纯净空气来流的超音速燃烧室试验与数值模拟研究

超音速燃烧室试验设备需要加热空气达到所模拟的飞行状态的总焓,采用电阻加热器可以提供纯净的来流空气。西北工业大学建立了采用连续式电阻加热器的超音速燃烧室直连式试验平台。设备的初步调试结果显示:该电阻加热器最高可将流量0.73 kg/s的来流空气加热至1000 K,可以利用该平台进行低飞行马赫数的超音速燃烧室试验研究。本文利用该试验平台进行了超音速来流条件下的氢气燃烧试验研究,并在此基础上开展了氢气燃烧的数值模拟研究,数值模拟结果和试验结果吻合较好。     

液环泵喷射器三维流场数值模拟分析

利用ANSYS CFX分软件及湍流模型,通过改变液环泵喷射器的结构参数,模拟其内部的三维流动探讨了结构参数对喷射器内部流场及性能的影响;重点分析了引射压力、喉嘴距和面积比对喷射器性能的影响;得到了喷射器性能(引射气量、喷射系数等)随喉嘴距、面积比的变化规律;模拟结果表明:几何参数的改变极大的影响着波系结构;在给定的设计工况下,存在一个最佳的面积比(约为10.15)及一个最优的喉嘴距(20mm)对应于最大的喷射系数,为喷射器的优化设计提供了依据。     

Experiment and surge analysis of centrifugal two-stage turbocharging system

To study a centrifugal two-stage turbocharging system’s surge and influencing factors, a special test bench was set up and the system surge test was performed. The test results indicate that the measured parameters such as air mass flow and rotation speed of a high pressure (HP) stage compressor can be converted into corrected parameters under a standard condition according to the Mach number similarity criterion, because the air flow in a HP stage compressor has entered the Reynolds number (Re) auto-modeling range. Accordingly, the reasons leading to a two-stage turbocharging system’s surge can be analyzed according to the corrected mass flow characteristic maps and actual operating conditions of HP and low pressure (LP) stage compressors.     

驻室抽气压缩机及其与风洞性能相关性研究

为了研究驻室抽气压缩机及其与风洞性能的相关性,对E71-3离心压缩机进行了性能试验,并进行了驻室抽气性能测试。试验结果表明:(1)E71-3离心压缩机实测最高压比4.516,设计点多变效率81.8%,达到了设计要求。(2)风洞运行总压升高,压缩机多变效率降低。(3)风洞试验段Ma=0.9~1.1时,驻室抽气量对风洞模型区梯度的影响不大,但驻室抽气量超过4%后风洞马赫数均方根偏差明显增大;压缩机稳定在中等转速、适量抽气量的工况,且入口流量调节阀全开,风洞流场品质较好,运行成本最低。     

An experimental and numerical study on hydrodynamic characteristics of horizontal annular type water-air ejector

A water-driven annular type ejector loop is designed and constructed for air absorption. Fabricated ejector unit is horizontally installed in the loop, and annular water jet at the throat entrained atmospheric air through the circular pipe placed at the center of the ejector. The tested range of water flow rate is 160 L/min to 320 L/min and volumetric flow rate of water and air and local pressure are quantitatively measured using LabVIEW signal express program. For the quantitative measurement of bubble velocity, cinematic PIV technique using a high speed camera is adapted. In post processing, each bubble is used as seeding particles and ensemble averaged bubble velocity field at vertical plane of the ejector system is finally acquired. In the range of experiment, the bubble size distribution at downstream of the ejector seems to be quite uniform so that the flow can be classified as a homogeneous bubbly flow. In case of low range of water flow rate, the transition from bubbly flow to stratified flow occurs at the atmospheric outlet condition. As a comparative study, a numerical simulation on the same ejector shape is performed to understand the more detail hydrodynamic characteristics in the annular type ejector system. Homogeneous bubbly flow regime is used as default two-phase flow regime, and void fraction at the vertical plane of the ejector system is qualitatively compared with that of experiment. In volume flow rate comparison, numerical prediction agrees well with that of experiment where the homogeneous bubbly flow is maintained.     

