Wind powered generators (RAT) are wildly used in aviation from commercial and military use to crop dusters. They are mainly used as an emergency power, supplying the aircraft with electrical or hydraulic power. The Ram Air Turbine (RAT) generates power from the airstream by ram pressure due to the speed of the aircraft. This powers vital systems such as flight controls or flight critical instruments like navigation and communication instruments.
Me 163 Komet
The first use of the RAT in aviation was on Messerschmitt Me 163 Komet. This was a German rocket powered fighter aircraft and was designed by Alexander Lippisch. This was also the first aircraft of any type to exceed 1000km/h in flight level. The aircraft was made in 1942 at the end of World War 2. From the picture you can see the propeller on the forward fuselage of the Komet this propeller was connected to a generator. This RAT as used to supply the aircraft with electrical power when in flight.
It just wasn’t aircrafts the RAT where fitted too. They were also fitted to some free fall nuclear weapons such as the British Yellow Sun and the Blue Danube. The both of these where designed in late 50s and early 60s. They used a RAT for electrical power, to power radar altimeters and firing circuits.
The Vickers VC10 was the first airliner equipped a RAT on a commercial aircraft. The Vickers VC 10 was introduced in 1962 was fitted with RAT for emergency electrical power to power vital instrumentation. The RAT was hid in the fuselage for aerodynamics. It is deployed manually or automatically when the engines shutdown.
The Concorde also had a RAT. Unlike the Vickerd VC 10 the Concorde RAT is used for hydraulic components. This supplies necessary hydraulic power for control in the event of all four engines failing. Hydraulic pressure is generated by two pumps. One pump to the Green system and the other to Yellow system. The RAT is stored in the port-inner elevon jack fairing.
RATs are also used in agricultural aircrafts. They are used as an auxillary power source for the pump. This is instead of taking power directly from the engine and can be installed as a without modifing the aircrafts mechanical system.
1.1 State of the art
The largest passenger aircraft Airbus A380-800 needs the largest RAT (Ram Air Turbine). This is on the diameter of the propeller blade on the RAT is 1.63 metres (5.3ft). The RAT is stored in the port-inner jack fairing.
WARP fitted to the X-47B
The US Navy’s prototype Northrop Grumman X-47B unmanned aerial refuelling tanker has been fitted with prototype WARP. The X-47B prototype has a standard drop fuel tank under the right wing and wing air refuelling pod (WARP) under its left. The X-47B performed the first autonomous aerial refuelling by an unmanned aircraft using the chute method. The WARP has a RAT fitted to the front of it. This can be seen in the picture above. The RAT is used to power a hydraulic pump to pump the fuel out of the tanks down into the aircraft refuelling.
A company called ATGI has developed Hi-powered Ram air turbine (HiRAT). The HiRate is an internally ducted power system which provides maximum power in a low drag geometry. The output of the HiRAT ranges from 300 watts to over 300kw. Embedded in the pod the turbine has a helical vane like blades.
1.2 Related technology
BEA-14/28 is an Auxiliary Power supply which is designed by Basic Aircraft Products. The BEA-14/28 is used to supply emergency electric power to small aircraft. This manually deployed and is air driven.
BPE-14 Turbo Alternator is made by the same company as the BEA-14/28. The BPE-14 is designed for most classic, antique and home built aircrafts that doesn’t have an electrical system. This is permititly fitted to the outside of the aircraft.
2 Design of the project
As stated in the project brief that some old aircrafts don’t have generators or alternators to supply power in light. After researching for aircrafts that fit the brief, two aircrafts where pick for the design of the aircraft. The first was the Druine D62B Condor and the second aircraft was an Aeronica Champ. As building the aircraft from scratch would take months to build alone so one was downloaded of a website called GrabCAD. Only one CAD drawing was found that looked similar to one of the aircraft picked. The following is the aircrafts Specifications:
Druine D62B Condor Specs Aeronica Model 7 Champ
Length 6.86m Length 6.55m
Wingspan 8.38m Wingspan 10.67m
Empty Weight 417kg Empty Weight 336kg
Gross Weight 670kg Gross Weight 553kg
Max Speed 204km/h Max Speed 153km/h
Cruising Speed 172km/h Cruising speed 137km/h
Stall Speed 74km/h Stall Speed 61km/h
Range 560km Range 485km
Service Ceiling 3,650m Service Ceiling 3,800m
Climb Rate 3.1m/s Climb Rate 1.9m/s
This following is the CAD aircraft that was chosen to design the wind air turbine for. The reason why this aircraft was pick was because it has a similar design to the Druine D62B Condor. It is important that the CAD aircraft has a similar design to the Druine Condor as the aircraft will be imported into a CFD software. The CFD software will help to analyse the design of the aircraft and help find the optimum location to position the wind air generator that produces the least amount of drag but produces the most amount of power.
2.2 Design for the RAT
The design of the wind powered generator (RAT) has to as aerodynamic as possible, produce sufficient power and doesn’t affect the aircrafts performance. There are multiple designs for wind powered generators (RAT) already in use today. After researching several designs, most designs were found unsuitable for two reasons. Firstly the out ruled designs result in serious modifications being carried out on the aircraft. These designs are therefore not cost effective. The remaining out ruled designs are used to for auxiliary power not for the main source of power.
The inspiration for the design of the wind powered generator was the design of modern gas turbine engine. There are numerous reasons why this component was used as inspiration. Firstly the gas turbine engine is aerodynamic and an efficient design. Designing the generator like an engine would give protection from the spinning blades and an aerodynamic design to store the generator in. Finally the gas turbine hangs off the wing in the freestream airflow. The wind generator will need to be located in the freestream airflow to extract the kinetic energy from the airflow.
