生物柴油发动机非常规排放的FTIR检测

采用傅里叶变换红外光谱FTIR,研究了汽车发动机燃用生物柴油的非常规排放物。所用燃料分别为纯柴油、纯生物柴油、生物柴油掺混比为20%的B20混合燃料。结果表明,该机燃用纯柴油和B20燃油的甲醛排放差别不大,纯生物柴油的甲醛排放则明显高于柴油。燃用B20燃油的乙醛排放略低于纯柴油;纯生物柴油的乙醛排放在中低负荷低于纯柴油,在高负荷时高于柴油及B20燃油。燃用B20燃油和纯生物柴油的丙酮排放要高于柴油,但排放量均较低。随着生物柴油掺混比例的增加,发动机甲苯和二氧化硫均呈逐渐下降趋势,纯生物柴油的二氧化硫排放大幅降低。燃用生物柴油后,发动机的二氧化碳排放有所降低,表明了生物柴油有利于温室气体的控制。     

Effect of ultrasonic irradiation on the properties and performance of biodiesel produced from date seed oil used in the diesel engine

In the present study, the effect of ultrasound irradiation on the transesterification parameters, biodiesel properties, and its combustion profiles in the diesel engine was investigated. Moreover, date seed oil (DSO) was firstly utilized in the ultrasound-assisted transesterification reaction. DSO was extracted from Zahidi type date (Phoenix dactylifera) and was esterified to reduce its Free Fatty Acid (FFA) content. Biodiesel yield was optimized in both heating methods, so that the yield of 96.4% (containing 93.5% ester) at 60 °C, with 6 M ratio of methanol/oil, 1 wt% of catalyst (NaOH) and at 90 min of reaction time was reported. The ultrasound irradiation did not influence the reaction conditions except reaction time, reduced to 5 min (96.9% yield and 91.9% ester). The ultrasonic irradiation also influenced on the physicochemical properties of DSO biodiesel and improved its combustion in the diesel engine. The analysis results related to the engine and gas emission confirmed that the ultrasound-assisted produced biodiesel has lower density and viscosity, and higher oxygen content facilitating injection of fuel in the engine chamber and its combustion, respectively. Although, B40 (biodiesel blend consisting of 40% biodiesel and 60% net diesel fuel) as a blend of both fuels presented higher CO₂ and lower CO and HC in the emissions, the DSO biodiesel produced by ultrasound irradiation presented better specifications (caused about 2-fold improvement in emissions than that of conventional method). The findings of the study confirmed the positive effect of the ultrasound irradiation on the properties of the produced biodiesel along with its combustion properties in the diesel engine, consequently reducing air pollution problems.     

生物柴油高压共轨喷雾特性的试验研究

应用高速摄影系统与高压共轨系统,在高压定容器内研究了生物柴油的喷雾特性,并与柴油进行了对比。结果表明,生物柴油油束形态比柴油细且长,喷雾贯穿距离比柴油大,喷雾锥角比柴油小;高的运动黏度与表面张力导致生物柴油雾化性能比柴油差。随着喷油压力的升高,生物柴油喷雾贯穿距离变长,喷雾锥角增大;随着背压的升高,生物柴油喷雾贯穿距离...     

Quantification of Ethanol in Ethanol-Petrol and Biodiesel in Biodiesel-Diesel Blends Using Fluorescence Spectroscopy and Multivariate Methods

Ethanol blended petrol and biodiesel blended diesel are being introduced in many countries to meet the increasing demand of hydrocarbon fuels. However, technological limitations of current vehicle engine do not allow ethanol and biodiesel percentages in the blended fuel to be increased beyond a certain level. As a result quantification of ethanol in blended petrol and biodiesel in blended diesel becomes an important issue. In this work, calibration models for the quantification of ethanol in the ethanol-petrol and biodiesel in the biodiesel-diesel blends of a particular batch were made using the combination of synchronous fluorescence spectroscopy (SFS) with principal component regression (PCR) and partial least square (PLS) and excitation emission matrix fluorescence (EEMF) with N-way Partial least square (N-PLS) and unfolded-PLS. The PCR, PLS, N-PLS and unfolded-PLS calibration models were evaluated through measures like root mean square error of cross-validation (RMSECV), root mean square error of calibration (RMSEC) and square of the correlation coefficient (R ²). The prediction abilities of the models were tested using a testing set of ethanol-petrol and biodiesel-diesel blends of known ethanol and biodiesel concentrations, error in the predictions made by the models were found to be less than 2%. The obtained calibration models are highly robust and capable of estimating low as well as high concentrations of ethanol and biodiesel.     

