The corresponding angle is known as a Mach angle and the lines enclosing the disturbed region are known as Mach lines (in 2-D case) or Mach cone (in 3-D). t), the disturbances originating from point A travel a distance c.The first Mach line is at an angle μ 1 = arcsin ( 1 M 1 ) ) as it moves from point A to B (distance u The expansion fan consists of an infinite number of expansion waves or Mach lines. The theory was described by Theodor Meyer on his thesis dissertation in 1908, along with his advisor Ludwig Prandtl, who had already discussed the problem a year before. Axial flow In an axial flow compressor, air is compressed while continuing its original direction of flow. modular design construction can be adjusted optimally to meet customer-specific requirements depending on the steam mass flow and compression ratio. the total pressure and total temperature) remain constant across the fan. The difference between them is the way that the air flows through the compressor. Since the process is isentropic, the stagnation properties (e.g. When you compress the air, it becomes denser and hotter. Because the flow is isentropic, it is also reversible (i.e., if the direction of the flow is reversed then the fluid is isentropicaly compressed). I want to understand the physics behind this completely. Figure 15.8(c) shows a typical expansion over a continuous convex turn. This can lead to temperatures of minus 7 degrees Celsius. Īcross the expansion fan, the flow accelerates (velocity increases) and the Mach number increases, while the static pressure, temperature and density decrease. The machine works by compressing air, cooling the compressed air, and then rapidly expanding it. It is physically impossible for the flow to turn through a single "shock" wave because this would violate the second law of thermodynamics. When a flow turns around a smooth and circular corner, these waves can be extended backwards to meet at a point.Įach wave in the expansion fan turns the flow gradually (in small steps). The fan consists of an infinite number of Mach waves, diverging from a sharp corner. The figure shows one such ideal expansion fan.Ī supersonic expansion fan, technically known as Prandtl–Meyer expansion fan, a two-dimensional simple wave, is a centered expansion process that occurs when a supersonic flow turns around a convex corner. When a supersonic flow encounters a convex corner, it forms an expansion fan, which consists of an infinite number of expansion waves centred at the corner.
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