Patent Description:
Variable-area fuel injectors have been used in many applications relating to air-breathing propulsion systems, including in ramjets, scramjets, and in gas turbine engines such as those used in aviation. Ramjets, scramjets, and gas turbine engines typically include a section for compressing inlet air, a combustion section for combusting the compressed air with fuel, and an expansion section where the energy from the hot gas produced by combustion of the fuel is converted into mechanical energy. The exhaust gas from the expansion section may be used to achieve thrust or as a source of heat and energy.

Generally, one or more types of fuel injectors are used in the combustion section for spraying a flow of fuel droplets or atomized fuel into the compressed air to facilitate combustion. In some applications of air-breathing propulsion systems including ramjets, scramjets, and particularly in gas turbine engines, which must run at variable speeds, variable-area fuel injectors have been used because they provide an inexpensive method to inject fuel into a combustor, while also metering the fuel flow without the need for an additional metering valve.

Typically, the fuel flow rate is controlled by the combination of a spring, the fuel pressure, and an annular area, which is increasingly enlarged as the fuel pressure is increased. This is unlike the operation of pressure-swirl atomizers where the pressure-flow characteristics are static, and are determined solely by the fixed injector geometry and the variable injection pressure. Generally, variable-area fuel injectors provide good atomization over a much wider range of flow rates than do most pressure-swirl atomizers. Additionally, with variable-area fuel injectors, the fuel pressure drop is taken at the fuel injection location, thus providing better atomization than typical pressure-swirl and plain-orifice atomizers.

However, throughout its operational pressure range, most variable-area fuel injectors do not provide optimal spray circumferential uniformity, or patternation. Typically, these conventional variable-area fuel injectors have slots or holes used to feed fuel to the fuel manifold which is upstream of the exit area. In general, this configuration does not prevent the formation of wakes in the fuel flow downstream of these slots or holes. Optimal patternation is desirable in order to avoid non-uniform fuel distribution, which can cause hot spots in air-breathing engines resulting in thermal distress and failure of the engine itself. Good patternation also helps avoid regions of high fuel concentration (i.e., rich regions) in combustors, which reduces fuel efficiency and leads to poor emissions quality.

In applications not related to air-breathing engines, poor patternation can also lead to failure of the device. One such application is the automotive engine exhaust treatment process in which fuel is used to increase the temperature of the engine exhaust. By increasing the temperature of the exhaust, downstream post-engine exhaust treatment devices, such as dosers and diesel particulate filters can operate more effectively. However, poor patternation can cause hot-spots in the matrix of both the doser and the diesel particulate filter, thus reducing the life of the matrix. Fuel injectors may also be used in missile applications, which typically requires higher fuel turndown ratio to meet flight envelope. The fuel turndown ratio is defined as the ratio of the maximum fuel input rate to the minimum fuel input rate.

A fuel injector apparatus is disclosed in <CIT> entitled, "Piloted Variable Area Fuel Injector, and in <CIT> entitled, "Variable-Area Fuel Injector With Improved Circumferential Spray Uniformity," while <CIT> discloses a Pre-Swirl Pressure Atomizing Tip for a nozzle of a fuel injector, and <CIT> discloses a Hybrid Variable Area Fuel Injector with Thermal Protection.

<CIT> describes a liquid fuel burner nozzle comprises a main swirl chamber and a pilot swirl chamber each adjacent and open to the nozzle outlet, and a normally closed valve, e.g. a ball valve controlling the flow of fuel from the nozzle inlet to the main swirl chamber, the valve being arranged to open when the fuel pressure reaches a predetermined value.

<CIT> describes a liquid fuel nozzle in which a main injection hole for jetting main fuel is of a structure having a straight portion which is in the form of an annular flow path extending parallel to an axis of the liquid fuel nozzle, the annular flow path having a flow path cross section not changed along the straight portion.

<CIT> describes a fuel injector having a body with a bore, which defines a fuel manifold. The injector also has a variable-area injector arrangement having a pintle with a conical head and a pintle spring connected to the body. The pintle spring urges a tip of the pintle to seal against an exit orifice of the body, such that application of pressurized fuel within the body causes the pintle to move. Above some threshold pressure, the pressurized fuel causes the conical head to move out of contact with the exit orifice of the body.

