辅助引射对蒸汽喷射器性能影响的数值研究

首次提出了通过局部低压区辅助引射来改善蒸汽喷射器工作性能的技术途径,并利用FLUENT软件对蒸汽喷射器辅助引射前后内部流场进行了数值模拟计算,重点研究分析了双临界范围内背压波动工况下不同辅助引射方式对工作蒸汽质量流量、引射蒸汽质量流量、辅助引射蒸汽质量流量、内部流场和激波现象的影响及其原因。结果表明:混合室辅助引射不利于改善蒸汽喷射器的引射性能,而喉部辅助引射和扩压室辅助引射能提高蒸汽喷射器的引射效率,且在不同背压下存在一个最佳的辅助引射优化方案。     

喷射器扩压室结构设计优化研究

扩压室对喷射器内混合流体的降速增压有着重要影响.本文基于真实流体物性,采用气体动力学方法建立改进的一维混合模型并提出扩压室结构设计优化方法.将模型计算结果与文献实验值对比验证了模型的准确性.分析了扩压室结构参数与喷射器膨胀比、喷嘴喉部直径和混合室直径之间的关系.结果表明,扩压室半锥角α随膨胀比Pg/Pe、扩压室出口直径...     

多级气-固引射器的研究计算及其在沸腾燃烧锅炉的应用

本文分析了多级气-固引射器的特点,推导了气体引射气-固混合物和气-固混合物引射气体两种引射器的有关计算式,编写了应用于沸腾燃烧锅炉飞灰再燃引射系统的通用计算程序.     

等压混合引射器设计与实验研究

 采用1维处理方法,建立了便于设计人员使用的等压混合引射器性能计算分析与工程设计方法,并详细分析了等压混合引射器各主要参数对性能的影响。该分析方法基于气体焓的变化,因此可应用于各种引射气体与被引射气体。为了控制尺寸,还首次将多喷嘴引射方式与等压混合结合起来。实验结果验证了等压混合引射器性能计算分析与工程设计方法的可靠性以及多喷嘴引射方式应用于等压混合引射器的可行性。     

微小通道内气体突扩阻力特性的实验研究

采用缝隙测压方法,测量了内径从0.245 mm到0.850 mm的三种不同面积比的微通道内氮气和氦气突扩时的局部阻力损失.结果表明,两种气体的局部阻力系数不同.在层流阶段,微通道内的两种气体突扩阻力系数都要高于常规管的值,氦气的突扩阻力系数还高于氮气的阻力系数.而在湍流阶段,由于气体的可压缩性,突扩阻力系数随雷诺数的增大而增大.而且通道面积比越小,突扩阻力系数增加的幅度越大.     

两段式喷嘴对CO_2两相流引射制冷系统性能的影响

文章对采用两段式喷嘴的引射器及其两相流引射制冷系统在不同工况、不同几何尺寸条件下进行了实验研究。实验结果表明,在实验工况固定的条件下,采用两段式喷嘴的CO_2两相流引射制冷系统的COP随引射器第一喉部直径的增大而增大,引射比随第一喉部直径的增大而减小;系统COP和引射比随引射器中间连接直径的增大而减小。对于固定几何尺寸的引射器,系统COP随气冷器出口压力的升高而增大,引射比随气冷器出口压力的升高先减小后增大,在9MPa时引射比最小。与传统的CO_2制冷系统相比,采用两段式喷嘴的CO2两相流引射制冷系统的COP在不同工况的条件下均高于传统系统的COP,最大可提高约15%。     

引射式气动窗口的光束质量研究

 实验研究了引射式气动窗口喷流引射对输出光束质量的影响,给出了不同引射喷管喉道尺寸下,不同引射喷流滞止压力时的气动窗口光学特性参数,其中包括:Strehl强度比,波像差最大值,波阵面形状,均方根值以及调制传递函数。实验表明,除引射喷管喉道尺寸dH=2.5mm,引射喷流滞止压力为0.5MPa工况外,其它工况时喷流引射对输出光束质量影响很小。因此引射式气动窗口可以保证输出高质量的光束。     

喷嘴喉部直径对CO2引射制冷系统性能的影响

为探索两级汽液分离CO2引射制冷系统中喷嘴第一喉部直径对其性能的影响,实验测量了使用不同喷嘴第一喉部直径的两级汽液分离CO2引射制冷系统的性能,并与传统CO2两级节流引射制冷系统进行了比较.实验结果表明,随着第一喉部直径的增大,引射比和系统COP均逐渐增大,引射比在第一喉部当量直径为2.0 mm时达到最大值,而系统CO...     

