Development and Validation of the SAE J3052 High Pressure Differential Flow Rate Recommended Practice 2017-01-2498
This paper describes the development work that went into the creation of the SAE J3052 “Brake Hydraulic Component Flow Rate Measurement at High Delta Pressure”, and also shows some example applications. The SAE J3052 recommended practice is intended to measure flow characteristics through brake hydraulic components and subsystems driven by pressure differentials above 1 bar, and was anticipated by the task force to be invoked for components and subsystems for which pressure response characteristics are critical for the operation of the system (such as service brake pressure response and stopping distance, or pressure rise rate of a single hydraulic circuit in response to an Electronic Stability Control command). Data generated by this procedure may be used as a direct assessment of the flow performance of a brake hydraulic component, or they may be used to build subsystem or system-level models.
Two significant variants of test methodology were studied, including use of a servo-actuator against a hydraulic cylinder to push fluid through the test specimens at a high rate, and the use of a high pressure pump to create a target pressure differential across the test specimen.
In the course of test development, experiments were run with two different calibrated orifice sizes, with two different ESC modules (representing common test specimens), and two different calipers (relevant to the servo-actuator based method). Data derived from each method were fitted into brake system models for two different vehicle (a car and a light truck). Observing which method produced better correlation to physical vehicle test results was the final arbiter of the best methodology, and shaped the final form of the recommended practice.