Study On Energy Flow Of Heavy Commercial Vehicle Under Transient And Steady State Condition

Due to the growth of population and the change of people’s way of life,the world’s energy use has increased dramatically.The shortage of fossil energy is accompanied by the serious problem of environmental pollution,which makes it imperative to save energy and reduce emission.The study of energy flow can well grasp the distribution of each energy balance term of internal combustion engine(ICE),evaluate the performance of ICE under different control strategies and accessory arrangement,and optimize the control parameters and related structures,which is of great significance to the accurate control of ICE heat balance under steady and transient conditions.In this paper,a China Ⅵ emission standard six-cylinder diesel engine was carried out based on the platform of coolant temperature steady flow of energy research,analysis of steady state conditions coolant temperature on the impact of each energy balance,and the coolant temperature on the impact of engine combustion process,economy and emissions.In addition,for the sample vehicle equipped with this engine,the variation and distribution of the energy flow of the vehicle during the start-up of the cooling and warmed up engine under C-WTVC transient condition were carried out on the hub test rig.The main research contents and conclusions are as follows:(1)The engine thermodynamic model under steady-state condition was built,and the energy balance equation was obtained through relevant thermodynamic formulas.The influence of cooling water temperature on engine combustion characteristic parameters and energy balance terms under different load conditions was studied.At idle speed and small load stage,the variation of CA50 with water temperature was not obvious,but it moved back with the increase of load.About economy,the optimal fuel consumption area of the test prototype is well expanded with the rise of coolant temperature.Small water temperature increase has little effect on smoke emissions,while NOx emissions value increase with the increase of water temperature,and it is very obvious under medium and high load condition.(2)We put forward the calculation method of transient conditions vehicle energy flow,combined with the C-WTVC transient cycle of different working conditions,revealed the change rule of vehicle flow and distribution characteristics.The main influencing factors of total fuel energy,effective power,coolant loss,exhaust loss,mechanical loss and residual loss are discussed respectively.Each part of the energy change is closely related to the vehicle speed;Exhaust loss is greatly affected by exhaust temperature and exhaust mass flow rate;The main influencing factor of coolant loss is the water temperature difference between inlet and outlet of engine.Results reveal the influence of coolant temperature on engine performance,and the energy balance of distribution under steady state conditions and vehicle transient operating conditions.And the energy utilization has provided the theory and data support.At the same time,it enriches the study of energy flow under the C-WTVC cycle condition,and provides a direction for the engine performance optimization under this condition,which is of great significance to improve the fuel consumption rate of the vehicle and reduce the emission.