A laser-based machine vision measurement system for laser forming

Laser forming continues to be a promising technology in manufacturing due to its fast speed, flexibility, and low-cost. Measurement of deformation after laser forming is widely needed to verify its convergence to the intended shape in academic research. With the development of laser forming, high requirements on the measurement of the deformed work-piece have been sought such as a 3D profile of the deformed surface, a large measuring range, and measuring convenience. In this paper, a laser-based machine vision measurement system was developed to measure the 3D profile of deformed surface by a one-off scanning process. Based on the 3D profile data, the vertical displacement of the deformed plate was calculated for bending analysis. In addition, as one of the important feature parameters, transverse shrinkage was automatically determined through a novel image-based method during the scanning process. A measuring accuracy of 0.03 mm for vertical displacement measurement and 0.0125 mm for transverse shrinkage were achieved in the developed measurement system. This measurement performance is acceptable in most of the laser forming processes currently studied.     

Experimental studies on the effects of bearing supply gas pressure on the response of a permanent magnet disk-type motor rotor

Vibrations, particularly low-frequency vibrations caused by self-excited gas films, significantly affect the safety and economy of turbomachinery, which becomes dangerous at high rotational speeds. This experimental study focuses on the dynamic characteristics of a Permanent magnet (PM) disk-type motor rotor supported by gas aerostatic bearings. Nonlinear dynamic behavior, including double low frequency and gas film half whirling, was analyzed in the experiments. The dynamic features of double low frequency and gas whirling are described in the paper. The most important finding is that the sum of the whirling ratios of low frequencies 1 and 2 is always 1.00. The occurrence mechanism requires further study. The effects of bearing supply gas pressure on the dynamic response characteristics of the multi-disk PM rotor are implemented to improve rotor stability.     

电场对竖直微槽润湿及毛细流动特性影响

竖直微槽群毛细结构广泛应用在重力热管、蒸发器等散热设备内,但受重力等因素影响易达到毛细极限。引入电场的主动强化方式来提高竖直微槽的毛细极限,并通过实验和建立数学模型研究电场对竖直微槽内液体润湿及毛细流动特性的影响。结果表明,电场可以提高竖直微槽内液体润湿高度,当电场为5.0 kV时与无电场时相比,润湿高度强化比可达到30.0%。同时,电场作用下流体在微槽道内的毛细润湿流动呈分段效应：润湿流动初期,润湿高度与时间的1/2次方呈线性关系,即h-t^1/2,润湿速率与润湿高度的倒数呈线性关系,即v-1/h;润湿流动中后期,润湿高度与时间的1/3次方呈线性关系,即h-t^1/3,润湿速率与润湿高度平方的倒数呈线性关系,即v-1/h²,且润湿速率随时间呈下降趋势。     

Assessment of CO2 capture options from various points in steam methane reforming for hydrogen production

Steam methane reforming (SMR) is currently the main hydrogen production process in industry, but it has high emissions of CO₂, at almost 7 kg CO₂/kg H₂ on average, and is responsible for about 3% of global industrial sector CO₂ emissions. Here, the results are reported of an investigation of the effect of steam-to-carbon ratio (S/C) on CO₂ capture criteria from various locations in the process, i.e. synthesis gas stream (location 1), pressure swing adsorber (PSA) tail gas (location 2), and furnace flue gases (location 3). The CO₂ capture criteria considered in this study are CO₂ partial pressure, CO₂ concentration, and CO₂ mass ratio compared to the final exhaust stream, which is furnace flue gases. The CO₂ capture number (N_cc) is proposed as measure of capture favourability, defined as the product of the three above capture criteria. A weighting of unity is used for each criterion. The best S/C ratio, in terms of providing better capture option, is determined. CO₂ removal from synthesis gas after the shift unit is found to be the best location for CO₂ capture due to its high partial pressure of CO₂. However, furnace flue gases, containing almost 50% of the CO₂ in produced in the process, are of great significance environmentally. Consequently, the effects of oxygen enrichment of the furnace feed are investigated, and it is found that this measure improves the CO₂ capture conditions for lower S/C ratios. Consequently, for an S/C ratio of 2.5, CO₂ capture from a flue gas stream is competitive with two other locations provided higher weighting factors are considered for the full presence of CO₂ in the flue gases stream. Considering carbon removal from flue gases, the ratio of hydrogen production rate and N_cc increases with rising reformer temperature.     

