Patent Description:
Accessories (such as an electric power generator, a fuel pump, and a lubricating oil pump), an accessory gear box, and the like are attached to an outer peripheral surface of a casing of an aircraft gas turbine engine (see <CIT>, for example). The accessories are mechanically driven by utilizing rotational power of a rotating shaft of the gas turbine engine. Specifically, the rotational power is taken out from the rotating shaft in the casing through a power transmission mechanism to an outside of the casing, is reduced in speed by the accessory gear box, and is transmitted to the accessories.

<CIT> discloses an aviation gas turbine comprising an outer casing structure, a core structure forming an annular flow passage and operating elements aligned therein and including an axial flow compressor, a combustor apparatus and a turbine connected to-the compressor by a common shaft. An afterburner section is associated with the casing structure providing a combustion chamber in which fuel may be burned in the gases exhausted from the turbine. <CIT> discloses an accessory gearbox assembly for an aircraft turbine engine having the features of the preamble of claim <NUM>.

For example, to suppress air resistance when the aircraft gas turbine engine is mounted on an airframe, a frontal projected area of the aircraft gas turbine engine needs to be reduced as much as possible, and the aircraft gas turbine engine needs to be reduced in size. However, according to current aircraft gas turbine engines, since the accessory disposed on the outer peripheral surface of the casing is large, the frontal projected area of the gas turbine engine becomes large.

An object of the present invention is to reduce the size of a gas turbine engine without decreasing output of the gas turbine engine.

This technical problem is solved by a gas turbine engine having the features of claim <NUM>. A gas turbine engine according to one aspect of the present invention is a gas turbine engine in which a compressor, a combustor, and a turbine are arranged so as to be lined up along a rotating shaft. The gas turbine engine includes: a casing that accommodates the compressor, the combustor, and the turbine; fuel pump units that are arranged at an outside of the casing, are lined up in a circumferential direction along an outer peripheral surface of the casing, and are connected in parallel; and a fuel supply pipe that collects fuel discharged from the fuel pump units and supplies the fuel to the combustor.

According to the above configuration, since the fuel is supplied to the combustor from the fuel pump units connected in parallel, the individual fuel pump units can be reduced in size. Then, since the fuel pump units that have been reduced in size are lined up along the outer peripheral surface of the casing, the amounts of projection of the fuel pump units outward in the radial direction from the casing can be made small, and the frontal projected area of the gas turbine engine can be reduced. Therefore, the gas turbine engine can be reduced in size without deteriorating engine performance.

The present invention can reduce the size of the gas turbine engine without reducing the output of the gas turbine engine.

Hereinafter, an embodiment will be described with reference to the drawings. In the following description, a "front side" denotes an upstream side in a direction in which air flows in an engine, and a "rear side" denotes a downstream side in the direction in which the air flows in the engine. To be specific, the "front side" denotes a side where a fan is disposed, in an axial direction of a rotating shaft of the engine, and the "rear side" denotes a side opposite to the side where the fan is disposed, in the axial direction of the rotating shaft of the engine. A "radial direction" denotes a direction orthogonal to a rotation axis of the rotating shaft of the engine. A "circumferential direction" denotes a direction around the rotation axis of the rotating shaft of the engine. Moreover, in the present description, an "aircraft" is a concept including an airplane, an unmanned flying object, and the like each of which flies by propulsive force generated by a gas turbine.

<FIG> is a sectional view of an aircraft gas turbine engine <NUM> according to the embodiment. <FIG> is a front view of the gas turbine engine <NUM> of <FIG> when viewed from the front. The present embodiment describes the aircraft gas turbine engine but is not especially limited. As shown in <FIG>, the aircraft gas turbine engine <NUM> includes a rotating shaft <NUM>, a fan <NUM>, a compressor <NUM>, a combustor <NUM>, a turbine <NUM>, and a casing <NUM>. The rotating shaft <NUM> extends in a front-rear direction of the gas turbine engine <NUM>. The fan <NUM> is connected to a front portion of the rotating shaft <NUM> and rotates together with the rotating shaft <NUM>. The compressor <NUM>, the combustor <NUM>, and the turbine <NUM> are lined up along the rotating shaft <NUM> in this order from the front side to the rear side. The casing <NUM> is a tubular object having an axis that coincides with a rotation axis of the rotating shaft <NUM>. The casing <NUM> accommodates the rotating shaft <NUM>, the fan <NUM>, the compressor <NUM>, the combustor <NUM>, and the turbine <NUM>.

