Propane Fuels Research Articles

Flame-jet ignition of large fuel-air clouds

This paper reports on a series of large-scale flame-jet ignition tests conducted at the Defense Research Establishment Suffield in Canada. The experimental configuration consisted of a steel tube connected to a large plastic bag simulating an unconfined region. The test volumes were filled with fuel-air mixtures employing acetylene, ethylene, propane and vinyl chloride monomer fuels. The nature of the flame jet was controlled by an array of obstacles in the tube and, in many of the tests, by a central circular blockage installed in the exit plane of the tube. Transition to detonation was observed in the bag for acetylene-air mixtures under a variety of geometric conditions. In the case of a flame jet emerging from an open tube, high-speed cinematography and numerical calculations have shown that the entrainment of hot combustion products into the vortex established by the shock-induced flow ahead of the flame is responsible for a sequence of localized explosions which result in shock wave amplification sufficient to initiate detonation. Other modes of transition were observed with the acetylene-air system, including transition downstream of a central blockage, transition due to colliding flame tongues in an asymmetric jet, and transition due to flame/boundary interactions. When the data from all of these experiments are plotted in terms of flame-jet velocity versus the sensitivity of the mixture to detonation, they describe a well-defined relationship. Successful correlation of this diversity of data would suggest that the critical conditions are established by the flame jet and that nearby perturbing boundaries merely trigger the onset of detonation. Although transition to detonation was not observed with the other fuel-air systems, it was found that a significant explosion in the bag could nonetheless occur for the relatively sensitive ethylene-air system, generating pressures approaching 6 bar. Cinematographic coverage has revealed that this is likely the result of a series of “hot spots” or regions of high reactivity developing downstream of the tube exit. Although these mini-explosions do not persist long enough for the critical size of a detonation kernel to be exceeded, the resulting reactive blast wave takes considerable time to decay.

Turbulent flame propagation and transition to detonation in large fuel-air clouds

The results of a series of flame acceleration tests performed in a top-vented channel, 1.8m× 1.8 m in cross-section and 15.5 m long, with repeated obstacles are reported. The tests were performed in order to assess the potential for flame acceleration and transition to detonation following an accidental spill of gaseous fuel in simulated industrial environments with repeated obstacles. Tests were performed with acetylene, propane and hydrogen sulphide fuels mixed with air. For near stoichiometric acetylene-air, the flame accelerates continuously as it propagates down the channel reaching speeds between 180 and 400 m/s prior to the occurrence of localized explosions which trigger the onset of detonation. The behavior of flames in lean acetylene (5.2% C2H2)-, propane- and hydrogen sulphide-air mixtures is much less dramatic. The observed flame speeds range from about 25 m/s up to 200 m/s, with associated peak overpressures typically less than 50 mbar. The continuous flame acceleration observed in stoichiometric acetylene-air is not observed in these mixtures. Based on these results it is concluded that the potential for flame acceleration and transition to detonation in the move open areas of a chemical plant is much smaller than in the heavily confined areas. The fact that flames in stoichiometric acetylene-air accelerate and produce detonations in these obstacle environments shows that the potential for damaging explosions does exist. However, higher levels of confinement, stronger ignition sources or denser obstacle configurations than in the present tests are required to produce such explosions in less sensitive mixtures. The results of numerical simulations of the turbulent flame propagation are also reported and compared with the observed results. These simulations successfully describe many of the observed phenomena. In particular, the flame acceleration in acetylene-air mixtures and the absence of similar flame acceleration in propane- and hydrogen sulphide-air mixtures are predicted.

Radiation properties of soot from premixed flat flame

The spectroscopic analysis of the radiation from luminous flames burning propane and methane fuels were carried out in the wavelength range from 0.4 μm to 5 μm and monochromatic spectra of the radiation from the soot particle cloud were measured. A large discrepancy between experimental and predicted κ λ from Mie theory is observed. Calculations from Mie theory were performed to clarify the effect of the shape, size, and complex refractive index of soot particles.

Comparison of methane and propane rockets

Martin (1983) compared methane and propane fuels for a single-stage-to-orbit vehicle, demonstrating a significant advantage for propane. Attention is presently given to the ways that this comparison changes when both methane and propane vehicles are optimized. It is found that while the difference is slightly reduced, propane remains the better hydrocarbon fuel for dry mass minimization.

Spectral optical constants of soots from polarized angular reflectance measurements

The optical constants of carbonaceous materials derived from different types of fuel were determined by a polarized ratio reflectance technique over a spectral range of 0.5–0.75 μm and variable incident angles to compare the relative influence of composition independent of particle size and size distribution. Optical properties of soots from acetylene, propane, and kerosene fuels and from a carbon black were measured in the 0.5–0.75-μm spectral range and the spectral optical constants calculated. Differences in optical constants were observed for soots derived from different types of fuel and for soots derived from the same type fuel when volatile adsorbed species were removed by exposure to vacuum.

Two-stage earth-to-orbit vehicles with dual-fuel Orbiter propulsion

Earth-to-orbit vehicle studies of future replacements for the Space Shuttle are needed to guide technology development. Previous studies that have examined single-stage vehicles have shown advantages for dual-fuel propulsion. Previous two-stage system studies have assumed all-hydrogen fuel for the orbiters. The present study examined dual-fuel orbiters and found that the system dry mass could be reduced with this concept. The possibility of staging the booster at a staging velocity low enough to allow coastback to the launch site ts shown to be beneficial, particularly in combination with a dual-fuel orbiter. An engine evaluation indicated the same ranking of engines as a previous single-stage study. Propane and RP-1 fuels result in lower vehicle dry mass than methane, and staged-combustion engines are preferred over gas-generator engines. The sensitivity to the engine selection is less for two-stage systems than for single-stage systems.

