Investigation of heat sink of endothermic hydrocarbon fuels

Endothermic hydrocarbon fuels are advanced coolants for high-temperature structures of spacecraft. No data of tested-cooling-ability of endothermic fuels have been broadly discussed in literature. In this work a high-temperature flow calorimeter was designed, and the cooling capacity of six different hydrocarbon fuels were measured. Experimental results showed that these hydrocarbon fuels have capacity for cooling high-temperature structures, and that the cooling capacity of fuel N-1 can reach 3.15 M J/kg, which can nearly satisfy the requirement of thermal management for a Mach 3 cruise aircraft, whose heat sink requirement is about 3.5 M J/kg. The endothermic velocity of hydrocarbon fuels was also measured by the calorimeter.

Effect of Liquid-phase Oxidation Impurities on Solubility of Water in Hydrocarbon Fuels

The effect of liquid-phase oxidation impurities on the solubility of water in hydrocarbon fuels was studied.The results show that the concentration of polar surfactant molecules in the first region increases(true solution)during fuel oxidation,and since the oxidation groups(-COOH,-O=O,-OH,etc.)have similar dipole momentμ,the dielectric loss tangent tanδincreases linearly in this region with surfactant concentration.Upon further oxidation,micelle structures begin to form at a certain point.Micelle formation leads to a sharp decrease in the dipole moment attributable to the monomer unitμ/n,where nis the number of molecules in a micelle.A several-fold decrease in the dipole moment leads to a sharp drop in tanδ.Upon further increase in the number and size of micelles,the dipole moment remains practically unchanged,and the dielectric loss tangent begins to increase linearly again with surfactant concentration.If the critical concentration for micelle formation is achieved upon further oxidation of hydrocarbon liquids,micelle formation processes occur spontaneously in the solution,and the true solution becomes a colloidal system(sol).The resulting micelles are structured with hydrocarbon radicals of molecules toward the outside and hydrophilic(polar)groups toward the inside.Water molecules are located inside micelles and held so securely that water molecules do not aggregate as temperature decreases.The reason for significant differences in the equilibrium solubility of water in hydrocarbon fuels is the different oxidation factors of product samples,resulting from the accumulation of various concentrations of oxidation products,which are natural surfactants,in hydrocarbon fuels.

Research Progress of Catalysts and Initiators for Promoting the Cracking of Endothermic Hydrocarbon Fuels

Catalytic/initiated cracking of endothermic hydrocarbon fuels is an eff ective technology for cooling a hypersonic aircraft with a high Mach number(over 5).Catalysts and initiators can promote fuel cracking at low temperatures,increase fuel conversion and the heat sink capacity,and suppress coke deposition,thereby reducing waste heat.Catalysts mainly include metal oxide catalysts,noble metal catalysts and metal nanoparticles,zeolite catalysts,nanozeolite catalysts,and coating catalysts.Moreover,initiators roughly include nitrogenous compounds,oxygenated compounds,and hyperbranched polymer initiators.In this review,we aim to summarize the catalysts and initiators for cracking endothermic hydrocarbon fuels and their mechanisms for promoting cracking.This review will facilitate the development of the synthesis and exploration of catalysts and initiators.

Evaluation of Cellulose as a Substrate for Hydrocarbon Fuel Production by <i>Ascocoryne sarcoides</i>(NRRL 50072)

The fungal endophyte, Ascocoryne sarcoides, produced aviation, gasoline and diesel-relevant hydrocarbons when grown on multiple substrates including cellulose as the sole carbon source. Substrate, growth stage, culturing pH, temperature and medium composition were statistically significant factors for the type and quantity of hydrocarbons produced. Gasoline range (C5-C12), aviation range (C8-C16) and diesel range (C9-C36) organics were detected in all cultured media. Numerous non-oxygenated hydrocarbons were produced such as isopentane, 3,3-dimethyl hexane and d-limonene during exponential growth phase. Growth on cellulose at 23°C and pH 5.8 produced the highest overall yield of fuel range organics (105 mg * g·biomass-1). A change in metabolism was seen in late stationary phase from catabolism of cellulose to potential oxidation of hydrocarbons resulting in the production of more oxygenated compounds with longer carbon chain length and fewer fuel-related compounds. The results outline rational strategies for controlling the composition of the fuel-like compounds by changing culturing parameters.