2.3 Blade Design
The blades for the wind power generator is going to look like the turbine blades in a gas turbine engine. The blades in the gas turbine engine have shrouded blades and therefor have no tip loss. This design on of the blades would be increase the efficiently of the blade design. The blades are going to be taking the kinetic energy out of the oncoming. This means the blades are going to be bucket shaped blades to with a twist out towards the tip. Below is a gas turbine blade. During researching blades I came across a software called Qblade. After searching GrabCAD for blades similar design to the blades below. Only two or three matched the blades below. After picking one of the three blades to use it was edited in Qblade to match the design.
CAD Turbine Blades
2.4 Generator/ Alternator
After designing the wind power generator next was wither to use a generator or to use an alternator. The difference between a generator and an alternator is how the current is created. In a generator creates electricity by moving a wire (armature) within a magnetic field. Depending on the speed of the armature depends on the amount of electric produced. In an alternator the magnetic field spins in series of a winding called a stator. The opposite to what happens in a generator. Alternators use a more efficient mothed. Much smoother electrical output produced by the alternator. Construction of the alternator allows for the windings to be directly wired to their output pins.
Before picking which one that would suit the RAT best, it was decide what basic instruments need to powered. The instrument chosen was GPS, Transponder Mode S and a Radio. The total power need to power all these was 20A at 14.4V. The following is the breakdown of the current.
Transponder (mode S)
Total of Components
To charge battery
After working out what power need to charge a battery and to power the components. But before picking a generator or alternator, the designed blade need to be tested to see what the blade most efficient RPM is and to determine what RPM the blade can reach itself. The result of this may cause the generator/ alternator to be geared up or down to allow the RPM of the generator/ alternator to run at its most efficient state.
A CAD software had to be used to help design and build the wind powered generator. There was a two different CAD (Computer Aided Design) software available in the college. The first one was a software called Soildworks and the second one was a software called Catia. Both of the software’s where compatible with CFD software in the college. After weighing up the pros and cons of both, the software picked was Soildworks. There was a few reason for the picking Soildworks over Catia. Firstly Soildworks was a more user friendly software then Catia. Secondly Soildworks has a rendering tool which takes pictures of the finished product and produces real life pictures. The finial reason for picking Soildworks over the Catia was a personal preference. Previous experiences of using Soildwork software can reduces the time spent on designing the wind power generator and allows more time to constraint on the CFD software.
Used in Aviation industry Never used Software
More accurate when moving into CFD Not familiar with its capability’s
Not user friendly
Past experience with software. Not as accurate as Catia converting to CFD
Familiar with its capability’s
Able to render pictures for report
ANSYS is analysis software that is used across different disciplines. The software is capable of FEA (Finite Element Analysis), structural analysis, explicit and implicit methods, heat transfer and computational fluid dynamics (CFD). The only disciplines that is need for this project is Computational fluid dynamic. CFD has two options CFX and Fluent. Both are use numerical analysis and data structurer to solve problems that involve fluid flows. This software will simulate an air flow around the CAD aircraft like the aircraft was in a wind tunnel. When the wind powered generator design is completed using Soildworks the generator will be imported into ANSYS to run a CFD analysis. This will help to determine if the wind generator is well designed and to see how much drag is produced from the design. As I have no past experience with this software there are going to a lot of reaching and trial and error to complete the analysis for each part.
QBlade is an open source software that aids in designing wind turbine blades by using wind turbine calculation software. The software purpose is to help design and provide an aerodynamic simulation of the turbine blade. Qblade is a user friendly software that will be grate benefit in designing the turbine blade for the wind power generator. This software allows previous designs CAD blades to be upload to the software and edited. This software will help aid the design of my blade
3 Manufacture of the project
3.1 Wind turbine Design
After researching different designs of gas turbine engines and determineing the size of the RAT. When researching and picking the finished the next step was to start to build the design on Soildworks. During the build the design was split up into three parts the first part was the generator/alternator holder. This part is the storage place for the generator/alternator. The purpose of this part is to make the inside of the RAT as aerodynamic as possible as well as protecting the generator as it will be in the outside environment. This part will have struts in the shape of blades. This will help it connect to the cover. One of the blades will be drilled the hold way to the middle for the generators/ alternators wires to exit on it
Picture of holder
The second part is the cover of the cover the blade and the generator/alternator holder. From the outside it looks like the outside of the gas turbine engine. The goal of the cover was to be aerodynamic and to produce as little of drag as possible. There was a two different designs for the cover made in Soildworks. The reason for this was designing two was because the outcome was unknown until CFD was completed on the generator. For example one of the designs could produce less drag then the other but produces less power. This was done to save time so there was no need to come back and design another one.
Picture of cover 1
Picture of cover 2
The finial part is a cap for the back of the generator/alternator holder this allows access to the generator/alternator to allow for replacements or repairs. This is a cap is able to be removed to do the repairs.
When all the parts where made they were put together in assembly the picture below is the three parts together.
3.2 Blade Design
After finding the blade that fitted the design, the next step was to import it into Soildworks. When the blade was in Soilworks, there was a bit of modifications had to be made to the cover and generator/alternator holder. The modifications was that the diameter of the cover had to be made greater to allow for the blades to rotate without striking the cover. As the diameter of the cover was widened the struts on the generator/alternator holder had to be made long to fit to the new design. When the modifications was completed the blade was added to the final design. The picture below is the entire RAT assembled together.
Finial Assembly with Blade
After this the blade was imported into Qblade for an analysis to find out what the how much power can be produced by the blades.