Numerical investigation on the impact of multiple injection strategies and spray included angles on combustion and emissions in a marine diesel engine

The computational fluid dynamical software AVL-FIRE code was used for investigating the impact of multiply injection strategies and spray included angles on combustion and emissions in a marine diesel engine. The fuel injection parameters of spray included angle and pilot injection timing with pilot-main injection, as well as post injection ratio and post injection duration angle with pilot-main-post injection, were all investigated and optimized. The results indicate that retarding pilot injection timing with pilot-main injection declines high temperature region, resulting in a notable reduction in NOx emissions. Since fuel evaporation and burn are hampered by long spray penetration due to low temperature and pressure with pilot injection, a suitable spray included angle are used to offer more efficient air-fuel mixing process. A wider spray included angle simultaneously reduces soot emission and indicated specific fuel consumption (ISFC). Post injection fuel exerts impact on combustion process by causing a great disturbance to flow field during post combustion. Increasing post injection ratio from 4% to 10% at a small post injection duration angle great emission performance is achieved by simultaneous reduction in NOx and soot emissions while only using a slight consumption of ISFC. To summarize, the defeat of traditional NOx-soot trade-off occurs as both NOx and soot emissions are decreased with optimized multiple injection strategy and spray included angle. Particularly, there are respectively four cases with pilot-main injection and two cases with pilot-main-post injection, that achieve simultaneous reduction in NOx emissions, soot emission, and ISFC, compared to the prototype.

Combustion performance investigation of aviation kerosene (RP-3) on a compression ignition diesel engine under various loads

The combustion performance of a compression ignition (CI) four-stroke aviation engine fueled with pure No. 3 rocket propellant (RP-3) was experimentally investigated for comparison with diesel. Pilot injection and main injection for RP-3 and diesel were unified under same test conditions. The results show that when burning RP-3, the maximum power of engine is 1% lower than that of burning diesel, with lower specific fuel consumption (SFC) and effective thermal efficiency (ETE). The combustion durations of RP-3 and diesel show small differences of less than 0.4°CA under heavy loads, while the combustion duration of RP-3 is shorter than that of diesel under low loads. The crank angle at 50% mass fraction burnt (CA50) of RP-3 shows differences of 0.3-1°CA compared to that of diesel. For pilot injection at a high engine speed, the ignition delay angle (IDA) of RP-3 is basically equal to that of diesel. With decreasing engine speed, the maximum difference of 1.2°CA in IDAs exist under medium or small loads. For the main injection, the IDA of RP-3 is lager than diesel under heavy loads at various engine speeds. As the load decreases, the IDA of RP-3 is extended. The peak heat release rate (HRR) of RP-3 during main injection combustion is basically the same as diesel under heavy loads, while the intervention effect of unburnt pilot-injected RP-3 under low loads results in a higher peak HRR.

Development of optimal diesel injection strategy based on the prediction of performance and emissions using deep neural network

This study aims to determine the optimal injection strategy by predicting the performance and exhaust emission parameters of a four-cylinder CRDI engine under several operating conditions. The experimental determination procedure is challenging and expensive calibration task since it requires a high number of tests. Many studies have focused on a limited level of parameters. In this study, design of experiments technique and deep neural network (DNN) modeling are used together. The experimental data set for the model is created using Taguchi L16 and L32 orthogonal arrays. The DNN model is developed to predict [Formula: see text], [Formula: see text], HC, and CO emissions with speed, torque, injection timings and fuel quantities of each injection called as pilot1, pilot2, main, and post. In this way, it has become possible to evaluate the effects of a larger number of operating parameters in a wide range than the literature. The developed DNN model predicts the [Formula: see text], [Formula: see text], HC, and CO with R2 0.939, 0.943, 0.963, and 0.966, respectively. Additionally, RMSE and MAE values for the model are between 0.024 and 0.048. The proposed method compared with the conventional look-up table method performs better in reducing the complexity and cost of experiments and exploration of the effects of injection parameters on engine emission and performance characteristics in a wide engine operating range. In conclusion, until 2300 rpm at specified torque (90 Nm), it is found that 70% of fuel quantity should inject in main injection to minimize [Formula: see text] and [Formula: see text] emissions. The post injection quantity should be increased by reducing the amount of main injection from this operating condition on. Furthermore, it is observed that the ratios of pilot injection durations do not change with increasing engine speed, but quantity of first pilot injection is more than that of second pilot injection.

