Micro-gas Turbine Engine Research Articles

DESIGN AND MULTI-PERSPECTIVE INVESTIGATIONS ON THE AERODYNAMIC PERFORMANCE FACTORS OF CONVENTIONAL AND ADVANCED UAV’S MICRO GAS-TURBINE ENGINE NOZZLES THROUGH VALIDATED CFD APPROACH

This paper describes the internal flow behaviors, aerodynamic performance effects, noise reduction techniques, and structural characteristic study on micro gas-turbine engine (MGTE) nozzles for small fixed-wing unmanned aerial vehicles (UAV). Firstly, the primary purpose is to obtain the aerodynamic performance, aeroacoustic, and structural parameters of the nozzle when applied to the MGTE. A baseline MGTE convergent nozzle is investigated on aeroacoustics and structural characteristics. Secondly, the baseline design is implemented with noise reducers, which include notches, a step-back airfoil, and nature-inspired notches. The notch initiates small disturbances on the surface of the jet plume and deforms the shear behind the nozzle, which in turn causes suppression in the jet mixing noise. Thirdly, the step-back airfoil is used in the nozzle's trailing end to optimize the flow at the exit. This causes turbulence and flow separation at the steps located at 50% of the chord length. Here, the step-back airfoil is done with a NACA0018-based configuration. Fourthly, nature-inspired notches impose computational performances on the aerodynamic factors, so the variations are noted. The notch, airfoil, and nature-inspired notch counts are increased and decreased to find the optimum model with minimal acoustic levels. The nozzle is modeled using CATIA and analyzed in the Ansys workbench. Furthermore, the model is tested through an advanced experiment facility and analyzed for pressure variations, velocity variations, and thermal variations by implementing numerous materials.

Chlorella vulgaris microalgae derived blends in micro gas turbine engines: A comprehensive environmental impact analysis for highway vehicle applications

The significant benefits of microalgae biofuel have made it a preferred choice in various industries, including aviation. Microgas turbine engines can be promising choice for highway vehicles. This research paper investigates the process of producing fuel from microalgae, as well as its performance and emission characteristics in the micro gas turbine engine operating at sea level conditions for highway vehicle applications. A two-step extraction and transesterification process were employed to convert the biofuel, using a batch stirrer reactor for esterification. The preparation of biofuel blends followed the volume fraction method at the concentration of 10% and 30%. Additionally, nanoparticles were incorporated into the blends at a 50 ppm concentration to enhance overall characteristics of the engine. Titanium dioxide nanoparticles, known for their high surface-to-volume ratio, were used for this purpose. Experimental tests were conducted on a 30 kW micro gas turbine engine to evaluate the fuel's quality in terms of performance and emissions. Various parameters were measured at different engine speed, including 30,000 rpm, 40,000 rpm, 50,000 rpm, 60,000 rpm, and 70,000 rpm. The results obtained clearly demonstrate that the optimal blending of biofuel with neat Jet-A fuel improves performance by generating the required thrust while significantly reducing harmful gas emissions. Furthermore, the addition of nanoparticles acted as a catalyst and enhanced the quality of the fuel blends, making them an efficient alternative for aircraft engines as well. Added to above, there is an significant reduction in the emission of the CO has been noted across wide range of speed. From the results it is evident that microgas turbine engine can be an ideal choice for the highway vehicles to meet reduced carbon emissions.

Research on the Control Method of Micro-gas Turbine Power Supply Modulation System for Primary Energy in Electromagnetic Launch Technology

Combining the advantages of micro-gas turbine generation system (MTGS) and power converters, moreover, comparing the various design ideas for the primary energy of electromagnetic launch technology, we design a primary energy to meet the reliability, stability, safety and portable of electromagnetic launch technology. We discuss the control ideas and methods to be adopted in this system, the first step is to output a stable DC bus voltage through rectification, and then to step up the voltage through a series resonant converter to achieve the desired output voltage. Through theoretical analysis and simulation, it reveals the effect of this load on the performance of MTGS, and the parameter optimization design is combined with the voltage outer loop control strategy to achieve the purpose of outputting stable voltage. We used a ARM controller to implement the control of this system to measure the response curve of the system under different input commands. According to the theoretical analysis, numerical simulation and experimental results, the control strategy designed in this paper can better meet the performance index requirements of micro-gas turbine engine (MTE) and power converter as well as the control method is simple and easy to implement in engineering. The results of this paper confirm the feasibility of this primary energy application for electromagnetic launch technology.

