隙与蜗壳前沿长度降低噪声,得到了空调室内机风道结构在此参数上的最优值。     

空调室内机导流板角度对流场影响的大涡模拟

建立分体空调室内机全流场二维模型,对出风导流板位于3种不同角度,叶轮处于高、中、低三档转速下的流场进行大涡模拟。计算结果表明,导流板的存在,一方面可以改变出流流体的方向和分散射流速度轴心区,使室内流场和温度场更加均匀;另一方面当导流板角度不合适时,将阻碍空气流动,导流板端部涡脱落增强。     

换热器结构对室内机风道系统流场特性影响的研究

建立了由贯流风机和换热器组成的空调室内机的三维物理模型,并通过Fluent计算软件对具有四种不同结构的换热器的空调室内机风道系统流场进行了模拟计算,分析了不同换热器结构的风道系统的静压以及速度分布,并统计了流经换热器的气流的分布。为改善空调室内机风道系统、提高空调舒适性提供理论的依据。     

空调器离心风机内流场的PIV试验与CFD仿真对比分析

采用粒子图像测速仪PIV,对柜式空调室内机离心风机叶轮出口内部流场进行了试验研究,揭示了离心风机沿叶高方向叶轮出口速度分布特性.通过CFD数值分析,得到了柜式空调室内机离心风机叶轮出口流动特性,结合PIV与CFD流场对比,验证了CFD方法的正确性.根据CFD数值模拟结果,获得了离心风机入口与导流圈间隙处的流动特性,并设计了一款新的离心风机,在满足生产装配要求的最小间隙条件下,改善了离心风机与导流圈间隙处的流场,降低紊流噪声,提高叶片在叶轮进口段的利用效率.试验测试表明,新设计的离心风机相比原来的离心风机,在不同转速下,风量略有提升,噪声声压级均可降低1 dB/A,功率下降2～5W,同时风叶重量减轻了350g(26.5％),降低了离心风机成本.     

空调用贯流风机进气状态对其性能的影响分析

本文采用计算流体力学(CFD)的方法建立空调室内机流道的数值计算模型,定义了用于描述室内机贯流风机进气口气流方向的参数偏心度Φ.分析了室内机不同类型的前面板和换热器对贯流风机进气口流场状态速度分布,偏心度分布的影响,以及其与室内机性能的关系.为合理布置室内机前面板、换热器等结构,优化贯流风机进气口气流状态,提高贯流风机流量,降低贯流风机噪声提供参考.     

空调器多翼离心通风机整机定常流动的数值模拟

针对柜式空调器室内机多翼离心通风机的特点,采用计算流体动力学方法对其在设计工况时的整机内部流场进行了数值模拟,揭示了其内流场的基本特征.所得到的分析结果对多翼离心通风机的结构设计以及性能优化,提供了理论依据.     

空调器室外机流场和噪声特性

针对分体空调室外机空气侧流场和声场的特点,采用计算流体动力学(CFD)的方法对该系统的气体流动进行数值模拟。详细分析了轴流风扇流道内部和出口的速度分布,并利用激光微粒图像测速(PIV)手段,验证数值模拟结果,模拟结果与PIV测量值吻合较好。在CFD数值模拟的基础上,运用Lowson模型预估系统的离散频率噪声,预估值与测量值吻合较好。CFD技术能够有效地分析室外机空气侧流场特性,并为进行气动声学分析提供依据。     

内藏式空调室内机噪声源诊断研究

对内藏式空调室内机的噪声源进行了全面的分析，运用噪声源诊断的分步运转、频谱分析等方法，对内藏式空调室内机噪声源进行了详细的研究，判断出主要的噪声源，结合实验进行了理论计算，并得出一些有益结论。     

多排孔气垫带式输送机气垫流场动力学分析

利用ANSYS／FLOTRAN软件对气垫带式输送机气垫流场的动力学状况进行了数值模拟分析,得出了不同条件下多排孔气垫流场的压力、速度及能量损失分布规律,为气垫带式输送机设计及运行监控提供了理论依据。     

The humidity effect on air flow rates in a critical flow venturi nozzle

A Critical Flow Venturi Nozzle (CFVN) is usually calibrated using dry air. Yet CFVNs in industrial and calibration service centers are often used to measure flow rates of humid air. Therefore, ISO 9300 provides the calculation method for the humidity effect on discharge coefficients of CFVN. However, since this method is only due to a theoretical analysis, it is important to confirm and check the ISO calculation method for the humidity effect on CFVN with its isentropic analysis by means of an experimental method.In this experiment, three CFVNs with diameters of 0.4, 0.8 and 1.6 mm were calibrated with dry air (with the dew point −40 °C), in a primary air flow standard system with a mercury sealed piston prover, installed at the Korea Research Institute of Standards and Science (KRISS). Another piston prover, a portable dry piston prover, was used as a reference meter and was also calibrated in the primary standard system using dry air. The repeatability of this dry piston prover was confirmed with the deviation being less than 0.05%. The CFVNs were tested with this dry piston prover, using humid air. For air types with high humidity, the humidity effect on flow rates through the CFVNs showed quite significant difference between the experimental results and those from the ISO method with isentropic analysis. But for air types with low humidity, its effect was relatively insignificant.     

