Patent Description:
Gas turbine engines can have pneumatic actuator systems which use gaseous pressure conveyed by a fluid line. Such fluid lines can have an evacuation passage which can be useful to drain condensation and/or for use as a vent, for instance. If the source of pressurized gas is likely to contain contaminants such as particles for instance, a filter can be used in the fluid line to protect the pneumatic actuator from the contaminants. It can be desired to reduce the weight and size of the filter, but doing so typically affects the filter capacity and may entrain more frequent maintenance, which may be undesired due to factors such as maintenance costs and down time. Accordingly, although former pneumatic actuator system fluid lines have been satisfactory to a certain degree, there always remains room for improvement. <CIT>, <CIT>, <CIT> and <CIT> describe arrangements of the prior art.

According to an aspect of the present invention, there is provided a fluid line segment as claimed in claim <NUM>.

According to another aspect of the present invention,, there is provided a gas turbine engine as claimed in claim <NUM>.

The following optional features may be applied to either of the above aspects.

Optionally and in accordance with any of the above, the orifice is located at a tip of the projection.

Optionally and in accordance with any of the above, the containment cavity is annular around the projection.

Optionally and in accordance with any of the above, the gas path forms an elbow, the containment cavity extending downwardly from a vertex of the elbow.

Optionally and in accordance with any of the above, wherein the containment cavity, projection and evacuation passage are formed in a component which is selectively removable from the body of the fluid line segment.

Optionally and in accordance with any of the above, the gas turbine engine further comprising a screen extending across the gas path, downstream of the containment cavity. According to another aspect of the present invention, there is provided a method of operating a fluid line as claimed in claim <NUM>.

<FIG> illustrates an example of a gas turbine engine. In this example, the turbine engine <NUM> is a turboshaft engine generally comprising in serial flow communication, a multistage compressor <NUM> for pressurizing the air, a combustor <NUM> in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases around the engine axis <NUM>, and a turbine section <NUM> for extracting energy from the combustion gases. The turbine engine terminates in an exhaust section <NUM>.

The fluid path extending sequentially across the compressor <NUM>, the combustor <NUM> and the turbine <NUM> can be referred to as the main gas path <NUM>. The pressure and temperature of the working fluid typically varies significantly along the main gas path <NUM>. The pressure can be significantly higher immediately downstream of the compressor <NUM> than immediately upstream of the compressor <NUM>, for instance, and can be even higher between the combustor <NUM> and the turbine <NUM>, at which point the working fluid can also be particularly hot. In the embodiment shown in <FIG>, the turboshaft engine <NUM> has two compressor and turbine stages, including a high pressure stage associated to a high pressure shaft, and a low pressure stage associated to a low pressure shaft, leading to intermediate pressures between compressor stages or between turbine stages. The low pressure shaft can be used as a power source during use.

Gas turbine engines <NUM> can be equipped with one or more pneumatic actuator system <NUM>. Pneumatic actuator systems can serve various purposes, and typically involve at least one actuator which is driven by gas (typically air) pressure. It can be convenient to use a pneumatic actuator system <NUM> on a gas turbine engine <NUM> given the availability of pressurized gas at various pressures from the main gas path <NUM>. The gas pressure can be conveyed between the desired pressurized gas source, which can be a point along the main gas path <NUM> for instance, to the pneumatic actuator via a fluid line <NUM>. Such fluid lines <NUM> can have an evacuation passage <NUM> which can be useful to drain condensation and/or for use as a vent, for instance. If the source of pressurized gas is likely to contain contaminants such as particles, which may be the case when bleeding air pressure from the main gas path <NUM> of a gas turbine engine <NUM>, a filter <NUM> can be used in the fluid line <NUM> to protect the pneumatic actuator from the contaminants. Filters <NUM> have predetermined contaminant accumulating capacities and need to be changed when they are about to reach that capacity, which can entrain undesired effects such as down time and maintenance costs. Accordingly, on the one hand, one may wish to increase the filter capacity in order to reduce down time and maintenance costs. However, increasing the filter capacity can lead to increasing weight, volume and/or costs of the filter, which may be undesired. There are different types of pneumatic actuator systems <NUM> which can serve different and various purposes.

