高超声速飞行器一体化设计的新选择——缩颚进气道

介绍了一种应用于高超声速飞行器的新型三维内乘波进气道,即缩颚进气道(JAWS InlET)的国外研究进展。对比基准进气道设计,分析了这种进气道的设计方法、流场特征和性能特点。国外研究结果表明,这种进气道通过四道激波面的设计,改善了激波/边界层以及激波/激波的相互作用,提高了进气捕获量,减少了溢流损失,有效地提高了推阻比。因此,可望通过对缩颚进气道的进一步研究,使其成为高超声速飞行器一体化设计的新选择

Advanced Laser Measurement Technology for Aeroengine Combustor Research and Development

在航空发动机燃烧室的研发过程中,传统的测量手段往往有时无法实施或不能满足精确捕捉流场信息的要求,发展新型、高精度测量以及先进诊断技术势在必行。重点介绍了适用于航空发动机燃烧室测量的先进激光测试技术,并与传统测量方法进行了比较。发动机燃烧室内的流场测量包括速度测量、温度和组分质量分数测量。氢氧根离子标记测速(HTV)方法适用于有化学反应流场的速度测量;而拉曼散射测量技术可以同时测量多种组分的质量分数和温度。利用这些激光测量技术的特点,可以使其在燃烧室的点火、贫油熄火及排放等性能的研究中发挥重要作用。The traditional methods of measurement can't meet the requirements of accurate capturing of the flow field in the development process of the aeroengine combustor.Therefore,the development of high-precision measurement and diagnostic techniques was imperative.The advanced laser diagnostic tools suitabling for aeroengine combustor measurement were introduced importantly and compared with the traditional measurement methods.The flow field measurement in the combustor include the measurement of velocity,temperature,and species concentration.Hydroxyl Tagging Velocimetry(HTV) method is applicable to the velocity measurement in the chemical reaction flow field.Raman scattering technology can measure a variety of species concentrations and temperature simultaneously.The laser diagnostic technique would play an important role in the study of ignition,extinction,and pollutant emission characteristics of the aeroengine combustor.国家自然科学基金(11002125和51106131);中央高校基本科研业务费专项资金(2010121045);教育部留学人员启动资金(J20120104)资

Performance Analysis of Three Kinds of Aero-Engine with Inter-Stage Turbine Burner

为探究级间燃烧室对各种航空发动机的性能影响,利用热力循环原理分别计算了在有无级间燃烧室的情况下涡喷、涡扇和涡轴发动机的性能结果并与实际型号做出对比。通过计算获得了上述三种发动机在加入级间燃烧室后的单位推力和耗油率随飞行马赫数等参数在一定范围内变化的曲线。结果表明加入级间燃烧室后对各种发动机的动力性能提升都在10%以上,个别涡轴发动机可达30%。同时若能将加入级间燃烧室后增加的质量控制在一定范围内,则对于各型发动机均可提高其推重比。In order to investigate the effects of the inter-stage turbine burner( ITB) on aero-engines,the thermodynamic cycle analysis was performed to demonstrate the performance of three kinds of aero-engines with the inter-stage turbine burners.The performance curves for different flight and operation conditions were obtained by calculation.Results show that specific thrust can be improved by at least 10%,and for one turboshaft engine the specific thrust even can be improved by 30%.Based on comparison between the real aero-engine performance and the calculation results,the errors are acceptable and the thrust-weight ratios show the potential capability of ITB application.国家自然科学基金(11002125;51106131); 中央高校基本科研业务费专项资金(2013121019

壁面微通道冷却对旋流燃烧室性能影响实验

为了探索微通道高效换热技术在低污染燃烧室壁面冷却中的应用,实验研究了壁面微通道冷却对模型旋流燃烧室性能的影响。结果表明:微通道结构对燃烧室热壁面具有显著的冷却效果,在雷诺数小于350时,雷诺数增加对壁面冷却有明显提升作用,在雷诺数大于350后,雷诺数的增大对冷却效果提高的促进作用减小;雷诺数增大对相同进气工况下CH*化学发光信号表征的火焰时均结构几乎不产生影响,但在个别工况下会使火焰产生黄色火星,甚至间歇地产生黄色火焰,带来不完全的燃烧;雷诺数增大会增强微通道对流换热程度,加大壁面传热速率,加剧火焰和微通道换热间的相互作用,使火焰表面发生较大的热量损失,最终造成CO排放量增加,NOx排放量降低,并使整体燃烧效率下降。国家自然科学基金(51406171);;福建省自然科学基金(2016J06011);;中央高校基本科研业务费(20720180058);;航空科学基金(20152868006

