Fan Shroud Design for Low Speed Damageability

An engine cooling system in an automotive vehicle comprises of heat exchangers such as a radiator, charge air cooler and oil coolers along with engine cooling fan. Typical automotive engine-cooling fan assembly includes an electric motor mounted on a shroud that encloses the radiator core. One of main drivers of fan shroud design is Noise, Vibration, and Harshness (NVH) requirements without compromising the main function of airflow for cooling requirements. In addition, there is also a minimum stiffness requirement of fan shroud which is often overlooked in arriving at optimal design of it. Low Speed Damageability (LSD) assessment of an automotive vehicle is about minimizing the cost of repair of vehicle damages in low speed crashes. In low speed accidents, these fan motors are subjected to sudden decelerations which cause fan motors to swing forward thereby damaging the radiator core. So designing fan shroud for low speed damageability is of importance today. In this paper, the design development of fan shroud using CAE and testing has been illustrated. Lack of sufficient stiffness of the fan shroud has been identified as the source to cause damage to radiator in a vehicle low speed crash test. In addition to vehicle level simulations used to guide the fan shroud design, this paper describes how a sub system level simulations and testing under low speed impact loading conditions can be used to predict contact between fan motors mounted on fan shroud and radiator. Also a generic pulse representing low speed impact conditions up to 16 km/h has been recommended as the loading pulse. Finally, an effective design guideline has been proposed as a requirement in designing a fan shroud to eliminate damage due to inertial movement of fan motors in low speed impacts.