Coolable rotor blade for an industrial gas turbine engine

A coolable rotor blade for an industrial gas turbine engine having a rotor assembly, the coolable rotor blade having an exterior, which comprises:

• a root which adapts the rotor blade to engage a portion of the rotor assembly, the root having
• a chordwise extending root wall,
• a first cooling air duct which adapts the blade to be in fluid communication with a source of cooling air, the first cooling air duct having a first plenum, a first cross-sectional flow area upstream of the first plenum and a second cross-sectional flow area for the first plenum which is greater than the first cross-sectional flow area, and
• a second cooling air duct which adapts the blade to be in fluid communication with a source of cooling air;
• the second cooling air duct having a second plenum, a first cross-sectional flow area upstream of the second plenum and a second cross-sectional flow area for the second plenum which is greater than the first cross-sectional flow area;
• an airfoil having a spanwise length S, having a front serpentine passage, having a rear serpentine passage, and having ribs which extend spanwise from the suction sidewall to the pressure sidewall to form spanwise airfoil structures which chordwise bound the passages, each serpentine passage having three legs which extend spanwise and which are bounded by the ribs, the airfoil having
• a leading edge, a leading edge region, and a trailing edge and a trailing edge region spaced spanwise from the leading edge region,
• a midchord region which extends chordwise and spanwise between the leading edge region and the trailing edge region,
• a suction sidewall and a pressure sidewall, the pressure sidewall being joined to the suction sidewall to form spanwise airfoil structure which chordwise bound an adjacent passage, the spanwise airfoil structure including a leading edge wall at the leading edge region and a trailing edge wall at the trailing edge region, the pressure sidewall being spaced from the suction sidewall between the leading edge and trailing edge walls to form a cavity therebetween for receiving cooling air,
• a tip region having a tip wall which extends in a chordwise direction between the suction sidewall and the pressure sidewall,
• a first rib which extends in the spanwise direction in the midchord region to the tip wall to divide the cavity into a front portion and a rear portion,
• the front portion having
• a second rib which extends from the root wall to the tip wall and is spaced from the leading edge leaving a first leading edge passage having a single leg therebetween which is in flow communication with the first cooling air duct,
• a third rib which extends from the root wall, which is spaced chordwise from the first rib leaving the first leg of the front serpentine passage therebetween, which bounds the second leg, and which is spaced spanwise from the tip wall leaving a first turn region therebetween which connects the first leg to the second leg, and
• a fourth rib which extends spanwise from the tip wall, which is spaced chordwise from the third rib to bound the second leg, which is spaced chordwise from the second rib to leave the third leg therebetween and is spaced spanwise from the root wall leaving a second turn region therebetween for the front serpentine passage;
• the rear portion having
• a fifth rib which extends from the root wall, which is spaced chordwise from the first rib leaving the first leg of the rear serpentine passage therebetween, which bounds the second leg, and which is spaced spanwise from the tip wall leaving a first turn region therebetween which connects the first leg to the second leg for the rear serpentine passage, and
• a sixth rib which extends spanwise from the tip wall, which is spaced chordwise from the fifth rib to bound the second leg, which is spaced chordwise from the trailing edge rib leave the third leg therebetween and which is spaced spanwise from the root wall leaving a second turn region therebetween for the rear serpentine passage;
• wherein the first cooling air duct is in flow communication with the front portion of the cooling air cavity for supplying cooling air to the leading edge passage and the front serpentine passage, the second cooling air duct is in flow communication with the rear portion of the cooling air cavity for supplying cooling air to the rear serpentine passage and wherein the associated plenum of each cooling air duct is adjacent the cavity and has an increase in average cross-sectional area as compared to the first average cross-sectional area upstream of the plenum which is adapted to reduce the velocity of the cooling air under operative conditions to increase the static pressure of the cooling air and reduces flow losses in the duct;
• wherein the front serpentine passage, the rear serpentine passage and the third leading edge passage each have an exhaust opening which extends through the tip region of the airfoil to the exterior of the airfoil to place the end of the passage in flow communication with the exterior of the airfoil and wherein the trailing edge wall has a plurality of cooling holes which extend in a generally chordwise direction through the trailing edge wall to place the third leg of the rear passage in flow communication with the exterior of the airfoil;
• wherein the front serpentine passage, the rear serpentine passage and the third leading edge passage each have at least one array of trip strips on the suction sidewall and at least one array of trip strips on the pressure sidewall to form at least two arrays of trip strips for each passage, the trip strips of each sidewall being spaced spanwise one from the other with a pitch and spaced spanwise from the trip strips on the other wall, each trip strip having a height measured from the adjacent portion of the sidewall and a trip strip height to pitch ratio and each trip strip forming an acute angle on the upstream side with the spanwise airfoil structure that bounds the serpentine passage;
• wherein the third passage disposed between the leading edge and the third leg of the forward most serpentine passage has a first portion adjacent to the root and a second portion adjacent to the tip and having a trip strip height and trip strip height to pitch ratio which is greater than that of the first portion and wherein each trip strip forms an acute angle on the upstream side of the trip strip with the first rib for driving a portion of cooling air flow toward the forwardmost first rib under operative conditions;
• wherein the arrays of trip strips in the legs of the front serpentine passage and the rear serpentine passage form an acute angle on the upstream side of the trip strip with the spanwise airfoil structure bounding the passage which is closest to the associated edge region to drive a portion of cooling air flow toward such structure which is closest to the associated edge of the airfoil under operative conditions;
• wherein the arrays of trip strips in the legs of the front serpentine passage and the rear serpentine passage that are disposed in the first leg and the second leg each have no increase in the trip strip height and trip strip height to pitch ratio for the associated leg and over the entire leg which increases the ease of inspection and fabrication during manufacture of the airfoil;
• wherein the front serpentine passage and the rear serpentine passage in the third leg of each passage have trip strips with both a trip strip height and trip strip height to pitch ratio over at least a portion of the third leg which is greater than that of the second leg to provide a greater increase in heat transfer effectiveness of the third leg over the second leg than exists between the second leg and the first leg as the flow of cooling air proceeds in the downstream direction;
• wherein the front serpentine passage and the rear serpentine passage in the third leg of each passage have a first portion which receives cooling air from the second leg and a second portion outwardly of the first portion, and wherein the arrays of the trip strips for the third leg which are disposed in the second portion have a trip strip height and a trip strip height to pitch ratio which is greater than that of the associated array in the first portion and greater than that of the corresponding array in the second leg and wherein the arrays of trip strips in the second leg have a trip strip characteristic selected from the group consisting of trip strip height or trip strip height to pitch ratio which is greater than that of the corresponding trip strip characteristic of the first leg to sequentially increase the heat transfer effectiveness of the second and third legs in the downstream direction.