基于动载荷的齿轮传动系统瞬态弹流润滑分析

综合考虑了齿轮传动系统振动影响、润滑流体的可压缩性 ,以及滑动速度和曲率半径随时间和坐标的变化 ;进行了动载荷下的直齿轮传动弹流润滑数值分析 ,获得了齿轮传动沿啮合线的中心油膜及摩擦系数的分布 ,并给出了 7个特殊啮合点上的压力分布及油膜形状 .     

基于多重网格法的齿轮热弹流润滑特性分析

该文基于多重网格法对齿轮的线接触弹流润滑问题进行求解,探讨不同参数对计算结果的影响,发现油膜压力及油膜厚度对于载荷和弹性模量的变化较为敏感;在对齿轮等温弹流润滑问题求解的基础上,考虑热效应、时变效应及壁面粗糙度对润滑效果的影响。     

r型槽与螺旋槽干式气体密封性能对比研究

为了改善螺旋槽干式气体端面密封性能,提出了一种由螺旋槽和圆弧槽组合的r型槽干式气体密封,并根据气体润滑理论建立了r型槽干式气体密封数值分析模型,定义了r型槽的主要几何结构参数,采用有限元方法求解雷诺方程,获得了端面气膜压力分布,分析了转速、压力对端面开启力、泄漏量等密封性能参数的影响规律,并与螺旋槽干式气体密封进行了对比研究。结果表明,r型槽干式气体密封中圆弧槽有回流作用,与螺旋槽干式气体密封相比有较小的泄漏量;r型槽干式气体密封更适用于低压高速场合。     

压力润滑技术在拉丝中的应用

简述压力润滑技术的工作原理、优点及在铝包钢丝拉拔上的应用。恰当使用压力润滑技术可明显改善润滑效果和产品质量,还可以降低模具磨损速度、提高拉拔速度。压力润滑可通过流体动力学压力涂敷装置来实现,并从其优点分析推广应用的可能。     

基于三维扫描的医疗袜压力分布预测模型研究

基于三维人体扫描获取的人体表面点云数据和拉普拉斯方程,建立医疗袜与腿部接触的服装压分布理论预测模型。选择常用的Ⅰ级、Ⅱ级、Ⅲ级医疗压力袜以及3名在校大学生进行试穿,按照建立的理论模型计算压力袜和腿部接触的压力分布,并采用AMI3037型接触式气囊压力测量系统测试受试者穿着医疗袜时的实际接触压力,验证预测模型的实用性。结果表明,理论值和实测值基本一致,在一定程度上表明基于非接触式三维人体扫描的医疗袜压力分布预测方法可行。     

单螺杆膨化机的物料输送机理研究

为了建立一种有效的单螺杆膨化机内物料输送计算模型,首先从分析螺槽中物料密度变化及物料微元体的受力入手,建立单螺杆膨化机内物料输送的连续方程与运动方程,进一步推导出单螺杆膨化机内的沿程压力和速度分布公式,以及物料质量流率计算公式,以期为单螺杆膨化机的设计和应用提供理论上的支持。     

活塞环自由型线计算方法的比较

论述活塞环径向压力分布函数的一般形式,归纳、总结由径向压力分布求解自由状态型线的方法,对各种计算方法进行了分析比较.实际计算结果表明,各种计算方法之间误差较大,实际应用中采用能量法较宜.     

JWF-A型并条机吸风系统气流流场的数值仿真

为解决JWF-A型并条机吸风系统在生产中存在的问题,采用数值仿真方法分析影响该吸风系统的气流流场、压力场分布和各个吸风口流量大小的因素,并从吸风系统结构参数入手,提出4种改进方案,研究补风口位置与尺寸、风道结构、吸风口开度等对吸风系统流场、压力场和风量大小的影响。仿真计算应用非结构化网格和有限体积法进行计算区域和控制方程的离散,采用标准k-ε模型封闭湍流控制方程。计算结果与实测结果表明：该吸风系统吸风量不足;吸风管道结构不变,补风口位置与尺寸、吸风口开度的变化对系统性能改进作用不大;提出的风道改进方案的吸风量相对于原方案有较大提高,吸风量可以满足要求。     

稀油集中润滑系统在直进式拉丝机中的应用

LZ-9/1200直进式拉丝机减速机采用飞溅润滑方式,润滑效果不好是造成减速机轴承和齿轮损坏的一个主要原因.稀油集中润滑系统采用压力喷射润滑,能够保证拉丝机多个润滑点润滑效果,润滑系统电气自动控制使得减速机润滑管理更简单有效,降低了减速机故障和零件损耗.阐述LZ-9/1200直进式拉丝机采用稀油集中润滑系统的优点,稀油...     