Specifically, the gas turbine engine <NUM> is a two-shaft gas turbine engine. The compressor <NUM> includes a low-pressure compressor <NUM> and a high-pressure compressor <NUM> arranged behind the low-pressure compressor <NUM>. For example, the low-pressure compressor <NUM> is an axial flow compressor, and the high-pressure compressor <NUM> is a centrifugal compressor. However, the type of the low-pressure compressor <NUM> and the type of the high-pressure compressor <NUM> are not limited to these. The turbine <NUM> includes a low-pressure turbine <NUM> and a high-pressure turbine <NUM> arranged in front of the low-pressure turbine <NUM>. The rotating shaft <NUM> includes a low-pressure shaft <NUM> and a high-pressure shaft <NUM>. The low-pressure shaft <NUM> couples the low-pressure compressor <NUM> to the low-pressure turbine <NUM>, and the high-pressure shaft <NUM> couples the high-pressure compressor <NUM> to the high-pressure turbine <NUM>. The high-pressure shaft <NUM> is a tubular shaft including a hollow space therein. The low-pressure shaft <NUM> is inserted into the hollow space of the high-pressure shaft <NUM>. The low-pressure turbine <NUM> is coupled to the fan <NUM> through the low-pressure shaft <NUM>.

The casing <NUM> includes an inner shell <NUM> and an outer shell <NUM>. The inner shell <NUM> has a substantially cylindrical shape and accommodates the compressor <NUM>, the combustor <NUM>, and the turbine <NUM>. The outer shell <NUM> has a substantially cylindrical shape and is arranged concentrically with the inner shell <NUM> so as to be spaced apart from the inner shell <NUM> outward in the radial direction. A cylindrical bypass passage B exists between the inner shell <NUM> and the outer shell <NUM>. The air sucked by the fan <NUM> flows through the bypass passage B and is discharged to the rear side.

As shown in <FIG> and <FIG>, an outer peripheral surface of the casing <NUM> includes a first region 18a, a second region 18b, and a third region 18c. Electrically-operated accessories <NUM> are disposed in the first region 18a, and the second region 18b is located behind the first region 18a. The third region 18c connects the first region 18a and the second region 18b. The first region 18a is smaller in diameter than the second region 18b. The third region 18c is an inclined region that gradually increases in diameter toward the rear side. The first region 18a is located at a position corresponding to at least the low-pressure compressor <NUM> in the front-rear direction (rotation axis direction). The second region 18b is located at a position corresponding to at least the combustor <NUM> in the front-rear direction (rotation axis direction).

The electrically-operated accessories <NUM> are arranged along an outer peripheral surface of the first region 18a of the outer shell <NUM>. The electrically-operated accessories <NUM> are arranged at a radially inner side of an outer peripheral surface of the second region 18b when viewed from the front. The electrically-operated accessories <NUM> include fuel pump units <NUM>, a controller <NUM>, and the like. The fuel pump units <NUM> supply fuel of a fuel tank <NUM> (see <FIG>) to the combustor <NUM>. The controller <NUM> controls the fuel pump units <NUM> in accordance with predetermined sensor data and an external operation command.

The fuel pump units <NUM> are lined up in the circumferential direction along the outer peripheral surface of the first region 18a of the outer shell <NUM> and are connected to each other in parallel. The fuel discharged from the fuel pump units <NUM> flows through a fuel supply pipe <NUM> to be supplied to the combustor <NUM>. The fuel supply pipe <NUM> penetrates the third region 18c of the outer shell <NUM>. Each of the fuel pump units <NUM> has an elongated shape extending in one direction and has a substantially circular outer shape when viewed from a longitudinal direction of each fuel pump unit <NUM>. The fuel pump units <NUM> are disposed side by side such that the longitudinal direction of each fuel pump unit <NUM> is parallel to a rotation axis X of the rotating shaft <NUM>.

