Software Development And Performance Research Of Methanol/Diesel Dual Fuel Engine

While people enjoy the convenience brought to the world by internal combustion engine,the energy and environment problems are becoming more and more serious.The main energy source of internal combustion engine is limited non-renewable oil.Traditional internal combustion engine emits a large number of harmful gases into the air,especially the particles and nitrogen oxides.It is difficult to reduce both emissions at the same time.In view of the above problems,the traditional internal combustion engine is reformed by adding methanol to participate into the combustion.Methanol has high thermal efficiency and good emission performance,so it has a broad application prospect.The electronic control system of methanol/diesel dual fuel engine is studied in this paper.In this paper,an inline,four cylinder,common rail diesel engine was modified.The methanol supply system was installed on the diesel engine,and methanol/diesel dual fuel engine control software was developed.Through the unit testing and system testing,the dual fuel engine test bench was built in order to verify that the dual fuel engine system is stable and reliable.The performance and emission characteristics of the dual fuel engine were studied experimentally.Based on the concept of modular design,following the “V” development process that is widely used in automotive electronic product development process,a set of methanol/diesel dual fuel engine control software was developed.“V” development process includes demand analysis,general design,software design,code generation,unit test,integration test,system test and bench test.Firstly,the functional requirements of the dual-fuel electronic control system were analysed.Then the general design of the system was adapted as multi-point sequential injection at the inlet port.Then the duel fuel model was divided into four functional modules such as data management module,condition determination module,engine management module and execution module,which are respectively used to manage sensor signal,engine condition migration,calculate actuator parameters and drive actuators.The cylinder deactivation strategy was designed to improve engine performance at light loads.The replacement rate control algorithm can improve the excess air coefficient of the duel fuel engine under the rapid acceleration working condition.In order to realize the requirement of "controlling the methanol substitution rate",the dual fuel output analog signal to simulate the pedal position signal to control the diesel injection indirectly.After the dual-fuel system software design is completed,a series of tests are needed to verify the software function.The test steps in this paper include unit test,system test and bench test.Carry out unit tests on each functional module of the software,write test cases and automated test scripts,and verify the results of unit tests that each functional module can perform functions correctly.System test was used to test the correctness of the whole system function.The code which was automatically generated from the integrated model was downloaded into the ECU,and then the ECU was connected with other parts of the system.The system test results showed that the dual fuel electronic control system functioned correctly and excellent multi-cylinder uniformity,which is ready to enter the bench test stage.The bench test results showed that the dual-fuel electronic control system can meet the functional requirements of the system.Compared with the pure diesel mode,the dual-fuel engine has better economic performance at high loads.The brake specific fuel consumption of the dual fuel mode is 4.98% lower than that of the pure diesel mode at the optimal condition.Soot and NOx emissions are reduced,while HC and CO emissions are slightly larger than that of pure diesel.At light loads,the brake specific fuel consumption of the engine can be obviously reduced with cylinder deactivation strategy,and the emission index can also be improved.Under the working condition of rapid acceleration,the dual-fuel engine can fulfill the acceleration requirement caused by the change of accelerator pedal more quickly through the control algorithm.