Fuel Flow-Through

EFC anodes in the compartment eonfiguration and operation are typically limited by diffusion of fuel (substrate) to enzymes in the bulk of the porous tortuous electrode material. Increased fuel coneentration might help, but maximal substrate concentration is relatively low as it is limited by substrate inhibition, increased fuel viscosity, and accumulation of highly concentrated waste products in the fuel that all hinder the charge transfer reaction. 

There are two viable jproaches to inducing fuel flow through an EFC. One is to integrate an extremely low power eonsumption pump. The eonsumed power for pumping must be signifieantly low with respect to the total generated power by the entire EFC system. The other is to use apassive pumping system that does not eonsume eleetric power. 

In a eireular profile tubing of diameter D (m) and length / (m), pressure drop of vp (Pa) is required to maintain a laminar flow of a fluid with dynamie viseosity p (Pa s) and veloeity u (m s ). In this ease, the pressure drop is dominated by the fluid flow friction in the tubing and can be simplified by Equation 16.3 [18]  

Then the pumping power W (W) can be calculated for flow rate / (m s ) (Equation 16.4)  

The pressure drop in the fuel line is only one part of the entire fuel circuit, but as is explained later in this chapter, the fuel line diameter is specifically designed to be very small and thus this part of the circuit might become dominating. The pressure drop through the bulk of the electrodes strongly depends on porosity and tortuosity of the material as well as on the electrode geometry and the design of the flow path. 

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The fuel filters were then partially blocked by rust and corrosion products carried by the water. Below-freezing temperatures possibly initiated the formation of ice within fuel filters and in fuel lines containing water. The combination of ice and corrosion products blocked fuel flow through vehicle fuel lines and filters. Gasoline flow to the engine was halted and engine shutdown followed. 

As the fuel passes through various tank and line filters, rouge can be trapped by the filter media. Filter plugging and halting of fuel flow through the filter can result. 

The use of these empirical procedures is being superseded by the more precise kinematic viscosity method (ASTM D-445, IP 71), in which a fixed volume of fuel flows through the capillary of a calibrated glass capillary viscometer under an accurately reproducible head and at a closely controlled temperature. The result is obtained from the product of the time taken for the fuel to flow between two etched marks on the capillary tube and the calibration factor of the viscometer and is reported in centistokes. Because the viscosity decreases with increasing temperature the temperature of test must also be reported if the viscosity value is to have any significance. For distillate fuel oils the usual test temperature is 38°C (100°F). 

If fuel flow through the arrestor is not safely stopped and the condition allowing the flame to burn at the arrestor is not corrected, the flame will continue to burn at the face of the heat-absorbing surface in the arrestor, eventually raising the temperature of the flame arrestor medium and its enclosure such that it might ignite the flammable mixture on the downstream side of the arrestor. 

The electronically conductive network in the electrode functions as an internal current collector and can be formed from conductive nanoparticles integrated within a porous matrix or from a continuous rigid backbone. One example is the biopolymer chitosan fabricated with a conductive additive of carbon nanotubes [2,3,8]. Ideally, the electronically conductive network will also provide mechanical stability to the electrode and support the structure against vibrations, fuel flow-through pressures, and other mechanical shocks. The electronically conductive network is essentially an internal current corrector within the anode and, as such, must be electronically wired to the external current collector of the anode compartment with minimal contact and ohmic resistance. The electrode materials described are typically delicate and mechanically soft and must be carefully handled to maintain their open high-porosity structure. 

Fuel Flow-Through Operation and Fuel Waste Management... 

The fuel flow-through system should be activated only in the event of EEC power generation, or in regular intervals to refresh the fuel in the system and potentially perform self-system checks such as ceU voltage at the pump electric loading. 

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