Research Papers

Evaluating the Potential for Gasoline Geysering From Small Engine Fuel Tanks

[+] Author and Article Information
Todd M. Hetrick

Exponent, Inc.,
4580 Weaver Parkway,
Suite 100,
Warrenville, IL 60555
e-mail: thetrick@exponent.com

Suzanne A. Smyth

Exponent, Inc.,
4580 Weaver Parkway,
Suite 100,
Warrenville, IL 60555
e-mail: ssmyth@exponent.com

Russell A. Ogle

Exponent, Inc.,
4580 Weaver Parkway,
Suite 100,
Warrenville, IL 60555
e-mail: rogle@exponent.com

Juan C. Ramirez

Exponent, Inc.,
4580 Weaver Parkway,
Suite 100,
Warrenville, IL 60555
e-mail: jramirez@exponent.com

1Present address: Rimkus Consulting Group, Inc., 7501 S. Quincy Street, Suite 160, Willowbrook, IL 60527.

Manuscript received March 5, 2015; final manuscript received September 1, 2017; published online October 3, 2017. Assoc. Editor: Chimba Mkandawire.

ASME J. Risk Uncertainty Part B 4(2), 021001 (Oct 03, 2017) (4 pages) Paper No: RISK-15-1046; doi: 10.1115/1.4037866 History: Received March 05, 2015; Revised September 01, 2017

This paper explores an infrequently encountered hazard associated with liquid fuel tanks on gasoline-powered equipment using unvented fuel tanks. Depending on the location of fuel reserve tanks, waste heat from the engine or other vehicle systems can warm the fuel during operation. In the event that the fuel tank is not vented and if the fuel is sufficiently heated, the liquid fuel may become superheated and pose a splash hazard if the fuel cap is suddenly removed. Accident reports often describe the ejection of liquid as a geyser. This geyser is a transient, two-phase flow of flashing liquid. This could create a fire hazard and result in splashing flammable liquid onto any bystanders. Many existing fuel tank systems are vented to ambient through a vented tank cap. It has been empirically determined that the hazard can be prevented by limiting fuel tank gauge pressure to 10 kPa (1.5 psi). However, if the cap does not vent at an adequate rate, pressure in the tank can rise and the fuel can become superheated. This phenomenon is explored here to facilitate a better understanding of how the hazard is created. The nature of the hazard is explained using thermodynamic concepts. The differences in behavior between a closed system and an open system are discussed and illustrated through experimental results obtained from two sources: experiments with externally heated fuel containers and operation of a gasoline-powered riding lawn mower. The role of the vented fuel cap in preventing the geyser phenomenon is demonstrated.

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Grahic Jump Location
Fig. 1

Fraction of liquid flashed. Hexane liquid–vapor in thermodynamic equilibrium in a pressurized tank.

Grahic Jump Location
Fig. 2

Schematic of a fuel system

Grahic Jump Location
Fig. 3

Four examples of fuel tanks from a:(a) string trimmer, (b) chainsaw, (c) push mower, and (d) riding mower [1518]

Grahic Jump Location
Fig. 4

Temperature (solid) and pressure (dotted) inside the fuel tank over time for a riding lawn mower at 100% throttle and 100% load running in full sun with a vented cap

Grahic Jump Location
Fig. 5

Temperature (solid) and pressure (dotted) inside the fuel tank over time for a riding lawn mower at 100% throttle and 100% load running in full sun with an unvented cap

Grahic Jump Location
Fig. 6

Temperature (solid) and pressure (dotted) inside the fuel tank over time for a riding lawn mower sitting in full sun, while not operating, with an unvented cap




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