In the example embodiment presented in <FIG>, the gas turbine engine has an example pneumatic actuator system <NUM> in which the pneumatic actuator is in the form of a piloted valve <NUM>. More specifically, a piloted valve <NUM> is used to control air flow along a pressure relief line <NUM>, to selectively release or not release air pressure upstream of the combustion chamber <NUM> based on sensed operating conditions of the gas turbine engine <NUM>. In this specific example, one or more pressure or temperature sensor <NUM> is used which is connected to a controller <NUM>. Based, potentially amongst other factors, on the sensed temperature or pressure, the controller <NUM> determines whether the operating conditions satisfy criteria for releasing air pressure or not. If the controller <NUM> determines that the criteria are met, the controller <NUM> operates a pilot valve <NUM>, which can be a solenoid valve for instance, and switches the pilot valve <NUM> to an open condition. The pilot valve <NUM> can default to the closed condition in the absence of positive control by the controller, for instance. Once in the open condition, pressurized gas is allowed across the pilot valve <NUM>. The pressurized gas then builds pressure in the fluid line <NUM>, between the pilot valve and the pneumatic actuator of the piloted valve <NUM>, and toggles or otherwise activates the actuator of the piloted valve <NUM> to open the piloted valve <NUM>, which can also be closed by default. When the piloted valve <NUM> is in the open position, the pressure release line <NUM> extending between the point along the main gas path <NUM> where pressure is to be released and the atmosphere can be open, allowing the pressure release.

In the embodiment presented in <FIG>, it can be suitable for the piloted valve <NUM> to be supplied with pressurized gas at a relatively high pressure. This need can be satisfied, in this example, by sourcing the pressurized gas from a point <NUM> along the main gas path <NUM> commonly referred to as P3 air, downstream of the highest pressure compressor stage, in the vicinity of the combustion chamber <NUM>, from an area which can be referred to herein as the combustor region for simplicity. The high pressure air in this region may contain contaminants such as particles in some operating conditions. To protect the actuator of the piloted valve <NUM>, it can be desired to filter any such contaminants at some point along the fluid line <NUM>. In this embodiment, a filter <NUM> is present along the fluid line <NUM> to this end.

Still referring to the example embodiment presented in <FIG>, it will be understood that in some embodiments, it can be convenient or otherwise useful to provide an evacuation passage <NUM> to act as a drain and/or a vent as a segment along the length of the fluid line. Such an evacuation passage <NUM> can be used to evacuate any condensation which may occur in the fluid line, for example, and may also be used as a vent which constantly allows a minor flow of pressurized air circulation for regulation and good function of the fluid line <NUM>. The evacuation passage <NUM> can be integrated to a fitting conventionally connected to other segments of the fluid line <NUM>, and thus form part of a segment <NUM> of the fluid line <NUM>, for instance.

Turning to <FIG>, a first example of such a segment <NUM> is presented. It was found that providing such a segment with a contaminant containment cavity <NUM> could be advantageous in some embodiments. In particular, if the segment <NUM> is provided upstream of the filter <NUM> and configured to collect at least some of the contaminants which can be expected to travel along the fluid line <NUM>, the segment <NUM> can reduce the amount of contaminants which will reach the filter <NUM>, and thereby reduce the frequency at which filter maintenance is required in a scenario where all other variables are kept the same.

In the specific example presented in <FIG>, the segment <NUM> is provided in the form of a fitting defining an L-shaped gas path segment <NUM> internally to a metallic body <NUM>. The gas path segment <NUM>, which can be referred to as a gas path <NUM> for short, can extend from an inlet <NUM> to an outlet <NUM>. Both the inlet <NUM> and the outlet <NUM> can incorporate a corresponding connector and be configured for conventional connection to other segments of the fluid line <NUM>.

While gas turbine engines <NUM> are often used for aircraft propulsion, and aircraft are known to change attitude during flight such as by experimenting roll, pitch and yaw, most aircraft still generally operate within a limited attitude variation envelope relative to gravity, and it can remain convenient to refer to "upward" and "downward" in the context of an aircraft with respect to the most typical orientation of gravity taking into consideration its entire operating envelope.

