Pressure-Loss Characteristics and Energy-Dissipation Mechanisms of a Centralized Valve-Controlled Hydraulic System During Boom-Cylinder Extension in an Electric Excavator

Pressure losses in centralized valve-controlled hydraulic systems limit hydraulic efficiency in electric excavators. This study examined boom-cylinder extension on a 4.3 t electric excavator using a 40-point matrix of main-spool opening and motor speed. For each retained response, the steady propulsion stage (S2) was identified, and repeated-response averages formed a pressure-loss-ratio map; independent reprocessing gave a mean absolute difference of 0.40 percentage points. The ratio generally increased with motor speed at fixed opening and with decreasing opening at fixed speed. Across the 40–100% openings, the speed-induced span was 5.30–7.47 percentage points; at the nominal 15% opening, the ratio converged within 67.21–68.20%. The measured return-to-supply pressure-drop ratio increased from 0.56 to 0.60 at 40–100% to 3.41 at 15%, indicating a shift toward return-path dominance. A calibrated 16.3% simulation input represented the nominal 15% setting. Across the full map, including this calibrated correspondence, the model yielded a mean absolute relative error of 4.83% and a root mean square error of 2.54 percentage points. Simulation decomposition showed the speed-averaged combined pressure-drop share of four valve-related restrictions increasing from 26.12% at full opening to 96.50% at the calibrated small opening. The case-specific benchmark supports pump-speed/spool-opening co-calibration and future matched-boundary comparison with distributed pump-controlled systems.