Patent Description:
Flow regulating valves are integral components to providing a constant flow rate of fluid as requested by an external command to a combustion chamber, regardless of the inlet flow at the flow regulating valve. Historically, flow regulating valves have been damped with either a laminar leak path or via orifices in non-flowing sense lines.

Laminar leak path damping can provide linear damping over the full range of valve velocities. However the damping is proportional to the kinematic viscosity of the fluid being regulated, therefore the damping is sensitive to temperature variations of the fluid media.

Non-flowing orifice damping exhibits less temperature sensitivity than valves using laminar leak path damping. However, non-flowing orifice damping is proportional to the square of valve velocity. As a result, the orifice provides no damping when the valve is stationary (e.g., valve velocity equal to zero), but can over-damp the valve during large disturbances.

<CIT> and <CIT> disclose fuel flow regulator systems of the prior art.

In general, this document describes fluid flow regulators.

In a first aspect, a fuel flow regulator system according to claim <NUM> is provided.

Various implementations are defined by dependent claims <NUM> to <NUM>.

In a second aspect, a method of regulating fluid flow is provided according to claim <NUM>.

The systems and techniques described here may provide one or more of the following advantages. First, a system can provide damping of the flow regulator that is independent of amplitude by using a flowing damping orifice damping arrangement. Second, the system can be arranged such that there are no additional pump draw requirements, thereby having no impact to pump sizing. Third, the system can implement larger diameter passages than other damping systems, thereby improving the resistance to contamination. Fourth, the system can have reduced leakage sensitivity. Fifth, the system can eliminate the need for one or two check valves that may be required when using prior damping arrangements.

This document describes systems and techniques for regulating fluid flow with a damped response. Flow regulating valves can maintain the flow of fluid provided at the inlet of the flow regulator. Two damping schemes used for flow regulator systems include the use of laminar leak path damping or orifices in non-flowing sense lines.

<FIG> is a schematic diagram of a prior art fluid flow regulator <NUM> that uses laminar leak path damping. The regulator <NUM> includes two distinct pressure signals at <NUM> and <NUM>. The fluid at <NUM> is fluidically connected to fluid path <NUM>, and the fluid at <NUM> is fluidically connected to fluid path <NUM>.

The fluid path <NUM> is fluidically connected to the outlet fluid path <NUM> through a bypass valve <NUM> and a laminar damping orifice <NUM>. The bypass valve <NUM> includes a number of ports (not shown) that fluidically connects the inlet fluid path <NUM> to the outlet fluid path <NUM>. The bypass valve <NUM> exhibits a regulator velocity, generally represented by the arrow <NUM>. The laminar damping orifice <NUM> restricts fluid flow from the fluid inlet <NUM> to the bypass valve <NUM>. The laminar damping orifice <NUM> includes a close clearance gap through which fluid can flow in a damped manner.

Laminar leak path damping can provide linear damping over a substantial range of valve velocities. However, the damping is proportional to the kinematic viscosity of the fluid being regulated, therefore the damping is sensitive to temperature variations of the fluid media. At low regulator velocities <NUM> of the bypass valve <NUM>, low flow is induced across the laminar damping orifice <NUM>. The flow across laminar damping orifice <NUM> results in a differential pressure drop that is proportional to flow (e.g., linear). In addition, laminar flow is inversely proportional to fluid kinematic viscosity. Therefore, damping varies with the temperature of the fluid being flowed. For example, typical aircraft fuels and operational temperature ranges can result in fuel viscosity variations from <NUM> centistokes (-65F JetA) to <NUM> centistokes (300F JetA), resulting in temperature-induced damping variations of approximately 50X. Such levels of damping variation can be difficult to design for over an entire operating envelope of an aircraft engine. As such, the laminar leak path damping architecture of the regulator <NUM> may be seldom implemented with modern aircraft engine embodiments.

<FIG> is a schematic diagram of a prior art fluid flow regulator <NUM> that uses non-flowing orifice damping. The regulator <NUM> includes a fluid at <NUM> and a fluid at <NUM>. The fluid at <NUM> is fluidically connected to a fluid path <NUM>, and the fluid at <NUM> is fluidically connected to a fluid path <NUM>.

The inlet fluid path <NUM> is fluidically connected to the outlet fluid path <NUM> through a bypass valve <NUM>. The bypass valve <NUM> includes a number of ports (not shown) that fluidically connects the inlet fluid path <NUM> to the outlet fluid path <NUM>. The bypass valve <NUM> exhibits a regulator velocity, generally represented by the arrow <NUM>. A damping orifice <NUM> restricts fluid flow from the bypass valve <NUM> to the fluid outlet <NUM> along the outlet fluid path <NUM>. In some embodiments, the fluid flow regulator <NUM> can also include a damping orifice <NUM> that restricts fluid flow from the fluid inlet <NUM> to the bypass valve <NUM>.