Experimental investigation of energy consumption and environmental impact of adaptive defrost in domestic refrigerators

With the development of human modern society at the turn of the new century, more and more people tend to use new technologies. To keep in tandem with modern technologies, food storage became easier with domestic refrigerators. In such systems, frost formation can be a fundamental problem especially in tropical countries with hot and humid ambient conditions. An adaptive method for defrosting the evaporator of a domestic refrigerator system is presented in this paper. In this method, parameters namely open door time, compressor ON time, previous defrost duration, mode of compressor, fans, and heater action before, during, and after defrost have been considered effective on defrost operation. Experiments have been carried out on two different case study top mounted freezers. Experimental results for case study 1 showed that the adaptive defrost in comparison to the fixed defrost cycles could reduce the energy consumption and Total Equivalent Warming Impact (TEWI) about 13% and 12.5%, respectively. The same parameters for case study 2 were decreased 5.5% and 5.2%, respectively. Furthermore, temperature variation of the compartments for both case studies decreased in comparison to that of their corresponding base case, which prevents quality loss of the stored food during defrost. Briefly, the results showed lower energy consumption, more environmentally friendly effects, and lower compartment temperature change.     

Life cycle assessment of stand-alone photovoltaic (SAPV) system under on-field conditions of New Delhi,India

In this paper, life cycle analysis has been carried out to evaluate overall performance of given rated stand-alone solar photovoltaic (SAPV) in terms of basic energy matrices, life cycle cost analysis, and earned carbon credit. Further, the experimentally calculated actual on-field life cycle performance results of existing outdoor SAPV system (i.e. almost 20 years old) have been represented with respect to the potential (max.) performance of same SAPV system estimated under same environmental conditions of solar intensity, ambient temperature, PV operating temperature as obtained during actual on-field performance evaluation. This new approach of overall performance evaluation by considering the on-field SAPV system installation as new (i.e. with potential/max. performance) and old (i.e. with actual performance) under same environmental conditions provides an inclusive comparative life cycle assessment of on-field PV system.     

Experimental investigation on a parabolic trough solar collector for thermal power generation

Developing solar thermal power technology in an effective manner is a great challenge in China.In this paper an experiment platform of a parabolic trough solar collector system(PTCS) was developed for thermal power generation,and the performance of the PTCS was experimentally investigated with synthetic oil as the circulate heat transfer fluid(HTF).The solar collector's efficiency with the variation of the solar flux and the flow rate of the HTF was identified.The collector efficiency of the PTCS can be in ...     

Experimental investigations on liquid flow and heat transfer in rectangular microchannel with longitudinal vortex generators

The behaviors of improved Heat transfer and the associated higher pressure drop for liquid flow in rectangular micochannels with longitudinal vortex generators (LVGs) were determined experimentally for the Reynolds numbers of 170–1200 with hydraulic diameter of 187.5 μm and aspect ratio of 0.067 for LVGs with different number of pairs and angles of attack. It was found that the range of critical Reynolds numbers (600–730) were at a much smaller value by adding LVGs than the one without (Re ～ 2300); heat transfer performance was improved (9–21% higher for those with laminar flow and 39–90% for those with turbulent flow), while encountering larger pressure drop (34–83% for laminar flow and 61–169% for turbulent flow). Empirical correlations for these two parameters were then obtained by curve-fittings for a variety of rectangular microchannels under study.