采用压力润滑技术进行钢丝拉拔的应用研究

针对传统拉拔润滑方法易堵塞炉管,钢丝扭转值不达标、扭转断口分层,模具和钢丝表面黏结等问题,采用涂敷器和压力模润滑技术进行改进,并进行理论分析和实际验证。结果表明,采用压力润滑技术进行拉拔,钢丝表面的润滑膜层面质量比用传统的拉拔方法增加50%~80%;低速拉拔时,压力模和涂敷器组合应用比只用压力模效果要好;钢丝的力学性能有所改善,在强度增加的同时,扭转值也增加,且断口有很大程度的改善。     

气压喂棉箱的一种新型配棉头装置

文章介绍了气压喂棉箱的工作原理;新旧配棉头的结构特点和性能,说明新配棉头满足了提高产品质量的要求。     

响应面法优化高静压提高鸡肉糜制品保水性的研究

应用响应面法(Response Surface Methodology,RSM),以高静压压力、酪朊酸钠和变性淀粉添加量为关键因素,建立了高静压提高鸡肉糜制品保水性的二次多项方程模型,优化得到7组制品保水性达到95%～96%的处理参数,其中压力X1=269～340MPa,酪朊酸钠添加量X2=1.7%～2.0%,变性淀粉添加量X3=5.1%～6.0%,验证了该模型有效性。     

The resistance of packed beds of moth gram (Vigna aconitifolius) to airflow

The resistance of packed beds of clean moth gram (Vigna aconitifolius) to airflow was studied at moisture contents varying from 5.64 to 19.42% dry basis (d.b.) and at superficial air velocities ranging between 0.0104 and 0.8321 m s^?1 with bed depths of 0.2–0.6 m and bulk densities ranging from 745 to 875 kg m^?3. The airflow resistance of moth gram increased with increase in airflow rate and bulk density and decreased with moisture content. Results indicated that a 13.78% increase in moisture content decreased the pressure drop by 26.58% whereas, a 7.7% increase in bulk density increased the pressure drop by 43%. The modified Shedd's equation and Hukill and Ives equation were evaluated to see if they predicted pressure drop accurately. Airflow resistance was accurately described by the modified Shedd's equation. The statistical model that related airflow rate and bulk density could fit pressure drop data reasonably well. For loose fill beds an increase in grain moisture content increased the minimum fluidization velocity value from 1.1009 to 1.2391 m s^?1 whereas, for grain beds with 12.47% moisture content, the increase in bulk density decreased the minimum fluidization velocity value from 1.1152 to 1.0306 m s^?1.     

对角度变位齿轮传动削顶量的探讨

深入分析了角度变位齿轮传动中，要同时保证无侧隙和标准顶隙，必须将齿顶削减一段，并借助无侧隙啮合方程式和中心距变动系数y的定义，用数学方法系统地证明了削顶量为(x1 x2-y)m的原因。     

Hydrostatic pressures in wet grinding of soybean with a double-disk attrition mill

Soybean was finely ground with a modified double-disk attrition mill by a wet-grinding process. The hydrostatic pressure in the gap between the rotating and stationary disks of the mill decreased with radial distance between the central inlet and the peripheral exit in the disks. Observed values were in good agreement with theoretical values derived from Bernoulli's equation. The maximum hydrostatic pressure was found at the feed entrance zone of the gap under any given operational conditions. The effects of rotational speed, gap width and soybean feed concentration on the hydrostatic pressure were measured. This implied that increase in hydrostatic pressure from height of feed head and/or increased speed will increase output.     

Analysis and prediction of woven compression bandages properties

Compression bandage (CB) as a porous material consists of elastic textile that exerts pressure on muscles. Three common types of woven CBs are evaluated. Uniaxial stresses of the input yarns and the produced bandage will be tested. This work presents a new method to predict optimum required tension when applying CB on lower leg ankle and mid-calf positions. Experimental measurements and data analysis using NIS software enable to analyze and calculate the bandage porosity during extension using high speed camera. Practical bandage pressure is measured using PicoPress tester. The obtained results will be compared with theoretical compression forces calculated by a modified Laplace’s law equation which predicts graduated compression ranging from 27 to 72?mmHg at the ankle, tapering to 18–8?mmHg below the knee. Results confirm that theoretical pressure is not exactly consistent with practical compression.     

