Effect of the Wet Outlet Geometry on the Shockwave Position in Supersonic Separators

Supersonic separators (3Ss) are applied in gas separation processes. Two-dimensional simulation is employed to investigate the effect of operational and thermophysical parameters on the shockwave position. In addition, the impact of the cyclonic part and wet outlet geometry is evaluated by proposing four cases. Increasing the length of the cyclonic part exerts positive and negative influences on the performance of the 3S and the pressure recovery coefficient, respectively. The optimum length is determined between 10 and 15 cm. To demonstrate negative effects of wasted air from the wet outlet, its flow has been increased from 3.6 to 8.1 % of the inlet flow. Improved performance of the 3S is obtained by reducing the flow disturbances around the wet outlet and moving the shockwave towards the outlet.     

A novel intelligent approach for yaw position forecasting in wind energy systems

Yaw control systems orientate the rotor of a wind turbine into the wind direction, optimize the wind power generated by wind turbines and alleviate the mechanical stresses on a wind turbine. Regarding the advantages of yaw control systems, a k-nearest neighbor classifier (k-NN) has been developed in order to forecast the yaw position parameter at 10-min intervals in this study. Air temperature, atmosphere pressure, wind direction, wind speed, rotor speed and wind power parameters are used in 2, 3, 4, 5 and 6-dimensional input spaces. The forecasting model using Manhattan distance metric for k = 3 uncovered the most accurate performance for atmosphere pressure, wind direction, wind speed and rotor speed inputs. However, the forecasting model using Euclidean distance metric for k = 1 brought out the most inconsistent results for atmosphere pressure and wind speed inputs. As a result of multi-tupled analyses, many feasible inferences were achieved for yaw position control systems. In addition, the yaw position forecasting model developed was compared with the persistence model and it surpassed the persistence model significantly in terms of the improvement percent.     

A simplified method for optimal design of solar water heating systems based on life-cycle energy analysis

Significant energy mismatch exists in solar water heating systems as the time and amount of solar energy supply are usually different from that of hot water demand. Using a hot water storage tank can reduce or eliminate such mismatch in short term while it is difficult to avoid this mismatch in long term. In many optimal design and life-cycle analysis methods, the energy mismatch is ignored which causes the system performance to be overestimated and also misleads the optimal design of the system. This paper presents a simplified method for optimizing the key parameters of solar water heating systems based on life-cycle energy analysis. This optimal method considering the energy mismatch phenomenon can be implemented through two steps. In the first step, a simplified energy model based hourly energy matching different components of the system, is developed for determining the operating performance of system with different solar collector areas and water storage volumes. In the second step, the law of diminishing marginal utility is employed to determine the optimum size of the system. The optimum size is identified when the maximal life-cycle net energy saving is achieved. A case study on the application of the proposed method in a building is presented as well.     

On oscillation reduction in feedback control for processes with an uncertain dead time and internal–external disturbances

This paper aims to find a practical solution to reduce oscillation on the Smith Predictor (SP) based design with the dead time (DT) uncertainty, making it less sensitive to DT change and more effective in disturbance rejection. First, a conditional feedback mechanism is introduced in SP to reduce the amount of oscillation caused by the model inaccuracies in the DT parameter. Then, to address the oscillation caused by the phase lag in traditional PI controller and uncertain dynamics, this conditional SP is combined with active disturbance rejection control (ADRC), assisted by the knowledge of process dynamics. A practical tuning method is provided for the practicing engineers. The proposed approach is validated in extensive simulation studies with different types of plants and in frequency domain analysis. The simulation results show significant improvements in performance robustness and transient response.     

基于非线性干扰观测器的自动弹仓终端滑模控制

针对某自动弹仓位置控制过程中的负载变化和不确定性干扰，设计了基于干扰观测器和非奇异快速终端滑模的复合控制策略，建立了自动弹仓的不确定性动力学模型。干扰观测器用于估计系统复合干扰，估计值用于补偿滑模控制器以增强控制器的鲁棒性和抗干扰能力。运用Lyapunov准则证明了系统闭环稳定。所提算法和PID算法的对比实验结果显示，设计的控制律实现了自动弹仓位置的精确控制，具有良好的鲁棒性，有效提高了自动弹仓的定位稳定性。     

