Calibration of Discrete Element Heat Transfer Parameters by Central Composite Design

The efficiency and precision of parameter calibration in discrete element method （DEM） are not satisfactory, and parameter calibration for granular heat transfer is rarely involved. Accordingly, parameter calibration for granular heat transfer with the DEM is studied. The heat transfer in granular assemblies is simulated with DEM, and the effective thermal conductivity （ETC） of these granular assemblies is measured with the transient method in simulations. The measurement testbed is designed to test the ETC of the granular assemblies under normal pressure and a vacuum based on the steady method. Central composite design （CCD） is used to simulate the impact of the DEM parameters on the ETC of granular assemblies, and the heat transfer parameters are calibrated and compared with experimental data. The results show that, within the scope of the considered parameters, the ETC of the granular assemblies increases with an increasing particle thermal conductivity and decreases with an increasing particle shear modulus and particle diameter. The particle thermal conductivity has the greatest impact on the ETC of granular assemblies followed by the particle shear modulus and then the particle diameter. The calibration results show good agreement with the experimental results. The error is less than 4%, which is within a reasonable range for the scope of the CCD parameters. The proposed research provides high efficiency and high accuracy parameter calibration for granular heat transfer in DEM.

温压炸药爆温无线存储测试系统设计

温压炸药爆轰时间长、爆炸温度高且伴随爆炸破坏作用,使其爆炸温度测试较困难。为有效评估温压弹药的热毁伤效应,将存储测试技术应用到爆炸瞬态高温测试中,并结合无线传感网络技术,在确保参试人员的安全前提下,可在500 m外远程监控测试仪器状态进行智能化测试。系统采用E12型热电偶,响应时间短,最大测温为2 300℃,并对其进行可溯源性动态校准,确保测试精度。测试装置成功应用于小当量温压弹药的实爆现场测试,试验结果表明所设计的系统操作简单、使用安全,具有良好的应用前景。