新型耐空蚀Cr-Co-Ni-Mn奥氏体不锈钢研究

制备了一种Cr-Co-Ni-Mn含钴奥氏体不锈钢。与304不锈钢比较,研究了其抗空蚀性能,用TEM观察了空蚀试样的组织结构,并测定了该钢种的强度,利用时效处理研究其组织稳定性。结果表明Cr-Co-Ni-Mn含钴奥氏体不锈钢屈服强度、抗拉强度比常用的304不锈钢高,奥氏体组织稳定,空蚀孕育期长,耐空蚀效果好。TEM观察到试样空蚀作用层有ε马氏体组织,这些形变组织有利于吸收应变能,提高材料耐空蚀能力。综合该钢的性能,在耐空蚀领域有潜在的应用前景。     

离心泵的汽蚀及提高抗汽蚀能力的措施

离心泵是制药的重要通用设备,而汽蚀对离心泵的危害很大,它使离心泵的性能下降、使过流部件点蚀、甚至产生振动和噪音,严重地影响离心泵正常工作。在实际生产应用中,从设计、选用、安装和运行几方面综合考虑,以提高了离心泵的抗汽蚀能力。     

空化水射流理论和应用研究

分析了空化水射流的三种主要形式:普通空化水射流、自振空化水射流、自激脉冲空化水射流。综述了空化水射流空化初生的判据和应用状况,为进一步扩展空化水射流的应用范围提供了可借鉴的思路。     

水轮机压力脉动测试的分析与探讨

介绍了水轮机压力脉动试验中测量位置、测点数量、信号采样频率及采样时间、空化系数等因素对压力脉动试验结果的影响,并提出在进行压力脉动试验时,应增加测点,延长采样时间,提高采样频率,以避免信号遗漏和信号混叠等现象的发生。建议对水轮机的重要运行工况,应增加不同空化系数下的压力脉动试验,以避免在真机运行时可能产生“空化自激”现象,确保原型机组的安全运行。     

涡凹气浮在炼油污水处理中的应用

阐述了涡凹气浮的原理及特点，并结合扬子石化炼油厂污水处理场改造的工程实例，采用涡凹气浮法处理污水，可以使污水的含油去除率达到88.2％，出水含油量为17．7mg／L，满足出水水质指标。与溶气气浮法相比，该法具有节省投资和占地，节能降耗，减轻操作强度的优势。     

窄脉冲声场中空化峰对声化学反应器设计的作用

用声致发光在声强<0.5W/cm2时记录到脉冲声场中脉冲占空比为1∶1,脉冲宽度为300～400μs时空化效应出现峰值,即出现空化峰。这一效应对于在低声强(<0.7W/cm2)下引发声化学反应和降低声化学反应的声能耗有意义     

Electrochemical behaviour of high strength steel wires in the presence of chlorides

The present work summarises results of the electrochemical behaviour of high strength steel wires in a high alkaline medium simulating the solution present in concrete. The aim is to expose the possible factors affecting the initiation period of stress corrosion cracking, the most frequent form of failure of pre-stressed concrete structures.Cold drawn steel wires were subjected to constant stress at 70% of their ultimate tensile strength and exposed to corrosive environments in order to study the stability of the passivating layer. The effects of chloride concentration, temperature, presence of oxygen, and cavitation induced by ultrasonic waves were studied. Two different techniques (cyclic voltammetry and impedance spectroscopy) were employed to study the effects of those parameters on the formation/breakdown of the passive layer. The results show that variations in the studied parameters can provoke breakdown of the passivating layer even at very low chloride concentrations. Chlorides, oxygen availability, temperature changes, and vibrations have been found to be important factors in the corrosion initiation of pre-/post-tensioned tendons.     

Nucleation,growth and transport modelling of helium bubbles under nuclear irradiation in lead–lithium with the self-consistent nucleation theory and surface tension corrections

Helium (He) nucleation in liquid metal breeding blankets of a DT fusion reactor may have a significant impact regarding system design, safety and operation. Large He production rates are expected due to tritium (T) fuel self-sufficiency requirement, as both, He and T, are produced at the same rate. Low He solubility, local high concentrations, radiation damage and fluid discontinuities, among other phenomena, may yield the necessary conditions for He nucleation. Hence, He nucleation may have a significant impact on T inventory and may lower the T breeding ratio.A model based on the self-consistent nucleation theory (SCT) with a surface tension curvature correction model has been implemented in OpenFOAM^® CFD code. A modification through a single parameter of the necessary nucleation condition is proposed in order to take into account all the nucleation triggering phenomena, specially radiation induced nucleation. Moreover, the kinetic growth model has been adapted so as to allow for the transition from a critical cluster to a macroscopic bubble with a diffusion growth process.Limitations and capabilities of the models are shown by means of zero-dimensional simulations and sensitivity analyses to key parameters under HCLL breeding unit conditions. Results provide a good qualitative insight into the helium nucleation phenomenon in LM systems for fusion technology and reinforces the idea that nucleation may not be a remote phenomenon, may have a large impact on the system's design and reveals the necessity to conduct experiments on He cavitation.     

MECHANISM AND PREDICTION OF MATERIAL ABRASION IN HIGH-VELOCITY SEDIMENT-LADEN FLOW

1. INTRODUCTION There are many heavily sediment-laden rivers in China, where the silt abrasion of hydraulic projects caused by high-velocity sediment-laden flow is severe. Prediction of the silt abrasion damage at the concrete surface in heavily sediment-laden rivers is one of the important problems to be solved in water conservancy and hydropower engineering. It is necessary to study the mechanism and prediction of material abrasion. In recent years, many researchers have focused their a…     

水轮机空化特性的人工神经网络模型

本文针对水轮机空化特性相对应的空间曲面比较复杂的特点，用径向基函数神经网络建立水轮机空化特性模型，对样本的学习采用Levenberg-Marquardt算法。该模型应用于四川紫坪铺水力发电厂中的水轮机空化特性研究。模拟计算结果与试验结果的比较表明，本文给出的模型能真实地表达水轮机的空化特性，可以在水轮机的计算机辅助选型设计和水轮发电机组的优化运行分析等方面应用。