All military munitions or energetic compounds must pass a liquid-fuel fire test. The liquid-fuel fire test consists of exposing a full-scale ordnance item to a liquid-fuel fire to assess the violence of reaction and susceptibility of the item to a fire that may result from an accident due to transportation, storage, and/or a mishap on the deck of an aircraft carrier. The liquid-fuel fire test is required for both hazard classification and insensitive munitions (IM). However, increasing environmental concerns with respect to air quality and soil and groundwater contamination have begun to impact the ability of the United States and other nations to perform the liquid-fuel fire test. Limitations are being placed on where and how the test can be conducted. To address these environmental concerns, propane is being considered as an alternative to kerosene-based fuels.

This project will demonstrate and validate the use of propane as a viable alternative to kerosene-based fuels for the liquid-fuel fire test. Work will be coordinated with the Department of Defense Explosive Safety Board (DDESB), IM community, and international community to establish a method for adopting and recognizing propane and other fuels as alternates for kerosene-based fuels in the liquid-fuel fire test. The design of the propane-fueled device will be simple in its construction to keep replacement costs low if damaged during the test. The test hardware will be easily replaced and modular by design to accommodate test articles of various dimensions. Test apparatus will not interfere with the test or change how the test is evaluated.

In the propane-fueled device, a series of nozzles will inject liquid propane at a measurable and controllable rate. The nozzle design for the liquid-fuel injection is innovative in its ability to properly atomize the propane at high flow rates with minimal pressure loss and to prevent the flame from blowing off. This nozzle design has been used previously to generate fine-scale turbulence in several combustion devices. The partially evaporated propane will impinge on metal slats where the jet will spread and entrain additional air for combustion. These metal slats, once optimized by determining the correct size, thickness, location, and material, will stabilize the flame and provide a location for flame attachment. With a stable flame, the test article can be situated at the location for maximum heat flux.

Once the propane fuel fire technology is built, ordnance items will be tested to determine the response of the item as a result of the propane fuel versus the kerosene fuel. A database will be developed that will document similarities or differences in the ordnance response between the two fuel types. Temperature, heat flux, overpressure, fragment size, and fragment distance will be documented for each test. Ordnance items with varying degrees of hazards (detonation to burn) will be explored. Successful completion of this project will involve the inclusion of propane into the standardized agreement (STANAG) and the production of a technical data package and publications. Additionally, a licensing agreement might be necessary to produce the technology so other services or companies may purchase and operate the technology.

Propane burns cleaner than kerosene-based fires, with 75% less soot. Propane is a gas at room temperature preventing soil and groundwater contamination, and propane is cheaper and easier to obtain than JP-8, AVCAT, and other kerosene-based fuels currently used in the liquid-fuel fire test. A propane burner system would be significantly more efficient than the pool fire configuration and would emit less carbon and almost no unburned hydrocarbons. Furthermore, because of the carbon-to-hydrogen ratio difference between propane and kerosene, propane produces 5% less carbon dioxide per mass of fuel. The propane burner system would use less than 10% of the fuel used in the liquid-kerosene fuel fire because the heat would be more efficiently used and the fuel burning could be stopped when the test item reacts. This leads to even further reduction in test environment emissions. (Anticipated Project Completion - 2016)