Combustion Characteristics of Ammonia in a Modern Spark-Ignition Engine

International audienc

Performance and Emissions of an Ammonia-Fueled SI Engine with Hydrogen Enrichment

International audienceWhile the optimization of the internal combustion engine (ICE) remains a very important topic, alternative fuels are also expected to play a significant role in the reduction of CO2 emissions. High energy densities and handling ease are their main advantages amongst other energy carriers. Ammonia (NH3) additionally contains no carbon and has a worldwide existing transport and storage infrastructure. It could be produced directly from renewable electricity, water and air, and is thus currently considered as a smart energy carrier and combustion fuel. However, ammonia presents a low combustion intensity and the risk of elevated nitrogen-based emissions, thus rendering in-depth investigation of its suitability as an ICE fuel necessary.In the present study, a recent single-cylinder spark-ignition engine is fueled with gaseous ammonia/hydrogen/air mixtures at various hydrogen fractions, equivalence ratios and intake pressures. A small hydrogen fraction is used as combustion promoter and might be generated in-situ through NH3 catalytic or heat-assisted dissociation. The in-cylinder pressure and exhaust concentrations of selected species are recorded and analyzed. Results show that ammonia is a very suitable fuel for SI engine operation, since high power outputs could be achieved with indicated efficiencies higher than 37% by taking advantage of the promoting effects of supercharging and hydrogen enrichment around 10% by volume. High NOx and unburned NH3 exhaust concentrations were also observed under fuel-lean and fuel-rich conditions, respectively. While hydrogen enrichment promotes the NH3 combustion efficiency and helps reducing its exhaust concentration, it has a promoting effect on NOx formation, assumedly due to higher flame temperatures. Therefore, it is recommended to take advantage of the simultaneous presence of exhaust heat, NOx and NH3 in a dedicated after-treatment device to ensure the economic and environmental viability of future ammonia-fueled engine systems

Experimental investigation on laminar burning velocities of ammonia/hydrogen/air mixtures at elevated temperatures

International audienc

Experimental study of RCCI engine – ammonia combustion with diesel pilot injection

Ammonia is seen as one potential carbon-free fuel, especially for maritime applications. Since SI engines require a significant ignition energy for large cylinders, engine manufacturers are targeting the use of ammonia in Compressed Ignition (CI) engines. Because of ammonia’s high auto-ignition temperature, to ensure that the combustion occurs in a CI engine, a pilot injection of a higher reactivity fuel must be used, as in Reactivity Controlled Compression Ignition engines. In the present study, the objective was to provide first unique data about the efficiency and pollutant emissions for a single cylinder compression ignition engine with a diesel energy fraction as minimum as possible (down to less than 2%) at a constant 1000 rpm. Experiments cover the impact of a wide variation of equivalence ratios of NH3-air mixtures from ultra-lean to slightly rich conditions. CO2, CO, NH3, NOX, N2O, UHC values were measured with a Fourier Transform Infrared (FTIR) spectrometer. Results of CO2 and N2O are presented as CO2-Equivalent (CO2eq) impact. Combustion stability was achieved for most conditions but not for the leanest ones. Furthermore, under lean conditions for a similar ammonia content, the minimum CO2eq is reached with a slightly higher Diesel Energy Fraction than the minimum possible. Finally, both leanest and richest conditions present a higher level of CO2eq compared to the range of ammonia/air mixtures at stoichiometry or just below

Health and Safety Workshop Report version 2, 2023

This report summarises the discussions that took place at the workshop on “Ammonia as an Energy Vector – Health and Safety” during the 1st Symposium on Ammonia Energy hosted at Cardiff University from the 1st to the 3rd of September 2022. Furthermore, the document has been updated with discussions from the workshop on health and safety at the 2nd Symposium on Ammonia Energy hosted at the University of Orléans from the 11th to the 13th of July 2023. Several presenters from various companies and organizations participated in discussions at these two workshops, and all provided some insight into the most concerning issues when using ammonia as an energy vector. The workshop, co-led by the Health and Safety Executive (HSE) and Cardiff University, promised to examine some important questions that need to be answered via Research and Development (R&D) to tackle the unknowns of using ammonia in both the energy and transport sectors. The outcome of the workshop is this document, which will be put forward in the following health and safety workshops scheduled to take place in future sessions of the Symposia, with the aim of coordinating research efforts undertaken by industries, governmental bodies and academic institutions

X-ray diagnostics of dodecane jet in spray A conditions using the new one shot engine (NOSE)

