弹性环式挤压油膜阻尼器动力设计方法

弹性环式挤压油膜阻尼器(ERSFD)与传统挤压油膜阻尼器(SFD)相比,在动力特性方面具有一定的特色.以燃气涡轮发动机用ERSFD为对象,基于有限元挤压油膜理论对ERSFD的弹性环支承刚度、油膜压力场分布和油膜阻尼等特性进行了研究.根据ERSFD的结构特点,利用有限元法分析其动力特性不仅具有模型简单、计算量小的优点,而且能考虑到各种复杂的边界条件及封严装置.研究结果表明,本计算方法和结果可以作为ERSFD结构优化的依据.与SFD(Squeeze Film Damper)相比,ERSFD具有分段式油膜间隙,可利用弹性环的弹性变形来调整油膜间隙,将油膜间隙控制在一个合适的范围内,从而有效地避免传统SFD在一定工作条件下的非线性振动现象的发生.      

模型机匣/叶片的包容性数值分析

应用有限元分析方法研究了模型叶片飞断后撞击模型机匣的响应,模拟了不同厚度机匣结构和不同材料的模型叶片以及叶片不同飞断转速下机匣的包容能力,对不同应变率下机匣的响应进行了计算和对比分析,并评价了主要参数对机匣响应的影响。计算结果与试验结果对比表明两者具有较好的一致性。      

橡胶"O"形密封圈结构参数和失效准则研究

利用大变形、接触的非线性有限元理论建立了某固体火箭发动机密封结构的二维轴对称模型,用有限元软件计算出该结构在工作状态下的变形和应力。通过计算可知,在橡胶“O”形密封圈与上下法兰接触的位置产生最大的接触压应力,在密封槽槽口转角位置产生最大的剪切应力。对密封性能的各结构参数进行了分析,讨论了上下法兰张开间隙、初始压缩率、密封槽槽口及槽底倒角半径、密封槽宽、密封圈材料等典型参数的影响:上下法兰张开间隙、密封圈的初始压缩率对最大接触压应力的影响较大,而密封槽槽口和槽底处倒角半径对剪切应力影响明显。三维壳体结构的有限元分析结果表明,上下法兰在内压作用下产生不均匀的张开间隙,体现了三维结构的特点。不均匀的张开间隙与二维轴对称结果对比可知,以最小间隙作为设计间隙,二维轴对称分析模型可取代三维模型来分析该结构的密封性能。最后,确定了“O”形圈密封结构的最大接触应力和剪切应力失效准则。     

某型航空发动机弹性涨圈椭圆模型的求法

某型航空发动机主轴滑油采用弹性涨圈密封,涨圈成型的好坏决定了滑油的密封效果。原涨圈椭圆成型采用热定型工艺进行,定型尺寸不稳定、零件合格率低。拟采取直接加工椭圆的方式替代原有热定型工艺。为了得到自由状态下的涨圈椭圆模型,采取有限元分析方法与三维建模软件相结合的方式得到涨圈自由状态下的椭圆三维模型。经数控编程加工验证,该方法求出的椭圆模型能保证涨圈开口闭合后的圆度在0.05mm以内,满足实际加工工艺要求。     

开口圆环过盈联接力学分析

利用能量原理对过盈联接的开口圆环力学模型进行研究,求得开口圆环开口端张开位移的计算公式,分析开口圆环过盈联接的弹力和正应力。数值算例分析了开口圆环与不同外径缸套过盈联接的弹力和最大正应力。结果表明:开口圆环过盈联接的弹力和最大正应力随圆环开口角度和缸套外径的增大而增大,但缸套外径对其有更大影响;为开口圆环的设计提供一定的理论依据。     

Relationship of the diffuse aurora and SAR arc dynamics to substorms and storms

Investigation results of a diffuse aurora (DA) and stable auroral red (SAR) arc dynamics based on spectrophotometric observations at the Yakutsk meridian (199°E geomagnetic longitude) are presented. The relationship of an equatorward extension of DA in the 557.7 nm emission to a substorm growth phase during the magnetospheric convection intensification after the turn of IMF B_Z to the south is shown. The formation of SAR arc during the substorm expansion phase is investigated. The association of SAR arc dynamics with the development of asymmetric ring current (substorm injection) during the main phase of a storm is analyzed. It is shown how the pulsating precipitations of energetic ring current particles develop in the outer plasmasphere based on photometric observations.     

Testing relativity with orbiting clocks

We describe the background and status of a superconducting microwave clock suitable for relativity experiments in earth orbit. The project has the capability of performing improved tests of Lorentz invariance via a Michelson–Morley type experiment, and setting new limits on nine parameters in the Standard Model Extension. If flown with a high stability atomic clock, a Kennedy–Thorndike experiment along with additional tests in general relativity could be performed.     

JSJ精密水准仪经纬仪综合检验仪原理及误差分析

介绍了一种最新研制的在室内检定高精度水准仪经纬仪的计量标准仪器，并分析了该仪器设计原理及误差来源。     

Coastal sea level measurements using a single geodetic GPS receiver

This paper presents a method to derive local sea level variations using data from a single geodetic-quality Global Navigation Satellite System (GNSS) receiver using GPS (Global Positioning System) signals. This method is based on multipath theory for specular reflections and the use of Signal-to-Noise Ratio (SNR) data. The technique could be valuable for altimeter calibration and validation. Data from two test sites, a dedicated GPS tide gauge at the Onsala Space Observatory (OSO) in Sweden and the Friday Harbor GPS site of the EarthScope Plate Boundary Observatory (PBO) in USA, are analyzed. The sea level results are compared to independently observed sea level data from nearby and in situ tide gauges. For OSO, the Root-Mean-Square (RMS) agreement is better than 5 cm, while it is in the order of 10 cm for Friday Harbor. The correlation coefficients are better than 0.97 for both sites. For OSO, the SNR-based results are also compared with results from a geodetic analysis of GPS data of a two receivers/antennae tide gauge installation. The SNR-based analysis results in a slightly worse RMS agreement with respect to the independent tide gauge data than the geodetic analysis (4.8 cm and 4.0 cm, respectively). However, it provides results even for rough sea surface conditions when the two receivers/antennae installation no longer records the necessary data for a geodetic analysis.     

用测长机校准数显千分表测量结果的不确定度评定

介绍了0～25 mm数显千分表的示值误差测量结果的不确定度分析,表明了用TWIN-CHECK1200测长机进行校准的可行性.