环空流体吸入式自激振荡脉冲射流调制元件结构优选研究

为充分利用井底水力能量提高破岩钻井效率,提出了环空流体吸入式自激振荡脉冲射流钻井技术。将数值模拟和试验研究相结合,分析了环空流体吸入式自激振荡脉冲射流调制元件结构参数的变化对射流破岩性能的影响。对比分析了调制元件的环空吸入量、出口流速、振荡腔负压值和进出口压差与射流破岩效果之间的关系,结果发现调制元件进出口的压差越大,射流破岩效果越好,二者呈显著线性相关。以调制元件进出口压差为优选依据,采用正交试验法,进行了数值模拟试验,优选了调制元件的结构参数,数值计算与试验结果吻合良好,表明分析环空流体吸入式自激振荡脉冲射流性能,优选调制元件结构的方法可行。所得结论可作为射流调制元件结构设计和优化的依据。     

DRILLING CHARACTERISTICS OF COMBINATIONS OF DIFFERENT HIGH PRESSURE JET NOZZLES

The high speed fluid jet for directly or indirectly breaking rock is one of the most effective ways to improve the deep penetration rate.In order to maximize the efficiency of energy use,the flow characteristics of different combinations of high pressure jet nozzles are analyzed through numerical simulations.According to the velocity vectors at the bottom and the bottom hole pressure diagram,the effects of the high pressure nozzle combinations on the flow structure and the penetration rate are analyzed.It is shown that the combination of three vertical edge nozzles is very efficient,but inefficient in cleaning the bottom hole and eroding the wall.The jet velocity is 400 m/s and the radius is 5 mm,with a center nozzle added,the problem can be solved,but the high-pressure fluid displacement would increase.The center nozzle’s jet velocity is 200 m/s and the radius is 8 mm,the combination of two vertical edge nozzles and a center tilt nozzle or that of a vertical edge nozzle and a center tilt nozzle would provide a flow structure favorable for drilling.The angle of inclination is 10o.To take advantage of high pressure jet energy to improve the efficiency of drilling,it is important to select a suitable nozzle combination according real conditions.     

RANDOM ANALYSIS OF HYDRODYNAMIC CHARACTERIS-TICS OF TRAJECTORY JET CAUSED BY DIFFERENT TYPES OF PIERS

1.　INTRODUCTIONThe energy dissipation problem of overflow damsisalwaysofgreatconcern to hydraulicengineers.Friction and collision,which can be produced by bottom current,surface currentand water jetlashing,are two primary ways of energy dissipation.Designers can deal withthe problem according to their own situation.In this paper,some experiments are reportedon the tail pattern ofpiers.Itis well known thatdeep pithole and far horizontal distance ofthe jet trajectory occur when a flat-tail…     

DETERMINATION OF ROCK-BREAKING PERFORMANCE OF HIGH-PRESSURE SUPERCRITICAL CARBON DIOXIDE JET

In this study, a well-designed experimental setup is used to determine the rock-breaking performance of a high-pressuresupercritical carbon dioxide (SC-CO2) jet. Its rock-breaking performance is first compared with that of a high-pressure water jetunder the same operation conditions. The effects of five major factors that affect the rock-breaking performance of the high-pressureSC-CO2jet, i.e., the nozzle diameter, the standoff distance, the jet pressure, the rock compressive strength and the jet temperature areexperimentally determined. The experimental results indicate that the rock-breaking performance of the SC-CO2jet is significantlyimproved over the high-pressure water jet. It is also found that the rock-breaking performance of the SC-CO2jet is improved with theincrease of the nozzle diameter or the standoff distance, until the nozzle diameter or the standoff distance reaches a certain criticalvalue and after that it begins to deteriorate. The rock-breaking performance of the SC-CO2jet improves monotonically with theincrease of the jet pressure, while it shows a monotonic deterioration with the increase of the rock compressive strength. In addition,it is found that, under the same working conditions, the SC-CO2jet can always provide a better rock-breaking performance than thesubcritical liquid CO2jet.     