基于多自由度气动机械手位置伺服系统稳定性控制研究

基于传统易碎薄板机械手位置伺服控制系统稳定性低、自动化分拣效率低等不足,设计了一种基于笛卡尔坐标式的气动码垛机器手和位置伺服稳定性控制系统。首先,设计并介绍笛卡尔坐标式码垛机械手的基本组成结构,对机械手末端吸盘气动回路控制系统进行设计和分析;然后分别对机械手X、Y、Z三个方向的伺服电机控制原理进行分析并设计了一种位置伺服系统的前馈自适应控制算法;最后,将传统位置闭环PID算法和前馈自适应控制算法进行位置跟踪稳定性对比试验。实验结果表明该笛卡尔坐标式的气动码垛机器手和位置伺服稳定性控制系统设计合理,满足实际生产要求。     

Experimental study on the propagation characteristics of hydrogen/methane/air premixed flames in a narrow channel

This work is focused on the explosion characteristics of premixed gas containing different volume fractions of hydrogen in a narrow channel (1000 mm × 50 mm × 10 mm) under the circumstance of stoichiometric ratio. The ignition positions were set in the closed end and the middle of the pipeline respectively. The results showed that when the gas was ignited at the pipeline closed end, the propagating flame was tulip structure for different premixed gas. When the hydrogen volume fraction was less than 40%, the flame propagation speed increased significantly with the rise of hydrogen volume fraction, and the overpressure peak also appeared obviously in advance. However, when the volume fraction of hydrogen was more than 40%, the increase of flame propagation speed and the overpressure peak occurrence time varied slightly. Furthermore, when the ignition position was placed in the middle of the pipeline, the flame propagation speed propagating to the opening end was much faster than that propagating to the closing end, and there was no tulip shape when the flame propagates to the opening end. The flame propagating to the closed end appeared tulip shape under the influence of airflow, and high-frequency flame oscillation occurred during the propagation. This work shows that the hydrogen volume fraction and ignition position significantly affected the flame structure, flame front speed, and explosion overpressure.     

Tunable electrocaloric and energy storage behavior in the Ce,Mn hybrid doped BaTiO3 ceramics

The electrocaloric effect and energy storage property are tuned in the Ba_1-xCe_xTi_0.99Mn_0.01O₃ ceramics prepared by the solid state reaction method. The ceramics with lower Ce content (x?=?0.005, 0.015) show a better ΔT and ΔT/ΔE response. The ceramics with higher Ce content (x?=?0.030, 0.040, 0.045) represent the broader ΔT peaks (50?K–60?K), and the higher energy storage density and efficiency. The largest electrocaloric response (ΔT_max?=?1.22?K, ΔT/ΔE?=?0.41?K mm/kV) is found in the Ba_0.995Ce_0.005Ti_0.99Mn_0.01O₃ ceramics, which is comparable or even higher than that of the most isovalent substituting BaTiO₃-based ceramics reported before. The maximum energy storage density 0.11?J/cm³ (E?=?30?kV/cm) is obtained for the Ba_0.970Ce_0.030Ti_0.99Mn_0.01O₃ ceramics, with high efficiency of 65–88% over a wide temperature range of 72?K. This work may open more opportunities to design high electrocalaric and energy storage performance lead-free systems from the viewpoint of the heterovalent and size mismatch substitution.     

操作窗口对排风柜污染物控制效果影响的实验研究

为提升排风柜的控污能力,在排风柜性能测试实验台上,采用示踪气体测试法和正交试验法,研究了操作窗口竖直开度、水平开度、面风速和操作窗口位置对排风柜前呼吸区污染物控制效果的影响。极差分析和方差分析结果表明:各因素对呼吸区污染物控制效果影响的强弱顺序依次为竖直开度、水平开度、面风速、操作窗口位置;操作窗口水平开度、竖直开度增大,排风柜对呼吸区的污染物控制效果减弱;面风速增大,控制效果增强;水平开度与竖直开度对控制浓度的影响存在较大的相关性,这2个因素对控制浓度的影响仅在另一因素达到一定水平后才能体现。     

提高冶炼低硅含钛铁水转炉废钢比工艺攻关

废钢比是转炉生产的重要经济技术指标,其值大小直接影响转炉冶炼钢铁料消耗及热平衡,提高入炉废钢比是实现节铁增钢、降本增效的重要技术手段。然因冶炼低硅含钛铁水成渣难、脱磷难等问题,对应入炉废钢比持低不高,直接影响转炉生产成本。为此,基于低硅含钛铁水冶炼特点及难点分析,结合水钢生产实践,通过氧枪喷头优化、枪位优化、添加提温剂等工艺优化和技术开发,使入炉废钢比由优化前7.41%提高至13.48%,优化效果较为明显,为实现节铁增钢、降本增效奠定了一定基础。