Browse Publications Technical Papers 2002-01-0256

Cooling Inlet Aerodynamic Performance and System Resistance 2002-01-0256

This report is a contribution to the understanding of inlet aerodynamics and cooling system resistance. A characterization of the performance capability of a vehicle front-end and underhood, called the ram curve, is introduced. It represents the pressure recovery/loss of the front-end subsystem - the inlet openings, underhood, and underbody. The mathematical representation, derived from several experimental investigations on vehicles and components, has four basic terms:
  • Inlet ram pressure recovery; free-stream energy recovered when the vehicle is moving
  • Basic inlet loss; inlet restriction when the vehicle is stationary
  • Pressure loss of the engine bay
  • Engine bay-exit pressure
Not surprisingly, the amount of frontal projection of radiator area through the grille, bumper and front-end structure (called projected inlet area), and flow uniformity play a major role in estimating inlet aerodynamic performance. One experimental investigation demonstrated that the ram curve is independent (essentially) of the fan/shroud system installed in the vehicle. Another experiment showed that the engine-bay pressure loss (which includes the interference of the underhood package on fan performance) might be small compared to the other resistances. The universal characteristic map of fan and system performance can be used to track airflow changes during early vehicle design tradeoff studies.


Subscribers can view annotate, and download all of SAE's content. Learn More »


Members save up to 18% off list price.
Login to see discount.
Special Offer: Download multiple Technical Papers each year? TechSelect is a cost-effective subscription option to select and download 12-100 full-text Technical Papers per year. Find more information here.
We also recommend:

An Automotive Front-End Design Approach for Improved Aerodynamics and Cooling


View Details


Development and Use of LDV and Other Airflow Measurement Techniques as a Basis for the Improvement of Numerical Simulation of Engine Compartment Air Flows


View Details


Assessment of Engine Cooling Performance by Measurement of Cooling Airflow Drag in Aerodynamic Wind Tunnels


View Details