09 Combustion (burners, combustion systems)

role played by extremely curved laminar flamelets in the propagation of moderately and highly turbulent flames is highlighted and the relevant physical mechanisms are discussed.

05101724 Pretreated olivine as tar removal catalyst for biomass gasifiers: investigation using naphthalene as model biomass tar Devi, L. et al. Fuel Processing Technology, 2005, 86, (6), 707-730. Biomass is considered as a potential source of renewable energy. One of the major problems for biomass gasification is the presence of tar in the product gas. This study investigated the catalytic behaviour of olivine as a prospective bed additive for biomass gasifiers for tar removal. In the present paper, the pretreatment of olivine was investigated to improve its activity. Pretreatment method includes heating olivine at 900°C in the presence of air for different treatment times. The catalytic activity of olivine was investigated via steam- reforming reaction of naphthalene as model biomass tar compound. Improvement in naphthalene conversion of around 30% was observed with 1 h of pretreatment. Also effect of pretreatment time was investigated. With increasing pretreatment time, conversion increased; more than 80% naphthalene conversion was observed with 10 h of pretreatment time for olivine. Both steam and dry reforming reaction of naphthalene formed more than 50% gaseous products over 10 h pretreated olivine. Besides the gaseous products and light tars, polymerization reactions occured producing higher tars in small quantity. Naphthalene conversion under syngas mixture was somewhat lower than that of only in steam and CO2. Apparent activation energy of 187 kJ mo1-1 was determined for 10 h pretreated olivine under gasification-gas mixture.

05•01725 Pyrolytic behavior of waste corn cob Cao, Q. et al. Bioresource Technology, 2004, 94, (1), 83 89. The powder of the agricultural waste corn cob was pyrolysed in a tube- typed stainless steel reactor of 200 ml volume under N2 atmosphere. The compositions of the gases and liquid obtained at different pyrolytic temperatures below 600°C at the heating rate of 30 K/rain were analysed. With the increment of the pyrolytic temperature, the yields of the solid and the liquid products were decreased, but the yield of gas products was increased. The liquid products were approximately 34- 40.96% (wt%), the gas products were 27-40.96% (wt%) and the solid products 23.6-31.6% (wt%). There were tess changes for the yields of these products above 600°C. The gas products were analysed by gas chromatography (GC) as CO2, CO, H2, CH4, C2H4, C3H6, C3H8, etc. When the temperature was 350-400°C, the gases had CO2 and CO 80- 95% (v/v). When the temperature increased continuously, yields of H2, CH4, C2H4, C3H6 and C3Hs gradually increased. The liquid products were identified by GC-MS as phenols, 2-furanmethanol, 2-cyclopenta- nedione, etc. The Fourier transform infra-red spectrophotometer (FT- IR) analysis of the liquid product showed a strong -OH group absorption peak. Differential thermogravimetric analysis (DTG) showed that thermal decomposition process involves two steps. The heating rate affects not only the activation energy of the decomposition reaction, but also the path of the reaction. With the increment of the heating rate, the maximum rate temperature of the decomposition reaction was shifted to a higher temperature, and the order and activation energy of the total decomposition reaction were decreasing.

05•01726 Reductive pyrolysis of Miocene-aged lignite lithotypes using MS and GC/MS detection systems for analysis of organic sulphur groups Stefanova, M. et al. Fuel, 2005, 84, (1), 71-79. The atmospheric pressure temperature programmed reduction (AP- TPR) technique, an approach for organic sulfur speciation, was extended by mass spectral detection. The coupling gave ground for precise assignment of sulfur compounds in flue gases of lignite lithotypes pyrolysed in H2 atmosphere. A broad range of suifur compounds was determined, i.e. thiols, dimethylsulphide, dimetbyldi- sulphide, CS2, thiophenes, benzothiophenes and their alkylated homologues. Certain peculiarities in organic sulfur distribution in lithotypes under study were noticed. Humovitrain was the lithotype with the highest organic sulfur content. A preponderance of aliphatic sulfur, thiols and dimethylsulfides were determined for both homo- geneous lithotypes (xylain and humovitrain). In humovitrain, addition- ally thiophenes were also identified. For heterogeneous lithotypes, liptain and humoclarain, a dominance of disulphides and an almost lack of sulphides was observed. This is an indication that with coalification a gradual loss of aliphatic sulfur functions has proceeded, where more resistant disulphides sulfur bridges turned out to be present. Thiophenes are the most abundant aromatic structures, dominating in humoclarain. Some amounts of oxidize d organic sulfur compounds (1% up to 4.1% of Sorg) were semi-quantitative determined in lithotypes using AP-TPR-MS.

