Fuel tank inerting system and method

Abstract

A fuel tank inerting system for an aircraft, the system comprises a catalytic heat exchanger comprising a first flow path and a second flow path for heat exchange with the first flow path. The system further comprises a first inlet arranged upstream of the first flow path of the catalytic heat exchanger for providing a mixture of fuel vapour and oxygen to the first flow path for sustaining a catalysed reaction, and a second inlet arranged upstream of the second flow path for providing a flow of fuel to the second flow path of the catalytic heat exchanger for exchanging heat with the first flow path.

Claims

1. A fuel tank inerting system for an aircraft, the system comprising: a catalytic heat exchanger comprising a first flow path and a second flow path for heat exchange with the first flow path; a first inlet arranged upstream of the first flow path of the catalytic heat exchanger for providing a mixture of fuel vapour and oxygen to the first flow path for sustaining a catalysed reaction; a second inlet arranged upstream of the second flow path for providing a flow of fuel to the second flow path of the catalytic heat exchanger for exchanging heat with the first flow path in order to control the temperature of the catalysed reaction therein.

2. A fuel tank inerting system as claimed in claim 1, comprising a fuel conditioner upstream of the second inlet for controlling the temperature of the fuel entering the second flow path of the catalytic heat exchanger.

3. A fuel tank inerting system as claimed in claim 2, comprising a fuel tank and wherein the fuel conditioner is arranged in use to receive fuel from the fuel tank.

4. A fuel tank inerting system as claimed in claim 1, comprising a temperature controlled valve upstream of the second inlet for controlling the rate of flow of fuel to the second inlet based on the temperature of the catalytic reaction or the heat exchanger in order to control the amount of heat exchange between the second flow path and the catalysed reaction and thereby control the temperature of the catalytic heat exchanger.

5. A fuel tank inerting system as claimed in claim 4, wherein the temperature controlled valve is arranged to divert fuel so as to bypass the catalytic heat exchanger thereby reducing the heat exchanged between the second flow path and the catalysed reaction.

6. A fuel tank inerting system as claimed in claim 1, wherein the system is arranged so that in use fuel exiting the second flow path is vaporised and supplied to the first inlet of catalytic heat exchanger.

7. A fuel tank inerting system as claimed in claim 1, arranged such that all fuel supplied to the first inlet of the catalytic heat exchanger in use will first have passed through the second flow path.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention will now be described by way of example only and with reference to the accompanying figures, in which:

(2) FIG. 1 shows a fuel inerting system comprising a catalytic heat exchanger; and

(3) FIG. 2 shows another fuel inerting system comprising a catalytic heat exchanger.

DETAILED DESCRIPTION

(4) FIG. 1 show a fuel inerting system 100 comprising a catalytic heat exchanger 110 comprising a first and second flow path. A first inlet 112 is arranged upstream of the first flow path, and a second inlet 114 is arranged upstream of the second flow path. Fuel vapour and oxygen flow along line 150 into the catalytic heat exchanger 110, through the first inlet 112 and into the first flow path

(5) A catalyst is disposed in the first flow path and during use the fuel and oxygen flowing into the first flow path undergo a catalysed reaction to create water and carbon dioxide. The water and carbon dioxide flows out of the first flow path via line 152, and is supplied to the ullage of a fuel tank. The catalyst has a temperature Tc.

(6) During use, fuel flows from line 160 though the second inlet 114 into the second flow path of the heat exchanger 110. In the second flow path the fuel is in heat exchange with the first flow path and thus affects the temperature of the catalyst and catalysed reaction. The fuel is heated in the second flow path and exits the heat exchanger through line 162. Fuel entering the second flow path is at a temperature T.sub.F2, and fuel exiting the second flow path is at a temperature T.sub.F3.

(7) A line 146 supplies oxygen rich air and combines with a flow of fuel vapour from another line 148 at junction 145 in order to supply a mixture of fuel and oxygen for the catalysed reaction. The ratio of flows of oxygen and fuel vapour at junction 145 may be controlled to provide the desired mixture to the heat exchanger.

(8) A fuel conditioner 180 is disposed upstream of the second inlet 114 and is arranged to provide fuel thereto via the line 160. The fuel conditioner is arranged to receive fuel from a line 164 and pass that fuel into heat exchange with oil flowing from line 182 to 184. Fuel entering the fuel conditioner is at a temperature T.sub.F1, and the fuel leaving the fuel conditioner is at a temperature T.sub.F2. Thus, temperature controlled fuel is provided to the second flow path of the catalytic heat exchanger via line 160 and second inlet 114.

(9) A temperature controlled valve 130 is disposed in line 160 and controls the flow of fuel therethrough, thereby controlling the flow of temperature controlled fuel to the second flow path and hence controlling the cooling of the catalytic reaction.

(10) The fuel inerting system of FIG. 1 may therefore be used to control the temperature of the catalytic reaction in the fuel inerting system to ensure a continuous supply inert atmosphere to the fuel tank.

(11) FIG. 2 shows a fuel inerting system similar to that of FIG. 1. The line 162 of fuel leaving the second flow path of the heat exchanger 110 is arranged to pass fuel to line 148 for supplying fuel vapour to the first inlet 112. Fuel leaving the second flow path during use is heated to a temperature T.sub.F3 and may be vapourised or partially vapourised. This fuel vapour may then be combined with oxygen rich air at junction 145 and supplied to the first inlet 112 for feeding the catalytic reaction. A heating element 134 is provided on line 162 and is used as necessary to convert liquid fuel to fuel vapour.

(12) A bypass line 136 is disposed to receive a bypass flow of fuel from the temperature controlled valve 130. The temperature controlled valve is controlled based upon the temperature of the catalyst and is configured to bypass fuel from the second flow path as necessary to achieve the desired temperature in the heat exchanger. Bypassed fuel is combined with the flow exiting the second flow path and at valve 132. The heating element 132 may vapourise the recombined fuel as required.

(13) The fuel inerting system 100 may therefore be used to control the temperature of the catalytic reaction. The heat necessary for forming the fuel vapour for the reaction is generated from the cooling of the reaction, thereby improving efficiency of the system.