低温液氧T型槽密封端面流场数值模拟

以动环、静环和液膜三者为研究对象,建立了低温液氧介质T型槽密封的三维实体模型。利用流体力学计算软件FLUENT对模型进行数值模拟,得到了密封端面液膜流场的压力场分布、剪切力分布和液膜动静环两侧温度场分布,分析了主轴转速、密封介质粘度和压差对开启力、泄漏量和液膜两侧温升的影响。结果表明:动环端面开槽可减少粘性摩擦热,液膜静环侧温升高于液膜动环侧温升,开启力和泄漏量与转速和压差的变化成正比,主轴转速的提高和密封介质粘度的增大都会提高端面温升,压差对温度变化的影响较小。     

机油泵限压阀工作压力反馈控制方式研究

本文阐述了机油泵限压阀工作压力的两种不同的反馈调节方式,并通过试验分析不同的限压阀工作压力反馈方式的发动机机油压力分布规律,总结出机油泵限压阀采用主油道机油压力反馈控制,发动机高速运转时的主油道机油压力受机油温度和油道阻力影响小,机油压力更加稳定,能够对发动机主油道机油压力实施精确的控制,特别是对发动机低温运行工况机油压力过高和旧机油滤清器机油压力过低有很大改善。     

浅析一般压力表、压力真空表和真空表检定依据的新旧规程对比

简述检定一般压力表时,依据JJG52-2013《弹性元件式一般压力表、压力真空表和真空表》与JJG52-1999《弹簧管式一般压力表、压力真空表和真空表》检定规程的对比。     

Proficiency test for effective area determination of a pneumatic pressure balance in Mexico

A pneumatic pressure proficiency test for effective area determination of a pressure balance was performed among 4 accredited calibration laboratories in Mexico. CENAM provided the reference values (making initial and final calibrations) and was the pilot laboratory. The Mexican Accreditation Entity (ema) collaborated. The participants calibrated, by cross floating, a Wika pressure balance model CPB 5000 with accuracy class 0.015% of the reading in the range 0.7–7 MPa. The calibration pressures were 0.7, 1.4, 2.1 3.5, 4.2, 5.6 and 7.0 MPa. For A₀ and A_e, the normalized error equation was used to compare the results of the laboratories with CENAM’s reference values. The results obtained were satisfactory (E_n did not exceed the compatibility limit, −1 ⩽ E_n ⩽ 1).     

CFD study of pressure loss characteristics of multi-holed orifice plates using central composite design

The study on the use of multi-holed orifice plate for measuring flow rate is a growing area of research. As compared to standard orifice plate, multi-holed orifice plates (MO) have number of advantages, such as, these plates require minimum straight piping at the upstream without compromising the pressure losses and provide better accuracy in the measurement of flow rates. In this study, a systematic methodology is adopted for investigating the effect of different geometrical parameters on pressure loss coefficient and values of parameters under investigation varied using central composite design. The geometrical parameters chosen for the study are: (a) Number of holes; (b) Multi-hole Diameter ratio and (c) Compactness of holes. Commercial computational fluid dynamics code (ANSYS Fluent) is employed to perform simulations for 15 different settings of these parameters to analyze their effect on pressure loss coefficient and flow development length at downstream of multi-holed orifice plates. It is found that values of pressure loss coefficient is a strong function of multi-hole diameter ratio, whereas, the flow conditioning properties are strongly affected by the number of holes.     

Experimental research of single-hole and multi-hole orifice gas flow meters

As energy efficiency is becoming more important today due to limited energy resources as well as their rising prices and environment issues, it is crucial to have reliable measurement data of different fluids in production processes. Because of its simplicity, affordability and reliability, orifice flow meters are again becoming subject of numerous researches. Conventional single-hole orifice (SHO) flow meter has many advantages but also some disadvantages like higher pressure drop, slower pressure recovery, lower discharge coefficient etc. Some of these disadvantages can be overcame by multi-hole orifice (MHO) flow meter while still maintaining advantages of conventional SHO meter. Both SHO and MHO flow meters with same β ratios were experimentally tested and compared. Results showed better (lower) singular pressure loss coefficient and lower pressure drop in favour of the MHO flow meter. Experimental data indicates that MHO flow meter is superior to the conventional orifice flow meter, but further research is necessary to make the MHO a drop-in replacement for a SHO flow meter.     

塑料压力盖模具设计与制造

本设计为塑料压力盖模具设计,介绍了压力盖注射模的结构及工作过程,着重介绍了一种新颖的采用斜导柱驱动方法进行侧向抽芯机构的结构设计,并阐述了该模具的工作过程,介绍了注射模设计中采用的强制脱模、滑动型延时顶出机构。涉及到注射机各种参数的选取、零部件的加工方法、注射模的结构及相关的计算问题、特种加工工艺及塑料的回收和利用等方面内容。     

干冰清洗车液压系统压力故障诊断与排除

从液压系统压力冲击、压力过高、压力不足或无压力等方面对干冰清洗车的液压系统中常见的压力故障与问题进行了分析,并且给出了故障排除与问题解决方法,对机械设备液压系统的维修具有一定的参考价值。     

Numerical modeling and experimental verification of compressible squeeze film pressure

The validity of using the Reynolds equation for compressible squeeze film pressure was tested with computational fluid dynamics (CFD). A squeeze film air bearing was instrumented with pressure sensors and non-contacting displacement probes to provide transient measurements of film thickness and pressure. The film thickness measurements also provided input parameters to the numerical prediction. However, numerical results showed a larger load capacity than those suggested from the experimental results. Furthermore, the nonlinear time averaged positive pressure described by the Reynolds equation was not evident in the experimental study.     

卷取机夹送辊安装调整对夹送辊工作压力的影响

分析了热连轧卷取机夹送辊在卷取带钢过程中状态变化,提出现场安装调整的精密准确检测方法,对改善钢卷卷形,提高产品质量起到积极作用。