LOW POWER, PULSED, ELECTRO-THERMAL ICE PROTECTION SYSTEM

• US 20070075188A1
• Filed: 05/06/2004
• Published: 04/05/2007
• Est. Priority Date: 05/06/2004
• Status: Active Grant

• Current Assignee: Goodrich Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Goodrich Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Christy, Daniel, Stoner, Paul, Sweet, David
• Granted Patent: US 7,246,773 B2
• Time in Patent Office: Days
• US Class Current: 244/134.D
• CPC Class Codes: B64D 15/14 controlled cyclically along length of surface
• CPC Class Codes: F01D 25/02 De-icing means for engines having icing phenomena
• CPC Class Codes: Y02T 50/60 Efficient propulsion technologies, e.g. for aircraft

Abstract

An electro-thermal ice protection system for an airfoil comprises: a metal foil heater including an integral parting strip, the metal foil heater configurable to cover at least a portion of a leading edge of the airfoil with the integral parting strip disposed along an air-stagnation zone of the leading edge; and a controller coupled electrically to the metal foil heater for controlling electrical energy from a power source to the metal foil of the heater in accordance with a pulse duty-cycle and for controlling power to the parting strip of the heater to maintain the air-stagnation zone virtually free of ice formation. A method of making an exemplary metal foil heater for use in ice protection of an airfoil comprises the steps of: preparing a sheet of Titanium foil in a rectangular shape having a length substantially greater than a width thereof for covering at least a portion of the leading edge of the airfoil; applying a layer of Nickel material over an area along each width edge of the Titanium foil; applying a layer of Copper material over the Nickel layer along each width edge of the Titanium foil; and attaching conductor wires to the Copper layers at each width edge.

Claims

1-72. -72. (canceled)

73. An electro-thermal ice protection system for an airfoil comprising:

at least one metal foil heater including at least one integral parting strip and a metal foil distinct from said at least one parting strip, said at least one metal foil heater configurable to cover at least a portion of a leading edge of said airfoil with said at least one integral parting strip disposed along an air-stagnation zone of the leading edge and said metal foil extending on both sides of the parting strip in a cross-sectional view of the airfoil; and

a controller coupled electrically to said at least one metal foil heater for controlling electrical energy from a power source to the metal foil of said heater in accordance with a first pulse duty-cycle and for controlling power to said parting strip of said heater to maintain said air-stagnation zone virtually free of ice formation;

wherein;

the metal foil is exposed to the atmosphere.

74. The system of claim 73, wherein the heater includes an insulation layer bonded to a leading edge facing side of the metal foil of said heater for electrically and thermally isolating the metal foil from the airfoil.

75. The system of claim 74 wherein the at least one parting strip is embedded in the insulation layer.

76. The system of claim 73, wherein the airfoil is comprised of a composite material;

and wherein the metal foil heater is embeddable in the leading edge of the airfoil.

77. The system of claim 73, wherein the at least one parting strip is disposed on an exposed surface of the metal foil of the heater and electrically and thermally isolated therefrom.

78. The system of claim 73, wherein the heater includes a metal foil rectangular shaped sheet of length and width in which said length dimension being substantially greater than said width dimension;

and wherein the metal foil heater is configurable to cover the leading edge of the airfoil by aligning the length thereof substantially parallel to the span of the airfoil and shaping the width of said rectangular sheet around the leading edge.

80. The system of claim 73, wherein the metal foil of the heater comprises titanium.

81. The system of claim 80, wherein the metal foil includes bus bars for rendering electrical connections thereto, each bus bar including a layer of nickel material bonded to the titanium, and a layer of copper material bonded to the nickel layer.

82. The system of claim 73, wherein the controller includes means for controlling:

(1) heating energy of the power pulse to be sufficient to weaken an interfacial ice bond to the metal foil heater, (2) the duration of said heating pulse in the first duty cycle to permit wind shear forces across the airfoil to peel off ice formations at shed zones on both sides of the air-stagnation zone, and (3) the duration between said heating pulses to permit ice to reform on the metal foil heater to a thickness that can be peeled off of the heated metal foil by said wind shear forces.

83. The system of claim 73, wherein the controller includes a first electrical energy storage device (ESD) chargeable by the power source for use in controlling electrical energy from the power source to the metal foil of the heater in accordance with the first pulse duty-cycle.

84. The system of claim 83, wherein the controller includes means for controlling power to said parting strip of said heater in accordance with a second pulse duty-cycle to maintain said air-stagnation zone virtually free of ice formation.

85. The system of claim 84, wherein the controller includes a second electrical energy storage device (ESD) chargeable by the power source for use in controlling electrical energy from the power source to the parting strip of said heater in accordance with the second pulse duty-cycle of the parting strip.

86. The system of claim 85, wherein the controller includes a first switching arrangement coupled between the first ESD and the metal foil of the heater and controllable to discharge the first ESD into the metal foil at the first duty cycle of the metal foil;

and a second switching arrangement coupled between the second ESD and the parting strip and controllable to discharge the second ESD into the parting strip at the second duty cycle of the parting strip.

