发动机燃用生物柴油的核态颗粒排放

以一台电控高压共轨柴油机为样机,使用排气颗粒数量及粒径分析仪EEPS,研究了发动机燃用生物柴油的核态颗粒排放特性。所用燃油为纯柴油、生物柴油掺混配比分别为5%、10%和20%的B5、B10和B20燃料。结果表明:发动机排气颗粒数量随粒径变化呈现明显的单峰或双峰对数分布形态,核态颗粒的峰值粒径在6 nm至10 nm之间。生物柴油配比上升,增加了该机核态颗粒的峰值数量浓度,颗粒总数量浓度大都呈持续上升趋势,其中核态颗粒数量增加占有主导因素;在低负荷燃用低配比生物柴油燃料时,B10燃油的颗粒总数量浓度最低。     

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。     

油品对DMCC甲醛排放的比较研究

为了研究甲醇燃料发动机尾气中甲醛的排放特征,在一台经过改装的组合燃烧发动机上,采用标准测试柴油(TF)和普通市场柴油(MF)进行了实验,比较了燃用不同油料时的甲醛排放特征.实验结果表明;在相同甲醇掺烧比时,两种油料均是在低负荷时甲醛排放最高,在中负荷时最低,在高负荷时甲醛排放居中,三种负荷下MF甲醛排放均比TF高;此外,实验还对比了相同负荷、不同甲醇掺烧比时的甲醛排放,均表现出MF的甲醛排放比TF高,在高负荷下甚至达到2.5倍;实验还表明单纯的依靠氧化催化转化器不能有效降低甲醛排放.     

发动机采用柴油／甲醇组合燃烧的性能研究

分别在增压和自然吸气式高速直喷柴油机上采用柴油/甲醇组合燃烧方式进行研究.试验结果表明,采用组合燃烧后发动机和纯柴油燃烧发动机相比,尾气中NOx和碳烟排放显著减少,消耗燃料的比能耗降低,组合燃烧用燃料的使用经济性优予原机;仅未燃碳氢和一氧化碳较原机有所增加,但是由于排气温度高于催化转换器起燃温度,可以通过催化转换器将其转化.     

基于激光诱导炽光法的生物柴油碳烟测量

生物柴油的原料多元化,制备出的生物柴油理化特性也大不相同,因此其污染物排放特性需进一步研究。本文利用基于消光法标定的激光诱导炽光技术来测量一系列生物柴油的碳烟体积分数,以探究含氧生物燃料与传统柴油掺混后的基础碳烟排放特性。结果表明,纯含氧生物燃料的碳烟体积分数峰值较低,仅为传统柴油的7.1%～30.5%。碳烟的形成随着生物柴油掺混比例增加而呈下降趋势,与含氧燃料掺混传统柴油的碳烟排放特性一致,而不饱和度较高的生物燃料更倾向于更多的碳烟排放。生物柴油产生的粒径颗粒相对较小,比传统柴油小了大约9.5%～41.3%。碳烟颗粒物形貌方面,生物柴油与传统柴油均呈现出团簇结构,而高饱和度的生物柴油产生的碳烟颗粒粒径相对较大,但数量密度较低。     

燃用天然气合成油增压柴油机特性研究

在一台增压中冷柴油机上分别燃用常规柴油与代用燃料天然气合成油(GTL),供油提前角分别设为上止点前9°和12°CA,对比研究了燃用这两种燃料的柴油机动力性、经济性、燃烧和排放特性.与柴油相比,燃用GTL的柴油机有效功率和转矩不变,有效燃油油耗率降低,有效热效率相当;GTL的最高燃烧压力和放热率峰值均略低,GTL的着火时刻、缸压和放热率峰值出现时刻均略晚,燃烧持续期略长;与柴油相比,在试验工况下GTL平均降低了16.6%HC、14.5%CO、15.7%碳烟和15.1%NOx排放.试验结果显示GTL是一种有潜力的低排放代用燃料.     

