热交换对喷气发动机过渡过程影响分析

给出一种用于估算气流与零部件间热交换对过渡过程影响的方法。利用该方法计算了某双轴涡扇发动机在加速过程中各主要零部件与气流间的热交换随加速时间的变化，各部件热交换对推力响应的影响；计算和分析了该发动机在相同供油规律下“冷”和“热”两种加速过程，估算了典型部件换热面积和质量对加速性的影响。计算结果的分析表明：高温部件与气流的热交换对喷气发动机的过渡过程有不容忽视的影响；相同供油规律下由于热交换使“冷”和“热”加速过程的差异十分显著，“冷”加速过程允许采用补偿供油改善加速性；零部件换热面积和质量的估算精度对加速性有一定的影响，但不显著。     

加速寿命试验的理论基础(Ⅰ)

提出了有效的加速寿命试验对加速系数的要求，讨论了加速系数的性质与用途，并给出了常见的失效分布族。     

轴对称充液贮箱有加速度时的等效建模

用空间等效摆模型描述航天器储箱内液体晃动。根据液体晃动建模型与边界条件,获得了液体在贮葙腔内作涡旋运动时的赫姆霍兹方程。研究有加速度的平衡状态及小幅运动时固定腔体中理想流体的横向运动,分别求出每个腔体在固定基座上的固有频率和振型函数。航天器具横行速度和姿态运动时考虑航天器运动对加速度势的影响,给出液体对主刚体的作用力和力矩。由此建立了轴对称贮箱等效力学模型。加入干扰的动力学响应分析验证了模型的正确性和实际影响效果。     

Investigation of acceleration effects on missile aerodynamics using computational fluid dynamics

In this paper we describe the implementation and validation of arbitrarily moving reference frames in the block-structured CFD-code EURANUS. We also present results from calculations on two applications involving accelerating missiles with generic configurations. It is shown that acceleration affects wave drag significantly. Also, it is shown that strake-generated vortices move significantly in turns. These results clearly show the necessity of including the acceleration effects in the calculations.     

民用飞机燃油系统负加速度试飞技术研究

一个新型的民用飞机要投入航线使用,必须经过适航合格取证试飞,获得型号合格证、生产许可证和适航证,具备三证才允许走向市场。民用飞机适航取证试飞项目有许多,其中负加速度试飞是民用飞机燃油系统适航取证试验的重要验证项目。民用飞机负加速度试飞在国内尚属首次,具有对机组操纵技术要求高、风险难度大的特点。结合某型民机燃油系统合格审定试飞,研究了民用飞机负加速度的试飞技术,提出了用抛物线试飞方法来完成负加速度试飞任务。主要介绍了负加速度试飞中可能出现问题、试飞前应准备的工作、试飞方法等,并对试验结果进行了分析。     

加速度对晶体振荡器的影响及补偿技术研究

晶体振荡器作为基准频率源,在电子设备中发挥着重要作用。晶体振荡器对加速度具有敏感性,振动、冲击、离心力等作用均会导致其输出频率失稳。讨论了加速度影响晶体振荡器频率及相噪的机理,介绍了目前降低加速度效应的常用措施,并提出一种基于数字补偿系统的新方法。     

Coronal mass ejections acceleration problem

A statistical study of acceleration and its error of coronal mass ejections (CMEs) observed by the Large Angle Spectrometric Coronagraph (LASCO) is performed. A total of 5594 CMEs events have been analyzed by using a least-square method and using the error in the height measures. We verify that slower CMEs (velocities in the interval from 200 to 500 km s⁻¹) tend to have a positive acceleration (about 1 m s⁻²) at heights above 5 solar radii, while less than 10% CMEs show an average negative acceleration (about −2.2 m s⁻²) as they propagate from 5 to 30 solar radii. For most individual CMEs one can not say if they are accelerated or decelerated, only for 8% of all observed CMEs events one can extract the sign of the acceleration in the 5–30 solar radii.     

Observations of Extended Radio Emission in Clusters

We review observations of extended regions of radio emission in clusters; these include diffuse emission in ‘relics’, and the large central regions commonly referred to as ‘halos’. The spectral observations, as well as Faraday rotation measurements of background and cluster radio sources, provide the main evidence for large-scale intracluster magnetic fields and significant densities of relativistic electrons. Implications from these observations on acceleration mechanisms of these electrons are reviewed, including turbulent and shock acceleration, and also the origin of some of the electrons in collisions of relativistic protons by ambient protons in the (thermal) gas. Improved knowledge of non-thermal phenomena in clusters requires more extensive and detailed radio measurements; we briefly review prospects for future observations.     

Modeling and parameter identification of linear time-varying systems based on adaptive chirplet transform under random excitation

In this paper, a time–frequency algorithm based on adaptive chirplet transform for parameter modeling and identification of Linear Time-Varying (LTV) systems under random excitation is presented. It is assumed that the solution of responses of LTV structures is expressed as the sum of multicomponent Linear Frequency Modulated (LFM) signals in a short-time. Then the measured acceleration response is used to perform the adaptive chirplet transform, in which an integral algorithm is employed to reconstruct the velocity and displacement responses. The vibration differential equation with time-varying coefficients is transformed into a simple linear equation. Furthermore, for systems under random excitation, the input–output relation based on correlation function is also derived to estimate the parameters including physicals parameters and instantaneous modal parameters. The full procedure of the method is presented and validated by using simulated responses. The results show that the presented method is accurate and robust for various LTV systems under random excitation.     

Pierce振荡电路调谐特性分析及在飞行器频综加速度效应补偿中的应用

飞行器频综是整个飞行器中重要的组成部分,其性能的好坏直接决定系统的好坏。然而频综中的晶体振荡器对加速度具有敏感性,在受到振动、冲击等作用力的时候会导致其频率抖动和相位噪声恶化。为此,对基于变容二极管的pierce振荡电路的调谐特性进行了分析和仿真,并构建了测试平台,得到调谐系统的脉冲响应。实验结果表明,将基于变容二极管的电压调谐应用到实际补偿电路中,在100Hz以下的振动频率中,取得了较好的补偿效果。