Search

In this study, the operating processes of a four-stroke diesel marine engine from the intake valve closing (IVC) to the exhaust valve opening (EVO) at numerous different charge air conditions were simulated with the AVL FIRE code. The CFD models were validated with engine shop-test technical data. The results showed that increasing the charge air pressure without cooling decreased the actual amount of air supplied to the cylinder. As a result, the combustion process was suboptimal, resulting in a reduction in engine power and an increase in specific fuel oil consumption (SFOC). In addition, less air to cool the combustion chamber coupled with elevated charge air temperatures increased the in-cylinder peak temperature, leading to a significant increase in thermal nitric oxide (NO) emissions. In contrast, by cooling the charge air after turbocharging, the actual amount of air entering the engine cylinders was increased. The abundant charge air helped to cool the combustion chamber better, significantly reducing the in-cylinder peak temperature and then the thermal NO formation. Better combustion also increased engine power, which, in turn, reduced SFOC. In addition, carbon dioxide (CO2) and soot emissions were also reduced. [ABSTRACT FROM AUTHOR]

Piston bowl geometry plays an important role in the fuel/air mixing quality which has a direct influence on the performance and emission characteristics of the engine. This work studied the effects of piston bowl geometry on the combustion and emissions of a four-stroke direct injection (DI) heavy-duty diesel marine engine. Three types of piston bowls with various parameters were numerically investigated, targeting to improve engine performance, fuel oil consumption, and emission characteristics. The results pointed out that the ω-type and re-entrant piston bowls enhanced cylinder power by 1.26% and 2.67% while reducing the indicated specific fuel oil consumption (ISFOC) of the engine by 1.06% and 1.60%, respectively, compared to the U-type bowl. Especially, the ω-type and re-entrant piston bowls reduced NO (nitric oxide) emission by up to 25.61% and 46.09%, respectively, owing to lower peak temperatures in comparison to the U-type piston bowl. The results also pointed out that changing the piston bowl type has negligible effects on the engine-out soot and CO2 emission characteristics of the engine. Based on this study, it is highly recommended to utilize the re-entrant piston bowl for four-stroke DI diesel engines to improve both engine performance and fuel oil consumption while reducing NO emission simultaneously. [ABSTRACT FROM AUTHOR]

This work studied the effect of the injector spray angle (SA) on the combustion and emissions of a 4-stroke port-injection natural gas-diesel dual-fuel (NG-Diesel DF) marine engine to determine the optimal SA for the fuel injector, aiming to reduce exhaust gas emissions while keeping the engine performance. Three-dimensional (3D) simulations of the combustion process and emission formations occurring in the engine cylinder in both diesel and DF modes were carried out using the AVL FIRE R2018a code. The engine's in-cylinder temperature, pressure, and emission characteristics were analyzed. To clarify the effect of the injector SA on the combustion and emission characteristics of the engine, only the injector SA has been varied from 145 to 160°. Meanwhile, all other boundary conditions for the simulations and operating conditions of the engine have remained unchanged. The simulation results have been compared and showed a good agreement with the engine experimental results. The study has successfully investigated the effects of the injector SA on the combustion and emission characteristics of the engine. A better SA for the fuel injector, to reduce the NO emissions (145°) or soot and CO2 emissions (150°), while keeping the engine power almost unchanged, without the use of any exhaust gas post-treatment equipment, has also been suggested. [ABSTRACT FROM AUTHOR]

This paper presents research on the combustion and emission characteristics of a four-stroke Natural gas–Diesel dual-fuel marine engine at full load. The AVL FIRE R2018a (AVL List GmbH, Graz, Austria) simulation software was used to conduct three-dimensional simulations of the combustion process and emission formations inside the engine cylinder in both diesel and dual-fuel mode to analyze the in-cylinder pressure, temperature, and emission characteristics. The simulation results were then compared and showed a good agreement with the measured values reported in the engine's shop test technical data. The simulation results showed reductions in the in-cylinder pressure and temperature peaks by 1.7% and 6.75%, while NO, soot, CO, and CO2 emissions were reduced up to 96%, 96%, 86%, and 15.9%, respectively, in the dual-fuel mode in comparison with the diesel mode. The results also show better and more uniform combustion at the late stage of the combustions inside the cylinder when operating the engine in the dual-fuel mode. Analyzing the emission characteristics and the engine performance when the injection timing varies shows that, operating the engine in the dual-fuel mode with an injection timing of 12 crank angle degrees before the top dead center is the best solution to reduce emissions while keeping the optimal engine power. [ABSTRACT FROM AUTHOR]