<FIG> is a block diagram showing the fuel pump units <NUM> and the like of the gas turbine engine <NUM> shown in <FIG>. As shown in <FIG>, each of the fuel pump units <NUM> (four fuel pump units <NUM>, for example) includes a displacement pump <NUM> and an electric motor <NUM>. The displacement pump <NUM> has a rotation axis Y extending along a longitudinal direction of the displacement pump <NUM>. The electric motor <NUM> is located adjacent to the displacement pump <NUM> in a direction along the rotation axis Y and drives the displacement pump <NUM>. A discharge port 31a of the displacement pump <NUM> is located at an opposite side of the electric motor <NUM> in the direction along the rotation axis Y in the displacement pump <NUM>. An inlet port 31b of the displacement pump <NUM> is located at the same side as the discharge port 31a in the displacement pump <NUM>.

The fuel supply pipe <NUM> includes a common pipe 23a and branch pipes 23b. The common pipe 23a extends toward the combustor <NUM>, and the branch pipes 23b extend from the common pipe 23a toward an upstream side. Upstream ends of the branch pipes 23b are connected to the discharge ports 31a of the displacement pumps <NUM>. To be specific, the fuel supply pipe <NUM> collects the fuel discharged from the discharge ports 31a of the displacement pumps <NUM> and guides the fuel to the combustor <NUM>. The fuel supply pipe <NUM> is arranged at an opposite side of the electric motors <NUM> across the displacement pumps <NUM>. A fuel suction pipe <NUM> connects the inlet ports 31b of the displacement pumps <NUM> to the fuel tank <NUM>. The fuel suction pipe <NUM> guides the fuel, stored in the fuel tank <NUM>, to the inlet ports 31b of the displacement pumps <NUM> by negative pressure generated in the displacement pumps <NUM>.

The controller <NUM> is connected to the electric motors <NUM> of the fuel pump units <NUM>. The controller <NUM> controls the electric motors <NUM> of the fuel pump units <NUM> in accordance with a detected value of a rotational frequency sensor <NUM> that detects a rotational frequency of the rotating shaft <NUM>, an operation command value (operator operation command, for example) from an outside, or the like. The rotational frequency sensor is not limited to a sensor that directly detects the rotation of the rotating shaft <NUM> and may detect the rotational frequency of the rotating shaft <NUM> from a voltage of an electric power generator (not shown).

According to the above configuration, since the fuel is supplied to the combustor <NUM> from the fuel pump units <NUM> connected in parallel, the individual fuel pump units <NUM> can be reduced in size. Then, since the fuel pump units <NUM> that have been reduced in size are lined up along the outer peripheral surface of the casing <NUM>, the amounts of projection of the fuel pump units <NUM> outward in the radial direction from the casing <NUM> can be made small. Therefore, the frontal projected area of the gas turbine engine <NUM> can be reduced.

Moreover, since the fuel pump units <NUM> are disposed side by side such that the longitudinal direction of each fuel pump unit <NUM> is parallel to the rotation axis X of the rotating shaft <NUM>, the fuel pump units <NUM> can be efficiently arranged in a circular-arc shape along the outer peripheral surface of the casing <NUM>. Therefore, the frontal projected area of the gas turbine engine <NUM> can be effectively reduced.

Moreover, since the fuel pumps arranged at an outside of the casing are electrically-operated pumps, a mechanism that transmits power from the gas turbine engine to the fuel pumps can be omitted, and the frontal projected area of the gas turbine engine can be reduced.

Moreover, since the fuel supply pipe <NUM> arranged at an opposite side of the electric motors <NUM> across the displacement pumps <NUM> is connected to the discharge ports 31a located in the displacement pumps <NUM> at an opposite side of the electric motors <NUM>, layout efficiency of the displacement pumps <NUM>, the electric motors <NUM>, and the fuel supply pipe <NUM> is high. Therefore, the entire gas turbine engine <NUM> can be effectively reduced in size.

