| 摘要 |
A typical impeller wheel compressor has a limitation relating to the maximum delivery pressure, cf. the fact that the temperature of the output gas after an isentropic compression becomes high, even at a moderate pressure. The internal parts of an impeller compressor have to resist said temperature. 1. By returning and cooling part of the high pressure delivery mass flow, and by returning the mass flow to the expansion side of the rotor, or 2. by injecting relatively cold gas into the expansion side of the rotor, the temperature can be further lowered at the subsequent expansion. The returned or injected mass flow is mixed with a mass flow from the inlet, whereby the temperature of the mixture will be lower than the temperature of the inlet gas. Hereby, the impeller wheel compressor may reach a higher delivery pressure at the same delivery temperature. <IMAGE>
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