The Application Of Uniform Design In IC Engine Combustion Optimization

IC engines have been widely applied because of its good dynamic performance,high thermal efficiency and reliablity. However, the pressures of energy shortages andenvironmental protection have posed new challenge for the development of dieselengine. In order to meet the stringent emission regulations, and to realize thehigh-efficiency clean combustion, a variety of technical methods are needed in theengine’s integrated optimization process, especially for multi-parameters optimization.Although these methods are helpful for the improvement of thermal efficiency andemission reduction, the period and scale of optimization experiments are greatlyincreased.This paper puts forward a new engine optimization experiment design method:uniform optimization experiment design. This method combines uniform design withthe diesel engine combustion optimization experiments. The function relationshipbetween the experiment variables and the optimization target in limited test scale canbe found with this method. And then, the engine optimization work has been changedto a mathematical problem of nonlinear constraint function minimise, which meansthat a big part of engine experiment can be replaced by mathematical calculations.Therefore, the optimization efficiency can be greatly improvedThe uniform optimization method was applied to the optimization process of asingle-cylinder diesel engine operating with dual fuel in HPCC combustion mode.The relationship between the input variables, such as bio-diesel’s SOI, n-nutanolcalorific value proportion, EGR rate, and the target variables, such as indicatedthermal efficiency and NOx/soot emission was formulated by regression analysis. Theaccuracy and reliablity of the regression equation in limited conditions have beenvalidated/confirmed by the acutal engine experiments; A uniform experiment designwas also applied to the optimization process of a heavy diesel engine with EGR. TheSQP algorithm was used to solve the optimization problem, andthe optimizationschemes under different emission limits were obtained,which further verifies theaccuracy of the regression equation.After the validation process, the optimization experiment design method wasfurther applied to a heavy diesel engine with adjustable2-staged booster and EGR.The function relationship between fuel injection strategy,2-staged boosterby-pass valve position, EGR rate and fuel consumption, NOx/soot emissions underdifferent operating conditions were derived and analyzed. The GA algorithm was alsoapplied to solve the optimization problem, and the schemes which could meet theChina5th emission regulationwas proposed. The research results show that theuniform design method have practical guidance significance in complex engineexperiments.