Effects of Pre-Diffuser on Performance of Dump Diffuser

研究了突扩扩压器中前置扩压器各参数与总压损失和静压恢复间的关系。采用实验与fluEnT计算结合的方法,通过水槽PIV实验得出扩压器内的流场信息,对照不同的湍流模型,得出最佳的计算方案。根据此计算方案计算不同的扩张角下前置扩压器性能的变化,得出各参数之间的规律。结果表明雷诺应力模型能够较好地预测扩压器内部流场;前置扩压器扩张角存在一个最佳值,大于最佳值前置扩压器会出现流动分离;结合理论分析和计算数据总结出计算前置扩压器总压损失系数和静压恢复系数的公式,利用此公式还可求出最佳的前置扩张角和前置扩压器长度,计算误差在5%左右。Diffuser is one key component of the gas turbine combustor following the compressor.Its primary function is to slow down the air flow delivered by the compressor in order to promote efficient combustion and avoid large total pressure losses.An experimental and computational study of cold flow in the dump diffusers was presented.The main aims were to evaluate the influence of pre-diffuser wall angle and pre-diffuser length on the performance of dump diffusers,and to identify the pressure loss mechanisms.PIV experiments were conducted in a simplified test model to help choose of congruent turbulence model.It was observed that apparent flow separation occurred on pre-diffuser wall when pre-diffuser wall angle amplified to certain degree.The pre-diffuser exit flow was distorted,indicating that the uniform exit conditions typically assumed in the diffuser design were violated.Skew distribution of the pre-diffuser outlet flow can result in strong transverse mixing for liquid,the total pressure loss of pre-diffuser increases significantly.The formula of the total pressure loss coefficient and the pressure recovery coefficient was developed.The optimal pre-diffuser length and pre-diffuser wall angle can be conveniently obtained by this equation,the calculation error was less than 5%.中央高校基本业务费(2013121019); 航空基金(20132268003

Potential impacts of pandemics on global warming, agricultural production, and biodiversity loss

The rising frequency of infectious diseases under climate change poses an emerging threat to environmental and agricultural sustainability by consuming large quantities of materials. The demand for crops to produce personal protective equipment (PPE) competes for land and fertilizers, leads to cropland expansion, and accelerates climate change, but the ecological impacts remain unclear. Here we explore the impacts of pandemics on global warming, agricultural production, and biodiversity loss in an Earth system model by developing relationships between consumption of PPE and the rate of infection during COVID-19. Meeting the demand for PPE would increase production of cotton lint, corn, and natural rubber, which accelerates global warming by 0.2°C with 1.8% additional species losses by 2100. Our results suggest that the risks of public health, food security, climate change, and ecological integrity have been connected to each other, which should be considered when predicting the impacts of future pandemics

Experimental investigation of airflow distribution for a novel combustor mode

This paper investigated the airflow distribution performance of the combustor which utilized trapped vortex in the cavity to improve the flame stability. Hole-filling method was used to study trapped vortex combustor airflow distribution at normal temperature and pressure condition. The influence of inlet velocity and mainstream flow-passage height were investigated. The results show that, inlet velocity hardly impacts the airflow distribution of trapped vortex combustor, but chamber height is a key parameter for airflow distribution. The size, number and opening area of the holes in trapped vortex combustor are important to airflow distribution, and increasing cavity back body air flow could bring well lean blowout limit. The research results may serve as a useful reference in further development and engineering application of trapped vortex combustor

CFD numerical simulation of Hyshot scramjet

以HySHOT超燃冲压发动机试验为研究对象,分别对冷流和燃烧工况进行了Cfd数值模拟.冷流模拟计算得到的壁面压力与试验结果吻合良好,且数值计算压力分布对采用的湍流流动模型不敏感;但是采用不同的湍流流动模型计算的湍流参数(湍动能和耗散率)差别很大,会对氢气燃料与气流的掺混产生重要影响,进而影响燃烧模拟结果.采用SST(SHEAr STrESS TrAnSPOrT)k-ω湍流流动模型和EdM(Eddy dISSIPATIOn MOdEl)湍流燃烧模型得到的模拟结果与试验结果基本吻合,但是计算压力峰值略靠后.对8个不同氢气燃料喷射角度的工况进行数值模拟结果表明喷射角度为99°和114°时燃料和空气混合最好、燃烧效率可达到最高.CFD numerical simulation was carried out for cold flow and combustion flow of the Hyshot scramjet to test the accuracy of turbulence flow model and turbulent combustion model.For cold flow,the predicted wall pressure profile was in accurate agreement with experimental data and the simulation result was insensitive to turbulence flow model choice.However,the predicted field of turbulence variables(turbulence kinetic energy and its dissipation rate)in cold flow is strongly influenced by turbulence flow model choice;these turbulence variables affect the mixing of hydrogen fuel and air and the subsequent combustion.Indeed,the simulation of combustion flow showed strong dependence on turbulence flow model and turbulent combustion model choice.The best combustion simulation result with SSTk-ωturbulence flow model and EDM turbulence combustion model has good agreement with experimental wall pressure data,but the pressure peak location is slightly deviated.The effect of fuel injection angle was also simulated.Eight injection angles of hydrogen fuel were tested and it was shown that the scramjet has best fuel/air mixing and combustion efficiency with injection angles of 99°and 114°.国家自然科学基金(51106131;11002125;51206057); 中央高校基本业务费专项资金(2010121045

