David W. Naegeli

Methylal and Methylal-Diesel Blended Fuels for Use in Compression-Ignition Engines

Gas-to-liquids catalytic conversion technologies show promise for liberating stranded natural gas reserves and for achieving energy diversity worldwide. Some gas-to-liquids products are used as transportation fuels and as blendstocks for upgrading crude derived fuels. Methylal (CH{sub 3}-O-CH{sub 2}-O-CH{sub 3}) also known as dimethoxymethane or DMM, is a gas-to-liquid chemical that has been evaluated for use as a diesel fuel component. Methylal contains 42% oxygen by weight and is soluble in diesel fuel. The physical and chemical properties of neat methylal and for blends of methylal in conventional diesel fuel are presented. Methylal was found to be more volatile than diesel fuel, and special precautions for distribution and fuel tank storage are discussed. Steady state engine tests were also performed using an unmodified Cummins 85.9 turbocharged diesel engine to examine the effect of methylal blend concentration on performance and emissions. Substantial reductions of particulate matter emissions h ave been demonstrated 3r IO to 30% blends of methylal in diesel fuel. This research indicates that methylal may be an effective blendstock for diesel fuel provided design changes are made to vehicle fuel handling systems.

Ignition Study in a Gas Turbine Combustor

Abstract Experiments were conducted in a T63 engine combustor to: (I) gain a better understanding of the roles played by fuel properties and atomization in ignition and (2) give experimental verification of assumptions used in ignition models. Ten test fuels were used, some of which were specially blended to vary either viscosity or volatility while holding the other constant. Six atomizers were used to vary the fuel spray characteristics, and average drop sizes, represented by Sauler mean diameter (SMD), were measured. Air temperatures were varied from 239 to 310K. Ignition comparisons were made by the minimum fuel-air ratios required to achieve light-off. Measurements of gas velocity and fuel-air ratio were made at the spark gap. Approximate ignition delay times were determined from high-speed photographs of the ignition process. Significant results for this combustor included: (1) viscosity, which determined atomization characteristics, was more important than volatility in the ignition process, (2) ig...

The Effect of Water on Soot Formation Chemistry

A combined, experimental and numerical program is presented. This work summarizes an internal research effort conducted at Southwest Research Institute. Meeting new, stringent emissions regulations for diesel engines requires a way to reduce NO x and soot emissions. Most emissions reduction strategies reduce one pollutant while increasing the other. Water injection is one of the few promising emissions reduction techniques with the potential to simultaneously reduce soot and NO x in diesel engines. While it is widely accepted that water reduces NO x via a thermal effect, the mechanisms behind the reduction of soot are not well understood. The water could reduce the soot via physical, thermal, or chemical effects. To aid in developing water injection strategies, this projects goal was to determine how water enters the soot formation chemistry. Linked burner experiments and modeling of a rich premixed flame were used to determine the magnitude of the thermal and chemical effect of water on soot formation and identify a possible kinetic mechanism to explain it. Following Decs model for diesel combustion processes (Dec, 1997; Flynn, et al., 1999) [1,19] , soot inception results from rich premixed combustion; thus the rich premixed flame provides an appropriate venue in which to isolate the influence of water on the kinetics. Open flame, burner experiments have been performed to quantify the soot inception point and the relative amounts of soot formation in premixed flames with and without water addition. These results have been used to expand and compliment data available in the published literature. Subsequent modeling has been used to predict trends in soot inception using currently accepted kinetic soot mechanisms. Results from this effort led to a revised kinetic mechanism for the process. Comparison of the experimental and modeling data has been used to assess the accuracy of soot formation mechanisms and ultimately has yielded a new understanding of the soot formation chemistry and the role of added water.

Effects of Flame Temperature and Fuel Composition on Soot Formation in Gas Turbine Combustors

Abstract The dependence of relative soot concentration on flame temperature and fuel composition was measured in a small-scale research combustor. The purpose was to gain a better understanding of the correlation of soot formation with H/C ratio. First, the effect of flame temperature on soot concentration was determined by varying the burner inlet temperature. Then, 10 fuels with H/C ratios in the range of 1.98 to 1.55 were used in an experiment 10 determine the effects of both flame temperature and fuel composition on relative soot concentration. Flame temperatures were calculated and measured optically by the Kurlbaum technique. Flame opacity measurements were used to determine relative soot concentration. The results showed that while soot concentration increased significantly as flame temperature increased, the ncrease in soot with fuels of lower H/C ratio was much stronger than could be attributed to associated increases in the tlame temperature.

Practical ignition limits for low molecular weight alcohols

An assessment is made of the flammability hazard of storing neat alcohols and diesel fuel/alcohol blends in fuel tanks. The immiscibility of alcohols in diesel fuel and the temperature range in which the vapour space contains a flammable mixture are discussed. Ignition limits for the C1 through C4 alcohols and alkanes, ethylene, isooctane and methylal were measured in a combustion bomb using an automotive-type spark coil as an ignition source. The effects of both temperature and pressure on the ignition limits were examined.