05/01727 Size and charge of soot particles in rich premixed ethylene flames Maricq, M. M. Combustion and Flame, 2004, 137, (3), 340-350. A nano differential mobility analyser (DMA) is used to measure both the size and electrical charge distributions of soot particles generated during rich premixed combustion. The size distributions are bimodal. One mode peaks at diameters below the 3 nm lower limit of the nano DMA and falls off nearly exponentially with increasing particle diameter. The intensity of this mode persists with increasing height above the burner suggesting that it represents the continued formation of new particles. The second mode is lognormal in shape. Its intensity decreases and the mean diameter increases with increasing height above the burner due to coagulation and surface growth as the particles rise in the flame. The DMA measurements show that a substantial fraction of the soot particles are electrically charged in the flame, predominantly with a single charge per particle and with essentially equal numbers of positive and negative particles. These charged particles belong solely to the upper mode, whereas the lower mode remains charge neutral, suggesting that ions do not act as soot nuclei. Following soot inception, the fraction of charged particles quickly increases with height above the burner and stabilizes at ~30% of the upper mode for each polarity.

05•01728 Sulphur functionality study of steam pyrolyzed 'Mequinenza' lignite using reductive pyrolysis technique coupled with MS and GC/MS detection systems Marinov, S. P. et al. Fuel Processing Technology, 2005, 86, (5), 523-534. Atmospheric pressure-temperature programmed reduction (AP-TPR) and its analogous in oxidative atmosphere coupled 'on-line' with a mass spectrometer (MS) were used to study the behaviour of organic sulfur forms of 'Mequinenza' lignite during their mild steam pyrolysis. The obtained data were confirmed and completed by the AP-TPR-GC/MS 'off-line' analysis. Samples under study were pyrolysed at different processing parameters (temperature and flow gas). Some peculiarities in the distribution of non-thiophenic sulfur forms depending on experimental conditions were found. Namely, their amounts decreased with temperature increase at the steam treatment. The experiment performed at 500°C in water vapour flow proved the C-S bond splitting in dibenzothiophene with biphenyl formation. Sulphonic acid com- pounds were also systematically removed. At higher temperature of the steam pyrolysed treatment, this effect was more pronounced. At the same time, a relative increase in sulphones was found. The following organic sulfur species in demineralized lignite were detected by the 'offqine' AP-TPR-GC/MS technique: methyl- and benzenethiols; mono- and disulphides; alkylthiolanes; alkenyl thiophenes; alkylben- zo[b]thiophenes and alkyldibenzo[bd]thiophenes. Their relative inten- sities as a function of temperature were followed. A strong preponderance of benzo[b]thiophene and its alkytated homologues above 450°C were observed. Thiophene presence was temperature independent.

05/01729 Tracer-LIF diagnostics: quantitative measurement of fuel concentration, temperature and fuel/air ratio in practical combustion systems Schulz, C. and Sick, V. Progress in Energy and Combustion Science, 2005, 31, (1), 75-121. The safe, clean, and reliable operation of combustion devices depends to a large degree on the exact control of the fuel/air mixing process prior to ignition. Therefore, quantitative measurement techniques that characterize the state of the fresh gas mixture are crucial in modern combustion science and engineering. This paper presents the funda- mental concepts for how to devise and apply quantitative measurement techniques for studies of fuel concentration, temperature, and fuel/air ratio in practical combustion systems, with some emphasis on internal combustion engines. The paper does not attempt to provide a full literature review of quantitative imaging diagnostics for practical combustion devices; rather it focuses on explaining the concepts and illustrating these with selected examples. These examples focus on application to primarily gaseous situations. The photophysies of organic molecules is presented in an overview followed by discussions on specific details of the temperature-, pressure-, and mixture- dependence of the laser-induced fluorescence strength of aliphatic ketones, like acetone and 3-pentanone, and toluene. Models that describe the fluorescence are discussed and evaluated with respect to their functionality. Examples for quantitative applications are categor- ized in order of increased complexity. These examples include simple mixing experiments under isothermal and isobaric conditions, fuel/air mixing in engines, temperature measurements, and mixing studies where fuel and oxygen concentrations vary. A brief summary is given on measurements of fuel concentrations in multiphase systems, such as laser-induced exeiplex spectroscopy. Potentially adverse effects that added tracers might have on mixture formation, combustion, and the faithful representation of the base fuel distribution are discussed. Finally, a brief section describes alternative techniques to tracer-based measurements that allow studies of fuel/air mixing processes in

254 Fuel and Energy Abstracts July 2005

practical devices. The paper concludes with a section that addresses key issues that remain as challenges for continued research towards the improvement of quantitative, tracer-based LIF measurements.