Working state map of hydrocarbon fuels for regenerative cooling

Regenerative cooling by endothermic hydrocarbon fuel(EHF)is one of the most promising techniques for thermal management of supersonic or hypersonic aircraft.How to maintain the fuel working in proper states is an important issue to maximize the cooling potential of EHT.This work proposes a novel working state map,including risking zone(RZ),thermal cracking zone(TCZ),supercritical zone(SupZ)and subcritical zone(SubZ),to differentiate possible working states of an EHF during regenerative cooling.Using n-decane flowing in a circular tube as an example,the boundaries of four zones are determined by numerical simulation covering different heat fluxes(0.2-4.0 MW·m^(-2))and mass flow rates(0.5-10.5 g·s^(-1))under two operating pressures(3.45 and 5.00 MPa).Empirical correlations for three boundary lines are obtained and the maximum cooling capacity is identified,as well as the identification of the pressure effect.The revelation of such new perspective of regenerative cooling is of great implication to the design and optimization of cooling system for future thermal management.

Effect of turbulence models on predicting convective heat transfer to hydrocarbon fuel at supercritical pressure

A variety of turbulence models were used to perform numerical simulations of heat transfer for hydrocarbon fuel flowing upward and downward through uniformly heated vertical pipes at supercritical pressure. Inlet temperatures varied from 373 K to 663 K, with heat flux rang- ing from 300 kW/m2 to 550 kW/m2. Comparative analyses between predicted and experimental results were used to evaluate the ability of turbulence models to respond to variable thermophysical properties of hydrocarbon fuel at supercritical pressure. It was found that the prediction performance of turbulence models is mainly determined by the damping function, which enables them to respond differently to local flow conditions. Although prediction accuracy for experimental results varied from condition to condition, the shear stress transport （SST） and launder and sharma models performed better than all other models used in the study. For very small buoyancy-influenced runs, the thermal-induced acceleration due to variations in density lead to the impairment of heat transfer occurring in the vicinity of pseudo-critical points, and heat transfer was enhanced at higher temperatures through the combined action of four thermophysical properties： density, viscosity, thermal conductivity and specific heat. For very large buoyancy- influenced runs, the thermal-induced acceleration effect was over predicted by the LS and AB models.

Investigation of flow resistance characteristics of endothermic hydrocarbon fuel under supercritical pressures

The characteristics of flow resistance of a typical hydrocarbon fuel(RP-3)flowthrough adiabatic horizontal miniature tubes at supercritical pressures are experimentallyinvestigated for both laminar and turbulent flow.The experiments are conducted by using along tube measuring section and a short tube measuring section simultaneously in order toeliminate the effect of local pressure drop.In these experiments,the temperature of RP-3changes from(295 to 789)K and the reduced pressure(P/Pc,Pc=2.33 MPa)ranges from 1 to2.58,the mass flux is up to 1572.7 kg/(m^(2).s).Test results indicate that frictional pressuredrops for various supercritical pressures at the same mass flux can be considered as equalwith each other when the reduced temperature Tb/Tpc<0.95.When Tb/Tpc>0.95,differenceappears and increases with the increase of Tb/Tpc.Additionally,the friction factor(f)of thesupercritical fluid for turbulent flow has a critical value at Tb/Tpc=1,the values of f at thispoint for all pressures and mass fluxes are equal with each other.Moreover,at the same massflux,there are two comresponding friction factors for the same Re,one is in the region of Tb/Tpc<1,the other is in the region of Tb/Tpc> 1.Finally, classical conelations of frictionfactor is inapplicable when Tb/Tpc>0.95 at supercritical pressure and a new coelation hasbeen obtained based on the experimental data.

