Ab-Initio Molecular Dynamics Simulation of the Electrolysis of Nucleobases

Electrolysis is potentially a valuable tool for cleansing waste water. One might even hope that it is possible to synthesize valuable products in this way. The question is how the reaction conditions can be chosen to obtain desired compounds. In the present study we use Car–Parrinello molecular dynamics to simulate the reaction of nucleobases under electrolytic conditions. We use our own scheme (F. Hofbauer, I. Frank, Chem. Eur. J., 18, 277, 2012) for simulating the conditions after the electron transfer in a self-consistent field calculation. This scheme was employed previously to the electrolysis of pure water and of polluted solutions. On the picosecond timescale, we find a strongly different reaction behavior for each of the four nucleobases contained in DNA

A comprehensive study of effective parameters on the thermal performance of porous media micro combustor in thermo photovoltaic systems

Low thermal performance is one of the biggest challenges of using micro combustor in Thermo-photovoltaic (TPV) system. In this study, a novel micro-combustor with porous media was designed and installed to enhance energy and exergy performance. Furthermore, the effects of several effective parameters including different porous media materials, length, porosity coefficient, and inlet mass flow on energy efficiency, exergy, entropy generation, wall temperature and its uniformity were studied. A comprehensive CFD model for using porous media in the micro-combustor of TPV systems was proposed. Results showed utilizing porous media significantly improve the exergy efficiency and energy output of TPV system. Therefore, using a 6 mm long porous media increased the average wall temperature by 111 K compared to the case without porous media. Additionally, the uniformity coefficient of the wall temperature decreased by 80.05 %, from 4.58 % to 0.89 %. This reduction increased the temperature uniformity of the outer wall of the micro-combustor with porous media compared to the case without a media, increasing the system’s lifetime. Moreover, the 6 mm-long porous media enhanced radiation efficiency and exergy efficiency by 37 % and 79.7 %, respectively, compared to the conventional micro combustor. The total energy conversion efficiency from the fuel chemical energy to electric power increased from 8.9 % to 12.32 %.<br/

A comprehensive study of effective parameters on the thermal performance of porous media micro combustor in thermo photovoltaic systems

Low thermal performance is one of the biggest challenges of using micro combustor in Thermo-photovoltaic (TPV) system. In this study, a novel micro-combustor with porous media was designed and installed to enhance energy and exergy performance. Furthermore, the effects of several effective parameters including different porous media materials, length, porosity coefficient, and inlet mass flow on energy efficiency, exergy, entropy generation, wall temperature and its uniformity were studied. A comprehensive CFD model for using porous media in the micro-combustor of TPV systems was proposed. Results showed utilizing porous media significantly improve the exergy efficiency and energy output of TPV system. Therefore, using a 6 mm long porous media increased the average wall temperature by 111 K compared to the case without porous media. Additionally, the uniformity coefficient of the wall temperature decreased by 80.05 %, from 4.58 % to 0.89 %. This reduction increased the temperature uniformity of the outer wall of the micro-combustor with porous media compared to the case without a media, increasing the system’s lifetime. Moreover, the 6 mm-long porous media enhanced radiation efficiency and exergy efficiency by 37 % and 79.7 %, respectively, compared to the conventional micro combustor. The total energy conversion efficiency from the fuel chemical energy to electric power increased from 8.9 % to 12.32 %.<br/

Effects of ammonia on combustion, emissions, and performance of the ammonia/diesel dual-fuel compression ignition engine

