B.J. McCaffrey

For water spray suppression of gas well blowout fire applications reasonably large scale (1-10 MW) methane diffusion flames have been investigat:;ed near the high Froude number limit. Flame blow-off has been observed with pipe sizes to 30 rom diameter. Flame and lift-off heights, centerline temperatures and incident radiative flux to nearby targets have been measured with and without water spray suppressant. Using the Dayan-Tien formulation for a cllindrical flame model an effective gray absorption coefficient approaching 0.2 m was determined at the blow-off limit. The derived shape of the functional dependence of decreasing radiative fraction with jet Froude number in the limit is consistent with small scale experiments.

The effect of spraying water internal to the flame envelope at the base is to shift or raise the flame above its normal position and to lower peak flame temperature and radiation levels despite increased absorptivity due to the radiatively active steam. Extinguishment near blowoff is thought due to te former effect. Calculations of flame entrain.ment based on increased water vapor emission are consistent with literature estimates of entrainment when account of the effects of buoyancy due to the liquid spray is provided.

R.L. Bailee, J.J. Bednarczyk

Polyetrafluoroethylene (PTFE) reins have been used for over 30 years in high performance wire and cable applications because of their unique electrical, thermal and chemical properties. Wire insulated with PTFE is used successfully in aircraft, computers, military and industrial electronics, and other demanding applications. In some instances, however, PTFE insulation has cracked during service. The following discussion deals with this problem by comparing the stress crack resistance of six different commercial grades of PTFE resin using insulted wire samples in an accelerated stress cracking test. Results are related to important resin properties including standard specific gravity (SSG) and thermal stability (TII). A theory describing the cracking mechanism is discussed a new test for stress crack susceptibility is developed based on that theory.

David E. Lorengo, Allen Porter

This report presents data required to assess the performance and effects of the environmental control system on smoke evacuation from the cabins of large commercial jet transports during an in-flight fire.

Volume I of the study contains data for the environmental control systems (ECS) of the Boeing 707, 727, 737, 747, 757, 767, McDonnell Douglas DC.a, 'DC-9, DC-IO, Lockheed L-IOII, and Airbus A-30e, A-310. Included are descriptions of the ECS operation; airflow rates for various flight regimes; thermodynamic parameters; ducting schematics for distribution and ventilation systems; and ECS energy requirements.

Volume II presents historical data on in-flight aircraft cabin fires; jet transport certification and operating regulations relating to cabin and cockpit smoke evacuation; emergency procedures for smoke evacuation; and aircraft in-flight fire scenarios with analyses of options available to the crew.

Patricia Cahill

The vertical Bunsen burner test method, as specified in appendix F of the Federal Aviation Regulations - Part 25, was evaluated in order to update and clarify certain problem areas. Burner fuel, flame temperature and flame placement were investigated. It was determined that (1) methane gas can be used as a replacement or alternative to B-gas, (2) a minimum flame temperature specification is meaningless without specifying thermocouple wire thickness, and (3) placing the flame at the midpoint of the lower edge of the front face results in a more realistic and severe evaluation of the specimen's flammability properties.

Marino di Marzo

A model is presented that predicts major features of the evaporation of water droplets deposited on a hot non-porous solid surface. In the temperature range of interest, nucleate boiling heat transfer is fully suppressed, hence the model is only concerned with the evaporative process. In the model, the solid material is assumed to have high thermal conductivity and diffusivity, so that the surface temperature under the water droplet can be considered uniform. The temperature of this portion of a larger solid surface covered by the liquid is calculated from the classic solution for contact temperature between two semi-infinite bodies. The liquid-vapor interfacial temperature and the water-vapor molar fraction in the air at the exposed surface of the water droplet are deduced from the coupled heat and mass transfer energy balance at the interface. Spatial and temporal integration of the overall droplet energy equation is used to predict the droplet evaporation time and the instantaneous evaporation rate. Model predictions for the total evaporation time and temporal variation of the droplet volume agree well with experiments performed using a heated aluminum block. The model is used to quantify spacial and temporal heat fluXesidistribution at the exposed surface of the water droplet.