螺旋流对环形射流泵性能影响的数值模拟

为了提高环形射流泵的输送效率,本文提出了一种利用导叶结构形成螺旋流的螺旋流环形射流泵。利用数值模拟的方法研究不同工作压力下的螺旋流环形射流泵和原型泵的速度、压力和湍动能分布计算结果,来分析螺旋流对环形射流泵的性能影响。数值模拟结果表明：在工作压力为130 kPa时,螺旋流使环形射流泵的流量比增加了43.1%,压力比降低了22.8%。螺旋流降低了环形射流泵喉管内的静压,更容易引起空化。螺旋流使得环形射流泵的效率在工作压力低于160 kPa时大于原型泵。螺旋流环形射流泵内具有更大的湍动能分布区域。随着工作压力升高,两种结构的环形射流泵湍动能分布差别减小。导叶阻力对螺旋流环形射流泵的效率有着重要的影响。     

基于喉部参数控制的离心泵导叶扩散度研究

为研究导叶扩散段无量纲参数对离心泵水力性能的影响,通过控制导叶喉部参数设计出5种导叶扩散度方案,采用雷诺时均N-S方程和RNGκ-ε湍流模型对离心泵进行全流场计算,对比分析了不同扩散度方案对上游叶轮、导叶本身以及下游压水室水力性能的影响,并验证了数值分析的可靠性.研究表明:导叶扩散度对上游叶轮水力性能较大,叶轮效率随导...     

硬质聚氨酯泡沫在多轴压缩试验下的力学特性研究

硬质聚氨酯泡沫广泛应用于吸能装置。为研究硬质聚氨酯泡沫在多轴载荷下的力学响应,应用静水压试验和围压试验对其进行多轴压缩试验,分析其力学特性和吸能特性。结果表明：在静水压试验中,泡沫材料经历了弹性区域、平台区域和密实化区域三个阶段,相应的体积弹性模量、平台应力和单位体积吸能量均比单轴压缩试验的高;而在围压试验中,泡沫仅经历弹性阶段和峰值后阶段,无明显的平台区域和密实化区域。峰值偏应力随着围压增加而减少,但当围压超过一临界值时,偏应力-轴向应变曲线表现出一定的随机性,丧失了进一步承受轴向载荷的能力。基于试验数据和微分硬化屈服面模型,获得不同塑性应变下硬质聚氨酯泡沫的屈服面。     

Numerical analysis of flow characteristics of a swirl-stabilized premixed burner with different swirl vane configurations

This study numerically investigates the flow and combustion characteristics of a swirl-premixed burner with a curved vane swirler (i.e., curved type) to reduce the pressure loss of the burner nozzle with a conventional vane swirler (i.e., flat type). For the curved type swirler, the pressure loss is decreased by 35 % due to the inhibition of flow separation at the vane, and NO_X emission is reduced by 69 % because fuel-air mixing is enhanced at the flame front, leading to more uniform fuel distribution toward downstream. In addition, the characteristics of the jet penetration are analyzed because the jet behavior is crucial to fuel-air mixing. The jet trajectory in non-swirling flow can be reasonably predicted by a conventional formula, but it is difficult to predict the jet trajectory in swirling flow by this formula because of the effect of a radial pressure gradient formed by the swirling flow.

     

<Emphasis Type="Italic">SMART Robotic System for 3D Profile Turbine Vane Airfoil Repair</Emphasis>

The 3D profile airfoil of a turbine vane under overhaul can be severely distorted. The current manual repair to restore its original shape is time and labour intensive, and also produces inconsistent quality. Automation of such a process can lead to a significant cost reduction and improved quality. This paper reports on a system and the process development of a SMART robotic system for automatically grinding and polishing vane airfoils. . ID="A2"Correspondance and offprint requests to: Dr Libo Zhou, Department of Systems Engineering, Ibaraki University, Nakanarusawa 4–12–1, Hitachi-shi, Ibaraki-ken, 316–8511, Japan. E-mail: lbzhou@dse.ibaraki.ac.jp     

On the intermittent spray characteristics

The quality of spray atomization ejected from an injector has a definitive influence upon the engine’s performance. Furthermore, considerable attention to the Earth’s environmental pollution is increasing now more than ever before. This experimental investigation has been carried out to clarify the characteristics of the intermittent spray using a pintle type gasoline fuel injector. Both the image processing system and the Phase Doppler Anemometer are utilized for the visualization of a spray behavior and the simultaneous measurements of dropsizes and their velocities, which have been conducted at the axial downstream from the injector exit plane. The fuel injection duration was fixed at 3ms and the injection pressure was varied from 250 kPa to 350 kPa. For a high injection pressure of 350 kPa, the spray tip arrival time was fluctuated at the vigorously disintegrated regions. It evidently shows a linear correlation between the axial velocity and the fuel drop size farther downstream.     

