Study On Efficiency Model Of Gasoline Engine Used By Hybrid Electric Vehicle

That engine always operates in high efficient operating range is one of main energy saving ways of hybrid electric vehicle. However, it is difficult to accurately control the engine used by the hybrid electric vehicle because the fuel consumption characteristic of the engine varies with external surroundings and its own conditions dynamically. Even though at present the method of correction factors is used to confirm the high efficient operating range of the engine which varies dynamically, there is no theoretical basis to support the correction factors to be sharing among different series of the engines. The experimental working of confirming the correction factors is too heavy and correction factors can not correct the dynamic changes of the high efficient operating range due to the conditions change of the engine itself, it also can't be guaranteed to the accuracy of the correction factors obtained through experiments under different external surrounding conditions. The reasons analyzed above lead to the hybrid electric vehicle's several shortcomings of long development cycle, high research and development cost, can't guarantee the control accuracy of the engine. So far, there is no relevant report about resolveing the problems above mentioned in the data bases of SAE and CNKI, which makes the relevant research more difficult. That founding general efficiency model of the engine used by hybrid electric vehicle which is based on the engine's operating state parameters in order to control the engine operating in high efficient operating range by feedback control under the conditions of different engines, different external surroundings, different conditions of the engine itself is significant without doubt to reduce the development cycle, reduce the high research and development cost, and guarantee the control accuracy of the engine.Based on LJ491QE1 and 4G18-AA gasoline engines as research objects, for the first time, this paper presented the theory to employ the air exchange equivalent loss which is based on the temperature and pressure of the intake and exhaust and the experience air exchange equivalent loss which is based on the pressure of the intake and exhaust as efficient model of the above mentioned naturally aspirated and port fuel injection gasoline engine used by hybrid electric vehicle to confirm the engine's high efficient operating range which varies dynamically. Also for the first time, this paper deduced the energy equition for Newtonian ideal airflow which can be used to calculate the energy of the low speed, steady, laminar actual airflow and the engine's air exchange loss and the energy taken away by the engine's exhaust can also be quantitative calculated by the energy equition. The formulas for calculating gasoline engine exhaust's gas constant, specific heat at constant volume, specific heat at constant pressure, ratio of specific heat and combustion efficiency, intake's gas constant were also obtained through theoretical derivation. The experience effcieny model of gasoline engine used by hybrid electric vehicle (the experience air exchange equivalent loss) can obtain better responsiveness than the effcieny model of gasoline engine used by hybrid electric vehicle (the air exchange equivalent loss) in the gasoline engine's feedback control and the control module of the gasoline engine can control the engine to operate in high efficient operating range through feedback control only using two parameters which are intake and exhaust pressure with parameter of fuel consumption unknown.The major works and conclusions as follows:The major energy-saving ways of the hybrid electric vehicles were discussed and the uncertainty of engine's fuel consumption characteristic was analysed. Series hybrid electric vehicles were taken as example to present the problems in the engines'control of hybrid electric vehicles. The conception of optimal speed characteristic curves and efficiency model of engines used by hybrid electric vehicles were introduced and the solution for resolving the problems in the engines'control of hybrid electric vehicles was confirmed.In order to quantize the variation range of load percentage, the engines'operating condition range under the load characteristic was partitioned. The conception of high efficient operating range was introduced in order to quantize the operating range of better engines'economy. That the scope of experimental research was focused on the medium and heavy load operating contions under which better fuel economy can be obtained was determined by means of experimental study on the LJ491QE1 gasoline engine. The practical work process of the naturally aspirated and port fuel injection gasoline engine was analysed based on the indicator diagrams of the LJ491QE1 gasoline engine, the equal compression ratio model of ideal cycle model applicable to gasoline engine and the component of the effective power were made clear based on ideal cycle model of internal combustion engine.The LJ491QE1 gasoline engine was taken as object of experimental study, the mechanical loss variation laws of the naturally aspirated and port fuel injection gasoline engine was studied by means of the analysis and the experiments and draw the conclusion that the mechanical loss power under load characteristic can be treated as a constant which is determined by the intrinsic feature of the engine itself. The combustion efficiency formula of gasoline engine was deduced and power balance equation of actual cycle was built.The conclusion was made clear that the"system"and"control volume"in Fluid dynamics are corresponding to the"open system"and"closed system"in Thermodynamics. The conclusion was also made clear that without considering the change of kinetic energy and potential energy, the conversion of heat and power between working medium and surroundings cause the change of internal energy in the system and the conversion of heat and power between working medium and surroundings cause the change of enthalpy in the control volume. By means of theoretical derivation, the conclusion was drawn that the fluid layer model and the fluid column model of full developed non-compressible fluid (steady) flow in circular tube have the same essence. The conception of Newtonian ideal airflow was introduced, the energy equition for Newtonian ideal airflow was deduced and the essence of enthalpy was made clear. The formulas for calculating exhaust gas constant Rge, specific heat at constant volume of exhaust c ve0 , specific heat at constant pressure of exhaust , specific heat ratio of exhaust ke and intake gas constant Rgi were deduced by means of theoretical derivation. The conclusion that the density of LJ491QE1 gasoline engine's exhaust can be approximated as constant and the conclusion that the thermodynamic energy increase of intake because of heating by intake pipe can be ignored were drawn by means of the expertment study on the LJ491QE1 gasoline engine. On the basis of energy equition for Newtonian ideal airflow, the aie exchange loss of the LJ491QE1 gasoline engine was qualitatively studied. The energy taken away by exhaust can also be qualitatively calculated by the energy equition for Newtonian ideal airflow.On the basis of experimental study on the LJ491QE1 gasoline engine, the following conclusions were drawn: the crank angle can be regarded as fixed value while the cylinder pressure researches its peak value under the better efficiency operating condition of medium and heavy load, the exhaust flow can be regard as full developed non-compressible fluid (steady) flow in circular tube whose length is a fixed value, the powerloss caused by exhaust is in proportion to the square of the exhaust gage pressure value.The conception of air exchange equivalent loss was introduced and by the study means of load characteristic experiments, small interval load characteristic experiments, variable structure load characteristic experiments, the following conclusions were drawn: the air exchange equivalent loss eqr and the break specific fuel consumption ge have the same variation law under load characteristic, the air exchange equivalent loss eqr was the main factor which influence the evolution of the break specific fuel consumption in the high efficient range under load characteristic, and the air exchange equivalent loss can be eqr treated as the efficiency model of the LJ491QE1 gasoline engine under load characteristic.The conception of air exchange experience equivalent loss was introduced, by the study means of load characteristic experiments, small interval load characteristic experiments, variable structure small interval load characteristic experiments to the LJ491QE1 gasoline engine and by the study means of load characteristic experiments, variable structure load characteristic experiments to the 4G18-AA gasoline engine, the following conclusions were drawn: the air change experience equivalent loss Eqr and the brake specific fuel consumption ge have the same variation law under load characteristic, the operating condition while the air exchange experience equivalent loss Eqr reached its least value under the load character correspond to the high efficient operating range of the engines. In comparison with the air exchange equivalent loss eqr, better responsiveness in engine feedback control can be reached using the air exchange experience equivalent loss Eqr as the efficiency model of naturally aspirated and port fuel injection gasoline engine, the electrical control unit can control the engines operating under high efficient operating range only using two parameters of intake and exhaust pressure with the parameter of fuel consumption unknown.