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This study aims to investigate the effects of exhaust direction on exhaust plume and helicopter infrared radiation in hover and cruise status.

Four exhaust modes are concerned, and the external flow field and fuselage temperature field are calculated by numerical simulation. The infrared radiation intensity distributions of the four models in hovering and cruising states are computed by the ray-tracing method.

Under the hover status, the exhaust plume is deflected to flow downward after it exhausts from the nozzle exit, upon the impact of the main-rotor downwash. Besides, the exhaust plume shows a “swirling” movement following the main-rotor rotational direction. The forward-flight flow helps prevent the hot exhaust plume from a collision with the helicopter fuselage generally for the cruise status. In general, the oblique-upward exhaust mode provides moderate infrared radiation intensities in all of the viewing directions, either under the hover or the cruise status. Compared with the hover status, the infrared radiation intensity distribution alters somewhat in cruise.

Illustrating the influences of exhaust direction on plume flow and helicopter infrared radiation and the differences of helicopter infrared radiation under hover and cruise statuses are identified. Finally, an appropriate exhaust mode is proposed to provide a better IR signature distribution.

The cities, for the most part, appeared up until the middle of the 1990s to be islands within the larger Chinese political economy in which job-secure workers could be certain that their livelihood, health, education, and living abodes would evermore undergird their and their children's sustenance. At least until the late 1980s, urbanites who stuck with the state sector even considered good treatment on the job a kind of birthright, an entitlement that was sure to be enforced. In the cities, true, there had always been the disadvantaged after 1949 – those without offspring or spouses, the disabled, and people unable to support themselves. But this relatively tiny batch of individuals generally survived in the shadows and out of sight, subsisting – but just barely – as members of the “three withouts” on a mere pittance, in the form of meager “social relief” disbursed by civil affairs departments.⁸