Non-flowing orifice damping exhibits less temperature sensitivity than valves using laminar leak path damping. However, non-flowing orifice damping is proportional to the square of the regulator velocity <NUM>. As a result, the orifice provides little to no damping when the bypass valve <NUM> is stationary (e.g., valve velocity <NUM> is equal to zero), but can over-damp the bypass valve <NUM> during large disturbances.

At low regulator velocities, low flow is induced across the damping orifices <NUM> and <NUM>. The induced flow across the damping orifices <NUM> and <NUM> results in a differential pressure drop that is proportional to the square of flow (e.g., non-linear). In examples in which the orifices <NUM>, <NUM> are appropriately sized (e.g., greater than about <NUM> inches diameter), the differential pressures generated by low regulator velocities may be negligible, resulting in little to no damping of the bypass valve <NUM>. In addition, orifice flow is proportional to the square root of fuel specific gravity, and is substantially independent of fuel viscosity. For example, typical aircraft fuels and temperature ranges can result in fuel specific gravity from <NUM> (-65F JetA) to <NUM> (300F JetA), resulting in a damping variation due to temperature of approximately <NUM>.

In aircraft applications, space and weight can be limited commodities. Use of the pressure regulator <NUM> of <FIG> in such examples may allow high-frequency pressure oscillations in the fuel to go substantially undamped across the valve <NUM>. For example, the operations of fuel injectors downstream of the pressure regulator <NUM> may introduce oscillations that can back-propagate and cause problems with equipment upstream from the pressure regulator <NUM> (e.g., noisy sensor readings, damage to fuel pumps). In another example, oscillations introduced upstream of the pressure regulator <NUM> (e.g., by fuel pumps, vibration from the engine) can propagate to and interfere with the function of equipment downstream from the pressure regulator (e.g., fuel injectors).

<FIG> is a schematic diagram of an example fluid flow regulator <NUM>. The regulator <NUM> includes a fluid at <NUM> and a fluid at <NUM>. The fluid at <NUM> is fluidically connected to an inlet fluid path <NUM>, and the fluid at <NUM> is fluidically connected to an outlet fluid path <NUM>.

A fluid with a flow to be regulated is provided at the fluid inlet <NUM> of the inlet fluid path <NUM>. The inlet fluid path <NUM> is fluidically connected to the outlet fluid path <NUM> through a bypass valve <NUM>. The bypass valve <NUM> includes a number of ports (not shown) that fluidically connects the inlet fluid path <NUM> to the outlet fluid path <NUM>. A spring <NUM> urges the valve <NUM> toward a position that restricts or blocks fluid flow between the inlet fluid path <NUM> and the outlet fluid path <NUM>. The valve <NUM> is responsive to changes in pressure differential <NUM> and <NUM> across it. In general, as pressure at the inlet fluid path <NUM> decreases, the bias force of the spring <NUM> urges the valve <NUM> toward a position that decreases allowable flow area between inlet fluid path <NUM> and the outlet fluid path <NUM>. Decreasing the allowable flow area of bypass valve <NUM> also decreases the rate of flow from the inlet fluid path <NUM> to the outlet fluid path <NUM>. The flow rate remains approximately at a specified level even though pressure at the valve <NUM> varies.

The bypass valve <NUM> exhibits a regulator velocity, generally represented by the arrow <NUM>. A damping orifice <NUM> restricts fluid flow from the bypass valve <NUM> to the fluid outlet <NUM> along the outlet fluid path <NUM>. In some embodiments, the fluid flow regulator <NUM> can also include a damping orifice <NUM> that restricts fluid flow from the fluid inlet <NUM> to the bypass valve <NUM>.

A bypass fluid path <NUM> fluidically connects the inlet fluid path <NUM> to the outlet fluid path <NUM> in parallel with the bypass valve <NUM>. The bypass flow path <NUM> includes a minimum flow orifice <NUM> that restricts fluid flow from the fluid inlet path <NUM> to the fluid outlet path <NUM>. In some embodiments, the minimum flow orifice <NUM> can be sized based on a predetermined minimum fluid flow.

