主燃级喷嘴和燃油分级后雾化特性实验研究(“两机”专刊)

为优化高温升主燃烧室燃烧性能，对三级旋流主燃烧室开展雾化特性试验研究。预燃级喷嘴采用离心喷嘴压力雾化和气动雾化相结合，主燃级采用预膜式气动雾化。试验采用相位多普勒粒子分析仪对主预燃级喷嘴和燃油分级后的雾化特性进行研究，对比分析了不同头部压降和燃油流量在不同轴向截面和径向位置的液滴粒径分布，并利用高速摄像对不同工况下的喷雾形态进行了记录。试验结果表明：主燃级油雾粒径为50~80μm，气液比达到3.5即可达到良好的雾化水平。随着轴向距离延长，喷雾粒径变大，喷雾浓度变得均匀。燃油分级比增加可降低整体粒径约10μm，且主要影响中心区域，对雾锥外侧粒径影响不大。     

An error analysis and optimization method for combined measurement with binocular vision

The accurate measurement of surfaces of large aviation components is vital for the assessment of manufacturing and assembly quality of such components. To satisfy the measurement requirement of large-size components, most current researches pay more attention to combined measurement methods utilizing different measuring instruments, but the related researches on error analysis and optimization methods are not taken enough attention. This paper proposes a combined laser-assisted measurement method with feature enhancement techniques, and it also develops an error propagation model of the main factors affecting the overall measurement error in detail. Firstly, the surface of a large-size component is measured by the measurement system at multiple stations. Secondly, a control point coordinate system is established as a bridge to unify all local measurement data into the global coordinate system. To improve the overall measurement accuracy, the pixel extraction error as a key factor causing the overall measurement error is analyzed in detail. Next, the error propagation model is established, and some optimization strategies of layout for minimizing measurement error and transformation error are researched. Finally, experiments are carried out to verify the effectiveness of the proposed method. The results show that the measurement error of the proposed method reaches 0.073% and 0.14% with a 1D standard ruler and a flat plate, respectively.     

基于光场成像的快照式气膜孔三维测量技术

叶片气膜孔的几何参数对其冷却效率具有十分重要的影响，需采取有效手段对加工的气膜孔几何参数进行检测。基于光场成像原理，初步探索了单光场相机快照式三维测量技术在气膜孔检测上的应用。与其他光学测量技术相比，该技术仅通过一次拍摄，即可快速从捕获的单张原始光场图像中计算得到气膜孔的三维点云数据，其数据采集效率很高。实验中对一组标准量块进行了测量，展示了单光场相机应用于工业级精密测量的潜力。对实际叶片上气膜孔几何参数的检测结果初步表明了该技术应用于气膜孔三维测量的可能性。由于单光场相机成像系统的结构简单，易于操作且便于与其他传感器设备集成，可为气膜孔三维测量问题提供一种新的解决方案。     

某型惯性导航系统典型53#故障的排除及解析

某型惯性导航系统在飞机上时有故障发生,造成导航系统无法正常使用,其中较为突出的是惯导报53#环境温控故障。为降低该惯导在飞机上的故障率,通过研究环境温控回路的工作原理,解析其故障机理,并以几起典型53#故障的排除为例深入分析,提出有效的预防措施,以延伸修理深度,提高产品修理质量。     

面向航天器微低重力仿真的大型超平支撑平台精密装配技术研究

大型超平支撑平台作为航天器微低重力仿真的大型精密试验设备,具备大尺寸、高承载刚度、全自动精密调节等特点。通过对大型超平支撑平台装配要求及难点分析,构建装配系统组成,制定装配工艺流程,设计调节机构及调节工艺流程,并针对虚拟轮廓构建、精密测量、装配路径规划、调控策略等数字化自动装配关键技术进行研究,最终实现大型超平支撑平台的快速、精密测量与调节,高效率、高质量地完成200块平台的精确装配。     

Validation of non-linear split window algorithm for land surface temperature estimation using Sentinel-3 satellite imagery: Case study; Tehran Province,Iran

