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Purpose The purpose of this paper is to improve the lubrication and remove as much as possible of the heat generated in the bearing assembly, embedded in the jet engine. Design/methodology/approach To determine the necessary values of the air pressure and oil amount, an experimental approach is used. For that purpose, a custom made test rig is developed. Findings Less amount of oil makes better lubrication conditions, reflected in the smaller temperature of the bearings. Concerning the air pressure, too high and too low air pressure deteriorates the lubrication parameters. An optimum value should be determined experimentally. The influence of oil amount is remarkably bigger than the influence of air pressure. Originality/value This experimental investigation provides an easy and fast way to improve the high-speed bearings lubrication parameters.

Subsonic ramjets, due to its simplicity, nowadays could be very attractive for expendable unmanned applications. However, due to very low efficiency at low Mach numbers, practically there isn’t any important application at subsonic speed. In 50’s subsonic ramjet was used for tip jet applications. Later in 70’s there was a study of Fan Augmented Ramjet (FARJ) where a fan was in-tended to be powered by a piston engine, both in subsonic and supersonic regimes. Almost at the same time it was analyzed ejector augmented subsonic ramjet. Both of these studies did not find real application of such engines. Finally, there was an attempt for the use of an Electric Ducted Fan, used in RC models, with a combustor but exit fan pressure was almost at atmospheric pressure which results in very low efficiency.

For decades, the memory hierarchy was determined based on latency, bandwidth, and cost between processors, random access memory (RAM), and secondary memory. Although the gap between the processor and RAM has been dampened by fast cache memory, the gap between RAM and secondary memory has remained challenging, expanding to 12 size range in 2015 and continuing to expand by around 50% per year. The rapid development of nanotechnology has triggered a new field in the organization of memory space. For more than a decade, FRAM - ferro random access memory has been in use, which keeps data in the form of a polarization of the ferroelectric crystal that does not lose polarization after the power is turned off. The real revolution is expected in the use of magnetic resonance random access memory (MRAM), which represents data storage technology using magnetic moments, not electric charges. Unlike conventional RAM chips, data in MRAM are not stored as an electrical charge, but with magnetic storage elements. The advantage of this memory is energy independence, that is, the storage of recorded data and the absence of power supply. MRAM has similar properties as SRAM, similar to the density of the record as dynamic RAM (DRAM), with much less consumption, and in relation to flash, it is much faster and with time does not degrade its performance. Theoretically, there is no limit to the number of read and write, so new memories could last unlimited. The paper will discuss this new type of memory organization.

U ovom radu se predlaže inovativnu konstrukciju ispitnog stola za precizno mjerenje vektora potiska raketnog motora tijekom njegovog rada. Jasno je izložena konstrukcija ispitnog stola kao i procedure te matematički model za kalibraciju ispitnog stola. Metoda obrade podataka dobivenih ispitivanjem kao i rezultati ispitivanja "jet tab" sustava za upravljanje vektorom potiska detaljno su prezentirani. Eksperimenti su pokazali da je ispitni stol iznimno funkcionalan, a da dobineni rezultati imaju odličnu ponovljivost i poklapanje s rezultatima autora koji su koristili ispitne stolove drugačije konstrukcije za mjerenje istog ili sličnog mehanizma za upravljanje vektorom potiska., This study proposes an innovative test stand design to accurately measure rocket motor thrust vector during its operation. Test stand design is clearly presented as well as procedure and mathematical model for its calibration. A method of processing data obtained from the experiments and the results of the jet tab system for thrust vector control are presented in detail. Experiments have shown that the test stand is highly functional and the results obtained have excellent repeatability and matching with the results of the other authors who have used different construction test stands for measurement of the same or a similar mechanism for thrust vector control.

A parametric, on-design performance analysis of an existing single-spool expendable turbojet engine with a short afterburner is presented in this paper. A design point mathematical model of the engine is developed to obtain the optimum system performance conditions. This model utilizes the engine design parameters, such as operating flight conditions, compressor pressure ratio, turbine inlet temperature and afterburner exit temperature to predict the engine performance parameters, such as specific thrust and specific fuel consumption. The results obtained are in a good agreement with commercial software, GasTurb, used for the performance analysis of gas turbine engines and with the available experimental data. Subsequently, the effects of adding a short afterburner on the performance of the engine were studied using a parametric analysis. A theoretical database for different performance parameters was obtained as a design reference for the future work.