The Heat Transfer Enhancement Mechanism And Experimental Research Of Cryogenic Air Atomizing Nanofluids For Minimal Quantitie Lubrication Titanium Alloy

Grinding is a typical method of machining,grinding heat and grinding force will be produced in grinding process.Especially for titanium alloy and other difficult to grinding materials,due to small thermal conductivity material,h eat can not be effectively transmitted to the workpiece matrix,and accumulated in the contact interface between the grinding wheel and the workpiece.The over high grinding temperature will make the Ti element react with the grinding wheel easily,leading to rapid wear of the grinding wheel,and the high grinding force will also lead to the plastic deformation of the grinding wheel.Therefore,it is very important to provide an effective cooling and lubricating medium to the grinding area." Made in China 2025 " and " 13 th Five-Year " advanced manufacturing technology are clearly put forward green manufacturing projects as one of the key construction projects,low-carbon manufacturing has been imperative.Nanofluid minimum quantity lubrication(NMQL)as a green environment of grinding fluid supply,many scholars have done a lot of research on it.However,there are still some technical bottlenecks in NMQL.When grinding difficult to machine materials,the phenomenon of grinding burn still exists.The cryogenic air cooling technology has been widely used in the metal processing,although the cryogenic air have a strong heat exchange ability,but its lubrication is poor,the quality of the workpiece is difficult to be guaranteed.It is possible to further improve the convective heat transfer capability of nanofluids by drawing on the cryogenic air heat transfer capability and the excellent anti-wear and friction reducing properties of nanofluids.In view of this,this paper presents a method that use high-speed cryogenic air instead of nanofluids minimum quantity lubrication methods of compressed air at room temperature,high-speed cryogenic air by forced convection to cool down the workpiece temperature and remove debris and effect of nanofluids by its good antifriction properties has excellent lubricating effect.This article main research content is as follows:(1)Based on the analysis of grinding mechanism of workpiece material,the model of grinding heat generation,heat transfer model and energy distribution model are established.The grinding performance parameters were studied.(2)The grinding mechanism of titanium alloy under different working conditions was analyzed.The grinding parameters are designed by the orthogonal experiment method.The grinding performance parameters were analyzed by signal-to-noise and grey relational grade analysis,the better grinding experimental parameters are obtained.Then,the optimal grinding parameters were obtained from the aspects of the surface profile support ratio,the microstructure of the workpiece surface,the material removal parameter value and the grinding energy,and so on.(3)The experimental platform of cryogenic air atomizing nanofluids minimum quantity lubrication(CNMQL)is constructed.Based on the ambient gas refrigeration device,minimum quantity lubrication supply device,control device and gas flow distribution of oil and gas mixed atomization nozzle design,from the principle of innovation and the structure is improved,the experimental platform was completed.(4)The grinding mechanism of CNMQL was studied,and compared with cryogenic air and NMQL two traditional cooling lubrication methods,from the analysis of the grinding temperature,grinding force,surface roughness,surface morphology and debris morphology of characterization parameters of grinding performance.It is proved by experiments that CNMQL is a better way of cooling and lubrication.(5)The mechanism of heat transfer enhancement in CNMQL was studied.A boiling heat transfer model and a temperature field model were established.The boiling heat transfer coefficient is calculated by linear interpolation method,and the temperature field is modeled and simulated by finite difference method.The simulation temperature is compared with the experimente,the rationality of the model is verified.And to further analysis the micro morphology of workpiece and debris interface in CNMQL.The conditions of capillary phenomena at the interface between abrasive grains and workpiece,the interface between abrasive and debris were confirmed.