Patent Description:
Attritable aircraft can include, for example, Unpiloted (or Unmanned) Aerial Vehicles (UAVs) and expendable turbojet systems for guided munitions, missiles, and decoys. Attritable aircraft are generally designed as a limited lifetime vehicle, which can be as short as a single use or single mission vehicle. As such, many components and features common in traditional piloted aircraft are unnecessary, such as, a fuel dispensing system within a traditional aircraft engine, which can have more than <NUM> individual parts, each requiring assembly. Even in the realm of attritable engines, conventional fuel rails can have more than <NUM> individual parts, which need to be brazed together, which is expensive and time consuming.

Furthermore, conventional fluid dispensing devices may be heavy, are difficult to package, and because of the many operating parts may be expensive to maintain and/or repair. There exist needs in various industries to reduce the number of manufactured parts for fluid dispensing devices, thereby providing more robust and simpler designs, which requires less maintenance, reduces manufacturing time and costs, reduces weight, and simplifies packaging.

A prior art additively manufactured attritable engine having integrated fuel injectors is disclosed in <CIT>, which is prior art under Art <NUM>(<NUM>) EPC only.

A prior art additively manufactured micro turbojet engine is disclosed in <CIT>.

A prior art fuel injection system for a turbine combustor is disclosed in <CIT>.

A prior art fluid injection system is disclosed in <CIT>.

In accordance with a first aspect of the disclosure, there is provided an additively manufactured attritable engine in accordance with claim <NUM>.

In accordance with a second aspect of the disclosure, there is provided a method of testing a fluid dispensing system in an attritable engine in accordance with claim <NUM>.

An attritable engine with an integrally built fuel dispensing system simplifies manufacturing. Even so, an attritable engine can leverage additive manufacturing techniques to improve various aspects of the limited-life engine. For example, additive manufacturing allows the assembly details to be unitized and, simultaneously permits integration of many complex performance-enhancing features. The additively manufactured engine reduces the time to delivery to the customer and lowers the overall production costs of the unit.

However, an integrally built fuel system in an attritable engine limits accessibility for inspection and testing post-manufacture. Typically, gas turbine engines have more than one fuel injector per engine, which complicates determining whether one or more individual injectors are clogged or otherwise faulty using routine techniques. For example, although CT scanning (Computed Tomography) can be used to inspect an attritable engine, CT scanning is very time consuming and costly. As such, CT scanning is not amenable to inspection of every manufactured attritable engine. An attritable engine with fuel feed passages and a method to individually isolate and flow test each injector using the fuel feed passages are disclosed herein.

<FIG> will be discussed together. <FIG> is a side view of an attritable engine. <FIG> shows attritable engine <NUM> including forward engine casing <NUM>, rearward engine casing <NUM>, exhaust casing <NUM>, fluid distribution system <NUM>, fuel inlet <NUM>, fuel manifold <NUM>, fuel line <NUM>, fuel feed passages <NUM>, and axis of rotation X. <FIG> is a cross-sectional view of attritable engine <NUM> including forward engine casing <NUM>, rearward engine casing <NUM>, exhaust casing <NUM>, fluid distribution system <NUM>, fuel inlet <NUM>, fuel line <NUM>, combustor <NUM>, combustor liner <NUM>, air channel <NUM>, rotor <NUM>, bearings <NUM> and <NUM>, rotor system <NUM>, compressor blades <NUM>, air inlet <NUM>, turbine blades <NUM>, and axis of rotation X.

Forward engine casing <NUM> encases a compressor section of attritable engine <NUM> and is connected to rearward engine casing <NUM>, which encases combustion and turbine sections of attritable engine <NUM>. Exhaust casing <NUM> is connected to rearward engine casing <NUM>, opposing forward engine casing <NUM>.

Rearward engine casing <NUM> has fluid distribution system <NUM> including fuel inlet <NUM>, fuel manifold <NUM>, fuel line <NUM>, and fuel feed passage <NUM>. Although only two feed passages <NUM> are shown, four other feed passages are present and circumferentially related around axis of rotation X and obscured in <FIG> by rearward engine casing <NUM>.

Fuel inlet <NUM> is coupled to a fuel source such as a fuel tank. Fuel inlet <NUM> is configured to deliver fuel to fuel manifold <NUM>, which is connected to and delivers fuel to fuel line <NUM>. The fuel exits fuel line <NUM> and enters fuel feed passage <NUM>. The fuel exits fuel feed passage <NUM> and enters injector <NUM>, which delivers the fuel to combustor <NUM> defined by combustor wall <NUM>. The fuel can be aerated by air from air channel <NUM> prior to delivery into combustor <NUM>, aerated in combustor <NUM>, or aerated both prior to and during delivery to combustor <NUM>.

Combusted fuel exits combustor <NUM> and turns rotor <NUM>, which is received in bearings <NUM> and <NUM>. Rotor system <NUM> includes compressor blades <NUM>, air inlet <NUM>, and turbine blades <NUM>. Air enters air inlet <NUM> and is compressed by compressor blades <NUM>. Compressed air enters combustor <NUM> where the compressed air is combusted with fuel from injector <NUM>. The combusted air from combustor <NUM> enters and turns turbine blades <NUM>, which are attached to rotor <NUM>, circumferentially around rotational axis X, generating power. The air exits out of exhaust casing <NUM>.