87. The system of claim 73, comprising a plurality of metal foil heaters, each metal foil heater covering a distinct portion of a leading edge of said airfoil, and wherein the controller is configured to multiplex electrical energy to said plurality of heaters.

88. The system of claim 87, wherein:

the plurality of heaters are electrically interconnected to each other; and

one metal foil heater of said plurality is coupled at a region through a conductor to a conductive structure of said airfoil for distributing electrical energy of a lightning strike from said region through the conductor to the conductive structure.

89. The system of claim 87, further comprising a switching arrangement for coupling the power source to the plurality of metal foil heaters and operative to multiplex pulses of electrical energy supplied by the power source among the plurality of metal foil heaters.

90. The system of claim 87, further comprising:

an energy storage device for each heater of the plurality; and

a switching arrangement for each heater of the plurality, each switching arrangement operative to couple the power source to the corresponding energy storage device in one state and to couple the corresponding energy storage device to the corresponding heater in another state; and

wherein the controller is coupled to the plurality of switching arrangements and operative to control the states thereof to sequentially charge and discharge the plurality of energy storage devices into their corresponding metal foil heaters.

91. The system of claim 87, furthering comprising:

an energy storage device for storing electrical energy supplied by the power source; and

a switching arrangement coupled between the energy storage device and the plurality of metal foil heaters and operative to discharge stored electrical energy of the energy storage device into each of the plurality of metal foil heaters.

92. The system of claim 91, wherein the energy storage device comprises a plurality of series connected ultracapacitors coupled across source and return lines of the power source.

93. The system of claim 91, wherein the controller is coupled to the switching arrangement for controlling the switching arrangement to multiplex the discharge of stored electrical energy of the energy storage device among the plurality of metal foil heaters.

94. The system of claim 73, comprising a plurality of parting strip segments, each parting strip segment disposed along a corresponding segment of an air-stagnation zone of the leading edge of said airfoil.

95. The system of claim 94, wherein the controller is operative to pulse heating energy from the power source sequentially through the plurality of parting strip segments.

96. The system of claim 95, further comprising:

an energy storage device corresponding to each parting strip segment of the plurality, each energy storage device chargeable from the power source; and

a switching arrangement corresponding to each parting strip segment for pulse discharging the corresponding energy storage device into the corresponding parting strip segment.

97. The system of claim 96, wherein the controller is operative to control the plurality of switching arrangements to sequentially pulse discharge each energy storage device of the plurality into the corresponding parting strip segment.

98. The system of claim 94, further comprising:

a common energy storage device chargeable from the power source; and

a switching arrangement for pulse discharging the common energy storage device into a selected one of the plurality of parting strip segments.

99. The system of claim 98, wherein the controller is operative to control the switching arrangement to pulse discharge the common energy storage device into one of the plurality of parting strip segments selected in accordance with a position of a stagnation line in the air stagnation zone.

100. The system of claim 98 wherein the controller is governed by an angle of attack signal to control the switching arrangement to pulse discharge the common energy storage device into the selected parting strip segment.

101. The system of claim 94, wherein each parting strip segment runs substantially parallel to the span of the leading edge of the airfoil.

102. The system of claim 94, wherein the heater includes an insulation layer bonded to a leading edge facing side of the metal foil of said heater for electrically and thermally isolating the metal foil from the airfoil;

and wherein the plurality of parting strip segments are embedded in the insulation layer.

103. The system of claim 94, wherein the plurality of parting strip segments are disposed on an exposed surface of the metal foil of the heater and are electrically and thermally isolated therefrom.

104. The system of claim 73, further comprising a converter for supplying electrical heating energy to said at least one metal foil heater at a voltage potential higher than a voltage potential of the power source.

105. The system of claim 104, wherein the converter is a DC-DC converter.

106. The system of claim 104, further comprising:

an energy storage device coupled to an output of the converter for storing electrical energy supplied by the converter; and

a switching arrangement coupled between the energy storage device and at least one metal foil heater and operative to discharge stored electrical energy of the energy storage device into the at least one metal foil heater at a predetermined duty-cycle.

107. The system of claim 106, wherein the energy storage device comprises a plurality of series connected ultracapacitors coupled across the source and return lines of the converter.

108. The system of claim 106, including a controller for controlling the switching arrangement to discharge stored electrical energy of the energy storage device into the at least one metal foil heater at the predetermined duty-cycle.

109. The system of claim 104, wherein the converter supplies electrical heating energy to said at least one metal foil heater over source and return lines which are electrically isolated from the power source.

110. The system of claim 109, wherein the source and return lines are connected respectively to one and another ends of the at least one metal foil heater;

and wherein the at least one metal foil heater is coupled at a region close to the return line connection through a conductor to a conductive structure of said airfoil.

111. The system of claim 109, wherein the converter comprises an isolation barrier to protect the power source from electrical energy from a lightning strike at the at least one metal foil heater.

