Engineering topics

Benz, F. J.

Publications and source records attributed to Benz, F. J..

12 records

NASA NTRS1991

Detonability of hydrocarbon fuels in air

Studies were conducted of the detonation of gas-phase mixtures of n-hexane and JP-4, with oxidizers as varied as air and pure oxygen, measuring detonation velocities and cell sizes as a function of stoichiometry and diluent concentration. The induction length of a one-dimensional Zeldovich-von Neumann-Doering detonation was calculated on the basis of a theoretical model that employed the reaction kinetics of the hydrocarbon fuels used. Critical energy and critical tube diameter are compared for a relative measure of the heavy hydrocarbon fuels studied; detonation sensitivity appears to increase slightly with increasing carbon number.

Beeson, H. D.↗

NASA NTRS1991

Detonation of cryogenic gaseous hydrogen-oxygen mixtures

The accidental mixing and detonation of oxygen-hydrogen mixtures is a serious aerospace industry hazard. The detonation characteristics of cryogenic mixtures of gaseous hydrogen and oxygen have accordingly been studied at various initial pressures and equivalence ratios at 100 K, and the results compared with numerical computations of idealized, steady-state, one-dimensional Zeldovich-von Neumann-Doering detonation structure with detailed chemical reaction kinetics. The predictions thus obtained for critical tube diameter, on the basis of calculated reaction-zone thickness, are found to agree reasonably well with experimental data.

Plaster, M.↗

NASA NTRS1989

Explosive fragmentation of orbiting propellant tanks

An examination is made of the in-orbit explosive characteristics of the Delta second stage and Ariane third stage, with a view to the vehicle breakups of the Ariane SPOT third-stage fuel tank in November, 1986, and of two Delta second stage tanks. Attention is given to the possible role of residual propellants in these breakups. After reviewing orbital data and comparing predicted fragment velocities with observed fragment velocities in debris patterns, a comparison has been made of total debris energy with total calculated explosion energy. Both physical and chemical explosions are deemed possible.

Benz, F. J.↗

NASA NTRS1988

Hydrazine vapor detonations

The detonation velocity and cell widths for hydrazine decomposition were measured over a wide range of temperatures and pressures. The detonation velocity in pure hydrazine was within 5 percent of the calculated C-J velocity. The detonation cell width measurements were interpreted using the Zeldovich-Doering-von Neumann model with a detailed reaction mechanism for hydrazine decomposition. Excellent agreement with experimental data for pure hydrazine was obtained using the empirical relation that detonation cell width was equal to 29 times the kinetically calculated reaction zone length.

Pedley, M. D.↗

NASA NTRS1986

Mixing of cryogenic fluids and predicted detonation properties for multiphase liquid oxygen and liquid hydrogen

The mixing and explosion of LOX and LH sub 2 is a concern for Space Transportation System operations. To understand this problem, cryogenic mixing is experimentally studied by pouring 1,2,2 trichloro 2,1,1 trifluoroethane (Freon 113) into LN sub 2, LN sub 2 into LH sub 2, and LH sub 2 into into LN sub 2 in a 1 m by 15 cm cylindrical glass vessel. Data from these experiments is compared with previous studies and a hypothesis is advanced that LOX/LH sub 2 mixing will result in a complex, heterogenous, multiphase aggregation including LOX, SOX, LH sub 2, and VH sub 2 using the multiphase hypothesis. Visual and x ray observations of the process and mass measurements are reported.

Bishop, C. V.↗

NASA NTRS1986

A comparison of the explosion hazards of hydrazine and methylhydrazine in aerospace environments

A comparison of the explosion hazards of hydrazine and methylhydrazine fuels in aerospace environments is presented. Hazards are divided into three broad areas: hazards resulting from incompatibility of the fuels with materials they might contact, hazards resulting from ignition of the fuels, and unusual hazards resulting from the wide range of pressures to which these fuels are exposed in aerospace applications.

Benz, F. J.↗

NASA NTRS1986

Friction-Testing Machine

Testing machine evaluates wear and ignition characteristics of materials in rubbing contact. Offers advantages over other laboratory methods of measuring wear because it simulates operating conditions under which material will actually be used. Machine used to determine wear characteristics, rank and select materials for service with such active oxidizers as oxygen, halogens, and oxides of nitrogen, measure wear characteristics, and determine coefficients of friction.

