航空发动机承力结构隔振设计方法及试验

基于先进航空发动机承力框架的结构与力学特征,通过理论分析与仿真计算验证了高隔振性承力框架结构动力学设计方法。通过对承力结构刚度/质量分布及几何构形突变的优化设计,提高转子支承结构在宽频域内的机械阻抗,实现在转子工作转速范围内的高隔振性。根据承力结构刚度/质量分布对隔振性的影响,采用折返式非连续结构,设计并搭建了转子-承力框架试验系统,通过试验进一步验证了高隔振性承力框架设计方法。试验结果表明:在承力结构中采用非连续性设计可在宽频域内对不同位置支点处激励具有良好的隔振效果。

半主动空气悬架的整车仿真分析及优化

为研究空气弹簧在半主动悬架中的突出优势以及空气弹簧的优化策略,文章基于某成熟车型的整车动力学模型,首先建立天棚阻尼控制策略的阻尼控制算法,再搭建相应的空气弹簧模型;其次,根据空气弹簧的特性进行不同载荷状态下的空气弹簧基准刚度设计,并结合悬架隔振性能和悬架冲击性能对空气弹簧刚度进行优化;最后,通过与基础被动悬架车型的仿真结果对比,验证了优化方案的有效性。结果表明,半载和满载状态下,悬架隔振性能在鹅卵石路面提升分别约19.78%和28.92%,在比利时路面提升分别约15.12%和21.52%,悬架冲击性能提升分别约54.55%和60%。该研究方法与空气弹簧的工程开发和应用较为贴合,可有效降低空气弹簧的开发周期及成本。

基于能量优化的混合馈能悬架阻尼优化设计

为了回收悬架的振动能量,提出了一种弹簧-减振器-直线电机并联的混合式悬架结构。针对直线电机馈能过程存在的死区现象,设计了DC/DC升压电路,以传统被动悬架耗散的能量为基准,得到了同一行驶工况下馈能效率的显式表达,同时,为兼顾系统动力学性能,研究了减振器阻尼对馈能性能和隔振性能的影响规律,并通过折中设计确定了减振器最优阻尼系数,建立了混合馈能悬架动力学模型,进行了其隔振性能和馈能性能的对比仿真分析。结果表明,混合馈能悬架可有效协调车辆馈能性和隔振性。最后,在仿真的基础上,进行了混合馈能悬架的试验研究,试验结果与仿真结果基本吻合,验证了仿真结果的正确性。

Experimental research on static characteristics of special wire-rope isolator

Based on analysis of the work conditions and structural characteristics of the exterior pipeline of the aero-engine, a kind of cantilever-structure wire-rope isolator fitted to the exterior pipeline of the aero-engine is designed for supporting and damping purposes. By static experiments, the static hysteresis loop, the relationship of stiffness and amplitude, and the relationship between the energy dissipation coefficient and the amplitude are obtained. Analyses show that the wire-rope isolator presents obvious hysteresis characteristics, and the characteristics of the isolator, such as stiffness and damping, behave obviously nonlinearly when the amplitude value of deformation changes. At the same time, by changing the structure parameters of the wire-rope, the wirerope isolators can be made with different functions to satisfy different work conditions. The research results have important reference values for the application of the wire-rope isolator on the exterior pipeline of an aeroengine.

Effects of friction variability on isolation performance of rolling-spring systems

By taking a rolling-spring isolation system as the study object, the effects of the non-uniform distribution of rolling friction coefficient on its isolation performance were analyzed by a compiled computer program. The results show that the errors associated with the structural maximum relative displacement, acceleration and residual displacement due to ignoring the friction variability sequentially grow. This rule is weakened by the spring action, however, the unreasonable spring constant will cause sympathetic vibration. Under the condition of large friction variability, in the calculation of the structural maximum relative displacement and acceleration, the friction variability should be considered. When the structural residual displacement is concerned, the variability of rolling friction coefficient should be fully considered regardless of the friction variability.

The Influence of Blocking Mass Parameters on the Vibration Isolation Performance of a Power Cabin

Rigid blocking masses are located in the typical base structure of a power cabin based on the impedance mismatch principle.By combining the acoustic-structural coupling method and statistical energy analysis,the full-band vibration and sound radiation reduction effect of vibration isolation masses located in a base structure was researched.The influence of the blocking mass’ cross-section size and shape parameters and the layout location of the base isolation performance was discussed.Furthermore,the effectiveness of rigid vibration isolation design of the base structure was validated.The results show that the medium and high frequency vibration and sound radiation of a power cabin are effectively reduced by a blocking mass.Concerning weight increment and section requirement,suitably increasing the blocking mass size and section height and reducing section width can result in an efficiency-cost ratio.

