Combustion and Flame最新文献

{"title":"Advancing 3D understanding of aluminum agglomerates in propellant environment using reconstruction techniques","authors":"Lu Liu ,&nbsp;Geng Xu ,&nbsp;Yao Shu ,&nbsp;Guoqiang He ,&nbsp;Peijin Liu ,&nbsp;Wen Ao","doi":"10.1016/j.combustflame.2025.114448","DOIUrl":"10.1016/j.combustflame.2025.114448","url":null,"abstract":"<div><div>Aluminum is commonly used in solid propellants to enhance energy density, but it tends to form large agglomerations during combustion, leading to incomplete combustion and reduced propulsion efficiency. To better understand the agglomeration and combustion behavior of aluminum particles, we developed a dual-perspective high-speed microscopic imaging system that captures the evolution of agglomerations from two aligned viewpoints. A two-step unsupervised segmentation algorithm based on K-means clustering and a Neural Radiance Field (NeRF)-based reconstruction framework were employed to resolve the 3D distribution of molten aluminum droplets and oxide caps. The results revealed a linear increase in the oxide-to-metal ratio over time. A combustion model was further developed to describe the burning process of aluminum particles in multi-component oxidizing atmospheres, incorporating O₂, CO₂, and H₂O as oxidants. The model assumes diffusion-limited combustion with oxide deposition, and was validated against literature and experimental data, showing good agreement in predicting particle size evolution and burning time. Sensitivity studies showed that oxidizer concentration has a significantly greater impact on combustion rate than temperature. The proposed imaging and modeling approach improves the understanding of aluminum agglomerate evolution in realistic propellant environments, and provides valuable guidance for optimizing propellant formulations to reduce incomplete combustion and improve solid rocket motor performance.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"281 ","pages":"Article 114448"},"PeriodicalIF":6.2,"publicationDate":"2025-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144932736","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":"Effect of aluminum, iron, and zirconia additives on the combustion of boron","authors":"Mysha Momtaz,&nbsp;Jonathan L. McNanna,&nbsp;Purvam Gandhi,&nbsp;Mirko Schoenitz,&nbsp;Edward L. Dreizin","doi":"10.1016/j.combustflame.2025.114446","DOIUrl":"10.1016/j.combustflame.2025.114446","url":null,"abstract":"<div><div>Spherical composite powders with particle sizes around 10 µm, combining boron and aluminum, were prepared by emulsion-assisted milling. Powders milled using the steel and zirconia milling media were contaminated by iron and zirconia, respectively. Some powders used small amounts of Fluorel® as a binder. The oxidation of the prepared powders heated in an Ar/O₂ gas flow was studied using thermal analysis. The ignition temperature in air was determined using an electrically heated filament. Prepared powders were blended with KNO₃ as an oxidizer and ignited using a CO₂ laser beam. The powders were also injected into a closed vessel and burned as an aerosol. The results show no effect of Fluorel® or zirconia contamination on the powder reactivity. The added iron causes a reduction in the oxidation onset temperature, whereas added aluminum increases that temperature. Both added iron and aluminum cause a reduction in the flame temperature and suppress the formation of the vapor-phase intermediate BO₂. A reduced flame temperature delays the aerosol flame propagation rate. The powder morphology achieved by emulsion-assisted milling enhances the powder reactivity, as is evidenced by reduced ignition temperatures and accelerated rate of flame propagation for the milled powders containing no iron or aluminum.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"281 ","pages":"Article 114446"},"PeriodicalIF":6.2,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144926321","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":"Propagation of ultra-lean hydrogen/air flames in a Hele-Shaw cell","authors":"Linlin Yang ,&nbsp;Yan Wang ,&nbsp;Tianhan Zhang ,&nbsp;Xiaolong Gou ,&nbsp;Wenjun Kong ,&nbsp;Zheng Chen","doi":"10.1016/j.combustflame.2025.114444","DOIUrl":"10.1016/j.combustflame.2025.114444","url":null,"abstract":"<div><div>Ultra-lean hydrogen flame is closely related to hydrogen safety. Recently, different types of hydrogen flame have been observed in experiments under ultra-lean conditions. However, the evolution and propagation of ultra-lean hydrogen flames are still not well understood. In this study, 3D simulations considering detailed chemistry and transport models are conducted for ultra-lean premixed hydrogen/air flames propagating in an open Hele-Shaw cell with isothermal walls. It is found that ultra-lean hydrogen flames are very sensitive to equivalence ratio, <em>ϕ</em>. As <em>ϕ</em> decreases from 0.225 to 0.21, different cellular flame regimes, including two-headed branching, two-headed finger and one-headed finger (ball-like flame) are sequentially observed. The cell size shows a decreasing tendency. Isolated ball-like flames and two-headed finger are stable in the ultra-lean mixture. During the flame cell propagation, both heat loss and heat release exhibit oscillatory characteristics since they are correlated with each other. The oscillation frequency is found to increase with <em>ϕ</em>. In order to balance the conductive heat loss to walls, two-headed flames split while isolated ball-like flames shrink, resulting in periodic changes in flame surface area and heat release rate. Moreover, ultra-lean flames are found to be characterized by high local equivalence ratio caused by strong differential diffusion of hydrogen over other species, highlighting the effect of diffusional-thermal instability (DTI) on sustaining the ultra-lean flame. Furthermore, stable ball-like flames and two-headed finger can exist simultaneously. Interestingly, flame instabilities play a stabilizing role in the ultra-lean flames. Darrieus-Landau instability (DLI) contributes to the stabilization of two-headed finger flames with strong mutual interaction between adjacent cells, whereas ball-like flames dominated by DTI tend to move away from each other to gain deficient fuel and drift in a zigzag manner. The present 3D simulations help to understand flame cell propagation and stabilization in ultra-lean hydrogen/air mixture within an open Hele-Shaw cell.