Research On Compatibility Of Engine Seal Materials With DME

Reductions in fuel consumption and engine emissions are two majorobjectives in engine department. Development of Alternative fuels forautomobile is one of the most important challenges that we have to face.Because of excellent characteristic of Dimethyl Ether, high thermalefficiency and low emission can be achieved when compression ignitionengine fuelled with it. For widely use of DME can improve domesticallyenergy structure, it has been increasing concerned by people recently.However, its low lubrication ability and rubber material compatibility aretwo main problems we have to solve before DME can be widely used asengine fuel.Under the support of National Natural Science Foundation of China,we conduct the research on seal materials. The main aim of this thesis isto develop elastic sealing materials for engine fuelled with DME. Thecompatibility of many kinds of rubber materials with DME was deeplyinvestigated.1. The resistance of4categories of rubber materials to DME wasexperimentally studied. The volume change rate of FEPM and HNBRrubber materials are up to191.5%and98.1%, so the two kinds ofrubber materials are not suitable to be used as seal materials of DMEengine. The volume change rate of EPDM rubber is24.8%and themass change is6.9%. Both the variations are the smallest among allthese experimental rubber materials. Experimental data showed thatEPDM had good resistance to DME and can be considered as therubber seal material.2. Using orthogonal design method, the resistance of EPDM rubbers isexperimentally tested. The aim is to choose one kind of EPDM withgood resistance to fuel DME. The raw rubber system, plasticizersystem and reinforcing filling system as the three factors oforthogonal tests. Each factor has3levels and without interactions each other. We evaluated the resistance of EPDM rubbers to DMEthough Volume Swelling Rate, Mass Change Rate and MechanicalPerformance of EPDM rubbers after immersion in DME for72h.3. The experiment results of EPDM components on the compatibility tofuel DME were orthogonally analyzed. The results revealed thatrubber raw materials are the most important factor influencing thecompatibility and different components of same kind of rubber havedifferent properties. EPDM rubbers with A1raw rubber system haveexcellent mechanical properties; EPDM rubbers with A2raw rubbersystem have the minimum volume swelling rate; EPDM rubbers withA3raw rubber system have the minimum permanent mass loss rate.In this study, plasticizer system and reinforcing filling system have nosignificant effect on the resistance of EPDM rubbers to DME. Basedon the experimental results, technical requirements of rubber sealingmaterials for vehicles fuelled with DME were given.4. The chosen EPDM rubber compatibility to fuel DME containingmethanol and water was experimented and analyzed. The resultsshowed that methanol and water caused small change rate of volumeswelling and mass loss. We can consider that the both componentshave little effects on the rubber sealing materials.5. The chosen EPDM rubber compatibility to blend of DME andlubricate additives was conducted. The effect of categories andcontents of the additives on rubber sealing performance. The resultsdemonstrated that different additives categories have differentinfluence. Volume swelling rate of the chosen EPDM rubber is biggerwhen immersed in DME with additives than that without additives,and the higher additive contents, the bigger volume swelling rate. Theexperiment of mass loss rate showed that there were no obviousdifferences between the fuel DME with and without additive.6. Research of chosen EPDM rubber resistance to diesel is conducted.Under current technical and economical conditions, the influence ofdiesel on rubber sealing materials should be considered when usingdiesel to adjust the uniformity of high-pressure fuel pump. The resultsshowed that the chosen EPDM rubber had acceptable volume swelling rate and mechanical performance when the time is no morethan3hours.This study properly solved the problems of rubber materialcompatibility, develop a new rubber sealing material which can beapplicable to vehicles fuelled with DME and made a contribution to thereliability of DME engine.