• Energy Research

Abstract An experimental study on new high temperature parabolic trough collector (PTC), with transparent receiver tube, based on gas-phase nanofluid, has been carried out for the first time in this work. Two-axes solar tracking PTC, with 4 m 2 reflecting surface has been realized. Besides, two coaxial quartz tubes, with vacuum in the inner space were used as receiver pipe, with air-dispersed CuO nano-powders as working fluid. The aim of this work was to investigate the technological issues related to the use of gas-based nanofluid coupled with transparent quartz receiver and to evaluate the performance of the first prototype, comparing numerical and experimental results. The experimental campaign highlighted a critical issue related to nanopowder deposition within the receiver pipe, due to humidity. Moreover, in a day of measurement, the fluid temperature higher than 145 °C has been maintained for about 10 h, reaching a maximum value of 180 °C, with a mean efficiency of about 65%.

Abstract A study on particulate matter (PM) compound of a turbocharged gasoline direct injection (GDI) engine for different injection strategies has been performed. Particularly, morphology and structure of PM and soot produced by GDI engine were investigated as a function of injection rail pressure and start of injection before top dead center (SOI bTDC). The produced particulate matter and soot have been analyzed on a wide range of operating conditions by means of imaging and sampling techniques. To study the relationship between particulate morphology and engine working conditions, microscopic analyses (SEM and TEM) of several samples at the exhaust were performed. Therefore, these investigations were coupled with soot measurements before the catalyst and at the exhaust by means of a soot detector, able to measure the carbon component of particulate matter. Besides, the same measurements were compared with smoke opacity analyses to detect also the non-carbon components. The results demonstrated high influence of injection strategies on soot morphology-composition and on catalyst efficiency, revealing also a wear phenomenon of the piston under high pressure condition.