燃烧室工作过程对冲压发动机性能潜力的影响研究

用准一维分析方法,在相同的入流条件下,假设将当量比为1的燃料热量全部添加到气流中,研究了燃烧室工作过程与性能之间的关系。结果表明,随着特征马赫数的增加,在相同飞行马赫数下,亚声速燃烧室所需扩张比逐渐减小,而双模态燃烧室所需扩张比逐渐增大;亚声速燃烧室出现所需最小扩张比和最大比冲的特征马赫数分别是1和0,双模态燃烧室在最小特征马赫数时所需扩张比最小,获得的比冲最大,且与亚声速燃烧室能获得的最大比冲相差不大,在飞行马赫数4、5、6时,差值分别为5%、4%、3%;特征马赫数在亚声速范围内变化时发动机比冲的曲线比较平缓;壁面摩擦系数的变化对燃烧室所需扩张比的影响大于对比冲的影响。直连式实验获得的等截面燃烧室极限加热量数据证明了本方法的合理性。     

Estimation of vertically integrated water vapor in Hungary using MODIS imagery

Information about the amount and spatial structure of atmospheric water vapor is essential in understanding meteorology and the Earth environment. Space-borne remote sensing offers a relatively inexpensive method to estimate atmospheric water vapor in the form of integrated water vapor (IWV). The research activity reported in the present paper is based on the data acquired by the HRPT/MODIS (High Resolution Picture Transmission, MODerate resolution Imaging Spectroradiometer) receiving station established in Budapest (Hungary) by the Space Research Group of the Eötvös Loránd University. Integrated water vapor is estimated by the remotely sensed data of the MODIS instrument with different methods and also by the operational numerical weather prediction model of the European Centre for Medium-Range Weather Forecasts (ECMWF). Radiosonde data are used to evaluate the accuracy of the different IWV fields though it has been pointed out that the in situ data also suffers from uncertainties. It was found that both the MODIS and the ECMWF based fields are of good accuracy. The satellite data represent finer scale spatial structures while the ECMWF data have a relatively poor spatial resolution. The high quality IWV fields have proved to be useful for radiative transfer studies such as the atmospheric correction of other satellite data from times different than the overpass times of satellites Terra/Aqua and the forecast times of the model data. For this purpose the temporal variability of IWV is scrutinized both using ECMWF and MODIS data. Taking advantage of Terra and Aqua overpasses, the mean rate of change of IWV estimated by the near infrared method was found to be 0.47 ± 0.45 kg m⁻² h⁻¹, while it was 0.13 ± 0.65 kg m⁻² h⁻¹ based on the infrared method. The numerical weather prediction model’s analysis data estimated −0.01 ± 0.13 kg m⁻² h⁻¹ for the mean growth rate, while using forecast data it was 0.24 ± 0.18 kg m⁻² h⁻¹. MODIS data should be used when available for the estimation of the IWV in other studies. If no satellite data are available, or available data are only from one overpass, ECMWF based IWV can be used. In this case the analysis fields (or the satellite field) should be used for temporal extrapolation but the rate of change should be calculated from the forecast data due to its higher temporal resolution.     

串联式TBCC发动机模态转换模拟

为开展涡轮基组合循环(TBCC)发动机模态转换过程研究,基于某小型涡喷发动机,应用串联式TBCC发动机总体性能数值计算程序进行性能计算。根据沿飞行轨道TBCC发动机冲压涵道与涡轮发动机涵道气流混合过程中的参数变化规律,开展模态转换过程模拟。分析了不同等动压头、加力/冲压燃烧室进口马赫数、出口温度等主要参数对发动机性能的影响。根据小型串联式TBCC发动机模态转换过程和沿飞行轨道的发动机稳态特性模拟,确定了较为合理的模态转换区间,并得到了推力、耗油率等发动机性能参数。研究表明:不同动压头对应不同的模态转换马赫数,加力/冲压燃烧室进口马赫数和出口总温对模态转换马赫数并无影响。     

Magnetic levitation of large water droplets and mice

We report successful levitation of large water droplets and mice using a newly built variable gravity simulator. The simulator consists mainly of a superconducting magnet with a room temperature accessible experimental levitating space. The superconducting magnet generates a field and field gradient product that is large enough to levitate water and many other common liquids. The warm bore of the magnet has a diameter of 66 mm, large enough to levitate small mammals. We demonstrate that water drops up to 50 mm in diameter and young mice can be levitated in the system. The capability of levitating large water drops and biological systems offers new opportunities for conducting detailed and in-depth study of properties of fluids and biological systems in reduced gravity environments.     