生物柴油中微量元素的测定

介绍了全谱直读电感耦合等离子体发射光谱法(ICP-OES)测定生物柴油中Na、K、Ca、Mg、Cu、Pb、Zn、Fe、Al、Cr、Mn、Ni、V、Si与P微量元素含量。结果表明,用该法测定生物柴油中微量元素含量可评价生物柴油品质,具有操作简便、全谱直读、可同时快速测定多元素、灵敏度与精准度高等优点。77%的平均基体加标回收率处于80%—130%之间,平均相对标准偏差不超过10%的占82%。该文可为制定生物柴油新微量元素指标和补充标准提供参考。     

Design of Si–SiO<Subscript>2</Subscript> phoxonic crystal having defect layer for simultaneous sensing of biodiesel in a binary mixture of diesel through optical and acoustic waves

The potentiality of a phoxonic crystal for sensing of biodiesel in a binary mixture of diesel and biodiesel is theoretically investigated. Using the transfer matrix method, the transmission of acoustic and optical waves through a periodic one-dimensional crystal of Si–SiO₂ layers is studied. A pass band is created in the band gap region by introducing a cavity in the considered one-dimensional crystal structure. This pass band can also be considered as a defect mode, and it is found that its position is highly dependent on mole concentration of binary mixture of biodiesel and diesel present in the cavity. The sensitivity of the sensor for a binary mixture of biodiesel and diesel in the cavity with various mole concentrations is estimated. Simulated results provide a valuable guidance for designing a phoxonic crystal sensor consisting of a defect layer.     

Mobile Low-Field 1H NMR Spectroscopy Desktop Analysis of Biodiesel Production

Biodiesel produced mainly by the base-catalyzed transesterification of vegetable oils or animal fats with a short chain alcohol, has become an attractive alternative to petroleum-based diesel fuel. Even though high-field ¹H nuclear magnetic resonance (NMR) is a reliable method for biodiesel quality control, it is restricted by its poor mobility and expensive superconducting coils. As an alternative, this study presents a mobile low-field ¹H NMR spectrometer for the analysis of biodiesel samples derived from different feedstock oils. The low-field ¹H NMR spectra of all the compounds coexisting in a typical transesterification reaction such as rapeseed oil, rapeseed biodiesel, methanol, and glycerol, could be clearly differentiated. Field-dependent characteristic parameters such as relaxation times are provided. The degree of saturation of the different biofuels samples could be reliably estimated via integration of the resolved signals of the spectra. The obtained results agreed well with those measured at high-field ¹H NMR. Since this compositional information is directly related to the biodiesel properties, the presented mobile low-field ¹H NMR device built from permanent magnets arrayed in a Halbach geometry, constitutes an excellent alternative tool for biodiesel quality control.     

生物柴油/柴油颗粒的拉曼光谱分析

为了进一步降低柴油机燃用生物柴油的颗粒排放,利用激光拉曼光谱技术,研究了柴油机应用废气再循环(EGR)前后,燃烧柴油(B0)、生物柴油(B100)及其调和油(B50)的颗粒微观结构,采用五带拟合法对一阶拉曼光谱进行拟合,并计算了颗粒石墨微晶尺寸和石墨晶格C—C键长。结果表明：随着生物柴油掺混比的增加,颗粒D1带的半高宽增加,颗粒化学异相性增强;I_D1/I_G逐渐减小,颗粒中有序石墨结构含量增加,石墨化程度提高。引入EGR会使得颗粒D1带的半高宽增加,颗粒化学异相性增强;I_D1/I_G升高,颗粒有序石墨结构含量减少,石墨化程度降低,B0,B50和B100颗粒的I_D1/I_G在应用EGR前后分别降低了约8.5%,10.6%和11.8%。六种颗粒的缺陷类型主要属于石墨烯层边缘缺陷,掺混生物柴油和引入EGR均会使得颗粒碳层边缘缺陷浓度增加,颗粒中挥发性有机物的官能团含量增加,增强了颗粒氧化活性。掺混生物柴油使得颗粒石墨微晶尺寸增加,EGR使得颗粒石墨微晶尺寸减小,生物柴油和EGR对柴油机颗粒石墨晶格C—C键长影响不大,C—C键长约为0.142 nm。     