The regulator <NUM> maintains the advantage of temperature insensitivity similar to the non-flowing orifice damping design of the example regulator <NUM> of <FIG>, but also provides linear damping similar to that provided by the example regulator <NUM> of <FIG>. By using the configuration of the example regulator <NUM>, the regulator has the same damping when stationary as during large transients. In the example regulator <NUM>, the minimum flow orifice <NUM> converts the damping orifices <NUM> and <NUM> of the bypass valve <NUM> from non-flowing orifices to flowing orifices. As a result, damping of the bypass valve <NUM> becomes less amplitude dependent, yet leakage is not impacted.

Given the flowing orifice configuration of the example regulator <NUM>, there exists a continuous, non-zero flow across the damping orifices of the bypass valve <NUM> and the minimum flow orifice <NUM>. The continuous flow across the damping orifices of the bypass valve <NUM> results in a differential pressure drop induced across the damping orifices, which serves as a mechanism for damping at low valve velocities (<NUM>) as well as high valve velocities (<NUM>). Similar to the non-flowing orifice configuration of the example regulator <NUM>, the flowing orifice configuration of the regulator <NUM> is insensitive to fluid viscosity variation due to temperature changes.

Additionally, the flowing orifice configuration of the example regulator <NUM> has a larger diameter damping orifice(s) than is appropriate to provide the similar levels of bypass damping in regulators that implement a non-flowing orifice configuration. In some implementations, the configuration of the regulator <NUM> can provide a number of advantages over the damping schemes implemented by the regulators <NUM> and <NUM>. For example, the relatively larger damping orifices of the regulator <NUM> can provide relatively improved contamination resistance. In another example, the regulator <NUM> can exhibit relatively reduced leakage sensitivity since small amounts of bypass leakage, which is typically temperature dependent, has been known to bias the pressure differential setting of bypass valves, resulting in fuel flow errors. The configuration of the regulator <NUM> reduces this leakage sensitivity. In another example, some other regulator designs require the use of check valves in parallel to the relatively smaller bypass orifices, resulting in added weight and cost. Such check valves are not needed in the configuration of the regulator <NUM>.

<FIG> is a schematic diagram of an example fluid delivery system <NUM> that includes fluid flow regulator damping, such as that provided by the example regulator <NUM> of <FIG>. The system <NUM> includes a bypass valve <NUM>, a metering valve <NUM>, and a pressurizing valve <NUM> (e.g., pressure regulator). In some implementations, the system <NUM> can regulate fuel flow to an aircraft engine. In general, a fluid <NUM> (e.g., fuel) is provided at a fluid inlet <NUM>. The fluid flows to a meter inlet <NUM> of the metering valve <NUM>, and out from a meter outlet <NUM> to a pressurizing valve inlet <NUM> of the pressurizing valve <NUM>.

The metering valve <NUM> is responsive to an external servo valve (not shown). The servovalve is coupled to actuate plunger <NUM>, metering valve plunger position is communicated to an electronic control via a position feedback device <NUM>. As the metering valve moves, a fluid path between a valve inlet <NUM> and a valve outlet <NUM> is selectively opened and closed. In use, the metering valve <NUM> can be actuated to adjust a rate of fluid flow at the valve outlet <NUM>.

The bypass valve <NUM> includes a collection of ports <NUM>. The bypass valve is actuated in response to the difference in fluid pressure developed in fluid conduit <NUM> and <NUM>. Fluid conduit <NUM> can be described as fluid pressure in a fluid path between a minimum flow orifice <NUM> and a damping orifice 472b. Fluid conduit <NUM> can be described as fluid pressure in a fluid path between a minimum flow orifice <NUM> and a damping orifice 472a. When force exerted on the bypass valve <NUM> by the pressure differential in fluid conduit <NUM> and <NUM> is not sufficient to overcome the force provided by a spring <NUM>, the bypass valve closes and restricts flow of the fluid <NUM> to an outlet <NUM>. As the force exerted on the bypass valve <NUM> by the pressure differential in the fluid conduit <NUM> and <NUM> exceeds the opposing force, the valve <NUM> opens and allows flow to pass to the outlet <NUM>.

The pressurizing valve <NUM> includes a spring <NUM> and plunger <NUM>. The spring <NUM> and a force provided by the pressure of the fluid <NUM> applied at the input <NUM> biases the plunger <NUM> into the fluid flow between the valve outlet <NUM> and the outlet <NUM>. The pressurizing valve <NUM> regulates the pressure of the fluid <NUM> at an inlet <NUM> in response to the pressure of a fluid <NUM> applied at an input <NUM> and a spring force <NUM>. In some embodiments, the bypass valve <NUM> can be the bypass valve <NUM>.

