Power matching on loader engine and hydraulic torque converter based on typical operating conditions

Abstract: In order to avoid the deficiencies of obtaining net engine torque in several common methods, and realize more scientific and reasonable matching between engine and hydraulic torque converter, a hydraulic test system for wheel loader was established, the performances of three sensors were calibrated, and a quantitative relationship was obtained between outlet pressure of hydraulic pump and engine torque consumed by the pump. Some actual tests were performed under typical operating conditions, and the test data were processed by a series of procedures, including segmentation, mergence, filtration, elimination of abnormal value and weighted average calculation with nSoft software, and the engine torque actually consumed by loader hydraulic system was obtained when comprehensively considering operation materials and their corresponding proportions, then a matching scheme between engine and hydraulic torque converter was put forward based on typical operating conditions. According to the original feature data of the tested loader engine, the deducted empiric values of engine torque for full power matching and partial power matching, and the actual engine torque value consumed by loader hydraulic system, three kinds of different characteristic curves of net engine torque were obtained by using a data fitting method. After fitting the original feature data of tested loader hydraulic torque converter, according to the characteristic curves of hydraulic torque converter between efficiency, torque coefficient, moment coefficient and rotational speed ratio, the corresponding torque coefficient, moment coefficient and rotational speed ratio were obtained when the torque converter efficiency was the highest; and according to the matching principle of engine with torque converter and load calculation formula of torque converter, the corresponding torque converter diameters of matching schemes for full power, experimental power and partial power were calculated. On the basis of determining jointly working points of different engine and torque converter matching schemes, and combined with the parameter relationships between pump impeller and turbine of hydraulic torque converter, the jointly working output characteristics of engine and torque converter were obtained, then the average turbo-shaft output power and the average engine fuel consumption rate of turbine working in high efficient area for experimental power matching scheme were calculated by using integral average method, and a contrast analysis of the corresponding calculated values had been carried out among the matching schemes of experimental power, original power and partial power. The results showed that the average turbo-shaft output power of experimental power matching scheme was respectively 17.02% and 42.59% higher than those of original scheme and partial scheme, and the average engine fuel consumption rate of experimental power matching scheme was respectively 3.80% and 8.72% lower than those of original scheme and partial scheme. Therefore, the proposed matching scheme is superior to several kinds of matching schemes commonly used in power matching at present, which provides a reference for optimum design of hydraulic torque converter and proper matching between engine and hydraulic torque converter.