The Study On The Efficiency Of An Eight-axles All Terrain Crane Cooling System

As mobile cranes developing towards large-scale, comfortable operation,high security, energy conservation and environmental protection, vehiclecooling system not only meets the increasing demand of vehicle dynamicsystem heat dissipation, but also components heat dissipation in vehicletransmission system, such as hydraulic torque converter, hydraulic retarder.Due to the different functions of the heating elements, their hot nodes are notsynchronous. So, vehicle cooling demand varies widely in different workingcondition. Under normal circumstances, the cooling system which satisfies enginedissipating heat in extreme working condition only runs perfectly in3%—5%ofits working time. The heat sinking capacity of the compound cooling system, whichgives consideration to hydraulic torque converter and retarder, is often higherthan the cooling demand of engine dissipating heat in extreme working condition.It further reduces the effective utilization of the system, and substantiallyincreases the power consumption of the cooling fan. In order to improve thecooling system utilization, making it can not only satisfy the demand of vehicleradiator under different operating conditions, but also avoid invalid of theengine power loss, this paper presents a study on improvement of cooling systemefficiency by using engine coolant temperature to control cooling fan.In order to reduce energy consumption of cooling system, a type of all terraincranes of this study weakens the extreme working environment that needs greatheat dissipation when matching system together, and at the same time, the workingcondition of the cooling fan is only associated with engine work status, withoutconsidering the actual vehicle cooling requirements. In actual use of vehicles,often in the high temperature weather or continuous long climbing, engine inletair temperature is high, and coolant temperature stays for a long time near the engine high temperature limit. Obviously, the cooling system does not fully meetthe cooling needs of the vehicle. To solve this problem, this paper proposesan optimizing scheme of re-matching radiator, based on controlling cooling fanaccording to heat dissipation. And the system simulation is performed bycomputational fluid dynamics (CFD).The main contents and results of this paper are as follows:In this paper, the performance of the design principles of the originalcooling system and all major components were analyzed. Combined with the actualuse of the vehicle condition, sorting out the vehicle cooling requirements undertypical driving conditions,420kW of water heat dissipation and79kW of chargeair cooling demand in vehicle extreme working conditions are used as theessential data for system change.Based on spatial arrangement of original cooling system, taking into accountthe requirements of serialization and generalization of the main components,and determining the dimension of charge air intercooler (referred to as“cooler”) and water cooler, demand for cooling medium under the extreme workingcondition, the appropriate fan speed is calculated, and fan control strategyand control objectives are proposed. A proportional relief valve is set in fandriving system. There is a positive correlation between fan speed and enginespeed. When engine speed is between700r/min～1800r/min, cooler side fanspeed can be up to1800r/min. When the cooling temperature is greater than orequal to98℃，the fan speed will be increased to2200r/min, while the coolanttemperature drops equal to or lesser than96℃, the maximum fan speed lowersto1800r/min, and is related to the engine speed. Water cooler fan will startuntil the coolant temperature is greater than or equal to96℃, and fan speedwill steady increase to1800r/min by controlling the output of the proportionalvalve. When the coolant temperature increase greater than or equal to98℃,the fan speed will increase to2200r/min. If the cooling fluid temperature dropsequal to or lesser than88℃, the fan will be turned off. The cooling system model is built. Taking into account the radiatorarrangement and layout of space without making changes, and the external radiatorcoolant flow and vehicle speed is less relevant, we use FLUENT software, combinedwith the fan performance at1800r/min,2200r/min simulated by the multiplereference Frame (referred to MRF), to simulate the external radiator coolantflow field, in order to prove the improved system can meet the designrequirements.According to relevant State regulations, pertinent testing schemes aredesigned to verify the actual performance of the improved system. Start theengine and adjust the pressure of electro-hydraulic proportional relief valvewhen the vehicle is stationary, measure air flow inlet side, temperature andfan speed of the radiator, then the rationality of the hydraulic system pressuresetting is tested. Whether the cooling system can meet the cooling needs of theengine under load limit inspects by the engine cooling test. Reliabilityexperiments of vehicle running10000km long distances tests reliability of thevehicle cooling system in different working condition and using environment,measures energy consumption data of the fan system, and verifies the correctnessof fan control system strategy.