In recent years, land surface temperature (LST) has become critical in environmental studies and earth science. Remote sensing technology enables spatiotemporal monitoring of this parameter on large scales. This parameter can be estimated by satellite images with at least one thermal band. Sentinel-3 SLSTR data provide LST products with a spatial resolution of 1 km. In this research, direct and indirect validation procedures were employed to evaluate the Sentinel-3 SLSTR LST products over the study area in different seasons from 2018 to 2019. The validation method was based on the absolute (direct) evaluation of this product with field data and comparison (indirect) evaluation with the MODIS LST product and the estimated LST using the non-linear split-window (NSW) algorithm. Also, two emissivity estimation methods, (1) NDVI thresholding method (NDVI-THM) and (2) classification-based emissivity method (CBEM), were used to estimate the LST using the NSW method according to the two thermal bands of Sentinel-3 images. Then, the accuracy of these methods in estimating LST was evaluated using field data and temporal changes of vegetation, which the NDVI-THM method generated better results. For indirect evaluation between the Sentinel-3 LST product, MODIS LST product, and LST estimated using NSW, four filters based on spatial and temporal separates between pairs of pixels and pixel quality were used to ensure the accuracy and consistency of the compared pairs of a pixel. In general, the accuracy results of the LST products of MODIS and Sentinel-3, and LST estimated using NSW showed a similar trend for LST changes during the seasons. With respect to the two absolute and comparative validations for the Sentinel-3 LST products, summer with the highest values of bias (?1.24 K), standard deviation (StDv = 2.66 K), and RMSE (2.43 K), and winter with the lowest ones (bias of 0.14 K, StDv of 1.13 K, and RMSE of 1.12 K) provided the worst and best results for the seasons in the period of 2018–2019, respectively. According to both absolute and comparative evaluation results, the Sentinel-3 SLSTR LST products provided reliable results for all seasons on a large temporal and spatial scale over our studied area.     

复杂薄壁构件自适应加工工艺几何模型重构

随着制造理念和制造水平的不断提高，大量复合制造工艺背景下的近净成形叶片被应用到现役或在研的航空发动机中。该类叶片是典型的复杂薄壁结构零件，无精确定位基准，且成形一致性差。采用传统叶身定位，加工后的前/后缘、榫齿形状和位置精度均难以保证，从而导致产品一致性差，易超差与合格率低。针对以上问题，提出一种面向自适应加工的复杂薄壁结构零件工艺几何模型重构方法。首先，建立复杂曲面的采样点分布模型，快速获取叶片精确成型区域的位置和形状；其次，提出基于特征曲线相似变形的模型重构算法，精确重构前/后缘非精确成型区域的工艺几何模型；最后，通过精锻叶片自适应加工试验进行验证。试验结果表明：该方法可有效满足以精锻叶片为代表的复杂薄壁构件自适应加工要求。     

单组元300N发动机低温试验研究

为探究低温环境下单组元300N发动机的工作特性，揭示影响发动机低温性能的主要影响因素，以300N发动机为试验对象，开展了模拟飞行工况的发动机低温试验。给出了低温试验研究方法，分别从温度差异对发动机性能影响、催化剂活性差异对发动机低温启动特性影响和低温对电磁阀响应特性影响等方面获得研究结果。结果表明，低温是影响发动机低温性能的主要影响因素，-48℃条件催化剂无法完成推进剂的催化分解，发动机发生爆炸；-30℃条件下起活时间为80.5～87.5ms，发动机可正常启动，且启动温度与起活时间呈指数关系；催化剂批次差异也对发动机低温工作性能产生一定影响，不同批次催化剂低温起活时间的差异可达91ms；低温试验过程中，电磁阀的关闭受到低温推进剂粘性和背压的影响，产生了明显的迟滞现象，延迟时间约100ms，对发动机在轨的精准控制存在一定影响。     

低压天然气喷射的船用二冲程低速双燃料发动机爆震研究

为了解决大缸径船用预混天然气双燃料发动机的爆震问题，并拓展天然气的稀燃边界。基于三维数值模拟的方法对大缸径船机进行了仿真模拟。分析了大缸径双燃料发动机爆震的特点，并对缸内涡流强度和废气再循环（EGR，Exhaust Gas Re-circulation）率对爆震的影响进行了研究。研究结果表明：大缸径预混天然气发动机的爆震位置往往发生在气缸边缘，火焰面的传播过程是引起缸内爆震的主要因素。随着缸内涡流从无到有的增强，缸内的爆震强度随之增强；当涡流到达一定程度后，随着涡流的增强，缸内的爆震强度反而降低；缸内加入EGR可以提高天然气当量比的同时减少爆震的强度，可以拓展天然气的稀燃边界。     

重复固溶对Inconel 718合金组织性能的影响

以982℃固溶水冷状态的Inconel 718合金棒材为研究对象,分析该合金经重复固溶再时效处理后的组织性能,并与直接时效处理进行对比。结果表明:在941~1010℃范围内重复固溶,随着固溶温度的升高,晶粒无明显变化,但是δ相含量逐渐减少,主要强化相γ′′的析出量增多,使合金硬度、高温拉伸强度和高温持久寿命显著提高,高温拉伸塑性、高温持久塑性在982℃固溶时达到极大值。与直接进行时效处理相比,经982℃重复固溶再时效处理后的组织性能无明显变化,更低的重复固溶温度对性能不利,而更高的重复固溶温度则使性能提高。