CAES离心压缩机可调扩压器调节规律研究

离心压缩机是压缩空气储能系统中关键设备之一,需具备在较宽流量、压力范围内高负荷高效率运行的能力。作为一种变工况调节技术,可调扩压器可以扩大压缩机工作流量范围,改善气动性能。因此,本文以某压缩空气储能系统用离心压缩机为研究对象,通过数值计算方法研究了可调扩压器调节时压缩机性能变化规律。结果表明采用可调扩压器可以有效拓宽压缩机运行特性,工作流量范围扩大44%,压比范围扩大25%.此后,本文采用Kriging模型获得了压缩机综合性能曲线图和不同储能工况需求下扩压器的调节方案及规律,为压缩空气储能系统离心压缩机变工况主动控制提供了依据。     

Measurements in the vaneless diffuser of a radial flow compressor

Results from an experimental study of flow behaviour at the inlet of a vaneless diffuser of a centrifugal compressor are presented. Measurements from a crossed hot-wire probe are given for operating points having inlet flow coefficients ranging from 0.006 to 0.019 at different Reynolds numbers. Instantaneous, time-averaged, and phase-averaged absolute velocity and flow angle at the diffuser inlet are deduced from the hot-wire signals after correction for mean density variations. These results show how flow behaviour varies in stable, rotating stall and surge regimes of compressor operation     

Performance of T-shape barriers with top surface covered with absorptive quadratic residue diffusers

A previous paper [Applied Acoustics 66 (2005) 709-730] has shown that adding a quadratic residue diffuser (QRD) to the top of a T-shape barrier can provide better barrier performance than an equivalent purely absorptive barrier. In here, we extend the study to look at the performance when a QRD is made absorptive. This paper presents an investigation on the acoustic performance of a few welled-diffusers with different absorption ability on top of a T-shape noise barrier. The absorption properties of the diffusers are modified with different sequences, by filling the wells with fiberglass, by covering the well entrance with wire meshes, and by putting perforated sheet either on the top surface or inside the wells. A 2D Boundary Element Method (BEM) is used to calculate the barrier insertion loss. The numerical and experimental results on diffuser barriers with rigid and absorptive covers are compared. Among the tested models the best method of treating diffuser barriers with absorbent agents in the QRD is found to be a perorated sheet on top or inside the diffuser wells. It is found that increasing the absorption ability of QRD by fiberglass or high resistance wire meshes has negative effect on the efficiency of a QRD barrier. It is shown that, if the increase in absorption destroys the effect of resonance in wells, it will also have negative effect on the insertion loss performance of the QRD edge barrier.     

Optical diffusers based on uniform nano-sized polymer balls/nematic liquid crystals composite films

ABSTRACT

Optical diffusers are promising diffusing materials in the optical devices such as monitors, projectors, fibre optics, light-emitting diode (LED) systems and liquid crystal displays (LCDs). We report optical diffusers comprising uniformly distributed nano-sized polymer balls/nematic liquid crystals (LCs) by ultraviolet (UV) click reaction of ene monomer and thiol monomer. By optimising the mass ratio 1:1 of ene and thiol, of which the average diameter of the corresponding nano-sized polymer balls is about 900 nm, relatively high optical transmission and haze with 88.99% and 94.49% are yielded, respectively. Furthermore, by controlling the curing time, the average diameter of nano-sized polymer balls can be reduced to 810 nm, and the developed film exhibits high transmission (98.49%) without sacrificing the high haze (91.77%). This paper demonstrates that UV click reaction is an economical approach to fabricate optical diffusers in a controllable manner.     

A switchable optical diffuser based on a polymer/nematic liquid crystal composite film with transient polymer balls-networks microstructure

ABSTRACT

With the increasing development of multifunction liquid crystal displays (LCDs), multifunction optical diffusers have attracted more attention. In this work, switchable optical diffusers based on the transient polymer balls-networks in polymer/nematic liquid crystal composite films have been prepared and investigated, and the effects of thiol content, curing time, LC content and photo-initiator content on the polymer microstructures and optical properties of optical diffusers are systematically studied. An optical diffuser with the transient polymer balls-networks microstructure has achieved the high transmission (96.42%), high haze (90.49%), excellent optical diffusing ability and wide viewing angle of 150° (from ?75° to 75°) on its off state. By the application of electric field of 40.0 voltage, the viewing angle of the optical diffuser turns to be narrower (from ?60° to 60°), which gives great applications in tunable viewing angle devices and other electric optical devices.     

Erosion in conical diffusers in particulate-laden cavitating flow

This paper highlights the serious damage that can occur in diffusing sections of pipework in which a cavitating particulate-laden fluid is flowing. The combined effects of particle erosion and cavitation are shown to remove considerably more material than would be expected from summing the effects of the individual mechanisms. It is demonstrated that, to be sure of avoiding this accelerated surface erosion, the transition from a smaller flow section to a larger one needs to be an abrupt expansion. If pressure recovery is important, a possible design solution is proposed. In the case of swirling flow, the expansion again needs to be abrupt. Evidence was also obtained which showed that, by allowing air to be entrained into the low pressure region in the flow, the cavitation and the erosion can be substantially reduced.     

Rapid fabrication of surface-relief plastic diffusers by ultrasonic embossing

This paper discusses an innovative and effective ultrasonic embossing process, which enables the rapid fabrication of surface-relief plastic diffusers. The metallic mold bearing the microstructures is fabricated using a tungsten carbide turning machine. A 1500-W ultrasonic vibrator with an output frequency of 20 kHz was used to replicate the microstructure onto 1-mm-thick PMMA plates in the experiments. During ultrasonic embossing, the ultrasonic energy is converted into heat through intermolecular friction at the master mold/plastic plate interface due to asperities to melt the thermoplastic at the interface and thereby to replicate the microstructure. Under the proper processing conditions, high-performance plastic diffusers have been successfully fabricated. The cycle time required to successfully fabricate a diffuser is less than 2 s. The experimental results suggest that ultrasonic embossing could provide an effective way of fabricating high-performance plastic diffusers with a high throughput.     

Computational fluid dynamics analysis of diffuser performance in gas-powered jet pumps

Jet pump diffuser performance is analyzed, both in terms of past experimental work dealing with the high inlet flow distortions involved and in the sense that this problem is amenable to predictive investigation by computational fluid dynamics techniques. In these highly nonuniform flow conditions, diffusers are seen to justify their inclusion in a jet pump design, for regaining static pressure downstream of the vacuum chamber, even though their performance in effectiveness terms is lowered by about two thirds at high inlet glow distortion levels. A satisfactory correlation has been found between outlet and inlet conditions and diffuser area ratio, extending well beyond past experimental published results for diffuser geometry and distorted inlet flows.     

大面积多周期伪随机序列扩散体群的一种优化布置方案

伪随机序列扩散体具有良好的扩散效果，但是大面积周期布置时会在扩散方向产生大量旁瓣。为了消除这些旁瓣，并得到符合使用者要求的扩散声压响应曲线，本文提出一种实现伪随机序列扩散体群大面积最佳布置方案的布置方法。