Artificial neural network analysis of the Nusselt number and friction factor of hydrocarbon fuel under supercritical pressure

This paper presents the Nusselt number and friction factor model for hydrocarbon fuel under supercritical pressure in horizontal circular tubes using an artificial neural network(ANN)analysis on the basis of the back propagation algorithm.The derivation of the proposed model relies on a large number of experimental data obtained from the tests performed with the platform of supercritical flow and heat transfer.Different topology structures,training algo-rithms and transfer functions are employed in model optimization.The performance of the optimal ANN model is evaluated with the mean relative error,the determination coefficient,the number of iterations and the convergence time.It is demonstrated that the model has high prediction accuracy when the tansig transfer function,the Levenberg-Marquardt training algo-rithm and the three-layer topology of 4-9-1 are selected.In addition,the accuracy of the ANN model is observed to be the highest compared with other classic empirical correlations.Mean relative error values of 4.4%and 3.4%have been achieved for modeling of the Nusselt number and friction factor respectively over the whole experimental data set.The ANN model estab-lished in this paper is shown to have an excellent performance in learning ability and general-ization for characterizing the flow and heat transfer law of hydrocarbon fuel,which can provide an alternative approach for the future study of supercritical fluid characteristics and the associ-ated engineering applications.

Experimental Study of Operation Performance for Hydrocarbon Fuel Pump with Low Specific Speed

In this paper, a small flow rate hydrocarbon turbine pump was used to pressurize the fuel supply system of scramjet engine. Some experiments were carried out to investigate the characteristics of turbine pump driven by nitrogen or combustion gas under different operating conditions. A experimental database with regard to the curves of the rotational speed, mass flow rate and net head with regard to centrifugal pump were plotted. These curves were represented as functions of the pressure and temperature at turbine inlet/outlet and the throttle diameter at downstream of centrifugal pump. A sensitivity study has been carried out based on design of experiments. The experimental was employed to analyze net head of centrifugal and throttle characteristics. The research results can accumulate foundations for the close loop control system of turbine pump.

Converting rubber seed oil into hydrocarbon fuels via supported Pd-catalyst

The one-step hydrotreatment of rubber seed oil to produce hydrocarbon fuels has been carried out via supported Pd-catalyst,and analyzed emphatically some elements affected catalytic cracking process,for example,temperature,hydrogen partial pressure and dosage of catalyst,etc.Through experimental research,the author found out the appropriate catalytic cracking conditions as follows:310℃ of reaction temperature,2 MPa of hydrogen partial pressure,15 of the ratio of oil to catalyst(m(oil)/m(catalyst)),100 r/min of stirring speed.Under these conditions,effective component of hydrocarbon fuels in the converted oil accounts for 99.49%,and the proportion of C_(8)-C_(16) can reach as high as 79.61%.The converted oil was similar to petroleum-based oil in chemical composition,and can be used for future the aviation biofuels development as the source of raw material because it contains a large amount of hydrocarbon in the range of C_(8)-C_(16).

Hydrocarbon pneumonitis following fuel siphonage: A case report and literature review

BACKGROUND: People sometimes siphon fuel to fill their tanks. However, this is a potentially dangerous procedure and may cause hydrocarbon pneumonitis. We present the case of a patient with severe hydrocarbon pneumonitis after siphoning fuel. The patient underwent artifi cial ventilation and was admitted to hospital for 97 days. METHODS: We review the relevant literature for a better understanding of clinical features and management strategies for hydrocarbon pneumonitis following fuel siphonage.RESULTS: We reviewed 15 articles, which included 3 original articles and 12 case reports that reported the clinical features of fuel siphonage. In addition, we added our presented case for data analysis. A total of 40 cases were included in this review. The literature review found that hydrocarbon pneumonitis caused by fuel siphonage occurs worldwide and that most patients(80%) became symptomatic within 1 day of aspiration. Cough(70%), chest pain(62.5%), dyspnoea(55%), and fever(52.5%) presented in more than half of all patients. The right middle lobe(80%) was the predominantly involved lung fi eld; more than one-third of patients(36.7%) showed the involvement of two lobes.CONCLUSION: Patient history, computed tomographic scans of the chest, and bronchoalveolar lavage are the commonly used diagnostic tools. Supportive care remains the foundation of treatment, whereas antibiotics, steroids, and bronchoalveolar lavage are practical therapies. Patients' clinical improvement precedes the resolution of lesions on chest X-ray. Most complications arise from pulmonary lesions. The prognosis of patients suffering from hydrocarbon pneumonitis following fuel siphonage might be improved by accurate diagnosis and appropriate care.