工程施工中深基坑高程放样的误差分析

论述了市政工程施工中深基坑高程放样方法,对放样过程中产生的误差及误差的大小进行了分析。本测量放样方法可以满足给排水工程施工,以及符合高程精度要求的验收规范。     

Global water vapour distribution in the upper troposphere and lower stratosphere during CRISTA 2

Water vapour measurements during the second mission of the CRyogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) instrument are presented in the altitude regime 8–20 km. Mixing ratios are shown on isentropic surfaces (300–500 K) as global zonal means and as averages in 60° longitude sectors. Transports are indicated to occur preferentially on isentropic surfaces in the northern hemisphere, but not in the tropics and in the south. The hygropause is found shifted away from the equator towards the winter hemisphere. The amount of shift is longitude dependent and can be as great as 20–30°. The water content of the hygropause area shows considerable zonal asymmetries.     

Four-month Moon and Mars crew water utilization study conducted at the Flashline Mars Arctic Research Station,Devon Island,Nunavut

A categorized water usage study was undertaken at the Flashline Mars Arctic Research Station on Devon Island, Nunavut in the High Canadian Arctic. This study was conducted as part of a long duration four-month Mars mission simulation during the summer of 2007. The study determined that the crew of seven averaged 82.07 L/day over the expedition (standard deviation 22.58 L/day). The study also incorporated a Mars Time Study phase which determined that an average of 12.12 L/sol of water was required for each crewmember. Drinking, food preparation, hand/face, oral, dish wash, clothes wash, shower, shaving, cleaning, engineering, science, plant growth and medical water were each individually monitored throughout the detailed study phases. It was determined that implementing the monitoring program itself resulted in an approximate water savings of 1.5 L/day per crewmember. The seven person crew averaged 202 distinct water draws a day (standard deviation 34) with high water use periods focusing around meal times. No statistically significant correlation was established between total water use and EVA or exercise duration. Study results suggest that current crew water utilization estimates for long duration planetary surface stays are more than two times greater than that required.     

CRISTA-NF measurements of water vapor during the SCOUT-O3 Tropical Aircraft Campaign

The new remote sensing experiment CRISTA-NF (Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere – New Frontiers) successfully participated in the SCOUT-O3 Tropical Aircraft Campaign in November and December 2005. CRISTA-NF operated aboard the high-altitude research aircraft M-55 Geophysica. Mid-infrared spectra (4–15 μm) were measured in the limb sounding geometry with high spatial resolution (250 m vertical sampling, 5–15 km along track sampling). Measurements were carried out during transfer flights between Oberpfaffenhofen, Germany, and Darwin, Australia, as well as during several local flights near Darwin. Water vapor volume mixing ratios in the upper troposphere and lower stratosphere were derived from the CRISTA-NF radiance measurements by utilizing a rapid radiative transfer forward model and the optimal estimation retrieval approach. CRISTA-NF water vapor measurements below the hygropause have a total retrieval error of 15–40% (i.e. root mean square of accuracy and precision). The systematic terms are dominating in the retrieval error budget. The contributions of a priori information to the retrieval results are less than 5–10%. The vertical resolution of the observations is about 250–500 m when permitted by instrument sampling. In this paper we present first results for three transfer flights of the campaign. Being generally in good agreement with corresponding ECMWF operational analyzes, the CRISTA-NF measurements show significantly higher variability and local structures in the upper tropospheric water vapor distributions.     

碳氢燃料超燃研究与应用

通过分析与试验表明 ,技术风险小、性能可靠、近期能够实现的、以煤油为燃料的弹用冲压发动机是一种适宜于飞行Ma =6左右的高超声速导弹的推进装置。采用尾喷管几何喉道可调的方法 ,有利于提高煤油冲压发动机亚燃工况的性能 ,满足飞行器对低马赫数 (Ma=2 5左右 )接力与加速状态推力特性的要求。以煤油与氢为燃料的双燃料冲压发动机具有广阔的应用前景     

旋流燃烧室对固体燃料冲压发动机药柱表面传热以及燃速的影响

为研究旋流燃烧室对固体燃料冲压发动机(SFRJ)药柱表面传热以及燃速的影响,以高密度聚乙烯(HDPE)为燃料,对旋流和无旋工况下的固体燃料冲压发动机进行了连管实验研究,并且编制了二维轴对称湍流燃烧仿真程序,采用流固耦合传热的方法以及非定常时间推进方式,对实验工况进行了数值模拟。结果表明:①药柱表面热流密度对燃速有显著影响,在回流区与附着点处,药柱表面的对流换热能力要明显优于再发展区;②在旋流工况下,在离心力与切向速度的作用下,使热解产物在药柱表面附近区域停留时间更长,有助于热解产物的充分反应,并且明显增强药柱表面对流换热能力,与无旋工况相比,提高幅度可达100%,并且在旋流工况下发动机可更快建立自持燃烧;③通过实验研究发现,旋流的引入提高发动机的燃速有积极作用,增幅可达26%,但会导致固体燃料冲压发动机补燃室压强出现周期性振荡。