Design Of Key Units Equipped On Rapid Fire Fighting Vehicle Of Airport

With the development of the aviation industry in our country, the number of the airport is gradually increasing, leading to a high demand of airport rapid fire fighting vehicle, as well as the requirements of its performance and reliability. At present, foreign key design technologies have been blockaded for the airport fire truck, therefore, our country still need import a large number of advanced airport fire trucks each year. Therefore, the production of highly reliable airport rapid mobilized fire engines meets the demand of the market.A special vehicle company is preparing to manufacture a model of airport rapid mobilized fire truck in order to meet the market demand. Based on this particular model, this paper is to analyse, redesign and manufacture the upper main structure of the vehicle. Afterwards, the units performance were tested according to national standards, and rectified according to the experimental data, finally realising the shape of the vehicle.In this paper, the redesigned units included capacity tank, subframe and hydraulic system (pipeline system). The basic technical parameters of the refined vehicle were calculated as well. An inner-hidden rectangular shaped tank was applied. Partitions were introduced in the inner part of the tank. Matts-shaped antiroulis were equipped, as well as vent pipes for the prevention of overflow. A base was located at the tank bottom and connected with subframe. The capacity of the tank was designed to be 5000 L, including 4600 L of water and 400 L of class B foam. The tank was welded into a unified whole with high quality stainless steel plates (0Cr18Ni9). A static pressure test was carried out after the completion of the welding to check whether there is leakage of the tank.To prevent the stress concentration on the main frame and let loading pressure uniformly distribute on the longitudinal beam, a subframe was utilized between the upper part and the main frame. This particular subframe of the airport rapid fire fighting vehicle is mainly carrying the weight of capacity tank, engine room, pump room, and related parts of transmission mechanism, and withstand all kinds of force and moment, and its use environment and stress condition is complicated. It belongs to the main load bearing parts, therefore, its safety and integrity has to be ensured in the process of transportation, installation and use, indicating, on the other hand its importance to the safety. As for the material, Q235 plain carbon structural steel was chosen for the subframe, which was joined with upper part by a flexible connection. To ensure the high reliability, subframe undergoes finite element analysis of statics and dynamics using AN SYS after the completion of shape design.Pipeline system (hydraulic system) is the main working unit during fire extinguishing. The main liquid outlet has a rated flow roof gun of 60 L/S (1 MPa), and a rated flow front gun of 30L/S (1.0 MPa). Meanwhile, because extinguishing fire fighting foam liquid has certain corrosion resistance, the materials should be stainless steel pipe when manufacturing the lines, and each pipeline should be linked with stainless steel flanges, while a flexible rubber joint connection should be used in line with capacity tank joint.The overall layout of upper main units are the prepositive pump room, mid-capacity tank, and postpositive rear pair engine case. Each units are separated by carriages skeletons, and the aluminum plates are gummed out of the skeleton after the skeleton is well welded. These measures can ensure the upper structures are not exposed in the outer space, and convenient to add the vehicle exteriors. The carriage skeleton basically undergoes no load, but the self-weight of skeleton is loaded on the subframe by welding the embedded plate, and the skeleton can achieve flexible links with subframe by elastic support. During the design of the upper main structure, the effect of adding the upper structure to the basic technical parameters of the vehicle should be considered. For example, the vehicle mass center should not be too high, the lateral and vergens stabilities should meet the design requirements, and the front axle shaft should be distributed reasonably.