In use, the bypass valve <NUM> maintains a substantially constant differential pressure across the metering window of the metering valve <NUM>. The metering valve <NUM> holds a metering port window that corresponds to the desired flow of the fluid <NUM> (e.g., a desired engine burn flow) in response to an input signal (e.g., from an engine controller or pilot input). The pressurizing valve <NUM> maintains at least a predetermined minimum fluidic pressure used to provide fluidic force margins for the metering valve <NUM> and internal or external actuation systems.

The example system <NUM> also includes the minimum flow orifice <NUM>, the damping orifice 472a, and a damping orifice 472b. The orifices <NUM>, 472a, and 472b restrict a bypass fluid flow path that bypasses the metering valve <NUM>. The bypass fluid flow path extends from the inlet <NUM> and/or the valve inlet <NUM>, through a damping orifice 472b, along the fluid conduit <NUM>, through the minimum flow orifice <NUM>, along fluid conduit <NUM>, through a damping orifice 472a, to the valve outlet <NUM>. The minimum flow orifice <NUM>, which in some embodiments can be the minimum flow orifice <NUM> of <FIG>, can be adjusted to calibrate for low fluid (e.g., fuel) flow requirements. In some embodiments, the minimum flow orifice <NUM> can be sized based on a predetermined minimum fluid flow to be passed through the bypass fluid flow path. In some embodiments, the minimum flow orifice <NUM> can be an adjustable orifice.

In use, the minimum flow orifice <NUM> continuously permits a specified amount of the fluid <NUM> to flow along a fluid path extending from the valve inlet <NUM> to the valve outlet <NUM>, bypassing the fluid path provided by the metering valve <NUM>. The two damping orifices 472a and 472b, which in some embodiments can be the damping orifices <NUM> and <NUM>, are positioned in a series circuit with the minimum flow orifice <NUM>. As such, all the fluid <NUM> that is passed by the minimum flow orifice <NUM> also passes through the damping orifices 472a and 472b. In some embodiments, the fluid flow rate at the valve outlet <NUM> can be the sum of the minimum fluid flow through the minimum flow orifice <NUM> and the regulated fluid flow rate through the metering valve <NUM>.

The portion of the fluid <NUM> bypassing the metering valve <NUM> flows from the fluid inlet <NUM> (and the valve inlet <NUM>, which is at the same pressure as the fluid inlet <NUM>) through the damping orifice 472b, to a fluid conduit <NUM>, to the minimum flow orifice <NUM>, through the damping orifice 472a, and to the valve outlet <NUM>. The flow remains substantially continuous at a specified flow rate, except for displacement flow provided by the bypass valve <NUM> which will add to or subtract from the described flow path. In some implementations, displacement flow from the bypass valve <NUM> can be relatively low compared to metering flow levels, and in cases can be ignored.

<FIG> is a schematic diagram of an example fluid delivery system <NUM> that includes fluid flow regulator damping. The system <NUM> is similar to the example system <NUM> of <FIG>, except that the two damping orifices 472a and 472b are reduced to a single damping orifice <NUM> along the bypass fluid flow path. Given this architecture, the fluid <NUM> flows from the fluid inlet <NUM> (and the valve inlet <NUM>, which is at the same pressure as the fluid inlet <NUM>) through the fluid conduit <NUM>, to the minimum flow orifice <NUM>, and to the valve outlet <NUM>. In some implementations, the configuration shown in <FIG> may be used in an engine fuel delivery application.

In some implementations, the configuration of the system <NUM> simplifies the configuration of the system <NUM>, eliminating the need to install and account for tolerance variations that may be associated with the damping orifice 472b. In some implementations, the configuration of the system <NUM> can cause the minimum flow orifice <NUM> to provide a protective filtering benefit to the damping orifice <NUM>. In some embodiments, the fluid flow rate at the valve outlet <NUM> can be the sum of the minimum fluid flow through the minimum flow orifice <NUM> and the regulated fluid flow rate through the metering valve <NUM>.

<FIG> is a schematic diagram of an example fluid delivery system <NUM> that includes fluid flow regulator damping. The system <NUM> is similar to the example system <NUM> of <FIG>, except that a minimum flow circuit <NUM> fluidically connects the valve inlet <NUM> to the valve outlet <NUM> in parallel with the metering valve <NUM> and the bypass fluid flow path <NUM>. A minimum flow orifice <NUM> is included in the minimum flow circuit <NUM>. Compared to the system <NUM>, the system <NUM> also replaces the minimum flow orifice <NUM> of the system <NUM> with a flow limiter orifice <NUM>. In some implementations, the configuration shown in <FIG> may be used in an engine fuel delivery application. In some embodiments, the minimum flow orifice <NUM> can be an adjustable flow orifice.

