Cyclone multiphase flow in the annular space is widely used in fluid machinery, such as burner and pneumatic conveying. However, the annular flow field is complex, and the related research is not sufficient. To improve the safety and efficiency of equipment, this paper proposes a method for detecting the motion state of swirling fluid in annular space by integrating computational fluid dynamics (CFD) and electrical capacitance tomography (ECT), calculates the motion characteristics of swirling multiphase flow in the annular space using the CFD, and visually measures the distribution and motion state of swirling multiphase flow in the annular space using the ECT. Numerical simulation and experimental results show that the results of the two methods are in good agreement, indicating that the model selected in this paper in the CFD is correct. The CFD effectively reveals the distribution of swirling multiphase flow in the annular pipe, and the ECT can accurately reconstruct the position and size of swirling multiphase flow in the annular space. The combination of these two methods provides a new idea for the study of multiphase flow in annular space.
In the rocket recovery environment, the imaging conditions are complicated, and the vision equipment is prone to problems such as ground target information loss, image contrast and saturation reduction, color deviation and so on, which directly affect the solution of the rocket pose. Therefore, it is necessary to study the de-fog algorithm for the special environment of rocket recovery, so as to contribute to the solution of rocket pose and altitude measurement. Through the investigation of previous research on de-fogging algorithms, it can be found that the dark channel de-fogging algorithm is not only simple in principle but also has better de-fogging effect in changeable environment. In addition, the brightness of fog in rocket recovery is often affected by the flame emitted from the nozzle, and a single dark channel de-fogging algorithm cannot adjust the overall brightness according to the environmental characteristics, resulting in blurred feature points in the image after de-fogging. Therefore, considering that RETINEX theory can be used to adjust the brightness of images, in combination with the dark channel prior model, this paper mainly uses RETINEX theory to improve the dark channel de-fogging theory to process the transmission t(x), so that the final image retains the feature information to the maximum extent, and improves the adaptability of the dark channel de-fogging algorithm to different fog environments. Finally, the removal effect of different de-fogging algorithms on different concentrations of fog in rocket recovery environment is quantitatively analyzed. The experimental results show that the de-fogging algorithm in this paper can solve the impact of the fog generated by the rocket nozzle on the vision equipment.
In order to meet the design requirements of more compact and portable laser detection system, the parameters optimization design of lightweight structure is carried out for the receiving system with large quality proportion. Firstly, based on the index requirements of the system for performance and structure, the scheme of Cassegrain optical receiving system is selected, and it is clear that the receiving system is an all-aluminum card mechanical structure. Then, through the numerical analysis of the mode and static force of the receiving lens, the main reflector is selected as the optimization object. After that then the multi wheel topology optimization design is carried out by using the finite element analysis method, and the dynamic simulation analysis of the whole receiving system is carried out. Finally, it is determined that the lightweight hole form of the back opening of the main reflector is fan-shaped, the thickness is 4mm, and the weight loss rate is 31.4%. Under certain vibration and impact environment conditions, the system structure still has good stability. According to the design and optimization results, the processing and assembly of the lens are completed. Through alignment test and surface inspection, the PV value of the main reflector is 2.293λ, and the RMS is 0.509λ (λ=1064nm). Both of them meet the requirements of optical design. It shows that the accuracy of the main reflector surface improved by top1ology optimization can meet the application requirements. which has a certain reference significance for the structural design in the field of aircraft laser ranging.
In view of the problem that the imaging quality of the large-aperture and long-focal length infrared optical system is sensitive to temperature changes. In this paper, we propose an idea of combining athermalization design with catadioptric optical system, and a large-aperture long-focal length catadioptric infrared optical system is designed by this idea. According to the influence of each parameter by environmental changes, the system optical power is allocated reasonably. Select the appropriate infrared lens material and reflector base material for the system so that the image plane deviation caused by the environmental changes of the components cancel each other out. The design method and idea proposed in this paper have important reference value for the realization of heat dissipation of catadioptric optical system. The working band of the system is 8~14μⅿ,the focal length is 250ⅿⅿ, F-number is 1, and the three infrared materials used in the system are HWS2, HWS9 and IRG22. The design results show that the system can maintain high imaging quality in the temperature range of -40°C~+60°C, with the modulation transfer function (MTF) curves close to the diffraction limit at the cutoff frequency. The design methods and ideas proposed in this paper have significant reference value for realizing athermalization of catadioptric optical systems.
The structure of the initial system is calculated according to the aberration theory, in which the radius of the primary mirror is 300 mm, the radius of the secondary mirror is 320 mm, the distance between the primary mirror and the secondary mirror is 90 mm, and the blocking ratio is close to 0.4, and the occlusion ratio is close to 0.4. A three-piece correction lens set is designed to solve the spherical aberration and comet aberration caused by the Cassegrain system in the large field of view, and the imaging of the edge field of view of the large field of view system is realized. Through the optimization and layout of the overall system, the MTF value of the system is finally greater than 0.4 within the frequency of 130 lp/mm. This paper provides important reference value for the design of catadioptric optical system with large aperture and large field of view.
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