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"281 ","pages":"Article 114444"},"PeriodicalIF":6.2,"publicationDate":"2025-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144922926","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":"Hydrodynamically unstable premixed flames in gravitational fields: Effect of gas expansion","authors":"Kaname Matsue ,&nbsp;Moshe Matalon","doi":"10.1016/j.combustflame.2025.114403","DOIUrl":"10.1016/j.combustflame.2025.114403","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The hydrodynamic instability is a long wave instability that results in premixed flames from gas expansion caused by the heat released during combustion. It was discovered independently by Darrieus and Landau treating the flame as a structureless surface of discontinuity, and bears their names suitably. Investigations that followed their pioneer work revealed that diffusion effects within the flame zone may, for mixtures deficient in their less mobile reactants, stabilize short wavelength disturbances. Thus, unless confined to a narrow domain, a planar flame remains unconditionally unstable. Landau has also examined the role of gravity and concluded that the long wavelength disturbances are stabilized by gravitational forces when the flame is propagating downwards. In the present paper, we study the composite effects of thermal expansion, differential diffusion, and gravity on the flame dynamics. We use a hydrodynamic theory that properly resolves the flame structure and extracts an explicit expression for the flame speed with a coefficient that lumps all the physicochemical properties of the combustible mixture. This nonlinear model enables studying both, the initial flame development by means of a linear stability analysis and the nonlinear development using a hybrid Navier–Stokes/flame-tracking methodology. The linear analysis yields explicit conditions for the growth rate of disturbances of arbitrary wavelength, and provides the critical conditions for the instability onset. The consequence of the instability has been determined numerically by examining the long time flame evolution, focusing on the flame morphology and the overall propagation speed. We examine both, downward and upward propagation and exploit the following three parameters: the unburned-to-burned density ratio or thermal expansion parameter, the Markstein number that depends on the composition of the mixture and the diffusive properties of the reactants, and the ratio of the gravitational to the inertial forces, or the gravitational parameter. Our results are summarized by means of bifurcation diagrams that elucidate the role of these parameters on the flame propagation.&lt;/div&gt;&lt;div&gt;&lt;strong&gt;Novelty and significance&lt;/strong&gt;&lt;/div&gt;&lt;div&gt;This paper consists of a comprehensive stability analysis, linear and nonlinear of planar flames propagating upwards and downwards. The linear analysis covers a wide range of the three relevant parameters: the unburned-to- burned density ratio or thermal expansion parameter, the Markstein number that depends on the pressure level, the composition of the mixture, and the diffusive properties of the reactants, and the ratio of the gravitational to the inertial forces, or reciprocal of the Froude number. The nonlinear analysis is the first that considers realistic values of the gas expansion and describes the evolving flame morphology and the flame propagation speed for a wide range of Markstein numbers under different Froude numbers.&lt;/div&gt;","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"281 ","pages":"Article 114403"},"PeriodicalIF":6.2,"publicationDate":"2025-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144911593","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":"Investigation on enhancement of the combustion flame speed and stability of ammonia-air mixture using nanosecond surface dielectric barrier discharge (nSDBD)","authors":"Yong Hu,&nbsp;Weixin Rong,&nbsp;Zhencao Zheng,&nbsp;Ruijiao Cao,&nbsp;Feiyang Zhao,&nbsp;Wenbin Yu","doi":"10.1016/j.combustflame.2025.114432","DOIUrl":"10.1016/j.combustflame.2025.114432","url":null,"abstract":"<div><div>Ammonia is a carbon-free and hydrogen carrier renewable fuel, but its ignition difficulties and low flame propagation speed limit its application in engines. The aim of this study is to utilize plasma derived by nanosecond pulse surface dielectric barrier discharge (nSDBD) to achieve ammonia ignition under high ambient pressure with enhanced combustion performance. The ignition and combustion characteristics of ammonia-air mixtures within the pressure range of 1 to 20 bar and equivalence ratio range of 0.8 to 1.3 are investigated in a constant-volume combustor. The experimental results demonstrate that the buoyancy effect significantly affects the combustion stability of ammonia. When the flame radius reaches 12 mm, the Froude number (<em>Fr</em>_<em>12</em>) is used to evaluate the buoyancy effect, and combustion stability gets deteriorated as <em>Fr</em>_<em>12</em> decreases. Employing nSDBD to generate multiple ignition nuclei is proven to increase the flame propagation speed of ammonia combustion, corresponding with enhanced <em>Fr</em>_<em>12</em> value to smooth the combustion instability. Thereby, plasma modulated by nSDBD will be served as a promising combustion improver to overcome engine high pressure combustion bottleneck.