<FIG> and <FIG> will be discussed together. <FIG> is a perspective view of the attritable engine with a fuel feed passage. <FIG> shows attritable engine <NUM> including rearward engine casing <NUM>, fluid dispensing system <NUM>, fuel inlet <NUM>, fuel manifold <NUM>, fuel line <NUM>, and fuel feed passage <NUM>. <FIG> is a sectional region view of an injector with a fuel feed passage shown in <FIG>. <FIG> shows attritable engine <NUM> including rearward engine casing <NUM>, fluid dispensing system <NUM>, fuel line <NUM>, fuel feed passage <NUM>, injector <NUM>, combustor <NUM>, combustor wall <NUM>, air channel <NUM>, exterior surface <NUM>, interior surface <NUM>, fuel line wall <NUM>, injector wall <NUM>, injector inlet <NUM>, injector outlet <NUM>, and fuel feed passage wall <NUM>.

Attritable engine <NUM> includes rearward engine casing <NUM>, which has exterior surface <NUM> and interior surface <NUM>. Attritable engine <NUM> also includes fluid dispensing system <NUM> manufactured integral and conformal with rearward engine casing <NUM>. Fluid dispensing system <NUM> includes fuel inlet <NUM>, fuel manifold <NUM>, fuel line <NUM>, injector <NUM>, injector inlet <NUM>, injector outlet <NUM>, and fuel feed passage <NUM>. Rearward engine casing <NUM> includes a plurality of cavities. Fuel line <NUM> is a cavity within rearward engine casing <NUM> defined by fuel line wall <NUM>. Injector <NUM> is a cavity within rearward engine casing <NUM> and is defined by injector wall <NUM>. Fuel feed passage <NUM> is a cavity within rearward engine casing <NUM> and is defined by fuel feed passage wall <NUM>.

Rearward engine casing <NUM> circumferentially surrounds rotor <NUM> along its rotational axis X. Injector <NUM> is attached to fuel feed passage <NUM> at injector inlet <NUM>. Injector <NUM> extends at an acute angle from rearward engine casing <NUM> in an axial direction toward rotor <NUM>'s rotational axis X and away from exterior surface <NUM>. Injector <NUM> is integral and conformal with rearward engine casing <NUM> and extends through and is defined by rearward engine casing <NUM>.

Fluid distribution system <NUM> operates by fuel entering fuel inlet <NUM>, which is configured to receive fuel from a fuel source such as a fuel tank and deliver fuel to fuel manifold <NUM>. The fuel enters fuel line <NUM> from fuel manifold <NUM> and is delivered to fuel feed passage <NUM>, which delivers the fuel to injector <NUM> at injector inlet <NUM>. The fuel can be partially aerated in fuel line <NUM>. For example, fuel line <NUM> can have numerous holes where air from air channel <NUM> may enter and mix with the fuel. The fuel travels through injector <NUM> and exits at injector outlet <NUM> where the fuel is dispensed into combustor <NUM>. Injector outlet <NUM> of injector <NUM> is configured to deliver fuel, which can be aerated, to combustor <NUM>. The fuel entering combustor <NUM> can be further aerated and is combusted.

Fuel feed passages <NUM> are built integral and conformal with rearward engine casing <NUM>. In one embodiment, fuel feed passages <NUM> extend laterally with exterior surface <NUM> and are substantially parallel with exterior surface <NUM>. Alternatively, fuel feed passages <NUM> can extend at an acute angle from exterior surface <NUM> toward axis of rotation X of rotor <NUM>.

Fuel feed passages <NUM> are in thermal communication with exterior surface <NUM>. Fuel feed passages <NUM> are close enough to exterior surface <NUM> to be in thermal communication with exterior surface <NUM>, but not close enough to reduce the structural integrity of rearward engine casing <NUM>, injector <NUM>, or fuel feed passages <NUM> compared to an attritable engine without any fuel feed passages. In other words, fuel feed passages <NUM> have sufficient structural integrity to withstand the pressures and temperatures in an attritable engine under load.

An attritable engine can have more than one injector per engine. After the attritable engine has been manufactured, the injectors can be flow tested to ensure the stringent flow requirements are met to operate the gas turbine engine under load. However, it is desirable to flow test each injector one at a time and, as such, desirable to temporarily block the flow of the other injectors present in the attitable engine.

The fuel feed passage system of attritable engine <NUM> temporarily blocks the flow to the other injectors in the attritable engine by freezing a flow test fluid in each of the other fuel feed passages. A flow test fluid is injected into fuel line <NUM> and enters fuel feed passage <NUM>. Cooling is then applied to exterior surface <NUM> adjacent to fuel feed passage <NUM>. The applied cooling can be in the form of a solid, liquid, or a gas such as, for example, ice, water, salt water, a water-alcohol mixture, carbon dioxide gas, or nitrogen gas. As cooling is applied heat is absorbed from rearward engine casing <NUM>, which in turn absorbs heat from a flow test fluid present in fuel feed passage <NUM>. The applied cooling is cold enough to induce a phase change in the testing fluid to a solid. The solid testing fluid prevents any further flow through injector <NUM>.

