改进的特征线方法及过载对水锤效应影响分析

传统特征线方法对过载作用下的水锤计算具有局限性，无法为水锤防护提供可靠性指导。本文在考虑过载效应和动态摩阻的基础上，提出了改进的特征线方法，该方法能准确模拟过载作用下水锤最大压力峰值及水锤波的衰减特性。基于该方法，建立了过载作用下水锤效应数学模型，通过分析结果与CFD数值仿真及实验数据对比，验证了改进特征线方法的正确性。分析结果表明，在恒定过载作用时，阀门位置的流体压力随过载量的增加而增大，且管轴向过载的影响大于横向过载；关阀过程受到瞬时过载作用时，过载效应对水锤最大压力峰值影响显著，而对关阀后水锤波的传播和衰减影响较小；同时，分析了过载效应下关阀特性和流体密度等参数对水锤效应的影响规律。     

Effects of WC-Co reinforced Ni-based alloy by laser melting deposition: Wear resistance and corrosion resistance

WC-Co reinforced C276 alloy composite coatings are fabricated on Q235 steel by laser melting deposition.The microstructure,hardness,wear performance,and electrochemical corrosion behavior of composite coating are studied.The results show that WC-Co particles are mostly uniformly distributed in the coating and provide favorable conditions for heterogeneous nucleation.The microstructure of C276/WC-Co composite coatings is composed of γ-Ni solid solution dendrites and MoNi solid solution eutectics.The WC-Co particles can effectively improve the hardness and wear resistance of C276 alloy.The average hardness of the composite coating containing 10-wt% WC-Co(447 HV_0.2) are 1.26 times higher than that of the C276 alloy(356 HV_0.2).The wear rate of composite coating containing 10-wt% WC-Co(6.95 ×10^-3 mg/m) is just 3.5% of that of C276 coating(196.23 × 10^-3 mg/m).However,comparing with Hastelloy C276,the corrosion resistance of C276/WC-Co composite coating decreases.