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Porous fouling layers formed by particulate deposition in the EGR cooler tubes degrade the cooling efficiency of the EGR coolers. This research has investigated the changes of the particulate concentration under varied coolant temperature conditions and the effects of the coolant temperature on the cooling efficiency of the cooler tubes by measuring the particulate concentration and size distribution at the cooler inlet and outlet. The experiment results indicate that for the particulates of different sizes, the thermophoretic force acting on them and the regeneration vary under the same experiment conditions, presenting distinctive effects on the particulate concentration distribution in the exhaust gas and causing concentrations of nuclear particulates and aggregated particulates to change, respectively. The mass of fouling layers inside the cooler tubes increases as the coolant temperature decreases. Decreasing the coolant temperature not only increases the quantity of fouling particulates but also forms more particulates of big sizes, causing cooling efficiency of the cooler tube per unit length to decrease with the decrease of coolant temperature and the increase of the tube length.

This paper summarizes a study based on a modified, light, single-cylinder diesel engine and the effects of the physicochemical properties for n-butanol-diesel blended fuel on the combustion process and hydrocarbon (HC) emissions in the intake at a medium speed and moderate load in, an oxygen-rich environment (Coxy = 20.9&ndash, 16%), an oxygen-medium environment (Coxy = 16&ndash, 12%), and an oxygen-poor environment (Coxy = 12&ndash, 9%). The results show that the ignition delay period is the main factor affecting the combustion process and it has a decisive influence on HC emissions. In an oxygen-medium environment, combustion duration affected by the cetane number is the main reason for the difference in HC emissions between neat diesel fuel (B00) and diesel/n-butanol blended fuel (B20), and its influence increases as the intake oxygen concentration decreases. In an oxygen-poor environment, in-cylinder combustion temperature affected by the latent heat of vaporization is the main reason for the difference in HC emissions between B00 and B20 fuels, and its influence increases as the intake oxygen concentration decreases. By comparing B20 fuel with diesel/n-butanol/2-ethylhexyl nitrate blended fuel (B20 + EHN), the difference in the ignition delay period caused by the difference in the cetane number is the main reason for the difference in HC emissions between B20 and B20 + EHN fuels in oxygen-poor environment, and the effect of this influencing factor gradually increases as the intake oxygen concentration decreases.

Initial temperature has a promoting effect on laminar burning velocity, while initial pressure and dilution rate have an inhibitory effect on laminar burning velocity. Equal laminar burning velocities can be obtained by initial condition coupling with different temperatures, pressures and dilution rates. This paper analysed the equivalent distribution pattern of laminar burning velocity and the variation pattern of an equal weight curve using the coupling effect of the initial pressure (0.1–0.3 MPa), initial temperature (323–423 K) and dilution rate (0–16%). The results show that, as the initial temperature increases, the initial pressure decreases and the dilution rate decreases, the rate of change in laminar burning velocity increases. The equivalent effect of initial condition coupling can obtain equal laminar burning velocity with an dilution rate increase (or decrease) of 2% and an initial temperature increase (or decrease) of 29 K. Moreover, the increase in equivalence ratio leads to the rate of change in laminar burning velocity first increasing and then decreasing, while the increases in dilution rate and initial pressure make the rate of change in laminar burning velocity gradually decrease and the increase in initial temperature makes the rate of change in laminar burning velocity gradually increase. The area of the region, where the initial temperature influence weight is larger, gradually decreases as the dilution rate increases, and the rate of decrease gradually decreases.