Proceedings of the Combustion Institute最新文献

{"title":"The effect on soot and its gas precursors of doping ethylene with 2,2,4,6,6-pentamethyl-heptane in the nitrogen-fuel stream of a laminar non-premixed Planar Mixing Layer Flame (PMLF)","authors":"Christian P. Bjork ,&nbsp;Mahmoud K. Ashour ,&nbsp;Evangelos K. Stefanidis ,&nbsp;Chiara Saggese ,&nbsp;Scott W. Wagnon ,&nbsp;Francesco Carbone","doi":"10.1016/j.proci.2025.105787","DOIUrl":"10.1016/j.proci.2025.105787","url":null,"abstract":"<div><div>Synthetic Aviation Turbine Fuels (SATFs) are promising for reducing soot emissions from the aviation sector and diversifying Jet Fuel (JF) sources. Accurately predicting the combustion and emissions behavior of SATFs (and other JFs) necessitates robust experimental databases to elucidate the chemistry of long-chain iso-paraffins, which can compose up to two-thirds of SATF blends and whose behavior is considered to be well-represented by that of iso-dodecane isomers. This study characterizes two laminar non-premixed Planar Mixing Layer Flames (PMLFs) with mild soot loads fueled by nitrogen-diluted ethylene, pure and doped with 2,2,4,6,6-pentamethyl-heptane, respectively. The two PMLFs have the same stoichiometric mixture fraction and total hydrocarbon mole fraction in the fuel stream (<em>X_F,F</em>=<em>X_C2H4,F</em>+<em>X_C12H26,F</em> = 0.260), resulting in nearly the same maximum temperature (<em>T_max</em>≈1800 K) and simple identification of the effects of doping. Importantly, any horizontal PMLF cross-section has a self-similar structure that can be modeled as an equivalent One-Dimensional Counterflow Flame (1D-CF) with vanishingly small strain rate (<em>a</em>). The cross-section at a Height Above the Burner (HAB) of 50 mm is characterized in terms of C₀-C₁₈ gas species using capillary sampling followed by GC-MS analyses. Laser-Induced Emission Spectroscopy (LIES) quantifies the soot volume fraction (<em>f_v</em>) profiles at HAB=25 and 50 mm where Elastic Laser Light Scattering (E-LLS) is performed to determine the <em>a</em> of the equivalent 1D-CFs and the profile of the E-LLS equivalent diameter (<em>d_6,3</em>) of soot. The substitution of 1500 ppm of ethylene with 2,2,4,6,6-pentamethyl-heptane causes an increase of ≈1.5 in the concentrations of several polycyclic aromatic hydrocarbons and <em>f_v</em>. Concurrently, the measured <em>d_6,</em>₃ doubles in the oxidizer stream, yet remains the same in the fuel stream, at HAB=50 mm. Instead, at HAB= 25 mm, the iso-dodecane doping does not affect the <em>d_6,</em>₃ profile in either stream. The experimental results partially validate the chemical reactions and soot formation kinetic model developed at Lawrence Livermore National Laboratory and provide directions to further improve its predictions.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105787"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144841803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Combustion and blow-out behavior in a cavity flame holder of Mach 2.5 n-dodecane-fueled scramjet model combustor","authors":"Shinji Nakaya ,&nbsp;Yuki Hirayama ,&nbsp;Yutaro Otsuka ,&nbsp;Kaito Hirose ,&nbsp;Kotaro Nakayama ,&nbsp;Kan Kobayashi ,&nbsp;Masahiro Takahashi ,&nbsp;Sadatake Tomioka ,&nbsp;Mitsuhiro Tsue","doi":"10.1016/j.proci.2025.105834","DOIUrl":"10.1016/j.proci.2025.105834","url":null,"abstract":"<div><div>The supersonic combustion mechanism was experimentally investigated using a Mach 2.5 n-dodecane fueled ramjet/scramjet dual-mode combustor with a cavity flame holder at stagnation pressure of 1021 kPa and a stagnation temperature of 1847 K. Heated n-dodecane was injected from the cavity closeout ramp. Optical diagnostics, including CH* and OH* chemiluminescence and Laser induced breakdown spectroscopy (LIBS), were employed. During steady combustion, the cavity shear-layer stabilized combustion was established autonomously without any assistance of the torch igniter. The local equivalence ratio was measured by moving the breakdown points using a 3-axis high precision motorized stage with measurements of CH* chemiluminescence in the cavity flame holders. Additionally, measurements were performed at fixed positions at 30 Hz as the fuel injection rate increased gradually. The results indicated the intensive OH* chemiluminescence emissions near the lower wall near the closeout ramp during the stable cavity shear-layer combustion. The equivalence ratio in the lower region of the flame was sufficiently rich, exceeding 2, while the flame region with high OH* and CH* signals was stoichiometric or lean. A steep gradient in the equivalence ratio was observed across the flame. During the transient combustion, as the fuel injection rate increased gradually, the equivalence ratio within the cavity increased. Additionally, the equivalence ratio within the cavity was high on the step side and decreases toward the ramp side. Near the flame regions exhibiting strong CH* chemiluminescence signals, the equivalence ratio approached unity. When the flame left the measurement point, the equivalence ratio exceeded 2, showing a substantial gradient across the flame. The flame tip was located near the fuel rich region exceeding 2. The findings of this study provide valuable insights for the design of kerosene-fueled scramjet combustors. Furthermore, the steady cavity flame demonstrated here has potential applications as a piloted flame for staged combustions.