An experimental work on the effect of injection molding parameters on the cavity pressure and product weight

The injection molding process is one of the most efficient processes where mass production through automation is feasible and products with complex geometry at low cost are easily attained. In this study, an experimental work is performed on the effect of injection molding parameters on the polymer pressure inside the mold cavity. Also, the effect of these parameters on the final products' weight is studied. Different process parameters of the injection molding are considered during the experimental work (packing pressure, packing time, injection pressure, injection time, and injection temperature). Two polymer materials are used during the experimental work (polystyrene (PS) and low-density polyethylene (LDPE)). The mold cavity has a cuboidal form with two different thicknesses. The cavity pressure is measured with time by using pressure Kistler sensor at different injection molding cycles. The results indicate that the cavity pressure and product weight increase with an increase in the packing pressure, packing time, and injection pressure for all the analyzed polymers. They also show that the increase of the filling time decreases the cavity pressure and decreases the product weight in case of PS and LDPE. The results show that the increase of packing pressure by 100 % increases the cavity pressure 50 % in the case of PS and 70 % in the case of LDPE. They also show that the increase of injection pressure by 60 % increases the cavity pressure 36 % in case of PS and 90 % in case of LDPE at an injection temperature of 220 °C. The results indicate that process parameters have an effect on the product weight for LDPE greater than PS. The results obtained specify well the developing of the cavity pressure inside the mold cavity during the injection molding cycles.     

The Lubrication characteristics of the vane tip under pressure boundary condition of oil hydraulic vane pump

The Lubrication Mode of line contacts between the vane and the camring in an oil hydraulic vane pump has been investigated. First, the variations of the radial force of a vane were calculated from previous measurements of dynamic internal pressure in four chambers surrounding a vane. Next, the lubrication modes were distinguished with Hooke’s chart, which is an improvement over Johnson’s chart. Finally, the influence of the boundary conditions in the lubrication region on the fluid film lubrication was examined by calculating the film pressure distributions. The results showed that the lubrication mode of the vane tip exists in the rigidvariable-viscosity region, and that discharge pressure higher than 7 MPa greatly affects the oil film pressure in the small and the large arc section because of the Piezo-viscous effect.     

Influence of arm soft tissue on non-invasive blood pressure measurements: An experimental and mathematical study

We investigated the possible influence of arm soft tissue on the accuracy of blood pressure measurements performed with indirect techniques. To this end we measured arterial pressure repeatedly on 36 patients by means of an automatic procedure based on the Riva-Rocci method and controlled by a personal computer. Measurement results point out that, in about 1/3 of patients, squeezing of arm tissue by repeated cuff pressure measurements can cause a significant decrease (0.66–1.33 kPa, i.e. 5–10 mmHg) in the estimated systolic and diastolic pressure values. This phenomenon may be ascribed to alterations in the elastic properties of arm tissue.

Mathematical analyses, performed with a finite element model of the upper arm, show that pressure transmission across the arm can be significantly affected by the elastic parameters of the soft tissue, especially by a decrease in tissue compressibility. Decreasing the Poisson ratio from 0.45 to 0.3, in fact, causes a fall in pressure transmission as high as 1–2 kPa (7.5–15 mmHg).

In order to achieve individual identification of the elastic parameters of arm tissue, we developed an original non-invasive experimental procedure, based on two contiguous cuffs placed around the same upper arm and separately inflated. The possibility of achieving a unique theoretical identificability of the elastic parameters with this procedure is demonstrated.     

