Experimental And Simulation Investigation On Operating Characteristics Of A Hybrid Hydraulic Passenger Car With An Output Coupled Power-split Transmission

Automobile, which plays a stimulative role in social economic and culturaldevelopment, is the most important traffic and transportation tool and a sign of socialscience and technology development level all over the world. However, with the rapiddevelopment of industrial production and transportation industries, energy resourcesshortage and environmental pollution problem are becoming more and more severe.Thus, improving energy saving and clean automobile turns to be the inevitable choicefor the automobile industry. Hybrid technique, which can recycle regenerative energyand make the power sources work in the highest efficiency range to reduce fuelconsumption and toxic emissions, is an effective way to alleviate energy resourcescrisis and environmental deterioration before a new and clean energy technique comesinto full play.Because of electrochemistry energy transformation of batteries, recyclingeffeciency of regenerative energy and the consistency of cells are limited for a hybridelectric vehicle. Unlike batteries, hydraulic accumulators could accept exceptionallyhigh rates of charging and discharging, so that hybrid hydraulic vehicles possesslonger life spans and need no special ways to deal with the disused batteries. Thus, thecharacteristics of hybrid hydraulic vehicles could fully satisfy the requirements forvehicles running under urban traffic conditions with a high stop-and-go frequency.A novel power-split transmission was proposed and the operating principle wasanalyzed, after which the corresponding mathematical model, simulation model and aprototype were established.Based on the analysis of the main factors that can influence power performanceand fuel economy of the hybrid hydraulic vehicle, the matching of the propulsionsystem’s key components and system working parameters were optimized. Comparedwith the original car, the power performance of the hybrid hydraulic vehicle could beimproved, though the maximum speed was reduced in some extent. The systemoptimization results and transmission characteristics show that, the application of theproposed power-split transmission would fit for passenger cars faultlessly.After the modeling method, work principles and operating characteristics ofsub-systems were introduced, a numerical model employed a forward-looking logic ofthe hybrid hydraulic vehicle was built to simulate the real situation. Base on the numerical model, the operating characteristics of the hybrid hydraulic vehicle wereinvestigated in detail. According to the theoretical analysis results, the hybridhydraulic vehicle had two working modes to achieve quick start/stop, which could cutfuel consumption and emissions during engine starting and idling. While braking, themaximum regenerative energy recycled efficiency could reach more than60%. TheNEDC test results show that, the fuel consumption were6.16L/100km,6.07L/100kmand6.10L/100km, and the fuel economic improvement were31.5%,3.6%and16.1%for UDC, EUDC and NEDC running schedule, respectively. According to the fueleconomic improvement compared with the original car, it can get the conclusion thatregeneration is a major factor in impressive benefits under city driving conditions, andengine optimization provides a benefit in some extent.On the basis of the output power-split transmission test platform, the relationshipof torque, rotation speed and friction effects were tested, which afford data for thematching and optimization of the propulsion system’s key components and systemworking parameters as well as the calibration of simulation models. According to theregulated testing procedure given by GB18352.3-2005, the fuel economy and powerperformance of the hybrid hydraulic vehicle was investigated on a chassisdynamometer. The test results indicated that, compared with the original car, the fueleconomy was improved by29.1%,-1.1%and12.4%during UDC, EUDC andNEDC running schedule, respectively. The test results also show that, the numericalinvestigation was validated and the application of the proposed power-splittransmission tends to be an effective way to promote the fuel economy for the futuredevelopment of passenger cars.