EGR率对生物柴油颗粒纳米结构的影响

为研究同时运用废气再循环(EGR)技术和燃用生物柴油对柴油机排气颗粒纳米结构的影响,分别采集0%,15%,30% EGR率下186F柴油机燃用生物柴油时的排气颗粒,并用激光拉曼光谱仪测得颗粒光谱,使用五带法对一阶拉曼光谱进行拟合,分析拟合曲线参数,计算颗粒微晶尺寸和碳碳键长度。结果表明：EGR率为30%时,生物柴油颗粒光谱的半高宽(FWHM)最大,代表化学异相性最强并且颗粒中的物质种类最多,随着EGR率降低,半高宽逐渐减小;当EGR率从0%升高到30%,I_D/I_G逐渐增大,代表石墨化程度降低,颗粒中的石墨结构减少;同时,I_D1/I_D2从0% EGR率的8左右降低到15%和30% EGR率的4左右,代表EGR率升高,颗粒内部缺陷由空位缺陷向石墨烯边缘缺陷发展;随着EGR率升高,微晶尺寸逐渐减小,碳碳键长度基本不变。     

生物柴油-生物油乳化油的燃烧排放特性

在一台未作改动的直喷式柴油机上研究了生物油质量分数分别为10%和20%的生物柴油生物油乳化油的燃烧与排放特性。结果表明:与生物柴油相比,燃用乳化油时燃烧始点推迟,预混燃烧放热峰值升高,扩散燃烧放热峰值、最高燃烧压力和燃烧温度降低,燃烧持续期缩短,且随着生物油含量增加以上趋势更明显。燃用含10%生物油的乳化油时燃油经济性较生物柴油略低,与0号柴油相当,而燃用含20%生物油的乳化油时燃油经济性则低于生物柴油和0号柴油。乳化油的NO_x排放明显低于生物柴油,而碳烟排放高于生物柴油,但低于0号柴油。     

Fluorescence as an Analytical Tool for Assessing the Conversion of Oil into Biodiesel

In this work fluorescence-based method to assess the biodiesel production from different refined vegetable oils is presented. Four different refined oils (soybean, sunflower, canola, and corn) and their respective biodiesel were used and the fluorescence of the compounds contained in their compositions was taken as a probe. The results show that the fluorescence intensity of the biodiesel is lower than one verified in the vegetable oil. The data achieved point out that the ratio between the fluorescence intensity of biodiesel and oil is about 0.6 regardless of the vegetable oil feedstock investigated. Reduced content of fluorophores as well as low viscosity of the biodiesel regarding the oil have been raised as hypotheses to explain the low fluorescence intensity of the biodiesel. The results obtained may provide the basis for the development of an alternative method able to give fast and accurate information about the conversion of oil into biodiesel without the requirement of dilution or pre-treatment of the biodiesel.     

Development of a reduced biodiesel surrogate model for compression ignition engine modeling

Methylbutanoate (MB), a C₄ methyl ester, represents the simplest surrogate that captures the chemical effects of the ester moiety in biodiesel and biodiesel surrogates. An updated chemical kinetic model has been developed to characterize the ignition and flame characteristics of MB. The mechanistic elements within this model that relate to the MB and smaller ester/oxygenate sub-mechanisms are drawn from the prototypical Fisher et al. model and from more recent theory and modeling efforts. The MB model development which is based on an iterative procedure involving global sensitivity analyses to identify elementary reactions that govern ignition and subsequent high level ab initio based theoretical updates to these reaction rates are presented. The MB model makes reasonable predictions of ignition delays and laminar flame speeds.The C₅–C₇ submechanisms from the LLNL n-heptane (NH) model were merged with the present MB model to obtain a detailed chemical kinetics model for a surrogate blend representing biodiesel. The detailed MB-NH model (661 species) was reduced using graph based techniques. The robust reduction techniques employed result in a reduced model (145 species) that is in good agreement with the detailed model over a wide range of conditions. 3-D compression ignition (CI) engine simulations utilizing this reduced chemistry model for MB-NH blends as a surrogate for biodiesel show good agreement with the experimental data suggesting the utility of this model for predictions of combustion and emission characteristics of biodiesel in realistic CI engine simulations.     

