Research The Intelligent Control Method Of The LPG Bus Engine Base On The Quasi-dinmensional Combustion And Emission Model

With the increase of car ownership, car has made people’s life convenient, but at thesame time, also leads to serious problems such as energy shortage, air pollution and so on,thus the development of LPG bus has become one of the effective ways of urbantransportation energy conservation and environmental protection. However, because the LPGfuel combustion is slower and the lean burn limit is relatively narrow, the engine (referred toLPGBE) air-fuel ratio and ignition phase control law of LPG bus have strong nonlinear,time-varying and uncertainty. Under conditions of frequent starting and braking in citytransition, current LPGBE control system meets problems like “reduced dynamicperformance and NO and HC emissions”.Aiming at solving the problems of "reduced dynamic performance, NO and HCemissions" of Guangzhou LPG bus in transient driving process, with a typical LPGBE as theresearch object, the engine experiment platform is established, the change relation amongLPG gas flow rate, air flow rate, boost pressure, inlet pressure, rotating speed andinstantaneous torque and emissions under transient operating conditions, such as starting,acceleration and deceleration were studied. Through theoretical and experimental analysis itcould be got that: in order to satisfy the requirements of high standard for LPG bus engineemissions performance and dynamic performance, the control system should, in accordancewith the physical and chemical characteristics of the fuel, control the gas mass flow andexcess air ratio and ignition phase combustion boundary conditions precisely in steady stateand above the expected values of all transient conditions However, the existing typicalLPGBE control system in engine under transient condition control process not only did notfully take the characteristics of high calorific value and slow burning rate of LPG fuel intoconsideration, but also, in terms of driver intention recognition,, is in lack of the recognitionof the accelerator pedal opening rate of change and its trend In the designed PID controlmethod, the change rate of proportional and integral control parameters and enginecharacteristic relation have not been analyzed, the LPGBE input constraints and stateconstraints, and considering the elasticity and damping of the actuator, clearance, and other nonlinear coupling characteristics have not been correctly designed, which lead to hardproblems like longer transition time of its excess air-fuel ratio control, a large quantity andlow control precision, overshoot ignition control fails to change with the actual air-fuel ratiofluctuation, LPGBE combustion is informal, engine HC, NO emissions increased and torquedecline. Thus, first of all, with one bus line in central district of Guangzhou as the conditionand typical LPG bus as the object, this article establishes the LPGBE engine experimentalplatform, and carries out test on the LPGBE bus engine control process, and through test andcontrol system analysis, the reasons of informal LPGBE combustion, engine NO and HCemission, torque declines are got. Then, on the basis of the transient condition of gas enginetorque, change relations between the NO and HC and the combustion boundary conditions, amodel based on quasi-dimensional combustion and emissions LPGBE is proposed, then thecylinder pressure during the gas engine combustion process and the change relation oftemperature inside the cylinder along with the crank shaft Angle is analyzed. And the LPGBEsimulation platform is set based on the working condition of the city through using GTpowerand KIVA software, and change rule between the air-fuel ratio and ignition advance Angle aswell as the change relation between the torque and the emission are quantitatively studied,Then, according to the laws of the air-fuel ratio control, LPGBE intake system model isestablished, the relationship among the fuel valve opening, the throttle opening, inlet pressure,rotating speed and other factors and actual air-fuel ratio is studied, a LPGBE rolling timedomain of neural network control method is proposed, a LPGBE intelligent control methodbased on Quasi-dimensional combustion and emission model(LICMQCE) is proposed, themethod is composed of fuel mass flow adjusting method based on neutral network ofreceding horizon and ignition advance angle adjusting method based on neutral network. Thehardware in loop test system based on LICMQCE is established while taking the dynamicchange relations of model parameters along the conditions and road data collected based onthe LPG real vehicle into consideration, then, through simulation of real vehicle emissioncharacteristics, the LICMQCE hardware in loop system of the controller and LPGBEemission dynameters test platform are developed, and therefore verify the feasibility of thebus gas engine intelligent control method based on quasi-dimensional combustion and emission model.