Numerical solution for dynamics of pneumatic DTH hammer system

The pneumatic down-the-hole(DTH) hammer is one of the efficient equipments used in medium hard to very hard rock drilling frield,and any change in its structure design affects all performance parameters of a pneuamtic DTH hammer directly.Yet,owing to the complexity of the dynamic interaction among the components in DTH hammer systems,until now it has been difficult to obtain reliable estimates of the design parameter affects.Thus providing an design parameter optimization and the layout of dynamics behavior of DTH hammer is of great importance.This paper documents the development and solution of a computational model for the dynamic response of a pneumatic DTH hammer.The model consists of rigid piston dynamics equation and chamber thermodynamics equations.The resulting model represented by a set of coupled nonlinear differential equations were computed in Visual C++ program.The developed solutions are used to perform a parametric study to illustrate the inffluence of the piston mass and supply pressure on the impact performance of DTH hammer system.

Structure Parameters Optimization Analysis of Hydraulic Hammer System

In order to improve the impact performance, the structure of hydraulic hammer should be optimized. In this paper, the ranges of eight vital structure parameters of piston and reversing valve system of hydraulic hammer were selected firstly;and then found the best value of different parameters under experiments with the method of computer optimization and the parametric analysis method provided by ADAMS software. These methods worked and the best design values of parameters of hydraulic hammer were obtained. At last, the optimal impact energy of virtual prototype of hydraulic breaking hammer was calculated and compared with the original impact performance. The results reveal that impact performance of hydraulic hammer has been improved significantly.

Water hammer protection for diversion systems in front of pumps in long-distance water supply projects

For a water supply system with long-distance diversion pipelines, in addition to the water hammer problems that occur beyond pumps, the safety of the water diversion pipeline in front of pumps also deserves attention. In this study, a water hammer protection scheme combined with an overflow surge tank and a regulating valve was developed. A mathematical model of the overflow surge tank was developed, and an analytical formula for the height of the overflow surge tank was derived. Furthermore, a practical water supply project was used to evaluate the feasibility of the combined protection scheme and analyze the sensitivity of valve regulation rules. The results showed that the combined protection scheme effectively reduced the height of the surge tank, lessened the difficulties related to construction, and reduced the necessary financial investment for the project. The two-stage closing rule articulated as fast first and then slow could minimize the overflow volume of the surge tank when the power failure occurred, while the two-stage opening rule articulated as slow first and then fast could be more conducive to the safety of the water supply system when the pump started up.

基于Bently-Hammer软件的长距离输水管道水锤防护模拟

基于Bently-Hammer软件对某实际工程中长距离输水系统进行建模,通过实际运行中的不同工况,模拟突发事件在管道与水泵间产生的水锤影响,同时针对系统内突发事件增加液压气动罐、缓闭止回阀等水锤消除措施加以改进,为实际工程提供有效抑制水锤破坏的技术保障。

Digital monitoring of rotary-percussive drilling with down-the-hole hammer for profiling weathered granitic ground

Rock and geotechnical engineering investigations involve drilling holes in ground with or without retrieving soil and rock samples to construct the subsurface ground profile.On the basis of an actual soil nailing drilling for a slope stability project in Hong Kong,this paper further develops the drilling process monitoring(DPM)method for digitally profiling the subsurface geomaterials of weathered granitic rocks using a compressed airflow driven percussive-rotary drilling machine with down-the-hole(DTH)hammer.Seven transducers are installed on the drilling machine and record the chuck displacement,DTH rotational speed,and five pressures from five compressed airflows in real-time series.The mechanism and operations of the drilling machine are elaborated in detail,which is essential for understanding and evaluating the drilling data.A MATLAB program is developed to automatically filter the recorded drilling data in time series and classify them into different drilling processes in sub-time series.These processes include penetration,push-in with or without rod,pull-back with or without rod,rod-tightening and rod-untightening.The drilling data are further reconstructed to plot the curve of drill-bit depth versus the net drilling time along each of the six drillholes.Each curve is found to contain multiple linear segments with a constant penetration rate,which implies a zone of homogenous geomaterial with different weathering grades.The effect from fluctuation of the applied pressures is evaluated quantitatively.Detailed analyses are presented for accurately assess and verify the underground profiling and strength in weathered granitic rock,which provided the basis of using DPM method to confidently assess drilling measurements to interpret the subsurface profile in real time.

