A Novel Half-Bridge Power Supply for High Speed Drilling Electrical Discharge Machining

High Speed Drilling Electrical Discharge Machining (HSDEDM) uses controlled electric sparks to erode the metal in a work-piece. Through the years, HSDEDM process has widely been used in high speed drilling and in manufacturing large aspect ratio holes for hard-to-machine material. The power supplies of HSDEDM providing high power applica-tions can have different topologies. In this paper, a novel Pulsed-Width-Modulated (PWM) half-bridge HSDEDM power supply that achieves Zero-Voltage-Switching (ZVS) for switches and Zero-Current-Switching (ZCS) for the dis-charge gap has been developed. This power supply has excellent features that include minimal component count and inherent protection under short circuit conditions. This topology has an energy conservation feature and removes the need for output bulk capacitors and resistances. Energy used in the erosion process will be controlled by the switched IGBTs in the half-bridge network and be transferred to the gap between the tool and work-piece. The relative tool wear and machining speed of our proposed topology have been compared with that of a normal power supply with current limiting resistances.

Micro Electrical Discharge Machining(μEDM):Holes Drilling and Characterization of the Process Parameters

μEDM(micro-electrical discharge machining)is a process for machining conductive materials without mechanical contact;it is particularly suitable for machining hard materials.The principle consists in creating electrical discharges between a micro-tool and a workpiece,both of which are immersed in a dielectric.It is a complementary process to mechanical,laser,micro-machining techniques,and even to techniques derived from silicon microtechnology(RIE,DRIE,LIGA).However,the resolution ofμEDM is limited;it depends on several electrical and physical parameters.The goal of this paper is to characterize the holes obtained by drilling usingμEDM with different micro-tool diameters(Φ=250μm;Φ=80μm;Φ=40μm;Φ=20μm)for an experimental time of t=2 h.The results obtained let us conclude that a large diameter micro-tool(Φ=250μm)leads to removing a larger amount of material(43×10^(5)μm^(3))than small diameters:Φ=80μm;Φ=40μm;Φ=20μm where the removed volume is equal to 2.6×10^(5)μm^(3);105μm^(3);0.4×10^(5)μm^(3),respectively.The electrode-tool diameter influences the maximum depth of the holes;a diameter ofΦ=250μm generates a hole where the maximum depth is 170μm while small diameters:Φ=80μm;Φ=40μm;Φ=20μm provide holes with a depth of 82μm;51μm;50μm respectively.Through these experiments,we can also conclude that the lateral gap of the holes is almost constant.It is about 40μm whatever the diameter.

Interest of Electrical Logging in Implementation of Technical Equipment for Water Drilling: Case of the Abrobakro Collecting Field (South-East Ivory Coast)

This work concerns the collecting field of the Abrobakro site, the objective of which is to determine the thickness of the layers crossed during drilling from electrical logging in order to propose the equipment plan for the various boreholes. The electrical logging data sheets, particularly those on resistivity and expeditious granulometry using a 1.25 mm and 2 mm mesh sieve, were used. The layer thicknesses are determined with the inflection points on the graphs. The electrical logging shows that the sands in the study area have resistivity values between 400 and 5000 Ω.m. The decrease in resistivity observed at 50 m for all boreholes shows that the static level of the groundwater is at this depth. The results of the accelerated granulometry show that the first 20 meters contain more fine particles and coarse to very coarse sands from 20 m. The granulometry of the screen laying areas shows that the 1.5 mm slot openings are best suited for all drilling in the Abrobakro collecting field. The diameter d10 of the aquiferous sands of the collecting field is close to 1.25 mm.

Design of Hybrid Compensators for Power Quality Improvement of Oilfield Drilling Electrical System

With large-scale use of kinds of motors, oilfield drilling electrical system always accompanied by serious power quality problem, including reactive current, harmonics current and grid voltage distortion, which would greatly threaten the safety and proper working of the whole system. This paper focuses on a power quality improvement project to solve these problems. A hybrid compensating scheme, including an active compensator and a passive compensator, is carried out. Because of the specificity of oilfield drilling electrical system, compensators are redesigned against features of this application background. And then the current detection point arrangement of this hybrid system is also taken into consideration to build the whole system much more effective and reliable. Now the improvement project is already implemented in application field, and the power quality of the system is greatly improved.