Uncertainty analysis of the high pressure closed loop gas flow standard facility in NIM

High pressure air flow standard facilities, including the pVTt facility, sonic nozzle facility and closed loop facility were built in NIM at the end of 2014. The high pressure closed loop gas flow facility was the first closed loop facility in China. The system has 4 sets of 100 mm diameter turbine meters for the reference meters with a flow range of (40–1300) m³/h and a pressure range of (190–2500) kPa. To avoid uncertainties introduced during installation, the reference meters were designed to be calibrated in situ using the sonic nozzle facility. The uncertainty in the pressure measurement was reduced by installing an absolute pressure transducer in the manifold upstream of the reference meters, with differential pressure transducers used to measure the pressure drops across the reference flow meter and the test flow meter. The relative expanded uncertainty for the test meter can reach 0.20% (k = 2) as verified by comparison the sonic nozzle facility and the closed loop facility measurements.     

Experiment and surge analysis of centrifugal two-stage turbocharging system

To study a centrifugal two-stage turbocharging system’s surge and influencing factors, a special test bench was set up and the system surge test was performed. The test results indicate that the measured parameters such as air mass flow and rotation speed of a high pressure (HP) stage compressor can be converted into corrected parameters under a standard condition according to the Mach number similarity criterion, because the air flow in a HP stage compressor has entered the Reynolds number (Re) auto-modeling range. Accordingly, the reasons leading to a two-stage turbocharging system’s surge can be analyzed according to the corrected mass flow characteristic maps and actual operating conditions of HP and low pressure (LP) stage compressors.     

舱外服大循环量引射器优化设计与实验研究

为进一步提高舱外航天服供氧通风能力,对其引射器进行优化设计。采用一维气体动力学模型建立喷嘴控制方程;根据实验结果确定喷嘴等熵效率,设计缩放喷嘴;采用3D打印技术加工不同结构的引射器;利用氮气进行常压引射实验,研究挡板位置、喷嘴类型与喷嘴出口位置(Nozzle Exit Position,NXP)等结构参数对混合流量的影响,寻找最优的引射器结构。研究表明:挡板位置对引射器混合流量的影响与喷嘴类型相耦合。前移挡板,亚音速引射器混合流量可提高56.90%以上,而超音速引射器则降低12.08%以上。将渐缩喷嘴换为缩放喷嘴,混合流量可以提高1.81倍以上;对于挡板前移的亚音速引射器,则可提高36.90%以上。所有亚音速引射器均无法满足当前性能要求。然而,对于超音速引射器,对于所有的NXP,在典型工况下引射器循环量均可满足要求;存在最优的NXP使得混合流量最大。NXP为6 mm时,超音速引射器混合流量最大,为144.83 L/min(工作流绝对压力为0.503 MPa);在全工况下(工作流表压为0.30～0.55 MPa),混合流量可至少提高1.59倍。设计的最优引射器测试结果均满足性能要求。     

Optimization study on the isolator length of dual-mode scramjet

The dual-mode scramjet is a prime candidate for air-breathing propulsion engines given its broad speed range and high efficiency. The detailed structure of the pseudo-shock wave in the isolator is worth investigating. Therefore, the present study investigates the effect of isolator length on the pseudo-shock wave. We replicate the experimental work of the reference paper with a two-dimensional numerical model. Pressure distribution on the body surface is applied in the numerical validation. The numerical result is in good agreement with that of the existing experimental work. We simulate the thermal choking condition with a throttling device. As the throat area of throttling device decreases, the back pressure continues increasing and the pseudo-shock wave moves upstream. Avoiding unstart phenomenon is a key objective in the operation of dual-mode scramjet. Therefore, we investigate the critical condition shortly before unstart phenomenon occurs. The pseudo-shock wave structure is described by pressure distribution. Our main objective is to explore the effect of isolator length on the dual-mode scramjet. The optimal isolator length depends on the maximum back pressure and total pressure loss in the critical condition shortly before the unstart phenomenon occurs. The maximum back pressure in the critical condition is higher when the isolator length ranges from 8.7 to 20.7. The total pressure loss in the critical condition decreases at the beginning and then increases when the isolator length ranges from 8.7 to 20.7.

