The vibration instability of the nonlinear dynamic system of the rolls considering the structural clearance was theoretically investigated,which is caused by the roll assembly accuracy deviation in the hot rolling pro...The vibration instability of the nonlinear dynamic system of the rolls considering the structural clearance was theoretically investigated,which is caused by the roll assembly accuracy deviation in the hot rolling process.Firstly,the dynamic rolling force model was established based on the Wekbrod model under the influence of the roll grinding deviation and the stability of the deformation zone.Further,the horizontal and vertical direction coupling dynamic model of the work roll was established considering the structural clearance between the roll and mill frame.Then,the nonlinear dynamic equation was solved by the Runge-Kutta method.The simulation results show that the dynamic system presents the nonlinear vibration characteristics,which shows that the instability of the system is a slowly varying response process with the characteristics of self-excited vibration and forced vibration.Finally,the comparison results show the consistency between the simulation and the test.展开更多
The presence of tip clearance not only ensures the structural safety of compression system in aero-engines,but also exerts significant negative impacts on internal flow stability due to the leakage flow.Previous studi...The presence of tip clearance not only ensures the structural safety of compression system in aero-engines,but also exerts significant negative impacts on internal flow stability due to the leakage flow.Previous studies by our team have shown that the induced shock resulting from the circumferentially diverging clearance structure has remarkable effect on suppressing leakage flow in transonic compressor rotors.Therefore,the inherent correlations between the characteristics of induced shock and leakage flow are further elucidated in this paper,and the influencing rules of induced shock wave on tip flow characteristic of transonic rotors are summarized as well.The results demonstrate that the enhancement of inhibitory effects on leakage flow and increase in the rotor’s stall margin can be achieved by both intensifying the induced shock wave and shifting its circumferential position away from the suction side edge of blade tip,which is possible by adjusting the circumferential expansion ratio of diverging clearance.The stall margin of the transonic rotor exhibits three distinct variations as the circumferential expansion ratio of the diverging clearance increases monotonically,and a maximum improvement of over 8.9%can be achieved through feature variations of the induced shock wave.The insufficient acceleration of the supersonic leakage jet flow over blade tip due to a smaller circumferential expansion ratio poses challenges in inducing a shock wave,resulting in an increased blockage effect and reduced stall margin of rotor.Meanwhile,excessive circumferential expansion ratio results in a pronounced adverse pressure gradient originating from the induced shock wave,leading to leakage flow separation at the blade tip and consequently weakening the intensity of induced shock waves while shifting its circumferential position towards the blade tip.As a result,further increasing the circumferential expansion ratio does not yield an enhanced rotor stall margin but instead exhibits a slight decreasing trend.展开更多
基金supported by Regional Joint Development Fund(No.U20A20289)Project of Leading Local Science and Technology Development Fund(No.206Z1601G)+1 种基金Innovation Research Group Project of Hebei Province(No.E2021203011)Innovation Funding Project for Graduate Students in Hebei Province(No.CXZZBS2020054).
文摘The vibration instability of the nonlinear dynamic system of the rolls considering the structural clearance was theoretically investigated,which is caused by the roll assembly accuracy deviation in the hot rolling process.Firstly,the dynamic rolling force model was established based on the Wekbrod model under the influence of the roll grinding deviation and the stability of the deformation zone.Further,the horizontal and vertical direction coupling dynamic model of the work roll was established considering the structural clearance between the roll and mill frame.Then,the nonlinear dynamic equation was solved by the Runge-Kutta method.The simulation results show that the dynamic system presents the nonlinear vibration characteristics,which shows that the instability of the system is a slowly varying response process with the characteristics of self-excited vibration and forced vibration.Finally,the comparison results show the consistency between the simulation and the test.
基金the General Program of National Natural Science Foundation of China(Grant No.52076124)the Joint Fund of the National Natural Science Foundation of China(No.U2441278).
文摘The presence of tip clearance not only ensures the structural safety of compression system in aero-engines,but also exerts significant negative impacts on internal flow stability due to the leakage flow.Previous studies by our team have shown that the induced shock resulting from the circumferentially diverging clearance structure has remarkable effect on suppressing leakage flow in transonic compressor rotors.Therefore,the inherent correlations between the characteristics of induced shock and leakage flow are further elucidated in this paper,and the influencing rules of induced shock wave on tip flow characteristic of transonic rotors are summarized as well.The results demonstrate that the enhancement of inhibitory effects on leakage flow and increase in the rotor’s stall margin can be achieved by both intensifying the induced shock wave and shifting its circumferential position away from the suction side edge of blade tip,which is possible by adjusting the circumferential expansion ratio of diverging clearance.The stall margin of the transonic rotor exhibits three distinct variations as the circumferential expansion ratio of the diverging clearance increases monotonically,and a maximum improvement of over 8.9%can be achieved through feature variations of the induced shock wave.The insufficient acceleration of the supersonic leakage jet flow over blade tip due to a smaller circumferential expansion ratio poses challenges in inducing a shock wave,resulting in an increased blockage effect and reduced stall margin of rotor.Meanwhile,excessive circumferential expansion ratio results in a pronounced adverse pressure gradient originating from the induced shock wave,leading to leakage flow separation at the blade tip and consequently weakening the intensity of induced shock waves while shifting its circumferential position towards the blade tip.As a result,further increasing the circumferential expansion ratio does not yield an enhanced rotor stall margin but instead exhibits a slight decreasing trend.