EFFECTS OF ELECTRODE INSULATION THICKNESS ON ELECTROCHEMICAL DRILLING STABILITY AND ACCURACY

Effect of electrode insulation on the electric field and the flow field of the machining gap during electrochemical drilling（ECD） is numerically studied. Electric field simulation shows that the current density along the side gap decreases with increasing the thickness of electrode insulation. And the analysis of the electrolyte flow in the frontal gap shows that the insulation thickness has a remarkable influence on the pressure distributions. Ex- periments investigate the influence of the insulation thickness on the main characteristics of the machined hole, i.e. , radial overcut, entrance conicity, and current stability. The poor hole is observed and identified as most likely to occur with a combination of the low tool feed rate and the low insulation thickness. The appropriate thickness of the insulating layer leads to an improvement on hole accuracy and machining stability.

Advancing electrochemical drilling process via coupling of flow field and electric field in pulsating state generated by a novel tube tool

This paper introduces an improvement to electrochemical drilling process by coupling flow field and electric field in pulsating state. A novel tube with half-wedged shape at the end(HW-tube) is prepared, with both sidewall and wedged part of the HW-tube insulated. Only the flat part is utilized to provide electric field for electrochemical drilling. By rotating the HW-tube, both flow field and electric field in pulsating state are generated, alternating in different positions within the inter-electrode gap(IEG). The pulsating flow field enhances the mass transfer process, while pulsating electric field disperses material dissolution process and distribution of electrolytic byproducts. Both pulsating fields are coupled at the same frequency, further enhancing the electrochemical drilling process. Simulation results indicate that both flow field and electric field in pulsating state are generated. Compared to the traditional tube, the HW-tube significantly reduces the number of residual particles in IEG, and this number is further reduced by increasing the rotation speed. Experimental results reveal that the surface quality and dimensional uniformity of small hole are improved with HW-tube. With feed rate of 2.22 mm/min, a small hole with diameter of 1.52± 0.017 mm is drilled, resulting in a surface roughness of 0.331 μm.

随钻电成像仪器磁流激励仿真和图像增强方法

提出采用磁流替代环形线圈激励源方法模拟随钻电成像仪器(REIT)响应,在考察随钻电成像测井仪器的探测特性基础上进行环境校正方法研究,旨在获得清晰度增强图像。考虑偏心距、地层电性参数、井眼参数变化,建立仪器响应函数库,利用查库方法反演偏心距并对图像进行井眼环境校正和软件聚集增强处理,实现提高图像质量目的。结果表明,采用本文给出的方法可以对仪器原始采集的电信号进行井眼环境校正和图像增强,对提高图像质量、消除井眼环境对测量影响具有良好效果,在成像测井地层评价、随钻电成像地质导向应用中都具有重要意义。

高压电脉冲破碎非均质花岗岩数值模拟

对高压电脉冲破碎机制的研究是提高钻井破岩效率和优化电脉冲电参数的关键。利用颗粒流离散元软件及Voronoi划分建立非均匀介电性质的花岗岩模型,从电流场、电路场、电击穿场进行等离子通道生长过程仿真,并分析非均质度对击穿路径的影响;对比不同花岗岩的电破岩效率和电脉冲破岩效果。结果表明:花岗岩的非均质度增大使得初始电场极值增大,相应地降低了电破岩的能量需求;等离子通道的生长方向存在优先发展区域,等离子通道的生长过程体现出通道尖端处电场集中现象强于通道躯干处;花岗岩非均质度的差异使得等离子通道的总长度和平均贯穿深度存在显著差异,在一定非均质度范围内电脉冲破碎效果和非均质度呈正相关;不同非均质度花岗岩的单脉冲电破岩效率差异不大,等离子通道的总长度越长,电破岩效率越高。

井下油基泥浆电阻率和介电常数测量方法与测量探头设计

随着油气勘探的发展,油基泥浆应用越来越广泛,适用于油基泥浆环境的电成像仪器也获得了大量应用。油基泥浆电阻率与介电常数对电成像仪器的测量影响很大,需要利用探头附近油基泥浆电阻率和介电常数数据对成像测量结果进行补偿。介绍了一种实时测量井下油基泥浆电阻率与介电常数的方法及其探头的设计,利用发射电极、接收电极及充满在环形间隙的油基泥浆形成同轴圆柱电容器,建立油基泥浆电阻率与电容器等效电阻的定量关系及油基泥浆介电常数与电容的定量关系,从而确定油基泥浆电阻率与介电常数。该技术为补偿油基泥浆对电成像测量数据的影响提供了理论依据和技术支持。