The rising human population is causing the utilization of enormous amounts of fossil fuels to fulfill energy needs. Various renewable sources are used as fossil fuels however those resources are not powerful in supplanting customary non-renewable energy sources like gasoline in vehicles. The depletion of conventional fossil fuel utilized in a vehicle contributes to an increased portion of air contamination and is a danger to human well-being. Also, to maintain the supply demand, many active types of research have been carried out in mixing a higher percentage of ethanol over gasoline and further moving towards flex-fuel vehicles. But there arises a problem of knocking and higher CO, and HC emissions from the engine. To overcome the above problem, ethanol could be mixed in a higher percentage over gasoline with the help of hydrogen assistance and can completely avoid the problem of knocking and reducing CO and HC emissions. In this research, the combustion, emission, and performance characteristics of a variable-speed gasoline engine fuelled with ethanol-blended gasoline along with hydrogen assistance are taken for investigation at variable speeds like 1800, 1600, 1400, and 1200 rpm. Hydrogen is added to blended fuel (E30) which has better combustion, emission, and performance than other blended fuels. Hydrogen addition is done at 2, 3, and 4 ms respectively. The outcomes showed that the E30 + H 2 at 3 ms has better combustion, emission, and performance, still, the emission of NOx is higher in comparison with all the other blends due to complete combustion. Thus, a two-stage analysis has been done, one is making a comparison among various blends of ethanol, and the second one is the comparison among the various energy shares of hydrogen. • Hydrogen injection timing variation at 2, 3, and 4 ms over the E30 fuel blend. • Hydrogen injecting strategy enhancing the usage of flex fuels in SI engine. • Split hydrogen and E30 fuel over port injection at the inlet manifold. • BTE was highest with E30 + H 2 at 3 ms and also the emissions were optimum. [ABSTRACT FROM AUTHOR]

In relative to traditional combustion, the reactivity-controlled compression ignition (RCCI) technique using fuels with different reactivity has gained significant interest because of its high thermal efficiency and low NOx and smoke emissions. Hence, the present work investigates the RCCI mode of operation in a light-duty diesel engine by introducing Cottonseed oil biodiesel as high reactivity fuel directly into the combustion chamber and n-pentanol as low-reactivity fuel intake. The experimental results revealed that NOx and smoke emissions were considerably decreased by 44.2% and 35.0% with RCCI mode of operation compared to Cottonseed oil biodiesel-based operation mode at 100% load condition. However, a significant rise in emissions of unburnt hydrocarbon (HC) and carbon monoxide (CO) was noted at medium load (50%) conditions in reactivity-controlled compression ignition mode but emissions of HC and CO tended to decrease at peak load conditions. Moreover, the engine's brake thermal efficiency was found to increase by 7% when operating under RCCI mode at 20% of the n-pentanol share, although a marginal reduction in brake thermal efficiency was recognized in the case of above 20% energy share at 100% engine load. Considering the combustion characteristics, the RCCI mode working on Cottonseed oil biodiesel/n-pentanol showed substantial improvement in peak pressure and heat release rate compared with the single-fuel mode. Overall, it has been identified that the operation of diesel engines on RCCI mode could result in a simultaneous reduction of smoke opacity (up to 21.2%) and NOx emission (up to 36%) and a marginal improvement in the engine performance. [Display omitted] • Reactivity-controlled compression ignition engine fuelled with biodiesel/n-pentanol. • 20% n-pentanol of energy share for reactivity-controlled mode as the optimum value. • Improved combustion and performance characteristics for reactivity-controlled mode. • Reducing 44.2% of nitrogen oxides and 35.0% of smoke opacity for the optimum mode. [ABSTRACT FROM AUTHOR]