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Abstract
To improve aircraft assembly efficiency and personnel utilization, a multi-objective and multi-constrained model of the type-E aircraft pulsating assembly line balancing problem was constructed according to the characteristics of aircraft pulsating assembly line, and a hybrid algorithm which combined Non-dominated Sorting Genetic Algorithm (NSGA), cuckoo search algorithm and dynamic search algorithm was designed to solve the problem. The dynamic search algorithm solved the low efficiency and poor quality of the solution to type-E assembly line balancing problem; the NSGA raised the optimization effect of assembly sequence by improving the individual distance calculation method; the cuckoo search algorithm improved Lévy flight distance calculation equation to search the optimal station number. The algorithm was proved to be senior to that in the related research, and the validity of the model was verified by the application example.
... To ensure the smooth progress of the heating metering reform, developing a reliable and precise heat meter with low pressure loss and its corresponding detecting equipment has become the key [3]. At present, the research and development of the ultrasonic heat meter mainly focus on the circuit module of the totalizer that collects the ultrasonic signals. ...
Objective: To increase heat calculation accuracy, the numerical simulation of the ultrasonic heat meter is explored by multiphysics coupling. Methods: The COMSOL, a multiphysics coupling finite-element simulation software, is used to build the coupling model of the sound field, structure field, and electric field. The propagation of ultrasonic waves in heat meters is simulated, and its sound field distribution in pure water is analyzed. According to the operating conditions of ultrasonic heat meters, the influence of impurities with different concentrations on ultrasonic propagation is analyzed. The end-face sound pressure levels of the incident transducer and the receiving transducer are compared to obtain the attenuation laws of ultrasonic waves in the liquid-solid two-phase flow. Results: The main lobe and multiple side lobes exist during the propagation of ultrasonic waves. The energy of the main lobe is higher than that of the side lobes. Bubbles resonate under the action of the sound field. Also, bubbles of different diameters correspond to different resonance frequencies, which have larger sound pressure than that of the incident sound field. Most of the sound waves are reflected at the liquid-solid interface, while some of them continue to propagate through the media, affecting the sound pressure distribution on the end-face of the receiving transducer, thereby affecting the measurement accuracy of the ultrasonic heat meter. Conclusion: The reliability and detection efficiency of the heat meter is improved, which is significant and theoretically valuable.
... At first, some scholars found that diesel / natural gas dual fuel engine consumes less fuel and has higher efficiency. Therefore, on this basis, some scholars analyzed the influence of different natural gas injection pressures on the pressure, heat release rate, ignition delay time and emissions of Diesel / natural gas dual fuel engine [3]. It is found that under low load condition, delayed injection of natural gas can realize stratified mixing of air fuel in different cylinders [4]. ...
In order to study a new clean and efficient combustion mode, which can relieve the pressure of traditional energy and ensure low emissions, in this study, a diesel/natural gas dual fuel engine is designed by non-dominant sorting genetic algorithm (NSGA-Ⅱ), and its thermodynamic characteristics are studied. The WP10.290 Diesel engine is modified into a diesel/natural gas dual fuel engine. The emissions of harmful substances and thermal efficiency of the modified engine under different working conditions are compared. The combustion chamber structure and adaptability between combustion chamber and injection parameters are optimized by using NSGA-II algorithm and CFD software. The results show that the emission of NOx and CH4 and the fuel consumption rate can be reduced simultaneously by using the composite combustion model compared with the original engine. When the CH4 emission is close to zero, the fuel consumption rate decreases obviously, and NOx slightly increases. When the angle between the injection holes is 141.57° the amount of NOx in the cylinder is large. When the injection advance angle is 21.91°CA, the pressure in the cylinder is the highest, the CH4 production is the lowest, the NOx production is higher, and the oxygen content in the combustion mixture is less. The NOx production is the lowest. diesel/natural gas dual fuel engine can ensure efficient combustion while reducing emissions. In this study, the performance of the dual fuel engine at various speeds can be further studied, which can provide theoretical support for the design of diesel/natural gas dual fuel engine.
... In aircraft manufacturing, the assembly has great impact on the production cost, which is estimated to account for almost 30% of the total cost [1,2]. To reduce the manufacturing cost, many aviation companies have introduced the pulse final assembly line for its high efficiency [3]. The aircraft pulse final assembly line is composed of several different assembly stations which are made up of dozens of jobs. ...
In order to develop equipment adapted to the aircraft pulse final assembly line, a vision-based aircraft transport platform system is developed. This article explores a guiding method between assembly stations which is low-cost and easy to change routes by using two-dimensional code and two complementary metal oxide semiconductor (CMOS) cameras. The two cameras installed on the front and back of the platform read the two-dimensional code containing station information to guide the platform. In the process of guiding, the theoretical position and posture of the platform at each assembly station are known, but there is a difference between the actual and theoretical values due to motion errors. To reduce the influence of the deviation on the navigation route, a localization method is proposed based on the two-dimensional images captured by the cameras. Canny edge detection is applied to the processed image to obtain the position of the two-dimensional code in the image, which can measure the angle/distance deviation of the platform. Then, the computer can locate the platform precisely by the information in the two-dimensional code and the deviation measured by the image. To verify the feasibility of the proposed method, experiments have been performed on the developed platform system. The results show that the distance and angle errors of the platform are within ±10 mm and ±0.15° respectively.
With the continuous upgrading of the manufacturing system, the assembly line balancing problem (ALBP) is gradually complicated, and the researches are constantly deepened in the application theory and solution methods. In order to clarify the research direction and development status of assembly line balancing, 89 articles are read and studied. We classify ALBPs to construct the network structure of research from horizontal classification and vertical thinking. The ALBP framework is horizontally given according to the number of models (i.e. the number of products), the layout shape of the assembly line, and the data of task time. The “seven steps for scientific paper” is vertically proposed according to the research steps to comb the research path of scientific and technological literature. The horizontal and vertical extension crosses and constructs the network structure of the ALBP. Any horizontal problem intersects with any step of the vertical “seven steps for scientific paper” to form a research point. We analyze 89 articles according to the development path from the straight line to U-shaped line and then to two-sided U-shaped/parallel U-shaped assembly line, summarize the research algorithm of assembly line balance and count the number of articles, and point out the latest research direction and algorithm development trend of assembly line balance.
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