Deposit Formation in Hydrocarbon Fuels

A high-pressure fuel coking test apparatus was designed and developed and was used to evaluate thermal decomposition (coking) limits and carbon deposition rates in heated copper tubes for two hydrocarbon fuels, RP-1 and commercial-grade propane. Tests were also conducted using JP-7 and chemically-pure propane as being representative of more refined cuts of the baseline fuels. A parametric evaluation of fuel thermal stability was performed at pressures of 136 atm to 340 atm, bulk fuel velocities in the range 6–30 m/s and tube wall temperatures in the range 422–811 K. In addition, the effect of the inside wall material on deposit formation was evaluated in selected tests which were conducted using nickel-plated tubes. The results of the tests indicated that substantial deposit formation occurs with RP-1 fuel at wall temperatures between 600 and 800 K, with peak deposit formation occurring near 700 K. No improvements were obtained when deoxygenated JP-7 fuel was substituted for RP-1. The carbon deposition rates for the propane fuels were generally higher than those obtained for either of the kerosene fuels at any given wall temperature. Finally, plating the inside wall of the tubes with nickel was found to significantly reduce carbon deposition rates for RP-1 fuel.

Ignition and flame quenching in flowing gaseous mixtures

The influence of pressure, velocity, turbulence intensity, turbulence scale and mixture composition on minimum ignition energy and quenching distance in flowing gaseous mixtures is examined experimentally for methane and propane fuels. In some experiments, the nitrogen in the air is replaced by various inert gases such as carbon dioxide, helium or argon, while in others the nitrogen is either partly or totally replaced by oxygen. The tests are conducted at room temperature in a 9 cm square working section through which the combustible mixture is arranged to flow at various levels of pressure, turbulence and velocity. At each test condition, the spark energy required to ignite the flowing mixture is measured for several gap widths in order to establish the optimum gap width corresponding to minimum ignition energy. From analysis of the relevant combustion and heat transfer processes involved, expressions for the prediction of quenching distance in flowing mixtures are derived. Support for the model employed in this analysis is demonstrated by a close level of agreement between theoretical predictions of quenching distance and corresponding values calculated from the experimental data on minimum ignition energy obtained over a wide range of mixture compositions and flow conditions.

The Energy Crisis: Reflection and Perspective — Part I, Reflection

As this is being written, the motion-picture and television industries, along with most others, are greatly concerned with the “energy crisis.” Suddenly there are shortages, imminent or actual, of almost every source of energy needed to keep our economy functioning. We have, or we forsee, shortages of electrical power and of gasoline, heating oil, propane and other fuels — all of which arc produced by or derived from petroleum. Moreover, we face shortages or projected shortages of plastics, petrochemicals, and other essential materials which arc also derived from oil. As a result, we are beginning to realize that no other crisis in recent years has portended such a drastic effect upon industrial-nation economics as this energy crisis — not gold crises, not import-export crises, not labor crises — nothing.

Platinum as a Propane Fuel Cell Electrocatalyst

Platinum as a Propane Fuel Cell Electrocatalyst

Discussion of “A High Performance Propane Fuel Cell Operating in the Temperature Range of 150–200°C” [W. T. Grubb and C. J. Michalske (pp. 1015–1019, Vol. 111, No. 9)

not Available.

Closure to “Discussion of ‘A High Performance Propane Fuel Cell Operating in the Temperature Range of 150–200°C’ [W. T. Grubb and C. J. Michalske (pp. 1015–1019, Vol. 111, No. 9)

not Available.

Influence of Gasoline and Propane Fuels on Spark-Ignition Engine Wear Rates During Low-Temperature Operation

Influence of Gasoline and Propane Fuels on Spark-Ignition Engine Wear Rates During Low-Temperature Operation

A High Performance Propane Fuel Cell Operating in the Temperature Range of 150°–200°C

High performance and complete electro‐oxidation of propane have been achieved in fuel cells operating in the range . The cells contain platinum catalyzed electrodes and concentrated phosphoric acid electrolytes. For best performances the electrolyte concentration and operating temperature are selected so that the partial pressure of water vapor over the electrolyte is in the vicinity of 600 mm. Observing this condition, complete propane‐oxygen fuel cells produced 50 ma/cm2 at 0.5v cell potential (with Ohmic resistance losses included) at 200°C. The mechanism of the electro‐oxidation of propane is discussed.

High-performance Propane Fuel Cells

IN April 1963, a high-performance fuel cell for saturated hydrocarbons was announced1. The cell contained platinum electrodes, a phosphoric acid electrolyte, and operated in the range 150°–200° C. It was noted also that a number of hydrocarbons, including methane, propane, n-octane, and n-cetane, could be utilized by the cell with complete oxidation to carbon dioxide and water being achieved. More recently an E.M.F.-current density curve and carbon dioxide yield data were published for a propane–oxygen fuel cell operating at 150° C with an electrolyte of 85 per cent (14.6 M) H3PO4 (refs. 2 and 3).