Explore the vast range of titles available.

The variable stator vanes (VSV) are a set of typical spatial linkage mechanisms widely used in the variable cycle engine compressor. Various factors influence the angle adjustment precision of the VSV, leading to the failure of the mechanism. The reliability analysis of VSV is a complex task due to the involvement of multiple components, high dimensionality input and computational inefficiency. Considering the hierarchical characteristics of VSV structure, we propose a novel multi-layer Kriging surrogate (MLKG) for the reliability analysis of VSV. The MLKG combines multiple Kriging surrogate models arranged in a hierarchical structure. By breaking the problem down into more minor problems, MLKG works by presenting each small problem as a Kriging model and reducing the input dimension of the sub-layer Kriging model. In this way, the MLKG can capture the complex interactions between the inputs and outputs of the problem while maintaining a high degree of accuracy and efficiency. This study proves the error propagation process of MLKG. To evaluate MLKG’s accuracy, we test it on two typical high-dimensional non-linearity functions (Rosenbrock and Michalewicz function). We compared MLKG with some contemporary KG surrogate modeling techniques using mean squared error (MSE) and R square (${R^2}$). Results show that MLKG achieves an excellent level of accuracy for reliability analysis in high-dimensional problems with a small number of sample points.

The variable stator vane adjustment mechanism plays a vital role in preventing the occurrence of surge due to its complex multistage linkage mechanism. Initially, the flexible body is modeled using the absolute nodal coordinate formulation method, followed by the formulation of rigid–flexible coupled dynamics equations using the Lagrange equations of the first kind for the single‐stage variable stator vane adjustment mechanism. The constraint equations are defined, and the dynamics equations are solved using the coordinate chunking method. Numerical simulation is employed to evaluate the crank’s angular displacement and angular velocity, with validation conducted by comparing results with Simscape to ensure model accuracy. The study explores the motion behavior of the variable stator vane adjustment mechanism under various joint stiffnesses, loads, and driving modes. Results show minor errors between numerical and Simscape simulations, with discrepancies of around 1.01% for crank displacement and 1.65% for angular velocity. Comparing angular displacement curves between rigid–flexible and purely rigid models indicates similar trends. Lower joint stiffness complicates stabilizing the connecting link’s speed, while increased loads lead to more significant deformation and speed fluctuations. The study recommends avoiding uniform‐speed drive modes in favor of simpler harmonic or variable‐speed modes for the mechanism’s cylinder. Additionally, joint clearance significantly influences dynamics performance, potentially resulting in abrupt changes in collision force values and increased risks of joint wear and pitting.

The test rig can simulate real service conditions to obtain the friction and wear evolution of the bushing under high temperature and complex loading conditions, providing important experimental methods for material optimization, structural design improvements, and service life prediction of the bushing. The Variable Stator Vane (VSV) system is a critical component in aircraft engines, with its bushing providing structural support and lubrication. Under high temperatures, complex loads, and periodic motions, the bushing is prone to wear, which can affect system performance. In this study, a friction and wear test rig was designed to simulate realistic VSV bushing operating conditions. The rig is equipped with a programmable reciprocating drive, adjustable radial and bending moment loading, and a closed-loop temperature control system, allowing the wear process to be reproduced under high-temperature and complex loading conditions. Friction torque is measured using a torque sensor, while the equivalent wear volume is calculated from real-time data collected by two position sensors. Six samples were tested under 250 °C, 300 °C, and 350 °C, with bending moments of 1.5 Nm and 3 Nm, and a radial load of 30 KN, for 15,000 cycles. The results show that friction and wear evolve in two distinct stages: in the initial stage, friction torque and wear increase rapidly, followed by a slower growth rate during the stable stage. Higher temperatures and larger loads result in greater peak friction torque and more severe early wear. This study provides experimental methods to support VSV bushing material optimization, structural improvements, and lifetime prediction.

Future aero engine designs must address environmental challenges and meet noise and emissions regulations. To increase efficiency and reduce size, axial compressors require higher pressure ratios and a more compact design, leading to necessary modifications in the variable stator vanes, especially in the stator hub region. This study examines the impact of a variable cantilevered stator on the performance and aerodynamics of a 1.5-stage transonic compressor, representative of a high-pressure compressor front stage. Experimental tests at the transonic compressor test rig at Technical University of Darmstadt involved two variable stators with identical airfoil designs but different hub configurations, using the same inlet guide vane and rotor. Detailed aerodynamic analysis was conducted using steady and unsteady instrumentation. The cantilevered stator achieved a 2% increase in efficiency and a 1% increase in total pressure ratio, due to higher aerodynamic loading and reduced pressure losses. The primary performance gain comes from the reduction of the hub blockage area. The cantilevered stator also performed well at near stall conditions, unlike the shrouded stator. Time-resolved measurements indicated that loss mechanisms are closely linked to the rotor wake phase. Overall, variable cantilevered stators outperformed shrouded stators in this compressor stage.