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105834"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145216305","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Local Rayleigh index reconstruction: Application to plasma-assisted sequential combustion under varying pulse repetition frequency","authors":"Matteo Impagnatiello,&nbsp;Nicolas Noiray","doi":"10.1016/j.proci.2025.105882","DOIUrl":"10.1016/j.proci.2025.105882","url":null,"abstract":"<div><div>This study investigates the influence of Nanosecond Repetitively Pulsed Discharges (NRPDs) on the acoustic response of the second stage of a Constant Pressure Sequential Combustor (CPSC) operating at atmospheric pressure. NRPDs are applied upstream of the second-stage combustion chamber to modify the autoignition process, thereby altering the combustor’s acoustic scattering properties. Large Eddy Simulations (LES) combined with System Identification (SI) methods are employed to better understand the NRPD-flame-acoustic interactions in the sequential flame across three different Plasma Repetition Frequencies (PRF), namely 20, 40, and 60 kHz. Results show that, while NRPDs always improve the overall acoustic scattering properties of the system compared to the combustion without NRPDs, the improvement is non-monotonic with respect to PRF. The most favorable acoustic characteristics are observed at <span><math><mrow><mtext>PRF</mtext><mo>=</mo><mtext>20</mtext></mrow></math></span> kHz. Analysis of local Rayleigh index fields, reconstructed from broadband-forced simulation data, reveals that variations in PRF alter the physical mechanism by which plasma discharges influence system acoustics. Plasma-generated kernels can either directly induce heat release rate fluctuations and act as acoustic energy sources or sinks, or indirectly affect the system’s acoustics by interacting with the main flame brush and modifying its response. The ability to influence the interaction between autoignition kernels and acoustics by simply adjusting the PRF underscores the potential of NRPDs as a versatile tool for controlling the acoustic behavior of sequential combustors, enabling adaptation to the varying operational needs of real gas turbines.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105882"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145216306","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Monitoring carbonaceous species in the transition from molecules to particles in shock-tube pyrolysis of toluene by laser induced emission spectroscopy","authors":"Can Shao ,&nbsp;Meysam Khademorezaeian ,&nbsp;Jürgen Herzler ,&nbsp;Greg J. Smallwood ,&nbsp;Thomas Dreier ,&nbsp;Torsten Endres ,&nbsp;Mustapha Fikri ,&nbsp;Christof Schulz","doi":"10.1016/j.proci.2025.105867","DOIUrl":"10.1016/j.proci.2025.105867","url":null,"abstract":"<div><div>Particle inception remains the most enigmatic stage of the formation process of carbonaceous particles. Detailed knowledge of the evolution of optical properties during the transition from molecular species to particles is essential for unraveling this phenomenon and enabling accurate particle volume fraction measurements of freshly formed particles in combustion environments. This study monitors the transition from molecular precursors to incipient soot particles during toluene pyrolysis behind reflected shock waves by laser-induced emission spectroscopy. Time-resolved and spectrally-resolved measurements of laser-induced emission were performed with excitation at 266, 355, 532, or 1064 nm. Microsecond time resolution was provided upon laser-pulse excitation via simultaneous measurements at various spatial locations behind the reflected shock wave, using the reaction-time-resolved detection concept. These measurements trace the evolution of different stages of the carbonaceous species evolving from red-shifted laser-induced fluorescence (LIF) progressing from toluene decomposition and polycyclic aromatic hydrocarbon (PAH) formation to the onset of incipient soot and subsequent laser-induced incandescence (LII) from refractory soot. LII signals recorded after 1064-nm excitation were utilized to identify initial particle formation, while time-resolved LII measurements provided insight into particle-size evolution. These findings contribute to a deeper understanding of soot inception and provide optical properties of the early stage of soot particles.