<CIT> describes a fuel injector for a gas turbine engine includes a monolithic nozzle body that defines within its interior one or more fuel circuits. Each fuel circuit includes an inlet, an outlet orifice, a main passage fluidly coupling the inlet with the outlet orifice, and a branch passage connected to the main passage. The branch passage connects to the main passage downstream of the inlet and upstream of the outlet orifice to form an effective metering flow area that is smaller than the flow area of the outlet orifice.

In one aspect, embodiments of the invention provide a multiphase fuel injector that includes an injector body having a fuel inlet at a first end of the injector body and a fuel outlet at a second end of the injector body opposite the first end. A primary circuit is disposed proximate the fuel inlet and extends into a central portion of the injector body. The primary circuit is configured to receive a first flow of pressurized fuel from the fuel inlet and discharge the fuel into a spin chamber located in the injector body downstream from the fuel inlet. The primary circuit is configured to impart a swirling action to the first flow of pressurized fuel. A secondary circuit is located in the injector body radially outward from the primary circuit. The secondary circuit is configured to receive a second flow of pressurized fuel from the fuel inlet and discharge the fuel into the fuel outlet. The secondary circuit is configured to impart a swirling action to the second flow of pressurized fuel. The primary circuit includes a flow plate attached to a biasing spring, wherein the flow plate blocks fuel from flowing into the secondary circuit when the biasing spring is fully extended, and allows fuel to flow into the secondary circuit when the biasing spring is compressed.

In a more particular embodiment, the biasing spring is configured such that the primary circuit facilitates ignition of fuel at a flow rate of less than <NUM>/hr (<NUM> pounds per hour (PPH)). In another embodiment, the biasing spring is configured such that the primary and secondary circuits together facilitate a maximum fuel flow rate greater than <NUM>/hr (<NUM>,<NUM> pounds per hour (PPH)).

In certain embodiments, the primary circuit includes one or more helical primary openings formed in the injector body. The one or more helical primary openings are configured to direct the first flow of pressurized fuel in the primary circuit to the spin chamber and to impart a swirling motion to the first flow of pressurized fuel. The secondary circuit may include one or more helical secondary openings formed in the injector body. The one or more helical secondary openings are configured to direct the second flow of pressurized fuel to the fuel outlet and to impart a swirling motion to the second flow of pressurized fuel. In some embodiments, the secondary circuit includes one or more helical secondary openings are located radially outward from the one or more helical primary openings. In an alternate embodiment, the primary circuit includes a fuel swirler inserted into an opening in the injector body, the fuel swirler having one or more helical grooves in an exterior surface of the fuel swirler, the fuel swirler being configured to impart a swirling motion to fuel flowing through the primary circuit.

In another aspect, embodiments of the invention provide a method of making a multiphase fuel injector. The method includes the step of using additive manufacturing to construct an injector body, wherein using additive manufacturing to construct the injector body comprises constructing the injector body to include a fuel inlet at a first end of the injector body and a fuel outlet at a second end of the injector body opposite the first end. The injector body further includes a primary circuit disposed within the injector body proximate the fuel inlet, and extending into a central portion of the injector body. The primary circuit has one or more helical primary openings formed in the injector body. The one or more helical primary openings are configured to direct a first flow of pressurized fuel to a spin chamber and to impart a swirling motion to the first flow of pressurized fuel. The injector body also includes a secondary circuit located within the injector body and positioned radially outward from the primary circuit. The secondary circuit has one or more helical secondary openings formed in the injector body. The one or more helical secondary openings are configured to direct a second flow of pressurized fuel toward a fuel outlet and to impart a swirling action to the second flow of pressurized fuel. The method also includes inserting a flow plate and spring into an opening within the injector. The flow plate abuts the biasing spring, wherein the flow plate blocks fuel from flowing into the secondary circuit when the biasing spring is fully extended, and allows fuel to flow into the secondary circuit when the biasing spring is compressed.

