对科里奥利质量流量计的工作原理和精度影响因素进行了介绍.针对某单位计量交接用质量流量计计量误差较大的情况,分析了流量计的安装使用工作状态和瞬时流量特征,指出了瞬时流量跃变对于流量计计量精度的影响,得到了流量计误差产生的原因,针对性的提出了减小流量计计量误差的措施.

Abrasive water jet cutting (AWJ) technology has an important application prospect in emergency repair of oil depot. A new type of rear-mixed AWJ nozzle was studied in this paper, and the multiphase flow characteristics in nozzle were analyzed by numerical simulation. The results show that the negative pressure is generated inside the nozzle. As the water moves towards the downstream of the nozzle, the rigidity of the water decreases, which is beneficial to the entry of abrasives. The turbulent kinetic energy is mainly distributed in the contraction section. In order to improve the mixture of water and abrasive, it is recommended that the abrasive inlet should be as close to the contraction section as possible. At the nozzle outlet, the abrasive is mainly distributed near the wall, while the water is concentrated near the axis, and the water and the abrasives mixed unevenly at the nozzle outlet. The wear of nozzle mainly occurs at the downstream of the contraction section and upstream of the cylinder section. Although the new rear-mixed AWJ nozzle cannot completely solve the issue of uneven mixture of water and abrasive, the distribution of the abrasive inside the nozzle is more symmetrical and the nozzle wear is relatively uniform, which reduces the inhomogeneity of the abrasive and water and prolongs the service life of the nozzle.

利用Fluent计算软件对3种不同入口形状的中心体喷嘴诱发空化的情况进行模拟.结果表明:锥形入口和流线形入口喷嘴的空化区域较圆柱形入口喷嘴范围更广,空化效果更为显著;对3种喷嘴中心体后轴心速度进行比较,流线形入口喷嘴的轴心速度最高,可达到120.12 m/s,且速度衰减慢,能量损失小.

This paper attempts to disclose the cutting features and mechanism of the pre-mixed abrasive water jet (AWJ) on Q345 steel. For this purpose, several cutting experiments were performed on the pre-mixed AWJ and a Q345 steel plate. Besides, a numerical simulation model was established based on the smoothed-particle hydrodynamics (SPH) and finite-element method (FEM) and adopted to analyse the erosion features of the jet at different angles and pressures. The main conclusions are as follows: (1) There exists a pressure threshold, i.e. the jet pressure under which the abrasive erosion kinetic energy is just enough to induce material deformation. For the 80 mesh corundum abrasive particles, the pressure threshold of Q345 steel is 15 similar to 17MPa. (2) The Q345 steel suffers from deformation and failure under the high-frequency and high-speed impinging of abrasive particles. The abrasive velocity is positively correlated with the erosion ability of the abrasive particles to induce material failure. (3) The variation in the jet angle changes the vertical and horizontal jet velocities and affects the erosion process of the jet. (4) For Q345 steel, the optimal jet angle is about 80 degrees. At this angle, the jet deflection trend towards the non-material side is minimized without undermining the jet erosion ability in the vertical direction. The research findings provide new insights into the mechanism of the AWJ cutting.

前混合磨料水射流技术在应急机动抢修和受限空间中具有广阔应用前景.在前混合磨料水射流系统中,磨料罐的结构及供料原理一直被视为射流核心技术之一.本文对渗流沉降式磨料罐供料原理进行了分析,基于渗流原理设计了一种新型磨料罐.分析了不同装料量条件下磨料罐供料特性,结果表明设计的新型磨料罐供料浓度不随罐内磨料量的改变而变化,说明其具有均匀供料的特性.本文的研究能够促进前混合磨料水射流技术的应用和发展.

Abrasive water jet cutting (AWJC) technology has been widely used in metal processing field. However, the generation of striations deteriorates cutting quality. In this paper, Smoothed particle hydrodynamics (SPH) coupled Finite element method (FEM) is used to simulate and analyze the cutting process of AISI 304 stainless steel. The results show that the declining jet angle will result in uneven erosion of abrasive particles, which is caused by the generation of striation phenomenon. The research can deepen the understanding of striation phenomena in metal machining process.

The erosion process produced by pre-mixed abrasive water jet was studied by the experiment and the simulation.The morphology of erosion damage was obtained from the experiment.An erosion model was established based on the Smoothed Particle Hydrodynamics coupling Finite Element Method.By using this model,the erosion process of the material was simulated and analyzed,and the mechanism of the damage morphology of the material was revealed.The results indicate that with the increase of erosion depth,the erosion kinetic energy of abrasive particles decreased,and the erosion angle increased.The erosion damage mode changed from micro-cutting and micro-ploughing to the impact deformation,and the damage morphology characteristics of erosion surface gradually deteriorated,which reflected as increasing declination angle and surface roughness.The damage morphologies of several metals were similar,while the material property had influence on the abrasive erosion process,resulting in the differences of the distributions and the declination angles of striations on the damage surfaces.The material damage morphology was determined by the movement characteristics of abrasive particles,so the quality of the eroded surface should be improved by the control of the movement features of abrasive particles.The study can provide a theoretical basis for the further research on the improvement of material quality of eroded surface.