基于高密度电法及大地电磁法的典型滑坡联合勘察与应用效果分析——以安徽黄山市歙县深渡镇约源村汪山组滑坡为例

以安徽黄山市歙县深渡镇约源村汪山组滑坡作为研究对象,在野外踏勘和测绘的基础上,运用高密度电法和大地电磁法联合勘察,并结合钻探验证资料对勘察成果进行分析。研究结果表明:电阻率参数能够很好地反映研究区的地层分布特征及滑坡体的空间分布特征,并通过钻孔资料得到了有效验证;汪山滑坡局部富水,富水区存在水力联系,是滑坡的潜在动力,推断是由于古滑坡受雨水浸入,致使产生斜坡滑移。因此,采用高密度电法以及大地电磁法联合勘察,可以有效地应用于黄山市典型滑坡的勘察中,为进一步开展黄山市滑坡的成因机理和防治研究提供参考数据。

木材深孔钻床的开发与机电设计

为了解决传统数控系统和机床结构无法直接用于木材深孔加工的问题,研究深孔加工的原理,分析重难点问题,从特殊的工装夹具系统和机床主体结构设计、机床的柔性辅助装夹系统设计、整个机床的电气控制系统和PLC内部的进给插补逻辑算法等进行研究和阐述。使用木材深孔钻床预加工16 mm的孔,测得精度为15.99 mm,完全符合加工要求。木材深孔钻床的设计与研究解决了木材在自动化深孔加工的问题,为该行业提供了解决方案。

基于高密度电法的狩猎场斜坡稳定性分析

通过对狩猎场斜坡的形态、地质构造、地层分界等信息进行获取,并进行综合稳定性分析,从而给予治理意见,保障周围居民的安全。主体采用高密度电法进行勘探,选取其中一条物探线加以少量的钻孔验证,从而获取数值模拟所需要的地质剖面图,设置合理的参数代入FLAC3D进行计算。结合物探手段与数值模拟,得出该斜坡在天然工况下处于稳定状态,但局部地区仍然有沿着软弱带滑动的风险。工程实际表明,合理的物探线布设并结合少量的工程钻探可提高勘探数据的精度,FLAC3D软件模拟切坡建房类斜坡的岩土体破坏具有一定的优势,为后续地质灾害的治理提供有力保障。

电脉冲破岩钻井地层主要参数敏感性分析

岩石的硬度、耐磨性等严重限制了深层超深层油气资源的高效开采,而电脉冲破岩钻井技术在破碎硬岩方面具有独特优势。为探究地层特性对电脉冲破岩效果的影响,根据电脉冲破岩的基本原理,并基于基本破岩单元建立了动态电损伤模型。基于动态电损伤模型,讨论了特定高压脉冲电源参数下,岩石特性对电脉冲破岩效果的影响。通过讨论分析可知,相对介电常数越大,岩石内部发生电击穿的时间成本越低,破坏深度与损伤总量也会越大;电击穿时间、破坏深度会随泊松比和弹性模量的变化出现小幅波动,但不具有规律性;岩石的密度不会对电脉冲破岩造成影响。相关结论可为电脉冲破岩钻井技术的进一步工业化应用提供一定参考。

TC4钛合金短电弧钻孔工艺性能研究

为了提高小孔钻削的加工效率和尺寸精度,文章提出了一种新颖高效的管电极短电弧钻孔方法。然而,由于电弧放电能量过大与进给速度不匹配,使得高效、高尺寸精度的小孔加工困难重重。文章揭示了基于脉冲电源的短电弧钻孔的工作原理,分析了SEAD的电压电流波形和截面形貌。此外,还研究了不同电极极性、电压、脉冲频率、占空比和电极进给速率对材料去除率(MRR)、电极相对磨损比(REWR)、平均直径和锥度的影响。最后,通过工艺参数优化实验,得到了小孔SEAD参数的最优组合,验证了小孔SEAD的加工性能。实验结果表明,在最佳加工参数下,小孔SEAD的材料去除率最高,为84.51μm/s,电极相对磨损比较低,为29.34%。加工小孔的最小平均直径和锥度分别为698.49μm和0.001 1°。

基于EVS建模分析物探-钻探在Cr(Ⅵ)污染场地勘察中的应用

为了探索物探和钻探技术在污染场地勘察中的综合应用,该研究选取河北省某铬污染场地作为案例。通过EVS软件对钻探数据进行三维建模,并结合高密度电法勘测结果综合分析了污染物的分布特征。建模结果揭示了试验地块的总体积为306.822 m^(3),其中Cr(Ⅵ)含量超标的体积达299.049 m^(3)。具体来看,超标1倍的体积为287.71 m^(3),2倍和3倍的分别仅为10.522 m^(3)和0.817 m^(3)。Cr(Ⅵ)含量在1倍超标时在地层中分布较为均匀,但在2~3倍超标时,主要集中于粉质黏土层,且底层Cr(Ⅵ)浓度较高。高密度电法勘测显示,粉砂、粉土和粉质黏土的视电阻率分别为2.5~5Ω·m、1~2.5Ω·m和小于1Ω·m,表明该技术对地层的响应良好。研究结果表明,EVS建模在清晰度和完整性方面优于传统分析方法,有助于更准确地评估污染场地的状况。此外,该方法通过区分不同土层,增强了物探分析的效能。然而,由于依赖钻探数据,模型可能受到钻孔数量的限制。高密度电法勘测作为一种有效的辅助手段,在钻探前能够识别不同地层,减少钻孔数量,同时确保模型建立的可信度。尽管如此,由于影响因素众多,视电阻率变化的原因难以简单归结。总体而言,结合EVS建模和高密度电法勘测不仅可以有效降低钻探工作量,还能准确识别污染严重区域,为污染场地的修复提供重要信息。

