Improving Performance of a Heavy Duty Engine Cooling Drive Through Reduction of Drag Losses

1
Improving Performance of a Heavy Duty Engine
Cooling Drive Through Reduction of Drag Losses
Project Background
BorgWarner Thermal Systems is known worldwide
for its advancements in automotive technology as
the leading designer and supplier of engine
thermal management components for global vehicle
manufacturers. The Cool Logic heavy duty,
multi-speed fan drives are a breakthrough in
engine cooling technology. These fan drives are
electronically controlled and built to last,
while improving fuel economy and meeting
emission requirements.
Simplified views of the clutch fan
assembly Within the Cool Logic clutch fan
assembly lays a rotating housing used to move
the fan powered by the engine. This assembly acts
as a clutch fan to control the rotation of the
fan at variable operating speeds. To ensure
that the clutch fan assembly is cooled and
lubricated properly, a static pump enclosed in
the assembly is used to transfer
Automatic Transmission Fluid (ATF) into the
assembly housing. The static pump protrudes into
the clutch assembly housing. During operation,
the assembly housing rotates between a range of
600 to 3600 rpm, which forces ATF to flow over
and around the static pump. This static
pump experiences drag losses due to its
interruption of the flow of the rotating fluid.
Two means of drag losses on the static pump are
skin friction drag and pressure drag. By
reducing these losses, a redesign of the static
pump could ultimately reduce the drag on the
entire Cool Logic clutch fan assembly, thus
improving engine efficiency.

• Approach
• The drag loss problem on the static pump was
  approached using the
• the following tools
• Fundamental principles of Aerodynamics and
  Fluid Mechanics
• Computational Fluid Dynamics (CFD) Analysis
• - Modeling and meshing using Gambit
• - CFD Testing completed in Fluent
• - Three different cross-section profiles
  evaluated
• Flow Visualization through Experimentation
• - Conducted using a window inserted in the
  cap of the clutch
• fan assembly to visualize the flow path of
  the ATF
• - Confirm the level of the rotating fluid
  inside the clutch housing
• - Observe the separation of the fluid flow
  as it intersects the
• static pump
• - Two different shaped static pumps tested
  and compared under
• a constant experiment conditions

Flow Visualization Through
Experimentation
BorgWarner Cool Logic Clutch Fan Assembly
Project Sponsor Information Sponsor
BorgWarner Thermal Systems Location Marshall,
Michigan Sponsor Representatives Mr. Dale
Pickelman Mr. Don Buckley
Original Static Pump
Airfoil Prototype Pump
Experiment Setup

• Testing Parameters
• Two different pumps designs
• Testing Speeds 600 1200 rpm
• Testing Observations
• The fluid flow over the original static pump
  design led to more separation
• The flow over the airfoil static pump was much
  more controlled there was less separation
• Much less separation in the airfoil pump
  compared to the original pump
• Tests at 1200 rpm were similar in that the
  airfoil pump design affected the flow much less
  than the original pump design (i.e. less
  separation)

CFD Analysis
Flow Over Original Pump (600 rpm)
Flow Over Airfoil Prototype Pump (600 rpm)
Team Information
Team Members
Evan DiMaggio George Elliott
Kyle Jose
John Sanburn Faculty
Advisor Dr. Oguzhan Guven
Example of a 2-D Meshed Model in Gambit -
Original Pump Design
Velocity Contour Plot Original Pump Design

• Project Conclusions
• CFD Analysis
• The drag force on the static pump was determined
  to be reduced
• by designing the pump with an airfoil shape. The
  drag force
• reduction percentages, as compared with the
  correlation of the
• current static pump design, are as follows
• Production Airfoil38.6 reduction
• Standard Airfoil......68.0
  reduction
• Test Fixture
• Fluid flow level (from the housing outer
  diameter)
• measured as approximately 2.9 cm
• The flow over the airfoil static pump caused
  much less
• separation of the boundary layers and less
  disruption of the flow
• The drag force was reduced with use of the
  airfoil static
• pump design, compared to the original static
  pump design

Design
Constraints Certain specifications and
constraints needed to be followed as
instructed by the project sponsor. The static
pump needed to remain near its current height to
fit in the existing clutch fan assembly. Also,
it was to remain located in the nine-oclock
position when viewing the housing from the front
view. The width and shape of the part were
allowed to be adjusted to achieve a more
aerodynamic and efficient pump design. The 48
ounces of ATF used for the working fluid in the
assembly remains at a level slightly below the
halfway point of the entire housing, when the
clutch is not engaged. The fluid can move at a
maximum rotational speed of 3600 rpm around the
interior of the housing. The average operating
speed of the fluid was 2000 rpm, which was
analyzed to determine the nature of the flow was
present. The drag losses on the original static
pump design at 2000 rpm are approximately 5
horsepower.
Velocity Contour Plot Production Airfoil Design

• Design Recommendations Future Analysis
• CFD Analysis
• It is recommended that the static pump be
  designed with an
• airfoil shape similar to that of the standard
  airfoil shape
• constructed by the team
• Further CFD Analysis recommendations
• - 2-D analysis on front view of the static pump
• - 3-D turbulent flow analysis
• - Data obtained should be run through Heeds, or
  a
• similar optimization program, to optimize the
  airfoil shape
• Test Fixture
• It is recommended that the static pump be
  designed with the airfoil
• shape due to its reduction in both drag and flow
  separation as
• compared to the current static pump design.
  Further testing on
• airfoil shaped static pumps should be conducted,
  including
• Production airfoil design
• Standard airfoil design as modeled for the CFD
  analysis

Velocity Contour Plot Standard Airfoil Design

• Project Goals
• Improve the design of the static pump to
  minimize drag losses
• Formulate design recommendations based on a
  comparative
• analysis with the current pump design
• Reduce power losses on the Cool Logic clutch
  fan assembly through
• reduction of drag on the static pump
• Understand the nature of the flow of the ATF as
  it rotates around the
• interior of the clutch fan housing and
  interacts with the static pump
• Develop a visualization of the centrifugal
  forces acting on the fluid
• Determine the level of fluid that the pump
  observes at varying speeds

Special Thanks Recognition Automotive
Research Experiment Station Dr. Harold Schock
Mr. Tom Steucken Spartan Oil
Corporation Computational Fluid Dynamics
Laboratory Srikanth Sridhar
Estimated correlation of Horsepower Loss based
on Fluent data