Moreover, since the first region 18a in which the fuel pump units <NUM> are disposed is smaller in diameter than the second region 18b on the outer peripheral surface of the outer shell <NUM> of the casing <NUM>, the amounts of projection of the fuel pump units <NUM> outward in the radial direction from the casing <NUM> when viewed from the front are made small. Therefore, the frontal projected area of the gas turbine engine <NUM> can be reduced.

Next, control by the controller <NUM> will be described. The following will describe an example in which the number of fuel pump units <NUM> is four. However, this is merely one example, and the number of fuel pump units <NUM> may be a different number.

<FIG> is a graph for explaining a relation between an engine rotational frequency and the number of driven pumps. As shown in <FIG>, in accordance with the engine rotational frequency detected by the rotational frequency sensor <NUM>, the controller <NUM> changes the number of fuel pump units <NUM> to be driven among the four fuel pump units <NUM> (the number of fuel pump units <NUM> to be driven is hereinafter referred to as "the number of driven pumps"). The controller <NUM> compares the engine rotational frequency detected by the rotational frequency sensor <NUM> with thresholds RID, R<NUM>, R<NUM>, R<NUM>, R<NUM>, and RLM. Then, the controller <NUM> determines the number of fuel pump units <NUM> to be stopped (hereinafter referred to as "the number of non-driven pumps") in accordance with a magnitude relation between the engine rotational frequency and each of the thresholds RID, R<NUM>, R<NUM>, R<NUM>, R<NUM>, and RLM and then determines the number of driven pumps (= the total number of pumps - the number of non-driven pumps).

The threshold RID is an idling threshold corresponding to an idling rotational frequency. In case that the gas turbine engine <NUM> is started when the engine rotational frequency is less than the idling threshold RID, the controller stops at least one of the fuel pump units <NUM> and makes the other fuel pump units <NUM> discharge the fuel to make the gas turbine engine <NUM> perform an idling operation. Specifically, until the engine rotational frequency reaches the threshold RID from zero, the controller <NUM> sets the number of driven pumps to "one. " When the engine rotational frequency exceeds the threshold RID, the controller <NUM> increases the number of driven pumps to "two.

According to such control, at the start of the gas turbine engine <NUM>, i.e., when the amount of fuel required by the combustor <NUM> is small, at least one of the fuel pump units <NUM> is set to a stop state. With this, the other fuel pump units <NUM> can be stably operated at a relatively high rotational frequency, and the accuracy of the amount of fuel supplied to the combustor <NUM> can be made high.

The excessive rotation threshold RLM corresponds to an excessive rotational frequency as an abnormally high engine rotational frequency and is a threshold used to determine an engine abnormal operation. When the engine rotational frequency exceeds the excessive rotation threshold RLM, the controller <NUM> informs an external device (cockpit, for example) of an abnormality and sets the number of driven pumps to, for example, zero.

Each of the thresholds R<NUM>, R<NUM>, R<NUM>, and R<NUM> is a normal flight threshold that is larger than the idling threshold RID and smaller than the excessive rotation threshold RLM. When the engine rotational frequency exceeds the normal flight threshold R<NUM>, the controller <NUM> increases the number of driven pumps to "three. " When the engine rotational frequency exceeds the normal flight threshold R<NUM>, the controller <NUM> increases the number of driven pumps to "four. " As above, when the engine rotational frequency is such an engine rotational frequency that the amount of fuel required by the combustor <NUM> is large, the controller <NUM> reduces the number of stop pumps (i.e., increases the number of driven pumps).

According to such control, the amount of fuel supplied can be finely set from a low flow rate to a high flow rate. Therefore, the amount of fuel supplied can be controlled with a high degree of accuracy.

Moreover, when the engine rotational frequency falls below the normal flight threshold R<NUM>, the controller <NUM> reduces the number of driven pumps to "three. " When the engine rotational frequency falls below the normal flight threshold R<NUM>, the controller <NUM> reduces the number of driven pumps to "two. " To be specific, since the amount of fuel required by the combustor <NUM> is small during flight at high altitude, the controller <NUM> increases the number of stop pumps (i.e., reduces the number of driven pumps).

According to such control, when the amount of fuel required is small, such as when an aircraft flies at a high altitude, the controller <NUM> reduces the number of driven pumps and increases the amount of fuel discharged from each fuel pump unit <NUM>. With this, each driven fuel pump unit <NUM> can be stably operated at a relatively high rotational frequency, and the accuracy of the amount of fuel supplied to the combustor <NUM> can be made high.

