Experimental Investigation of the Effect of Pilot Fuel Injection Pressure and Start of Injection on Combustion and Emission of RCCI Engine fueled with Diesel-CNG

The main feature of RCCI is the significant reduction of nitrogen oxides and soot pollutants as efficiency and fuel consumption decrease. The aim of this study was to investigate the effects of the start of diesel fuel injection and injection pressure and two stage fuel injection strategies on RCCI combustion. The engine under investigation is a single cylinder engine with diesel fuel injection as high-reactivity fuel directly into the cylinder and natural gas fuel injection as low-reactivity fuel at the intake manifold. The start of injection, injection shape, and injection length in both injectors are controlled by the developed ECU. All tests were performed at an inlet air temperature of 37 ° C and the inlet pressure of 87kPa and 1800rpm. The results of this study show that by increasing diesel fuel injection pressure from 300 to 600 bar, at the 55 °BTDC start of injection, the ignition starts 2.5 degrees earlier and the in-cylinder maximum pressure and HRR increase by 0.66% and 2.68%, respectively. By delaying the start of diesel fuel injection by 6 degrees, we see a 12.37 % reduction in maximum in-cylinder pressure, and the start of ignition is delayed to 5 degrees. Increasing the spray pressure of diesel fuel increases NOx by 154 % and decreases UHC and CO by 32 and 57%, respectively. Increasing the diesel injection pressure increases NOx by 154 % and decreases UHC and CO by 32 and 57 %, respectively. On the other hand, the results of the two-stage injection of diesel fuel show that by postponing the first start of injection, the in-cylinder maximum pressure, HRR, IMEP, and NOx emission increase and UHC and CO decrease. Also, by postponing the second start of injection, the in-cylinder maximum pressure, HRR, IMEP and NOx emissions are reduce,d while UHC and CO increase

A Numerical Study on the impact of Purcell Effect and Spontaneous Emission Factor in Lower-Dimension Semiconductor Nanolasers

This paper presents a numerical approach to estimating the spontaneous emission coupling efficiency in semiconductor lasers with lower-dimension gain mediums. Also, the impact of the Purcell effect F and spontaneous emission factor β on the threshold and the height of the kink in the L-L curves is studied. Our theoretical calculations provide more insights into the laser behavior and help to optimize the laser cavity to achieve a lower threshold and higher coupling efficiency before fabrication

Availability analysis on combustion of n-heptane and isooctane blends in a reactivity controlled compression ignition engine

Unfortunately, energy demands and destruction of the environment from uncontrolled manipulation of fossil fuels have increased. Climate change concerns have resulted in the rapid use of new, alternative combustion technologies. In this study, reactivity controlled compression ignition (RCCI) combustion, which can simply be exploited in internal combustion (IC) engines, is investigated. To introduce and identify extra insightful information, an exergy-based study was conducted to classify various irreversibility and loss sources. Multidimensional models were combined with the primary kinetics mechanism to investigate RCCI combustion, incorporating the second law of thermodynamics. The n-heptane, a highly reactive fuel, was supplied by direct injection into the cylinder, whereas premixed fuel was supplied through the intake port in an isooctane/n-heptane RCCI engine. For five n-heptane increments (5%, 7.5%, 15%, 25%, and 40%) and six different exhaust gas recirculation (EGR) rates (0%, 10%, 20%, 30%, 40%, and 50%), accumulation of different exergy terms was calculated. The results show that as EGR introduction increases from 0% to 50%, the exergy destruction increases from 21.1% to 28.9%. Furthermore, the value of exhaust thermomechanical exergy decreases from 18.4% to 14.4% of the mixture fuel chemical exergy. Among the five different high reactive fuel mass regimes, the 40% n-heptane mass fraction has the major heat transfer exergy owing to its advanced CA50 that exerts a unique influence on cylinder charge temperature of heat transfer layer. The utilization efficiency of exhaust in RCCI is less affected by the variation of reactive fuel mass fraction by contrast; it will significantly influence heat transfer availability. This study revealed that with increasing reactive fuel (n-heptane) from 7.5% to 40% the irreversibility decreased from 28.6% to 25.8% and the second law efficiency first increased from 43.2% to 44.6% at 15% n-heptane then decreased to 42.9% at 40% n-heptane

Exposures of zebrafish through diet to three environmentally relevant mixtures of PAHs produce behavioral disruptions in unexposed F1 and F2 descendant

The release of polycyclic aromatic hydrocarbons (PAHs) into the environment has increased very substantially over the last decades. PAHs are hydrophobic molecules which can accumulate in high concentrations in sediments acting then as major secondary sources. Fish contamination can occur through contact or residence nearby sediments or though dietary exposure. In this study, we analyzed certain physiological traits in unexposed fish (F1) issued from parents (F0) exposed through diet to three PAH mixtures at similar and environmentally relevant concentrations but differing in their compositions. For each mixture, no morphological differences were observed between concentrations. An increase in locomotor activity was observed in larvae issued from fish exposed to the highest concentration of a pyrolytic (PY) mixture. On the contrary, a decrease in locomotor activity was observed in larvae issued from heavy oil mixture (HO). In the case of the third mixture, light oil (LO), a reduction of the diurnal activity was observed during the setup of larval activity. Behavioral disruptions persisted in F1-PY juveniles and in their offspring (F2). Endocrine disruption was analyzed using cyp19a1b:GFP transgenic line and revealed disruptions in PY and LO offspring. Since no PAH metabolites were dosed in larvae, these findings suggest possible underlying mechanisms such as altered parental signaling molecule and/or hormone transferred in the gametes, eventually leading to early imprinting. Taken together, these results indicate that physiological disruptions are observed in offspring of fish exposed to PAH mixtures through diet