112. The system of claim 109, comprising a parting strip area disposed along an air stagnation zone of the leading edge, wherein the at least one parting strip comprises a multiplicity of differently shaped island areas disposed on the metal foil surface within the parting strip area, each island area being separated from the other island areas by the metal foil surface.

125. The system of claim 73, wherein:

said at least one parting strip comprises a plurality of parting strip segments, each parting strip segment disposed along a corresponding segment of the air-stagnation zone; and

the controller is configured to selectively energize at least one of the parting strip segments based on information reflective of an angle of attack of the airfoil.

79. (canceled)

113. A method of removing ice from an air stagnation zone of a leading edge of an aircraft airfoil comprising:

positioning a metal foil of a metal foil heater having an integral parting strip on the leading edge of the aircraft airfoil such that the metal foil is exposed to the atmosphere, the metal foil being distinct from the parting strip and extending on both sides of the parting strip, in a cross-sectional view of the airfoil;

controlling electrical energy from a power source to the metal foil in accordance with a first pulse duty-cycle; and

controlling power to the integral parting strip so as to maintain said air-stagnation zone virtually free of ice formation.

114. A method of making a metal foil heater for use in ice protection of an airfoil, said method comprising the steps of:

preparing a sheet of titanium foil in a rectangular shape having a length substantially greater than a width thereof for covering at least a portion of a leading edge of said airfoil;

applying a layer of nickel material over an area along each width edge of the titanium foil;

applying a layer of copper material over the nickel layer along each width edge of the titanium foil; and

attaching conductor wires to the copper layers at each width edge.

115. The method of claim 114, wherein the step of applying the layer of nickel material includes the steps of:

plating the layer of nickel material to the titanium foil to a predetermined thickness; and

thereafter, heat treating the titanium foil at a predetermined temperature.

116. The method of claim 114, wherein the titanium foil is heat treated at a temperature close to the melting point of the nickel material.

117. The method of claim 114, wherein the step of applying the layer of nickel material includes the steps of:

electro less plating a first layer of the nickel material to the titanium foil; and

electro plating a top layer of nickel material to the first layer of nickel material.

118. The method of claim 114 wherein the copper material is applied to the nickel layer by soldering.

119. The method of claim 114, wherein the conductor wires are attached to the layers of copper material by soldering.

120. The method of claim 114, including the step of disposing a parting strip integral to the heater along the length of the titanium foil sheet so that said parting strip aligns with an air-stagnation zone of the airfoil.

121. The method of claim 120, wherein the parting strip is disposed over a surface of the titanium foil and electrically and thermally isolated therefrom.

122. The method of claim 114, including the step of bonding an insulating layer to the leading edge facing side of the titanium foil for electrically and thermally isolating the titanium foil from the airfoil.

123. The method of claim 122, wherein the step of bonding includes the steps of:

chemically treating the leading edge facing side of the titanium foil; and

thereafter, bonding the insulating layer to the chemically treated side using an adhesive material.

124. The method of claim 122, including the step of embedding a parting strip in the insulating layer along the length of the titanium foil sheet so that said parting strip aligns with an air-stagnation zone of the airfoil.

126. An electro-thermal ice protection system for an airfoil comprising:

at least one metal foil heater including at least one integral parting strip and a metal foil distinct from said at least one parting strip, said at least one metal foil heater configurable to cover at least a portion of a leading edge of said airfoil with said at least one integral parting strip disposed along an air-stagnation zone of the leading edge and said metal foil being exposed to the atmosphere; and

a controller coupled electrically to said at least one metal foil heater, the controller for controlling electrical energy from a power source to said parting strip of said heater in accordance with a first pulse duty-cycle and also for controlling electrical energy to said metal foil;

wherein;

said at least one parting strip comprises a plurality of parting strip segments, each parting strip segment disposed along a corresponding segment of the air-stagnation zone; and

the controller is configured to selectively energize at least one of the parting strip segments based on information reflective of an angle of attack of the airfoil.

127. The system according to claim 126, wherein the metal foil heater metal foil extending metal foil extends on both sides of the at least one parting strip in a cross-sectional view of the airfoil.

128. The system according to claim 127, wherein the controller is further configured to energize the metal foil of said foil heater in accordance with a second pulse duty cycle.

129. The system according to claim 128, wherein the first pulse duty cycle and the second pulse duty cycle differ from one another.

130. The system according to claim 127, wherein the plurality of parting strip segments are embedded in an insulation layer and electrically isolated from the metal foil.

131. The system according to claim 126, further comprising:

a common energy storage device chargeable from the power source; and

a switching arrangement for pulse discharging the common energy storage device into said at least one of the parting strip segments.

132. The system according to claim 126, wherein the controller selects said at least one of the parting strip segments in accordance with a position of a stagnation line in the air stagnation zone.

133. The system according to claim 126, wherein each parting strip segment runs substantially parallel to the leading edge of the airfoil.