Study And Analysis Of A Certain Vehicle Cooling System

Cooling system is an important part of engine, automobile engine cabin is asemi-enclosed space and has high special requirements of the temperature field. On one handthere are various materials in the cabin,such as rubber parts, wiring harness on temperatureof certain requirements; on the other hand the engine itself requires proper heat dissipation,that make sure the various operating conditions has the optimal power and economy. Withrapid the increasing in speed and power of engine, require high performance of the coolingsystem increasingly, so the engine cooling system design and research also more and moredeeply and also the the research methods are various. The research of the cooling parts arececoming more mature and for OEMs these work are always completed by the supplier.However, the system-level development in our country is not yet mature, especially foranalysis of the flow field and the cooling match is still in the stage of development. Based onthis, the matching of the engine cooling system has been a subject of concern by the OEMs.The purpose of this study is to re-match a cooling system of a vehicle which JianglingMotors introduced from European. This vehicle is a long-wheelbase17, due to regionaldifferences, this commercial vehicle in Europe’s main purpose is to transport goods but inChina’s main purpose to carry passengers, so the air conditioning performance in a vehicledefine need to improve the requirements. In order to meet the vehicle idling and low-speedair-conditioning performance and thus improve vehicle comfortableness, based onexperience the preliminary concept is like this: to change the cooling fan from the originalmodels to electronic fan way. The advantage of electronic fan is greatly improving thevehicle idling and low-speed air-conditioning performance and greatly reduce the engineload, also do good to vehicle power and economy; drawback is the maximum amount ofwind is lower than the mechanical fan and cooling system may not meet the coolingrequirements which requires re-match on the radiator. Due to the optimization of the airconditioning system itself will change the condenser in the front-end module, and thus thepressure map characteristics of the condenser changes and also the system will have someimpact. Based on the above changes require re-selection and matching the entire coolingsystem. The following research methods are used in the cooling system matches:(1) study the design principles of the original models and the performance of keycomponents. First need to obtain the performance curve of original water pumps, radiator,condenser and fan, and also the coolant flow of original cooling system. All of these can bemeasured through the vehicle test and parts bench experiments. Then analysis the layout ofthe cooling system and experimental data, based on the use of RAM curve of the originalmodels, calculate the heat capacity of the cooling system in the vehicle when idling is31KW,the maximum torque point is48KW, the maximum power point, radiator cooling capacity is71KW. All these results can be used as a basis and reference of the re-mach of coolingsystem t.(2) Based on the original model data, and also combined with the use of the domesticmarket and vehicle air-conditioning property, we can define the the target of heat dissipationand air flow target of the re-matched cooling system. Without increasing the trailer in thedomestic market requirements, heat dissipation can be appropriately reduced, but the idle airflow required to substantially improve in order to improve the performance of airconditioning. Radiator and fan need to re-design baced on the requirement.As the originalmodel of the engine compartment and the inlet channel has not changed, we can use theRAM curve of the original models to complete the mach of radiator, condenser, electronicfan. The calculated results show that the re-match electronic fans can provide air flowthrough the cooling module increased from2.56m/s to3.2m/s, so that the air conditioningperformance have been greatly improved;30Km/h and70km/h when the wind speed ofthe cooling module were3.51m/s and4.12m/s, which compared with the original modelsdecreased, but the radiator performance improvement can make up for the decline of the airflow. The cooling capacity of the re-matched radiator in the maximum torque and powerpoint for47kw and64kw which are all higher than10%of the water jacket heat dissipationand heat transfer in the torque point is nearly as the original models.(3) the use of CFD fluid analysis is used as a complete-aided design, combined with therequirements of the engineering and attribute goals, input the Conditions and constraints intothe boundary conditions for analysis, and output the results to analyze and judge. The CFDanalysis results show that the cooling system in the idle air flow through the cooling systemis3.46m/s, in30Km/h and70km/h air speed through the cooling module were3.84m,/sand4.5m/s, the results are better than the RAM calculations, and the result is the differencein less than10%. By the result the re-matched system judged less risky and can be implemented in the vehicle.(4) Use the wind tunnel experiments, the road assessment experiments to verify theoptimization design of automotive engine cooling system in a variety of working conditions.Experiment settings to43°C ambient temperature, vehicle full load, select six conditions asthe highest speed, the common conditions and the worst conditions to verify, in allconditions, the engine water temperature does not exceed110°C, the engine oil temperaturedoes not exceed140℃, the engine compartment temperature to meet the designrequirements, vehicle power no decline. In particular, the air flow in idling condition wassignificantly greater than the original vehicle, which ensuring the air conditioning systemperformance has been improved. The test results show that: the re-matched design of thecooling system meets the design requirements.In this paper combined the method of theory and practice, also the bench test, RAMcurve, CFD analysis has been used to re-match the cooling system, wind tunnel experimentsand road tests are used on the cooling system verification, the final experimental resultsshow that in any harsh environments with complex conditions, the cooling system can meetthe requirements of engine cooling and air-conditioning properties. Due to the application ofCFD and RAM curve matching accuracy greatly increased to avoid repeated verification andoptimization, and for the development of the project saving a lot of development costs andshorten the time cycle. Also timely joined the cooling system development model describesthe theory of the cooling system matching, the use of RAM curve, the CFD model tosimplify, the bench test method, wind tunnel experiments and road test methods andconditions set. these methods integrated applied in practical work will show experience ofsuccessful use to the future work of the systems and components analysis and matching. andalso shows a reference for other OEMs in the cooling system matches.The vehicle has been appeared on the market in the August2010,during the summerhigh temperature environment, verify the efficiency of the cooling system is fully and theair-conditioned superior performance is prominent, the customer satisfaction is very high,the company won the good economic and social benefits.