双毛细管法高温气态环己烷黏度测量研究

为了探索双毛细管法在碳氢燃料高温气态黏度测量中的应用,本文采用双毛细管法测量了亚临界压力下环己烷的高温气态黏度。测量温度范围：301.9 K-567.1 K（间隔约10K）;压力范围：0.5MPa-4.0MPa（间隔1.0 MPa）。考虑螺旋管圈的二次流效应,使用基于雷诺数（Re）或迪恩数（De）的函数关系式对黏度测量结果进行离心修正。在测量参数条件下,气态环己烷的雷诺数Re ≤ 1984.5。研究表明：双毛细管法测量环己烷液态和气态黏度时,螺旋管圈的二次流效应具有显著差别;液态环己烷的离心修正系数小于 4.32%,气态环己烷的离心修正系数最高达到 49%;离心力二次流效应是影响环己烷气态黏度测量精度的最重要因素;离心修正关系式的准确度对环己烷气态黏度测量结果的不确定度产生显著影响。     

一种用于深空测距的数字化锁相环设计

在深空测距中,扩大锁相环捕获范围与提高锁相环对微弱信号检测能力是一对矛盾。为解决这一矛盾,本文提出一种基于频率引导与二次混频的数字化锁相环结构,并对其性能进行理论分析和计算机仿真。仿真结果表明,该锁相环可以很好地在较大范围内实现对微弱测距信号的捕获锁定。该结构已在实际测距接收机中使用。     

微织构刀具对钛合金切屑形成影响的仿真研究

针对微织构刀具对钛合金Ti6Al4V切屑形成以及微槽二次切削机理分析的不足，通过建立热-力耦合仿真模型对比研究不同微织构刀具、微织构几何尺寸以及切削速度对切屑形成的影响规律。数值仿真结果表明：微织构刀具更有利于断屑，二次切削作用使切屑的弯曲半径变大，微织构可以减小刀屑之间实际接触面积，降低切削温度。增大微织构宽度可以增强微槽的二次切削作用，利于断屑，但应注意其对刀具强度的削弱作用，而增大相邻微槽间距则会出现相反的二次切削作用机制。提高切削速度对各刀具均有利于断屑，弧形微织构刀具的降温效果最好，V形微织构刀具次之，矩形微织构刀具降温效果最差。研究结果对进一步理解微织构刀具对钛合金切屑的二次切削作用机理提供一定参考。     

Simulation of the secondary air system of turbofan engines: Insights from 1D-3D modeling

Focusing on the internal flow and heat transfer analysis, a platform for the performance evaluation of the Secondary Air System (SAS) is developed. A multi-fidelity modeling technique has been developed in a turbofan engine model under different flight conditions. A turbine blade cooling model which integrates external heat transfer calculations and coolant side modeling with common components is proposed. In addition, the Computational Fluid Dynamics (CFD) method is selected to capture the complex flow field structure in the preswirl system. The validity of the SAS models is compared with publicly available data. An elaborately designed cooling system for the AGTF30 engine is analyzed through three main branches. It is found that the 1D-3D modeling technique can provide more accurate predictions of the SAS for the AGTF30 engine. The results demonstrate the versatility and flexibility of the SAS models, thereby indicating the capacity of meeting most of the demands of flow and thermal analysis of the SAS.