Study On Optimal Design Of The Key Device Of Nozzles Used For Improving Production Of Gas

With the natural Gas was exploited , production rate of most of gas wells is decreased . It is one of the most important problem that how to increase gas production by Remolding the old gas wells . The effection is poor by traditional methods that acidification and fracturing in the gas wells that low-prmeability ,polluted seriously , absorbing water difficulty , or the profiles that absorb water are uneven . Research shows that it is better effect by the water jet method . Nozzles are the key component as the water jet device , and usually are worn seriously by abrasive particles . The problem that how to design nozzle in some special conditions is very important for the water jet technology.Supported by Innovation Groups Fund Project"Theory of rock cracking by High-pressure water jet and its basic application research in underground engineering (ID: 50621403)"of National Natural Science Foundation , this thesis proposes a new method of designing and researching nozzles in special condition. Develop the criterion of design nozzle in special condition based on the actual designing and researching of nozzles that used in industry ; It is expounded about designing nozzle in theory ; By the CFD method , the relation that between nozzle's structure parameters and the nozzle's performance; The paper presents a novel method that researching water jet performance by testing reynolds stress field and viscous stress field ; the performance of nozzles are tested by eroding the rock .The main conclusion are as follows :1. It is expounded about designing nozzle , containing nozzle's material , internal structure , diameter d , inlet's conical angle , the long of outlet's cylindrical section h , outside diameter D , total length H , roughness . By the CFD method , the relation that between nozzle's structure parameters and the nozzle's performance. The results shown that the long of outlet's cylindrical section have a greater influence on nozzle function than the ignition terms inlet's conical angle , and the nozzle that inlet's conical angle is 30°and the outlet's cylindrical section length is 10mm function is best.2. The paper presents a novel method that researching water jet performance by testing reynolds stress field and viscous stress field . The results shown that the erage velocity increases first and then reduces with the he long of outlet's cylindrical section and inlet's conical angle increase , and the nozzle's that inlet's conical angle is 30°and the outlet's cylindrical section length is 10mm function is best . Because its erage velocity which is 106.29m/s is highest , the viscous stress of axle center is smaller then others and value of reynolds stress field is almost the same .3. The experiment done in the laboratory on the erosion of sandstone indicated that under the same experimental conditions, the flow coefficient of the nozzle that inlet's conical angle is 30°and the outlet's cylindrical section length is 10mm function is the maximal and had the higher capacity utilization; and this nozzle under the same conditions of 10% abrasive concentration, erodes the rock that compressive strength as 500 Mpa and for the elastic modulus of sandstone in 6.17 Gpa deeply (925mm). Finally the optimized nozzle parameters are: the intake contraction angle is 30 degrees, the length of columned exit is 10 mm. The terse conclusion is that the intake contraction angle is 30 degrees, the length of columned exit is 10 mm.