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where is the heat capacity ratio / of the gas and where is the total (stagnation) upstream pressure. For air with a heat capacity ratio =, then =; other gases have in the range 1.09 (e.g. butane) to 1.67 (monatomic gases), so the critical pressure ratio varies in the range < / <, which means that, depending on the gas, choked flow usually ...
Compressor characteristic is a mathematical curve that shows the behaviour of a fluid going through a dynamic compressor.It shows changes in fluid pressure, temperature, entropy, flow rate etc.) with the compressor operating at different speeds.
A low pressure ratio fan (such as that used on a high bypass ratio turbofan) has a range of working lines. At high flight speeds, the ram pressure ratio factors up the cold nozzle pressure ratio, causing the nozzle to choke. Above the choking condition, the working lines tend to coalesce into a unique steep straight line.
As the pressure is reduced still further, a pressure is reached that result in M = 1 at the throat with subsonic flow throughout the remainder of the nozzle. There is another receiver pressure substantially below that of curve C that also results in isentropic flow throughout the nozzle, represented by curve D; after the throat the flow is ...
The pressure ratios for the design flow rate at the intake and outlet are = / and = /, and the off-design ratios are = / and = /. If the speed of sound is reached in a stage, the group of stages can be analyzed until that stage, which is the last in the group, with the remaining stages forming another group of analysis.
Typical primary nozzle map. The following discussion relates to the expansion system of a 2 spool, high bypass ratio, unmixed, turbofan. On the RHS is a typical primary (i.e. hot) nozzle map (or characteristic). Its appearance is similar to that of a turbine map, but it lacks any (rotational) speed l
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For example, the Mach number evolution of an ideal gas in a supersonic nozzle depends only on the heat capacity ratio (namely on the fluid) and on the exhaust-to-stagnation pressure ratio. [6] Considering real-gas effects, instead, even fixing the fluid and the pressure ratio, different total states yield different Mach profiles. [17]