This study presents the development of a medium flow, multiple slit based PM2.5 （particle aerodynamic diameter 〈2.5 μm） inertial impactor. Its performance was compared with that of a light scattering based optical...This study presents the development of a medium flow, multiple slit based PM2.5 （particle aerodynamic diameter 〈2.5 μm） inertial impactor. Its performance was compared with that of a light scattering based optical particle sizer in a field study and in controlled lab based experiments using polydisperse dolomite powder as test aerosol. The impactor＇s optimum nozzle configuration had a cutoff size of 2.51 μm （aero- dynamic diameter） at an operating flow rate of 215 L/rain with a pressure drop of 0.35 kPa across the impactor stage. Because the apparent particle density of an ambient aerosol depends on the physical properties and the chemical composition of the particles, the PM2.5 mass concentration was measured with an optical particle sizer and an inertial impactor over a weekday and a weekend day in a field study during which the effective particle shape factor and density were in tandem modified in order to com- pare the results from the two sampling techniques. The correlation of the two instrument results tended towards 1：1 with increasing values of shape factor （irregular shaped） and effective particle density. This observation was supported through chemical investigations of the collected mass, which showed a higher percentage contribution from elements which are mostly of crustal nature （namely, Ca, Fe, and Mg）.展开更多
Accurately predicting the minimum velocity required to initiate particles movement on a cuttings bed surface during drilling operations is crucial for efficient and cost-effective removal of deposited particles.Howeve...Accurately predicting the minimum velocity required to initiate particles movement on a cuttings bed surface during drilling operations is crucial for efficient and cost-effective removal of deposited particles.However,current models neglect the influence of particle shape on the drag coefficient and static friction coefficient during rolling and sliding on a cuttings bed.Accordingly,this study developed an experimental setup for cuttings transport and employed both theoretical analysis and experimental methods to investigate the critical velocity for the incipient motion of particles under various operational conditions.A novel semi-mechanical criterion model was developed for the incipient motion of particles,incorporating a shape correction factor for non-spherical particles.A balance equation for the threshold Shields number,determined by particle driving forces and resistances,was established,and a numerical procedure was formulated to determine the critical velocity for the incipient motion of particles.The model predictions show strong agreement with experimental results.The study found that higher eccentricity,inclination,and fluid viscosity increased the difficulty of initiating particle movement on the cuttings bed surface,thus requiring higher annular velocities for effective cuttings removal.Conversely,increasing particle size facilitated easier removal of the cuttings bed.Compared to non-Newtonian fluids,Newtonian fluids proved more effective in cuttings removal.The findings of this study are significant for optimizing hole cleaning parameters and improving the efficiency of cuttings removal.展开更多
文摘This study presents the development of a medium flow, multiple slit based PM2.5 （particle aerodynamic diameter 〈2.5 μm） inertial impactor. Its performance was compared with that of a light scattering based optical particle sizer in a field study and in controlled lab based experiments using polydisperse dolomite powder as test aerosol. The impactor＇s optimum nozzle configuration had a cutoff size of 2.51 μm （aero- dynamic diameter） at an operating flow rate of 215 L/rain with a pressure drop of 0.35 kPa across the impactor stage. Because the apparent particle density of an ambient aerosol depends on the physical properties and the chemical composition of the particles, the PM2.5 mass concentration was measured with an optical particle sizer and an inertial impactor over a weekday and a weekend day in a field study during which the effective particle shape factor and density were in tandem modified in order to com- pare the results from the two sampling techniques. The correlation of the two instrument results tended towards 1：1 with increasing values of shape factor （irregular shaped） and effective particle density. This observation was supported through chemical investigations of the collected mass, which showed a higher percentage contribution from elements which are mostly of crustal nature （namely, Ca, Fe, and Mg）.
基金This work was supported by the Science Research and Technology Development Foundation Project of China National Petroleum Corporation(grant No.2023DQ03-11)。
文摘Accurately predicting the minimum velocity required to initiate particles movement on a cuttings bed surface during drilling operations is crucial for efficient and cost-effective removal of deposited particles.However,current models neglect the influence of particle shape on the drag coefficient and static friction coefficient during rolling and sliding on a cuttings bed.Accordingly,this study developed an experimental setup for cuttings transport and employed both theoretical analysis and experimental methods to investigate the critical velocity for the incipient motion of particles under various operational conditions.A novel semi-mechanical criterion model was developed for the incipient motion of particles,incorporating a shape correction factor for non-spherical particles.A balance equation for the threshold Shields number,determined by particle driving forces and resistances,was established,and a numerical procedure was formulated to determine the critical velocity for the incipient motion of particles.The model predictions show strong agreement with experimental results.The study found that higher eccentricity,inclination,and fluid viscosity increased the difficulty of initiating particle movement on the cuttings bed surface,thus requiring higher annular velocities for effective cuttings removal.Conversely,increasing particle size facilitated easier removal of the cuttings bed.Compared to non-Newtonian fluids,Newtonian fluids proved more effective in cuttings removal.The findings of this study are significant for optimizing hole cleaning parameters and improving the efficiency of cuttings removal.
