Effect of drum structure on particle mixing behavior based on DEM method

The optimization of the drum structure is beneficial to improve the particle motion and mixing in rotary drums.In this work,two kinds of drum structures,Lacy cylinder drum(LC)and Lacy-lifters cylinder drum(LLC),are developed on the basic of cylinder drum to enhance the heat transfer area.The particle motion and mixing process are simulated by DEM method.Based on the grid independence and model validation,the contact number between particles and wall,particle velocity profile,thickness of active layer,particle exchange coefficient,particle concentration profile and mixing index are demonstrated.The influences of the drum structure and the operation parameters are further evaluated.The results show that the contact number between particles and wall is improved in LC and LLC compared to cylinder drum.The particle velocity in LC is higher than that in cylinder drum at high rotating speed,and the particle velocity of the particle falling region is significantly improved in LLC.Compared to cylinder drum and LC,the thickness of active layer in LLC is smaller,while the local particle mixing quality is proved to be the best in the active region.In addition,the particle exchange coefficients between static region and active region in the three drums are compared and LLC is found tending to weaken the particle flow.Besides,the fluctuations of particle concentration in the active region,static region,and boundary region are weakened in LLC,and the equilibrium state is reached earlier.In addition,the overall particle mixing performance in cylinder drum,LC and LLC is analyzed.The particle mixing performance in cylinder drum is the worst,while the difference in mixing quality of LC and LLC depends on the operation conditions.

Experimental investigation of the reaction-build-up for plastic bonded explosive JOB-9003

In order to measure the shock initiation behavior of JOB-9003 explosives,Al-based embedded multiple electromagnetic particle velocity gauge technique has been developed.In addition,a gauge element called the shock tracker has been used to monitor the progress of the shock front as a function of time,thus providing a positionetime trajectory of the wave front as it moves through the explosive sample.The data is used to determine the position and time for shock to detonation transition.All the experimental results show that the rising-up time of Al-based electromagnetic particle velocity gauge is very short(<20 ns);the reaction-build-up velocity profiles and the positionetime for shock to detonation transition of HMX-based plastic bonded explosive(PBX)JOB-9003 with 1e8 mm depth from the origin of the impact plane under different initiation pressures were obtained with high accuracy.

Particle image velocimetry measurement of velocity distribution at inlet duct of waterjet self-propelled ship model

A vehicle-mounted three-dimensional underwater particle image velocimetry（PIV） device is used in a towing tank to measure the velocity distribution of the inlet duct of a waterjet ship model in a self-propulsion test. The following points are shown through a comparison of the influences of the stationary and free states of the ship model on the measured results：（1） during the test, the ship attitude will change, specifically, the ship model will heave and trim,（2） the degree of freedom disturbs the processing of the pixel images enough to distort the subsequent image processing,（3） the stationary state of the ship model is the optimal mode for measuring the velocity distribution using the PIV device, and（4） if the changes must be considered, the man-made heaving and trimming may be pre-applied, and be made a corrected stationary mode. In addition, the momentum effect coefficient and the energy effect coefficient are calculated in a non-uniform inflowing state, and the related factors affecting the two coefficients are analyzed. The test results show that the pumping action of the waterjet creates a transverse vector in the cross-sectional speed, which increases the non-uniformity of the inflow. These results could help to establish the design requirements for a waterjet-propelled ship type.