     

车载小型除氚装置催化氧化床设计

通过对目前国内外除氚方法的研究,采用负载型Pd贵金属催化剂,设计了一种适合特殊环境条件下的车载小型催化氧化除氚装置。本文详细阐述了装置的设计方法,原理及一般原则,并通过计算机系统仿真对装置的处理效果检验,达到了设计要求,满足了特殊环境的需要。     

An experimental study of supersonic dual coaxial free jet

A supersonic dual coaxial jet has been employed popularly for various industrial purposes, such as gasdynamic laser, supersonic ejector, noise control and enhancement of mixing. Detailed characteristics of supersonic dual coaxial jets issuing from an inner supersonic nozzle and outer sonic nozzles with various ejection angles are experimentally investigated. Three important parameters, such as pressure ratios of the inner and outer nozzles, and outer nozzle ejection angle, are chosen for a better understanding of jet structures in the present study. The results obtained from the present experimental study show that the Mach disk diameter becomes smaller, and the Mach disk moves toward the nozzle exit, and the length of the first shock cell decreases with the pressure ratio of the outer nozzle. It was also found that the highly underexpanded outer jet produces a new oblique shock wave, which makes jet structure much more complicated. On the other hand the outer jet ejection angle affects the structure of the inner jet structure less than the pressure ratio of the outer nozzle, relatively.     

Water cooling characteristics in an enclosed vacuum tank by water driven ejector

The general cooling tower is a device for cooling water in industrial condensers or heat exchangers. The present cooling towers have defects with noises, complicated structures and environmental problems. This paper focuses on a new water cooling system using the latent heat of evaporation in an enclosed vacuum tank and a water driven ejector system. Several experiments were carried out to improve high vacuum pressure and water cooling characteristics. The ejector performance was tested with various water temperatures. Based on the vacuum pressure of the water driven ejector, the water cooling characteristics were investigated for the condensed and vaporized air and the effect of increased evaporating surface area in an enclosed tank.     

低温制冷系统两级喷射器设计与性能分析

本文提出了一种用于渔船低温制冷系统的两级喷射器,并对其进行了优化设计和性能分析。为达到最大引射性能,提出了基于流场参数匹配的两级喷射器优化设计方法,使用计算流体力学仿真软件对两级喷射器进行了建模和参数优化。此外,采用了水冷式冷凝器来减小冷凝器与蒸发器之间的压差,从而获得了更高的引射比。研究结果表明,所设计的两级喷射器可使蒸发温度低至248.15 K,第一级和第二级喷射器最优面积比分别为11.8和6.5。中间压力在253～324 kPa之间,引射比先增加后减小,在中间压力为304 kPa时达到最大值0.096,此时系统能效比达到0.074。可以认为,采用优化设计的两级喷射器和水冷式冷凝器,利用渔船余热驱动的低温制冷系统具有较好的节能效果。     

空气压缩机模型级用于不同真实气体的气动性能研究

基于机器马赫数相等的相似变换准则,对不同真实气体工质同一离心压缩机模型级进行常温常压及高温高压下气动性能的数值研究。除了空气,选取的气体工质还包括二氧化碳和丙烯两个重介质以及一个轻介质甲烷。通过分析不同工质的物性和模型级气动性能变化规律,寻找影响不同工质模型级性能变化的主要因素。结果表明:在机器马赫数相等的条件下,工质远离临界区时,模型级内部流场受比热比影响较大,导致不同真实气体的级性能随比热比的变化而改变,流场内部流动损失及压力随比热比的增大而增大。当模型级进出口比热比变化较小时,比热比越大,级效率越低,压比越高,但能头系数变化较小;进出口比热比变化较大时,级性能变化比较大。     

Performance test and component characteristics evaluation of a micro gas turbine

This study aims to analyze engine performance and component characteristics of a micro gas turbine based on detailed measurement of various parameters. A test facility to measure performance of a micro gas turbine was set up and performance parameters such as turbine exit temperature, exhaust gas temperature, engine inlet temperature, compressor discharge pressure and temperature, and fuel and air flow rates were measured. The net gas turbine performance (power and efficiency based on the gas turbine shaft end) was isolated and analyzed. With the aid of measurement based simulation, component characteristic parameters such as turbine inlet temperature, compressor efficiency, turbine efficiency and recuperator effectiveness were estimated. Behaviors of the estimated characteristic parameters with operating condition change were examined and sensitivities of estimated parameters to the measured parameters were analyzed.     