In yet another aspect, embodiments of the invention provide a method of making a multiphase fuel injector. The method includes the step of using additive manufacturing to construct an injector body, wherein using additive manufacturing to construct the injector body comprises constructing the injector body to include a fuel inlet at a first end of the injector body and a fuel outlet at a second end of the injector body opposite the first end. A primary circuit is disposed within the injector body proximate the fuel inlet, and extends into a central portion of the injector body. The primary circuit has a fuel swirler disposed in an opening within the injector body. The fuel swirler is configured to direct a first flow of pressurized fuel to a spin chamber and to impart a swirling motion to the first flow of pressurized fuel. A secondary circuit is located within the injector body and positioned radially outward from the primary circuit. The secondary circuit has one or more helical secondary openings formed in the injector body. The one or more helical secondary openings are configured to direct a second flow of pressurized fuel toward a fuel outlet and to impart a swirling action to the second flow of pressurized fuel. The fuel swirler is cylindrical with helical grooves formed in an exterior surface of the fuel swirler.

Embodiments of the invention provide an improvement to the state of the art with respect to fuel injectors. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.

In one aspect, embodiments of the invention provide a multiphase or dual-circuit fuel injector, in which primary and secondary circuits are separated at the tip of the injector. Embodiments of the multiphase or dual-circuit fuel injector include a single fuel inlet, where the primary circuit provides better atomization for reliable light-off, and a quickly opening secondary circuit (resulting in a higher flow number (FN)) allows for the engine to go to maximum power very quickly. The multiphase fuel injector also eliminates the moving components (e.g., the pintle) and both manufacturing and operational complexity which may be present in some conventional variable-area fuel injectors (VAFI).

In particular embodiments, atomization quality during light-off and fuel flow transition from light-off condition to max power quickly is improved in comparison to conventional fuel injectors. Limited or non-moving components located inside the fuel nozzle help to maintain a consistent transition for improved performance.

In another aspect, embodiments of the invention provide a multiphase fuel injector that includes an injector body having an opening at a first end of the injector body. The opening defines a fuel inlet. A primary circuit is disposed proximate the opening in a central portion of the injector body. The primary circuit is configured to receive a flow of pressurized fuel from the fuel inlet and discharge the fuel toward a central portion of a spin chamber located in the injector body downstream from the fuel inlet. The primary circuit is configured to create a swirling action in the flow of pressurized fuel. A secondary circuit is located in the injector body radially outward from the primary circuit proximate an inner wall of the injector body. The secondary circuit is configured to receive a flow of pressurized fuel from the fuel inlet and discharge the fuel toward a perimeter portion of the spin chamber. The secondary circuit is configured to create a swirling action in the flow of pressurized fuel.

As used in this application, the term "axially" refers to distances traversed in a direction from one end of the fuel injector to the opposite end, e.g., from the fuel inlet to the fuel outlet, where, in some embodiments, a longitudinal axis of the fuel injector runs through the center of the cylindrical injector from one end to the opposite end. As used in this application, the term "radially" refers to directions and distances perpendicular to the longitudinal axis, e.g., from the longitudinal axis to a wall of the cylindrical injector and beyond. In the context of the.

In a particular embodiment of the invention, the primary circuit includes a flow plate attached to a biasing spring, wherein the flow plate blocks fuel from flowing into the secondary circuit when the biasing spring is fully extended, and allows fuel to flow into the secondary circuit when the biasing spring is compressed.

Current pintle-style variable-area fuel injectors (VAFI) tend to be relatively complex and expensive devices. It is desired that these types of fuel injectors have a high degree of fuel atomization for light-off, and the ability to quickly go to maximum power (i.e., to increase fuel flow quickly) for missile applications. It is challenging to meet both requirements using a single-orifice fuel injector just simply due to the orifice curve. To meet higher flow requirements, it is advantageous for the injector to have a large orifice diameter, but this tends to produce poor spray quality which affects light-off performance.

<FIG> is a cross-section view of a multiphase fuel injector <NUM>, constructed in accordance with an embodiment of the invention. In certain embodiments, the multiphase fuel injector <NUM> shown in <FIG> and on the far right of <FIG> provide a low cost, additively manufactured fuel injector <NUM> with fewer moving components, improved accuracy, with a reliable approach to regulating the large flow turndown ratios necessary throughout the required performance envelope. Embodiments of the multiphase fuel injector <NUM> are able to generate recirculation using a swirling component of the secondary circuit <NUM> when the fuel changes phase from liquid to gas.

