Development Of Simulation Test-bed Of Engine Compartment

Engine compartment and cooling system are important components of the vehicle. Along with the unceasing enhancements of power and the requirements of energy-saving and emission-reduction, the design requirements of engine compartment and cooling system are also getting higher and higher. Therefore, researches on flow and heat transfer of engine compartment and cooling system are becoming more important, which are mainly divided into simulation methods and experimental studies currently. Numerical simulations have many advantages, such as preliminary researches, widespread conditions, low costs, short cycle and others, but they are limited by the boundary conditions and precision of models. Experimental studies on flow and heat transfer for the cooling system are mainly divided into parts tests, modular tests, vehicle road tests. Parts and module tests cannot provide actual performance of parts, when they are working in systems. Vehicle road tests are the ultimate means of cooling system performance testing, but the financial and time costs are relatively high. Aiming at shortages above, this paper is devoting to designing a test-bed of engine compartment, which can simulate the working condition, thermal status, intakes and exhaust environment.The following are works and conclusions in this thesis:1. Overall design of test-bed. Tests of parts’performance could be complete by this test-bed, and also optimizations of parts and matching experiments. The test-bed was mainly composed of master control system, heat source simulation system, measuring flow rate system of cooling wind and data acquisition system. Heat source simulation system was responsible for the simulation of working conditions, and measuring flow rate system of cooling wind was responsible for the simulation of intake and exhaust environment, and completed the measurement of air flow rate2. Design of heat source simulation system. The system was composed of simulation heat source, constant temperature and flow system, hot oil circulating system. The double closed-loop control could make temperature fluctuations of the test medium remain within the range of±1℃, and could guarantee the stability of test flow rate.3. Design of measuring flow rate system of cooling wind. Major function of the system included:performance tests of radiators; simulated atmosphere environment and conducted the open experiments; after adding balance fan and forming loop system, could simulate the intake and exhaust environment, conducted the closed experiments. Multiple nozzles method with the accuracy of±1%was used for the measurement of air flow rate, and the range of air flow was decided by different combinations of nozzles. In order to simulate the intake and exhaust environment of non-wind cooling engine compartment actually, the pressure difference between intake and exhaust environment of engine compartment was requested to be0Pa, with accuracy of±2Pa.4. Data acquisition system and sensors. According to the properties and requirements of the main parameters, measuring methods and sensors were determined and calibrations of sensors were completed.5. Building, debugging and testing. Test-bed was built and debugged. When measuring flow rate closed system was being debugged, a phenomenon was found when there was no heat transfer on the liquid side, the cooling air’s temperature rose apparently. The analysis obtained that the air’s temperature rise was created by fan’s diffusion, so when did the calculation of thermal balance, fan’s diffusion must be taken into consideration. Based on this, thermal balance tests of one non-wind cooling engine compartment were carried out. The results indicated that the errors are1.97%～2.20%,so the best-bed met the requirement of application.