预混火焰条件下生物柴油羰基物的生成与影响因素分析

羰基物是低温燃烧过程中产生的不完全氧化中间产物,主要产生在预混燃烧阶段。从化学反应动力学角度,分析了预混火焰条件下,燃油量、过量空气系数和调合比例等因素对生物柴油羰基物生成的影响。通过改变空气稀释比进行空气预处理,通过掺混氢气、掺混一氧化碳、掺混甲烷进行燃料预处理,对生物柴油羰基类污染物的排放控制进行了数值模拟。研究结...     

玉米秸秆生物油-柴油乳化油的燃烧特性

试验用生物油是玉米秸秆快速热解液化的产物,主要成分为含氧有机混合物和水,不宜直接作为燃料使用,但与柴油乳化后可实现其在发动机中应用.在一台未作改动的直喷式柴油机上研究了玉米秸秆生物油质量分数分别为10%(B10)和20%(B20)的生物油-柴油乳化油的燃烧特性.结果表明:与0号柴油相比,乳化油的滞燃期延长,预混燃烧放热...     

柴油掺混正丁醇对火焰发展及光谱的影响

正丁醇是一种很有前景的柴油替代燃料,针对缸内火焰发展和燃烧中间产物的自发光光谱开展研究,有助于深入理解柴油掺混正丁醇混合燃料对柴油机燃烧过程的影响规律。因此,在一台光学发动机上,利用火焰高速成像技术和自发光光谱分析法,研究纯柴油与柴油掺混不同比例正丁醇后对发动机缸内火焰发展和自发光光谱的影响。试验过程中,光学发动机转速为1 200 r·min~(-1),喷油压力为600 bar,进气加热到398 K,使上止点附近达到约900 K温度。纯柴油、柴油掺混20%正丁醇燃料和柴油掺混40%正丁醇燃料分别用D100, DB20和DB40表示,三种燃料在每个着火循环喷入的油量分别为17.5, 18.7和19.2 mg,从而保证发动机输出功相同。试验结果表明:冷却水温不变时,喷油时刻推迟,滞燃期缩短,初始火核形成时刻推迟,蓝色预混火焰比例减小;喷油时刻不变时,提高冷却水温度,滞燃期缩短,初始火核形成时刻提前,蓝色预混火焰比例减小。随着正丁醇掺混比例增加,呈现局部混合气率先着火的特征且着火时刻推迟,蓝色预混火焰比例增加,火焰亮度降低,火焰亮度从大到小依次为:D100DB20DB40。D100燃料随喷油推迟,整体光谱的峰值向长波方向移动,碳烟辐射增强, OH谱带的光强峰值先增大后减小, OH和CH_2O谱带出现的时刻推迟,表明高温和低温反应时刻推迟;喷油时刻不变时,提高冷却水温,整体光谱的光强增加, OH和CH_2O谱带的出现时刻提前,表明高温和低温反应时刻提前。掺混正丁醇后的DB40燃料随喷油推迟,光谱的整体光强增加, OH和CH_2O谱带的光强峰值提高,表明推迟喷油对DB40燃料也是有助于促进高温和低温反应。DB40燃料光谱的整体光强低于D100燃料,其OH和CH_2O的谱带出现的时刻迟于D100燃料,表明掺混正丁醇后燃料的高温和低温反应时刻都相对D100燃料推迟。SOI-15、冷却水温95℃工况下, D100燃料的谱线经过2℃A就呈现出了类似碳烟黑体辐射谱的特征,而DB40燃料先呈现出CO氧化连续谱的特征,经过15℃A才呈现碳烟黑体辐射谱的特征。     

生物制气-柴油双燃料发动机燃烧特性研究

各种农林废弃的生物质,经气化炉热解气化产生可燃生物制气,作为柴油为引燃燃料的双燃料发动机主要燃料,测量该发动机及柴油机在运转范围内的燃烧过程,并分析燃烧始点、最高燃烧压力及相位的变化规律。双燃料发动机与燃用纯柴油时的发动机相比,燃烧始点较迟,在低速大负荷时比柴油机气缸最高燃烧压力及最大压力升高率要大,在其余工况比柴油机要低。     

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.     