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105867"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145216398","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multi-stage interactions on flame stability and NOx emissions in ammonia/methane co-combustion via fuel nitrogen-hydrocarbon separation","authors":"Yuanping Yang ,&nbsp;Tong Si ,&nbsp;Qian Huang ,&nbsp;Peng Ma ,&nbsp;Shuiqing Li","doi":"10.1016/j.proci.2025.105870","DOIUrl":"10.1016/j.proci.2025.105870","url":null,"abstract":"<div><div>Co-combustion of ammonia with fossil fuels is inherently constrained by the trade-off between flame stability and NO<em>_x</em> control. In our prior work, an innovative fuel nitrogen-hydrocarbon separation concept was proposed to broaden the low NO<em>_x</em> emission window by attenuating radical-driven reaction pathways. However, the influence of multi-stage flame interactions and mixing dynamics on the competing routes of nitrogen conversion remains insufficiently understood. In the present study, these effects are systematically investigated using a two-stage tangential swirl burner, with particular emphasis on their roles in governing flame stability and NO<em>_x</em> formation. Experimental investigations reveal three distinct flame stability regimes governed by ammonia blending ratio (<em>E</em>_NH3): (i) dual-flame stable, (ii) detached ammonia flame, and (iii) pulsating methane flame. Increasing <em>E</em>_NH3 enhances primary flame stability, but leads to a higher tendency for pulsation in the secondary methane flame due to attenuated secondary flow. NO<em>_x</em> emissions exhibit a non-monotonic dependence on the primary equivalence ratio (Φ_pri), with an optimal value around 1.05 achieving 134 to 298 ppm (@ 3.5 % O₂) NO<em>_x</em> emissions and NH₃ slip below 10 ppm. Notably, the influence of Φ_pri on NO<em>_x</em> emissions diminishes progressively as the overall equivalence ratio (Φ_ove) increases from 0.6 to 0.9, thereby remarkably broadening the low NO<em>_x</em> emission window. Spatially resolved NH₂* and OH*chemiluminescence analyses demonstrate that NO<em>_x</em> suppression correlates strongly with reduced overlap between primary and secondary reaction zones. Chemical reactor network analysis confirms that reduced multi-stage mixing suppresses HNO formation by impeding oxidative radical entrainment into ammonia-rich zones. This study fills a critical gap by ​quantifying how multi-stage mixing dynamics govern the trade-off between flame stability and NO<em>_x</em> emissions​ in ammonia/methane co-combustion.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105870"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145216959","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Constrained reduced-order modeling of reacting flows using bounded Gaussian process likelihoods: application to a furnace operating under MILD conditions","authors":"Muhammad Azam Hafeez ,&nbsp;Alberto Procacci ,&nbsp;Axel Coussement ,&nbsp;Alessandro Parente","doi":"10.1016/j.proci.2025.105846","DOIUrl":"10.1016/j.proci.2025.105846","url":null,"abstract":"<div><div>This study explores the application of a novel constrained reduced-order modeling framework to analyze a furnace operating under Moderate and Intense Low-oxygen Dilution (MILD) combustion conditions. The methodology employs low-cost Singular Value Decomposition (lcSVD) with optimal sensor placement for data compression and reconstruction, followed by Gaussian Process Regression (GPR) with bounded likelihood functions – truncated Gaussian and beta distributions – to ensure physically admissible outputs in high-dimensional combustion simulations. We test these models by predicting the unexplored thermo-chemical states of three-dimensional CH₄/H₂ simulation samples, with varying equivalence ratio, fuel composition (ranging from pure methane to pure hydrogen), and air injector diameter. Results indicate that the beta likelihood constrains species mass fraction predictions to the <span><math><mn>0</mn></math></span>–<span><math><mn>1</mn></math></span> interval by construction, yielding higher accuracy for species with localized distributions. Meanwhile, the truncated Gaussian enhances robustness by respecting realistic thermo-chemical ranges, reducing the influence of outliers, and improving model reliability in sparse or noisy data regions. These models demonstrate computational efficiency and scalability while delivering high-accuracy, physically consistent predictions.