Modelling biodiesel–diesel spray combustion using multicomponent vaporization coupled with detailed fuel chemistry and soot models

A multicomponent vaporization model is integrated with detailed fuel chemistry and soot models for simulating biodiesel–diesel spray combustion. Biodiesel, a fuel mixture comprised of fatty-acid methyl esters, is an attractive alternative to diesel fuel for use in compression-ignition engines. Accurately modelling of the spray, vaporization, and combustion of the fuel mixture is critical to predicting engine performance using biodiesel. In this study, a discrete-component vaporization model was developed to simulate the vaporization of biodiesel drops. The model can predict differences in the vaporization rates of different fuel components. The model was validated by use of experimental data of the measured biodiesel drop size history and spray penetration data obtained from a constant-volume chamber. Gas phase chemical reactions were simulated using a detailed reaction mechanism that also includes PAH reactions leading to the production of soot precursors. A phenomenological multi-step soot model was utilized to predict soot emissions from biodiesel–diesel combustion. The soot model considered various steps of soot formation and destruction, such as soot inception, surface growth, coagulation, and PAH condensation, as well as oxidation by oxygen and hydroxyl-containing molecules. The overall numerical model was validated with experimental data on flame structure and soot distributions obtained from a constant-volume chamber. The model was also applied to predict combustion, soot and NOx emissions from a diesel engine using different biodiesel–diesel blends. The engine simulation results were further analysed to determine the soot emissions characteristics by use of biodiesel–diesel fuels.     

Radiation grafting of maleic anhydride onto polypropylene in solid state via ultrafine blend

A novel method to prepare maleic anhydride grafting onto poly (propylene) (PP-g-MAH) was described. It was performed by γ-irradiation in solid state via ultrafine blend in the absence of any initiator and the grafting mechanism was proposed based on the experimental results. First, ultrafine blend of MAH and PP was prepared through ultrasonic initiation in melt state and then cooled rapidly. Second, the blend was radiated by γ-irradiation in the circumstance of atmosphere. Effects of irradiation dose and MAH concentration on the amount of grafted MAH were investigated. Compared with the conventional solid-state radiation grafting method, PP-g-MAH obtained via this method shows a higher graft rate of MAH. This novel method also has the advantages of solventless, energy efficient, low cost and simple operation. Furthermore, it is very easy to get purified products. The molecular structures of grafted copolymer were characterized by Fourier-transform infrared spectroscopy. Differential scanning calorimetry, wide-angle X-ray diffraction and polarized optical microscope were used to determine the degree of crystallinity and crystalline structure.     

Biodiesel production process intensification using a rotor-stator type generator of hydrodynamic cavitation

Triglyceride transesterification for biodiesel production is a model reaction which is used to compare the conversion efficiency, yield, reaction time, energy consumption, scalability and cost estimation of different reactor technology and energy source. This work describes an efficient, fast and cost-effective procedure for biodiesel preparation using a rotating generator of hydrodynamic cavitation (HC). The base-catalyzed transesterification (methanol/sodium hydroxide) has been carried out using refined and bleached palm oil and waste vegetable cooking oil. The novel HC unit is a continuous rotor-stator type reactor in which reagents are directly fed into the controlled cavitation chamber. The high-speed rotation of the reactor creates micron-sized droplets of the immiscible reacting mixture leading to outstanding mass and heat transfer and enhancing the kinetics of the transesterification reaction which completes much more quickly than traditional methods. All the biodiesel samples obtained respect the ASTM standard and present fatty acid methyl ester contents of >99% m/m in both feedstocks. The electrical energy consumption of the HC reactor is 0.030 kW h per L of produced crude biodiesel, making this innovative technology really quite competitive. The reactor can be easily scaled-up, from producing a few hundred to thousands of liters of biodiesel per hour while avoiding the risk of orifices clogging with oil impurities, which may occur in conventional HC reactors. Furthermore it requires minimal installation space due to its compact design, which enhances overall security.     

大豆油酯交换法制备生物柴油及气相色谱分析

为获得最佳条件,在单因素试验的基础上,采用正交试验法对大豆油碱催化酯交换法制各生物柴油的工艺参数进行了优化试验,结果表明,制取生物柴油的最佳工艺参数是：醇油摩尔比6：1,催化剂用量为油量的0.8%,反应温度为45℃,反应时间60m in,并且在最优工艺参数下进行了验证试验,得到生物柴油的转化率为97.05%。气相色谱分析结果表明,脂肪酸甲酯含量很高。     

Fast,easy ethanolysis of coconut oil for biodiesel production assisted by ultrasonication

Biodiesel is a renewable fuel, consistituting an alternative to petroleum-based diesel fuel. It is non-toxic and biodegradable and has a low emission profile, is better from environmentally sensitive areas. Research study on alternative fuels is essential for increased energy security. Presently, biodiesel is produced mainly is batch reactor. In this process the required energy is given by heating accompanied by mechanical stirring which has several disadvantages because of time consuming high labour cost. Being methanol is a toxic chemical; the objective of this work is to produce coconut oil ethyl ester by using ultrasonic irradiation. The advantages of ethanol are non-toxic domestic all available, having higher carbon atoms which provide higher heat content. The optical conditions for biodiesel production is the molar ratio oil to ethanol 1:6, KOH catalyst 0.75 wt.% of oil and 7 min reaction time. The reaction time reduced 15–40 times comparing to the conventional batch processes and found ?98% biodiesel yield.     

