The Theory And Experiment Research On The Flow Field Of The Air-water Coaxial Nozzle Used In The High-pressure Jet Grouting

The water jet which is protected by the air is become more and more important and has been widely used in high-pressure jetting ,drilling engineering,washing and cleaning business.Many aspects of the air-water nozzle are very important for the Engineering effect and benefits, such as the optimizations of the air-water coaxial nozzle structures,the regulations of the flow fields which are in different submerged environment,the inner mechanism of how the gas protect water jet to improve the jet ability etc.The purpose of this article is to take the air-water coaxial nozzle in the high pressure jet grouting as a model, respectively analyzing the water jetting with or without the gas protecting circumstances ,and water jetting in different environments,such as water, sandy soil etc, through the methods of using the CFD software to make the numerical simulation,testing in the lab , and later excavation detection in the site to research the laws of the air-water coaxial nozzle how to affect the diameter of the pile, so as to provide the scientific basis for designing the reasonable structures and suitable parameters of the air-water coaxial nozzles. The key work performed in this paper are as follows:Firstly. Analyzing the air-water coaxial nozzle structure parameters and jetting characteristics in the high pressure jet grouting .The euler method is used to establish the internal flow field of the mathematical model for the air-water coaxial nozzle, and the standard two-phase k ?εturbulent model is adopted to simulate the two phase flow field. Selecting the classic water flow structure, with standards of the gas loops can better protecting the water jet and the water jet has less disturbance, making the optimization analysis of the thickness of the water nozzle and gas flow structures .Secondly.Taking the optimal selection of water coaxial nozzle structure as the analysis object for the numerical simulation. Analyzing the flow field rules of the speed,dynamic pressure parameters of each phase ,finding the changes of the phases in the radial profiles situated in different flow positions and flow profiles situated in different radial positions, studying the regulations respectively in the situations of with and without the gas protectiong across the water jet . Revealing the relationship of the water jet decay rate .Thirdly. Designing and manufacturing the devices used in the transparent water tank for the flow showing, demonstrating the jet flow respectively with and without a gas ring protecting the water jet,in the air and underwater for the jet flow qualitative research.Fouthly. Through the core, excavation pile subjects,connecting sections inspections,mechanics and water pressure test etc in the site,all the prooves proved that the pile diameter size consistent with jetting distance or the declay rate of the flow pressure .In the pile cross section, the particles size distribution state exist the corresponding regulations with the jetting submerged environment and the jetting distance from the nozzle.Fifth. According to the numerical simulation and the pile effect analysis, make the improvements about the early pile diameter empirical equation , which has been taken into account the air-water coaxial nozzle structure parameters and the injection parameters aspects, then the pile diameter empirical equation has been verified with the pile inspection in the site.