基于Bentley Hammer的长距离有压管道输水工程的水锤防护研究

【目的】在长距离有压管道输水工程中,因管道内部水流条件复杂而容易产生水锤现象,不仅会影响水流正常输送,还可能导致管道破裂。因此,有必要进行长距离有压管道输水工程的水锤防护研究。【方法】基于台前县城乡供水一体化南水北调配套工程,通过Bentley Hammer软件,在最不利工况下分别建立三种数值模拟模型:无防护措施、加装复合式高速进排气阀水锤防护、气囊式空气罐和复合式高速进排气阀,进行联合水锤防护,对以上三种情况进行水力过渡过程数值模拟分析,研究复合式高速进排气阀与气囊式空气罐联合防护时的水锤防护效果以及气囊式空气罐的防护能力与预设压力和罐体体积之间的关系。【结果】结果表明:复合式高速进排气阀和气囊式空气罐可以很好地消除管道内水锤带来的危害,气囊式空气罐防护能力随着罐体体积和预设压力的增大而增强,罐体体积对其防护能力影响更显著。【结论】选择合理的罐体体积和预设压力可以使水锺防护发挥最好的防护效果,最大化输水工程的经济性。

基于BentleyHammer的长距离压力输水管道水锤模拟分析

水锤模拟分析在保证工程安全运行、减少事故发生、降低人身财产风险损失等方面具有十分重要的意义。本文利用Bentley Hammer水锤分析软件,以某县城工业园区供水工程为例,模拟长距离压力输水管道工程非正常运行条件下管道水力工况,分析制定安全可靠、合理可行的水锤防护方案,保证供水工程运行安全,为长距离压力输水管道工程水锤防护方案的设计提供参考。

Bentley Hammer V8i软件在城乡一体化供水管道水锤计算中的应用

应用Bentley Hammer V8i软件模拟城乡统筹供水工程中输水和配水管道的稳态工况与事故断电工况的水锤安全性,可以清楚地展示管内水流压力的变化趋势。本文以新和县城乡一体化实际供水工程为研究对象,评估其供水管网水锤安全性。模拟结果显示,虽然该工程在稳态工况与事故断电情况下管道内压力会有剧烈波动,但仍在管道的承载能力之内,可以通过优化关阀时间及相关操作来确保供水的安全稳定。本应用可供类似城乡一体化供水工程管道设计参考。

RESEARCH OF THE DYNAMIC CHARACTERISTICS ON A NEW HYDRAULIC SYSTEM OF ELECTRO-HYDRAULIC HAMMER

A new typed hydraulic system of electro hydraulic hammer is researched and developed By means of power bond graphs the modeling and simulation to the dynamic characteristics of the new hydraulic system are performed The experimental research which is emphasized on the blowing stroke is also performed It is proved from the result of simulation and experiment that this new hydraulic system possesses such advantages as simplification of structure,flexibleness of operation and reliability of working Especially it possesses better dynamic characteristics

Flux Vector Splitting Schemes for Water Hammer Flows in Pumping Supply Systems with Air Vessels

To solve water hammer problems in pipeline systems,many numerical simulation approaches have been developed. This paper improves a flux vector splitting( FVS) scheme whose grid is the same as the fixedgrid MOC scheme. The proposed FVS scheme is used to analyze water hammer problems caused by a pump abrupt shutdown in a pumping system with an air vessel. This paper also proposes a pump-valve-vessel model combining a pump-valve model with an air vessel model. The results show that the data obtained by the FVS scheme are similar to the ones obtained by the fixed-grid method of characteristics( MOC). And the results using the pump-valve-vessel model are almost the same as the ones using both the pump-valve model and the air vessel model. Therefore,it is effective that the proposed FVS scheme is used to solve water hammer problems and the pump-valve-vessel model replaces both the pump-valve model and the air vessel model to simulate water hammer flows in the pumping system with the air vessel.