<FIG> is a cross-sectional view of conventional fuel injector <NUM>. This conventional fuel injector <NUM> is a variable area fuel injector that requires a high-accuracy spring <NUM>, a pintle <NUM>, and a nozzle body <NUM>. As the fuel pressure flowing into an inlet end <NUM> increases, the pintle <NUM> moves downstream and opens the active area of the fuel injector orifice <NUM> to increase the flow number or essentially increase fuel flow. A complex balance is required for orifice size selection to meet both ends (i.e., high fuel flow rate and a high degree of atomization) of the performance envelope.

Embodiments of the present invention eliminate the need for a high-accuracy spring <NUM> (metering type) and for the moving pintle <NUM>. As such, the multiphase fuel injector <NUM> of <FIG> improves on some of the above-described shortcomings of the conventional fuel injector <NUM>. In <FIG>, the multiphase fuel injector <NUM> has a single fuel inlet <NUM> that extends close to a tip area and splits into a primary circuit <NUM> and the secondary circuit <NUM> using a simple spring <NUM>. Within a body <NUM> of the multiphase fuel injector <NUM> and just downstream of the opening in the injector <NUM> that defines the fuel inlet <NUM>, there is a larger opening in the injector body <NUM> that accommodates a flow plate <NUM> and the simple spring <NUM>, which are described in more detail below. The primary circuit <NUM> could be sized very small to provide a higher degree of atomization for reliable light-off. At certain pressures, the secondary circuit <NUM> will open such that the multiphase fuel injector <NUM> operates as a fixed orifice curve fuel injector. In certain embodiments, the secondary circuit <NUM> is sized to provide an extremely high flow rate, and to provide a swirling component in the fuel flow for engine combustion operability.

In the embodiment of <FIG>, the flow plate <NUM> is positioned within the body <NUM> of the multiphase fuel injector <NUM> adjacent to the fuel inlet <NUM>. The flow plate <NUM> may be cylindrical or piston-shaped with a central opening <NUM> positioned at the fuel inlet <NUM>, such that fuel flows first through the fuel inlet <NUM>, then through the central opening <NUM> and downstream into a central portion of the injector body <NUM>. Downstream from the central opening <NUM>, the flow plate <NUM> has a larger opening inside of which the spring <NUM> is seated. This larger opening extends to the end of the flow plate <NUM> opposite the end with the central opening <NUM>. Thus, this largely hollow, open end of the flow plate <NUM> houses at least some portion of the spring <NUM> and constitutes a part of the primary circuit <NUM> leading to the helical or spiraling openings used to impart a swirling motion to the fuel flowing in the primary circuit <NUM>. The spring <NUM> may be attached to the flow plate <NUM>, or may just abut the flow plate <NUM> without any attachment. In the embodiment shown, the spring <NUM> is disposed in a portion of the multiphase fuel injector <NUM> that extends from the fuel inlet <NUM> about halfway towards the middle of the injector body <NUM>. When the spring <NUM> is fully extended, the flow plate <NUM> abuts an interior end of the injector body <NUM> adjacent to the fuel inlet <NUM>.

A trim orifice <NUM> may be placed within, and attached to, an interior surface of the central opening <NUM>. The trim orifice <NUM> reduces the diameter of the central opening <NUM> in order to regulate the amount of fuel that can enter into the injector body <NUM>. Depending on the particular application, trim orifices <NUM> of varying sized can be placed within the central opening <NUM> to ensure the correct amount of fuel is output from the multiphase fuel injector <NUM>. Fuel entering the injector body <NUM> via the central opening <NUM> then flows through the primary circuit <NUM>, which may include one or more helical or spiraling primary openings <NUM> in the injector body <NUM> in order to introduce a swirling motion to the fuel flowing out of the primary circuit <NUM> and into a spin chamber <NUM>. As a result of the one or more helical or spiraling primary openings <NUM> in the injector body <NUM>, a swirling flow of pressurized fuel flows out of the primary openings <NUM>, into the spin chamber <NUM>, through primary outlet port <NUM>, and then to the fuel outlet <NUM>.

