MATERIAL TEMPERATURE LIMITS AND CONVECTION FLOW REQUIREMENTS

摘要

Material temperature limits (MTL) influence the convection flow required to cool the surfaces of HPT parts. The goal of designing minimum-cooling-flow parts is pursued by stating two hypotheses. The 'Minimum Cooling Hypothesis' is that cooling flow is minimized by operating surface points at the material temperature limits (MTL). The 'Isothermal Hypothesis' states that for spatially uniform materials, the cooling flow is minimized if the limiting material interfaces are isothermal. Demand for convection cooling is measured using a new grouping called the convection flow parameter and theory, covering a variety of material design spaces, is presented to show how the film, metal and coating temperatures each contribute to the convection flow through and cooling technology effectivenesses.An example of film decay over turbulent flat plate demonstrates the stated MTL method satisfies the minimum cooling hypothesis and approaches the second hypothesis of isothermal interface surfaces over a large portion of the cooled surface. This condition of isothermal interfaces is a cornerstone of prior studies by the author on the iceformation design method dating back to 1983. With analogous iceformation geometries solved, their implementation in gas turbines depends on the designer's ability to determine cooling distributions that provide isothermal material interfaces.