1. Field of the Invention
The present disclosure relates to valves, and more particularly to bypass valves such as used in proximity to filters installed in fuel, oil, hydraulic, refrigeration, or pneumatic systems of aircraft engines.
2. Description of Related Art
Bypass valves are used in aircraft jet fuel and oil systems typically in filtering applications. A separate pressure sensor measuring the fluid flow pressure across the bypass valve is typically used to monitor the state of the bypass valve and, thus, infer the condition of the filter it protects. These pressure sensors require remote housing cores to access the upstream and downstream pressures relative to the filter. Pressure sensors' housing cores can be problematic as they add additional footprint and weight to a design. Another potential operational drawback with pressure sensors is the risk of amplification of pressures pulsations typically inherent in incompressible fluid systems as driven by the pumping architecture providing the fluid source pressure. These pressure sensors are designed to be readily removable for inspection and/or rapid replacement. Thus, the additional filter accessories (i.e., bolts, seals, fixtures, etc.) add complexity to the filter's housing design.
Such pressure detection devices have generally been considered adequate for their intended purposes, however, this is an ongoing need for improved bypass valves. The present disclosure provides a solution for this need.
A bypass valve includes a housing for directing fluid flow through the bypass valve. A disc is positioned within the flow path having an inner perimeter and an outer perimeter. The bypass valve further includes at least one strain gauge disposed on the disc. One of the inner and outer perimeters of the disc is fixed to the bypass valve housing and one of the inner and outer perimeter of the disc is free to deflect from the bypass valve housing in response to fluid flow through the bypass valve such that a measurement of deflection of the disc induces strain on the strain gauge.
The disc can be configured to deflect as a function of pressure of fluid flow through the bypass valve. An amount of deflection of the outer perimeter of the disc can generate strain on the disc proportional to the pressure of fluid flow through the bypass valve.
The disc can have a first position defined by the free perimeter adjacent the housing configured to seal with the housing in the first position. The disc can have a second position defined by the free perimeter separated from the housing configured to allow fluid flow through the bypass valve. The disc can include an upstream surface configured to allow fluid to pass over the disc and the strain gauge can be coupled to a downstream surface of the disc opposite the upstream surface. The disc can be metal and can be loaded into the housing for creating a metal to metal seal of the valve in the first position. A portion of housing that the inner perimeter of disc is coupled to can be threaded with a screw feature to lock-in the position of the disc. The bypass valve can further include a harness in communication with strain gauge configured to provide feedback of the deflection of the outer perimeter of said disc to a control system. The bypass valve can include two strain gauges. The inner perimeter of said disc can be fixed to the bypass valve housing and the outer perimeter of said disc can be free to deflect away from the bypass valve housing.
These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings.
So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein:
Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a partial view of an exemplary embodiment of an integrated bypass valve in accordance with the disclosure is shown in
With reference to
The bypass valve 120 includes an inlet 122 and an outlet 124 for directing fluid flow through the bypass valve 120. A flat metal disc 110 acts as the bypass valve 120 where the flat disc 110 is restrained along one of its perimeters. More specifically, the disc 110 has an inner 130 and an outer perimeter 132 wherein one of the inner 130 and outer perimeters 132 is fixed to the housing 100 (i.e. a fixed perimeter) and one of the inner and outer perimeters 130, 132 is free to deflect (i.e. a free perimeter) as pressure of fluid flow through the bypass valve 120 increases. As shown in
Peak stress across the bypass valve 120 is experienced closest to the housing 100 that restrains the disc's 110 inner perimeter 130 and, therefore, acts as an ideal location for measurement of strain. Strain is proportional to the pressure load across the bypass valve 120 that acts to deflect the disc 110 during a bypass event as shown in
As shown in
Knowing the area, pressure drop, density, and discharge coefficient will allow flow to be calculated past the bypass valve 120. The bypass valve 120 provides the area and pressure inputs.
Fluid density can be provided by a separate fluid temperature measurement for improved accuracy. Typically most fuel and oil and hydraulic systems incorporate temperature measurement and this input is readily available through the Electronic Engine Control (EEC)/Full Authority Digital Engine Control (FADEC). It should be noted that the spring rate of the deflecting disc will be affected by temperature and accuracy of the desired measurement. This may mandate measurement of fluid temperature local to the bypass valve's disc 110. A thin film Resistance Temperature Detector (RTD), or a surface mount Thermally Sensitive Resistor (TSR), can be locally employed to provide correction for changes in the spring rate of the disc. Flow past an orifice can be simply expressed as shown in equation (1):
Q=C
d
A/ρΔP (1)
where:
Q—total flow
Cd—discharge coefficient
A—cross-sectional flow area of orifice
ρ—density of fluid
ΔP—pressure drop of fluid flowing through orifice
In regards to the disclosed bypass valve 120, the discharge coefficient, Cd, can be determined experimentally. This discharge coefficient defines the performance of the bypass valve 120 within the housing 100 and can be used as an input to flow measurement. Given the inputs from the bypass valve 120 of fluid pressure and bypass valve cross-sectional open flow area coupled with a system input for fluid density, the measurement of flow is readily determined.
The described bypass valve 120 can be calibrated to enable the intended function. The inner perimeter 130 of the bypass valve disc 110 in contact with the housing 100 can be secured with a large threaded feature such as a spanner nut. An additional set screw feature 164 is required to lock the position of the calibrated spanner nut in place. This concept allows for the proper preload adjustment. Any failures of the bypass valve 120 operation can be registered in the integrated aircraft monitoring systems (e.g., the Engine Indicating and Crew Alerting System/Engine Centralized Aircraft Monitor) and become latched upon the activation of the Weight-on-Wheels=1 (WOW=1) switch as needed. This provides some level of “intelligence” to the proposed bypass valve 120 by automatically alerting ground maintenance crews of any impending/required parts replacements. This in turn, optimizes aircraft ground turn-around times, minimizes the Aircraft On Ground (AOG) times, and improves overall operational efficiency of the aircraft.
The methods and systems of the present disclosure, as described above and shown in the drawings, provide for a bypass valve with superior properties including measurement of strain across the bypass valve. While the apparatus and methods of the subject disclosure have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the scope of the subject disclosure.