AERATION EFFECT OF SUBMERGED JET ON HYDRAULIC CHARACTERISTICS

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＪｅｔｆｌｏｗｈａｓｂｅｅｎｅｘｔｅｎｓｉｖｅｌｙａｐｐｌｉｅｄｆｏｒｅｎｅｒｇｙｄｉｓｓｉｐａｔｉｏｎ .Ｉｎｄｅｓｉｇｎ ,ｈｏｗｅｖｅｒ,ｂｅｃａｕｓｅｏｆｔｈｅｃｏｍ ｐｌｅｘｉｔｙｏｆｐｒｏｂｌｅｍａｎｄｔｈｅｄｉｆｆｉｃ     

SCALE EFFECT OF IMPINGING PRESSURE CAUSED BY SUBMERGED JET

The characteristics of the impinging pressure at the jet equipment where the maximum jet velocity can reach 50m/s were studied. By comparing the impinging pressure with the one measured at the low velocity conditions, two conclusions of the scale effect are drawn： firstly, the velocity attenuation degree is smaller than that of low velocity jet, and secondly, the relative impinging width is narrower than that of low-velocity jet. The reasons of the scale effect of the impinging pressure were elucidated through numerical simulation.     

TRANSMISSION BEHAVIOR OF MUD-PRESSURE PULSE ALONG WELL BORE

In oil and gas industry,mud-pulse telemetry has been widely used to obtain directional data,drilling parameters,formation evaluation data and safety data,etc. Generally,the drilling mud in most current models was considered to be a single-phase fluid through which the mud pulses travel,despite the fact that the drilling mud is composed of two or more phases. In this article,a multiphase flow formula was proposed to calculate the mud-pulse velocity as mud solids and free-gas content change,and a mathematical model was put forward to simulate the dynamic-transmission behavior of the mud-pressure pulse or waves. Compared to conventional methods,the present model provides more accurate mud-pulse attenuation,and the dynamic-transmission behavior of drilling-mud pulses along well bores can also be easily examined. The model is valuable in improving the existing mud-pulse systems and developing new drilling-mud pulse systems.     

NUMERICAL MODELLING OF THE WATER AIR TWO PHASE JET INTO A PLUNGE POOL

１．　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｃｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆｆｌｏｗｆｉｅｌｄａｎｄｅｎｅｒｇｙｄｉｓｓｉｐａｔｉｏｎｉｎｐｌｕｎｇｅｐｏｏｌａｒｅｏｆｐｒａｃｔｉｃａｌｉｍｐｏｒｔａｎｃｅｆｏｒｄａｍｅｎｇｉｎｅｅｒｉｎｇ．Ｔｈｅａｒｅａｔｉｏｎｈａｓｉｍｐｏｒｔａｎｔｅｆｆｅｃｔｓｏｎｔｈｅｆｌｏｗｉｎｐｌｕｎｇｅｐｏｏｌ［１］　．Ｉｎｔｈｅｃｏｎｖｅｎｔｉｏｎａｌｍａｔｈｅｍａｔｉｃａｌｍｏｄｅｌｓｏｆｗａｔｅｒｆｌｏｗｉｎｈｙｄｒａｕｌｉｃｅｎｇｉｎｅｅｒｉｎｇ，ｔｈｅａｒｅ…     

DILUTION OF HORIZONTAL RADIAL JET IN A CURRENT

A type of port with a movable cover is designed to increase initial dilution andprevent sea water and sediments from intruding into outfall systems.Horizontal radial jets pro-duced by this type of port in a current are investigated experimentally and theoretically.Theanalysis based on Reynolds'equations and self-similarity hypothesis shows that the maximum ve-locity of radial jets decays with r~(-1.5).The relationships between the width,thickness,average di-lution of a submerged wastefield along flow,and the parameters of the port,jet and ambient areestablished quantitatively and verified by experiments.It is demonstrated that the dilution ofhorizontal radial jets is much higher than that of vertical round jets and the surface boil point ofthe former is much more distant than that of the latter.     

EFFECT OF SUSPENDED PARTICLE ON STABILITY OF INTERFACE OF MOVING TWO-PHASE JET

ＮＯＭＥＮＣＬＡＴＵＲＥαｓｐａｒｔｉｃｌｅｖｏｌｕｍｅｆｒａｃｔｉｏｎｕｇｉｎｓｔａｎｔａｎｅｏｕｓｇａｓｖｅｌｏｃｉｔｙｖｅｃｔｏｒｕｓｉｎｓｔａｎｔａｎｅｏｕｓｐａｒｔｉｃｌｅｖｅｌｏｃｉｔｙｖｅｃｔｏｒＵｍｅａｎａｘｉａｌｖｅｌｏｃｉｔｙｏｆ...     