回转式空气预热器流场仿真分析

为分析某电厂1000 MW锅炉机组的双密封回转式空气预热器漏风问题,建立局部流体仿真模型。通过理论计算和仿真模拟相结合的方法分析了密封间隙对回转式空气预热器内部流场压力分布、密封压差及漏风率的影响,并针对“三密封”特殊时刻下的流场压力及漏风率变化做了研究。结果表明,密封间隙从2 mm到8 mm的变化过程中,密封片受到的最大压差小于7000 Pa;为使空预器漏风率小于5%,其漏风间隙需要控制在3 mm以内;“三密封”时刻下的漏风率达到了最小值,为3.98%。经过分析总结,为密封片的载荷计算及密封片的改进提供一定的参考。     

Study of moist air flow through the ludwieg tube

The time-dependent behavior of unsteady condensation of moist air through the Ludwieg tube is investigated by using a computational fluid dynamics (CFD) work. The twodimensional, compressible, Navier-Stokes equations, fully coupled with the condensate droplet growth equations, are numerically solved by a third-order MUSCL type TVD finite-difference scheme, with a second-order fractional time step. Baldwin-Lomax turbulence model is employed to close the governing equations. The predicted results are compared with the previous experiments using the Ludwieg tube with a diaphragm downstream. The present computations represent the experimental flows well. The time-dependent unsteady condensation charac-teristics are discussed based upon the present predicted results. The results obtained clearly show that for an initial relative humidity below 30% there is no periodic oscillation of the condensation shock wave, but for an initial relative humidity over 40% the periodic excursions of the condensation shock occurs in the Ludwieg tube, and the frequency increases with the initial relative humidity. It is also found that total pressure loss due to unsteady condensation in the Ludwieg tube should not be ignored even for a very low initial relative humidity and it results from the periodic excursions of the condensation shock wave.     

复合型空气阀流量特性研究

针对空气阀水锤仿真中出现的"虚假"振荡,研究了其产生的原因,分析了复合型空气阀结构特点,重点探讨了怀特法在实际应用中存在的不足,着重介绍了"两阶段"空气阀边界条件,并结合工程实例,论证了该方法可以得到较好的仿真效果.     

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.     

别克汽车空气流量计故障分析与维修

针对别克汽车动力下降、油耗增大、怠速不稳等情况,对产生这些故障的原因逐条排查,最后锁定是由于空气流量计电阻丝受到空气中尘埃的污染造成的。通过清除附着在电阻丝上的污染物,是汽车功能恢复正常,圆满地解决了以上问题;同时,由于修复了故障元件,避免了更换部件总成,节省了费用。     

独立式散热舱冷却空气侧流动特性试验研究

Aiming at the great differences between the detached cooling system and the traditional axial cooling system in aspects like system arrangement, matching relationships between the fan and radiators, the flow field distribution and so on, the detached cooling test bench was designed. Experimental study on the detached cooling system with different radiators’ installation angle and position was carried out on the new test bench. Dynamic characteristics like flow resistance and air speed distribution were measured by piezometer tubes and impeller anemometers. Relatively uneven coefficient of the air speed distribution and system matching curve were calculated and analyzed. The results indicate that when the radiator installation angle is within 30°, with the angle increasing, radiator flow resistance decreases and air speed distribution on the radiator surface is more uneven. When the position relationships between radiators change from opposed form to vertical form, radiator flow resistance increases and air speed distribution is more uneven. The matching area between the fan and the detached cooling system locates in the area where the fan pressure is low and the air flow is large. [ABSTRACT FROM AUTHOR]     

高速磨削楔形区气流场建模与仿真

在磨削加工中,由于砂轮高速旋转在砂轮表面形成空气附面层,特别是在工件与砂轮楔形间隙内,附面层的压力场与速度场急剧变化,且在楔形间隙内出现了明显的返回流,严重制约磨削液的有效注入.利用附面层和流体力学理论建立了平面磨削中楔形区气流场的数学模型,并进行了仿真研究,结果表明:随着砂轮线速度的增大,楔形区的气流压强增加,气流速度也随之增大;随着砂轮与工件间最小间隙的减小,楔形区气流压力、水平方向气流速度以及垂直方向气流速度明显增加,返回流趋于剧烈,流场能量增加.     

A study on the air knife flow with Coanda effect

The coating thickness in hot-dip zinc galvanizing process is of practical importance in determining the quality of product, and its control is often done using the gas wiping through an air knife system. Such a gas wiping method causes a technical problem of splashing from the strip edge to have a harmful effect on the performance of the galvanizing process and the product quality. The present study aims at investigating the effectiveness of Coanda nozzle to reduce the strip splashing problem. A blow-down wind tunnel has been used to experimentally investigate the detailed flow field near the exit of Coanda nozzle and on the strip edge. A computational work has been performed with the help of a computational fluid dynamics method. The three-dimensional, compressible Navier-Stokes equations have been solved using a fully implicit finite volume scheme. The results obtained show that Coanda nozzle effectively reduces the splashing problem, leading to improvement of the whole galvanizing process.