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"281 ","pages":"Article 114432"},"PeriodicalIF":6.2,"publicationDate":"2025-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144911601","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":"Flame propagation through a non-ideal gas","authors":"John K. Bechtold ,&nbsp;Moshe Matalon","doi":"10.1016/j.combustflame.2025.114436","DOIUrl":"10.1016/j.combustflame.2025.114436","url":null,"abstract":"<div><div>Advances in understanding the dynamics of premixed flames have been predominantly made by assuming that the combustible mixture behaves as an ideal gas. While this assumption is suitable in many circumstances, it does not properly describe combustion at high pressures that is of interest in some practical systems. In this paper, we derive an asymptotic model of premixed flame propagation through a non-ideal gas in closed vessels, but the results readily accommodate flame propagation under isobaric conditions. Specifically, we employ the Noble-Abel equation of state, accounting for finite molecular volume, which is known to be significant at high pressures. Our analysis resides within the framework of the hydrodynamic theory for which the flame is thin relative to all the other length scales in the problem. Multi-scale methods are used to resolve the internal flame structure, resulting in explicit equations that determine the pressure rise throughout the vessel, as well as the instantaneous flame location, the local mass burning rate and flame speed. The flame speed is modulated by a Markstein number which has an explicit dependence on the co-volume parameter, a measure of the volume occupied by the molecules involved in the combustion process. For the enclosed flame, the Markstein number is also found to depend on the mean pressure rise. Our model is used to examine non-ideal gas effects on the propagation of free and confined flames in simple geometries.</div><div><strong>Novelty and significance statement</strong></div><div>This work provides the first formal asymptotic model of premixed flame propagation through a non-ideal gas in free and confined environments, thereby extending the hydrodynamic theory to new parameter regimes. The work is significant in that many practical combustion systems, such as rocket engines, gas turbines and incinerators, operate under these conditions.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"281 ","pages":"Article 114436"},"PeriodicalIF":6.2,"publicationDate":"2025-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144911602","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":"Quantifying uncertainties in the input–output identification of Flame Transfer Functions","authors":"Justus Florian Radack,&nbsp;Bayu Dharmaputra,&nbsp;Bruno Schuermans,&nbsp;Nicolas Noiray","doi":"10.1016/j.combustflame.2025.114398","DOIUrl":"10.1016/j.combustflame.2025.114398","url":null,"abstract":"<div><div>The Finite Impulse Response model of a flame subject to acoustic forcing can be identified from numerical simulations. It is often subsequently used to obtain the frequency domain Flame Transfer Function (FTF). Its estimation from a finite time series introduces uncertainty in the model coefficients, affecting the prediction of the system response when implemented in a thermoacoustic network model. Quantifying how this uncertainty affects the identified FTF is commonly achieved by repeatedly sampling from the distribution of the model coefficients to obtain numerous model realizations and computing their Fourier transform. In the present work, we instead provide the exact mathematical connection between the uncertainty in the time and frequency domain, and give the sampling distributions for the gain and phase of the transfer function. Confidence intervals can then be associated with each predicted FTF value from a single time series. Moreover, by setting a permissible range in the gain and phase of the FTF, the appropriate time series length of the simulation can be determined on the fly.</div><div><strong>Novelty and Significance Statement</strong></div><div>In this paper, a novel approach to quantify uncertainties in Flame Transfer Functions (FTFs), which are crucial for predicting thermoacoustic instabilities in combustion systems, is introduced. This research provides an exact mathematical connection between uncertainties in the time domain impulse response and their impact on FTF gain and phase in the frequency domain. We derive sampling distributions for the gain and phase of the FTF, which enables the assignment of confidence intervals to the Bode representation of the FTF. This advancement helps determine the necessary simulation duration to achieve a desired uncertainty level, improving the reliability and efficiency of thermoacoustic predictions.