Engineering topics

Dryer, Frederick L.

Publications and source records attributed to Dryer, Frederick L..

21 records · Page 2

NASA NTRS1991

Some further observations on droplet combustion characteristics - NASA LeRC-Princeton results

Experimental and numerical studies are reviewed which are designed to examine the effects of droplet/gas motion, product-intermediate absorption, extinction, and sooting on droplet combustion. The experimental work at the NASA-Lewis Research Center involves a 2.2-s droptower for investigating microgravitational effects of droplet combustion over a relatively extended range. The droplet-gas velocities are very low because the spherosymmetrical nature of the major combustion processes produces a quiescent environment. The refined experimental results are combined with numerical modeling based on a technique that is fully transient, comprehensive, and has few empirical simplifications. The combination of techniques improves the present understanding of convection-induced effects, reducing soot formation, and promoting quiescent droplet combustion.

Choi, Mun Y.↗

NASA NTRS1991

Observations on a Slow Burning Regime for Hydrocarbon Droplets - N-Heptane/Air Results

Experiments on n-heptane/airdroplet combustion under reduced gravity have served as a benchmark for much of the existing theoretical efforts on the modeling of sphero-synmmetric droplet burning. New experiments conducted in the NASA-Lewis Research Center 2.2 second droptower (at less than 10 exp -5 g) which emphasize the production of sphero-symmetry and low relative droplet/gas convection produce burning rates in air (for about 1 mm droplets) as much as 40-percent lower than the classical result (0.78 sq mm/s). The burning rate is proportional to the measured droplet/gas relative velocity, and the observed functional dependence is much larger than predicted by published convective correlations. New results clearly indicate that the droplet/laboratory velocity does not correspond to the relative droplet/gas velocity. Thus, the convective effects on droplet combustion is not properly characterized by droplet motion alone. Differences in the burning rates are speculated to result from the effects of the accumulated soot as well as the asymmetry (caused by convection) in the temperature and species distributions surrounding the droplet.

Choi, Mun Y.↗

NASA NTRS1990

N-Decane-Air Droplet Combustion Experiments in the NASA-Lewis 5 Second Zero-Gravity Facility

The burning of single fuel (n-decane) droplets in a microgravity environment (below 0.00001 of the earth's gravity, achieved in the NASA-Lewis 5-Second Zero-Gravity Facility) was studied, as part of the development of the Droplet Combustion Experiment for eventual operation aboard either the Shuttle middeck or Spacelab. Special attention is given to the combustion equipment used and its operations and performance. Temporal analysis of the local burning rates in these tests showed increasing rates of change in the local burning as droplet combustion progressed. Result point to the need of studying large droplets, with long droplet combustion lifetimes as well as low gas/droplet motion to understand reasons for this unsteadiness.

Haggard, John B.↗