纤维素生物质与废塑料共催化热解制取富烃液体燃料的研究进展

生物质能是国际公认的零碳可再生能源,其高效利用成为缓解能源与环境危机的关键,并对中国实现“碳达峰”和“碳中和”的目标具有重要意义。纤维素生物质与废塑料的共催化热解技术,不仅能制备高附加值的富烃液体燃料,还可达到“以废治废”的目的,进而实现生物质与废塑料的高效资源化利用。本工作从生物质与废塑料高值化利用的角度出发,对生物质和废塑料共催化热解制备富烃液体燃料的研究现状进行了综述,介绍了纤维素生物质和废塑料的基础化学特性差异,论述了废塑料种类、催化剂种类、物料和催化剂比例、催化热解温度等因素对生物质和废塑料共催化热解生物油产率和品质的影响,阐述了生物质和废塑料单独催化热解过程中的化学反应机理,并揭示了共催化热解过程中的协同反应机理,展望了该领域未来的发展方向,为生物质与废塑料的高附加值利用提供参考与思路。

吸热燃料裂解产物分析及裂解过程推测

采用全二维气相色谱-质谱联用仪(GC×GC-MS/FID)和便携式微型气相色谱仪对类JP-7吸热型碳氢燃料高温裂解气液相产物进行定性定量分析,并根据分析结果研究了裂解过程。分析结果表明,气相产物主要为氢气、甲烷、乙烯、乙烷和丙烯,较低裂解温度下的裂解液相产物主要为未裂解的原料及低分子量的链烯烃、环烯烃等不饱和烃和烷基苯类及茚类;680~700℃,裂解产物中低分子量的不饱和烃含量出现了转折,此时芳烃含量开始急剧增加;组分含量的变化表明裂解过程首先是小分子气体及低分子量烯烃的产生,其次随着裂解温度的提高,低分子量烯烃含量增加的同时又部分转化产生了芳烃的过程。

Regulating metal-acid double site balance on mesoporous SiO_(2)-Al_(2)O_(3) composite oxide for supercritical n-decane cracking

The balance between metal and acid sites directly affects the preparation of high-performance cracking catalysts with high heat sink and low coking.Nevertheless,how to control acid-metal sites balance and its relationship with cracking performance are reported scarcely.In this work,a series of Pt/Al_(2)O_(3)-SiO_(2) dual sites catalysts with different metal to acid active sites ratio(C_(M)/C_(SA))were constructed by ethanolassisted impregnation method and the impact on n-decane cracking under supercritical conditions was systematically and deeply investigated.The results showed that the conversion and carbon deposition increased gradually with varied C_(M)/C_(SA)and reached the balance at C_(M)/C_(SA)of 0.13.The proper ratio C_(M)/C_(SA)(0.13)can balance the deep dehydrogenation coking over metal active sites and high heat sink of cracking over acid active sites,the chemical heat sink reaches amazing 1.75 MJ/kg and carbon deposition is only22.03 mg/cm^(2) at 750℃.Meanwhile,the few metal sites at low C_(M)/C_(SA)and the few strong acid sites at high C_(M)/C_(SA)are the main factors limiting the cracking activity.Low C_(M)/C_(SA)limit the activation of C-H bond and deep dehydrogenation of coking precursor,resulting in relative low cracking activity and carbon deposition,while high C_(M)/C_(SA)limit the activation of C-C bond and increase the deep dehydrogenation.In this contribution,design and construction of metal-acid dual sites can not only provide the technical solution for the preparation of high heat sink and low coking cracking catalyst,but also deepen the understanding of the cracking path of hydrocarbon fuel.

Ni doped La_(0.6)Sr_(0.4)FeO_(3-δ) symmetrical electrode for solid oxide fuel cells

The conventional Ni cermet anode suffers from severe carbon deposition and sulfur poisoning when fossil fuels are used. Alternative anode materials are desired for high performance hydrocarbon fuel solid oxide fuel cells （SOFCs）. We report the rational design of a very active Ni doped La0.6Sr0.4FeO3‐δ（LSFN） electrode for hydrocarbon fuel SOFCs. Homogeneously dispersed Ni‐Fe alloy nanoparticles were in situ extruded onto the surface of the LSFN particles during the operation of the cell. Sym‐metric SOFC single cells were prepared by impregnating a LSFN precursor solution onto a YSZ （yt‐tria stabilized zirconia） monolithic cell with a subsequent heat treatment. The open circuit voltage of the LSFN symmetric cell reached 1.18 and 1.0 V in humidified C3H8 and CH4 at 750？？, respective‐ly. The peak power densities of the cells were 400 and 230 mW/cm2 in humidified C3H8 and CH4, respectively. The electrode showed good stability in long term testing, which revealed LSFN has good catalytic activity for hydrocarbon fuel oxidation.

