Study On Combustion And Emissions Characteristics Of Lean-burn Gasoline Engine With Hydrogen Under Various Hydrogen Additional Ratio

With the rapid sustainable development of car industry in China, the wholeindustry is challenged by the energy crisis and the environmental pollution.To realize the goal of energy saving and emission reduction become the primarytask of any automobile enterprise. Being regarded as one of the cleanest energy,hydrogen is a new idea to develop alternative fuels. This thesis is supportedby National Natural Science Foundation ‘Study on Energy-saving Mechanism ofHEV Equipped with Lean-burn Gasoline Engine with Hydrogen Direct InjectionSystem’. The thesis analyzes the combustion and emissions characteristicsaccording to the experiment on lean-burn gasoline engine with hydrogen.Base on the advantages and disadvantages of lean-burn combustion andhydrogen engines, the experiment designed a scheme in order to realize bothadvantages about lean-burn emissions controlling and hydrogen combustion rateimproving. This thesis will verify the effect on lean-burn combustionperformances by the experiment.Firstly, the test need build up the engine test bunch to satisfy therequirement of experiment. Different from traditional engine, this test needstwo fuel supply systems with gasoline and hydrogen. Selecting WV EA888to beinitial engine, engine was installed an extra SPI system on air duct to supplygasoline. Our research group has developed the double fuels control system toaccurately control experimental parameters.The experimental variables are hydrogen additional ratio, spark advanceangle and excess air ratio. The thesis analyzes the effect of lean-burnperformances with different hydrogen additional ratio. This test collecteddata about in-cylinder pressure curve and heat release rate curve at the samespark advance angle. The results show that, with the increase of excess airratio, the in-cylinder pressure and rate of flame spread decreased. With theincrease of hydrogen additional ratio, this phenomenon has been improved. Themaximum explosion pressure and heat release rate are increased, mixture burnedmore completely. Hydrogen improve the lean-burn characters of gasoline engine because of its physical and chemical propertiesThe test find minimum spark advance for best torque (MBT) of differenthydrogen additional ratio and excess air ratio through changing spark advanceangle. On these spark advance angles, break mean effective pressure, torqueand power have the highest peak, Emission of HC is lowest. The test analyzesthe variation trends of the thermal efficiency, in-cylinder temperature andflame development and propagation periods. The results show that burning withhydrogen can improve the thermal efficiency, shorten flame development andpropagation periods, make the engine operation like constant volume combustionand decrease combustion loss.When hydrogen additional ratio arrived7.2%, engine can burn stably andkeep higher work performance under λ=2. With increasing hydrogen additionalratio, HC and CO emissions are both reduced, but the emission of NOx is increasedbecause of higher in-cylinder temperature. It can be controlled by increasedexcess air ratio.The experiment investigated engine work stability at lean conditions bycycle variations of maximum explosion pressure and effective pressure. Theresults show that, with increasing hydrogen additional ratio, cycle variationsof maximum explosion and effective pressure were both reduced, the engineworked more stabilized at lean conditions. Define10%of the cycle variationof the effective pressure as the excess air ratio to lean burn limit. The excessair ratio to lean burn limit extends is increased under hydrogen enrichment.