Ammonia is currently receiving more interest as a carbon-free alternative fuel for internal combustion engines (ICE). A promising energy carrier, easy to store and transport, being liquid, and non-carbon-based emissions which make ammonia a green fuel to decarbonize ICE and to reduce greenhouse gas (GHG) emissions. This paper aims to illustrate the impacts of replacing diesel fuel with ammonia in an ammonia/diesel dual fuel engine. Hence, the effects of various ammonia diesel ratios on emissions and engine performance were experimentally investigated. In addition, a developed 1D model is used to analyze the combustion characteristics of ammonia and diesel. Results show 84.2% of input energy can be provided by ammonia meanwhile indicated thermal efficiency (ITE) is increased by increasing the diesel substitution. Moreover, increasing the ammonia energy share (AES) changed the combustion mode from diffusion combustion in pure diesel operation to premixed combustion in dual fuel mode. Therefore, combustion duration and combustion phasing decreased by 6.8CAD and 32CAD, respectively. Although ammonia significantly reduced CO2, CO, and particulate matter (PM) emissions, it also increased NOX emissions and unburned ammonia (14800 ppm). Furthermore, diesel must be replaced with more than 35.9% ammonia to decrease GHG emissions, since ammonia combustion produces N2O (90 ppm) that offsets the reduction of CO2.<br/

Effects of ammonia on combustion, emissions, and performance of the ammonia/diesel dual-fuel compression ignition engine

Ammonia is currently receiving more interest as a carbon-free alternative fuel for internal combustion engines (ICE). A promising energy carrier, easy to store and transport, being liquid, and non-carbon-based emissions which make ammonia a green fuel to decarbonize ICE and to reduce greenhouse gas (GHG) emissions. This paper aims to illustrate the impacts of replacing diesel fuel with ammonia in an ammonia/diesel dual fuel engine. Hence, the effects of various ammonia diesel ratios on emissions and engine performance were experimentally investigated. In addition, a developed 1D model is used to analyze the combustion characteristics of ammonia and diesel. Results show 84.2% of input energy can be provided by ammonia meanwhile indicated thermal efficiency (ITE) is increased by increasing the diesel substitution. Moreover, increasing the ammonia energy share (AES) changed the combustion mode from diffusion combustion in pure diesel operation to premixed combustion in dual fuel mode. Therefore, combustion duration and combustion phasing decreased by 6.8CAD and 32CAD, respectively. Although ammonia significantly reduced CO2, CO, and particulate matter (PM) emissions, it also increased NOX emissions and unburned ammonia (14800 ppm). Furthermore, diesel must be replaced with more than 35.9% ammonia to decrease GHG emissions, since ammonia combustion produces N2O (90 ppm) that offsets the reduction of CO2.<br/

Ammonia CI engine aftertreatment systems design and flow simulation

Investigation of exhaust emissions and ammonia flow behavior in the exhaust system incorporating with Selective Catalytic Reduction (SCR) unit is discussed. An aftertreatment system is designed to work without additional urea injection to improve feasible temperature of operating and reduce size. This study is focused on obtaining optimal parameters for catalysis using gaseus ammonia as reducing agent. Its effectiveness is considered as a function of basic parameters of exhaust gases mixture and SCR material characteristics. A 3D geometry of SCR with porous volume has been simulated using Ansys Fluent. Moreover, a 1D model of ammonia dual-fuel CI engine has been obtained. Results were focused on obtaining local temperature, velocity, and exhaust gases composition to predict optimal probes placement, pipes insulation parameters, and characteristic dimensions

Ammonia CI engine aftertreatment systems design and flow simulation

Investigation of exhaust emissions and ammonia flow behavior in the exhaust system incorporating with Selective Catalytic Reduction (SCR) unit is discussed. An aftertreatment system is designed to work without additional urea injection to improve feasible temperature of operating and reduce size. This study is focused on obtaining optimal parameters for catalysis using gaseus ammonia as reducing agent. Its effectiveness is considered as a function of basic parameters of exhaust gases mixture and SCR material characteristics. A 3D geometry of SCR with porous volume has been simulated using Ansys Fluent. Moreover, a 1D model of ammonia dual-fuel CI engine has been obtained. Results were focused on obtaining local temperature, velocity, and exhaust gases composition to predict optimal probes placement, pipes insulation parameters, and characteristic dimensions

Effects of using ammonia as a primary fuel on engine performance and emissions in an ammonia/biodiesel dual-fuel CI engine

