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Status
Electronic Resource
Call number
Publication
1019; Report; August 1980.
Language
Library's review
ABSTRACT:
In order to be economically viable, distributed point focus air Brayton systems will require highly effective recuperators. The use of recuperators with effectiveness of . 9 can reduce the energy required to run the Brayton engine by a factor of • two or more. This translates into a
Metal recuperators can be designed to provide high effectiveness. These devices, however, seriously reduce the mean-time-between failures for the Brayton systems because the thermal stresses experienced by the recuperator exceed the creep stress of the metals used in the construction. After a limited number of cycles the stress induced distortion leads to metal fatigue and failure. Sanders has proposed a Brayton conversion system where the recuperator is replaced by a pair of thermal storage modules (TSM's) and associated valving, which act as a regenerator. By operating these TSM 'sat low air velocities, a sharp temperature gradient (thermocline) can be propagated through the ceramic. The use of this thermocline mode of operation allows the design of a recuperator system with an effectiveness over .9 and with very low
pressure drops. An air cycle Brayton system using these TSM's as valved regenerators will have a thermal-to-mechanical conversion efficiency of 40%. The goals of this program were to demonstrate the thermocline propagation in the TSM's, to measure the steepness of the thermocline, and to measure the effectiveness of the TSM's when used in a Brayton system. In addition, a high temperature valve
suitable for switching the TSM at temperatures to 1700°F was to be designed, built and tested.
In order to be economically viable, distributed point focus air Brayton systems will require highly effective recuperators. The use of recuperators with effectiveness of . 9 can reduce the energy required to run the Brayton engine by a factor of • two or more. This translates into a
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substantial cost reduction when the reduced size of the parabolic dish, receiver and tracking and support mechanism are taken into account.Metal recuperators can be designed to provide high effectiveness. These devices, however, seriously reduce the mean-time-between failures for the Brayton systems because the thermal stresses experienced by the recuperator exceed the creep stress of the metals used in the construction. After a limited number of cycles the stress induced distortion leads to metal fatigue and failure. Sanders has proposed a Brayton conversion system where the recuperator is replaced by a pair of thermal storage modules (TSM's) and associated valving, which act as a regenerator. By operating these TSM 'sat low air velocities, a sharp temperature gradient (thermocline) can be propagated through the ceramic. The use of this thermocline mode of operation allows the design of a recuperator system with an effectiveness over .9 and with very low
pressure drops. An air cycle Brayton system using these TSM's as valved regenerators will have a thermal-to-mechanical conversion efficiency of 40%. The goals of this program were to demonstrate the thermocline propagation in the TSM's, to measure the steepness of the thermocline, and to measure the effectiveness of the TSM's when used in a Brayton system. In addition, a high temperature valve
suitable for switching the TSM at temperatures to 1700°F was to be designed, built and tested.
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