Numerical Investigation Of Enchancing Heat Transfer In Belt-type Resistance Heater Of Hypersonic Wind Tunnel

As an important support for comprehensive national strength,the hypersonic technology is the technique field that countries race to develop in recently years.Ground tests,one of the three means of hypersonic aerodynamics research,is the main source of aircrafts' aerodynamic data.Evolved from the basis of the supersonic wind tunnel,the hypersonic wind tunnel enjoys similar principles with it,except that the experiment gas of the hypersonic wind tunnel should be heated to prevent gas' s condensation.Heater,which used to heat gas before settling chamber in the hypersonic wind tunnel,divided into continuous heater and storage heater according to different types of heating the experiment gas.Five chapters is included in this paper,and the main content of each section are as follows:hypersonic wind tunnel and its heating technique is discussed in the introduction.The general situation of heater used in the hypersonic wind tunnel both at home and abroad is also summarized.In Chapter 2,the numerical simulation method used in this thesis is referred.After introduced the macroscopic idea,the equations of flow and heat transfer problems are represented.Particularly,the scheme used in pressure-velocity coupling,k-? and RNG k-? turbulence model,and the Enhanced Wall Treatment method are provided.Chapter 3 mainly talk about the numerical computation of the inner field of belttype resistance heater.This research set the?0.5m hypersonic wind tunnel's belt-type resistance heater,in China Aerodynamics Research and Development Center(CARDC),as the prototype,and built three-dimensional model after making some simplification on the archetype.The inner flow-field and heat exchange characteristics,including distributions of temperature,pressure,density and velocity,are investigated.The simulation method proved workable by comparing the result of numerical calculation with the experimental data from heater of ?0.5m wind tunnel under four states(M5,P=1MPa;M5,P=2MPa;M6,P=2MPa;M6,P=5MPa),and on the basis of which,the flow-field's variation laws along with different entrance parameters,consisting of flow rate,pressure and temperature,are introduced.Then,research of improvement of overall performance of heater for wind tunnels is carried out in Chapter 4,based on the research of heat exchangers used in industry field for the similarity between the two.Three different means to increase heat transfer rate are investigated on the two dimensional model in which can reflect major features and the influences of each method are discussed.The device of belt of staggered is selected after Comprehensive evaluation of the three approaches.Three dimensional model of heater with staggered belt is established because the two dimensional model cannot simulate flow in radial direction.Four state are calculated and on one hand,it's consequence match well with two dimensional simulations,on the other hand,the result shows staggered belt arrangement is indeed have better overall performance than the standard model.The last part concluded the work in this thesis,and the research direction for next stage is discussed.