超音速射流在高温气体环境中引射特性的模拟研究

本文以超音速氧气射流为研究对象,采用温度修正的k-ε湍流模型,对氧气射流在不同环境温度下的引射行为进行数值模拟研究.通过对模拟结果与文献中试验结果的比较发现温度修正的k-ε模型能够准确预测高温环境中射流行为.射流引射行为的模拟结果表明:环境温度对湍流射流的引射行为有很大的影响,在标准大气压下,随着环境温度的升高,射流引射率降低.与此同时,室温下的模拟结果符合经验公式,而在高温气体环境中,温度对湍流混合增长速率的影响不可忽略,随着环境温度的升高,环境气体密度和湍流混合增长速率均减小,从而使射流引射率降低并逐渐偏离室温下得到的经验公式.     

科恩达环形射流元件的数值及试验研究

本文研究了面积比、科恩达面曲率、进口条件和压强系数对科恩达环形射流元件引射系数的影响。研究结果表明:科恩达环形射流元件的引射系数和面积比呈线性关系;对于结构一定的科恩达环形射流元件来说,进口条件对引射系数影响很小;在一定范围内增加科恩达面曲率可增加科恩达环形射流元件的引射系数;揭示了科恩达效应使科恩达环形射流元件引射系数增加的机理;压强系数的提高使科恩达环形射流元件内部形成回流引使系数降低。     

蒸汽喷射制冷系统中喷射器内特殊流动现象的研究

本文通过求解二维N-S方程来模拟蒸汽喷射器内复杂的流动混合过程,模拟时使用了蒸汽的真实物性公式。与理想气体假设不同,真实物性的带入,真实地反映了蒸汽经缩放喷嘴时,温度递减,喷嘴出口后温度场波动变化的特征．模拟时,通过对节点焓值的计算,得出了喷射器内发生相变的蒸汽的百分含量,实现了相变现象的定量分析。在激波捕捉方面,验证了喷射器内喷嘴出口后,膨胀波(压缩波)经混合层反复折射、转化、衰减的过程,以及在扩压室入口会产生斜激波的理论预测。     

变截面超-超引射器启动特性数值研究

为研究不同结构参数与来流参数下变截面超-超引射器的启动特性,用于指导超-超引射器设计与工况调试,采用二维雷诺平均Naiver-Stokes方程,数值研究了引射器混合室不同收缩比、一次流和二次流的不同总压比、总温比下超-超引射器的启动规律,并定义了“启动系数”来判别超-超引射流场是否建立。研究结果表明:随着收缩比（范围0.7～0.9）的增加,超-超引射器启动的临界总压比、总温比均先降低后升高,收缩比0.8时,存在最佳总压比5.88,最佳总温比0.21。结构参数一定,超-超引射器随总温比升高启动难度增加。当超-超引射器处于启动状态下,室压不随总温比、总压比变化而变化,引入的启动系数较引射系数可不依赖具体工况而直接判别超-超引射器是否启动。     

蒸汽喷射器变工况性能的CFD探讨

利用二维轴对称,真实气体模型对喷射式制冷空调系统的喷射器进行CFD计算。真实气体模型占用较多的计算机资源,但它的计算结果更加真实。计算的目的在于得到在变工况条件下喷射器性能的变化和制冷系统性能的变化情况。在计算范围中,存在一最优的发生压力Pg*(3.973568bar),使得此时的喷射系数和系统COP最大。当Pg>Pg*时,喷射系数和COP随着发生压力的增加而减少;当Pg相似文献   

喉部面积比对喷射器性能的影响分析

利用真实气体的二维轴对称,模型对喷射式空调系统的喷射器进行CFD计算,为了研究喷射器的喉部面积比对喷射器性能的影响.在计算工况条件下,存在一最优的喉部面积比AR*(5.76),使得此时的喷射系数和系统COP最大.当AR AR*时,喷射器出现倒流现象,而且随着A...     

Ejectors for pressure recovery systems of supersonic chemical lasers

Results of a numerical study of performance characteristics of supersonic ejectors with nozzles of different types are reported. The work was carried out with the aim of developing a high-performance ejector for pressure recovery systems of supersonic chemical lasers. A specific feature of the operation of ejectors in pressure recovery systems consists in that, in this case, the ejecting and ejected gases, as they undergo mixing, have different thermodynamic properties, and the ejection coefficient depends on the ratio between the temperatures of the gases and on the ratio of their molecular masses. Since the operation of an ejector is based on the mixing process, the task consisted in intensification of this process using nozzles of special geometries. The performance of ejectors was judged considering an integral parameter, the product of induction by compression ratio. The calculations of the 3D viscous gas flow in the ejector channel were performed using ANSYS software. In verifying the numerical model, a comparison with experimental data obtained earlier on a model ejector facility and during tests of real pressure recovery systems in operation with supersonic chemical lasers was performed.     

