Research On Gas-liquid Ejector For Negative Pressure Drilling Vibrating Screen

As the primary equipment of drilling solid control system,drilling fluid vibrating screen is of great significance for the recovery and utilization of drilling fluid,ecological environment protection and drilling benefits in drilling engineering.With the advent of new drilling processes and advances in drilling technology,the traditional drilling fluid vibrating screen can not meet the increasing demand of drilling fluid treatment and the liquid reduction of cuttings in drilling engineering.Therefore,researchers at home and abroad are committed to the research of new drilling fluid vibrating screens.Negative pressure drilling:fluid vibrating screen is a new type of vibrating screen that adds a negative pressure system to the traditional vibrating screen.It relies on the vacuum system to form a vacuum under the screen,so that the drilling fluid on the screen passes through the screen under the combined action of the pressure difference between the screen and the vibration of the screen frame.The processing capacity of the negative pressure vibrating screen is greatly improved compared with the conventional vibrating screen,and the liquid content of the drill cuttings after processing reaches the new requirements for environmental protection of the drilling solid control system.Therefore,the new negative pressure vibrating screen can simplify the solid control system into the secondary solid control of the "vibration screen+centrifuge",which reduces the floor space and the energy consumption of the solid control system,and increases the drilling efficiency.The core equipment of the negative pressure vibrating screen is a negative pressure system,and the gas liquid ejecting device is selected as the negative pressure generating device.The performance of the gas liquid ejecting device is of great significance to the efficiency of the whole negative pressure vibrating screen.Therefore,the study of the performance of gas-liquid ejector is the primary task of rational design and use of negative pressure vibrating screen.In this paper,the gas-liquid ejector in negative pressure drilling fluid vibrating screen was studied from both theory and simulation,and the main work was as follows:(1)The structural parameters and operating parameters of the gas-liquid injector had a great influence on the performance of the injector.Based on the momentum conservation equation of fluid,the momentum conservation equation of the constant pressure and pulsed gas-liquid injector mixing chamber was derived.Based on the momentum conservation equation of the injector mixing chamber,the computational performance equations of constant pressure and pulsed gas-liquid injectors were derived by combining aerodynamics,fluid thermodynamics and computational fluid dynamics.At the same time,in order to make it easier to observe and calculate the performance of the injector,the total injection coefficient was used as an important performance index to simplify the performance equation of the gas-liquid injector under the actual working conditions,and the calculation formula of the total injection coefficient was derived.(2)Solve the theoretical performance curve of the gas-liquid injector.Based on the calculation equation of the total injection coefficient,the theoretical values of different structural parameters and working parameters were solved by MATLAB.The relationship between the constant pressure and pulsed gas-liquid ejector at different relative pressure drop?pc/ps,liquid volume fraction ?1,area ratio m and nozzle distance L12 and the total injection coefficient u of the injector was mainly studied.At the same time,the influence of parameters such as pulse law and pulse frequency on the performance of pulsed gas-liquid ejector was studied by theoretical calculation.(3)In order to verify the rationality of the derived theoretical equations,a three-dimensional simulation calculation model of constant pressure and pulsed gas-liquid injector was established.The simulation was carried out under different structural parameters and working parameters to obtain a numerical simulation performance curve in this paper.At the same time,the theoretical values of the constant pressure and pulsed gas-liquid ejector are compared with the numerical simulation results,and the trends and differences of the two performance curves were observed to verify the accuracy of the theoretical equations and numerical simulations,as well as,proving the rationality of the mathematical model and the simulation model.(4)Comparing the performance of constant pressure and pulsed gas-liquid injectors,the performandce of pulse injectors was proved to be superior to that of constant pressure injectors.At the same time,based on the conditions of total injection coefficient,vacuum degree and practical applicability,the gas-liquid injectors under different laws were optimized,and the optimal pulse law was selected.(5)Through the theoretical analysis and numerical simulation of gas-liquid ejector,the performance curves under various parameters were obtained,which provided important theoretical guidance for the structural design and field use of gas-liquid ejector.