高参数石油基和煤基火箭煤油射线法密度测量实验研究

基于Beer-Lambert定律,采用γ射线吸收法,研制了高参数火箭煤油密度测量装置,对液态及超临界压力下火箭煤油的密度进行测量方法研究。测量温度范围293~673 K,压力范围0.3~30 MPa,密度测量结果的扩展相对不确定度为2.2%~3.2%(置信因子k=2)。选取常压、温度293 K和压力5 MPa、温度673 K的环己烷分别作为高密度和低密度标准流体,抵消了温度变化对测量装置射线吸收率的影响。通过对环己烷和甲苯密度测量的校验,验证了测量方法的可靠性和准确性。在此基础上,完成了石油基和煤基火箭煤油的密度测量,并计算了石油基和煤基火箭煤油等压热膨胀系数。利用实验数据,拟合了宽广温度压力范围内两种火箭煤油密度的Tait函数关系式,密度实验数据与方程的平均绝对偏差为0.21%,最大绝对偏差为1.32%。测量结果表明:在所测量的温度和压力范围内,煤基煤油与石油基煤油的密度值基本一致。所得密度实验测量数据为高参数火箭煤油物性及传热等研究提供了基础数据。

STS304管表面“氧化+结焦”处理对碳氢燃料热解结焦的抑制作用

采用氧化或结焦方式对STS304内表面进行预处理,得到反应管O-STS304、C-STS304、OC-STS304,将其与STS304和TA管开展SEM/AFM表面形貌、表面元素XPS和导热系数等参数测试.结焦引入碳层增加了STS304内表面的粗糙度以及导热热阻,但一定程度抑制了催化结焦,同时提高了管材耐温性.采用MCH热解结焦实验发现,氧化和结焦预处理对热解影响很小,结焦处理可以显著降低催化反应管的结焦速率,5种管材的结焦速率排序为STS304>O-STS304>OC-STS304>TA>C-STS304.因此,对镍基催化反应管进行结焦预处理可以有效抑制结焦.

超临界碳氢燃料流动不稳定的频域分析与数值模拟

再生冷却通道中的流动失稳是高超声速飞行器发动机热防护技术中的核心问题之一。为研究超临界碳氢燃料在冷却通道中的流动不稳定特性,基于有限体积法及流体物性近似,发展了高效的一维瞬态模拟方法;同时,基于小扰动假设,进一步提出了用于预测稳定行为的频域分析方法。通过相关实验,验证了模型的可靠性。基于时域和频域方法的综合分析,沿内特征曲线讨论了主要失稳类型,重点分析了受密度波及Ledinegg不稳定共同影响的复合不稳定性。随后,进一步分析了工作压力和入口温度对稳定特性的耦合影响,并基于N_(tpc)-N_(spc)空间划分了稳定区域。研究发现,复合不稳定、Ledinegg不稳定以及密度波不稳定,随入口温度升高而相继消失。Ledinegg不稳定及密度波不稳定的稳定边界在N_(tpc)-N_(spc)空间具有高度相似性,而复合不稳定性的区域在较高的压力下略有缩小。

基于零维反应近似的航空煤油裂解流动模拟及误差分析

燃料裂解反应流动传热的数值模拟是先进发动机主动冷却技术研究和设计的重要手段,然而燃料裂解反应带来的巨大计算量阻碍了数值模拟的高效完成。基于集总反应模型发展简化算法是降低裂解反应流计算量的有效途径。本文建立了基于0维反应近似的数值模拟简化算法,将RP-3号航空煤油裂解反应模型需要模拟的组分方程数减少为1,计算速度提高126%。同时对简化模型带来的误差进行了详细的研究和讨论。直通道模型的对比模拟显示,简化模型与传统模型对壁温、出口流体平均温度和转化率计算结果的最大误差分别为:0.3%,0.004%,1%。折流流动模拟结果显示,简化模型对航空煤油的质量分数模拟最大误差出现在回流区,约5%;而主流区计算误差仍然可以忽略。本文可为燃料裂解反应数值模拟及主动冷却系统分析评估提供新的方法。