UAV EnginesBy: Nathaniel Crisler1, Onyewuchi Ebere2, Mahmoud Farhat 3, Natalie Marini 4, Janet

Massengale5, Kenneth McCloud6

Unmanned Aerial Vehicle

► Commercial Applications:

Firefighting Oil and gas industry Agriculture Motion picture filming Journalism

► Military applications:

Surveillance Reconnaissance Striking Search and rescue Targets for training

Common types

UAV type Engine Type Power Range (HP)

Micro Electrical 1

Mini Piston (2x2), Electrical 1-20

Tactical, Close range (75%) Rotary (Wankel) 20-90

MALE “medium alt. longend.” (15%)

Piston (4x4), Rotary 90-250

MALE Turbo-prop, turbo-jet >250

* Almost 90% of UAV engines requires power outputs from 20-250 hp

Requirements

1. Long endurance - mission length of 20-50 hours

2. Compactness-High power/weight ratio, low volume.

3. Simple maintainability -Robustness, lower skills ground crews

“The Wankel engine”

►A type of Internal Combustion Engine that uses a rotary design.

►Uses Four strokes cycle (Otto cycle).

►Developed in 1951 by Felix Wankel.

Rotary Design

► 4 stroke engine (intake, compression, combustion, exhaust)

► Rotor on eccentric shaft.► Design to Minimize Volume

while Maximizing Compression ratio.

► Rotor – Triangular shaped with equaled width.

Pros

►Much simpler comparing to its piston counterpart.

► Power to weight ratio is superior than piston engines.

► Smooth power flow and high RPM.

► Less mechanical losses

Con

► Sealing, leaks from the apex seals greatly reduces efficiency of the engine.

► Poor emissions, unburntfuel is in the exhaust stream. Due to port overlap

► Low fuel efficiency and shorter engine life due to damaged seals.

Performance Indicators

► Power to Weight Ratio► Fuel Type► SFC – specific fuel consumption

► BMEP – brake mean effective pressure►Engine’s capacity to do work independent of engine size

Engine Comparison

EngineDisplacement(cc)

Maxpower(hp)

Maxtorque(lb-ft) BMEP (psi)

SFC(lb/HP/HR) Fuel

Weight(lbs) Cooling

300LCR 300 32 24.32 200.40 0.527 gas/avgas 26.2 liquid

300HFE 300 31 22.6 186.23 0.58 jp5/jp8/jet a1 27.1 liquid

600LCR 600 58 43.55 179.43 0.61 gas/avgas 46.7 liquid

600HFE 600 56 42 173.05 0.67 jp5/jp8/jet a1 46.7 liquid

AR731 208 38 26 154.50 0.57 avgas 21.7 air

• Rotron 300LCR chosen as best performing engine due to the BMEP and low SFC

• An engine must first provide the power needed for a specific application. Then BMEP and SFC are evaluated.

Enhancing Performance

Increasing the fuel efficiency► Problem: Poor sealing between

the rotor and the chamber walls due to thermal expansion of engine block

► The engine block is constantly being heated where combustion is occurring and constantly being cooled near the intake

► Solution: design an exotic alloy or ceramic engine block that is more resistant to thermal expansion

► Result: increased torque and decreased SFC (for constant )

Enhancing Performance

Increasing the fuel efficiency► Problem: High wear on the

inner wall of the engine block and poor sealing between rotor and chamber walls

► Solution: Use special cast iron apex seals

► Cast Iron is self-lubricating, reducing the amount of lubricating oil needed in the system

► Result: increased torque, decreased SFC, less emissions from burnt oil

Increasing the fuel efficiency► Problem: High wear on the

inner wall of the engine block and poor sealing between rotor and chamber walls

► Solution: Use special cast iron apex seals

► Cast Iron is self-lubricating, reducing the amount of lubricating oil needed in the system

► Result: increased torque, decreased SFC, less emissions from burnt oil

Increasing the fuel efficiency► Problem: High wear on the

inner wall of the engine block and poor sealing between rotor and chamber walls

► Solution: Use special cast iron apex seals

► Cast Iron is self-lubricating, reducing the amount of lubricating oil needed in the system

► Result: increased torque, decreased SFC, less emissions from burnt oil

Enhancing Performance

Increasing the fuel efficiency► Problem: Incomplete burning

of fuel, large HC emissions► Solution: use fuel injectors to

control amount and timing of fuel supply

► Stratification techniques will increase the burning of fuel and decrease emissions

► Result: increased torque, decreased SFC, less emissions from unburnt fuel

Partial Direct Injection: Lean mixtureprovided by carburetor, rich mixture injected near spark plug

Rotor Vs Piston

13B 1.3 Liters (146 hp @ 6500 rpm and 138 ft·lbf )

KA24DE 2.4 Liters (155 hp @ 5600 rpm and 160 ft·lbf)

Mazda Rx-7 (1989-1992) Nissan 240sx (1991-1994)

QUESTIONS

References► Nice, Karim. “How Rotary Engines Work”. http://auto.howstuffworks.com/rotary-

engine2.htm

► Karunakaran, K.P. "Application of Wankel Engine in Aircrafts and Ways of Increasing Its Fuel Efficiency.“

► "Rotary Engines for UAV Applications." Advanced Rotary Engine Technology. Rotron. Web. 1 Apr. 2015. <http://www.rotronuav.com/>.