When the pressure of the fuel entering the inlet <NUM> is sufficiently high, the fuel flow acts on the flow plate <NUM> to compress the spring <NUM>. As the fuel flow pressure increases, the flow plate <NUM> moves downstream into the central portion of the injector body <NUM>. As the flow plate <NUM> moves downstream, the inlet to the secondary circuit <NUM> opens and fuel is able to flow into the secondary circuit <NUM>. In the embodiment shown, the secondary circuit <NUM> has one or more openings that extends radially outward from the inlet of the secondary circuit <NUM>, subsequently extending both axially and linearly along a radially-outward section of the injector body <NUM>. These one or more axially- and linearly-extending openings transition to one or more helical or spiraling secondary openings <NUM> in the injector body <NUM> in order to introduce a swirling motion to the fuel flowing out of the secondary circuit <NUM>. The one or more spiraling secondary openings <NUM> of the secondary circuit <NUM> are located radially-outward from the one or more spiraling primary openings <NUM> of the primary circuit <NUM>. The swirling flow of pressurized fuel then flows out of the one or more spiraling secondary openings <NUM> through a secondary outlet port <NUM>, and then to the fuel outlet <NUM>.

The injector body <NUM>, including the features of the primary circuit <NUM> and the secondary circuit <NUM>, may be manufactured using additive manufacturing, also referred to as <NUM>-D printing. Additive manufacturing facilitates the inclusion of spiraling primary openings <NUM> and spiraling secondary openings <NUM> in the injector body <NUM>. As can be seen in the cross-sectional view of <FIG>, the spiraling primary openings <NUM> and spiraling secondary openings <NUM> are shown as a plurality of openings in the solid material of the injector body <NUM>.

In embodiments of the invention, the multiphase fuel injector <NUM> provides high accuracy, high turndown ratios, reliable transition. While conventional variable area fuel injectors typically have fuel turndown ratios of about <NUM>, the multiphase fuel injector <NUM> has a typical fuel turndown ratio of <NUM>, or possibly more. Further, the maximum fuel flow for the multiphase fuel injector <NUM> is generally two to three times the maximum flow for a conventional variable area fuel injector. Some features of the multiphase fuel injector <NUM> include, but are not limited to, very low fuel mass flow rate at start condition; high turndown flow ratio (e.g., <NUM>-<NUM> times higher than conventional variable-area fuel injectors (VAFI)); passive system with no moving parts; elimination of flow shift and pintle failures; and additional swirling component in the secondary circuit. While the ratio of fuel flow rate to the square root of the differential pressure, known as the flow number (FN), for a conventional variable-area fuel injector typically ranges from <NUM> to <NUM>, the FN for the multiphase fuel injector ranges from <NUM> to <NUM>, proving a larger turndown ratio.

<FIG> is a cross-sectional view of an alternate embodiment of the multiphase fuel injector <NUM>, constructed in accordance with an embodiment of the invention. Similar to the injector <NUM> shown in <FIG>, the multiphase fuel injector <NUM> of <FIG> has a single fuel inlet <NUM> that extends close to a tip area and splits into a primary circuit <NUM> and the secondary circuit <NUM> using a simple spring <NUM>. The primary circuit <NUM> could be sized very small to provide a higher degree of atomization for reliable light-off. At certain pressures, the secondary circuit <NUM> will open such that the multiphase fuel injector <NUM> operates as a fixed orifice curve fuel injector. In certain embodiments, the secondary circuit <NUM> is sized to provide an extremely high flow rate, and to provide a swirling component in the fuel flow for engine combustion operability.

Also, similar to the embodiment of <FIG>, multiphase fuel injector <NUM> has a flow plate <NUM> is positioned within a body <NUM> of the multiphase fuel injector <NUM> adjacent to the fuel inlet <NUM>. The flow plate <NUM> may be cylindrical or piston-shaped with a central opening <NUM>, positioned at the fuel inlet <NUM>, through which fuel flows into the injector body <NUM>. At the end of the flow plate <NUM> opposite the end with the central opening <NUM>, the flow plate <NUM> has a largely hollow open end which accommodates the spring <NUM>. In the embodiment shown, the spring <NUM> is disposed in a portion of the multiphase fuel injector <NUM> that extends from the fuel inlet <NUM> about halfway towards the middle of the injector body <NUM>. When the spring <NUM> is fully extended, the flow plate <NUM> abuts an interior end of the injector body <NUM> adjacent to the fuel inlet <NUM>.

