Hot Gas Ingestion, or HGI, is a phenomenon where the engine exhaust gases are re-ingested into the engine air inlet.
Causes
HGI is a common phenomenon that occurs when helicopters hover with a tail wind or during sideways or rearwards flight.
Consequences
HGI causes increased engine inlet gas temperatures and potential flow/temperature distortion. Assuming an engine is operating at its maximum rated temperature, an inlet temperature rise of 40°F due to HGI can cause approx 15 percent power loss. In addition, spatial or temporal temperature distortion can cause compressor stall, which in turn may lead to abrupt and catastrophic power loss.
The Solution
With the Centrisep® Engine Advanced Protection System (EAPS), the ingested hot gas is quickly and uniformly redistributed by the swirling process inside the vortex tubes, resulting in uniform, stable air flow into the engine intake. By reducing flow and temperature distortion, this minimizes any detrimental effects of HGI and hence significantly alleviates compressor stall problems.
Computational Fluid Dynamics (CFD) illustrations
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Figure 1
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Figure 2
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20mm from the engine air inlet, a pocket of hot gas forms.
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Figure 3 - Without a Centrisep EAPS at the compressor entry plane, this gas pocket creates temperature distortion, with all its associated effects.
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Figure 4 - With a Centrisep EAPS, the hot gas mixes with fresh air resulting in an even temperature distribution at compressor entry plane.
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