# Thermodynamic Analysis and Performance Evaluation of Microjet Engines in Gas Turbine Education
## 1 Introduction  
A micro gas turbine is a reduced-scale heat engine that operates with similar cycles and components to those found in large gas turbines, with a power range of 25 kW to 300 kW [1]. Compared to jet engines, the primary components of a micro gas turbine engine typically include a centrifugal or mixed-flow compressor, a combustion chamber, a single-stage axial-flow or radial-flow turbine, and a jet nozzle. Presently, micro turbojet engines are the most accessible and practical type of micro gas turbine. This is due to their simple design, low manufacturing and maintenance costs, and ease of operation [2]. Micro turbojet engines have a wide array of engineering applications, including both military and civil aviation, as well as power generation. These micro engines are particularly suited to such applications because of their high power-to-weight ratio, multi-fuel capability, and design simplicity [3]. In the military sector, a significant application of microjet engines is as propulsive power sources for Unmanned Aerial Vehicles (UAVs), owing to their higher energy density (Whr/kg) [3, 4]. In the civilian sector, they are suitable for portable power units, radio-controlled (RC) aircraft models, and distributed power generation in combined heat and power applications [4]. Due to the technical advantages mentioned above, micro gas turbines are not only utilized for UAVs and power generation but also have significant applications in the field of gas turbine education. These engines can be installed in small laboratories without the need for complex or expensive infrastructure [2]. Consequently, they can easily become components of propulsion laboratories or small turbine engine test facilities for gas turbine education. Typically, gas turbine labs help students enhance their theoretical knowledge of gas turbines through practical experience. By conducting engine run tests, students cancompare theoretical data with experimental data or with other calculated data derived from measurements. Through these experimental tests, a technical reference is established to understand the fundamentals of gas turbine theory and to validate the reasoning behind assumptions and approximations made in analytical performance evaluations [5; 6]. Currently, aerospace institutes and research entities such as the German Aerospace Center (DLR) [7; 8; 9; 10] are developing small propulsion laboratories or mobile test facilities as research infrastructure. These facilities are used to study new potential propulsion programs with the aim of improving gas turbine performance [3]. Additionally, aerospace universities are involved in various academic research projects in the field of gas turbines using micro propulsion laboratories [11; 12]. The objective of these projects is to optimize performance parameters such as specific fuel consumption, noise and emissions, overall pressure ratio, gas temperature in front of the turbine, turbine and compressor efficiencies, engine thrust, and power [3; 11]. Small microturbine engines are very useful for conducting experiments for both educational and research purposes because they do not require the extensive testing infrastructure needed for larger turbine engines. Using microturbine engines for educational purposes is a highly practical option for experiments serving subjects such as turbine processes, thermodynamics, acoustics, chemical pollution, and alternative fuels. Several studies present the use of small turbine engines that, in addition to their educational applications, have been used in the production of scientific papers on experimental and numerical simulation [13]. For example, the study [14] examines the transient processes that occur with various fuels and under different atmospheric conditions. Additionally, the study [15] presents methods for increasing thrust and reducing noise using an ejector for a micro engine, while another study [16; 17; 18] explores performance and gas emissions using alternative fuels.