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How is a jet engine developed and manufactured?

This year at the Aerospace technology division (ATD), in addition to the previously announced PBS TJ80 engine, we also presented the PBS TJ150 engine. This is the fifth most powerful jet engine type that we supply to foreign markets. In the following article, you can read about the process of creating a new turbojet engine.  

How is a jet engine developed and manufactured?
The PBS TJ150 mainly stands out with its excellent thrust-to-weight ratio as well as the engine's outer diameter, which are the most viewed parameters in this aircraft drive category. Other advantages include its compact design, an integrated starter generator, reliability when starting up the engine under harsh climate conditions, and the added possibility of starting in mid-flight at high speeds and high altitudes.

The project of developing a new engine was based on the upgrade of the current PBS TJ100 engine with a power output of 1,300 N. It was clear from the beginning that it would be necessary to make complex structural changes in order to be able to reach a higher thrust while maintaining the same diameter and engine weight.

At the beginning of 2017, the basic design sketch was made. The calculation department made the thermodynamic calculations, structural calculations and the design of the engine’s through-flow parts. After verifying the calculations, it was necessary to create detailed drawing documentation for manufacturing the prototypes. We managed to accomplish this in mid-2017, which is an excellent result considering the complexity of the entire process. The engine required a range of innovations, among others a new turbine stage, a new concept of the bearing case and, most notably, an integral radial-axial diffuser, which optimises the flow of compressed air into the combustion chamber.

This new technical solution allowed the engine to reach the nominal parameters while keeping the outer diameter of the engine to 272mm. It was so innovative that the company patented it. The subject of the patent is used in the design of several other jet engines from PBS production.

Production process
After creating the complete technological documentation, the individual parts entered production. During production, classic and modern technologies were used, among others, five-axis CNC machining, electrical discharge machining, the manufacturing of the combustion chamber with laser technology, and also the implementation of stamping technology instead of metal knocking, which increased the accuracy of the individual components in the combustion chamber. Modern technologies were also used for the grinding of gears or for surface treatments. All of these technologies are ensured by the ATD with its own production capacities. After the final assembly of the engine, only the electronic equipment is purchased, such as the engine control unit (ECU), cabling and a few other components. 

Assembly and testing of the first prototypes
After finalising the production of the components, assembly took place. Before the end of 2017, tests of the first prototype were able to begin. During the tests, it was verified that the engine was able to meet the required parameters, but the first results weren’t entirely optimal. A planned optimisation mainly of the fuel and oil systems and the control system took place. During further tests, various variants of the through-flow parts were verified with the goal of reaching the best possible parameters.

Based on the specific measurements and their evaluations, the design department came up with a fairly radical step in the turbine’s design. Due to time constraints, 3D printing technology was selected for the development of the new turbine, although this technology is not ideal for the use of Inconel 718 material.
Several potential suppliers from home and abroad were pre-selected. Production completion took place at a Czech manufacturer. The new turbine manufactured with this technology was available within a relatively short time, but it was not possible to reach the required strength of the material and an accurate enough geometry. Despite this, however, an improvement in the newly developed turbine’s parameters was demonstrated.

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The final version of the engine’s development
In the fourth quarter of 2018, the final configuration of the engine was defined. In this design, it was necessary to realise all the defined tests and inspections for validating the functionality of the engine during the desired operating conditions. After satisfactory testing was completed in August of 2018, the creation of the serial production documentation and its issuance into serial production followed. At the conclusion of the project, it was necessary to create operational regulations and documentation for customers. Development was concluded with the manufacturing of prototypes in the serial design, which meet the required technical parameters from the beginning of the development. And so, the company has another sophisticated product with which it can reach out to an even wider spectrum of customers that are mainly recruited from the defence industry, mainly in Europe and Asia.