Abrasive water jet (AWJ) is a safe processing technology which can effectively machine almost any materials. However, due to excessive influence factors and micro-high-speed characteristics of the erosion process, traditional experiment methods have limitations in the research of the process, and the understanding of the abrasive water jet cutting (AWJC) process is not comprehensive. In this paper, the SPH coupled FEM method is used to establish the model of the pre-mixed AWJC process, and the effect of jet angle on the abrasive particle erosion process is analyzed deeply. The effect of jet angle on erosion crater sphericity is achieved from simulation results and the sphericity values are compared with the values observed in the experiments. Simulation results are in good agreement with results obtained from the experimental verification, which proves that the SPH coupled FEM method has better reliability and higher accuracy than single particle or multi-particle FEM erosion simulation. Based on the analysis of erosion crater morphology, the reason of jet angle change during AWJC process. This paper not only enriches the research method of abrasive water jet cutting process, but also contributes to the precise control of abrasive water jet cutting process.

为拓展中心体空化喷嘴的应用场合,探索中心体空化喷嘴射流流场特性,提出了在中心体空化喷嘴中采用异形中心体的思路,通过Fluent软件,对含90°锥形柱体、平头柱体和半球柱体3种不同中心体空化喷嘴射流所产生的流场进行数值模拟,重点对流场压力分布、气含率分布以及速度分布进行了对比分析.研究发现:在非淹没情况下,含90°锥形柱体喷嘴和含半球柱体喷嘴比含平头柱体喷嘴产生的空化效果更好,含90°锥形柱体喷嘴产生的楔形空泡射流具有更强的集束性能;含90°锥形柱体喷嘴和含半球柱体喷嘴射流低压区沿轴心扩散效果明显比含平头柱体喷嘴好;含半球柱体喷嘴和含平头柱体喷嘴射流在轴心线上的速度增加比含锥形柱体喷嘴更快,含锥形柱体喷嘴空化区域扩散更稳定.

In order to improve the tank derusting efficiency and expand the application of cavitation water jet technology, a new type of a central-body cavitation nozzle is designed, which is formed by cone nozzle and central body.The design of the central-body cavitation nozzle is studied.The internal and external flow fields of the nozzle with different structure parameters are numerically simulated by using Mixture multiphase flow control equation, Realizable k-ε turbulence model and Schnerr-Sauer cavitation model with Fluent software.The flow field pressure distribution, the axial velocity distribution and the gas holdup are compared and analyzed.The results show that the rationality and feasibility of the model and control equation are proved by the simulation.The designed nozzle jet flow field can effectively generate cavitation.The cavitation region mainly exists near the end of the central-body.The gap distance between the central-body and the outer nozzle and the length of the outer nozzle cylindrical section are the direct factors of influencing the cavitation forming effect.The reasonable combination of nozzle structure parameters can improve the cavitation capacity, thereby improving the quality of cleaning rust.

Physical model of pre-mixed abrasive water jet nozzle is established.Based on the software of FLUENT,numerical simulation of wear characteristic of abrasive water jet nozzle was carried out by use of particle trajectory model,Grant collision elastic recovery coefficients and E/CRC erosion model.The simulation results show that there are two severe wear sections for nozzle wear,locating within a short distance range before the entrance of cylindrical section of nozzle and before the exit of cylindrical section of nozzle respectively,when the contract angle of nozzle is above 20°.The collision frequency and velocity of abrasive particle with the wall of cylindrical section of nozzle increase with the increase of contract angle of nozzle.At the same time,wear rate of the wall of cylindrical section of nozzle increases integrally and the range of severe wear section expands with the increase of the ratio of cylindrical section length to exit diameter of nozzle.These cause the wear of cylindrical section of nozzle aggravating.The overall wear degree of the nozzle is characterized by the area-weighted average integral of nozzle wall wear rate.The area-weighted average integral of nozzle wall wear rate increases,namely the overall wear degree of the nozzle is more serious with the increase of contract angle and the ratio of length to diameter of nozzle.Therefore,the contract angle and the ratio of cylindrical section length to exit diameter of nozzle is selected small for better from the point of view of reducing the wear of the nozzle.

