Study Of Wall Pressure Distribution Of Vertical Air Impinging Jet Of Round Nozzles

Impinging jet as an important technical tool,has been widely used in industrial areas such as Jet stripping,Jet dedusting.Wall pressure distribution is one of those critical feathers of these applications,which is worth being studied both in theoretical and practical aspects.Firstly,the flow field structure and wall static pressure distribution are studied by numerical simulation for three different structure of nozzles.SST k-? ?RNG k-? ? Realizable k-? and S-A totally four turbulent models are used in simulation.According to the simulated flow field structure and wall pressure,the study of wall pressure distribution is divided into two parts: subsonic and supersonic impinging jets.Secondly,the pneumatic circuit and test device are designed in detail.The 0.5mm static pressure hole and moving platform with 0.005 mm positioning accuracy are used considering the pressure measurement errors.By comparing the simulation and the experiment results,SST k-? is considered the most accurate turbulent model in calculating the wall pressure of impinging jet.Thirdly,this paper takes N1 nozzle for study first and analyzes the wall pressure distribution both in subsonic and supersonic impinging jets.In subsonic impinging conditions,the wall pressure distribution is Gaussian from experiments.Dimension analysis method is used and after introducing a new quantity called “half width of pressure distribution”,wall pressure distribution can be described by one equation for all conditions.Further,the half width and stagnation pressure distribution are described only by impinging parameters successfully.This equation is also used for N2 and N3 nozzles and the experiment results show that the equation is also suitable for N2 and N3 nozzles.In supersonic impinging conditions,the study is divided into moderately and highly under-expanded impinging jets.In moderately under-expanded impinging jet,the wall pressure distribution is basically Gaussian and the relation is the same as subsonic impinging jet,except some special distributions related to nozzle's structure.In highly under-expanded impinging jet,the reason of bimodal distribution is explained and the experiment results show that this kind of distribution occurs mostly in core jet zone.And a simple method is given to determine the occurrence of the bimodal distribution.Also,the distribution is fit for N2 and N3 nozzles well experimentally.Finally,orthogonal test method is used to determine the most influential factor for the stagnation pressure,and the nozzle diameter turns out to be the most influential one in all conditions.By comparing the axial velocity and stagnation pressure loss of three types of nozzles,it shows that N3 nozzle has the biggest pressure loss in subsonic impinging jets while N1 nozzle in supersonic ones.According to wall pressure distribution and stagnation pressure loss,N1 and N3 nozzle are expected to use in subsonic and supersonic impinging jets respectively.