Experimental Study On Combustion And Emission Characteristics Of Rotary Engine

Rotary engine is a kind of internal combustion engine with special structure.It has the advantages of compact structure,high ratio of power to weight,small vibration noise,etc.Therefore,it has wide application prospects in the military and civilian fields,but at the same time it has low thermal efficiency and high hydrocarbon emissions which have always been criticized by people.These problems are particularly acute in today’s increasingly serious energy crisis and environmental pollution problems.Therefore,it is particularly important to improve the combustion process of rotary engines.At present,there are relatively few experimental studies on the combustion process of the rotary engine.Therefore,it is of great significance to improve the economical efficiency and emission of the rotary engine by experimentally studying its combustion and emission characteristics.Firstly,this paper analyzed the reasons that lead to low thermal efficiency of the rotary engine and high hydrocarbon emissions,and it is clear that the focus of the research is the process of thermal power conversion.Then,the carburetor-type rotary engine was modified by electric injection,and the experimental bench for the combustion characteristics of the rotary engine was established.Based on this bench,the combustion characteristics were tested.The combustion data acquisition system was used to obtain the cylinder pressure data under different operating parameters.Based on the measured cylinder pressure data,the combustion heat release law was calculated to obtain the relevant combustion characteristic parameters.The highpressure cycle indicating thermal efficiency was calculated using the dynamometer diagram.On this basis,the influence of operating parameters on the combustion characteristics was analyzed.In addition,from the perspective of high-pressure cycle indicating thermal efficiency,the combustion characteristic parameters was pointed out which can evaluate the combustion process of rotary engine reasonably,thus indicating the direction for improving the thermal power conversion efficiency of the rotary engine,and providing a lot of data supporting for the positive development of the rotary engine.At the same time,the combustion emission characteristics and idle-cycle variation of gasoline-rotary engines under various ethanol blending ratios were studied,and the influence of ethanol blend ratio on the combustion and emissions of gasoline-rotary engines was revealed.Research indicates:(1)Properly increasing the ignition advance angle can shorten the combustion duration and increase the in-cylinder pressure.This is beneficial to increase the highpressure cycle indication thermal efficiency,but excessive ignition advance angle has a negative effect instead.Delaying the ignition will help to reduce the emissions of unburned HC and NOX,but this will also contribute to the sacrifice of power and economy to some extent.Under experimental conditions,the optimal ignition advance angle is 40 degrees before TDC.(2)Excessively lean mixture will delay the start of combustion and release heat,prolong the duration of combustion,and worsen combustion.A slightly lean mixture(An excess air ratio of 1.05)has the best fuel economy.HC emissions are at a minimum when the excess air ratio is 1.1,and both CO and NOx emissions increase with increasing excess air ratio.It is reasonable to evaluate the high-pressure cycle indicating thermal efficiency of the rotary engine with CA10-90.However,it is uncertain that the thermal efficiency is evaluated by CA0-10 and CA50.(3)When no adjustment is made to the original machine,the addition of ethanol to gasoline will reduce the cylinder pressure.In the case that the excess air ratio of the mixture is kept constant,blending a small proportion of ethanol in gasoline can increase the rate of combustion heat release,shorten the combustion duration,and reduce the HC,CO,NOx emissions and cycle variation at idle.A large proportion of ethanol blending results in an increase in NOx emissions and a cycle variation.When the blending ratio is 15%,it can not only perform better function,but also maintain low cycle variation and emissions.