Experimental Study On Engine Performance Of Nano-diesel Oil Combined With Heat Barrier Coating On Piston

The vast sea is an important place for maritime traffic and military activities.In order to ensure that China’s maritime interests are not harmed and safeguard the safety of China’s Marine environment,China has put forward the strategy of maritime power in recent years.Diesel engine has the characteristics of wide power coverage and high efficiency in the whole working range,and it is the most important power machinery for offshore ships.In order to respond to the strategic demand,further development of high-performance diesel engine has become an inevitable trend.In order to improve the performance of the engine,two specific measures are put forward:nano-diesel technology and thermal barrier coating technology.Nanoscale particles can be used as fuel additives due to their micro-size effect and surface effect,which can improve the atomization evaporation process during fuel injection,and effectively improve the combustion condition in the cylinder with its excellent thermal conductivity.The technology of thermal barrier coating can reduce the heat loss of diesel engine during combustion while reducing the load of heated parts,so that the combustion temperature and the maximum explosion pressure in the cylinder can be increased,and the engine performance can be further improved.However,the effect of a single technology on improving engine performance is limited to some extent.It is a prospective new approach to combine the two technologies and apply them to the engine.The effects of two technologies on the performance of WP-04 Marine diesel engine are studied by means of bench test and numerical simulation.Because there are many kinds of nanoparticles and coating materials,a large number of experimental tasks are required to complete the comparative analysis even if the orthogonal test method is adopted.Therefore,this paper adopts a two step method,that is,through certain theoretical analysis and preliminary exploratory tests,to select the nano-powder with better performance and the appropriate coating scheme.Finally,a bench test is carried out by combining the two techniques.The specific work content is as follows.Through consulting relevant literature,CeO₂ and Mo O₃ metal oxide nanoparticles were preliminarily selected to prepare 50mg/L,100mg/L and 150mg/L nanodiesels,respectively.With ordinary pure diesel as the control group,the influence of nano-particle materials and configuration concentration was analyzed through the platform test successively.According to the test results,150mg/L CeO₂ nano-diesel has the most obvious effect on engine performance improvement.Through relevant theoretical analysis,the selection scheme of coating was preliminarily drawn up.The simulation model of piston and top layer was built and analyzed in ANSYS software.The relevant boundary conditions are calculated from the test data of burning nano-diesel at rated engine conditions.The influence of thermal barrier coating on the heat load of piston and the combustion condition in cylinder is analyzed through the numerical changes of piston temperature field and thermal stress field.Finally,the spray coating on the top surface of piston was carried out,and finally the bench test of nano-diesel combined coating technology was completed.The influence of two technologies on diesel engine combustion characteristics and emission characteristics is emphasized.The results show that both nano-diesel technology and piston top coating technology can increase the maximum explosion pressure in the cylinder,improve the combustion condition in the cylinder,reduce fuel consumption and reduce CO emission.When the two technologies are applied together,the performance improvement effect is more obvious.In terms of NO_x emission,nano-diesel technology reduces its emission;thermal barrier coating technology rises its emissions.When acting together,there are different trends in low load and high load.