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Cold Testing to -40°F of Isolated Transmission Components
Project Brief
Concerns about low temperature performance have prompted manufacturers to aggressively evaluate their internal transmission components in this regime. This type of evaluation has relied heavily on laboratory testing because analytical models are unable to predict cold temperature effects with accuracy.
Technical challenges due to the external ATF reservoirs were involved in the testing of isolated transmission components such as pumps and torque converters to temperatures of −40°F. To overcome problems such as moisture condensation, fluid pumpability and fluid gelling, Southwest Research Institute (SwRI) created a unique hardware system to provide controlled ATF cooling rates and conditions to achieve extremely low temperatures.
The system consists of two multi-pass systems that chill the air and ATF. For example, on a pump stand the test article is mounted in a precision aluminum fixture attached to a headstand. Underneath the pump is a reservoir. The reservoir contains a two-pass heat exchanger, integral serpentine tubing and spray bars. One pass of the reservoir contains a continuously circulating ethyl alcohol solution chilled to −40°F. The other pass contains continuously circulating ATF drawn from the reservoir.
In the air immediately above the reservoir and housed in an insulated chamber is a two-pass heat exchanger. One pass contains closed loop pressurized liquid nitrogen. The other loop contains pressurized gaseous nitrogen that continuously dries and chills the air in contact with the test pump and ATF. Uniform temperatures must be obtained in the fluid, test article, steel structure and chamber air to assure that realistic and repeatable test data are obtained.
Typically, the test article performance is quantified by measuring the operating torque or torque loss associated with the component. This requires that precision rotary torque transducers be used that are temperature-compensated to extremely low temperatures.
For more information about our drivetrain engineering capabilities and past performance briefs, or how you can contract with SwRI, please contact Douglas Fussner at dfussner@swri.org or (210) 522-3972.
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Southwest Research Institute® (SwRI®), headquartered in San Antonio, Texas, is a multidisciplinary, independent, nonprofit, applied engineering and physical sciences research and development organization with 11 technical divisions. | ||||||||||||||||
December 28, 2012 | ||||||||||||||||
