Optical Studies On Combustion Process In A Single Cylinder DI Diesel Engine

In the engine development early time, combustion system development throughconsultation and benchmark to define design direction, and by a large number of testingfound the optimized parameters, then for the production. Some companies do not have thecapabilities of combustion development; this is the only product mode. This pattern hasobvious shortcomings, among the same company’s product platform, combustion conceptsis inconsistent, also in plans. And development periods are long. As a result, engineers donot know the combustion system continues to the optimization of the potential how. ASimulation Guided Combustion System Lean Design(Correctitude Design)should be donearound three factors, Through the visual test and optical diagnosis for the necessaryphysical parameters and boundary conditions established as a numerical simulation modelof the initial data, engine numerical model is built to certain conditions comparing theresults of the numerical model and correction, satisfied after verification by usingnumerical simulation model of optimal design, so as to determine the engine combustionsystem design scheme. Preliminary design scheme implemented by a thermodynamicssingle cylinder engine test first, and the performance optimization is using a numericalmodel comparing with different operating modes, gradually approach the optimizing designgoal. The single cylinder engine test again after setting into the multi-cylinder engineproduct development stage, in a configuration all system accessories for the whole engineafter calibration.Optical diagnosis belongs to the non-contact measurement, to the testing area almostno interference, has the good time and space distinguishability, there has a very importantapplication value on soot and NOx generated diagnosis in cylinder. Endoscope system is akind of miniature optical image data acquisition system, the basic idea is to through a smalllens, the optical image will be transmitted from the fiber, and then the data records processis executing exteriorly. In the implement of engine is usually to drill a hole around thecombustion chamber and insert optical probe lens in it. The advantages of this method are: the engine changes small, and will not affect the internal structure of combustion chamber(compressed ratio loss is less than4%), so the air movement and burning effect changesvery little. In addition, endoscope system can bear high temperature、 high pressure andmany other intense combustion conditions in cylinder, collection is almost the sameconditions as thermodynamics engine combustion conditions of image data. And it’senough strength to be operated during a long time. To observe the real operating conditionsof engine work process in cylinder, especially suitable for the development of the engineproducts. Defect is: because lens size is small and the range between observed flame andlens is very near, so the eyeshot and wild-angle are restricted, at the same time there will beimage distortion.Based on the above of diesel engine test and burning development research concept,the test has established a set of AVL visioscope visual test system for optical test meanscarried out on a single cylinder D.I. diesel engine, and combining the method of two-colortemperature measurement theory, through Matlab as a computing platform, separately fromthe data acquisition, image quality evaluation, and then to combustion data analysis to be aseries of research. Tests include variable rail pressure、air intake pressure and swirl ratio,also EGR in cylinder visualization test. Specific research content and the results are asfollows:1. The test research has established a set of complete single cylinder diesel enginevisual combustion experimentation platform, the endoscopic optical platform based onsingle cylinder diesel engine, it includes electric power dynamometer system, air conditioncontrol system, coolant/lubrication control system and EGR control system, fuel injectioncontrol system, also include AVL Combustion analyzer, Horiba emission analyzer and incylinder optical acquisition system. This platform was closed to the thermodynamicproperties of metal engine, the engine changes exiguity, basic structure of internalcombustion chamber will not affect (compressed ratio loss is less than4%), the air flow andcombustion effect is changed exiguity, There are some characteristic, for example，canwithstand the higher cylinder pressure and etc. 2. In the study, use of Matlab as a basic platform of the calculation, set up withtwo-color temperature measurement method based on the theory of the cylindertemperature, temperature gradient distribution of combustion method. At the same time, tocollect the data of image quality was analyzed and evaluated. It formed a complete set ofvisualization methods, for diesel engine combustion analysis, it is both practical credible,and has the advanced instruction function.3. Use of established single cylinder engine visual test platform and calculationmethod, with A speed (1335r/min) as a standard speed. Respectively, rail pressure, air inletpressure, swirl ratio (are all variable), and EGR as four factors of visual test. Then the testdata are analyzed was obtained, and the regularity of the combustion process influenceconclusion.