Minimizing Steady-State Testing Time in an Engine Dynamometer Laboratory 2023-01-0209
In the automotive industry, performing steady-state tests on an internal combustion engine can be a time consuming and costly process, but it is necessary to ensure the engine meets performance and emissions criteria set by the manufacturer and regulatory agencies. Any measures that can reduce the amount of time required to complete these testing campaigns provides significant benefits to manufacturers. The purpose of this work is then to develop a systematic approach to minimize the time required to conduct a steady-state engine test campaign using a Savitsky-Golay filter to calculate measured signal gradients for continuous steady-state detection. Experiments were conducted on an Armfield CM11-MKII Gasoline Engine test bench equipped with a 1.2L 3-cylinder Volkswagen EA111 R3 engine. The test bench utilizes throttle position control and an eddy current dynamometer braking system with automatic PID control of engine speed. Data from engine signals (e.g. exhaust temperature, engine speed, air-fuel ratio etc.) were continuously collected, allowing for detection of steady-state and further analysis in post-processing.
In this preliminary work, two distinct approaches were studied for generating a map of engine data in the typical load/speed operating space: 1) a constant-speed variable-throttle/load sweep, and 2) a constant-throttle variable-speed sweep. Both test approaches were equally capable of generating the desired engine operating map, but using the second approach, i.e., the constant-throttle sweep, saved an average of 41 seconds per operating point, representing a 15% reduction in total time to steady-state for the operating points tested. This reduction was due to the decrease in exhaust temperature change between engine operating points associated with changes in engine speed as opposed to changes in engine load, as well as the improved dynamic response in engine speed of the eddy current dynamometer braking system.