FGC-15D large-diameter DTH air hammer drilling system and its application in offshore rock-socketed pile hole drilling

In the past two decades, numerous large-diameter rock-socketed piles were constructed in China to support foundations of skyscrapers, great bridges or to retain soil in potential geological hazard areas. However, drilling large-diameter rock-socketed pile holes with conventional drilling method such as rotary drilling or cable tool drilling is time-consuming and the cost is usually very high. In order to drill large-diameter rocksocketed pile holes faster at relatively low cost, the FGC15A large-diameter DTH air hammer drilling system was developed in 1987 and was given the second-clasa award by Ministry of Geology and Mineral Resources in 1991. Since it was innovated the drilling system has been used in more than twenty important and tough pro- jects on land, and wonderful results were acquired. At the same time the large-diameter DTH air hammer drilling system was improved continuously. The FGC15D is the latest version of the technique.

Construction and Solution to a New Dynamic Model of Forging Hammers Damping System

For the directly supported isolated foundation which includes returning isolator, a new dynamic model of forging hammers damping system is founded. This system is solved by model analysis to get a set of new calculating formulas about the vibration parameters of anvil and foundation.

基于Bentley Hammer的泵站输水系统管道优化前后的水力过渡过程研究

为了研究泵站输水系统管道优化前后事故停泵的水力过渡过程的特性,基于实际工程,运用Bentley Hammer软件,建立泵站输水系统双泵并联机组数学模型,研究两阶段不同关阀方案下管道优化前后对水锤压力、机组转速等最不利水锤参数的影响。结果表明,管道优化后最大水锤压力降低了3.76%~8.85%,最小水锤压力提升了4.89%~8.85%,最大倒转速度提高了1.47%~81.35%;快关时间对最不利水锤参数有显著影响,管道优化后泵站输水系统最不利水锤参数均比优化前提前发生。表明管道优化有效改善了泵站输水系统的水锤特性,提高了泵站输水系统的安全性。

Selection of Hammering Sound Collection Devices for the Development of Total Hip Arthroplasty Support Systems

In total hip arthroplasty, intraoperative femoral fractures can be avoided by analyzing the hammering sounds from the stem inserted into the femur. This procedure is based on a hammering test that makes use of the fact that sound depends on the stability of the object. This technique is generally used in engineering. A system designed to avoid excessive stem hammering by predicting the intraoperative fracture risk based on this technique and software for real-time spectra analysis has been developed with repetitive improvements. The remaining technical challenge lies in selecting an appropriate sound collection device and building a compact and easy unit for use. This study reviewed the types of directional microphones suitable for the sound collection system to develop a practical THA support system. Four types of microphones based on selected methods were used to collect and compare the peak frequencies of the hammering sounds and make comparisons between them, and the built system was used to conduct clinical trials. For miniaturization and operational ease of the unit, plug-in unidirectional microphones are appropriate. However, no laboratory-level data has been collected, and thus, further data accumulation is necessary.

Performance of large-diameter pneumatic down-the-hole (DTH) hammers: A focus on influences of the hammer structure

Pneumatic down-the-hole (DTH) hammer has been extensively used in air drillings through hard and ultra-hard geological formations. Numerical modeling can offer close observation on the working behaviors by visualizing internal pressure status as well as provide reliable performance predictions for large-diameter DTH hammers to which conventional empirical and experimental approaches cannot be applied. In this study, CFD simulations coupled with dynamic meshing are utilized to simulate the air flow and piston movement inside the large-diameter DTH hammers. The numerical modeling scheme is verified against a theoretical model published in literature. Effects of structural parameters on hammer performance, including piston mass, piston upper-end diameter, piston groove diameter, and lengths of intake and exhaust stroke in both front and rear chambers, are analyzed in detail by virtue of sets of numerical simulations. The simulations suggest that changing the intake stroke of front chamber has a negligible influence on hammer performance while increasing the piston groove would lower all the four indicators of hammer performance, including impact energy, impact frequency, maximum stroke, and air consumption rate. Changing the other structural parameters demonstrates mixed effects on the performance indicators. Based on the numerical simulations, a large GQ-400 DTH hammer has been designed for reduced air consumption rate and tested in a field drilling practice. The air drilling test with the designed hammer provided a penetration rate 1.7 times faster than that of conventional mud drilling.