Benz, F. J.↗

NASA NTRS1986

Ignition of metals and alloys by high-velocity particles

The ignition of metals and alloys by impacting high-velocity particles in gaseous oxygen was investigated. A convergent/divergent nozzle was used to accelerate the flowing oxygen, which in turn accelerated the particles to velocities greater than 305 m/s (1000 ft/s). The test sample (target) was placed at the end of the chamber in the flow path. Aluminum 6061, type 316 stainless steel, type 304 stainless steel, and Inconel 718 were ignited with 1600-micron aluminum 2017 particles at elevated temperatures and pressures whereas Monel 400 could not be ignited. The ignition susceptibility of metals and alloys appeared to increase as the inlet pressure, sample temperature, and particle size were increased. Type 304 stainless steel particles required more extreme conditions for ignition of materials than similar sized aluminum particles. The results indicated that ignition and subsequent burning of the particles were required for ignition of the target materials with the possible exception of aluminum 6061.

Benz, F. J.↗

NASA NTRS1986

Ignition of metals and alloys in gaseous oxygen by frictional heating

The ignition of metals and alloys have been investigated by rotating the end of a hollow cylinder against an identical stationary cylinder on a common axis (frictional heating) in gaseous oxygen. A ranking criterion that measures the resistance of metals and alloys to ignition is discussed. It consists of the power per unit area required for ignition conveniently expressed as the product of contact pressure P and average linear velocity ALV. Data are presented that demonstrate that materials that are high in nickel and copper require greater P-ALV products for ignition (more resistant to ignition) than materials that are high in iron. Aluminum and titanium alloys are shown to require the lowest P-ALV products for ignition. The effects of varying surface velocity, contact pressure, coefficient of friction, and oxygen pressure on P-ALV products required for ignition are discussed. The results indicate that P-ALV product required for ignition increases as surface velocity increases, as contact pressure decreases, and as the coefficient of friction decreases. Increasing oxygen pressure will cause the P-ALV product required for ignition to decrease at low pressures and increase at high pressures. In some cases, the relative ranking of materials based on P-ALV products will also change as conditions are varied. The data presented in this paper are from a development program to determine the merits of using such a dynamic test method for ranking materials for oxygen service. The results to date have indicated that more testing is required before this method can be made into a standard test. The data presented do show some of the major parameters affecting the ignition of materials when exposed to frictional heating. The repeatability of the data at any set of conditions have not been thoroughly investigated.

Benz, F. J.↗

NASA NTRS1986

Burn propagation rates of metals and alloys in gaseous oxygen

The average burn rates of several metals and alloys were determined at oxygen pressures between 3.45 and 68.91 MPa (500 and 10,000 psig) and ambient temperature. Several materials were tested at elevated sample temperatures. The test materials were fabricated into solid cylindrical rods and mounted vertically in the test chamber. A magnesium igniter was positioned at the bottom end of each test specimen to promote upward burn propagations. Nickel 200 and copper 102 could not be ignited at all oxygen pressures tested whereas Monel 400 appeared to ignite but quickly self-extinguished. The other materials tested burned the entire length of the test sample. Aluminum 6061 exhibited the fastest burn propagation rate. Inconel 718 burned slower than aluminum but faster than the stainless steels (types 304 and 316). Increasing oxygen pressure generally increased the burn propagation rate of the materials. Increasing the ambient temperature of the test specimens for several materials to approximately 850 K (1070 F) had little effect upon the ignition or burn properties of nickel 200 or Monel 400. Type 316 stainless steel exhibited an increase in its burn propagation rate at this higher temperature.

Benz, F. J.↗

NASA NTRS1985

Device and method for frictionally testing materials for ignitability

Test apparatus for determining ignition characteristics of various metal in oxidizer environments simulating operating conditions for materials is invented. The test apparatus has a chamber through which the oxidizing agent flows, and means for mounting a stationary test sample therein, a powered, rotating shaft in the chamber rigidly mounts a second test sample. The shaft is axially movable to bring the samples into frictional engagement and heated to the ignition point. Instrumentation connected to the apparatus provides for observation of temperatures, pressures, loads on and speeds of the rotating shaft, and torques whereby components of stressed oxygen systems can be selected which will avoid accidental fires under working conditions.

Benz, F. J.↗

NASA NTRS1983

Alternate thermal control coolant fluid investigation for the NASA Space Transportation System

Although Freon 21 has been assumed to be the coolant fluid for both the Space Shuttle Orbiter's primary heat rejection system and Spacelab's pallet heat transport loop, the fluid's supplier has considered stopping its production. This fact, together with the recent determination that maximum allowable toxicity levels must be reduced by a factor of 100, has prompted NASA's present investigation of a Freon 21 replacement which would provide comparable heat transport/rejection capability without requiring the redesign of existing hardware. Systems performance was analytically evaluated for many fluids, together with tests establishing material compatibility with alternate fluids and the character of any synergistic effects. Test results have indicated that Freon 114 is a viable alternative for some of the systems in question.

Hueter, U.↗