The Tribological Behaviour of Fe–28Al–5Cr/TiC Under Liquid Paraffine Lubrication

The tribological behaviour of Fe–28Al–5Cr and its composites containing 15, 25 and 50 wt% TiC (corresponding to 19.3, 31.2 and 57.6 vol%), produced by hot-pressing process, was investigated under liquid paraffine lubrication against an AISI 52100 steel ball in ambient environment at varied applied loads and sliding speeds. It was found that the wear resistance increased and friction coefficient decreased with increasing of TiC content. The coefficients of friction are in the range of 0.09–0.14 at the given testing conditions. The wear rates of all the materials except the 50% composite are on the order of 10⁻⁶–10⁻⁵ mm³ m⁻¹, the wear rate for the 50% composite is too low to quantify under the two sliding conditions, (50 N, 0.04 m/s) and (100 N, 0.02 m/s). The wear rates of all the materials increase as applied load increases and the increasing extent diminishes with the increase of TiC content, but first increase slightly and then nearly remains steadiness with increasing sliding speed. The 50 wt% composite has wear resistance about 7–20 times better than pure Fe–28Al–5Cr at different sliding parameters. The enhanced wear resistance by TiC addition is attributed to the high hardness of the composites, as well as support of the oil lubrication film/layer by the hard TiC phase. The worn surfaces of all the materials are analyzed by a scanning electron microscope. The dominant wear mechanism of the Fe–28Al–5Cr and 15% composite is grooving and flaking-off, but those of the 25 and 50% composites are mainly shallow grooving.     

Analysis of Lapping and Polishing of a Gauge Block

A lapping experiment and performance analysis for the gauge block is given first. Then, the experimental design using the Taguchi method was employed to optimise the polishing parameters. Results showed that the carrier with circular holes produced better surface roughness in the lapping experiment. The analysis of variance (ANOVA) of the polishing experiment found that the removal rate was a function of pressure and speed. This finding agrees with Preston’s equation. The optimum conditions for high removal rate in the polishing experiment are: pressure, 56.27 kPa; concentration, 15%; speed, 200 r.p.m. The optimum conditions for good surface roughness in the polishing experiment are: pressure, 18.75 kPa; concentration, 10%; speed, 150 r.p.m.     

多孔射流钻头破岩钻孔规律试验研究

利用自行研制的射流破岩系统,对淹没和围压条件下多孔射流钻头的破岩钻孔规律进行了试验研究,重点考虑了水力参数(冲蚀时间、射流压力、围压、喷距)和结构参数(孔眼数量和侧向孔眼扩散角)对破岩效果的影响,结果表明:随着冲蚀时间的增加,破岩效果先增加,后趋于平缓;随着射流压力的增大破岩效果随之增大;随着围压的增加破岩效果随之减小;随着喷距的增加破岩效果呈先增大后减小的趋势,存在最优喷距范围;随着孔眼数量的增多,破岩成孔形状越来越圆整;随着侧向孔眼扩散角的增大,破岩效果呈先增大后减小趋势,存在最优扩散角范围。试验结果可为多孔射流钻头水力参数选择和结构参数设计提供依据。     

Vane tip detachment in a positive displacement vane pump

This paper reports on the theoretical study of the transient chamber, pressure and vane motion in a positive displacement vane pump which widely used in the automotive power steering systems. For analyzing the vane detachment, dynamic equation of vane motion and flow continuity equations are derived and then solved simultaneously using the numerical integration. Vane detachment is shown to be a function of the chamber pressure, rotational speed, and the design geometry of pump. Vane detachment occurs due to excess compression of chamber volume, and it can be reduced by adjustment of design parameters. Specially, silencing V-groove in side plate and radius reduction ratio of compression zone in the cam ring are important design factors for reducing the vane detachment.     

考虑叶片-定子副动压效应的高压叶片泵叶片优化研究

考虑叶片-定子副之间的动压效应,研究了叶片结构参数对叶片泵工作性能的影响,针对不同参数的叶片,采用ADAMS和Fluent软件对高压叶片泵叶片-定子副进行了动力学、流体动压仿真分析和模态分析。以S25VQH子母叶片泵为研究对象,详细分析了叶片结构参数对叶片-定子副之间相互作用力、叶片-定子副之间动压和振动噪声的影响规律。结果表明,优化后的叶片结构使得叶片-定子副之间相互作用力减小,叶片-定子副之间动压和固有频率显著增加;减小了叶片-定子副之间的摩擦磨损和振动噪声,一定程度上延长叶片泵使用寿命。最后,进行了综合台架实验,实验结果与仿真分析结果具有较好的一致性,验证了仿真结果的正确性。     

Forced convection heat transfer of steam in a square ribbed channel

An experimental study of heat transfer characteristics of steam in a square channel (simulating a gas turbine blade cooling passage) with two opposite surfaces roughened by 60 deg parallel ribs was performed. The ranges of key governing parameters were: Reynolds numbers (Re) based on the channel hydraulic diameter (30000–140000), entry gauge pressure (0.2Mpa–0.5Mpa), heat flux of heat transfer surface area (5kWm⁻²–20kWm⁻²), and steam superheat (13°C–51°C). The test channel length was 1000mm, while the rib spacing (p/e) was 10, and the ratio of rib height (e) to hydraulic diameter (D) was 0.048. The test channel was heated by passing current through stainless steel walls instrumented with thermocouples. The local heat transfer coefficients on the ribbed wall from the channel entrance to the fully developed regions were measured. The semi-empirical correlation was fitted out by using the average Nusselt numbers in the fully developed region to cover the range of Reynolds number. The correlation can be used in the design of new generation of gas turbine blade cooled by steam.     

