共查询到19条相似文献,搜索用时 62 毫秒
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《工程热物理学报》2016,(1)
通过应用商用软件ANSYS-CFX数值求解Reynolds-Averaged Navier-Stokes(RANS)方程和k-ε两方程湍流模型的方法对不同流量下的汽轮机末级流场进行了详细的非定常研究分析。本次数值计算的计算域包括末级静叶域、动叶域和弧形扩压段,同时采用叶片约化法减少了计算成本。动叶的围带和拉金(PSC)均考虑在计算域之内以获得更为真实的流场结果。结果表明:末级总总等熵效率和长叶片表面静压呈现明显的周期性波动;随着流量的减小,总总等熵效率和叶片载荷均明显降低,扩压段中出现分离涡,并逐渐扩展到动叶栅通道中;分离涡的频率较低,并对长叶片所受到的气流激振产生影响。 相似文献
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《工程热物理学报》2016,(12)
以高负荷局部进气涡轮为研究对象,对其进行了数值研究,并着重对该局部进气涡轮内部流场不均匀性进行了分析。结果表明:局部进气涡轮内部流场的流动情况十分复杂,局部进气堵塞段的存在,使其后面对应的动叶栅进出口速度矢量偏向周向,导致该区域叶片流道内形成了大尺度的旋涡结构,降低了流道的通流能力,增大了该区域的损失水平;各级动叶进出口静压沿周向分布极不均匀,从第一级动叶入口至第二级动叶出口,静压周向不均匀性参数分别为:1.5593、1.0179、0.9163和0.1551,不均匀性沿轴向逐渐衰减;处于不同周向位置的叶片表面压力分布差异明显,直接影响了动叶的做功能力。 相似文献
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背压对缩放型流道涡轮动叶激波结构的影响 总被引:1,自引:0,他引:1
本文采用数值模拟的方法对具有缩放型流道动叶的涡轮级中的激波结构进行了数值研究.在近设计工况下,随叶高的不同,缩放型流道动叶尾缘的相对马赫数分布不同,尾缘燕尾型激波的强弱及其在相邻叶片吸力面的反射波也不同.由于叶片吸力面60%轴向弦长处为一内凹壁面,在该处将会产生一束较强的微弱压缩波,在叶片顶部,该微弱压缩波在通过燕尾波后不远处即发展为一较强的斜激波.随背压增加,动叶尾缘燕尾形激波及其在相邻叶片吸力面上反射波的强度会发生变化,一般来说会减弱,但叶顶由于微弱压缩波所形成的激波会得到强化. 相似文献
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汽轮机调节级静叶栅中采用多分流叶栅的研究 总被引:1,自引:0,他引:1
l引言调节级效率的高低,对整个汽轮机的效率有很大的影响,调节组的效率比中间级的效率低得多。所以,许多汽轮机厂和研究所一直把改善和提高调节级效率作为研究的课题之一。由于相对叶高对叶栅的端部损失影响很大,因而调节级叶片不能太短,只能采用部分进汽度结构,造成了部分进汽损失,这一损失占据调节级的比重很大。例如上海汽轮机厂的125MW机组的调节级叶栅中,叶型损失为6%其中型面损失为1%,端部损失为5凡而部分进汽损失,按照上海汽轮机厂应用的公式计算,部分进汽损失在设计工况时达到8.49%。因此决定调节级效率高低的主要… 相似文献
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叶片安装角偏差对涡轮通道内热斑迁移的影响 总被引:9,自引:0,他引:9
叶片的加工和安装偏差不仅直接影响到涡轮的性能,而且可能对叶片通道内热斑的迁移产生影响.为了研究这种偏差对热斑在涡轮中迁移及叶片热负荷等的影响,本文以某高压涡轮级为例,利用三维非定常数值模拟手段进行了研究.结果表明:动叶安装角的偏差对动叶中热斑的迁移如周向迁移有较明显的影响;而热斑迁移的变化将直接影响涡轮动叶压力面和吸力面的热负荷分布,最终影响涡轮叶片的寿命;并且热斑迁移的变化还导致下游支板通道内温度分布产生较为明显的变化,这有可能给发动机排气温度的测量带来偏差.热斑迁移的变化在涡轮的设计和故障分析中应予重视. 相似文献
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The bunching system of the ATLAS positive ion injector (PII) has been improved by relocating the harmonic buncher to a point
significantly closer to the second stage sine-wave buncher and the injector LINAC. The longitudinal optics design has also
been modified and now employs a virtual waist from the harmonic buncher feeding the second stage sine-wave buncher. This geometry
improves the handling of space charge for high-current beams, significantly increases the capture fraction into the primary
rf bucket and reduces the capture fraction of the unwanted parasitic rf bucket. Total capture and transport through the PII
has been demonstrated as high as 80% of the injected dc beam while the population of the parasitic, unwanted rf bucket is
typically less than 3% of the total transported beam. To remove this small residual parasitic component a new traveling-wave
transmission-line chopper has been developed reducing both transverse and longitudinal emittance growth from the chopping
process. This work was supported by the U.S. Department of Energy under contract W-31-109-ENG-38. 相似文献
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The surface shape of a bucket of sand rotating about its cylindrical axis is studied experimentally and theoretically. Focusing on fast time scales on which surface shape is determined by avalanches, we identify three regimes of behavior. At intermediate and high frequencies, the surface shape is always at its critical shape determined by the Coulomb yield condition. The low frequency behavior displays an unexpected subcritical region at the center of the bucket. To understand this central region, we adapt a continuum model of surface flow developed by Bouchaud et al. and Mehta et al. The model indicates that the subcritical region is due to a nonlinear instability mechanism. (c) 1999 American Institute of Physics. 相似文献
