We have since a few weeks back been working on our new rotations, this time I am working in a workshop called Rotatives where rotating components for jet engines are manufactured. Working within Aerospace you normally face really tough tolerances as it is very important to manufacture correct and safe products. When manufacturing rotating parts, it is even tougher. During my time at the department I’ve realized how incredibly cool it is to be able to manufacture something with such extreme precision.
This Tuesday (30th of April) we had a “Two thirds review” of a project we are having, it’s a Viritual Reality (VR) project where you can explore GKN Aerospace in a very modern way, we will tell you more about this when the project is finished. However, our supplier has been working with this project for a time now, reaching an approximate 66 % completion. We had previously decided that a review of the project would be needed as we reached this level so our supplier come to our site in order for us to give some feedback.
Further, they also brought some additional equipment to show how VR can be used in training and manufacturing. They also brought a Microsoft Hololens which is a Mixed Reality (MR) headset, also known as Augmented Reality (AR). We took the opportunity to invite some managers and people over within manufacturing and IT to try it out and to let them be inspired. We are convinced that this type of technology can be exploited to make our company even better in the future.
Things are moving on here at GKN in Trollhättan and we are soon at the well-deserved Christmas holidays. This week we had the opportunity to join some colleagues, doing an internship called ”Tekniksprånget”, and Maria Stavered at F7 Såtenäs, a Swedish military air base.
At Såtenäs we meet our Guide Dag Kjellberg who showed us around some hangars with old aircrafts. Dag has over 1500 flight hours with the Viggen Aircraft and a few hundred with the Gripen aircraft. We had the opportunity to walk around the hangar and see Viggen, Draken, Lansen and many other aircrafts. They are all managed and flown by its ideal organization Swedish Air Force Historic Flight, participating in flight shows all over the world.
SAAB JA 37 ViggenSAAB J37 Draken
Shortly afterwards we went to the Gripen centra, a building at F7 with the duty to promote the Swedish air force and govern the Gripen program. There, we had a lecture of the Swedish air force history by Håkan Brandt a retired pilot with a lot of experience of Viggen. Close outside, the Gripen aircrafts took off and even though we were inside, it was loud!
We headed off to the last hangars, the Gripen hangars and before entering we waited for a Gripen to take off, and we could never imagined the mighty sound of the RM12! The visual aspect of the takeoff was incredible, but the sound of the engine was marvelous! Makes one proud being from Trollhättan. Inside the hangars, Dag and Håkan talked about the cockpit, the clothing, the fire power, agility and much more. We also had the fortune to take two photos of the group in front of two Gripen aircrafts.
In front of a JAS 39 GripenIn the background: the nozzle of the RM12, the engine of Gripen. Made by GKN
It was a very giving visit and we are very glad that we had the opportunity to visit F7 Såtenäs!
Last week was a special one at GKN in Trollhättan, we had what is called Training Days which is a week full of lectures and presentations from different disciplines within the company. The purpose of Training Days is to educate the personnel and to provide all employees with new information and possibilities so that one can develop in the daily work. Courses that were offered were everything between heart and lung rescue, employeeship and Additive Manufacturing (AM).
One course that all of us trainees attended to was the introduction course in Jet engine theory where the basics of how a jet engine works is stepped through. A great course for new employees but also very giving for employees who want to refurbish their knowledge. One thing, among many other things, that we went through is the intake of air and ways of compressing it. More specifically we went through the philosophies of radial compression (Centrifugal compressors) and axial compression.
Jetmotor with Radial (centrifugal) compressor
Radial compression works by taking in air and compressing it by forcing it in a radial direction which usually ends up in the engine and aircraft being quite chubby looking. One typical aircraft ‘suffering’ from this look is the Swedish air force aircraft called Saab 29 Tunnan. The design of such a jet engine is quite simple but very robust with few rotating parts. Although being robust is a good thing, this very design allow for less parameters to be optimized or allow for changes in the design.
Jetmotor with Axial compressor
Another type of jet engine is an engine with an axial compressor instead. The air is being pushed axially along a rotating shaft from left to right seen in the picture above. This is often done by several compressor stages e.g. a Low Pressure Compressor (LPC) and a High Pressure Compressor (HPC), each compressor stage usually being a set of rotors. Here the design becomes a bit longer but less chubby and usually having a lot of different parameters that can be optimized or re-designed. An example of an aircraft having this kind of an engine is the Swedish air force aircraft called JAS 39 Gripen….and basically all other modern aircraft.
Common for the two different kind of engines is that there always has to be a combustion stage to add energy to the system. After the air has been compressed it is mixed with kerosene and ignited. The hot gas propagates further down in the engine, it sets the turbines in motion which are driving the different compressor stages and the fan which in turn allow for more air intake. Further, the gas is guided out from the engine, here though a nozzle which purpose is to further accelerate the gas so that a greater thrust can be achieved. After that it is all up to Newton’s Third Law to generate thrust in the direction of travel.
Thanks Newton!
The purpose of this blog post did not intend to give a short introduction in jet engine theory, but I guess that is what happens when one gets a bit to enthusiastic about technology, science and stuff. Perhaps you learned something or perhaps you found the lack of explanation annoying! Sorry about that!
One popular way of describing a jet engine can be done with the following figure.
The fan sucks the air in, the compressor squeezes it, the combustion ignites it and then it is blown out from the exhaust. Credit: Stanford edu
