Weather Resistance and Bleed Air Control for the Diverterless Supersonic InletIAN ZABEL

ME 547 – TRANSFER / RATE PROCESS

The Supersonic Inlet Diverter

Function◦ Redirect the boundary layer◦ Ensure even pressure distribution

Consequences◦ Increase in inlet drag◦ Complex structure and bleed system◦ Significant radar reflection

Types◦ Ramp inlet bleed system (F-15, Tu-144)◦ Formed Inlet Diverter (F-16)◦ Combinations of Both

The Diverterless Supersonic Inlet (DSI)

Function◦ Divert the boundary layer through obstruction◦ Prevent radar reflection and signal dispersion

Benefits◦ Low radar cross section (RCS)◦ Structurally simple◦ No critical need for bleed systems

Downsides◦ Potentially reduced pressure recovery◦ Optimal within small speed ranges (transonic)◦ Complicated design optimization (lots of testing)◦ Poor / no weather resistance

Bleed Systems Function Purpose

◦ Mass flow rate control◦ Cabin air quality (Passenger aircraft)◦ Cooling of internal systems◦ Shockwave Control

Location◦ After compressor – passenger aircraft◦ Before compressor – Supersonic aircraft◦ Damaged compressor blades/stators

Current Problems◦ Mechanically complex◦ Bypass airflow wasted

Ice Buildup Cause and Prevention

Occurrences◦ High altitude, convective weather◦ ~100 engine power loss events since 1990◦ Supercooled water and ice crystals

Power Loss◦ Ice entering compressor (no flow)◦ Ice entering combustor (no fuel ignition)◦ Damaged compressor blades/stators

Current Mitigation◦ Electrical heating – power draw and thin metal◦ Vibration – mechanically complex if forced◦ Avoiding the weather – restricted operation

Using Deicer Deicer

◦ Alcohol, Salt, Glycols◦ Used to modify the freezing point◦ Similar to methods used on roads

Benefits◦ No system necessary on the aircraft◦ No power draw on the aircraft

Issues◦ Requires airport resources◦ Time intensive◦ Unusable during flight

The ‘Weeping Wing’ Concept Porous Internal / External Surface

◦ Hole size increases along the diffuser◦ Deicing chemical pumped through small holes◦ Flows down internal surface into large holes

Benefits◦ Prevention of ice formation◦ Bleed system addition potential

Downsides◦ Deicing chemicals potentially on blades◦ Limited use, activated by pilot / sensors◦ Potential boundary layer separation

System Combination Perforated Internal Surface

◦ Acts as bleed system◦ Mechanically simple◦ Shock location control

Moisture and Ice Control◦ Less surface area for ice crystals◦ Potential for using condenser◦ For subsonic, active prevention needed◦ For supersonic, no concern due to shock◦ Used in combination with ‘weeping wing’◦ Expose salt or alcohols to ice to remove

Conclusion Combined System

◦ DSI doesn’t need significant bleed system, but…◦ Slight mass flow rate control improves efficiency◦ Ice control where and when needed

Implications◦ Broadened operational scope◦ Reduced cold weather maintenance◦ Increased aircraft capability◦ Minimal change in RCS

Final Result◦ Significantly improved cold weather resistance

Questions?