10 ENGINES

Power generation and propulsion, electrical vehicles

05101730 Characterization and effect of using rubber seed oil as fuel in the compression ignition engines Ramadhas, A. S. et al. Renewable Energy, 2005, 30, (5), 795-803. Vegetable oils pose some problems when subjected to prolonged usage in compression ignition engines because of their high viscosity and low volatility. The common problems are poor atomization, carbon deposits, ring sticking, fuel pump failure, etc. Converting the high viscosity vegetable oil into its blends or esters can minimize these problems. The various blends of rubber seed oil and diesel were prepared and its important properties such as viscosity, calorific value, flash point, fire point, etc. were evaluated and compared with that of diesel The blends were then subjected to engine performance and emission tests and compared with that for diesel. It was found that 50- 80% of rubber seed oil blends gave the best performance. Long run tests were conducted using optimized blend and diesel. It was found that blend fuelled engine has higher carbon deposits inside combustion chamber than diesel-fuelled engine. Utilization of blends requires frequent cleaning of fuel filter, pump and the combustion chamber. Hence, it is recommended that rubber seed oil-diesel blend fuel is more suitable for rural power generation.

05101731 Corrosion studies with a new laboratory-scale system simulating large-scale diesel engines operating with residual fuels. Part I. Corrosion of Nimonic 80 A samples Lyyr~tnen; J. et al. Fuel Processing Technology, 2005, 86, (4), 353-373. A new laboratory-scale deposition-corrosion apparatus (DCA) has been designed to study the corrosion of Nimonic 80 A samples. The apparatus simulates conditions in a large-scale diesel engine operated with high sulfur- and ash-content heavy fuel oils. The fuel composition and ash particle formation were simulated with synthetic ash particles (SAP) generated by aerosol methods. The deteriorated areas, i.e. the zones under the deposits, ranged from 0 rtm at 700°C with no synthetic ash particle feed to 135 [am at 750°C with synthetic ash particle and SO2(g) feeds. A zone of 'black islands' (thickness 30 gin), i.e. internal precipitates, rich in S, Cr and Ti indicating internal sulphidation of the base material was observed at the bottom of the regions under the deposits. A comparison between a Nimonic 80 A exhaust valve from a field endurance test and material studied with this laboratory system indicated similar internal sulphidation mechanisms. Corrosion propa- gation for Nimonic 80 A is also discussed.

05/01732 Corrosion studies with a new laboratory-scale system simulating large-scale diesel engines operating with residual fuels. Part II. Particle and deposit characteristics Lyyrfinen, J. et al. Fuel Processing Technology, 2005, 86, (4), 329-352. Particle and deposit characteristics were studied with a new laboratory- scale deposition-corrosion apparatus designed to simulate the particle formation and deposition in large-scale diesel engines. Synthetic ash particles containing V, Ni, and Na are generated with an ultrasonic nebulizer. Total particle mass concentrations varied from 463 to 1739 mg/N m 3 and highest concentrations were reached with SO2(g) feed and cold dilution. Mass size distributions at the size range of 0.01-15 gm (aerodynamic size) were unimodal at 1.4/.tin. Particle morphology changed dramatically from 1 to 5 ~tm sized solid particles without SO2(g) feed into flat wet 'pools' with SO2(g) feed. It seemed that condensing sulfuric acid had dissolved the particles. Small 70-90 nm spherical particles were also observed with SOz(g) feed. On the other hand, hardly any S was found in the deposits, which indicated that S as SO2(g)/SO3(g) was transported through the deposit pile into the base material.

05101733 Effects of rim location, rim height, and tip clearance on the tip and near tip region heat transfer of a gas turbine blade Kwak, J. S. et al. International Journal of Heat and Mass Transfer, 2004, 47, (26), 5651-5663.