Prediction of NOx emissions from a simplified biodiesel surrogate by applying stochastic simulation algorithms (SSA)

A stochastic simulation algorithm (SSA) approach is implemented with the components of a simplified biodiesel surrogate to predict NOx (NO and NO₂) emission concentrations from the combustion of biodiesel. The main reaction pathways were obtained by simplifying the previously derived skeletal mechanisms, including saturated methyl decenoate (MD), unsaturated methyl 5-decanoate (MD5D), and n-decane (ND). ND was added to match the energy content and the C/H/O ratio of actual biodiesel fuel. The MD/MD5D/ND surrogate model was also equipped with H₂/CO/C₁ formation mechanisms and a simplified NOx formation mechanism. The predicted model results are in good agreement with a limited number of experimental data at low-temperature combustion (LTC) conditions for three different biodiesel fuels consisting of various ratios of unsaturated and saturated methyl esters. The root mean square errors (RMSEs) of predicted values are 0.0020, 0.0018, and 0.0025 for soybean methyl ester (SME), waste cooking oil (WCO), and tallow oil (TO), respectively. The SSA model showed the potential to predict NOx emission concentrations, when the peak combustion temperature increased through the addition of ultra-low sulphur diesel (ULSD) to biodiesel. The SSA method used in this study demonstrates the possibility of reducing the computational complexity in biodiesel emissions modelling.     

柴油的透射光谱测量和热辐射物性参数反演

提出了一种基于填充柴油类半透明液体光学腔的透射光谱反演其介质光学常数的新方法(IDTM),通过测量填充水光学腔的透射光谱并反演水的光学常数进行了方法验证。采用Bruke V70傅里叶红外光谱仪实验测量了填充柴油光学腔在波长2~15 μm的透射光谱,基于新方法反演得到柴油在部分波长区域的光学常数,进而计算得到了其热辐射物性参数。研究结果表明：(1)在波段为2.0~2.5 μm,新方法(IDTM)反演水的光学常数同文献结果基本一致。(2)IDTM反演液体光学常数精度同MCDTM基本一致,且明显高于SODTM和SDTM。(3)柴油在波长2~15 μm范围透光性能较差,其中存在2.4,3.4,6.9,7.3和13.8 μm等5个强吸收区域。(4)柴油的光学常数和热辐射物性参数光谱选择性很强,在不同波段其值差距较大。     

Examination of wavelength dependent soot optical properties of diesel and diesel/rapeseed methyl ester mixture by extinction spectra analysis and LII measurements

The refractive index of soot is an essential parameter for its optical diagnostics. It is necessary for quantitative interpretation of LII (Laser Induced Incandescence) signals, light scattering or extinction measurements as well as for emissivity calculations. The most cited values have been determined by intrusive methods or without taking into account the soot size distribution and its specific morphology. In the present study, soot generated by the combustion of diesel and diesel/rapeseed methyl ester (RME) mixture (70% diesel and 30% RME) are extensively characterized by taking into account the morphology, the aggregate size distribution, the mass fraction and the spectral dispersion of light. The refractive index m for wavelengths λ between 300 and 1000 nm is determined for diesel and diester fuels by both in-situ and ex-situ methods. The ex-situ method is based on the interpretation of extinction spectra by taking into account soot sizes and fractal morphology with the RDG-FA (Rayleigh–Debye–Gans for Fractal Aggregate) theory. The in-situ approach is based on the comparison of the LII signals obtained with two different excitation wavelengths. The absorption function E(m) and the scattering function F(m) are examined. This study reveals similar optical properties of soot particles generated by both studied fuels even at ambient and flame temperatures. The function E(m) is shown to reach a maximum for λ=250 nm and to tend toward a plateau-like behavior close to E(m)=0.3 for higher wavelength (600<λ (nm)<1000). The function F(m) is found to be quite constant for 400<λ (nm)<1000 and equal to 0.31.