The combustion processes of homogeneous charge compression ignition (HCCI) engines whose piston surfaces have been coated with catalyst (rhodium or platinum) were numerically investigated. A singlezone model and a...The combustion processes of homogeneous charge compression ignition (HCCI) engines whose piston surfaces have been coated with catalyst (rhodium or platinum) were numerically investigated. A singlezone model and a multi-zone model were developed. The effects of catalytic combustion on the ignition timing of the HCCI engine were analyzed through the single-zone model. The results showed that the ignition timing of the HCCI engine was advanced by the catalysis. The effects of catalytic combustion on HC, CO and NOx emissions of the HCCI engine were analyzed through the multi-zone model. The results showed that the emissions of HC and CO (using platinum (Pt) as catalyst) were decreased, while the emissions of NOx were elevated by catalytic combustion. Compared with catalyst Pt, the HC emissions were lower with catalyst rhodium (Rh) on the piston surface, but the emissions of NOx and CO were higher.展开更多
In order to adapt to the changing battlefield situation and improve the combat effectiveness of air combat,the problem of air battle allocation based on Bayesian optimization algorithm(BOA)is studied.First,we discuss ...In order to adapt to the changing battlefield situation and improve the combat effectiveness of air combat,the problem of air battle allocation based on Bayesian optimization algorithm(BOA)is studied.First,we discuss the number of fighters on both sides,and apply cluster analysis to divide our fighter into the same number of groups as the enemy.On this basis,we sort each of our fighters'different advantages to the enemy fighters,and obtain a series of target allocation schemes for enemy attacks by first in first serviced criteria.Finally,the maximum advantage function is used as the target,and the BOA is used to optimize the model.The simulation results show that the established model has certain decision-making ability,and the BOA can converge to the global optimal solution at a faster speed,which can effectively solve the air combat task assignment problem.展开更多
Flow and heat transfer of a novel turbine shroud with throttle chamber under two kinds of orifice arrangements were numerically studied. The original shroud model composed of the impingement holes, film holes and jet ...Flow and heat transfer of a novel turbine shroud with throttle chamber under two kinds of orifice arrangements were numerically studied. The original shroud model composed of the impingement holes, film holes and jet channel. The two modified models have identical geometrical spacing except for the number and location of the orifices in the upper plate of the throttle chamber added in the jet channel. Different pressure values were set at the outlets of different row film holes simulating the mainstream favorable pressure gradient. The ratios of inlet total pressures of impingement holes to outlet static pressures of the third row film holes ranged from 1.6 to 3.6. The Nusselt number distributions were validated by the experimental data. The main target of this study was to quantify the impact of the throttle chamber on the flow regulation and internal heat transfer characteristics. The flow factor, relative mass flow rate, the Nusselt number and the heat transfer factors on the target walls were presented. It is found that the mass flow rate distributions in the film hole rows become more reasonable by the modification of location and number of the orifices on the throttle chamber. The throttle chamber decreases the heat transfer on the target walls.展开更多
Fiber-reinforced resin-based plastics are widely used in structural composites for aerospace and automotive applications,and they often face extreme load conditions in actual working environments.It is challenging to ...Fiber-reinforced resin-based plastics are widely used in structural composites for aerospace and automotive applications,and they often face extreme load conditions in actual working environments.It is challenging to monitor the damage of the structure during the vibration process.This study was aimed at using buckypaper(BP)sensors to monitor the structural health status of composite structures under ambient vibrations.First,the feasibility of flexible printed circuit instead of wire is verified by the tensile experiment.Then the vibration monitoring experiment of the composite cantilever beam is carried out by using BP sensors systematically.The sweep frequency experiment determines the excitation frequency of the cantilever beam.Low-period vibration fatigue cycle and high-period vibration fatigue cycle experiments are designed to verify the vibration monitoring method using BP sensors.Besides,the signal response of BP sensors in the vibration experiment is analyzed,and the relationship betweenΔR/R0 and vibration acceleration is obtained.Finally,through the change law ofΔR/R0 of the sensor,the cumulative damage caused by vibration fatigue is visualized.It is demonstrated that the monitoring method based on BP sensors can be applied to study the damage behavior of composite structure under the vibration environment.展开更多
基金the National Key Basic Research Development Project of China (2001CB209201)
文摘The combustion processes of homogeneous charge compression ignition (HCCI) engines whose piston surfaces have been coated with catalyst (rhodium or platinum) were numerically investigated. A singlezone model and a multi-zone model were developed. The effects of catalytic combustion on the ignition timing of the HCCI engine were analyzed through the single-zone model. The results showed that the ignition timing of the HCCI engine was advanced by the catalysis. The effects of catalytic combustion on HC, CO and NOx emissions of the HCCI engine were analyzed through the multi-zone model. The results showed that the emissions of HC and CO (using platinum (Pt) as catalyst) were decreased, while the emissions of NOx were elevated by catalytic combustion. Compared with catalyst Pt, the HC emissions were lower with catalyst rhodium (Rh) on the piston surface, but the emissions of NOx and CO were higher.