10 Engines (power generation and propulsion, electrical vehicles)

Effects of the rim height and the tip gap clearance on the heat transfer coefficients on the blade tip and near tip regions were measured with two different rim geometries. The heat transfer coefficient distributions were measured using the transient single colour capturing liquid crystals technique. Rims were located along (a) the pressure and the suction side (full-rim case) and (b) the suction side of the blade tip (suction side rim case). The rim heights were (a) 2.1%, (b) 4.2%, and (c) 6.3% and the blade tip gap clearances were (a) 1.0%, (b) 1.5%, and (c) 2.5% of the blade span. Tests were performed on a five-bladed linear cascade placed in a blow-down facility. The overall pressure ratio, inlet total pressure to exit static pressure, was 1.2, and the Reynolds number based on the exit velocity and the axial cord length was 1.1 × 106. The turbulence intensity level at the cascade inlet was 9.7%, and the inlet and exit Mach number were 0.25 and 0.59, respectively. It was found that higher rims reduce the heat transfer coefficients on the tip and shroud, but the reduction on the pressure and suction sides was not significant. The suction side rim case provided lower heat transfer coefficients on the blade tip and near tip regions than the full-rim case.

05•01734 FC vehicle hybridisation: an affordable solution for an energy-efficient FC powered drive train Pede, G. et al. Journal of Power Sources, 2004, 125, (2), 280-291. Fuel cells (FCs) have potential as clean and efficient energy sources for automotive applications without sacrifice in performance or driving range. However, the complete FC system must operate as efficiently as possible over the range of driving conditions that may be encountered while maintaining a low cost. To achieve this target, a storage unit can be introduced in the FC system to reduce the size of the fuel cell that is the most expensive component. This 'hybrid' concept would not only reduce the drive train total cost but it also allow the recover of the braking energy and the operation at the voltage-current point of maximum efficiency for the FC system. Pro-and-cons of the 'full-power' versus the 'hybrid' configuration are shown in this work. The 'hybridization rate' or 'hybridization degree', a parameter expressed by the relationship between two installed powers, the generation power and the traction power, is also introduced and it is demonstrated that for each category of hybrid vehicles there is an optimal value of hybridization degree. The storage systems considered are based on high power batteries or ultra capacitors (UCs) or a combination of them. A preliminary design of a sport utility vehicle (SUV) using a combined storage system and a FC energy source (called Triple Hybrid), is proposed. Finally, the experience of the Italian industry in this field is also reviewed.

05•01735 Flame chemiluminescence studies of cyclic combustion variations and air-to-fuel ratio of the reacting mixture in a lean-burn stratified-charge spark-ignition engine Aleiferis, D. G. et al. Combustion and Flame, 2004, 136, (1-2), 72 90. The operating range of lean-burn spark-ignition engines is limited by the level of cyclic variability in the early flame development that typically corresponds to the 0-5% mass fraction burned duration. An experimental investigation was undertaken to study the levels of flame chemiluminescence in an optical stratified-charge spark-ignition engine, using a Cassegrain optical system with high spatial resolution. Measurements of OH and CH-radical intensities were simultaneously acquired with double flame images per cycle for a range of air-to-fuel ratios (A/F = 12-22). These signals of chemiluminescence were used to evaluate the in-cylinder equivalence ratio of the reacting mixture and to further examine its contribution to the flame growth speed and the cyclic variability in the crank angle by which 5% mass fraction was burned (0xbS°/o). Specifically, the ratio of the OH/CH chemilumines- cence signals was calibrated in the engine and tested extensively for different injection strategies and spark advances, to measure the 'global' and 'local' in-cylinder A/F ratio around the spark plug. The complications encountered towards this goal are discussed in detail. The results showed that the equivalence ratio exhibited large variations on a cycle-by-cycle basis and consistently produced negative corre- lation coefficients with 0~bSO/o, especiai1y for lean-set operating conditions (AlE = 20-22). Particularly, for open-valve injection strategy that yielded a stratified mixture, the degree of this correlation lied in the range ~ - 0 . 4 to -0.8, being lower for the locally measured A/F ratio and higher for the globally evaluated one. Some issues related to the opposite gradients of the calibration curves deduced for the measurement of the global and local in-cylinder A/F ratios need to be examined outside the engine using a combustion facility with controlled conditions of pressure, temperature, turbulence intensity, and dilution by combustion residuals.

05/01736 Gaseous emissions from burning diesel, crude and prime bleachable summer yellow cottonseed oil in a burner for drying seedcotton Holt, G. A. and Hooker, J. D. Bioresource Technology, 2004, 92, (3), 261-267.

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