Self-Mixing Interference Effects in LD Pumped Multi-Mode Solid-State Laser

Based on the effective structure of the self-mixing interference effects,a general model for the self-mixing interference effects in the LD pumped solid-state laser has been established for the first time.The numerical simulation of the self-mixing interference signal has been done,the results show that when the external cavity length is integral times of 1/2,1/3,2/3,1/4,3/4 of the effective cavity length,the intensity of the self-mixing interference signals reach maximum in value.While that of single mode laser is integral times of half of the effective cavity length,the measuring precision of displacement of single mode laser is λ/2.A conclusion can be drawn from the above results that the measuring precision of displacement of multi-mode laser is higher than that of single mode laser.

Application of the Modified nverse Design Method in the Optimization of the Runner Blade of a Mixed-Flow Pump

To improve the design speed and reduce the design cost for the previous blade design method, a modified inverse design method is presented. In the new method, after a series of physical and mathematical simplifications, a sail?like constrained area is proposed, which can be used to configure di erent runner blade shapes. Then, the new method is applied to redesign and optimize the runner blade of the scale core component of the 1400?MW canned nuclear coolant pump in an established multi?optimization system compromising the Computational Fluid Dynamics(CFD) analysis, the Response Surface Methodology(RSM) and the Non?dominated Sorting Genetic Algorithm?II(NSGA?II). After the execution of the optimization procedure, three optimal samples were ultimately obtained. Then, through comparative analysis using the target runner blade, it was found that the maximum e ciency improvement reached 1.6%, while the head improvement was about 10%. Overall, a promising runner blade inverse design method which will benefit the hydraulic design of the mixed?flow pump has been proposed.

Effects of Meridional Flow Passage Shape on Hydraulic Performance of Mixed-flow Pump Impellers

During the process of designing the mixed-flow pump impeller, the meridional flow passage shape directly affects the obtained meridional flow field, which then has an influence on the three-dimensional impeller shape. However, the meridional flow passage shape is too complicated to be described by a simple formula for now. Therefore, reasonable parameter selection for the meridional flow passage is essential to the investigation. In order to explore the effects of the meridional flow passage shape on the impeller design and the hydraulic performance of the mixed-flow pump, the hub and shroud radius ratio (HSRR) of impeller and the outlet diffusion angle (ODA) of outlet zone are selected as the meridional flow passage parameters. 25 mixed-flow pump impellers, with specific speed of 496 under the design condition, are designed with various parameter combinations. Among these impellers, one with HSRR of 1.94 and ODA of 90° is selected to carry out the model test and the obtained experimental results are used to verify accuracies of the head and the hydraulic efficiency predicted by numerical simulation. Based on SIMPLE algorithm and standard k-ε two-equation turbulence model, the three-dimensional steady incompressible Reynolds averaged Navier-Stokes equations are solved and the effects of different parameters on hydraulic performance of mixed-flow pump impellers are analyzed. The analysis results demonstrate that there are optimal values of HSRR and ODA available, so the hydraulic performance and the internal flow of mixed-flow pumps can be improved by selecting appropriate values for the meridional flow passage parameters. The research on these two parameters, HSRR and ODA, has further illustrated influences of the meridional flow passage shape on the hydraulic performance of the mixed-flow pump, and is beneficial to improving the design of the mixed-flow pump impeller.

Experimental Study of the Influence of Flow Passage Subtle Variation on Mixed-flow Pump Performance

In the mixed-flow pump design, the shape of the flow passage can directly affect the flow capacity and the internal flow, thus influencing hydraulic performance, cavitation performance and operation stability of the mixed-flow pump. However, there is currently a lack of experimental research on the influence mechanism. Therefore, in order to analyze the effects of subtle variations of the flow passage on the mixed-flow pump performance, the frustum cone surface of the end part of inlet contraction flow passage of the mixed-flow pump is processed into a cylindrical surface and a test rig is built to carry out the hydraulic performance experiment. In this experiment, parameters, such as the head, the efficiency, and the shaft power, are measured, and the pressure fluctuation and the noise signal are also collected. The research results suggest that after processing the inlet flow passage, the head of the mixed-flow pump significantly goes down; the best efficiency of the mixed-flow pump drops by approximately 1.5%, the efficiency decreases more significantly under the large flow rate; the shaft power slightly increases under the large flow rate, slightly decreases under the small flow rate. In addition, the pressure fluctuation amplitudes on both the impeller inlet and the diffuser outlet increase significantly with more drastic pressure fluctuations and significantly lower stability of the internal flow of the mixed-flow pump. At the same time, the noise dramatically increases. Overall speaking, the subtle variation of the inlet flow passage leads to a significant change of the mixed-flow pump performance, thus suggesting a special attention to the optimization of flow passage. This paper investigates the influence of the flow passage variation on the mixed-flow pump performance by experiment, which will benefit the optimal design of the flow passage of the mixed-flow pump.