基于模糊PID控制的石油钻井电机控制系统

为保证石油钻井电机按照指定转速完成钻井作业,设计了基于模糊PID控制的石油钻井电机转速控制系统。系统上位机通过RS-232驱动芯片将控制指令与参数传输至DSP控制模块,DSP控制模块通过中央处理器启动增量式光电编码器跟踪电机实际转速,并结合实际转速调整控制指令后,转换成电机转速控制执行指令下达至电机速度调节器,基于模糊PID控制的电机转速控制方案控制石油钻井电机转速。实验结果表明:采用所设计系统进行控制,不论是空载工况还是负载工况,石油钻井电机都可按照指定转速运行,且转速多次切换均不存在超调问题,切换时间与转速值都与控制指令要求一致。

基于LDMs的锂电钻形态设计研究

潜在扩散模型(LDMs)是一种从文本到图像生成的模型。模型架构中的交叉注意力层可以将扩散模型变为强大而灵活的生成器,采用文本或边界框等一般条件输入,即可输出高质量图像。以电动工具典型产品锂电钻为例,提出一种基于LDMs结合低适应模型和控制网模型的形态设计和图像生成方法。

ZDY6500LQK钻机电液控制系统故障分析

ZDY6500LQK是在煤矿井下大量推广应用的一款电控钻机,其远距离遥控操作减轻了工人劳动强度,提高了安全性。但随着设备的长期使用,钻机电液控制系统难免出现故障。为了快速、准确地定位故障原因和迅速处理故障,建立了以遥控发射器调节给进压力时压力显示异常为顶部事件的故障树模型。结合实际生产,定量分析了基础事件发生的概率。结合大概率基础事件的定性分析,从维护保养和设计优化两方面提出了解决方案,为钻机电液控制系统的改进和优化提供参考。

担水沟煤矿特厚煤层开采底板导水破坏带深度实测研究

为了研究特厚煤层开采对工作面底板破坏深度的影响,通过在担水沟煤矿9204工作面底板2个观测钻孔,运用直流电法观测分析工作面回采过程中底板岩体视电阻率的变化特征,结合工作面与测点的空间位置关系,得出采动影响下的底板破坏深度,并将其与未考虑煤厚因素影响的统计公式和理论公式的计算值进行比较分析。结果表明,工作面实测底板破坏深度为17.3 m和18.3 m;实测底板最大破坏深度小于统计公式值7.81%~12.90%,大于理论公式值24.81%。探讨其机理认为,相对于工作面斜长、采深等因素,煤厚因素对底板破坏深度影响较低;且工作面底板下17 m赋存有一厚层隔水砂质泥岩,不易产生导水裂缝,降低了底板导水破坏深度。

基于超高密度电法的某铁路穿越采空区工程稳定性评价研究

为合理评价甘钟铁路某段穿越采空区工程的稳定性,采用宏观识别和详细识别两阶段技术手段进行分析。宏观识别阶段,通过现场测绘、工程地质调查,并收集采空区既有煤矿地质报告后,基本查明采空区大致范围及采煤深度。详细识别阶段,为解决小窑采空区难以高效、精确测定的难题,基于现场地形条件及宏观识别阶段确定的大致范围及埋置深度,首先利用超高密度电法物探技术特有的分辨率高、定位准确、经济、灵活等特点,查明采空区精确分布范围、大小、深度及影响铁路范围。其次针对性地采用地质钻探验证超高密度电法探测结果的准确性,并进一步明确了采空区采动带、采动冒落带及裂隙带特征。基于两阶段技术成果,从地表变形特征、开采深厚比(H/M)和顶板岩土体对场地稳定性影响三方面对采空区稳定性进行了定性评价,结论为两处采空区处于欠稳定状态。定量计算表明,1#采空区地基不稳定,2#采空区地基欠稳定。结合定性与定量评价结果,综合评定2处采空区地基稳定性结果为欠稳定状态。