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.     

Butanol–acetone mixture blended with cottonseed biodiesel: Spray characteristics evolution,combustion characteristics,engine performance and emission

Increasing energy demands and more stringent legislation relating to pollutants such as nitrogen oxide (NO_x) and carbon monoxide (CO) from fossil fuels have accelerated the use of biofuels such as biodiesel. However, current limitations of using biodiesel as an alternative fuel for CI engines include a higher viscosity and higher NO_x emissions. This is a major issue that could be improved by blending biodiesel with alcohols. This paper investigates the effect of a butanol–acetone mixture (BA) as an additive blended with biodiesel to improve the latter's properties. Macroscopic spray characteristics (spray penetration, spray cone angle and spray volume) were measured in constant volume vessel (CVV) at two injection pressures. A high-speed camera was used to record spray images. The spray's edge was determined using an automatic threshold calculation algorithm to locate the spray outline (edge) from the binary images. In addition, an engine test was carried out experimentally on a single-cylinder diesel engine. The engine's performance was measured using in-cylinder pressure, brake power (BP) and specific fuel consumption (SFC). Emission characteristics NO_x, CO and UHC were also measured. Neat biodiesel and three blends of biodiesel with up to 30% added BA were tested. The experimental data were analyzed via ANOVA to evaluate whether variations in parameters due to the different fuels were significant. The results showed that BA can enhance the spray characteristics of biodiesel by increasing both the spray penetration length and the contact surface area, thereby improving air–fuel mixing. The peak in-cylinder pressure for 30% BA was comparable to neat diesel and higher than that of neat biodiesel. Brake power (BP) was slightly improved for 10% BA at an engine speed of 2000 rpm while SFC was not significantly higher for any of the BA-biodiesel blends because of the smaller heating value of BA. Comparing the effect on emissions of adding BA to biodiesel, increasing the amount of BA reduced NO_x and CO (7%) and (40%) respectively compared to neat biodiesel, but increased UHC.     

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.     

DMM及纳米颗粒添加剂对农用柴油机燃烧与排放性能的影响

本文通过在柴油中添加小比例二甲氧基甲烷(DMM)以及纳米氧化铝(Al2O3)颗粒研究一台小型农用柴油机的燃烧与排放特性。研究表明,随着柴油中DMM添加比例的增大,发动机燃烧特性参数如缸内压力、燃烧放热率及制动热效率得到明显地提升,着火延迟期以及CA50逐渐减小;排放方面HC和NOx增加,而CO和碳烟得到有效地抑制。燃油中同时添加DMM和纳米Al2O3颗粒后,发动机燃烧及排放方面得到了不同程度地优化。因此,将DMM与纳米颗粒的有机结合可为代用燃料在农用发动机中的推广应用提供新的思路。     

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.     

An experimental investigation on spray, ignition and combustion characteristics of biodiesels

Spray, ignition and combustion characteristics of biodiesel fuels were investigated under a simulated diesel-engine condition (885 K, 4 MPa) in a constant volume combustion vessel. Two biodiesel fuels originated from palm oil and used cooking oil were used while JIS#2 used as the base fuel. Spray images were taken by a high speed video camera by using Mie-scattering method to measure liquid phase penetration and liquid length. An image intensifier combined with OH filter was used to obtain OH radical image near 313 nm. Ignition and combustion characteristics were studied by OH radical images. Biodiesel fuels give appreciably longer liquid lengths and shorter ignition delays. At low injection pressure (100 MPa), biodiesel fuels give shorter lift-off lengths than those of diesel. While at high injection pressure (200 MPa), the lift-off length of biodiesel fuel originated palm oil gives the shortest value and that of biodiesel from used cooking oil gives the longest one. Air entrainment upstream of lift-off length of three fuels was estimated and compared to soot formation distance. This study reveals that the viscosity and ignition quality of biodiesel fuel have great influences on jet flame structure and soot formation tendency.     