Enhancement of Anti-Stokes Line of Stimulated Four-Photon Mixing in an Er^(3+ ) Doped Silica Fiber

By using a pidsed dye Laser of nanosecond level as a pump source,we have investi-ga-ted stiinulated Ranmn sca.ttcring and stiiuulatcd four-photon mixing in Er^(3+) doped silicu fibers.The experimental results show that all lines,incJuding the pump radia-tion line,are obviously broadened and the anti-Stokes lines of stimulated four-photon mixing are greatly enhanced,and that the enhancement effect is independent of the wavelength.

Broadband and continuous wave pumped second-harmonic generation from microfiber coated with layered GaSe crystal

The conversion-efficiency for second-harmonic(SH)in optical fibers is significantly limited by extremely weak second-order nonlinearity of fused silica,and pulse pump lasers with high peak power are widely employed.Here,we propose a simple strategy to efficiently realize the broadband and continuous wave(CW)pumped SH,by transferring a crystalline GaSe coating onto a microfiber with phase-matching diameter.In the experiment,high efficiency up to 0.08%W-1mm-1 is reached for a C-band pump laser.The high enough efficiency not only guarantees SH at a single frequency pumped by a CW laser,but also multi-frequencies mixing supported by three CW light sources.Moreover,broadband SH spectrum is also achieved under the pump of a superluminescent light-emitting diode source with a 79.3 nm bandwidth.The proposed scheme provides a beneficial method to the enhancement of various nonlinear parameter processes,development of quasi-monochromatic or broadband CW light sources at new wavelength regions.

Correlation of Blood Lactate and Mixed Venous Oxygen Saturation in Off-Pump CABG

Aim: To evaluate the correlation of blood lactate and mixed venous oxygen saturation to predict outcome in off-pump coronary artery bypass grafting. Method: This is a randomized study including 30 patients. Blood lactate and mixed venous oxygen saturation were measured in 4 groups of patients—number of grafts, presence or absence of left main coronary artery disease, ejection fraction and serum creatinine. Blood samples were taken before induction, after grafting, on intensive care unit admission, 24 hours and 48 hours after surgery. The measured blood lactate and mixed venous oxygen saturation are compared to assess the outcomes in terms of duration of ventilation and intensive care unit stay. Results: The blood lactate and mixed venous oxygen saturation values increased post operatively but no statistically significant difference in three groups— number of grafts, left main coronary artery disease and ejection fraction. In serum creatinine group, the blood lactate value was found to be statistically significant after grafting in patients with creatinine <1.5 mg/dl, however, there was a significant disparity in numbers. Conclusion: Mixed venous oxygen saturation is a better predictor of morbidity than blood lactate in terms of intensive care unit stay in patients undergoing off pump coronary artery bypass grafting.

降速方式对混流泵压力脉动特性的影响

混流泵在降速过程中的内部流动特性变化对其性能和稳定性有重要影响。针对这一问题,该研究探究了混流泵在降速过程中内部流动的复杂性,尤其关注不同降速方式对泵内压力脉动特性的影响。通过构建多通道测试系统,收集了混流泵在不同降速方式下的外特性参数信号和泵内压力脉动信号。并采用非稳态信号处理技术,从时域、频域和时频三方面探究不同降速方式对叶轮出口和导叶内部的压力脉动特性的影响以及二者之间的相关性。结果表明,泵内压力脉动的峰值和样本熵的变化趋势与不同降速方式的幂指数呈正相关关系;在整个降速过程中叶轮出口压力脉动对导叶内压力脉动起主导作用;叶轮出口和导叶内部压力脉动之间的相干频率主要集中于80~120 Hz之间;在不同降速过程中叶轮出口和导叶内部的压力脉动之间强相关区域的频带范围保持不变,但是强相关区域在整个降速过程频带范围中的占比有所变化;对于具有固定初始转速和目标转速的降速过程,降速方式的改变不会影响叶轮出口和导叶内压力脉动的相干频率。研究结论可为揭示混流泵瞬态运行特性及提高混流泵降速运行中的稳定性提供参考。

考虑表面粗糙度与空化效应的组合密封润滑分析

为了研究表面粗糙度及空化效应对压裂泵柱塞密封副密封性能的影响,基于稳态Reynolds方程,建立了粗糙峰和空化效应影响下组合密封的弹流润滑数值模型.在数值模拟基础上,采用有限体积法求解稳态Reynolds方程,研究了密封副在表面粗糙度影响下的油膜厚度、油膜压力、油膜流速分布规律,以及不同的往复速度和滑环表面粗糙度对密封性能的影响.结果表明,外行程流体动压效应微弱,油膜在空气侧附近会出现空化现象;较高的往复速度有利于减小泄漏量及摩擦阻力;滑环表面粗糙度从0.8μm增加到1.8μm时,净泄漏量与外行程摩擦力分别升高了180.4%和11.17%.因此,在工作过程中应设置较高的往复速度和使用较低粗糙度的滑环以提高密封性能.

