Analysis of Low and High Temperature Heat Release in Dual-Fuel RCCI Engine and its Relationship with Particle Emissions

This study presents the influence of low-temperature heat release (LTHR) and high-temperature heat release (HTHR) on the combustion and particle number characteristics of the RCCI engine. The study investigates the relationship between the amount of LTHR, HTHR, and particle number emission characteristics. In this study, gasoline and methanol are used as low reactivity fuel (LRF), and diesel is used as a high reactivity fuel (HRF). The LRF is injected into the intake manifold using a port-fuel injection (PFI) strategy, and HRF is directly injected into the cylinder using a direct injection strategy. A particle sizer is used to measure particle emission in size ranging from 5 to 1000 nm. Firstly, the LTHR and HTHR are analyzed for different diesel injection timing (SOI) for RCCI operation. Later, the variation of particle emissions with LTHR and HTHR is characterized. Additionally, empirical correlations are developed to understand the relation between the LTHR and HTHR with particle emission. Two-staged auto-ignition of charge has been observed in RCCI combustion. Results depict that LTHR varies with diesel injection timing and the phasing of HTHR depends on the amount and location of LTHR. Results also showed that HTHR and LTHR significantly influence the formation of particle number concentration in RCCI combustion. The developed empirical correlation depicts a good correlation between diesel SOI and the ratio of HTHR to LTHR to estimate total particle number concentration.

Impact of Blow-By Gas and Endgap Ring Position on the Variations of Particle Emissions in Gasoline Engines

Particulate emission from internal combustion engines is a complex phenomenon that needs to be understood in order to identify its main factors. To this end, it appears necessary to study the impact of unburned gases, called blow-by gases, which are reinjected into the engine intake system. A series of transient tests demonstrate their significant contribution since the particle emissions of spark-ignition engines are 1.5 times higher than those of an engine without blow-by with a standard deviation 1.5 times greater. After analysis, it is found that the decanter is not effective enough to remove completely the oil from the gases. Tests without blow-by gases also have the advantage of having a lower disparity, and therefore of being more repeatable. It appears that the position of the “endgap” formed by the first two rings has a significant impact on the amount of oil transported towards the combustion chamber by the backflow, and consequently on the variation of particle emissions. For this engine and for this transient, 57% of the particulate emissions are related to the equivalence ratio, while 31% are directly related to the ability of the decanter to remove the oil of the blowby gases and 12% of the emissions come from the backflow. The novelty of this work is to relate the particles fluctuation to the position of the endgap ring.

CNC Edge Finishing of Granite: Effect of Machining Conditions on Part Quality, Cutting Forces, and Particle Emissions

Edge finishing is a shaping process that is extremely important in the granite and marble processing industries. It does not only shape the edge but also makes it shiny and durable. However, this process generates dust (fine and ultrafine particles) that can have a significant impact on air quality in the workshop and can put workers’ health at risk. While environmental requirements and occupational health and safety regulations are becoming increasingly stringent, at the same time, industries must continue to produce quality parts at competitive prices. The purpose of this study was to examine the surface quality, the cutting forces, and the emission of fine (FP) and ultrafine (UFP) particles during wet and dry edge finishing of granite edges as a function of the machining parameters and abrasive grit sizes. Three machining operations were investigated: roughing, semi-finishing, and finishing, using diamond abrasives (with grit sizes 45, 150, 300, 600, 1500, and 3000). The experiments were carried out on two granites, one being black and the other white. The tested spindle speeds ranged from 1500 rpm to 3500 rpm and the feed rates from 500–1500 mm/min. It was found that roughing operations produce more fine particles while finishing operations produce more ultrafine particles. These particle emissions, as well as the part quality and the cutting forces are strongly dependent on cutting speed and on the grit size of the abrasive used.