| Roads covered with ice seriously threat to the traffic. Countries which are at highlatitudes and located in the plateau have been committed to the study of de-icing,especially for some important facilities, such as highways, bridges, airport runwaysand so on. In northern China, in late autumn and early winter or in late winter andearly spring there is always the freezing rain which can easily cause road icing. In thesouth especially the southwest, freezing rain is also a very common weather. Aroundthe Spring Festival of2008and2010，the cold weather caused a large number ofroads interrupted, airport closure and rail outage,and then leaded to large quantitiesof supplies and passengers stranded. Therefore timely removal of the ice covered onthe road has an important significance for recovering the traffic.Transportation is not only the lifeblood of the national economy, but also apowerful guarantee of the national security. As china’s economy continues to developin recent years, the transportation industry has made great progress. More and morepeople tend to travel by air, the number of airports is increasing quickly. The icing onthe airport runways make the runways’ coefficient of friction greatly reduce, whichadversely affects the taking off and landing of aircrafts, which is directly related tothe personal safety of passengers. So the ability to quickly clear the ice on airportrunways is important to ensure both passengers’ safety and our national defense.The traditional manual de-icing method needs a lot of human and material resources,and it has very low efficiency. Although the mechanical de-icing method has lightpollution and high efficiency, but it can’t effectively clear the thin ice on therunways(Ice thickness less than3mm). We mainly use the method which includechemical de-icing and thermal de-icing to clean the thin ice. Chemical de-icingmethod is currently widely used in airport runway de-icing. But it will cause heavypollution to underground environment by using chemical deicers. As a result, othermethods are needed to replace chemical de-icing. In this case, the thermal de-icingmethod has developed a lot. How to improve the speed and efficacy of thermalde-icing is the key point to popularize this method in airport runways.De-icing vehicles converted by turbojet-5engine are in a certain used in someairports. By doing research on mechanism and working speed of the turbojet vehicle, its working efficacy is hoped to be improved. The main research work andconclusions are as follows:(1) Build the physical model of turbojet de-icing vehicles. By calculating theflow field of the high-speed and high-temperature gas flow with CFD method, thevelocity and temperature distributions of the flow field are obtained. Through analysisof the distributions, we know that the diffusion of the temperature field depend on thediffusion of the velocity field. Then combined with the thermodynamic knowledge, itis determined that the main failure modes of the ice is melting.(2) When the ice melts into water, it will be broken into small dropletsin high-speed gas flow field and the movement of water particles in high-speed gas isstudied. The velocity and travel time of water particles in the flow field depend on thehorizontal axis of the x direction of the nozzle velocity. The larger the turbulentkinetic energy is on the x axis, the faster the velocity of diffusion of the particles andthe flow field is. Compared2D with3D state of the particles’ movement, theexistence of a lot of water particles make the speed proliferation move to the verticalaxis of the z direction which don’t conducive to the heat exchangebetween the gas and ice. The greater the velocity on the horizontal axis of the xdirection is, the more easier for water particles flying out of the computationaldomain.(3) The distribution under various incident angles of the flow field is calculatedusing CFD methods. Comparing field distribution and temperature distribution underdifferent incident angles and combined with distribution of the convective heatexchange coefficient on the ground, following conclusions can be obtained: With theincrease of the incident angle, the coefficient of the convective heat exchangebetween the gas and ice increases. The contact area between the gas and ice alsoincrease. The heat exchange coefficient and the contact area depend on the meltingrate of the ice. But the increase of the incident angle will make the horizontal velocitydecrease, which is not conducive to the discharge of the water particles. At the sametime, the increase of incident angle will lead to gas reflux and bring harm to de-icingvehicles’ safe operation. We found that the best incident angle of de-icing vehicles is20°in the quantify angle. The de-icing vehicles’ operating speed is determined to be2.83km h-1using state parameters of the gas and the ice surface under the best incident angle. |
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