| With the formal implementation of new law of environmental protection, the research and development on the energy-saving and environmental protection technology are paid great attention in the various walks of life. Besides of the automotive industry, the construction machinery industry has been the maximum user using the internal combustion engine products. For the construction machinery which work although limited to construction, mining and construction sites, the environment pollution is more serious because of the large emission density leading to the worse emission index compared to the automotive.As the main types of construction machinery, hydraulic excavator directly affect the application prospect of construction machinery.After the development of the key components of hydraulic excavator such as the engine and hydraulic components for many years, their efficiency have been improved greatly but the overall efficiency of the hydraulic excavator is still poor. According to the survey, the overall efficiency of the traditional hydraulic excavator is only 20%. The main two reasons are:(1) the matching technology on the different components doesn’t adapt to the different working condition leading to the high oil consumption; (2) the energy waste decided by the especial working way during the boom dropping and upper device rotation braking exist and need to be recovered. So, the waste energy can be recovered to use again.In this thesis, matching on the overall dynamic system parameters and the recovery on the energy during the boom dropping and rotation braking are the research target. By the way combination with the theory analysis, simulation and experiment, the in-depth study on the energy-saving program and system efficiency of hydraulic excavator is performedThe main research contents in this thesis are as follows:1. The advantages and disadvantages of hybrid power are analyzed and the simulation of machine power, energy consumption, electric motor power and SOC status of super capacitor etc. on the hydraulic excavator of the common system, the oil-electric series hybrid system and the oil-electric parallel hybrid system are performed. The results indicate that effect of the parallel hybrid is the best which can effectively decrease the power of the machine.2. In comparison among the boom,bucket-rod and bucket system, the recoverable energy of boom system is the best, the proportion of which is 49.5% to the recoverable energy and is 15% to the overall energy waste. So, research on the energy recovery of boom system has great practical value. The new boom system with the flow regeneration based on the energy-saving is designed and analyzed. The calculation results indicate that the recovery efficiency of new system is best. By simulation on the effect of key parameters such as motor displacement and throttling area on the recovery efficiency, the determination principle of key parameters affecting the recovery efficiency has been found.3. Based on the special working condition and energy loss of the rotation system of hydraulic excavator, a kind of energy recovery solution combined with the direct and indirect filling is provided. In the light of it. the analysis on the pressure variation of accumulator, recovery flow-rate and recovery energy are performed. And,the effect of accumulator volume, charged pressure and damp coefficient on the recovery efficiency are analyzed so as to get the new way of energy recovery and standard for choosing accumulator. The results indicate that the larger accumulator volume is, the more recovery energy is, the less accumulator pressure is and the lower recovery efficiency is when the charged pressure of accumulator is fixed; the larger charged pressure is. the less recovery flow-rate is. the higher accumulator pressure is and the higher recovery efficiency is when the accumulator volume is fixed. Based on the same way, the analysis on the energy-saving of rotation system is performed for the 4-ton hydraulic excavator. The results indicate that the effect trend is the same to that of the 20-ton.4. Based on the dynamic model of the whole machine combined with the engine and parallel-hybrid system, a kind of dynamic control strategy based on the multiple parameter coordination mode is put forward. By it, the super capacity can match the difference between the engine output and hydraulic pump input energy so that the real time matching of torque among the engine, electric motor and pump can be realized. The results indicate that the fuel efficiency is improved by 13% at least.5. Experiment plan is designed and experiment rig is built so as to test the recovery energy for rotation system of 4-ton hydraulic excavator. The Labview software is used to program for collecting and processing the experiment data such as system pressure, flow-rate and flywheel speed. The energy recovery efficiency can be calculated based on the experiment data. By comparison and analysis between simulation and experiment, reason of the error can be found so as to improve the energy recovery solution. |
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