Refining Measurement Uncertainties in HCCI/LTGC Engine Experiments

This study presents estimates for measurement uncertainties for a Homogenous Charge Compression Ignition (HCCI)/Low-Temperature Gasoline Combustion (LTGC) engine testing facility. A previously presented framework for quantifying those uncertainties developed uncertainty estimates based on the transducers manufacturers’ published tolerances. The present work utilizes the framework with improved uncertainty estimates in order to more accurately represent the actual uncertainties of the data acquired in the HCCI/LTGC laboratory, which ultimately results in a reduction in the uncertainty from 30 to less than 1 kPa during the intake and exhaust strokes. Details of laboratory calibration techniques and commissioning runs are used to constrain the sensitivities of the transducers relative to manufacturer supplied values. The uncertainty framework is also extended to consider additional sources of uncertainty, including non-ideal engine volume history due to kinematic effects on the effective connecting rod length. Finally, the uncertainty propagation chain is analyzed to determine primary uncertainty sources, and mitigations are discussed.