The operational demands of a wide range significantly exacerbate combustion instability issues within ramjet combustor.To suppress combustion oscillations,an open-loop control system utilizing Linear Genetic Programmi...The operational demands of a wide range significantly exacerbate combustion instability issues within ramjet combustor.To suppress combustion oscillations,an open-loop control system utilizing Linear Genetic Programming(LGP)has been developed for a full-scale annular ramjet combustor.The LGP is used to generate control laws that include multi-frequency forcing.These laws are then transformed into square waves to actuate the solenoid valve,which modulates the kerosene supply for open-loop control.The results show that the duty cycle has little effect on instability amplitude,whereas an increase in frequency leads to a remarked reduction in combustion amplitude.After five generations evolvements,the pressure amplitude is reduced by 40.6% under the optimal control law generated by LGP.Furthermore,the machine learning process is depicted using a proximity map of control law similarity,with the search pathway visualized by the steepest descent.All individuals go forward to the upper left corner of the map with the evolution process,terminating at the optimal individual of the fifth generation.展开更多
The existence of absolute parametric instability in an inhomogeneous plasma is revisited in a one-dimensional three-wave model.Non-resonant daughter waves are considered to match the conditions of radio-frequency(RF)-...The existence of absolute parametric instability in an inhomogeneous plasma is revisited in a one-dimensional three-wave model.Non-resonant daughter waves are considered to match the conditions of radio-frequency(RF)-plasma interactions in magnetically confined plasma.Our model shows that such absolute instability has an extremely high threshold and cannot be induced for typical RF-plasma interactions,even if the linear growth rate of the instability achieves the level of ion-cyclotron frequency.As a result,we suggest that it is appropriate to neglect absolute instability when non-resonant daughter waves are involved.展开更多
基金support from the National Natural Science Foundation of China(No.12002372)the Young Elite Scientists Sponsorship Program by China Association for Science and Technology(No.2022QNRC001)the Natural Science Foundation of Hunan Province,China(No.2021JJ40674)。
文摘The operational demands of a wide range significantly exacerbate combustion instability issues within ramjet combustor.To suppress combustion oscillations,an open-loop control system utilizing Linear Genetic Programming(LGP)has been developed for a full-scale annular ramjet combustor.The LGP is used to generate control laws that include multi-frequency forcing.These laws are then transformed into square waves to actuate the solenoid valve,which modulates the kerosene supply for open-loop control.The results show that the duty cycle has little effect on instability amplitude,whereas an increase in frequency leads to a remarked reduction in combustion amplitude.After five generations evolvements,the pressure amplitude is reduced by 40.6% under the optimal control law generated by LGP.Furthermore,the machine learning process is depicted using a proximity map of control law similarity,with the search pathway visualized by the steepest descent.All individuals go forward to the upper left corner of the map with the evolution process,terminating at the optimal individual of the fifth generation.
文摘The existence of absolute parametric instability in an inhomogeneous plasma is revisited in a one-dimensional three-wave model.Non-resonant daughter waves are considered to match the conditions of radio-frequency(RF)-plasma interactions in magnetically confined plasma.Our model shows that such absolute instability has an extremely high threshold and cannot be induced for typical RF-plasma interactions,even if the linear growth rate of the instability achieves the level of ion-cyclotron frequency.As a result,we suggest that it is appropriate to neglect absolute instability when non-resonant daughter waves are involved.