烟气粉尘治理的气体引射装置设计计算

阐述烟气粉尘治理的气体引射的作用，射流喷嘴的设计，自由射流长度及附壁点的计算；气体引射效率的计算。给出在立窑烟气粉尘治理应用的实例。     

PEMFC 全功率变流量喷射器流场特性研究

针对质子交换膜燃料电池全功率氢循环对喷射器变流量的需求,提出并设计了不同嵌套方式的四喷嘴喷射器,以实现不同工况下变流量性能。为研究不同嵌套方式喷射器的流场特性及其循环性能,采用计算流体力学方法对喷射器进行建模和分析。结果表明,部分嵌套喷射器的内部流场比全嵌套喷射器的内部流场稳定;当二次流压力和背压不变时,一次流压力从6 bar(1 bar=100 kPa)增加到10 bar,部分嵌套喷射器引射比先上升后下降,在压力为7 bar时存在最大值;而全嵌套喷射器引射比是下降的趋势,通过与实验数据的比较,部分嵌套喷射器具有更优的性能;最后通过多喷嘴PWM逻辑控制,实现了170 kW燃料电池全功率变流量拟线性调控性能,满足燃料电池在变功率运行下的氢循环需求。     

凹槽火焰稳定器前缘结构对煤油超声速燃烧的影响

采用离散液滴模型、概率密度函数紊流燃烧模型和两方程紊流模型数值,模拟了双模态冲压发动机燃烧室内不同前壁面结构凹槽的超声速燃烧火焰稳定特性。在相同的计算条件下,数值分析结果表明:与具有正规凹槽结构的燃烧室相比,具有斜面凹槽结构的燃烧室:壁面静压分布更加合理;其内涡量比较强;燃烧室出口总压恢复系数和燃烧室效率都比较大。因而认为斜面凹槽火焰稳定器提高了混合和燃烧,优于正规凹槽火焰稳定器。     

超声速流下多供气空圆盘静压止推气体轴承性能分析

应用Fluent软件对多供气节流小孔盘静压止推气体轴承进行三维流场的模拟计算,分析供气小孔数、气膜间隙和供气压力对圆盘静压止推气体轴承性能的影响,并和Reynolds方程解的结果进行比较,分析气膜内发生超音速流和不发生超音速时气膜内的压力分布和马赫数情况.结果表明,应用Fluent数值模拟可以很方便地处理节流小孔进入到气膜内区域的复杂流场流动;增加供气孔数、减小气膜间隙和降低供气压力能够避免多供气孔静压止推气体轴承气膜内发生超音速.     

Sewerage force adjustment technology for energy conservation in vacuum sanitation systems

The vacuum sanitation is the safe and sound disposal approach of human excreta under the specific environments like flights, high speed trains and submarines. However, the propulsive force of current systems is not adjustable and the energy consumption does not adapt to the real time sewerage requirement. Therefore, it is important to study the sewerage force adjustment to improve the energy efficiency. This paper proposes an energy conservation design in vacuum sanitation systems with pneumatic ejector circuits. The sewerage force is controlled by changing the systematic vacuum degree according to the amount of the excreta. In particular, the amount of the excreta is tested by liquid level sensor and mass sensor. According to the amount of the excreta, the relationship between the excreta amount and the sewerage force is studied to provide proper propulsive force. In the other aspect, to provide variable vacuum degrees for different sanitation requirements, the suction and discharge system is designed with pneumatic vacuum ejector. On the basis of the static flow-rate characteristics and the vacuum generation model, the pressure response in the ejector circuit is studied by using the static flow rate characteristics of the ejector and air status equation. The relationship is obtained between supplied compressed air and systematic vacuum degree. When the compressed air is supplied to the ejector continuously, the systematic vacuum degree increases until the vacuum degree reaches the extreme value. Therefore, the variable systematic vacuum degree is obtained by controlling the compressed air supply of the ejector. To verify the effect of energy conservation, experiments are carried out in the artificial excreta collection, and the variable vacuum-degree design saves more than 30% of the energy supply. The energy conservation is realized effectively in the new vacuum sanitation systems with good application prospect. The proposed technology provides technological support for the energy conservation of vacuum sanitation systems.