A trim orifice <NUM> may be placed within, and attached to, an interior surface of the central opening <NUM>. The trim orifice <NUM> functions in the same way as trim orifice <NUM> described hereinabove. As in the embodiment described above, when the pressure of the fuel entering the inlet <NUM> is sufficiently high, the fuel flow acts on the flow plate <NUM> to compress the spring <NUM>. As the flow plate <NUM> moves into the injector body <NUM>, fuel is able to flow into the secondary circuit <NUM>. In the embodiment shown, the secondary circuit <NUM> includes one or more helical or spiraling secondary openings <NUM> in the injector body <NUM> in order to introduce a swirling motion to the fuel flow. Both the primary and secondary circuits <NUM>, <NUM> introduce a swirling motion to the fuel flowing through the circuits <NUM>, <NUM>. The swirling fuel then flows out of the primary and secondary circuits <NUM>, <NUM> to the injector outlet <NUM> via a primary outlet port <NUM> and secondary outlet port <NUM>, respectively. Fuel flow from the primary circuit <NUM> passes through a spin chamber <NUM> before reaching the injector outlet <NUM>.

However, the multiphase fuel injector <NUM> differs from the embodiment of <FIG> in that multiphase fuel injector <NUM> does not include one or more spiraling primary openings <NUM> formed in the injector body <NUM> using additive manufacturing. Instead, in certain embodiments of the invention, the multiphase fuel injector <NUM> has an opening in the injector body <NUM> for the insertion of a fuel swirler <NUM> with helical grooves <NUM> machined, formed, or molded into an outer surface of the fuel swirler <NUM>. In particular embodiments, the fuel swirler <NUM> is cylindrical and the helical grooves <NUM> extend around the sidewalls of the cylinder from an inlet end of the fuel swirler <NUM> to an outlet end. In the embodiment of <FIG>, the one or more spiraling secondary openings <NUM> of the secondary circuit <NUM> are located radially-outward from the fuel swirler <NUM>.

It is envisioned that, with the embodiment shown in <FIG>, different fuel swirlers <NUM>, with different characteristics, could be used in the multiphase fuel injector <NUM> depending on the particular application. Use of a machined or molded, drop-in fuel swirler <NUM> allows for potentially faster, less expensive manufacturing, and more flexibility in the application of the multiphase fuel injector <NUM>.

<FIG> is a graphical illustration showing the relationship between fuel mass flow and fuel pressure drop for both conventional variable area fuel injectors and the multiphase fuel injector <NUM>, <NUM>. As can be seen from <FIG>, the multiphase fuel injector <NUM>, <NUM> has a much wider range of operational capability as compared to conventional variable area fuel injectors. The multiphase fuel injector <NUM>, <NUM> can operate at very low fuel mass flow rates when using only the primary circuit <NUM>, <NUM>, and at very high fuel mass flow rates when using both the primary and secondary circuits <NUM>, <NUM>, <NUM>, <NUM>.

Claim 1:
A multiphase fuel injector comprising:
an injector body (<NUM>, <NUM>) having a fuel inlet (<NUM>, <NUM>) at a first end of the injector body and a fuel outlet at a second end of the injector body opposite the first end;
a primary circuit (<NUM>, <NUM>) disposed proximate the fuel inlet and extending into a central portion of the injector body, the primary circuit configured to receive a first flow of pressurized fuel from the fuel inlet and discharge the fuel into a spin chamber (<NUM>, <NUM>) located in the injector body downstream from the fuel inlet, the primary circuit configured to impart a swirling action to the first flow of pressurized fuel, wherein the primary circuit includes a flow plate (<NUM>, <NUM>) attached to a biasing spring (<NUM>, <NUM>);
a secondary circuit (<NUM>, <NUM>) located in the injector body radially outward from the primary circuit, the secondary circuit configured to receive a second flow of pressurized fuel from the fuel inlet and discharge the fuel into the fuel outlet (<NUM>, <NUM>), the secondary circuit configured to impart a swirling action to the second flow of pressurized fuel,
wherein the flow plate blocks fuel from flowing into the secondary circuit when the biasing spring (<NUM>, <NUM>) is fully extended and allows fuel to flow into the secondary circuit when the biasing spring is compressed.