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

Combustion Characteristics of Ammonia in a Modern Spark-Ignition Engine

International audienc

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

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

2023 Roadmap on ammonia as a carbon-free fuel

The 15 short chapters that form this 2023 ammonia-for-energy roadmap provide a comprehensive assessment of the current worldwide ammonia landscape and the future opportunities and associated challenges facing the use of ammonia, not only in the part that it can play in terms of the future displacement of fossil-fuel reserves towards massive, long-term, carbon-free energy storage and heat and power provision, but also in its broader holistic impacts that touch all three components of the future global food-water-energy nexus

Développement de la technique "Incandescence Induite par Laser" pour caractériser les particules de suies dans un moteur Diesel

ORLEANS-BU Sciences (452342104) / SudocSudocFranceF

Développement de la technique de spectroscopie d'absorption UV, pour l'étude de l'émission de NO dans la chambre de combustion d'un moteur à allumage commandé

ORLEANS-BU Sciences (452342104) / SudocSudocFranceF

Etude expérimentale des modes de combustion essence sous forte pression et forte dilution

Face aux normes actuelles et futures de plus en plus draconiennes en termes d émissions polluantes, les constructeurs automobiles cherchent en permanence à améliorer le rendement des moteurs à allumage commandé. L une des voies efficaces et applicables à court terme pour réduire les émissions de dioxyde de carbone (CO2) consiste à réduire la cylindrée des moteurs tout en conservant leur performance grâce à la sur-alimentation : c est l approche de l éco-suralimentation ou downsizing . L une des particularités de ce mode de fonctionnement est le fort niveau de pression et de taux de dilution dans lequel se propage la flamme de prémélange. La simulation de la combustion turbulente de prémélange est devenue un outil incontournable pour la R&D. Toutefois, les hypothèses sur lesquelles reposent les modèles de combustion, tout particulièrement le modèle de flammelettes, peuvent être sujettes à discussion dans le cas d un fonctionnement de type downsizing . Le but de ce travail de thèse est donc d étudier expérimentalement les régimes de combustion de manière à valider ou non l utilisation de ces modèles. Les grandeurs caractéristiques de la turbulence ont alors été caractérisées lors de la phase de compres-sion pour différentes pressions d admission à l aide de la vélocimétrie par imagerie de particules. La vitesse de combustion de laminaire a, quant à elle, été estimée à partir d un mécanisme cinétique réduit. L utilisation de la tomographie laser par diffusion de Mie avec et sans suivi temporel, nous a permis de caractériser la vitesse de combustion turbulente et la structure du front de flamme pour différentes pressions d admission et différents taux de dilution. Lors de cette étude, nous avons ainsi pu mettre en évidence une cassure dans l évolution de la PMI et de la vitesse de combustion turbulente à partir d un taux de dilution de 25% : cette cassure a été reliée à la transition entre le régime de flammelette et le régime des flammes plissées épaissies.Faced with the current and future more and more drastic standards for pollutant emissions, car manufacturers try to improve the efficiency of Spark Ignition engine. One effective and applicable ways to reduce the greenhouse emissions (CO2) in the short run is based on the reduction of the engine size while preserving their performance thank to turbocharging: eco-supercharging or downsizing approaches. One of the characteristics of this operating mode is the high level of the pressure and of the dilution rate of the medium in which the premixed flame propagates. The simulation of turbulent premixed flame is nowadays an indispensable tool for R&D. However, the assumptions on which the combustion models are based, particularly the flamelet model, can be prone to discussion in the downsizing conditions. The objective of this work is thus to study experimentally the combustion regimes in order to validate or not the use of these models. Turbulence parameters and flow fields were then characterized out during the compression stroke for several intake pressures by using Particle Imaging Velocimetry technique. The laminar burning velocity was estimated by using reduced chemical kinetic schemes. The Mie scattering laser tomography technique with and without temporal follow-up, enabled us to characterize the turbulent burning velocity and the flame front structure for different intake pressures and dilution rates. In this study, a break in the evolution of the IMEP and the turbulent burning velocity for a dilution rate of 25% has been obtained: this break was linked to the transition between the flamelet zone and the distributed reaction zones.ORLEANS-SCD-Bib. electronique (452349901) / SudocSudocFranceF