Study On Energy Flow Distribution Characteristics Of Diesel Engine Under Vehicle Operating Condition

As the main means of transportation,heavy vehicles are the important support to promote the high-quality development of road transportation industry.But the use of heavy vehicles consumes a lot of fuel and causes serious air pollution.With the shortage of resources in the world and the increasingly serious environmental pollution,the development of high efficiency and low emission internal combustion engine is one of the current research hotspots.The internal combustion engine is widely used as the power source of heavy vehicles because of its high thermal efficiency.Generally,the effective thermal efficiency of gasoline engines is between 30% and 40%,and that of diesel engines is between 35% and 45%.However,the improvement of combustion efficiency of internal combustion engine is limited by fuel characteristics and combustion conditions,especially in practical road operation,the frequent start and stop of vehicles will cause a large amount of energy loss.Therefore,it is of great guiding significance to explore the energy flow distribution characteristics and influencing factors of internal combustion engine under vehicle road conditions to improve the energy utilization efficiency of internal combustion engine.The main contents of this paper are as follows:(1)The Vehicle energy flow test rig was built,and the role and measurement methods of each equipment and instrument on the test rig were described in detail.The test content and test conditions were introduced in detail,and the diesel engine in the all-features steady-state condition and C-WTVC(China-World Transient Vehicle Cycle.The energy flow test under the condition of China-world transient vehicle cycle is presented,and the theoretical calculation formulas of various energy flows(fuel energy flow,effective work,pump air loss energy flow,exhaust energy flow and coolant energy flow)based on the thermodynamic law are introduced.(2)The data of fuel flow,average effective brake pressure,coolant temperature and flow,inlet and exhaust temperature and flow and other parameters of the test vehicle under steady-state condition and C-WTVC condition were obtained through the test.Combined with the theoretical calculation formula of energy flow,the energy distribution characteristics of diesel engine under steady state and C-WTVC conditions are obtained.Under THE C-WTVC condition,the effective work,exhaust energy flow,coolant energy flow,pump gas loss energy flow and other energy flow losses accounted for 35.7%,35.08%,19.64%,2.05% and 7.52%,respectively.The analysis results show that the operating conditions have the greatest influence on all energy flows,in which the coolant energy flow is mainly affected by the coolant mass flow rate,and the exhaust energy flow is mainly affected by the exhaust mass flow rate.(3)of the vehicle system based on GT-Suite software one dimensional modeling,by changing the vehicle boundary conditions such as coolant temperature,inlet temperature,injection pressure,explore its vehicle in C-WTVC cycle of three working conditions the energy flow distribution characteristics,and also analyzes the condition and reduction conditions for a period of accelerated under various real-time changes in energy flow characteristics.In this paper,the characteristics of energy flow distribution of diesel engine of a heavy vehicle under C-WTVC road cycle were studied by combining test and simulation,and the influence of various parameters on energy flow distribution was explored by changing boundary parameters.The research results not only provide reference value for improving the actual fuel efficiency of heavy vehicles,but also provide a theoretical basis for improving the fuel efficiency of heavy vehicles.It also points out the improvement direction for reducing the energy loss of internal combustion engine.