Cooling is applied to fuel feed passages <NUM> for all the injectors of attritable engine <NUM>, except for one. For example, an attritable engine with an N number of injectors would have (N-<NUM>) fuel feed passages cooled, which prevents flow through the corresponding (N-<NUM>) injectors. That leaves one injector available for flow testing. The flow rate can be measured of a test fluid such as, for example, water or fuel. The injector under test can be blocked by cooling exterior surface <NUM> adjacent to fuel feed passage <NUM> in order to induce a phase change in the flow test fluid present in the fuel feed passage. Next, one of the (N-<NUM>) injectors can be unblocked by allowing the flow test fluid to undergo another phase change. Either heating can be applied to the exterior surface <NUM> adjacent to fuel feed passage <NUM> or ambient conditions can be allowed to warm up the flow test fluid by simply removing the cooling from exterior surface <NUM> adjacent to fuel feed passage <NUM>. Subsequently, the one of the (N-<NUM>) injectors can be flow tested. This process can be repeated until all N injectors have been fluidically isolated and flow tested.

Notably, water can be used both as the cooling fluid and the flow test fluid. For example, fast moving water, a suitable mixture of salt water, or a suitable mixture of water and alcohol do not freeze even below <NUM>° C (<NUM>° F) and, as such, can induce a phase change of water in the fuel feed passage.

Measured flow rates within tolerance requirements indicate a successful manufacture, whereas, measured flow rates outside of tolerance requirements may indicate the injector was not manufactured correctly. For example, a metallic powder used during an additive manufacturing process may not be sintered completely or properly removed after one or more additive manufacturing building steps and, as such, obstruct the flow path through the injector.

Alternatively, a gas, such as Argon, can be used as the flow test fluid. A gas passing through a restricted opening, such as an injector, induces an acoustic vibration. The pitch of the acoustic vibration changes as the restriction is enlarged or narrowed. Measuring the pitch of the acoustic vibration may indicate a successful build, an improper build, or a plugged injector.

Attritable engine <NUM> is built using additive manufacturing techniques and has fluid dispensing system <NUM> manufactured integral with the engine case wall. Specifically, the engine case wall is built up in a layer-by-layer process in an axial direction toward the central rotor's rotational axis and has a plurality of cavities. The additively manufactured engine case wall results in a geometry for the injector that meets the stringent tolerance requirements of the attritable engine and includes cooling holes to allow sequential flow testing of individual injectors within the attritable engine.

Attritable engine <NUM> can be additively manufactured using any metal or alloy that can tolerate the high temperature and pressure environment of an aircraft combustion engine for the expected useable life of the vehicle, such as, for example, Inconel® <NUM> or other nickel alloys or alloys of nickel, chromium, and iron. However, guided munitions, missiles, and decoys are designed as single use vehicles and can have a maximum useable life of <NUM> hours. Heat protection that extends the useable life of the vehicle beyond <NUM> hours can unnecessarily add labor and expense to the manufacturing of such an engine. On the other hand, some UAVs can be designed to perform multiple missions and more heat protection may be desirable. A specific metal or alloy with or without additional treatments to provide heat protection can be chosen with such considerations in mind. For example, a thermal barrier layer or coating can be applied to the metal or alloy to extend the useful life of the attritable engine.

Providing fuel feed passages adjacent to and in thermal communication with the exterior surface of an attritable engine allows each injector to be fluidically isolated and flow tested after the attritable engine has been manufactured. This testing process is much faster and less expensive than conventional testing techniques such as CT scanning.

Claim 1:
An additively manufactured attritable engine (<NUM>) comprising:
a compressor section;
a combustion section;
a turbine section; and
an engine case wall (<NUM>, <NUM>) surrounding the compressor section, the combustion section, and the turbine section, characterized by the engine case wall (<NUM>, <NUM>) comprising:
a first cavity, embedded within the engine case wall (<NUM>, <NUM>), defining an injector (<NUM>), wherein the injector (<NUM>) is in fluid communication with the combustion section;
a second cavity, embedded within the engine case wall (<NUM>, <NUM>), defining a fuel feed passage (<NUM>), wherein the fuel feed passage (<NUM>) is adjacent to and in thermal communication with an exterior surface (<NUM>) of the engine case wall (<NUM>, <NUM>); and
a third cavity, embedded within the engine case wall (<NUM>, <NUM>), defining a fuel line (<NUM>), wherein the fuel line (<NUM>) is connected to and in fluid communication with the fuel feed passage (<NUM>), a fuel inlet (<NUM>) is configured to deliver fuel to a fuel manifold (<NUM>), the fuel manifold (<NUM>) is configured to deliver the fuel to the fuel line (<NUM>), and the fuel line (<NUM>) is configured to deliver the fuel to the fuel feed passage (<NUM>), and the fuel feed passage (<NUM>) is configured to deliver the fuel to the injector (<NUM>).