基于二重威布尔混合分布的某型燃机燃油泵组件可靠性分析

燃油泵组件是机电一体化的产品,其在使用中获得的故障数据存在不同失效机理的情况,因此一重威布尔分布无法准确描述产品失效机理,而混合分布通过将多种失效分布进行耦合,能够充分描述产品失效机理。本文将二重三参数威布尔混合分布模型应用在舰船发动机附件故障分析中,基于某型燃机燃油泵组件的故障数据,通过数据分析直方图确定故障模型与模型初始化参数,通过Matlab非线性曲线拟合方法来估计二重三参数威布尔混合分布的参数。研究方法及成果能够为燃油泵组件可靠性分析及优化改进提供一定的借鉴。

抽水蓄能电站单机容量与机组转速选择

通过分析国内外已建抽水蓄能电站机组主要技术参数,研究抽蓄电站定转速混流式水泵水轮机水头与单机容量、参数水平的关系,提出了不同水头段抽水蓄能电站单机容量和比速系数选择原则,推荐了合适的机组额定转速范围,可提高抽水蓄能电站水泵水轮机选型设计的工作效率和成果质量。

叶顶间隙对螺旋混流式喷水推进泵内流及推进特性的影响

喷水推进泵是舰船泵喷推进系统的核心部件,喷水推进泵在工作过程中,叶顶间隙处所产生的泄漏流会严重影响混流泵的工作性能。为了探讨叶轮叶顶间隙对喷水推进泵推进特性的影响,本文定义了叶顶间隙系数τ,设计了六种不同叶顶间隙系数模型并使用Ansys进行仿真分析,最终得到叶顶间隙对于喷水推进泵内流以及推进特性的影响规律。结果表明:随着叶顶间隙系数的增大,叶顶间隙处泄漏流逐渐增加,泄漏涡影响范围变大,轴向推力随着叶顶间隙系数的增大呈负指数下降,叶顶间隙处泄漏量随指数上升,喷水推进泵内流损失增加,推进效率持续减小,并且在大流量工况下叶顶间隙对喷水推进泵推进特性影响最大,在设计的六套模型中,叶顶间隙系数为0.08,叶顶间隙为0.16mm时效率最高。通过本文的研究可以发现,叶顶间隙对于喷水推进泵内流以及推进特性影响较大,在设计时应尽量减小叶顶间隙。

沙集泵站改造叶轮选型及流道改形研究

针对沙集泵站空化汽蚀较为严重,在工程加固改造时主体结构不变,无法通过降低站房底板增加叶轮淹没深度,从而提高空化性能的实际问题,采用计算流体动力学CFD方法,考虑泵站进口不同水位,对水泵装置全流道内部流动进行数值分析,研究水泵空化和能量特性。小幅降低叶轮中心高程,不仅未能减小空化范围,反而降低了泵装置效率,不宜采用。通过优选水泵水力模型、降速、增径并适当修整流道等方法,在保证泵装置能量性能的前提下,提高水泵空化性能。结果表明,采用方案一:叶轮直径增至1.68 m,转速降至250 r/min,基本消除了叶片进水边附近的附着空化,同时能够满足泵站特征水位组合下的流量和效率。成果也可用于类似泵站的设计和机组的选型。

一种核电厂重要厂用水泵房环境温湿度高处理方法

高温高湿气候时,东南沿海核电厂重要厂用水泵房频发温度高报警或设备凝露问题,影响泵电机运行安全,降低核电厂冷源安全可靠性。因此,在不改变当前通风方式情况下,提出在泵房进风风室增加一种新风混风制冷机组进行空气温湿度处理的方法。机组采用两路新风,将经制冷除湿后的新风与外界新风混合。通过计算确定进风参数。该方法无需冷却所有新风,无需再热段,通过混风升温降低相对湿度,可以彻底解决所有工况下泵房环境温度、湿度超标问题,且兼顾经济性。