Multiple-objective optimization of heavy-duty compression ignition engine fueled by gasoline/hydrogenated catalytic biodiesel blends at low loads

Multiple-objective optimization of a heavy-duty compression ignition engine fueled by gasoline/hydrogenated catalytic biodiesel (HCB) blends at low loads was performed by employing the KIVA-3V code and genetic algorithm. In addition, the mechanism of multiple-injection and sensitivity of operating parameters on engine performance of the optimal cases were also explored. The results indicated that efficient combustions for G70H30 (70% gasoline and 30% HCB) and G100 (pure gasoline) with ultra-low nitrogen oxides (NOx) and soot emissions could be obtained after optimization. As HCB fraction increases, the ranges of operating parameters become more extensive, and the required initial temperature for optimal cases can be effectively reduced. When the main injection occurs after the ignition caused by pilot injection, main injection moderates the heat release rate (HRR) by creating concentration and temperature stratifications in the spray area simultaneously, and the exhaust gas recirculation (EGR) rate, pilot, and main start of injections and pilot fraction play dominant roles on engine performance. Moreover, when main injection is much more advanced than the ignition timing, main injection controls the HRR only through the concentration stratification in the reaction zone, and the EGR rate, initial temperature, and pilot faction have dominated effects on engine performance.

Effects of Different Injection Strategies on Combustion and Emission Characteristics of Diesel Engine Fueled with Dual Fuel

In this work, an effective numerical simulation method was developed and used to analyze the effects of natural gas mixing ratio and pilot-main injection, main-post injection, and pilot-main-post injection strategies on the combustion and emission characteristics of diesel engine fueled with dual fuel. Firstly, the one-dimensional calculation model and three-dimensional CFD model of the engine were established by AVL-BOOST and AVL-Fire, respectively. In addition, the simplified chemical kinetics mechanism was adopted, which could accurately calculate the combustion and emission characteristics of the engine. The results show that the cylinder pressure and heat release rate decrease with the increase of the natural gas mixing ratio and the NOx emission is reduced. When the NG mixing ratio is 50%, the NOx and CO emission are reduced by 47% and 45%, respectively. When the SODI3 is 24 °CA ATDC, the NOx emission is reduced by 29.6%. In addition, with suitable pilot-main injection and pilot-main-post injection strategies, the combustion in the cylinder can be improved and the trade-off relationship between NOx and soot can be relaxed. Thus, the proper main-post injection strategy can improve the combustion and emission characteristics, especially the reduction in the NOx and CO emissions.

Effect of Injection System Parameters on Performance and Emission Characteristics of a Small Single Cylinder Diesel Engine

Limited fossil fuel reservoir capacity and pollution caused by them is the big problem in front of researchers. In the present paper, an attempt was made to find a solution to the same. The conventional fuel injection system was retrofitted with a simple version of the common rail direct injection system for the small diesel engine. Further, the effect of injection system parameters was observed on the performance and emission characteristics of the retrofitted common rail direct injection diesel engine. The parameters such as injection pressure, the start of pilot injection timing, the start of main injection timing and quantity of percentage fuel injection during the pilot and main injection period were considered for experimental investigation. It was observed that all the evaluated parameters were found vital for improving the engine’s performance and emission characteristics. The retrofitted common rail direct injection system shows an average 7% rise in brake thermal efficiency with economic, specific fuel consumption. At the same time, much more reduction in hydrocarbon, carbon monoxide and smoke opacity with a penalty of a slight increase in nitrogen oxides.

Modeling of post-injection strategies of ethanol and experimental analysis of the use of ethanol in the form of dual fuel and emulsion in diesel engine

In this research, as the first stage, the effects of the ethanol on engine performance and emissions under the fumigation and emulsion method were experimentally investigated under part load and various engine speed conditions. Diesel-ethanol blend containing 5% ethanol by volume was used as the mixture fuel. In the fumigation method, ethanol was used at the same rate and 99.9% purity as the emulsion method. As the second stage, the effects of ethanol post injection on engine performance and pollutant emissions were investigated in the experimental engine modeled in AVL Boost simulation program and compared with the experimental results. Simulation post injection tests were performed separately after the main injection at 3 CA (P1) and 7 CA (P2) crank angles. In the experimental studies, NOx emission decreased with the emulsion method (E5) at low and high engine speeds. In post injection strategies, NOx emission in general increased due to improved combustion and increased in-cylinder temperature with P1 (first post injection) and P2 (second post injection) strategies. Soot emission decreased significantly with E5. This improvement in soot emissions was approximately 87% in post injection strategies.