[EN] Quantifying liquid mass distribution data in the dense near nozzle area to develop and optimize diesel spray by optical diagnostic is challenging. Optical methods, while providing valuable information, have intrinsic limitations due to the strong scattering of visible light at gas-liquid boundaries. Because of the high density of the droplets near the nozzle, most optical methods are ineffective in this area and prevent the acquisition of reliable quantitative data. X-ray diagnostics offer a solution to this issue, since the main interaction between the fuel and the X-rays is absorption, rather than scattering, thus X-ray technique offers an appealing alternative to optical techniques for studying fuel sprays. Over the last decade, x-ray radiography experiments have demonstrated the ability to perform quantitative measurements in complex sprays. In the present work, an X-ray technique based on X-ray absorption has been conducted to perform measurements in dodecane fuel spray injected from a single-hole nozzle at high injection pressure and high temperature. The working fluid has been doped with DPX 9 containing a Cerium additive, which acts as a contrast agent. The first step of this work was to address the effect of this dopant, which increases the sensitivity of X-ray diagnostics due its strong photon absorption, on the behavior and the physical characteristics of n-dodecane spray. Comparisons of the diffused back illumination images acquired from ndodecane spray with and without DPX 9 under similar operating conditions show several significant differences. The current data show clearly that the liquid penetration length is different when DPX 9 is mixed with dodecane. To address this problem, the dodecane was doped with a several quantities of DPX containing 25% ± 0.5 of Cerium. Experiments show that 1.25% of Ce doesn’t affect the behaviour of spray. Radiography and density measurements at ambient pressure and 60 bars are presented. Spray cone angle around 5° is obtained. The obtained data shows that the result is a compromise between the concentration of dopant for which the physical characteristics of the spray do not change and the visualization of the jet by X-ray for this concentration.This work is supported by ANR Research National Agency (ECN-France project). I.C. is supported by ANR PLANEX ANR-11-EQPX-0036-01.The authors would like to thank Thierry Seguelong for DPX9 supply and Gilles Bruneaux for scientific discussions.Chiboud, I.; Arjouche, H.; Nilaphai, O.; Dozias, S.; Moreau, B.; Hespel, C.; Foucher, F.... (2017). X-ray diagnostics of dodecane jet in spray A conditions using the new one shot engine (NOSE). En Ilass Europe. 28th european conference on Liquid Atomization and Spray Systems. Editorial Universitat Politècnica de València. 755-762. https://doi.org/10.4995/ILASS2017.2017.4705OCS75576

Environmental life cycle analysis of an ammonia-ethanol fueled internal combustion engine (ICE) for power generation

Climate change and other environmental impacts have been an enormous worldwide concern in recent decades. Decarbonizing strategic and economic industries is mandatory. Using carbon-free fuels such as ammonia (NH3) has been promoted as a promising solution for decarbonizing both energy and industrial sectors. The use of biofuels has also been encouraged as an attractive alternative to replace conventional petroleum-based fuels in transportation. Therefore, the present study evaluates the environmental profile of using ammonia-ethanol blends in internal combustion engines (ICE) for power generation systems through a life cycle assessment (LCA) framework using the OpenLCA v1.10.3 software. The experiments were conducted in a single-cylinder spark-ignition engine that employs direct injection using three different fuel compositions (in mole fraction) of ethanol/ammonia (75/25, 50/50, and 25/75), with two different intake pressures (0.5 and 1 bar) at 1000 rpm. The functional unit (FU) was set at 1 kWh. The GWP results for 0.5 bar of intake pressure are between 0.07 and 0.95 kg CO2/kWh. The scenario running on Brazilian ethanol and green ammonia is the most environmentally friendly case. The carbon footprint for ethanol/ammonia-based ICE at 1 bar fluctuates between 0.052 and 0.68 kg CO2/kWh. Similarly, regarding GWP, there is a slight difference in Fossil Depletion Potential (FDP) when using ethanol from Brazil and ethanol from Ecuador due to the lack of circular economy strategies in Ecuador's agriculture, compared to Brazil. Regarding the contribution analysis, for a 50% green ammonia – 50% ethanol scenario for power generation, ethanol production has the highest contribution for global warming, fossil depletion, and freshwater eutrophication potential impacts. Compared to the analysed environmental impacts, some of our proposed scenarios depict better performance than the average electricity production in the United Kingdom, France and Europe. Therefore, ethanol-ammonia fuel-based for power generating systems could be an important option to contribute to the decarbonization of the electric sector

Combustion performances of premixed ammonia/hydrogen/air laminar and swirling flames for a wide range of equivalence ratios

Ammonia, a carbon-free source of hydrogen has recently gained considerable attention as energy solution towards a green future. Previous works have shown that adding 30VOL.% hydrogen with ammonia can eradicate the drawbacks of pure ammonia combustion but no study in the literature has investigated this blend across a wide range of equivalence ratios. The present work investigates 70/30VOL.% NH3/H2 blend from 0.55 ≤ Φ ≤ 1.4 for both premixed laminar spherically expanding flames and turbulent swirling flames at atmospheric conditions. A detailed chemistry analysis has been conducted in Ansys CHEMKIN-PRO platform using a chemical reactor network (CRN) model to simulate the swirling turbulent flames. NO and NO2 emissions have followed similar bell-shaped trends, peaking at around Φ = 0.8, while N2O emission rises at lean conditions (Φ ≤ 0.7). The results indicate that Φ = 1.2 is the optimum equivalence ratio with reduced NOX emissions and some ammonia slip