This study proposes a new near zero-wear non-contact self-impact seal based on the passive fluid blocking principle and Tesla valve structure, which is characterised by zero-wear, long lifetime, simple structure high stability. Research shows that impact-blocking effect of three-dimensional leakage channel can realise stepwise throttling sealing medium. Furthermore, pressure, number stages spacing significantly affect leakage. Leakage be effectively controlled increasing series reducing...

Due to their distinct advantages and great potential, quadrotor UAV has attracted more attentions. The ability avoid obstacles automatically is the essential criterion of intellectualization UAV. In order decouple dynamic system realize desired flight, backstepping technique employed in this paper, which performance terms transient steady response. On basis, paper also proposes two kinds obstacle avoidance approaches, Safety-ball model Mass point model. process avoidance, stable flight...

The influences of groove bottom texture, in the form orientation structure with various width, depth, spacing, and different operation parameters, on effect have been investigated by numerical analysis. results show that existence texture change direction strong impacts effect, opening force leakage increase due to effect. increment is more remarkable when film thickness small shaft speed or medium pressure high. makes performance dry gas seal stable, which significant for extreme working...

Accurate prediction of the self-propulsion performance is one most important factors for energy-efficient design a ship. In general, hydrodynamic full-scale ship could be achieved by model-scale simulation or towing tank test with extrapolations. With development CFD methods and computing power, directly predict an approach. this article, numerical study on propeller operating behind at model- presented. The includes simulations using RANS method double-model VOF model respectively scale...

Abstract. The multi-body dynamics simulation model of the hybrid system with a flexible shaft was established through rationally simplifying structure parallel system, assembling shaft, pulley, piston assembly , rod and rotor according to actual constraints, adding appropriate connections. engine cylinder pressure reconstruction motor vector control were in MATLAB as shafting incentives. analysis dynamic characteristics carried out boost mode system. results show that: torsional vibration...

For a class of discrete-time multi-variable systems with time-varying parametric uncertainty, the parameter identification method and switching control architecture are developed in this study to implement smooth control. Specifically, algorithm based on least geometric mean squares is derived for system. In addition, system, model reference technique as basis design each local model, proposed achieve satisfactory performance, especially eliminate oscillations at boundaries which can be...

The parameter design of main components hydrauLic excavator, mostly based on the specific structure system, has bad universaLity. In order to find a method that is versatile and simple calculation process, it figured out different kinds hybrid power system have same path in transfer energy. distribution energy decided by upper Limit direct from diesel engine. engine, which could characterize used as independent variable. common expressions components' installed are deduced load curve. These...

At present, more and applications of Unmanned Aerial Vehicles (UAV) makes the control UAV to be a hot pot in doing research. In controlling UAV, traditional PID controller's parameters are not easily chose anti-interference ability system is poor. Aiming improve it, paper designs GPFN-PID controller based on GPFN neural network. The has functions online training, self-training self-adjusting, which longitudinal channel effective. simulation results show that both dynamic characteristics lot.

The characteristics of high speed, pressure, microscale, and rotating flow fields result in very complicated between the dynamic static rings a dry gas seal. In particular, existence groove, dam, weir further contribute to uncertainty microscale field. Classically, regime pipe is determined based on critical Reynolds number (Pipe model) while field sometimes by factor (Oval model). this study, new method was developed that can be used for prediction seal three-dimensional velocity component...

Multi-model technique is studied and adopted for the control design longitudinal dynamics of fixed-wing unmanned aerial vehicle (UAV) in paper. A linear model set built up at a number operating points which are characterized by different values flight velocity altitude, since aerodynamics greatly influenced two states, corresponding controller linearized models constructed, including discrete-time quadratic regulator (DLQR) as inner loop pitch angle PID altitude tracking keeping. The...

For a class of unstable discrete-time multi-variable switched systems with parametric uncertainty, an identification scheme is developed in this paper. Specifically, the algorithm derived to identify parameter vectors potential subsystems based on idea least geometric mean squares. Furthermore, neural network classifier put forward for partition identified subsystems. Finally, feasibility and effectiveness proposed are verified by numerical simulations, which show that desirable performance...

摘要: 针对高转速下液膜密封空化区界面发生强烈波动导致密封失稳的问题,为寻找波动抑制方法,考察了微流道槽底面剪切条件对液膜空化流场特性的影响。选用Schnerr-Sauer空化模型,运用Laminar和转捩SST模型,对比研究了不同转速槽底面无滑移和无剪切条件下的开启力Fo、泄漏率Q、空化占比和空化区速度分布规律。结果表明:流动模型的选择(Laminar和转捩SST模型)对Fo和Q的影响可以忽略,但对空化影响十分显著;液膜空化泡在膜厚方向呈不规则曲面状,在槽区膜厚中部位置的轴截面空化面积占比最大,无滑移时向非开槽端面单侧减小,无剪切时向密封端面双侧减小;可分开判定非槽区和槽区流态,非槽区始终为层流,槽区在11 300 r/min以下为层流,高于11 r/min为转捩流,若存在局部区域流动因子9/16<ζ<1或有空化发生,均应采用转捩SST模型;槽底面进行超滑水改性,可显著提高Fo(15 000 r/min时提高51.6%),降低Q(1 r/min时降低2.8%),有效降低空化率(15 r/min时空化体积占比降低超过80%),提升空化临界转速(从4 r/min提升至7...

Numerical analysis is employed to investigate the influence of parting surface and combined thermal factor (rotation) on deformation split mechanical seal. Parting takes little effect temperature distribution, verified by comparison experiment. Shaft rotation speed does not much affect radial gradient seal end faces but can raise when being increased. The simulated model turns a drum, with surfaces, close primary sealing interface presenting convergent taper, becoming open-shaped. Increasing...

For longitudinal dynamics of Fixed-wing Unmanned Aerial Vehicle (UAV) with strong disturbance and parameter uncertainty, a new High Performance L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> Adaptive Control (HPL AC) method is proposed in this paper. HPL AC based on combination Ackermann Pole Assignment Controller (APAC) adaptive controller, where APAC utilized to stabilize the closed-loop system controller adopted guarantee control...

optimal estimation of the attitude, an attitude solution system based on low-cost IMU sensors is proposed. The uses quadratic coordinate conversion to fuse gyroscope, accelerometer, and magnetic compass data, deviation corrected by PI controller, information vehicle solved a complementary filtering algorithm. experimental results show that proposed algorithm not only effectively improves accuracy meet flight requirements small UAV, but also suppresses influence random sensor noise three-axis...

Abstract The concept of “super-slip design” is used to investigate the influence multiple factors on opening and frictional forces a tribo-pair with microscale grooves. results demonstrate that significantly improving load-carrying capacity reducing viscous friction can be simultaneously realised by super-slip modification bottom surface hydrodynamic groove as result joint action surface, geometrical parameters, operating conditions. This expected further enhance reduce applying shear stress...