Etude de la perte de charge dans un echangeur de chaleur à surface raclée traitant des produits newtoniens et non-newtoniens

The pressure drop in a scraped-surface heat exchanger operating on Newtonian and non-Newtonian fluids has been studied in relation to the flow rate, the rheological behaviour of the fluids, the rotational speed and the number of blades. For Newtonian fluids, the pressure drop is independent of the rotational speed and can be predicted by the theoretical equation for flow in an annular space modified by a geometrical correction factor taking into account the effect of the blades. For shear-thinning fluids, an increase in rotational speed causes a decrease in pressure drop due to a decrease in the apparent viscosity of the fluid. The authors adapt the method of Metzner and Otto for predicting the power consumption in agitated vessels in order to calculate an apparent shear rate in their exchanger. This apparent shear rate is a linear function of the rotational speed. The parameters of this function are correlated to the operating conditions.     

Comparison of Optimization Techniques for Application to Food Product and Process Development

The super-simplex optimization was modified by incorporating a quadratic regression subroutine. The new algorithm was found to be more efficient in converging at the optimum than the following algorithms: fractional factorial designs, sequential single-factor search, pattern-search method, Morgan-Deming simplex and super-simplex. The efficiency of the modified super-simplex optimization was dependent on the‘fitness of the regression equation to the model equation. Response surface analysis was accurate only when the model equation was quadratic factorial and the boundary covered the optimum. When a constraint was imposed to restrict the search within the boundary, unlike other simplex algorithms including the weighted centroid method, the modified super-simplex algorithm circumvented a problem of the search stalling at the boundary. Since it is not unusual for optimization to be restricted within boundaries, the modified super-simplex algorithm could be useful in optimizing food processing and analysis. When the modified super-simplex technique is applied to -food research, even higher optimization efficiency could be expected by incorporating backward stepwise multiple regression analysis instead of the quadratic regression subroutine with regression equations of set formulae. To obtain a regression equation fit better to the true response surface, all information, including graphics, should be utilized.     

Pressure inactivation kinetics of Enterobacter sakazakii in infant formula milk

Survival curves of Enterobacter sakazakii inactivated by high hydrostatic pressure were obtained at four pressure levels (250, 300, 350, and 400 MPa), at temperatures below 30 degrees C, in buffered peptone water (BPW; 0.3%, wt/vol) and infant formula milk (IFM; 16%, wt/vol). A linear model and four nonlinear models (Weibull, log-logistic, modified Gompertz, and Baranyi) were fitted to the data, and the performances of the models were compared. The linear regression model for the survival curves in BPW and IFM at 250 MPa has fitted regression coefficient (R2) values of 0.940 to 0.700, respectively, and root mean square errors (RMSEs) of 0.770 to 0.370. For the other pressure levels, the linear regression function was not appropriate, as there was a strong curvature in the plotted data. The nonlinear regression models with the log-logistic and modified Gompertz equations had R2 values of 0.960 to 0.992 and RMSE values of 0.020 to 0.130 within pressure levels of 250 to 400 MPa, respectively. These results indicate that they are both better models for describing the pressure inactivation kinetics of E. sakazakii in IFM and BPW than the Weibull distribution function, which has an R2 minimum value of 0.832 and an RMSE maximum value of 0.650 at 400 MPa. On the other hand, the parameters for the Weibull distribution function, log-logistic model, and modified Gompertz equation did not have a clear dependence on pressure. The Baranyi model was also analyzed, and it was concluded that this model provided a reasonably good fit and could be used to develop predictions of survival data at pressures other than the experimental pressure levels in the range studied. The results provide accurate predictions of survival curves at different pressure levels and will be beneficial to the food industry in selecting optimum combinations of pressure and time to obtain desired target levels of E. sakazakii inactivation in IFM.     

圆形筒仓仓壁小变形条件下的变形及应力分析

对用以贮存散体物料的圆形筒仓的仓壁变形和应力分布进行了分析。假定贮料对仓壁的压力和摩擦力按照Janssen公式分布。在小变形条件下根据有矩理论给出了筒仓仓壁径向位移和应力的分布解答。