Ammonia is a promising alternative fuel that can replace current fossil fuels. Hydrogen carrier, zero carbon base emissions, liquid unlike hydrogen, and can be produced using renewable resources, making ammonia a future green fuel for the internal combustion engine. This study aims to show the procedure of utilizing ammonia as a primary fuel with biodiesel in a dual-fuel mode. Hence, a single-cylinder diesel engine was retrofitted to inject ammonia into the intake manifold, and then a pilot dose of biodiesel is sprayed into the cylinder to initiate combustion of the premixed ammonia-air mixture. The effects of various ammonia mass flow rates with a constant biodiesel dose on engine performance and emissions were investigated. Furthermore, a one-dimensional model has been developed to analyze the combustion of ammonia and biodiesel. The results reveal that 69.4% of the biodiesel input energy can be replaced by ammonia but increasing the ammonia mass flow rate slightly decreases the brake thermal efficiency. Moreover, increasing the ammonia load contribution significantly reduced the emissions of CO2, CO, and HC but increased the emission of NO. It was found that ammonia delayed the start of combustion by 2.6CAD compared with pure biodiesel due to the low in-cylinder temperature and the high resistance of ammonia to autoignition. However, the combustion duration of biodiesel/ammonia decreased 19CAD compared with only biodiesel operation at full load, since most of the heat was released during the premixed combustion phase

Effects of using ammonia as a primary fuel on engine performance and emissions in an ammonia/biodiesel dual-fuel CI engine

Ammonia is a promising alternative fuel that can replace current fossil fuels. Hydrogen carrier, zero carbon base emissions, liquid unlike hydrogen, and can be produced using renewable resources, making ammonia a future green fuel for the internal combustion engine. This study aims to show the procedure of utilizing ammonia as a primary fuel with biodiesel in a dual-fuel mode. Hence, a single-cylinder diesel engine was retrofitted to inject ammonia into the intake manifold, and then a pilot dose of biodiesel is sprayed into the cylinder to initiate combustion of the premixed ammonia-air mixture. The effects of various ammonia mass flow rates with a constant biodiesel dose on engine performance and emissions were investigated. Furthermore, a one-dimensional model has been developed to analyze the combustion of ammonia and biodiesel. The results reveal that 69.4% of the biodiesel input energy can be replaced by ammonia but increasing the ammonia mass flow rate slightly decreases the brake thermal efficiency. Moreover, increasing the ammonia load contribution significantly reduced the emissions of CO2, CO, and HC but increased the emission of NO. It was found that ammonia delayed the start of combustion by 2.6CAD compared with pure biodiesel due to the low in-cylinder temperature and the high resistance of ammonia to autoignition. However, the combustion duration of biodiesel/ammonia decreased 19CAD compared with only biodiesel operation at full load, since most of the heat was released during the premixed combustion phase

Parameter sensitivity analysis for diesel spray penetration prediction based on GA-BP neural network

Machine learning has started to be used in engine research to optimize combustion and predict fuel spray characteristics. This paper presents the development of a machine learning model using a Genetic Algorithm-Backpropagation (GA-BP) neural network to predict spray penetration. The GA-BP neural network was selected for its ability to optimize neural network weights and thresholds, thereby improving model convergence and avoiding local minima, which are common challenges in complex, non-linear problems such as spray prediction. The model was trained using experimental data from diesel injector spray tests, and its accuracy was evaluated through parametric sensitivity analysis, examining the influence of various input factors. A comparison between the machine learning model and the traditional empirical formulas of spray penetration revealed that the machine learning model achieved greater accuracy. In terms of the sensitivity to inputs, it is interesting to find that the cognition of machines is different from that of humans. When an input parameter does not have any functional relationship with other input parameters, the absence of this input parameter will lead to a significant decrease in the accuracy of the output result. The results demonstrate that the machine learning approach offers higher accuracy and better generalizability compared to traditional empirical methods. This study recommends the ways to get better results of penetration prediction with BP neural networks, which is efficient in training and utilizing Artificial Neural Networks (ANNs).<br/