含甲缩醛柴油喷雾和燃烧排放特性的试验研究

应用激光相位多普勒技术测量了含甲缩醛柴油喷雾的速度场和粒径场,在直喷式柴油机上研究了该含氧混合燃油的燃烧排放特性。结果表明,添加甲缩醛可改善柴油的雾化,增加喷雾轴线上的粒子速度,但减小喷雾锥角;同时以远大于其加入的比例降低柴油机排气烟度,但对氮氧化物的排放影响不大。柴油机采用甲缩醛作燃油添加剂时,需改造燃油系统。     

Experimental and kinetic modeling studies on the auto-ignition of methyl crotonate at high pressures and intermediate temperatures

Biofuels, including biodiesel have the potential to partially replace the conventional diesel fuels for low-temperature combustion engine applications to reduce the CO₂ emission. Due to the long chain lengths and high molecular weights of the biodiesel components, it is quite challenging to study the biodiesel combustion experimentally and computationally. Methyl crotonate, a short unsaturated fatty acid methyl ester (FAME) is chosen for this chemical kinetic study as it is considered as a model biodiesel fuel. Auto-ignition experiments were performed in a rapid compression machine (RCM) at pressures of 20 and 40 bar under diluted conditions over a temperature range between 900 and 1074 K, and at different equivalence ratios (? = 0.25, 0.5 and 1.0). A chemical kinetic mechanism is chosen from literature (Gaïl et al. 2008) and is modified to incorporate the low-temperature pathways. The mechanism is validated against existing shock tube data (Bennadji et al. 2009) and the present RCM data. The updated mechanism shows satisfactory agreement with the experimental data with significant improvements in low-temperature ignition behavior. The key reactions at various combustion conditions and the improved reactivity of the modified mechanism are analyzed by performing sensitivity and path flux analysis. This study depicts the importance of low-temperature pathways in predicting the ignition behavior of methyl crotonate at intermediate and low temperatures.     

Surrogate formulation for diesel and jet fuels using the minimalist functional group (MFG) approach

Surrogate fuels aim to reproduce real fuel combustion characteristics in order to enable predictive simulations and fuel/engine design. In this work, surrogate mixtures were formulated for three diesel fuels (Coryton Euro and Coryton US-2D certification grade and Saudi pump grade) and two jet fuels (POSF 4658 and POSF 4734) using the minimalist functional group (MFG) approach, a method recently developed and tested for gasoline fuels. The diesel and jet fuel surrogates were formulated by matching five important functional groups, while minimizing the surrogate components to two species. Another molecular parameter, called as branching index (BI), which denotes the degree of branching was also used as a matching criterion. The present works aims to test the ability of the MFG surrogate methodology for high molecular weight fuels (e.g., jet and diesel). ¹H Nuclear Magnetic Resonance (NMR) spectroscopy was used to analyze the composition of the groups in diesel fuels, and those in jet fuels were evaluated using the molecular data obtained from published literature. The MFG surrogates were experimentally evaluated in an ignition quality tester (IQT), wherein ignition delay times (IDT) and derived cetane number (DCN) were measured. Physical properties, namely, average molecular weight (AMW) and density, and thermochemical properties, namely, heat of combustion and H/C ratio were also compared. The results show that the MFG surrogates were able to reproduce the combustion properties of the above fuels, and we demonstrate that fewer species in surrogates can be as effective as more complex surrogates. We conclude that the MFG approach can radically simplify the surrogate formulation process, significantly reduce the cost and time associated with the development of chemical kinetic models, and facilitate surrogate testing.