基金the National Natural Science Foundation of China(No.61074090)。
文摘In order to adapt to the changing battlefield situation and improve the combat effectiveness of air combat,the problem of air battle allocation based on Bayesian optimization algorithm(BOA)is studied.First,we discuss the number of fighters on both sides,and apply cluster analysis to divide our fighter into the same number of groups as the enemy.On this basis,we sort each of our fighters'different advantages to the enemy fighters,and obtain a series of target allocation schemes for enemy attacks by first in first serviced criteria.Finally,the maximum advantage function is used as the target,and the BOA is used to optimize the model.The simulation results show that the established model has certain decision-making ability,and the BOA can converge to the global optimal solution at a faster speed,which can effectively solve the air combat task assignment problem.
基金supported by the National Natural Science Foundation of China(Grant No.51406124)by the Educational Department of Liaoning Province(Grant No.JYT19062)。
文摘Flow and heat transfer of a novel turbine shroud with throttle chamber under two kinds of orifice arrangements were numerically studied. The original shroud model composed of the impingement holes, film holes and jet channel. The two modified models have identical geometrical spacing except for the number and location of the orifices in the upper plate of the throttle chamber added in the jet channel. Different pressure values were set at the outlets of different row film holes simulating the mainstream favorable pressure gradient. The ratios of inlet total pressures of impingement holes to outlet static pressures of the third row film holes ranged from 1.6 to 3.6. The Nusselt number distributions were validated by the experimental data. The main target of this study was to quantify the impact of the throttle chamber on the flow regulation and internal heat transfer characteristics. The flow factor, relative mass flow rate, the Nusselt number and the heat transfer factors on the target walls were presented. It is found that the mass flow rate distributions in the film hole rows become more reasonable by the modification of location and number of the orifices on the throttle chamber. The throttle chamber decreases the heat transfer on the target walls.
基金This work was supported by the National Natural Science Foundation of China[11902204]Natural Science Foundation of Liaoning Province[2020-MS-236,2019010256-JH3/301]+1 种基金Shenyang Youth Technological Innovation Talent Project[RC200030,RC190004]Aeronautical Science Foundation[201903054001].
文摘Fiber-reinforced resin-based plastics are widely used in structural composites for aerospace and automotive applications,and they often face extreme load conditions in actual working environments.It is challenging to monitor the damage of the structure during the vibration process.This study was aimed at using buckypaper(BP)sensors to monitor the structural health status of composite structures under ambient vibrations.First,the feasibility of flexible printed circuit instead of wire is verified by the tensile experiment.Then the vibration monitoring experiment of the composite cantilever beam is carried out by using BP sensors systematically.The sweep frequency experiment determines the excitation frequency of the cantilever beam.Low-period vibration fatigue cycle and high-period vibration fatigue cycle experiments are designed to verify the vibration monitoring method using BP sensors.Besides,the signal response of BP sensors in the vibration experiment is analyzed,and the relationship betweenΔR/R0 and vibration acceleration is obtained.Finally,through the change law ofΔR/R0 of the sensor,the cumulative damage caused by vibration fatigue is visualized.It is demonstrated that the monitoring method based on BP sensors can be applied to study the damage behavior of composite structure under the vibration environment.