An investigation into potential fuel savings for 110–130 seat passenger transport aircraft due to the incorporation of natural laminar flow or hybrid laminar flow control on the engine nacelles

Abstract

A computer program, capable of accurately determining the required fuel for a given mission profile, has been developed for two ‘project’ aircraft types. The program was initially validated against reference aircraft and then modified to study the potential impact on trip fuel due to the incorporation of natural laminar flow or hybrid laminar flow control on the engine nacelles, by implementing changes the aircraft’s drag coefficient ( CD), specific fuel consumption and operating empty weight. Trade studies, with changes to CD, specific fuel consumption and operating empty weight, were conducted using trip fuel as the objective function. The results can be superimposed, permitting estimates of the trip fuel reduction due to the incorporation of alternative drag reduction designs. The impact of trip distance on the fuel-saving potential of laminar flow technologies has also been explored. The potential fuel savings for the aircraft fleet (with the incorporation of hybrid laminar flow control or natural laminar flow) has been estimated using an aircraft utilisation model (representing the probability of the aircraft flying a given stage length). It was concluded that there would be a net fuel saving based on the utilisation model. Finally, to obtain a realistic assessment of the potential benefit of these technologies, the probable time-in-cloud, which will result in a loss of laminar flow, has been considered.

Aspects of aero-engine nacelle drag

“…22 For example, an analysis of natural laminar flow (NLF) nacelles, with transition at 40% chord, used to power a twinengine aircraft with a 2000 nm mission demonstrated potential fuel burn reductions of 1.7%. 23 Historically, the principal method to assess the drag of a nacelle has been through wind tunnel testing. For civil aero-engine configurations, this has typically been performed using a sting mounted nacelle with a suck down configuration to enable that the effects of MFCR, freestream Mach number and incidence on the nacelle drag to be measured.…”

“…22 For example, an analysis of natural laminar flow (NLF) nacelles, with transition at 40% chord, used to power a twin-engine aircraft with a 2000 nm mission demonstrated potential fuel burn reductions of 1.7%. 23…”