A parameter used in threshold comparison by which the number of driven pumps is determined is not limited to the engine rotational frequency. For example, instead of the engine rotational frequency, an acceleration requested amount may be used as the parameter. <FIG> is a graph for explaining a relation between the acceleration requested amount and the number of driven pumps.

The acceleration requested amount denotes the degree of request of increasing the engine rotational frequency by an operation command value from an outside (for example, a command from a pilot or a command from a flight control device). For example, the acceleration requested amount may be a rotational frequency difference obtained by subtracting a current engine rotational frequency from a target engine rotational frequency determined based on the operation command value.

As shown in <FIG>, the controller <NUM> changes the number of driven pumps in accordance with the acceleration requested amount. The controller <NUM> compares the acceleration requested amount with thresholds A<NUM>, A<NUM>, A<NUM>, and A<NUM>. Then, the controller <NUM> determines the number of non-driven pumps in accordance with a magnitude relation between the acceleration requested amount and each of the thresholds A<NUM>, A<NUM>, A<NUM>, and A<NUM> and then determines the number of driven pumps. For example, the threshold A<NUM> is a negative value, and the thresholds A<NUM>, A<NUM>, and A<NUM> are positive values.

Until the acceleration requested amount reaches the threshold A<NUM> from a value close to zero, the controller <NUM> sets the number of driven pumps to "one. " When the acceleration requested amount exceeds the threshold A<NUM>, the controller <NUM> increases the number of driven pumps to "two. " When the acceleration requested amount exceeds the threshold A<NUM>, the controller <NUM> increases the number of driven pumps to "three. " When the acceleration requested amount exceeds the threshold A<NUM>, the controller <NUM> increases the number of driven pumps to "four. " In a process in which the acceleration requested amount decreases, the controller <NUM> performs an opposite operation to the above. Then, when the acceleration requested amount falls below the threshold A<NUM>, the number of driven pumps becomes zero.

Claim 1:
A gas turbine engine (<NUM>) in which a compressor (<NUM>), a combustor (<NUM>), and a turbine (<NUM>) are arranged so as to be lined up along a rotating shaft (<NUM>),
the gas turbine engine (<NUM>) comprising:
a casing (<NUM>) that accommodates the compressor (<NUM>), the combustor (<NUM>), and the turbine (<NUM>);
fuel pump units (<NUM>) that are arranged at an outside of the casing (<NUM>), and are connected in parallel; and
a fuel supply pipe (<NUM>) that collects fuel discharged from the fuel pump units (<NUM>) and supplies the fuel to the combustor (<NUM>), wherein:
the fuel supply pipe (<NUM>) includes
a common pipe (23a) extending toward the combustor (<NUM>) and
branch pipes (23b) extending from the common pipe (23a) toward an upstream side;
the branch pipes (23b) are connected to discharge ports (31a) of the fuel pump units (<NUM>),
characterized in that:
the fuel pump units (<NUM>) are lined up in a circumferential direction along an outer peripheral surface of the casing (<NUM>);
each of the fuel pump units (<NUM>) has an elongated shape extending in one direction;
the fuel pump units (<NUM>) are side-by-side such that a longitudinal direction of each fuel pump unit (<NUM>) is parallel to a rotation axis (X) of the rotating shaft (<NUM>);
each of the fuel pump units (<NUM>) includes
a displacement pump (<NUM>) including a rotation axis (Y) extending along the longitudinal direction and
an electric motor (<NUM>) that is located adjacent to the displacement pump (<NUM>) in a direction along the rotation axis (Y) of the displacement pump (<NUM>) and drives the displacement pump (<NUM>);
the discharge port (31a) of the displacement pump (<NUM>) is located at an opposite side of the electric motor (<NUM>) in the direction along the rotation axis (Y) of the displacement pump (<NUM>);
the fuel supply pipe (<NUM>) is arranged at an opposite side of the electric motors (<NUM>) across the displacement pumps (<NUM>) of the fuel pump units (<NUM>).