Given this architecture, the fluid <NUM> flows from the fluid inlet <NUM> (and the valve inlet <NUM>, which is at the same pressure as the fluid inlet <NUM>) through the fluid conduit <NUM>, to the flow limiter orifice <NUM>, through flow conduit <NUM>, through the damping orifice <NUM>, and to the valve outlet <NUM>, and the minimum flow circuit flows from the valve inlet <NUM>, through the minimum flow orifice <NUM>, to the valve outlet <NUM>. In some embodiments, the fluid flow rate at the valve outlet <NUM> can be the sum of the minimum fluid flow through the minimum flow orifice <NUM> and the damping flow circuit <NUM> and the regulated fluid flow rate through the metering valve <NUM>. In some implementations, the configuration of the system <NUM> can cause calibration of the minimum flow orifice <NUM> to have little or no impact upon the damping performance of the bypass system.

<FIG> is a schematic diagram of an example fluid delivery system <NUM> that includes fluid flow regulator damping. The system <NUM> is similar to the example system <NUM> of <FIG>, except that flow conduit <NUM> includes additional features to prevent icing of the damping flow circuit <NUM>, such as a wash screen assembly <NUM> and a fuel heating element <NUM>. The wash screen assembly <NUM> is resistant to heavy contamination as well as large quantities of ice, and the fuel heating element <NUM> provides fuel temperatures above freezing to preventing ice crystals from building up on the critical features of the damping circuit. In some implementations, the configuration shown in <FIG> may be used in an engine fuel delivery application. In some embodiments, the minimum flow orifice <NUM> can be an adjustable flow orifice.

Given this architecture, the fluid <NUM> flows from the fluid inlet <NUM> through wash screen <NUM>, through the heating element <NUM>, thru the fluid conduit <NUM>, to the flow limiter orifice <NUM>, through flow conduit <NUM>, through the damping orifice <NUM>, and to the valve outlet <NUM>, and the minimum flow circuit flows from the valve inlet <NUM>, through the minimum flow orifice <NUM>, to the valve outlet <NUM>. In some embodiments, the fluid flow rate at the valve outlet <NUM> can be the sum of the minimum fluid flow through the minimum flow orifice <NUM> and the damping flow circuit <NUM> and the regulated fluid flow rate through the metering valve <NUM>. In some implementations, the configuration of the system <NUM> can cause calibration of the minimum flow orifice <NUM> to have no impact upon the damping performance of the bypass system.

The architecture of <FIG> provides the greatest protection for the damping circuit via the wash screen assembly <NUM> and the heating element <NUM>. The wash screen assembly <NUM> is positioned in flow path <NUM> such that the large majority of fluid flow passes down the center of the wash screen assembly <NUM> and through to the valve inlet <NUM>. Only a small percentage of flow passes to conduit <NUM>, thereby providing a continuous washing of the filter media to prevent contamination and ice buildup. The heating element <NUM> is exposed only to the damping flow circuit flow, and therefore can be sized accordingly. The heating element <NUM> may be of various types, including but not limited to electrical, fluid heat transfer, or mechanical. In some embodiments, the fluid conduit <NUM> may be split to provide washed and/or heated fluid to other features within the system <NUM>.

Claim 1:
A fuel fluid flow regulator system (<NUM>, <NUM>, <NUM>, <NUM>) for regulating fluid flow through a fuel delivery path, comprising:
a fluid inlet of an inlet fluid path (<NUM>) of the fuel delivery path;
a fluid outlet along an outlet fluid path (<NUM>, <NUM>) of the fuel delivery path;
a fuel bypass valve (<NUM>) in the fuel delivery path operable to selectively provide a fluid flow restriction to an outlet (<NUM>) of the fuel bypass valve (<NUM>) in response to changes in pressure differential;
characterized by :
a bypass fluid path (<NUM>, <NUM>) fluidically connecting the inlet fluid path (<NUM>) and the outlet fluid path (<NUM>, <NUM>) in parallel with the fuel bypass valve (<NUM>);
a first orifice (<NUM>, <NUM>) restricting the bypass fluid path (<NUM>, <NUM>); and
a second orifice (472a, 472b, <NUM>) restricting one of the inlet fluid path (<NUM>) or the outlet fluid path (<NUM>, <NUM>).