| Control valves are key control components of production process automation,and are a component of industrial automation instruments.They are widely used in industries such as the marine,nuclear power,and electricity.The rapid increase in the performance of modern ships has created new challenges for control valves.Under extreme operating conditions,especially when the ship implements complex tactical actions,the flow or pressure of the fluid inside the valve suddenly changes along with the ship’s operating conditions jumping changes.The control valve bears unstable fluid loads caused by fluid oscillation.After reaching a certain opening position,the control valve fails to operate normally,endangering the safety of the ship.To eliminate the effects of sudden changes in fluid load on the control valve,the output torque of the control valve actuator is compensated on demand.The actuator is subjected to different load torques due to different flow rates,different orifices,etc.In order to accurately calculate the load torque and avoid damaging the valve stem,valve sealing surface and other structures due to excessive torque compensation,it is necessary to measure the dynamic flow rate inside the control valve,monitor the load torque of the control valve actuator and compensate the output torque as required.This paper takes the dynamic flow self-sensing of the control valve and nonlinear compensation mechanism of sudden coupling load changes as the main line of research.The formation mechanism of unstable fluid load under extreme sudden changes of operating conditions is illustrated.The dynamic flow measurement model is established.The total load model with superimposed unstable fluid load on the valve plug during the movement of the control valve is built.Based on the information of the self-sensing flow and total load of the control valve,the output torque of the actuator is dynamically compensated on demand to compensate the effect of the sudden coupling load on the performance of the control valve,which can effectively improve the operational reliability and control accuracy of the control valve.Firstly,the formation mechanism of the unstable fluid load for abrupt changes in the control valve under extreme operating conditions is studied.The plug shape of the control valve is drawn.The multi-physical field coupling model of the control valve based on machine-electric-fluid-control is established.The mechanical changes of the plug and characteristics of the flow field in the valve under sudden changes in the inlet flow rate and different plug movement speeds are analyzed.The working suitability of the linear,equal percentage and fast-opening flow characteristic control valve under sudden changes in pressure is discussed.The mechanism of unstable fluid load formation is illustrated.The coupling law between the physical fields of the control valve is revealed.The study shows that when there is a sudden change in flow rate,the pressure inside the valve and fluid load on the valve plug changes dramatically.Vortex is generated at the throttle position,the upper left side of the valve chamber,and the outlet pipeline position behind the valve.The vortex at the outlet pipeline will compress the mainstream fluid and interfere with the flow direction of the mainstream.Under different valve plug speeds,the pressure difference at both ends of the control valve caused by the same time of valve movement and the change in fluid load on the valve plug are more significant,especially when the initial movement position of the valve plug is a small opening.The higher the plug movement speed,the faster the impact of fluid on the valve plug will achieved.The adjustment time of the fast-opening flow characteristic control valve is short,but the fluid load on the valve plug is relatively large when it is in the equilibrium position.When the same flow rate is changed,the stroke required by the control valve with equal percentage flow characteristics is large.During the dynamic adjustment of the control valve,the pressure distribution at the bottom of the valve plug is asymmetric,which makes the left and right sides of the plug suffer from unbalanced forces.Secondly,the mechanism of dynamic flow measurement by flow self-sensing of the control valve is studied.Based on the throttling principle of the control valve,the method of dynamic flow measurement inside the valve cavity by the control valve is proposed,considering the influence of non-linear factors such as fluid viscous force and inertia force.The dynamic flow self-sensing model of the control valve is established.The dynamic flow self-sensing optimization model based on radial basis function neural network and combined optimization strategy is built.The mapping relationship between dynamic flow and dynamic pressure of the control valve is revealed from a theoretical perspective.The dynamic flow measurement without the use of a flow meter is realizing.The dynamic flow inside the control valve can be measured without the use of a flow meter is realized.The study shows that by analyzing the dynamic flow self-sensing performance of the control valve during the changes in the valve inlet pressure and valve opening,the self-sensing flow rate is basically consistent with the simulated flow rate.By optimizing the dynamic flow self-sensing model,the maximum relative error between the self-sensing flow rate and set value under random plug motion conditions is reduced from 11%to 6%,which improves the accuracy of the self-sensing flow rate.Then,the dynamic non-linear compensation of the unstable fluid load of the control valve is studied.By quantitatively transforming the momentum of the fluid system into the expression of the control body,the total load model of the valve plug under unstable fluid loads is established.The principle and method of the dynamic compensation of the unstable fluid load of the control valve are proposed,The co-simulation model of AMESim and MATLAB/Simulink with the control valve system and load compensation module is constructed.The influence of different compensation coefficients on the load torque,servo motor output torque and actuator plug displacement is illustrated.The selection strategy of the compensation coefficient is revealed.The best compensation coefficient is provided.The self-sensing of the load torque of the actuator and dynamic compensation of the actuator output torque are achieved.The study shows that when the inlet pressure of the control valve undergoes a sudden change,by compensating the output torque of the actuator,the stability time of the valve is shortened from more than 6s to 4.46s.And the fluid load on the valve plug increases during this process.After the compensation starting value of the servo motor is given,the compensation effect is significant and the response time of the control valve becomes shorter when the load torque is greater than the compensation starting value.The larger the compensation coefficient,the higher the maximum output torque of the servo motor.However,the control valve may be over-controlled resulting in longer stability time.And the energy consumption of the motor is also increased.Finally,the experimental system of the control valve is developed.And the validation is performed.The experimental platform for the control valve system is built.The flow regulation characteristics,flow measurement,and self-compensation experiments on the control valve system is carried out.By the experiments of the flow regulation characteristics,the accuracy of the control valve modeling and reliability of the simulation data are verified,By measuring the flow rate of the control valve under fixed opening and motion conditions.the experimental flow rate is basically consistent with the self-sensing flow rate,verifying the accuracy of the self-sensing flow rate model.By conducting self-compensation experiments on the control valve system under the conditions of the sudden change of the inlet target pressure and sudden change of the inlet flow,the response time of the control valve is shortened from 59s to 47s.And the adjustment time of the inlet pressure is shortened.The compensation effect is obvious,.which verifies the feasibility of the compensation principle and method proposed in this paper.The compensation coefficient is not the larger or the better,and the reasonable compensation coefficient should be selected based on the actual working condition. |
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