Ride quality evaluation of the soil compactor cab supplemented by auxiliary hydraulic mounts via simulation and experiment

In order to evaluate the ride quality of the soil compactor cab supplemented by the auxiliary hydraulic mounts (AHM), a nonlinear dynamic model of the soil compactor interacting with the off-road deformable terrain is established based on Matlab/Simulink sofware. The power spectral density (PSD) and the weighted root mean square (RMS) of acceleration responses of the vertical driver s seat, the cab s pitch and roll angle are chosen as objective functions in low-frequency range. Experimental investigation is also used to verify the accuracy of the model. The influence of the damping coefficients of the AHM on the cab s ride quality is analyzed, and damping coefficients are then optimized via a genetic algorithm program. The research results show that the cab s rubber mounts added by the AHM clearly improve the ride quality under various operating conditions. Particularly, with the optimal damping coefficients of the front-end mounts c a 1,2 = 1 500 N · s/m and of the rear-end mounts c a 3,4 =2 335 N · s/m, the weighted RMS values of the driver s seat, the cab s pitch and roll angle are reduced by 22.2%, 18.8%, 58.7%, respectively. Under the condition of the vehicle travelling, with the optimal damping coefficients of c a 1,2 = 1 500 N · s/m and c a 3,4 =1 882 N · s/m, the maximum PSD values of the driver s seat, the cab s pitch and roll angle are clearly decreased by 36.7%, 54.7% and 50.6% under the condition of the vehicle working.

Optimization Design of Vibration Characteristics of Ship Composite Brace with Rigid Vibration Isolation Mass

In considering the theory of structural dynamic optimization design, a design method of the structural style of ship composite brace with rigid vibration isolation mass was studied. Two kinds of structural dynamic optimization formulations minimizing the vibration acceleration of the non-pressure hull on the restraining condition of the gross weight of the ship cabin were established: 1) dynamic optimization of the sectional dimensions of the rigid vibration isolation mass in the composite brace; 2) dynamic optimization of the arranging position of the rigid vibration isolation mass. Through the optimization results, sectional dimensions and the arranging position of the rigid vibration isolation mass with better performance in reducing vibration were gained, and some reference was provided for practical engineering designs as well as enrichment of the design method of a novel ship vibration-isolation brace.

浅述内燃机用环保静密封材料

介绍了内燃机用环保静密封材料的物理结构、制造方法及密封机理。客观地阐述了环保静密封材料的应用价值。

Study on the Impediment to Vibration Wave Propagation from Rigid Vibration Isolation Mass

Based on the principle of impedance mismatching,the performance of rigid vibration isolation mass in impeding vibration wave propagation was discussed from the perspective of wave approach.Based on FEM,the influence of its weight as well as the cross-section shape parameters on the isolation performance of rigid vibration isolation mass was studied through numerical simulation.The results show that rigid vibration isolation mass can effectively impede the propagation of the medium and high frequency vibration waves,and the heavier the vibration isolation mass,the better the isolation performance.For low frequency waves,the vibration isolation effect is not so obvious;for a rectangular vibration isolation mass,the isolation performance could be effectively improved by increasing the cross-section height and reducing the cross-section width.A useful reference was provided for the application of rigid vibration isolation masses to the vibration isolation and noise reduction of ship structure.

Vibration transmissibility characteristics of smart spring vibration isolation system

The objective of this work was to study the vibration transmissibility characteristics of the undamped and damped smart spring systems. The frequency response characteristics of them were analyzed by using the equivalent linearization technique, and the possible types of the system motion were distinguished by using the starting and ending frequencies. The influences of system parameters on the vibration transmissibility characteristics were discussed. The following conclusions may be drawn from the analysis results. The undamped smart spring system may simultaneously have one starting frequency and one ending frequency or only have one starting frequency, and the damped system may simultaneously have two starting frequencies and one ending frequency. There is an optimal control parameter to make the peak value of the vibration transmissibility curve of the system be minimum. When the mass ratio is far away from the stiffness ratio, the vibration transmissibility is small. The effect of the damping ratio on the system vibration transmissibility is significant while the control parameter is less than its optimal value. But the influence of the relative damping ratio on the vibration transmissibility is small.

Low-frequency ride comfort of vibratory rollers equipped with cab hydro-pneumatic mounts

Based on the advantages of hydraulic and pneumatic mounts,a new hydro-pneumatic mount(HPM)is proposed to improve the low-frequency ride comfort of vibration rollers.Through the experiment of the vibratory roller,a nonlinear vehicle dynamic model working on off-road soil grounds is then established to assess the HPM's ride comfort in the low-frequency region.Two indices,the power spectral density(PSD)acceleration and root mean square(RMS)acceleration of the operator vibration and cab shaking,are chosen as objective functions in both the frequency and time regions.The research results show that when the cab isolations are equipped with the HPM,the RMS values of the operator's seat,cab's pitch and roll angles are reduced by 35%,42%and 53%;and the maximum PSD of the operator's seat,cab's pitch and roll angles are decreased by 39%,59%and 65%,respectively.Consequently,the characteristics of the nonlinear damper and high-static stiffness of HPM can greatly reduce the operator vibration and cab shaking in the low-frequency region when compared to the vibratory roller's cab using the rubber mounts.

Contrast enhanced MR angiography in pulmonary sequestration

Objective To evaluate the feasibility of contrast enhanced three-dimensional(3D)magnetic resonance angiography(MRA)in identifying the systemic blood supply in pulmonary sequestration.Methods Three patients who were suspected of pulmonary sequestration were examined by contrast enhanced 3D MRA.MR images were compared with surgical findings.Results Contrast enhanced 3D MRA clearly demonstrated systemic arteries from the descending thoracic aorta supplying the basilar segments of the lower lobe in each case.Pulmonary veins from these segments,which drained into the left atrium in two cases,were also detected.MRA images were consistent with those observed in surgery.Conclusion Contrast enhanced 3D MRA allows accurate diagnosis of pulmonary sequestration and may obviate the need for more invasive investigations.