Search Results

An Air intake system (AIS) is a duct system which leads the airflow going into the internal combustion engine. Combustion requires oxygen, and the more oxygen is provided into the combustion process the more power it will produce. The lower the air temperature, the higher its density, and hence there is more oxygen in a unit volume. The quality of air entering engine can be measured with the air temperature. AIS design and routing influence the air charge temperature (ACT) at intake manifold runners and ACT is normally measured at AIS throttle body in reality. Higher ACT lead to inefficient combustion and can lead to spark retard. Optimization of AIS designs and reduction of ACT can improve engine performance and vehicle fuel economy. High ACT can be a result of two different phenomena: Recirculation - Hot air from the underhood environment ingested into the dirty side of the air intake system.

Vehicle front end air flow management affects many aspects of vehicle aero/thermal performances. The HVAC system capacity is greatly driven by the airflow and the air temperature received at the condenser. In this paper, front end design practices are investigated using computer simulation and full vehicle test to evaluate their effects on AC system performance. A full vehicle 3D CFD model is developed and used to predict the airflow and temperature in underhood and around the vehicle body, and specifically the conditions entering the condenser. The condenser inlet airflow and temperature profiles from 3D CFD model are then used as inputs for the 1D AC system model. The 1D AC system model, which includes condenser, compressor, evaporator and TXV (Thermal eXpansion Valve), is developed to observe the critical AC performance indicators such as panel out air temperature and compressor head pressure.

During the development phase of a vehicle, several thermal tests have to be conducted in order to validate the design and ensure all vehicle level functional objectives are met. Physical tests are performed both in controlled climatic drive cells and on the road at specific test sites. These tests must be done under specified conditions, since the test data is influenced by various environmental conditions and data correction methods have to be used to interpret the test results. For road trip tests, the results are influenced by several uncontrollable factors, such as ambient temperature, tail and cross wind, free stream turbulence etc. In climatic drive cell tests, some conditions can be controlled but still some conditions such as boundary layer thickness, inlet turbulence level etc, are not consistent with those when driving a vehicle at various test locations. It is therefore important to understand the effects of these free stream conditions on vehicle thermal management.