QUANTIFICATION OF ELECTROSTATIC CHARGE GENERATION AND RELAXATION IN COMPOSITE AIRCRAFT FUEL TANKS

摘要

A study of charge generation and charge relaxation, due to static electrification, is proposed when a liquid, charged in an upstream circuit, is injected into a composite tank. Firstly, the relationship between the generated charge density q_g in the tank and the injected upstream charge density q_i is analyzed; when the double layer is fully developed, the sum of both charges densities is a constant which depends only on intrinsic parameters that describe the electrification in the tank. The case of a strong injection (q_i q_g) and its impact on the charge generation in the tank, are discussed. A conservative criterion for a risk assessment is proposed. Secondly, the charge relaxation is analyzed for various tank walls conductivities. The dynamics are given for the charge migration through the liquid bulk to the tank walls and the liquid surface from one side, and for the charge relaxation through the tank walls from the other side. Dynamics of complete charge relaxation to ground through the walls was estimated in the case of a composite tank with dissipative walls. At last, the impact on charge relaxation of conducting grounded parts through dielectric walls is discussed and quantified.