为提高油罐清洗除锈效率和安全性,拓展空化水射流技术的应用场合,设计了一种用锥形喷嘴与90°锥形柱体镶嵌而成的新型中心体空化喷嘴.通过Fluent软件,采用无量纲量,针对不同喷嘴出口段圆柱长度、外喷嘴直径、中心体直径以及内嵌深度参数组合的多种工况进行数值模拟,重点对射流流场的压力分布和气含率分布进行了对比分析,研究表明:所设计的喷嘴射流绕流能够有效产生空化,空化区域主要存在于90°锥形柱体末端附近;含90°锥形柱体中心体空化喷嘴结构的四大参数(L、D、d、l)必须相互配合,在l/d=1附近、L/D=1.5~2.5、D/l=2~2.5能够产生较好的空化效果.

In order to improve the cutting ability of pre?mixed abrasive water jet and the efficiency of emergency repairing, cat?ionic polyacrylamide (PAM) and cetyl trimethyl ammonium chloride (CTAC) are used as drag reducing agents and the cutting depth is chosen as the evaluation index to carry out the cutting experiment of X60 steel plate. The results show that:the addition of drag re?ducing agent can improve the cutting ability of pre?mixed abrasive jet effectively;during the pressure range of 25~40 MPa, the opti?mal additive amount of PAM is 20 mg/kg, and the optimum additive amount of CTAC/NaSal is 30 mg/kg;CTAC/NaSal is better than PAM in term of resistance reduction effect; with the addition of CTAC/NaSal, the same cutting depth can still be obtained while pump pressure is reduced by 5 MPa.

Abrasive water jet cutting technology can meet the requirements of emergency repair for oil and gas storage and trans-portation facilities. Through cutting experiments which were carried out on pipeline steel by portable abrasive water jet cutting system to research the cutting characteristic, the law for impacts of pressure, standoff distance and traverse rate on cutting depth was obtained, and then a cutting depth prediction model was put forward. The results show that the cutting depth is proportional to the pressure and in-versely proportional to the standoff distance and the traverse rate. The maximum error of prediction result of the cutting depth by the cut-ting depth model is 15. 04%, the minimum error is 0. 87%, and the average error is 5. 98%, which shows that the cutting depth model can effectively guide the cutting process establishment in a certain parameter range.

In order to improve the efficiency and safety of oil depot emergency repair, an abrasive water jet cutting (AWJC) technology is adopted for fast cutting under the conditions of high concentration of oil and gas. Through the optimal design of the pipeline system, abrasive add system and power system, a kind of portable AWJC system which is suitable for oil depot emergency repair cutting is assembled. Cutting tests for X60 pipeline steel are carried out by using this system, and a cutting model is obtained which would be used to guide the cutting operation of oil pipeline effectively. All of these researches will promote the application of portable AWJC technology and can effectively improve the efficiency of oil depot emergency repair.

The mathematical model of solid?liquid two?phase flow was established to study the flow field of pre?mixed abrasive water jet nozzle. With the software Fluent, a numerical simulation was conducted on flow field inside the cylinder nozzle, cone noz?zle, streamline nozzle and cone?cylinder nozzle, the influences of nozzle inner surface shape on flow field and abrasive particle accel?eration performance were analyzed, and the reliability of the results was validated by the abrasive water jet cutting experiment. The results show that energy loss of the cylinder nozzle is large, abrasive particle acceleration performance of the cone nozzle is bad, the streamline nozzle has good performance but is not easy to be processed, and the cone?cylinder nozzle is suitable for pre?mixed abra?sive water jet.

Based on the discrete phase model of FLUENT software,the simulation and analysis of the abrasive particle trajectory were carried on in the post-mixed abrasive focusing tube. Referring to the RNG k- e model,the turbulent kinetic energy distribution and static pressure distribution in the postmixed nozzle were obtained. By changing the size of the abrasive particle size and inlet velocity,particle movement was analyzed. Simulation results show that the particle size and the inlet velocity which is too big or too small can affect the acceleration of the particle movement and thus affect the cutting effect. The best entrance velocity of different size particles and the best particle size were obtained,which can optimize the mixing process from the aspect of reducing nozzle wear and improving the cutting effect. The experimental results are consistent with the simulation.

通过耦合空化模型和混合模型对角形喷嘴在淹没条件下产生的空化水射流流场进行了数值模拟,同时利用冲蚀实验对模拟结果进行了验证.结果表明:空化首先在圆柱段和扩散段交界上产生,并随着射流方向向前发展,流场在35 s后达到稳定;气含率随压力的增加而增大,冲蚀实验最佳的工作压力为15 MPa;湍动能主要集中在射流与周围流体之间的剪切层;相同条件下,淹没水射流的冲蚀能力是非淹没水射流的5～8倍.