THE EFFECT OF RECLAMATION IN AREAS BETWEEN ISLANDS IN A COMPLEX TIDAL ESTUARY ON THE HYDRODYNAMIC SEDIMENT ENVIRONMENT

The Oujiang Estuary is a very complex tidal estuary with many islands, which is located in Zhejiang Province, China. Reclamation of areas between islands will create a great amount of land. In this article, the feasibility of reclamation of areas between Lingkun Island and Niyu is studied from the angle of its impacts on the hydrodynamic sediment environment. First, the natural hydrodynamic and sediment conditions and the seabed evolution are analyzed according to in-situ data. Second, numerical models of tidal current and sediment movement under the combined action of wave and current are set up with irregular triangular grid to carry out numerical simulations. The following conclusions are drawn from the study. (1) The areas between Linkun Island and Niyu are not a tidal passage. Wenzhou Shoal has been aggraded gradually, a condition favorable for reclamation. (2) The reclamation is feasible as far as its effect on surrounding hydrodynamic sediment environment is concerned. (3) The reclamation has great favorable socio-economic impacts.     

NUMERICAL SIMULATION OF LAMINAR SQUARE IMPINGING JET FLOWS

A theoretical study has been undertaken to determine the flow characteristics associated with a three-dimensional laminar impinging jet issuing from a square pipe nozzle. Interesting flow structures around the jet are detected. The numerical result reveals the existence of four streamwise velocity off-center peaks near the impingement plate, which is different from the rectangular jet impingement. The mechanism of the formation of the off-center velocity peaks and the parameters affecting the flow-field characteristics are discussed by comparison of the computed results with different nozzle-to-plate spacings and Reynolds numbers.     

NUMERICAL SIMULATION OF A HORIZONTAL MOMENTUM JET IN CROSS-FLOW

1. INTRODUCTIONWhen a momentumjet is issuing vertically orhorizontally into a steady ambient cross-flow, amomentumjet in cross-flowis formed as shown inFig .1 .The phenomena canfrequently foundin na-ture ,as well as inindustrial projects .Examples in-clud…     

THEORETICAL AND EXPERIMENTAL STUDY ON THE CONICAL SWIRLING WATER JET FLOW

This paper is concerned with theoretical and experimental study on theconical swirling water jet flow.Based upon the theoretical analysis,the experiment on thestructural characteristics of swirling water jet flow including the velocity and pressure dis-tribution laws,on which the parameters of the jet,nozzle and directional blades havemore or less influence,was carried out in CSSRC by using a 3-D LDV in order to optimizea new high-efficiency jet instead of swirling drilling bit for rock-breaking and continuouslydrilling,and to meet the demand of radial horizontal drilling technology.Meanwhile basedon the experimental results,the numerical simulation was conducted for the conicalswirling water jet in the immersed well-bottom flow by solving the RANS equations in the3-D body-fitted coordinate system with the k-ε turbulence model.The numerical resultsare consistent with the experimental data,and lead to some conclusions which are impor-tant for applying the conical swirling water jet to the petroleum drill     

NUMERICAL SIMULATION OF THE EFFECTS OF WEIGHT SYSTEM ON THE HYDRODYNAMIC BEHAVIOR OF 3-D NET OF GRAVITY CAGE IN CURRENT

In this article, a model of 3-D net is set up by using lumped mass method. Model test results made by Lader and Enerhaug are cited to verify the numerical model. The aim of this paper is to investigate the effects of weight system on the hydrodynamic behavior of 3-D net of gravity cage in current. Using the 3-D net model, with different styles and masses of weight system, hydrodynamic behavior of gravity cage net in current is simulated. In this article, two styles of common weight system are used, which include: (1) sinker system , (2) bottom collar-sinker system. Under each style, three different masses of weight system are adopted. The numerical results indicate that the bottom collar-sinker system is practically feasible in improving the cage net volume deformation. Results of this study will give references for better knowledge of hydrodynamic behavior of gravity cage.     

