Performance analysis of aircraft fuel tank inerting system with turbocharger

The onboard inert gas generation system with turbocharger (OBIGGSTC) was proposed for better inerting performance of an aircraft fuel tank. The operating principle and method of the system were introduced, and the mathematical model of the major component was deduced. Then, the characteristic of the system was simulated based on the software AMESim. Compared with the traditional onboard inert gas generation system (OBIGGS), the proposed system has the potential advantages of reducing the weight and volume of the air separation system by decreasing the number of hollow fiber membrane modules (HFMMs) from a maximum number of eight to one at 0.3 MPa of the bleed air from the engine. When both inerting systems have a single HFMM configuration, the OBIGGSTC can substantially reduce the inerting time by 66.6% compared with the OBIGGS at 0.3 MPa of the bleed air. Due to the turbine applied, the mass flow rate of the bleed air of the inerting system with turbine is greater than the traditional system. The compensatory loss of the proposed system is less than the OBIGGS by a maximum of 57.39% when the bleed air pressure varies from 0.3 to 0.8 MPa with a range in flight time from 4 h to 10 h. By analyzing the two inerting system, the OBIGGSTC has better performance than the OBIGGS.

Numerical Study of the Influence of Ambient Pressure on the Inerting Effect of an Aircraft Fuel Tank Inerting System

The numerical study of the influence of the ambient pressure of the fuel tank on the inerting effect of an aircraft fuel tank inerting system was carried out. The mathematical model of ullage equilibrium oxygen concentration has been established using the differential time calculation method based on the mass conservation and ideal gas state equations. The variations of ullage oxygen concentration and dissolved oxygen concentration in the fuel with time under different working conditions have been obtained. The results have shown that the as the ambient pressure of the fuel tank became lower, the speed of the decreasing of oxygen concentration of the fuel tank ullge and the dissolved oxygen concentration of the fuel was slower.

Mill Steam Inerting System Review and Performance Validation

NFPA 85, Chapter 9.5.4 states “A pulverizer that is tripped under load shall be inerted and maintained under an inert atmosphere until confirmation that no burning or smoldering fuel exists in the pulverizer or the fuel is removed”. Pulverizer systems with the potential for a resident inventory of combustible material upon trip must be designed and equipped with an inerting system that is capable of maintaining an inert atmosphere to meet this requirement. Proper design of the inerting system and operating procedure, integrated with the mill operation during start-up, shut down and emergency trip is critical for safe mill operation. This paper presents a mill steam inerting system review and performance validation. The technology has been applied to ball tube mill systems at Hoosier Energy’s Merom Generating Station. A testing technique, used to validate performance of the steam inerting system at this generating plant, is described. It quantifies the compliance of the steam inerting system to meet NFPA requirements during start-up and shut down of the pulverizer. This type of operation is considered to be the most difficult for inerting as the primary air is flowing through the system. The developed testing approach can be applied to evaluate the performance of either existing or newly installed steam inerting systems. The validation technology, developed based on a ball tube mill system, can be readily applied on other types of mill systems, since the steam inerting principle is the same and inerting system requirements are similar, regardless of different mill types.