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"281 ","pages":"Article 114398"},"PeriodicalIF":6.2,"publicationDate":"2025-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144911603","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":"Publication / Copyright Information","authors":"","doi":"10.1016/S0010-2180(25)00460-2","DOIUrl":"10.1016/S0010-2180(25)00460-2","url":null,"abstract":"","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"280 ","pages":"Article 114423"},"PeriodicalIF":6.2,"publicationDate":"2025-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144917127","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":"Impact of gasoline composition on the effects of nitric oxide on autoignition and knock in a DISI engine","authors":"Namho Kim ,&nbsp;Magnus Sjöberg ,&nbsp;Dario Lopez-Pintor ,&nbsp;Naoyoshi Matsubara ,&nbsp;Koji Kitano ,&nbsp;Ryota Yamada ,&nbsp;Chiara Saggese","doi":"10.1016/j.combustflame.2025.114367","DOIUrl":"10.1016/j.combustflame.2025.114367","url":null,"abstract":"<div><div>Modern spark-ignition engines use exhaust gas recirculation (EGR) to dilute the charge and suppress knock, enabling the use of higher compression ratios and/or more optimum combustion phasing for higher efficiency. The effectiveness of EGR is affected by the composition of the fuel and its chemical-kinetic interactions with combustion products. Among those, nitric oxide (NO) has been shown to strongly affect autoignition reactivity. However, the impact of fuel composition of the effect of NO on reactivity is not well-understood.</div><div>In this study, engine experiments were conducted to assess the impact of NO seeded to the intake on knock-limited operation of two gasoline fuels (high cycloalkane content, or HCA, and high olefin content, or HO). Results showed that compositionally-different fuels responded differently to NO. HCA, which was less knock-limited than HO for NO &lt; 200 ppm, became more knock-limited for NO &gt; 200 ppm. Moreover, it was found that differences in knock between fuels were caused by differences in autoignition chemistry and not in the sequential autoignition process of the end gas that occurs due to thermal stratification. Chemical kinetic simulations were performed to better understand the experimental results. For HCA, intermediate-temperature heat release had a greater impact on autoignition reactivity than low-temperature heat release, while the opposite was observed for HO. For both fuels, NO enhances the magnitude of low-temperature heat release via NO + HO₂ → NO₂ + OH. The effect of NO on reactivity was stronger for HCA because OH produced from NO helped to overcome the OH quenching effect of cyclopentane, a main species in HCA. In contrast, HO had relatively strong inherent low-temperature chemistry arising from iso-octane, which reduced the impact of NO on reactivity. For the range of NO mole fractions tested in this study, in-cylinder NO increased fuel’s knock propensity, especially for fuels with mild low-temperature chemistry.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"281 ","pages":"Article 114367"},"PeriodicalIF":6.2,"publicationDate":"2025-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144911594","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":"On electrode placement in plasma-assisted ignition of a scramjet flame-holder","authors":"Rajath Shetty ,&nbsp;Cesar Cardenas ,&nbsp;Luca Massa","doi":"10.1016/j.combustflame.2025.114408","DOIUrl":"10.1016/j.combustflame.2025.114408","url":null,"abstract":"<div><div>A multi-scale model for plasma-assisted combustion is developed to investigate how the location of the electrodes in the cavity affects the ignition of supersonic flows in nanosecond repetitive pulse discharges. A new approach to plasma-fluid coupling is investigated that relies on solving the detailed plasma and photon transport equations on a near-electrode block partition of the overall mesh during the pulse and synchronizing the thermochemical balances with the reactive-fluid mesh by interpolation. The approach reproduces experimental observations of assisted ignition: the formation of trailing-edge flames in high-enthalpy conditions, the formation of localized ignition kernels near the cathode for medium-enthalpy conditions, and the presence of a distributed region of elevated OH mass fraction for conditions leading to no ignition. The approach matches the experimental measurement of plasma-energy coupling. The analysis emphasizes the significance of fluid strain rate in plasma-fluid coupling. The location of the electrode is found to affect ignition by supporting a larger radical turnover by plasma when the electrodes are placed in regions of lower strain, leading to a thicker reaction region.</div><div><strong>Novelty, Significance, and Contributions</strong>: A novel computational approach to plasma-gas coupling is developed and validated. This approach was applied to investigate the influence of strain rate on the focusing of pre-ionization electrons in the low-shear region of cavity stabilizers. The authors identify a correlation between strain rate and radical turnover number. This study led to the determination of the contribution of electrode placement to the efficacy of plasma actuation in supersonic flame-holders. The importance of the cathode location to supersonic ignition is investigated for the first time in detail. This research presents a significant advancement of previously published works: it models photoionization from first principles and includes the gas-plasma interactions in a three-dimensional turbulent flow.</div></div>","PeriodicalId":280,"journal":{"name":"Combustion and Flame","volume":"281 ","pages":"Article 114408"},"PeriodicalIF":6.2,"publicationDate":"2025-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144908133","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}