To meet the demanding performance requirements of next-generation aero engines especially high maneuverability and extended endurance, adaptive cycle engines (ACE) with three-stream bypass have attracted significant research interest. These engines offer superior operational flexibility through variable geometry and multi-mode adjustment. A key component, the front and rear fan system, must provide an enhanced flow adjustment range for the rear fan and improved throughflow capacity at high Mach numbers. This study investigates a variable tandem stator configuration as a means to address these challenges. Using numerical simulations, we analyze the effect of tandem stator load split (LS) on fan performance. Results indicate that reducing the LS improves both mass flow rate and efficiency: it lowers flow deviation angles and positive pre-swirl at the rear fan inlet, thereby increasing mass flow rate in both front and rear fans and alleviating front surge and rear blockage. While reverse stator adjustment further increases mass flow rate, it also reduces efficiency due to heightened negative pre-swirl and increased reaction degree. During forward adjustment, fans with different LS values exhibit identical stall point mass flow rates, limiting the forward adjustment range for larger LS values. At a lower LS (0.2), the total and internal bypass mass flow rate adjustment ranges exceed 15% and 22%, respectively, significantly greater than those at higher LS (0.6). Moreover, a smaller LS consistently delivers better efficiency across all adjustment angles. Based on these findings, a multi-condition optimization framework is proposed to identify optimal operational parameters under various flight scenarios. This work provides valuable insights into wide-range flow control and variable-condition performance optimization for ACE compression systems.

The six-phase motor control system has low torque ripple, low harmonic content, and high reliability; therefore, it is suitable for electric vehicles, aerospace, and other applications requiring high power output and reliability. This study presents a superior sensorless control system for a six-phase permanent magnet synchronous motor (PMSM). The mathematical model of a PMSM in a stationary coordinate system is presented. The information of motor speed and position is obtained by using a sliding mode observer (SMO). As torque ripple and harmonic components affect the back electromotive force (BEMF) estimated value through the traditional SMO, the function of the frequency-variable tracker of the stator current (FVTSC) is used instead of the traditional switching function. By improving the SMO method, the BEMF is estimated independently, and its precision is maintained under startup or variable-speed states. In order to improve the estimation accuracy and resistance ability of the observer, the rotor position error was taken as the disturbance term, and the third-order extended state observer (ESO) was constructed to estimate the rotational speed and rotor position through the motor mechanical motion equation. Finally, the effectiveness of the method is verified by simulation and experiment results. The proposed control strategy can effectively improve the dynamic and static performance of PMSM.

The operating characteristics of the gas turbine are described beginning with the basic thermodynamic cycle and developing typical stage temperatures and pressure throughout the gas path of the engine. The performance characteristics of the primary elements of the engine including compressor, combustor, turbine and exhaust nozzle are developed using non‐dimensional variable techniques. The concept of compressor stall is explained together with the design techniques used to improve engine controllability during transients including interstage bleeds and variable stator vanes. Finally the principle of afterburning is described including a typical arrangement of fuel manifold and flame holders within the exhaust nozzle.

This study introduces stator currents‐based model reference adaptive system (MRAS) estimators that employ variable structured control (VSC) in the adaptation mechanism to enable the online estimation of stator resistance and permanent magnet (PM) flux in interior permanent magnet synchronous motors (IPMSMs). These MRAS estimators estimate stator resistance and PM flux by analysing the error between the stator currents measured as the reference model and the stator currents generated by the adaptive model. The performance of the proposed estimators is assessed through simulation studies. Furthermore, the proposed approach is compared to a conventional MRAS employing a fixed‐gain proportional‐integral (PI) controller. Simulation results and error analyses indicate that the VSC‐based MRAS algorithms outperform traditional PI‐based MRAS in terms of accuracy and reliability. Additionally, the proposed method eliminates the reliance on a fixed‐gain PI controller, a common component in conventional MRAS systems.

In this study, a new model-based fault detection and isolation (FDI) strategy is proposed for field-oriented control (FOC) induction motor (IM) drives. Actuator faults are addressed, and specifically, single open-circuit faults are considered in this study. The residual signals are synthesised by taking the resulting closed-loop dynamics when a FOC strategy is applied, that is, the residuals are referenced to the synchronous reference frame (dqe-coordinates), which are generated by using a bank of variable structure observers to obtain a robust FDI scheme. Thus, subsystems sensitive to a specific fault, but decoupled from other faults are obtained in a natural way, where only two stator currents and the mechanical position are required for fault isolation purposes. Residual evaluation is carried out in the stator reference frame (dq-coordinates) for the IM model, where the residual direction (angle) is employed to isolate a fault in each one of the six power switches in a voltage source inverter. In addition, the observer FDI scheme can be combined with a fault re-configuration strategy in order to improve the reliability of the motor drive. Experimental results are illustrated for a three-phase 3/4 HP IM drive at different reference frequencies and load torques with single open-circuit faults that verify the ideas presented in this work.

The dynamic response of a rotor system can be significantly affected by uncertainties. It is essential to understand and quantify the influence of uncertain parameters on the rotor response. The purpose of this study is to evaluate the effect of perturbation in critical system parameters on the dynamic behaviour of a flexible rotor with localised contact. A test rig consisting of a localised contact element is developed. The critical rotor speeds are identified using the Campbell diagram, internal resonance diagram and experimental run-up analysis. Modal interactions influence the critical rotor speed. Modal interactions can be controlled using system parameters such as contact location, eccentric mass location and contact friction. Experimentally the sensitivity of the system parameters on the dynamic response is analysed. A stochastic finite element model is developed for the rotor–stator system using uncertain critical system parameters. The generalized Polynomial Chaos expansion (gPC) is used to evaluate the stochastic response of the finite element model with uncertainties. The approach uses a numerical collocation method for determining the coefficients of the gPC. The modal interaction is altered by varying the contact location, impulsive load location and the rotor–stator interface friction. The results from the experimental and numerical study indicate that the dynamic response at internal resonance rotor speed is more sensitive to the perturbation in system parameters compared to the critical speed corresponding to the first whirling mode.