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Axial force is one of the important factors affecting the life and reliability of centrifugal pumps. Based on the SST turbulence model, the unsteady internal flow field of an aero fuel centrifugal pump under various working conditions was analyzed by using the finite volume method and the axial force of the impeller component was predicted. The position servo force measuring system was used to measure the axial force of the fuel centrifugal pump and the theoretical formula of axial force was modified according to the numerical results and experimental values. The study shows that the pressure distribution of the front and rear pump chambers presented uneven circumferential distribution under the influence of dynamic and static interference through numerical simulation. The simulated head number is basically consistent with the test result and the maximum error of the axial force value obtained by the numerical calculation and the experimental value was 9.7% under different speeds, which verified the accuracy of the numerical simulation. Furthermore, the modified formula can accurately calculate the axial force of the fuel centrifugal pump with an error of less than 9.88%. The results of the study provide a theoretical basis for the calculation and balance of axial force in an aero aero fuel centrifugal pump. [ABSTRACT FROM AUTHOR]

In order to ensure that aircraft have medium and long-range flights, enhanced aerodynamic performance, and reduced fuel consumption, this paper presents an original Distributed Hybrid Electric Propulsion Aircraft (DHEPA) design scheme and proposes a novel power allocation management method based on convex optimization. Firstly, by taking the Tecnam P2006T general-purpose aircraft as a reference, key components of DHEPA are selected and modeled. Then, a power allocation management method for DHEPA is proposed on the basis of convex optimization, which takes the minimum fuel consumption as the performance index to realize the reasonable power allocation of the battery and engine, while avoiding sliding into the local optimum of allocation. Finally, momentum theory and numerical simulation methods are used to analyze the aerodynamic enhancement effect of the propeller on the wing in the DHEPA, and a dynamics method is utilized to calculate the dynamics performance of the aircraft at several important stages. The results show that, compared with the reference aircraft, the lift of the DHEPA is increased by 46%. Under typical sectors, the DHEPA has a higher rate of climb and maximum leveling off speed at cruise, and a significantly lower fuel consumption. [ABSTRACT FROM AUTHOR]

A full envelope LMI-based multi-region linear parameter-varying power controller is designed for a turbofan engine in this paper. According to the characteristics of aero-engine model, three scheduling variables are divided into two groups firstly, and then part of them are partitioned, rather than all scheduling variables are partitioned directly as the usual multi-region LPV control. The polynomial LPV model of aero-engine is established under a specific flight condition. An explicit LPV controller by gridding method based on parameter-dependent Lyapunov function is designed and we propose a method to eliminate the dependence of LPV controller on the derivative of scheduling parameter. The flight envelope of turbofan engine is divided into multiple sub-regions, and a mixing LPV control method with overlapping regions is proposed, which can guarantee stability and performance across the full envelope. Finally, the simulation results on the nonlinear component level model of a twin-spool turbofan engine verify our method. [ABSTRACT FROM AUTHOR]

This study evaluated the effect of intrauterine perfusion of autologous platelet-rich plasma (PRP) on pregnancy outcomes in women with recurrent implantation failure (RIF). Key biomedical databases were searched to identify relevant clinical trials and observational studies. Outcomes included clinical pregnancy rate, chemical pregnancy rate, implantation rate, live birth rate, and abortion rate. Data was extracted from ten studies (six randomised controlled trials, four cohort studies) involving 1555 patients. Pregnancy outcomes were improved in women treated with PRP compared to controls: clinical pregnancy rate (RR = 1.96, 95% CI [1.67, 2.31], p < 0.00001, I2 = 46%), chemical pregnancy rate (RR = 1.79, 95% CI [1.54, 2.08], p < 0.00001, I2 = 29%), implantation rate (RR = 1.90, CI [1.50, 2.41], p < 0.00001, I2 = 0%), live birth rate (RR = 2.83, CI [1.45, 5.52], p = 0.0007, I2 = 83%), abortion rate (RR = 0.40, 95% CI [0.18, 0.90], p = 0.03, I2 = 59%). These data imply PRP has potential to improve pregnancy outcomes in women with RIF, suggesting a promising role in assisted reproductive technology. What is already known on this subject? Platelet-rich plasma (PRP) is an autologous blood product that contains platelets, various growth factors, and cytokines at concentrations above the normal baseline level. Recent studies have shown that intrauterine infusion of autologous PRP can improve pregnancy outcomes in infertile women. What do the results of this study add? This systematic review and meta-analysis of data from ten studies (n = 1555; 775 cases and 780 controls) investigated the effect of intrauterine perfusion of autologous PRP on pregnancy outcomes in women with recurrent implantation failure (RIF). Findings suggest that pregnancy outcomes, including clinical pregnancy rate, chemical pregnancy rate, implantation rate, live birth rate and abortion rate were improved in women treated with PRP compared to controls. What are the implications of these findings for clinical practice and/or further research? RIF remains a challenge for researchers, clinicians, and patients. Our study identified PRP as a potential intervention in assisted reproduction. As an autologous blood preparation, PRP eliminates the risk of an immune response and transmission of disease. PRP is low cost and effective and may represent a new approach to the treatment of patients with RIF. [ABSTRACT FROM AUTHOR]

In order to solve the problem of motor fault caused by extreme low temperature and vibration in the high altitude of aviation propulsion motor, using the intelligent sliding mode fault-tolerant control, a speed controller based on variable exponential power reaching law and an extended sliding mode disturbance observer is designed; furthermore, the parameters are optimized by the adaptive chaotic gray wolf optimization algorithm. In addition, a second-order nonsingular terminal sliding mode observer and a frequency adaptive complex coefficient filter are designed. First, variable exponential power reaching law is helpful to eliminate the speed tracking error and buffeting for the speed controller, the external disturbance can be estimated and compensated using the extended sliding mode disturbance observer, and adaptive chaotic gray wolf optimization algorithm can enhance the accuracy of parameters. Second, for the sake of making the aviation propulsion motor run smoothly in the case of speed sensor fault, second-order nonsingular terminal sliding mode observer is designed to estimate the speed and position of aviation propulsion motor, and adaptive complex coefficient filter is designed to improve the estimation accuracy. Finally, based on MATLAB/Simulink simulation and STM32 motor series experiments, the effectiveness of the proposed observer and controller algorithm is verified. [ABSTRACT FROM AUTHOR]

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Aiming at the various nonlinear factors, external disturbance in electro-hydraulic servo position systems, a novel sliding mode tracking control method based on the variable exponential power is proposed, which not only improves the speed of reaching the sliding mode surface, but also ensures the smooth approach performance as much as possible: the chattering phenomenon of the sliding surface is reduced effectively as a result. Furthermore, in order to optimize the parameters of the sliding mode controller, a new optimization algorithm is proposed by combining Grey Wolf optimizer with particle swarm optimization (CGWO-PSO), skillfully. The primary advantages of the new CGWO-PSO algorithm include faster convergence speed and higher performance. Finally, the co-simulation platform for the electro-hydraulic servo position system is built. The results of co-simulation show that the sliding mode tracking control method proposed in this paper can realize that the electro-hydraulic position servo system has excellent tracking accuracy, strong robustness, and smooth approach performance. [ABSTRACT FROM AUTHOR]