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105846"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145216962","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Determining the reaction enthalpy in pyrolysis and combustion at realistic process conditions","authors":"Raymond Chen,&nbsp;Ewa J. Marek","doi":"10.1016/j.proci.2025.105890","DOIUrl":"10.1016/j.proci.2025.105890","url":null,"abstract":"<div><div>Understanding and optimising processes during combustion or converting biomass to carbon materials requires information about reaction enthalpies, ideally determined experimentally at industrially relevant conditions. However, more complicated experimental set-ups exploring newer technologies often do not allow simultaneous measurement of reaction enthalpy, <em>e.g.</em> using differential scanning calorimetry (DSC). Therefore, we developed a method for <em>in-situ</em> measurement of the reaction enthalpy, requiring only minimal equipment of a sample holder, two thermocouples, and a furnace. To obtain the momentary reaction enthalpy, the heating rate of the sample upon insertion into the furnace was recorded and compared to the heating rate of an empty sample holder. Integrating the results led to the total reaction enthalpy in the temperature interval of interest. To correct for artefacts from radiative heat flux of the sample holder, a correction term was introduced, improving the accuracy of the method. To validate our method, the enthalpy of the phase changes from water and tin was measured and compared to values from literature, with the relative error being 9% and 19%, respectively. Additionally, the reaction enthalpy of birch and beech wood spheres and <em>Sargassum</em> powder were measured, revealing the properties and presentation of the sample to influence the precision of this method. From the momentary reaction enthalpy curve, the corresponding temperature range, in which the reaction occurred, was also determined. Overall, the developed method presents a simple and inexpensive approach for measuring the reaction enthalpy during thermal processing of biomass, providing an option that can work in setups incompatible with DSC.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105890"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145262387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structure and nitrogen oxide emissions of confined turbulent hydrogen jet flames","authors":"T.L. Howarth ,&nbsp;S. Nerzak ,&nbsp;P. Gruhlke ,&nbsp;J.T. Lipkowicz ,&nbsp;L. Panek ,&nbsp;S. Pfadler ,&nbsp;M. Gauding ,&nbsp;H. Pitsch","doi":"10.1016/j.proci.2025.105851","DOIUrl":"10.1016/j.proci.2025.105851","url":null,"abstract":"<div><div>In this work, a database analysis of three-dimensional direct numerical simulations using detailed chemistry is presented considering a turbulent lean premixed hydrogen/air round jet flame at elevated pressure and temperature (<span><math><mrow><mi>ϕ</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>5</mn><mo>,</mo><msub><mrow><mi>T</mi></mrow><mrow><mi>u</mi></mrow></msub><mo>=</mo><mn>530</mn><mtext>K</mtext><mo>,</mo><mi>p</mi><mo>=</mo><mn>8</mn><mi>atm</mi></mrow></math></span>), subject to different levels of domain confinement by solid walls. It is shown that for sufficiently small domain sizes, a coherent recirculation zone is present as expected; however, this does not affect the flame structure, consistent with experiments of attached hydrogen flames. Examination of velocity statistics indicates that, while both turbulent kinetic energy and Reynolds shear stresses increase with increasing domain size, these changes occur sufficiently far away from the flame. Each of the flames experiences the same level of mean shear, leading to the same flame structure. Despite identical turbulence-flame interactions between cases, nitrogen oxide (NO) emissions from the flames are observed to be different. For flames with recirculation zones comparable in size to the flame height, the superadiabatic temperatures caused by intrinsic flame instability are retained within the recirculation zone. Often, residence times in the post-flame are too short for locally elevated temperatures to have a significant impact on thermal NO formation. However, when these higher temperatures are coupled with the long fluid residence time in the recirculation zone, despite lower global residence times, this analysis shows that NO emissions from the flame can be enhanced.