Characterization Of Bionic Anti-wear Surface For Pump Plunger And Design Of A Multi-channel Testing Platform

Petroleum is a non-renewable energy that is critical to the economy and safety ofour nation. Thus efficient exploitation of our oil resources is of great significance. It isestimated that more than80%of oil wells in China use sucker rod pump (SRP) to liftthe emulsion of crude oil and water from underground, which account for60%ofliquid extraction and75%of crude oil production on our nation’s oilfields as well asone third of the oilfield energy consumption. According to the data from ShengtuoOilfield of Sinopec, the wear between pump barrel and plunger caused200-250short-term failures of oil extraction annually, which lead to11.25%of failures ofmechanical oil-lifting wells with SRP and maintenance cost more than10millionRMB each year. Therefore it is crucial to improve the anti-wear property of pumpplunger, which will not only reduces maintenance cost, but also enhances oilproduction and brings more economical benefit to our oilfields.The wear of SRP mainly happens between the kinematic pair of pump barrel andplunger, which have both adhesive and abrasive wear. During the ideal workingmotion of the plunger, a thin layer of oil film will form between the barrel and theplunger, providing a lubrication medium. However, most of our oilfields are in theirlate-stage and the crude oil of such an oilfield usually contains a large amount ofwater and sand. High level of water can lead to less lubrication and more adhesivewear, which will be more prominent when the moving force between the barrel andthe plunger is unbalanced. Meanwhile, under the real working condition with highlevel of sand, sand can sneak into the gap between the barrel and the plunger, causingabrasive wear. More dangerously, if a sand bigger than the gap has been squeezed intothe gap, the pump could be stuck and failed. Although a great deal of efforts has beendedicated to reduce the adhesive and abrasive wear of SRP, the outcomes are stillundesirable.Bionics is a science that investigates the morphology, structure, composition andbehavior of natural organism to gain inspiration and mimic these characteristics inengineering. The laboratory has established the theory of bionic non-smooth surface, as well as a corresponding evaluation system, through the investigation ofrepresentative plants and animals with non-smooth morphology. Based on this theory,four kinds of bionic anti-adhesion and anti-friction parts and equipments, such asbionic non-smooth plough and bionic cultipacker, have been developed and applied toa variety of instruments for agriculture, construction, mining and power generation.In this thesis, earthworms and sandfish have been chosen as model animals togain insights about anti-wear and anti-friction properties. Four kinds of bionicnon-smooth test specimens, together with smooth test specimen, have been preparedand tested under three differently lubricated conditions (i.e., oil-submerged lubrication,oil-dropped lubrication, and no lubrication) to examine their anti-friction andanti-wear properties. Test specimens with various sizes of non-smooth morphologyhave also been assessed under non-lubricated condition. The friction coefficientduring wearing and the post-wearing weight loss and morphology have been collectedand analyzed for different specimens. It has been demonstrated that non-smoothsurface possesses better anti-wear and anti-friction properties than smooth surface.Besides, three-dimensional simulation of bionic non-smooth specimens and smoothspecimen has been created with ANSYS, a software for finite element analysis, toinvestigate the contact stress and equivalent stress for different specimens.Subsequently, an anti-wear and anti-friction mechanism has been proposed for bionicnon-smooth surface via both experimental and simulation approaches.In addition to the aforementioned work, a four-channel testing platform has beenset up to conduct wearing experiments of pump barrel and plunger. This testingplatform will not only save time and cost of plunger wearing experiments, but alsooffer better controllability and tunability. Thus it will provide a convenient tool for thefuture study of anti-wear and anti-friction properties of plungers with different bionicnon-smooth morphologies.