Current Issue : October-December Volume : 2022 Issue Number : 4 Articles : 5 Articles
As technology continues to leap forward and innovations advance, the systems of civil aircraft are becoming increasingly sophisticated and complex. Accordingly, there is a rising amount of information to be processed by pilots in the cockpit, increasing their cognitive burden, which significantly threatens the safety of flight. Thus, designers have formulated cockpit layout principles relating to importance, frequency of use, functional grouping, and operation sequence on the basis of ergonomics, which can effectively reduce the cognitive burden for pilots. The degree to which the cockpit layout of a model conforms to the four design principles can indicate its ergonomic design level. In accordance with the concepts of the above four cockpit layout principles, evaluation methods for determining their respective conformity to the four design principles were proposed in this paper. These methods use the operational sequence of cockpit system controls used in the normal flight mission of the actual aircraft type as the evaluation data source. Subsequently, the total evaluation results for cockpit layout were obtained using the weighted accumulation method. Lastly, the process for evaluating the cockpit layouts of civil aircraft was illustrated using the cockpits of the A320 series and B737NG series as examples. Based on the final evaluation results, the feasibility and effectiveness of the proposed evaluation method was verified....
In this study, the performance of a vortex array gripper was numerically investigated based on the pressure distribution on the surface of a gripped object and the resulting suction force. An analysis of the suction force generated by a single-vortex gripper was performed to determine the geometric parameters for providing a good suction force and subsequently, for the vortex array gripper configuration. Array grippers consisting of two- and four-vortex grippers were studied. For dual-vortex grippers, the generated suction forces of various inlet air configurations with different vortex gripper distances are illustrated. The pros and cons of all types of air supply and the influence of positive pressure formed by outlet airflow interaction were examined. The analysis of quad-vortex grippers also revealed that the suction force could be increased by reducing the outlet flow interaction between the grippers using the placement of exhaust vents. Thus, the installation of array grippers can be arranged in a more compact form to increase the total suction force per unit operation area with uniformity....
The orbital operation of spacecraft can excite the long-drawn and low-frequency vibration of the solar array, which is prone to affecting the task execution of the system. To address this issue, an envelope-based variable-gain control strategy is proposed to suppress vibration of the solar array using the reaction wheel (RW) actuator. The RW actuator is individually mounted on the solar array to provide reaction torque through the speed change of its rotor. The governing equation of motion of the solar array actuated by a RW actuator is deduced with the state space representation. The control relation between the measured bending moment and the rotational speed of the RW actuator with the constant-gain coefficient is firstly developed and demonstrated in numerical simulation. Changing the gain coefficient to be inversely proportional to the envelope function of vibration, a variable-gain control strategy is proposed to improve the damping effect of the RW actuator. Simulation results show that the vibration suppression performance of the RW actuator is improved compared to the constant-gain control. As the actual on-orbit natural frequency of the solar array is not always exactly known, the robustness of the control system is analyzed for the deviation between the estimated and the actual natural frequency values. The proposed variable-gain control is also experimentally verified using a simplified elastic plate model. Experimental results indicate that the vibration attenuation time is decreased to 29.1% and 50.22% compared to the uncontrolled and the constant-gain controlled states, respectively....
Erosive wear due to the fact of sand severely affects hydrocarbon production industries and, consequently, various sectors of the mineral processing industry. In this study, the effect of the elbow geometrical configuration on the erosive wear of carbon steel for silt–water–air flow conditions were investigated using material loss analysis, surface roughness analysis, and microscopic imaging technique. Experiments were performed under the plug flow conditions in a closed flow loop at standard atmospheric pressure. Water and air plug flow and the disperse phase was silt (silica sand) with a 2.5 wt % concentration, and a silt grain size of 70 μm was used for performing the tests. The experimental analysis showed that silt impact increases material disintegration up to 1.8 times with a change in the elbow configuration from 60◦ to 90◦ in plug flow conditions. The primary erosive wear mechanisms of the internal elbow surface were sliding, cutting, and pit propagation. The maximum silt particle impaction was located at the outer curvature in the 50◦ position in 60◦ elbows and the 80◦ position in 90◦ elbows in plug flow. The erosion rate decreased from 10.23 to 5.67 mm/year with a change in the elbow angle from 90◦ to 60◦. Moreover, the microhardness on the Vickers scale increased from 168 to 199 in the 90◦ elbow and from 168 to 184 in the 60◦ elbow....
Due to environmental pressure and the prevailing political and economic situation in the world, alternatives to traditional fossil fuels are being sought. The use of bio-derived fuels may reduce the emission of pollutants present in jet engine exhausts. The presented research investigates the possibility of replacing the conventional fuel, which is kerosene, with plant-derived fuels from marine algae and jatropha. During the analysis, based on the available data, the emission indices of pollutants were computed, and then, for the adopted aircraft and route, the emissions for kerosene and alternative fuels were determined. A significant reduction in the emission of most analyzed compounds (even by 40% for CO) was achieved compared to the emission for kerosene. The obtained results are discussed in the conclusion section....
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