轮缘密封气流影响下的涡轮静叶通道流动特性研究

为探讨轮缘密封气流对高压涡轮静叶通道内流动特性的影响,采用SST湍流模型求解三维非定常雷诺方程,分析无封严腔、无封严气流以及4种封严流量下涡轮静叶通道内压力波动和气流变化。研究结果表明：封严腔出口受上游静叶压力场影响较大,燃气入侵发生在静叶尾缘附近压力面和吸力面两侧气流交汇形成的高压区;封严出流发生在静叶通道中间位置受吸力面侧扩压区影响的低压区;封严出流与主流掺混形成的新涡量结构卷吸了部分附面层流体,削弱了二次流结构的强度,同时对主流通道形成堵塞效应,推动了轮毂二次流向吸力面靠近同时径向位置的抬升;盘泵效应导致的封严出流与主流的掺混增强了非定常效应,封严流量的增大能够抑制通道内非定常效应。     

植物样品中稳定碳同位素的EA-IRMS系统分析方法

通过多组实验对比,分析并讨论了利用元素分析仪-稳定同位素比率质谱仪（EA-IRMS）联用技术测定植物样品中碳同位素比值的实验条件。初步建立了植物样品中稳定碳同位素组成的分析方法,同时对系统分析的稳定性和精密度等进行了检验分析。结果表明：当IRMS真空度为7×10^-8kPa,高压3.0 kV,EA系统Carrier-He载气流量在90～100 mL•min-1,Conflo-He载气压力为80 kPa,氧喷条件为110 mL•min^-1时,使用Cr₂O₃/Co₃O₄作为EA氧化柱氧化剂填料,在严格控制样品残余和本底空白的条件下,植物样品的测定精密度为±0.20‰,测定值与给定值值偏离0.01‰。     

An experimental investigation of tool wear in electric discharge machining

In this study, the variations of geometrical tool wear characteristics – namely, edge and front wear – and machining performance outputs – namely, workpiece removal rate, tool wear rate, relative wear and workpiece surface roughness – were investigated with varying machining parameters. Experiments were conducted using steel workpieces and round copper tools with a kerosene dielectric under different dielectric flushing conditions (injection, suction and static), discharge currents and pulse durations. The experiments have shown that machining parameters and dielectric flushing conditions had a large effect on geometric tool wear characteristics and machining performance outputs. Additionally, published research on tool wear is presented in detail in this study.     

离心式压气机椭圆叶型成型方法

随着高性能、高压比离心式压气机的发展、文献[1]指出：椭圆成型是一种最佳叶型。本文提出了一种椭圆叶型成型方法,该法采用极坐标系代替笛卡儿坐标系,建立了以椭圆中心为极点的简单极坐标方程。直接推导了叶片翘曲角β s,β h[2][3]与极角ψ之间关系式,并给出了β s,β h沿轮盖、轮毂回转面的分布规律。通过95mm轮径压气机示例计算,证实了本文所提出方法是简单而可行的。     

基于灭菌效果监测的真空压力蒸汽灭菌器最优参数选取方法

为提升真空压力蒸汽灭菌器灭菌效果,提出基于灭菌效果监测的真空压力蒸汽灭菌器最优参数选取方法。该方法使用温度压力测定仪、敷料型PCD灭菌包、恒温培养箱等设备,利用不同循环方式通过调整压力变化速率在合格条件与不合格条件下,从不同脉动深度、真空速率、密封时间、脉动正压值和脉动真空值等方面检测空压力蒸汽灭菌器灭菌效果,从检测结果中选取真空压力蒸汽灭菌器最优参数。实验结果表明:真空压力蒸汽灭菌器温度、时间参数分别为130℃、2.8min条件下,抽空深度分别为5kpa、20kpa时,最优脉冲次数分别为5次、10次;密封时间为400min时,脉动正压值和脉动真空值最优参数为-0.095mpa和0.09mpa,此时灭菌合格率达到100%;循环方式分别为低大气压、高大气压时,空气注入量最优参数分别为300 mL和400 mL。