Army Fire-Resistant Diesel Fuel

Various means have been investigated for reducing fuel fire vulnerability of Army combat vehicles by altering fuel compositions. Extensive laboratory studies have yielded clear-to-hazy fire-resistant fuel microemulsions of water in surfactant-stabilized diesel fuel, with and without an antimist agent. The surfactant is a mixture of reaction products of diethanolamine and oleic acid. Flammability and ballistic tests reveal diminished mist flammability with self-extinguishing pool fires, even at temperatures above the base fuel flash point. No difficulties have been encountered in starting, idling, and running unmodified diesel engines on such fuels under typical operating conditions.

The Effects of Lubricant Composition on S.I. Engine Wear With Alcohol Fuels

An investigation of the effects of lubricant composition changes on spark ignition engine wear and deposits when using alcohol fuel was jointly sponsored by the U.S. Department of Energy and the U.S. Army Mobility Equipment Research and Development Command. In the work covered by this paper, tests were conducted with methanol fuel in a 2.3-liter engine using a modified ASTM Sequence V-D procedure. The baseline lubricant was a 10W-30 grade product, qualified under MIL-L-46152, for which a large amount of field and laboratory data were available. Eleven variations of the baseline lubricant were supplied and tested. The results indicate that a magnesium-based detergent additive was less effective in controlling methanol-related engine wear than was a calcium-based additive. Ashless dispersant chemistry was also determined to be of importance in controlling wear with methanol fuel. Experiments were conducted to identify the wear mechanism using the 2.3-liter engine, 20-hour steady-state test. This 20-hour test shows promise as a lubricant screening procedure when using methanol fuel.

The Effects of Alcohol Fuels and Fully Formulated Lubricants on Engine Wear

An investigation of the effects of alcohol fuels and lubricant formulations on spark ignition engine wear and deposition was made. Tests were conducted using near methanol, anhydrous ethanol, and alcohol blends as fuel in a 2.3-liter engine using a modified ASTM Sequence V-D test procedure.

The Role of Sulfur in the Thermal Stability of Jet Fuel

The autoxidation of Jet A, dodecane, and a dodecane-15%-cumene blend doped with sulfur compounds were studied at 433 K. Oxygen, hydro peroxide and soluble gum were monitored during the autoxidation. Dodecane, cumene, and the dodecane-15%-cumene blend autoxidized rapidly, while Jet A had an induction period followed by a relatively slow post autoxidation. The results suggest that an inhibitor formed early in the post autoxidation of Jet A. Gum formed in the autoxidation of Jet A, whereas none was detected in dodecane, cumene, or dodecane-15% cumene. However, gum was detected in dodecane and dodecane-15% cumene doped with thiols and disulfides. Alkyl thiols and disulfides reduced the rate of autoxidation of dodecane, and there was an induction period in the formation of gum. Traces of sulfur (≈4 ppm) inhibited the autoxidation of dodecane-15% cumene in a way that resembled the post autoxidation of Jet A. Adding an organic base increased the rate of post autoxidation in Jet A and prevented formation of the oxidation inhibitor. An inhibition mechanism is proposed in which phenois are formed via acid-catalyzed decomposition of benzylic hydro peroxides.Copyright

Synthesis and characterization of carbazole polymers exhibiting large nonlinear absorption and refractive index

Abstract Poly-(N-[1-butane 4-sulfonate benzyl triethylammonium],-3,6-carbozolyl), PNBSC, the corresponding propane sulfonate derivative, PNPSC, and poly-(N-[2-pyrimido] 3,6 carbazolyl), PCZP were synthetized as candidates for non-linear optical materials. The radical cations of these polymers were distinguished by absorbances at 850–900nm and 1300 nm which were assigned to intramer and intermer charge transfer in the carbazole radical cations. Solutions of PNBCZ and PNPCZ in 0.1 and 1 M aluminum chloride - nitrobenzene or nitromethane or 2:1 aluminum chloride-n-butyl pyridinium chloride solvents, exhibited a complex with a sharp absorption peak at 700 nm and a very broad absorption centered at 1100 nm. Since these absorption characteristics are very similar to those appearing for oxidation with one electron oxidants such as NO + in protonic acids, a similar complexation must be taking place in both cases. The nonlinear optical properties of the aluminum chloride based solutions of PNBCZ and PNPCZ and nitrobenzene solutions of the radical cation of PCZP were measured with a degenerate four wave mixing experiment at 568 nm at the minimum of the linear absorption spectrum using 10 nsec wide pulses from a dye laser. The monomer unit based, nonlinear susceptibilities γ xxxx (all beams copolarized) and γ xyyx (probe and reflected phase conjugate polarized perpendicular to the pump beams) were 3.5→2.8×10 −29 esu and 9.0→5.7 × 10 −30 esu, respectively. We thus estimate that the electronic and reorientational contributions to the x 3 is on the order of 10 −7 − 10 −8 esu. Significant nonlinear absorption was also observed at 1060 nm using 5 nsec pulses. The data could be matched to a simple linear intensity dependence of the absorption coefficient only at lower intensities, whereupon values between 10 −6 →10 −5 cm/W/M (monomer unit based) were obtained. We suspect that such large nonlinearities are obtained through the introduction of delocalized charge transfer states into the polymer chain.