Blow-by and tribological performance of piston ring pack during cold start and warm idle operations

To reduce the fuel consumption of internal combustion engines, more attention has been paid to the tribological performance of the piston ring pack during the cold start and idle operations. In this research, a numerical model considering the cylinder liner deformation and the piston ring conformability is developed to predict the blow-by, lubrication, friction and wear of the piston ring pack under different operating conditions. The gas flow rate, inter-ring gas pressures, minimum oil film thickness, frictional force and wear load during cold start are calculated and compared with those during warm idle operating conditions. The results show that cylinder liner deformation and piston ring conformability together obviously affect blow-by and other tribological performance. Meanwhile, it is found that friction loss is larger during cold start than during warm idle operating conditions. However, the wear process is more severe during warm idle operation than during cold start. From this research, the blow-by and tribological performance of the piston ring pack during cold start and warm idle operations are understood more deeply.

Drug delivery interfaces:A way to optimize inhalation therapy in spontaneously breathing children

There are several different types of drug delivery interfaces available on the market.Using the right interface for aerosol drug delivery to children is essential for effective inhalation therapy.However,clinicians usually focus on selecting the right drug-device combination and often overlook the importance of interface selection that lead to suboptimal drug delivery and therapeutic response in neonates and pediatrics.Therefore,it is necessary to critically assess each interface and understand its advantage and disadvantages in aerosol drug delivery to this patient population.The purpose of this paper is to provide a critical assessment of drug delivery interfaces used for the treatment of children with pulmonary diseases by emphasizing advantages and problems associated with their use during inhalation therapy.

Explanation of the mechanisms of unsteady gas flow through the turbocharger seal system,including thermal and structural interactions

Gas flow in the seal system can be expected during the operation of a turbocharger and is associated with negative effects on the quality of the lubricant or turbocharger efficiency.Gas flow also affects particulate matter production due to lubricant entrainment in the compressor or turbine.The prediction of gas flow rates depends on many design parameters and the operating conditions of the turbocharger,but sufficiently accurate descriptions of the gas flow mechanisms and their quantification depending on the operating conditions have not yet been presented.The proposed computational approach simultaneously solves the gas dynamics in the seal system,the heat transfer in the turbocharger rotor-bearing system and the dynamics of the seal rings and rotor,including the bearings.The computational model for the turbocharger of a heavy-duty vehicle engine is experimentally validated.Two mechanisms have major influences on gas mass flow:the gas flow through the thin gap between the moving ring and groove and the flow through the ring gap.The results show that the importance of these mechanisms depends on several geometrical dimensions of the seal system and the operating conditions of the turbocharger,with a strong connection to the rotor dynamics and thermal load of the impellers.Influences involving rotor movement or rotor thermal conditions are crucial,and their non-inclusion limits the ability to correctly predict gas mass flow.