Research On Variable Displacement Technology Of GDI Engine

With the rapid development of automobile industry,dependence on imported oil has been increasing in China,and the environmental pollution caused by the combustion of petroleum fuel is becoming more and more serious.Therefore,energy-saving emission reduction is very urgent.The design of automobile engine displacement is to meet the dynamic performance of the target,but in the case of low speed,small and medium load conditions,the too large displacement of engine would result in a large loss of pump loss and heat transfer loss,therefore the fuel consumption is higher.In order to solve the problem,changes according to demand of the cylinders are made,the cylinders are able to operate in lower fuel consumption.In this way,we can make balance between large-displacement engine power and small-displacement engine emissions.But the comfort of driving is influenced in this process.To solve this problem,the research works as follows:In the first part,simulation models of gasoline direct injection are made by GT-Power and Matlab/Simulink.Realize the engine stopped two-cylinder control,stop for a cylinder,20% cylinder rate cycle circulation control,33% control,obtains a different stop strategy corresponding to the torque and specific fuel consumption.Established in the Simulink throttle control module,cylinder deactivation control module,ignition timing control module and valve timing control module,the average torque calculation module,average fuel consumption rates and PID feedback control modules,through changing these modules,fuel consumption and instantaneous torque of cylinder is reduced.And we come to these conclusions:1 Implementation of the two cylinder engine deactivation control,one cylinder engine deactivation control,20% cylinder deactivation rate cycle control,33% cylinder deactivation rate cycle control,obtained a different strategy corresponding to the deactivation cylinder torque and fuel consumption rate;by optimizing the deactivation cylinder time.Cylinder can be deactivated at intaking air before TDC angle of 30° crank to obtain the best fuel consumption rate and fuel consumption rate is getting better with the increasing deactivation rate.2.By optimizing the fixed cylinder deactivation time,30° crank angle before the intake valve open starting to stop cylinder can get the best fuel consumption rate,two cylinders and stop a ratio compares two cylinders fuel economy are better.3.Engine cylinder instantaneous,torque will suddenly decrease,respectively,explores the throttle control,ignition advance angle control,valve timing control for torque effects.In the second part,LMS measurement technique of non-contact electromagnetic torsional vibration measuring principle,from data acquisition to the findings of the trial dealing with the whole process;exploring different cylinder on the vibration,the impact of speed fluctuation and torsional vibrations,by comparing the two tanks in six different two-cylinder and four different programmes.And we come to these conclusions:1.If reducing two cylinders is required in order to reduce the engine cylinder vibration amplitude,we should select to stop 1,4 cylinder,or stop 2,3 cylinder.2.If reducing two cylinders is required in order to reduce the engine cylinder vibration amplitude in some specific speed,we should stop 1,2 cylinder or 1,3 cylinder or 2,4 cylinder or 3,4 cylinder in high speed.And stop 1,4 cylinder or 2,3 cylinder.3.In order to reduce torsional vibration of engine,cylinder should be chosen close to the free end of the crankshaft cylinder,gas torque near the crank of physical output,reduce crankshaft torsional angle,reducing risk of torsional vibration of crankshaft damage.