Flame Curvature Effect on NO Emission of the Hydrogen Diffusion Flame

使用不同的H_2/O_2化学反应机理和nO_X化学反应机理模拟了平面对冲火焰。通过和实验数据比较确定了最优的化学反应机理。使用该化学反应机理模拟了管形对冲火焰。通过对比平面拉伸火焰和管形拉伸火焰,突出了火焰曲率对H_2扩散火焰温度和nO排放的影响。分析显示正曲率提高火焰温度,负曲率降低火焰温度,由于nO生成对温度的敏感性,正曲率火焰的nO排放明显高于平面火焰,反之,负曲率火焰的nO排放大大低于平面火焰。The opposed jet H_2 diffusion flames are simulated with OPPDIF code and different H_2/O_2 and NO_x mechanisms.The simulations with 2004 UCSD NO_x mechanism and 2005 UCSD H_2/O_2 mechanism are identified to have the best agreement with the experimental flame temperature and NO emission.With those mechanisms,the tubular H_2 diffusion flames are simulated with modified OPPDIF code and compared with the plane opposed jet flames.The comparison result shows that the positive flame curvature enhances the preferential diffusion of H_2 and increases the flame temperature and NO emission;and vice versa for the negative curvature.The flame curvature can change the NO emission 6 times for the tested H_2 diffusion flames with constant stretch rate 100 s--(-1).国家自然科学基金资助项目(No.10702064);中央高校基本科研业务费专项资金资助项目(No.2010121045

Aeroacoustic and flow field features of ultrasonic atomizer based on Hartmann resonance tube

采用试验与数值模拟相结合的方法研究了谐振腔孔径、谐振腔深度、谐振腔与射流喷孔距离以及喷嘴压比(NPR)对基于Hartmann谐振腔(HRT)的气动式超声波雾化喷嘴外部流场及声场的影响.结果表明:当喷嘴压比大于2时,喷嘴压比增大对声场频率影响较小;当喷嘴压比小于2时,谐振腔依然能够产生高频声场,但其频率较高喷嘴压比时产生的小.当谐振腔深度小于1倍射流喷孔孔径时,此时高频声场主要由射流的不稳定性引发,声场频率与谐振腔深度经验关系式此时并不适用;当谐振腔孔径大于1.75倍射流喷孔孔径时,声场频率大小有降低趋势.谐振腔与射流喷孔距离与声场频率关系紧密,当谐振腔放置在自由射流压力增大区域时,才可获得理想高频声场.Experimental and numerical studies were carried out to investigate the effects of operation parameters,such as diameter of resonance tube,resonance tube depth,jet nozzle hole to resonance tube spacing and nozzle pressure ratio(NPR),on the flow and acoustic field characteristics of a ultrasonic atomizer based on the Hartmann resonance tube(HRT).The modifications of the geometry of HRT in spectral and flow field characteristics were studied in detail.Result shows that that,when NPR is higher than 2,the increase of NPR has little effect on the frequency,however,when NPR is lower than 2,the lower frequencies of the acoustic field are obtained.The simulation results of flow field suggest that when the length of the resonance tube is smaller than diameter of jet nozzle hole,the reciprocating phenomenon of flow in the cavity is dampened,leading to a decrease of acoustic field frequency compared with cases having longer resonance tube length,and the classical relation between acoustic field frequency and tube resonance length is not appropriate for these situations.Also,the oversized diameter of resonance tube(typically,the diameter of resonance tube more than 1.75 times the diameter of jet nozzle hole)results in a lower oscillation acoustic field frequency for the interaction of the reciprocating and the shock is weakened.Furthermore,resonance occurs when the cavity is put in the regions where pressure arises for free jet.国家自然科学基金(51406171);; 中央高校基本科研业务费(20720150180);; 福建省自然科学基金(2015J05111