Research on Breeze Vibration Law and Modal Identification Method of Conductor Considering Anti-Vibration Hammer Damage

In the harsh environment,the structural health of the anti-vibration hammer,which suffers from the coupled effects of corrosion and fatigue damage,is significantly reduced.As part of the conductor structure,the anti-vibration hammer is rigidly attached to the conductor,effectively suppressing conductor vibration.The conductor’s breeze vibration law and natural modal frequency are altered damage to the anti-vibration hammer structure.Through built a vibration experiment platform to simulate multiple faults such as anti-vibration hammer head drop off and position slippage,which to obtained the vibration acceleration signal of the conductor.The acceleration vibration signal is processed and analyzed in the time and frequency domains.The results are used to derive the breeze vibration law of the conductor under multiple faults and propose an anti-vibration hammer damage online monitoring technology.The results show that the vibration acceleration value and vibration intensity of the conductor are significantly increased after the anti-vibration hammer damage.The natural frequency increases for each order,with an absolute change ranging from 0.15 to 6.49 Hz.The anti-vibration hammer slipped due to a loose connection,the 1st natural frequency increases from 8.18 to 16.62 Hz.Therefore,in engineering applications,there can be no contact to determine the anti-vibration hammer damage situation by monitoring the modal natural frequency of the conductor.This is even a tiny damage that cannot be seen.This method will prevent the further expansion of the damage that can cause accidents.

长距离多支线有压输水系统起动水锤防护

为研究同时包含重力流输水管线与泵站加压提水管线的长距离多支线有压输水系统开启运行时的水锤问题,基于瞬变流分析的特征线法建立了输水系统过渡过程计算的数学模型,结合实际工程计算了输水系统开启运行时调节阀与水泵及其出口阀不同的开启时间与控制策略对水锤的影响,并在此基础上提出了空气阀联合阀门开启的水锤防护方案。结果表明:采取提水泵站滞后调节阀开启运行,且各提水泵站相继开启的策略可有效改善输水系统沿线的内水压力分布;采用空气阀联合阀门开启的水锤防护方案可在不影响输水系统反应速度的情况下以较小尺寸的空气阀达到较好的水锤防护效果。

泵站过渡过程计算及水锤防护措施研究

文章介绍了水锤的基本概念、泵站水锤的危害、水锤防护研究的目的及意义。通过HAMMER软件对实际工程的供水系统进行数字建模,并对事故停泵时水力过渡过程进行模拟计算,对不同防护措施下的计算结果进行对比,最终提出更适合工程的预防水锤发生的防护措施,从而保证供水系统安全运行,可为类似的工程设计提供参考依据。

有压输水系统水锤防护方案探讨

水锤是有压输水系统中一种极为常见的现象,而长距离、高扬程和大流量输水项目的水锤防护,对工程运行安全显得尤为重要。通过对水锤现象的探讨,分析产生水锤的基本因素,梳理常见的水锤防护措施,提出针对不同情况应采取相应的水锤防护方案;对流速、管线布置、管材、管长和管道最大工作压力等设计参数分析,通过工程案例选取调流调压阀、两阶段缓闭阀、空气阀、空气罐、超压泄压阀、调压塔及增加机组转动惯量等其中适合工程实际的水锤防护措施,使系统水锤危害得到有效缓解,可为类似工程提供经验和借鉴。

基于Hammer积分的三维地面磁共振高精度正演方法

为满足三维地面磁共振正演计算的精度要求,本文提出了基于非结构不均匀四面体网格的Hammer积分算法。首先利用有限元方法实现了对地下空间的三维磁场计算,完成了地面磁共振灵敏度核函数表达式的推导。针对现有地面磁共振正演方法中常规网格尺寸大、计算精度差、细化网格尺寸小、但是数量大的问题,应用Hammer积分在常规网格中完成核函数的高精度计算。三维核函数和3个含水模型的正演仿真实验表明:基于Hammer积分的地面磁共振正演方法具有网格少、计算节点少、积分精度高的特点,能够高效解决核函数的正演计算问题。