Aircraft Engine Nacelle Strake

 

Engine nacelle strake is vortex generator which enhance aerodynamic performance of an aircraft. It is mounted on engine nacelle. Encircled part in this picture is engine nacelle strake.Many aircraft engine have strake only one side and that will be on inboard of nacelle but few aircraft have strake on both the sides.

Fig 01 Engine Nacelle Strake 

Fig 02 Strake View from Cabin

The purpose of nacelle strake is to generate vortex which energize the low energy airflow over the wing when aircraft operating at high angle of attack and low speed condition such as takeoff and landing phase of flight.

We have seen many modern aircraft have their engine mounted beneath of wing and inlet of engine nacelle  forward of wing leading edge. There are many advantages of installing engine below the wing but there are some disadvantage and one of the disadvantages is engine nacelle /wing assembly interaction which disturb the airflow over the wing and it affect the lift production capability of wing.Although this nacelle/wing assembly is designed such a way that in cruise phase of flight,  the airflow around the nacelle causes little disturbance of the airflow over the adjacent wing

To use short length runway for takeoff and landing aircraft has to have low speed. To keep aircraft speed low, aircraft has to produce more lift.  With the help of flap, slat and aircraft at high angle of attack wing can generate more lift but there is possibility of stalling of aircraft. If aircraft stalled, airflow separate from wing surface. As we know if aircraft fly beyond permitted angle of attack stall will occur. If we can delay separation of airflow from wing , this will allow us to operate aircraft beyond permitted angle of attack and the lift which we get from wing will also increase.  

Aircraft which have higher stalling angle of attack, aircraft will require low speed for takeoff and landing.

As we know the disadvantage of placing engine beneath of wing is interaction of nacelle wing assembly which disturb airflow over the adjacent wing and this has more intense effect when aircraft flying at high angle of attack. As engine nacelle placed beneath and forward of wing so when aircraft flying at high angle of attack,  nacelle will be at higher angle which will disturb more airflow over the wing  and this undesirable effect reduces lift which can be avoided if we don’t install engine on wing.

To overcome the undesirable interaction effect of the nacelle/wing assembly manufacture installed Strake or vortex generator on nacelle of an engine. This strake or vortex generator produces downwash field or vortex which flows over the wing leading edge. This downwash field energies low energy airflow  over the wing which in turn delay the separation of airflow at wing trailing edge. This delay in separation of airflow permit wing to generate more lift. 

 Fig 03 Vortex Generated by Strake

So basically, strake improve the performance of nacelle/wing assemblies at high angle of attack operation such as the time of takeoff and landing.

 

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