In the embodiment presented in <FIG>, the containment cavity <NUM> can thus be said to extend downwardly relative the gas path <NUM>, in the sense that it extends downwardly when the aircraft is grounded for instance, or during the most typical orientation of the force of gravity taking into consideration the entire operating envelope.

The downward orientation of the contaminant containment cavity <NUM> offers the possibility that relatively dense contaminants such as solid particles settle downwardly into the bottom <NUM> of the containment cavity under the effect of gravity. Even if there are operating conditions in which this mode of operation does not work because of a change in the orientation of gravity, the embodiment can remain suitable and useful in other operating conditions.

In the specific example illustrated in <FIG>, the containment cavity <NUM> is in fluid communication with the gas path <NUM>, and more specifically with a vertex of an elbow of the gas path <NUM> where two straight segments meet, and accordingly where a relatively abrupt change of orientation of the pressurized gas circulation can occur. This relatively abrupt change of orientation of the pressurized gas circulation can favor contaminant deposition and collection in the containment cavity <NUM>. Indeed, in this example, contaminant particles carried by the pressurized gas circulation are denser than the pressurized gas and may thus tend to continue travelling horizontally due to inertia as they are carried horizontally from the inlet <NUM> to impact the far wall <NUM> of the segment <NUM> at which point the effect of gravity may be greater than the entraining force of the pressurized gas, leading to settling of the contaminant particles at the bottom <NUM> of the containment cavity <NUM>. Alternately, if it is more convenient to invert the inlet and outlet in an alternate embodiment, the pressurized gas coming vertically from above before abruptly changing to a horizontal orientation can drive contaminant particles with a sufficient inertia for contaminant particles to be entrained vertically downward by the combined effect of their inertia and gravity and thereby resist the pull of the pressurized gas in horizontal orientation toward the outlet.

In some alternate embodiments, it can be preferred to further mechanically assist the separation of contaminant particles from the pressurized gas flow. For instance, a mesh, screen, membrane, or other element acting somewhat as a filter can be present across the gas path <NUM> and positioned and configured in such a way to favor collection of contaminant particles with limited effect on pressurized gas circulation. In the context of an embodiment such as presented in <FIG> for instance assembled with the horizontal port configured as an inlet, a screen or other filter can be positioned obliquely across the vertex of the elbow or horizontally in the vertical output leg of the segment, for instance, such as illustrated by schematic lines 56a and 56b for instance. In a similar embodiment assembled with the horizontal port configured as an outlet, a screen or other filter can be positioned vertically across the output leg, in close proximity with the elbow, for instance, such as schematized by schematic line 56c for instance. The presence of such a screen or other filter within the segment <NUM> is optional.

It can be convenient in some embodiments to configure such a fluid line segment <NUM> in a manner to have an evacuation passage <NUM> in addition to a containment cavity <NUM>. An evacuation passage <NUM> can serve to evacuate condensation and/or as a vent, for instance. It can be convenient to combine functionalities into a single fitting having a relatively complex geometry as opposed to providing two separate fittings for different functionalities for example, such as for weight, cost and/or other considerations.

The example presented in <FIG> presents such a configuration where an evacuation passage <NUM> is integrated to the same fluid line segment <NUM> which also provides for the containment cavity <NUM>. The evacuation passage <NUM> leads outside the segment <NUM> from an orifice <NUM> which is in fluid flow communication with the gas path <NUM>. In some cases, it may be suitable for the orifice <NUM> to be positioned at the bottom <NUM> of the containment cavity, but in others, such as in the one illustrated, it can be considered that positioning the orifice <NUM> in the bottom <NUM> of the containment cavity <NUM> is more likely to lead to clogging of the evacuation passage <NUM> by the contaminants.

