Design of test mechanism to evaluate thrust and performances in turbojet engines and calculation of turbojet engine efficiency in this test mechanism

This thesis explains the theoretical concept, engineering design, and experimental practice of a dedicated experimental device that measures thrust output, performance parameters, and efficiency factors of miniature turbojet engines. The aim was to develop an economically sound, accurate, and efficient mechanism to achieve consistent and reliable results in a controlled laboratory environment. Test facility is built upon a linear bearing table that is optimized for low friction, which holds two 15-kg load cells to enable accurate thrust measurement within a very wide operational range. Data capture is done through an Advantech USB-4711A system that is integrated with LabVIEW software, thus enabling real-time display and measurement of several quantities like thrust, compressor outlet temperature (T₂), exhaust gas temperature (T₄), inlet and outlet pressure, air velocity, and fuel mass flow. The arrangement enables simultaneous measurement of key mechanical, thermal, and fluid dynamic quantities that are relevant to performance characterization. Experimental studies were performed with a JetCat P80 micro turbojet engine, which achieved rotational speeds of 125,000 rpm. In a condition of maximum loading, 97 N of thrust was achieved together with an exhaust-gas velocity of 1,305 km/h and a fuel consumption velocity of 0.275 L/min, which corresponded to specific fuel consumption (SFC) of 0.15 kg/(N·h). Polytrophic compressor efficiency was equal to 81.6 %, thermal compressor efficiency was 27.3 %, and combustion efficiency was 50.1 %. Comparison of results derived experimentally with theoretically calculated estimations, based on the Brayton open cycle model, showed differences within ±3 %, thus confirming reliability and accuracy of constructed test equipment. The study provides evidence that the proposed test rig ensures that turbojet performance is assessable in a scalable, accurate, and multidimensional manner. Its characteristics combine thrust measurement, thermal investigation, and efficiency testing within an integrated experimental setup makes it valuable for research purposes, boosting propulsion system performance, and optimizing components. Additionally, its hybrid platform nature that makes it useful across different small gas turbines further increases its applicability in academic and industrial environments.