CO_(2)/R1233zd(E)混合工质回热热泵系统性能优化分析

空气源热泵作为一种新型的节能环保技术,在多种供暖场景中得到了广泛应用,其在低环境温度下的运行可靠性和效率是重要的关注点。采用二元混合工质CO_(2)/R1233zd(E)构建了兼顾环保性、安全性和高效性的回热热泵系统,并通过优化分析得到该系统的COP、单位容积制热量、吸气压力和排气压力等系统性能在-30~-10℃环境温度下的变化规律。通过与目前常用的传统补气增焓系统和复叠系统进行对比,探明了该混合工质回热系统在低环境温度下可以保持较高效率运行。在-30~-10℃环境温度下,与R134a补气增焓系统相比其COP和单位容积制热量分别减小了9.8%~20.6%和增大了3.5%~56.1%,并且压缩机压比以及压比随环境温度的变化幅度低于其他方案。二元混合工质回热系统结构简单,CO_(2)和R1233zd(E)安全环保,因此提出的混合工质回热系统方案在低环境温度采暖的应用中具有独特优势。

黏度对油气混输泵内气相和泄漏涡分布的影响

为了更准确地探究油气混输泵在高黏度条件下输送介质时,其流道内常常存在的泄漏涡、分离涡等这些涡流的特性,文中选用欧拉-欧拉非均相流模型对油气混输泵内气相分布以及涡分布进行分析,并使用刚性旋转涡量表征涡旋强度.研究表明:在混输泵叶轮流道内,气相的存在较大地影响了叶片表面流线的分布规律.偏设计工况下,当黏度较小时气相主要集中分布在压力面后半段,当黏度较大时气相在压力面后段分布较少.不同工况下泄漏涡的分布规律都与气相分布吻合度较高,在偏设计工况下,其气相在流道尾部的聚集度和黏度成正比,但是在大流量工况下流道内局部的气相聚集得到了改善.此外,由于高黏度条件下流道内湍流黏度较低以及剪切涡较多,所以在考虑刚性旋转时的涡量分布更为准确.研究结果可为油气混输泵的优化设计等提供理论参考.

工况参数对混输转子泵排出性能影响

混输转子泵是气液固三相混输工艺的关键设备,输送介质成分复杂,内部流动机理尚不明确。因此,基于动网格技术和Mixture多相流模型对混输转子泵内部进行数值模拟,分析了混输转子泵在不同工况参数下的性能变化规律。结果表明:气相与固相占比对混输泵性能影响不明显;转速对混输转子泵性能影响明显,转速增加,容积效率显著上升,流量脉动略微降低;随着压差的增加,出口流量降低,容积效率显著下降,流量脉动大幅上升;而在3个工况参数交互作用下,混输转子泵的性能波动明显,混输转子泵在低含气、高含砂、低转速、高压差工况时表现较差。研究结果对混输转子泵的深入研究和广泛应用提供了有价值的参考。

超大扬程变幅大型导叶式混流泵选型研究

浙江省杭州市九溪排涝泵站,装设有6台大型导叶式混流泵,单机流量50 m^(3)/s,单台电动机功率10000 kW,为国内目前在建单机流量最大的导叶式混流泵。水泵受上游来水和下游钱塘江潮位的影响,扬程变化幅度很大,最低扬程1.71 m,设计扬程14.0 m,最高扬程15.4 m。为保证泵组在超大扬程变化范围内保持安全稳定运行,结合九溪泵站建筑物布置和运行情况,充分利用下游挡潮闸提高最低扬程,详细分析比较全调节和变频调节对优化低扬程运行工况的作用,并采取综合措施提高泵组结构设计刚强度,从多角度对泵组运行工况和选型方案进行优化分析,并提出泵组变频调节和运行优化建议,为类似泵站提供参考。

温度对组合型织构油封密封性能的影响

耦合流体力学、变形分析、接触力学、能量守恒方程和黏温黏压方程,建立具有表面组合型织构油封的密封区域混合润滑数值模型,研究温度对表面组合型织构油封密封性能的影响;通过有限差分法对数值方程离散求解,得到不同表面织构油封唇口的温度分布及不同转速下油封唇口的最高温度,对比分析温升对油封泵吸率、油膜厚度、摩擦扭矩等密封性能的影响。结果表明:油封最高温度位于唇尖处,无织构油封最高温度略高于织构油封,随着转速的增加,油封最高温度也都随之增加;织构的存在会引起油封泵吸率的增加和平均油膜厚度变大;随着温度的升高,油封泵吸率、摩擦扭矩、油膜厚度都会逐渐减小,油封密封性能明显下降,温度升高至一定程度,油封泵吸率会变为负值。

多相混输泵用超高压机械密封性能研究

针对超高压混输泵机械密封易磨损失效的问题,介绍了端面槽加工和涂层应用两种策略,用热流固耦合分析方法,分析了浅槽微接触式机械密封在实际应用中的温度分布和端面变形情况,阐述了表面涂层技术的应用,进行了一系列机械密封性能的试验研究。研究结果不仅证实了这些技术在提高机械密封寿命和可靠性方面的有效性,还证实了端面开槽和涂层技术在降低摩擦、改善耐磨性能方面的显著效果。为超高压混输泵机械密封系统的设计和优化提供了重要的理论依据及实践指导。