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BEPC Ⅱ is an electron-positron collider designed to run under multi-bunches and high beam current condition. The accelerator consists of an electron ring, a positron ring and a linear injector. In order to achieve the target luminosity and implement the equal bunch charge injection, the Bunch Current Monitor (BCM)system is built on BEPC Ⅱ. The BCM system consists of three parts: the front-end circuit, the bunch current acquisition system and the bucket selection system. The control software of BCM is based on VxWorks and EPICS. With the help of BCM system, the bunch current in each bucket can be monitored in the Central Control Room. The BEPC Ⅱ timing system can also use the bunch current database to decide which bucket needs to refill to implement "top-off" injection. 相似文献
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《中国物理 B》2020,(2)
We propose a compressed ghost imaging scheme based on differential speckle patterns,named CGI-DSP.In the scheme,a series of bucket detector signals are acquired when a series of random speckle patterns are employed to illuminate an unknown object.Then the differential speckle patterns(differential bucket detector signals) are obtained by taking the difference between present random speckle patterns(present bucket detector signals) and previous random speckle patterns(previous bucket detector signals).Finally,the image of object can be obtained directly by performing the compressed sensing algorithm on the differential speckle patterns and differential bucket detector signals.The experimental and simulated results reveal that CGI-DSP can improve the imaging quality and reduce the number of measurements comparing with the traditional compressed ghost imaging schemes because our scheme can remove the environmental illuminations efficiently. 相似文献
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针对北京正负电子对撞机二期工程(BEPCⅡ)原束团流强测量系统(BCM)不能稳定运行的问题,对系统进行了升级。利用高速ADC对束流位置探头(BPM)信号直接采样,在现场可编程门阵列(FPGA)内进行实时数字信号处理,进而得到加速器储存环内的束团流强值。基于反射内存网络,系统可以实现测量结果高速共享、实时显示。升级后系统实现了更高精度的测量,实时显示精度到0.1mA,最佳测量精度达到10μA。通过对系统的触发时钟和算法结构调整,系统实现了长时间的稳定工作,正负电子储存环均实现了对束团流强的均匀性控制,提高了加速器的对撞亮度。 相似文献
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《中国物理 B》2018,(12)
We present the joint probability density function(PDF) between the bucket signals and reference signals in thermal light ghost imaging, by regarding these signals as stochastic variables. The joint PDF allows us to examine the fractional-order moments of the bucket and the reference signals, in which the correlation orders are fractional numbers,other than positive integers in previous studies. The experimental results show that various images can be reconstructed from fractional-order moments. Negative(positive) ghost images are obtained with negative(positive) orders of the bucket signals. The visibility and peak signal-to-noise ratios of the diverse ghost images depend greatly on the fractional orders. 相似文献