Performance comparison of supersonic ejectors with different motive gas injection schemes applicable for flowing medium gas laser

A class of flowing medium gas lasers with low generator pressures employ supersonic flows with low cavity pressure and are primarily categorized as high throughput systems capable of being scaled up to MW class. These include; Chemical Oxygen Iodine Laser (COIL) and Hydrogen (Deuterium) Fluoride (HF/DF). The practicability of such laser systems for various applications is enhanced by exhausting the effluents directly to ambient atmosphere. Consequently, ejector based pressure recovery forms a potent configuration for open cycle operation. Conventionally these gas laser systems require at least two ejector stages with low pressure stage being more critical, since it directly entrains the laser media, and the ensuing perturbation of cavity flow, if any, may affect laser operation. Hence, the choice of plausible motive gas injection schemes viz., peripheral or central is a fluid dynamic issue of interest, and a parametric experimental performance comparison would be beneficial. Thus, the focus is to experimentally characterize the effect of variation in motive gas supply pressure, entrainment ratio, back pressure conditions, nozzle injection position operated together with a COIL device and discern the reasons for the behavior.     

Realization of an advanced nozzle concept for compact chemical oxygen iodine laser

Conventional supersonic chemical oxygen–iodine lasers (SCOIL) are not only low-pressure systems, with cavity pressure of 2–3 Torr and Mach number of approximately 1.5, but also are high-throughput systems with a typical laser power per unit evacuation capacity of nearly 1 J/l, thus demanding high capacity vacuum systems which mainly determine the compactness of the system. These conventional nozzle-based systems usually require a minimum of a two-stage ejector system for realization of atmospheric pressure recovery in a SCOIL. Typically for a 500 W class SCOIL, a first stage requires a motive gas flow (air) of 120 gm/s to entrain a laser gas flow of 3 g/s and is capable of achieving the pressure recovery in the range of 60–80 Torr. On the other hand, the second stage ejector requires 4.5 kg/s of motive gas (air) to achieve atmospheric pressure recovery. An advanced nozzle, also known as ejector nozzle, suitable for a 500 W-class SCOIL employing an active medium flow of nearly 12 g/s, has been developed and used instead of a conventional slit nozzle. The nozzle has been tested in both cold as well as hot run conditions of SCOIL, achieving a typical cavity pressure of nearly 10 Torr, stagnation pressure of approximately 85 Torr and a cavity Mach number of 2.5. The present study details the gas dynamic aspects of this ejector nozzle and highlights its potential as a SCOIL pressure recovery device. This nozzle in conjunction with a diffuser is capable of achieving pressure recovery equivalent to a more cumbersome first stage of the pressure recovery system used in the case of a conventional slit nozzle-based system. Thus, use of this nozzle in place of a conventional slit nozzle can achieve atmospheric discharge using a single stage ejector system, thereby making the pressure recovery system quite compact.     

喷嘴直径对喷射器性能的影响分析

利用二维轴对称,真实气体模型对喷射式制冷空调系统的喷射器进行CFD计算。真实气体模型占用较多的计算机资源,但它的计算结果更加真实。计算的目的在于得到在不同喷嘴直径条件下喷射器性能的变化和制冷系统性能的变化情况。在计算工况条件下,存在一最优的喷嘴直径Dn*(5mm),使得此时的喷射系数和系统COP最大。当Dn>Dn*时,喷射系数和COP随着喷嘴直径的增加而减少;当Dn相似文献   

喷射式空调系统的实验与数值模拟研究

利用二维轴对称,真实气体模型对喷射式制冷空调系统的喷射器进行CFD计算。搭建喷射式空调实验系统,进行喷射式空调实验,验证CFD模型的可行性。利用验证的CFD模型,进行实验工况以外的数值计算,得到了喷射器在不同发生条件、蒸发条件和冷凝条件下的性能变化。在喷射器结构确定,其它条件不变时,发生温度tg必须要在一定范围内,71℃≤tg≤95℃,喷射器才能正常运行。在计算条件下,蒸发温度te越高,喷射器的性能越好。冷凝温度tc要在一定范围内:20℃≤tc≤40℃,喷射器才能正常工作。当冷凝压力低于临界压力时,喷射器的性能表现出恒能力特性。