| With the increasingly strictness of national energy saving requirements and thedevelopment of high-power engine, the heat balance problem of loaders is getting more andmore attention. Cooling module with excellent performance can make the loader system workwithin the optimal temperature range, which has great significance for the improvement ofloader reliability, fuel economy and reduction of loader emissions. Cooling fan drivetechnology plays an important role in heat balance control of loader, which constantlypromotes the development of heat balance technology. With National Science and TechnologySupport Programme Project " Energy-saving and safety-oriented, integrated engineeringmachinery and equipment research and development"(project number:2013BAF07B04), thispaper researched a domestic50type wheel loaders cooling fan. Drive characteristics, fixedquantity drive as well as variable quantity drive of cooling fan were discussed. Hydraulicdrive of cooling fan which was applied on wheel loader was studied.Firstly, based on the method of with the application of C++languageprogram, heat dissipation characteristic and resistance characteristic of liquid cooling radiator,transmission oil radiator as well as hydraulic oil radiator which changing with environmenttemperature and cooling-air flow rate were obtained. Fitting formulas of calculating relationsof cooling fan were determined by using cooling fan test data on the basis of similarity law.The relationship between fan rotation speed and environment temperature when cooling fanmatches with radiator reasonably in the wheel loader cooling module was deduced.Furthermore, drive characteristics of cooling fan which changing with environmenttemperature including rotation speed, static pressure, moment as well as shaft power wasdetermined.Secondly, hydraulic drive of cooling fan was studied from two aspects including fixedquantity system and variable quantity system. Referring to the development of speed adjustingtechnology of cooling fan in engineering machinery, the work principle of hydraulic wasdetermined and analyzed. In fixed quantity system, fan rotation speed was controlled bythrottling adjusting of electro-hydraulic proportional relief valve, while in variable quantitysystem, fan rotation speed was controlled by volume speed adjusting of electro-hydraulicproportional constant pressure pump. Parameters of key hydraulic components werecalculated and types of key hydraulic components were determined. For fixed quantity system of hydraulic drive of cooling fan, HCD simulation model was established in AMEsimsoftware after the work principle of electro-hydraulic proportional relief valve was analyzed,the static characteristics of system were studied and simulation parameters were determined,after that, the dynamic characteristics of system were analyzed under two extreme workingconditions, effects of pilot valve half cone angle, main orifice diameter, pilot valve seat holediameter of electro-hydraulic proportional relief valve on performance of fixed quantitysystem were analyzed. Based on the analyzing of work principle of constant pressure variablepump with electro-hydraulic proportional constant pressure pump, the simulation model ofpump-controlling system of cooling fan which consists of variable pump and fixed quantitymotor was established. Combining with static characteristics and available researchachievements, the simulation parameters were determined. The dynamic characteristics undertwo extreme working conditions were obtained. Mechanical drive, hydraulic fixed quantitydrive and variable quantity drive were compared from the point of energy consumption. Inputpower, using ratio of cooling fan power and fuel consumption of system was obtained.Furthermore, the drive system of wheel loader cooling pan was improved into hydraulicdrive. Based on analyzing of work principle of hydraulic system and mechano-fluid couplingsimulation, the dynamic simulation of working device was established and the workingresistance force was predicted. Mechano-fluid coupling simulation model of working devicewas established by using AMESim software. According to the technology parameters ofworking device, boundary conditions were setup, working performance and energyconsumption of working device were analyzed.To sum up, the reasonable matching of cooling pan rotation speed and radiator demandsfor the continuously variable adjusting of cooling pan rotation speed. The research results inthis paper has great reference value and guiding significance for domestic50type wheelloader improving drive system from mechanical drive into hydraulic drive. The researchmethods also can be applied in other engineering machinery. |
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