In the example presented in <FIG>, a projection <NUM> is formed in the containment cavity <NUM>, and more specifically protrudes upwardly from the bottom <NUM> of the containment cavity <NUM>, towards the gas path <NUM>, and the orifice <NUM> can be provided in the projection <NUM> in a manner to be separated from the bottom <NUM> of the cavity <NUM> by a separation distance <NUM>. More specifically, in the illustrated embodiment, the projection <NUM> is somewhat reminiscent of a pillar, is detached from walls of the containment cavity <NUM> which circumscribe it, and the containment cavity <NUM> has an annular shape around the projection <NUM>, but these are design choices and other configurations can be preferred in alternate embodiments. In the illustrated embodiment, the orifice <NUM> is provided at a tip of the projection <NUM> in a manner to maximize the separation distance <NUM> for a given projection height. The shape and relative size of the gas passage legs, evacuation passage <NUM>, containment cavity <NUM> and projection <NUM> can vary from one embodiment to another and selected as a function of the specific intended context of use.

<FIG> presents one alternate example of a fluid line segment <NUM> which incorporates a containment cavity <NUM> and an evacuation passage <NUM>. The shape and size of the containment cavity <NUM>, projection <NUM>, and evacuation passage <NUM> presented in this embodiment can be comparable to the corresponding features of the embodiment presented in <FIG>. However, in this alternate example, the fluid line segment <NUM> is incorporated as a T-shaped fitting where the inlet <NUM> and the outlet <NUM> are horizontally opposed to one another at opposite ends of a straight gas path portion, and the containment cavity <NUM> is provided at the lower end of a vertical passage extending downwardly from an intermediate point along the straight gas path portion. Such a configuration can be suitable in some embodiments, especially in scenarios where the density of the expectable contaminants and the expected velocity of the pressurized gas circulation are such that the contaminants will be expected to be dragged horizontally along the bottom of the gas passage <NUM> by the pressurized gas until they will become free to fall into the vertical passage into the containment cavity <NUM>. Another distinction with the embodiment presented in <FIG> is that in this embodiment, the containment cavity <NUM>, the projection <NUM> and the evacuation passage <NUM> are formed in a component <NUM> which is distinct from the body <NUM> of the fluid line segment <NUM>, as opposed to forming part of the same body, and this component <NUM> can be selectively removed and replaced in a manner to allow emptying the containment cavity <NUM> of contaminants when desired or found suitable.

In this specific embodiment, the containment cavity <NUM> can be removably connected to the body <NUM> of the fluid line segment <NUM> with a standard conical connector <NUM>, for instance. The T-Fitting can be part of a tubing assembly or be provided with connectors allowing connection with <NUM> tube ends. In the embodiment presented in <FIG> and <FIG>, an inlet connector and an outlet connector are present in the form of broadening sections configured to receive tube ends therein. Tube connections can either be brazed, welded or connected using standard conical (nipple) connectors. In some embodiments, connectors which provide for selective removal and replacement of the containment cavity from the fluid line segment, or for selective removal and replacement of the fluid line segment from the fluid line can be preferred as this functionality can be used for cleaning of the fluid line segment. In a T-shaped configuration, if a screen or other filter is used, it can extend vertically across the outlet leg, immediately downstream of the vertex, or diagonally across the vertex for instance.

Claim 1:
A fluid line segment (<NUM>;<NUM>) comprising:
a body (<NUM>;<NUM>) having an inlet (<NUM>;<NUM>), an outlet (<NUM>;<NUM>), and a gas path (<NUM>) extending between the inlet (<NUM>;<NUM>) and the outlet (<NUM>;<NUM>);
a containment cavity (<NUM>;<NUM>) extending between the gas path (<NUM>) and a cavity bottom (<NUM>) of the containment cavity (<NUM>;<NUM>), the containment cavity(<NUM>;<NUM>) in fluid communication with the gas path (<NUM>);
a projection protruding from the cavity bottom (<NUM>) of the containment cavity (<NUM>;<NUM>) towards the gas path (<NUM>);
an orifice (<NUM>) defined in the projection (<NUM>;<NUM>); and
an evacuation passage (<NUM>;<NUM>) extending from the orifice (<NUM>), across the projection (<NUM>;<NUM>) and leading outside the body (<NUM>;<NUM>), the evacuation passage (<NUM>) being in fluid communication with the containment cavity (<NUM>;<NUM>) and the gas path (<NUM>) via the orifice (<NUM>).