LARGE EDDY SIMULATION OF THE INTERACTION BETWEEN WALL JET AND OFFSET JET

The interaction between a plane wall jet and a parallel offset jet is studied through the Large Eddy Simulation (LES).In order to compare with the related experimental data,the offset ratio is set to be 1.0 and the Reynolds number Re is 1.0×10 4 with respect to the jet height L and the exit velocity 0 U.The Finite Volume Method (FVM) with orthogonal-mesh (6.17×10 6 nodes) is used to discretize governing equations.The large eddies are obtained directly,while the small eddies are simulated by using the Dynamic Smagorinsky-Lily Model (DSLM) and the Dynamic Kinetic energy Subgrid-scale Model (DKSM).Comparisons between computational results and experimental data show that the DKSM is especially effective in predicting the mean stream-wise velocity,the half-width of the velocity and the decay of the maximum velocity.The variations of the mean stream-wise velocity and the turbulent intensity at several positions are also obtained,and their distributions agree well with the measurements.The further analysis of dilute characteristics focuses on the tracer concentration,such as the distributions of the concentration (i.e.,0 C /C or /m C C),the boundary layer thickness δ c and the half-width of the concentration c b,the decay of the maximum concentration (0 /m C C) along the downstream direction.The turbulence mechanism is also analyzed in some aspects,such as the coherent structure,the correlation function and the Probability Density Function (PDF) of the fluctuating velocity.The results show that the interaction between the two jets is strong near the jet exit and they are fully merged after a certain distance.     

EFFECT OF ENLARGED FREE JET ON ENERGY CONVERSION IN PELTON TURBINE

NOMENCLATURE Q —flow rate H— head Dref —diameter of pitch circle B —inner width of bucket ω —angular speed of runner QDH —unit discharge Sn —needle strokesn—relative needle stroke Dinj —diameter of injector inlet Dt —diameter of nozzle throat D     

FLOW CHARACTERISTICS OF TURBULENT JETS INJECTED OBLIQUELY IN CROSSFLOW

1 .　INTRODUCTIONThejetinacrossflowisahighlycomplexturbu lentflow ,andwithapplicationsinvariousengineeringfields .Theinjectionofajetintothecrossflowcanaltertheflowfieldandresultinaverycomplexthree di mensionalflowstructure .Numericalsimulationisanimportantmethodtostudythetransversejet cross flow .Chang[1] ,Tamamidis[2 ] ,Lakehal[3] etc .,usedthenormalk εmodelandwallfunctionmethodtosim ulatetheflowfieldoftheturbulentjet .Althoughthenormalk εmodelgivespredictionsofengineeringaccu racyint…     

FINITE ELEMENT NUMERICAL SIMULATION FOR THE HYDRODYNAMIC FIELD EVOLUTION OF GEOTHERMAL WATER IN THE NANWENQUAN ANTICLINE IN CHONGQING IN CHINA

1. INTRODUCTION The Nanwenquan anticline is the drape storing geothermal water. The anticline extends from north to south in Chongqing, the Nanwenquan and Xiaoquan in the middle of the anticline [1]. The two hot springs, and geothermal water in the other …     

THREE-DIMENSIONAL MEAN AND TURBULENCE CHARACTERISTICS OF AN IMPINGING DENSITY JET IN A CONFINED CROSSFLOW IN NEAR FIELD

The three-dimensional mean and turbulence characteristics of an impinging density jet in a confined crossflow were numerically investigated using the RNG turbulence model. The comparison of the subregion structures and gross features between the numerical results and the experimental data show good agreement. The velocity, Turbulent Kinetic Energy (TKE) and concentration distributions of the impinging jet in near field were obtained and analyzed. The results indicate that the flow and concentration fields of the impinging jet in the crossflow exhibit distinguished three-dimensionality in the near field. There exist upstream wall vortices and downstream wall jet zones in the impinging region, and the TKE and concentration decays are asymmetrical in relation to the stagnation point. The lateral concentration distributionrange in the impinging region spreads considerably. The enhanced entrainment and mixing of the impinging jet in the confined crossflow are mostly associated with the impinging action and lateral expansion in the impinging region. The presence of the bottom wall restrains the formation of the spanwise rollers in the transverse jet region and vertical entrainment and mixing in the impinging region and the transition region.