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105851"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145104442","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microgravity flame extinction induced by a moving air vortex ring","authors":"Sainan Quan ,&nbsp;Feng Zhu ,&nbsp;Jinglong Lyu ,&nbsp;Caiyi Xiong ,&nbsp;Xinyan Huang ,&nbsp;Shuangfeng Wang","doi":"10.1016/j.proci.2025.105825","DOIUrl":"10.1016/j.proci.2025.105825","url":null,"abstract":"<div><div>With the growth of outer space exploration missions, a safe, effective and clean fire extinguishing in microgravity spacecraft environment is critical. This paper explores the microgravity flame extinction dynamics induced by a moving air vortex ring. Tests were conducted both on the ground and in microgravity by a drop tower for comparison. An electromagnetic piston-tube system was designed to produce well-controlled air vortex ring to extinguish candle flames with different heat release rates (HRRs). We found a linear extinction boundary correlating the flame HRR with the Reynolds number and characteristic thickness of vortex ring. The flame extinguishing efficiency of air vortex ring in microgravity is 30 % higher than that on the ground. To explain the underlying mechanism, the flame stretch rate that accounts for the unsteady effect, i.e., the competition between external disturbance and flame self-stabilization, was examined. The absence of gravity and buoyancy has a minimum effect on the vortex ring but reduces the oxygen supply and flame diffusion, thereby the flame in microgravity is more vulnerable to vortex ring disturbance. The power of generating a vortex ring is 2–3 orders of magnitude lower than the HRR of flame that it can extinguish, and such a power requirement can be further reduced by 20–30 % in microgravity. This work reveals limiting conditions of vortex ring-induced flame extinction in microgravity and helps design future clean firefighting system for space travel.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105825"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145104445","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental and numerical analysis of the knock phenomenon inside ammonia–hydrogen internal combustion engine","authors":"Florian Hurault ,&nbsp;Pierre Brequigny ,&nbsp;Fabrice Foucher ,&nbsp;Christine Mounaïm-Rousselle","doi":"10.1016/j.proci.2025.105901","DOIUrl":"10.1016/j.proci.2025.105901","url":null,"abstract":"<div><div>Ammonia is one of the most promising carbon-free fuels for decarbonising sectors reliant on thermal energy conversion, such as power generation and transportation. However, its distinct combustion properties – low laminar burning velocity, narrow flammability limits, and high autoignition temperature – present challenges for stable and efficient ignition in internal combustion engines. To address these limitations, high-compression-ratio engines are often paired with ignition promoters such as hydrogen, which can be produced on-board through ammonia cracking. Nevertheless, the addition of hydrogen increases the risk of knock occurrence under such conditions. This study aims to improve the understanding of knock formation by investigating the chemical kinetics in the unburned gases during the engine cycle. Before engine testing, ignition delay times (IDTs) were measured in a Rapid Compression Machine for ammonia and partially cracked ammonia (PCA) mixtures (90% NH₃, 10% <span><math><mrow><mi>P</mi><mi>C</mi><mi>A</mi></mrow></math></span>: 7.5% H<span><math><mrow><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub><mo>+</mo><mn>2</mn><mo>.</mo><mn>5</mn></mrow></math></span>% N<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>) under engine-representative conditions (40–70 bar, 950–1000 K, <span><math><mrow><mi>Φ</mi><mo>=</mo></mrow></math></span> 0.5–1.5). Combined with previous IDT data for pure NH₃ and NH₃/10% H₂, the Stagni 2023 mechanism was selected for detailed chemical analysis. Experiments were conducted on a spark-assisted compression ignition engine (CR = 16.4) with fuel blends of pure NH₃, NH₃/10% H₂, and 10% <span><math><mrow><mi>P</mi><mi>C</mi><mi>A</mi></mrow></math></span>. Only the hydrogen-containing blends exhibited knock. The Chemkin Pro SI Engine Zonal Model was employed to simulate in-cylinder chemical evolution. Results indicated that the key reactions driving knock are the consumption of H₂ via H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> <span><math><mo>+</mo></math></span> NH<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> <span><math><mo>↔</mo></math></span> H <span><math><mo>+</mo></math></span> NH<span><math><msub><mrow></mrow><mrow><mn>3</mn></mrow></msub></math></span> and H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> <span><math><mo>+</mo></math></span> OH <span><math><mo>↔</mo></math></span> H <span><math><mo>+</mo></math></span> H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O in the end gases. These pathways contribute significantly to pre-ignition heat release, triggering knock, and explain the absence of knock in pure NH₃ cycles unless sufficient hydrogen is present through residuals or in-situ cracking.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105901"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145463003","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}