TRANSFER OF AN ASYNCHRONOUS ELECTRIC MOTOR TO GENERATOR FOR PARALLEL OPERATION WITH MICROGRID

One of the issues of the energy sector is to increase the efficiency of energy supply to remote or isolated territories by creating microgrids based on renewable energy sources. The requirements for generators are design simplicity and high operational reliability, as well as the parameters of the generated electricity. (Research purpose) The research purpose is converting an asynchronous motor into an asynchronous generator. The technical solution for the transfer of an asynchronous electric motor to the generator has two directions: the creation of reactive energy in the electric motor and the excitation control. We took the first direction as a basis. (Materials and methods) The article presents a semi-automatic synchronization scheme for the operation of an asynchronous electric motor in generator mode, when one part of the operations is performed automatically and the other is performed manually. A test stand was made. The characteristics of an asynchronous generator when working in parallel with the grid are presented. (Results and discussion) During the analysis of the data obtained, the dependence of the power transmitted by the generator to the grid on the rotating frequency of the asynchronous electric motor was drawn. Using experimental studies, capacitor banks included in the stator winding of an asynchronous motor according to the «triangle» scheme allow it to be used as an asynchronous generator. (Conclusions) The parameters of the asynchronous generator depend on the rotation speed and the power transmitted by the micro-gas turbine engine; the semi-automatic synchronization scheme, in which one part of the operations is carried out automatically and the other manually, makes it possible to turn on the asynchronous generator to work with the distribution grid without equalizing current.

Influence of high oxygenated biofuels on micro-gas turbine engine for reduced emission

Purpose This paper aims to investigate the effect of additives in Jet-A fuel blends, especially on performance, combustion and emission characteristics. Design/methodology/approach Jet-A fuel was formed by using Kay’s and Gruenberg–Nissan mixing rules by adding additive glycerol with TiO2. While measuring the combustion performance, the amount of oxygen content present in fuel and atomization are the key factors to consider. As such, the Jet-A fuel was created by adding additives at different proportion. A small gas turbine engine was used for conducting tests. All tests were carried out at different load conditions for all the fuel blends such as neat Jet-A fuel, G10T (glycerol 10% with 50 ppm TiO2 and Jet-A 90%), G20T (glycerol 10% with 50 ppm TiO2 and Jet-A 90%) and G30T (glycerol 10% with 50 ppm TiO2 and Jet-A 90%). Findings From tests, the G20T and G10T produced better results than other blends. The thermal efficiency of the blends of G20T and G10T are 22% and 14% higher than neat Jet-A fuel. Further, the improved static thrust with less fuel consumption was noticed in G20T fuel blend. Originality/value The G20T blends showed better performance because of the increased oxygenated compounds in the fuel blends. Moreover, the emission rate of environmentally harmful gases such as NOx, CO and HC was lower than the neat Jet-A fuel. From the results, it is clear that the rate of exergy destruction is more in the combustion chamber than the other components of fuel.

Impact of additives in Jet-A fuel blends on combustion, emission and exergetic analysis using a micro-gas turbine engine

This study focuses on combustion, emission, and performance analysis of JET-A fuel blends with various additives using a micro gas turbine engine. The amount of oxygen in fuel blends and atomization are the crucial parameters in the production of a higher combustion rate with less emission. Therefore, various ratios of additives (ethanol and pentanol) are blended with biofuel (rapeseed and canola-sunflower oil) to form the JET-A fuel blends by using Kay’s and Grunberg-Nissan mixing rules. The combustion, performance and emission parameters under different engine loads were examined. Results showed that all the blends logged higher static thrust with an appreciable reduction rate in the consumption of the fuel. Among different fuel blends, R20E (Jet-A 70% fuel, 20% Rapeseed, and 10% ethanol) showed 35% increase in static thrust associated with 41% reduction in thrust specific fuel consumption. Moreover, the blends R20E and CS20E (Jet-A fuel 70%, Canola- Sunflower 20% and 10% ethanol) indicated 24% and 10% increase in thermal efficiency respectively due to the influence of ethanol concentration and higher oxygen content. In addition, these fuel blends generate less emission of environmental unfriendly harmful gases, including NOx, CO, and HC, compared to neat Jet-A fuel. Results revealed that the exergy destruction values are higher for the combustion chamber than the other conventional fuel components.

Evaluating high volume blends of vegetable oil in micro-gas turbine engines

Vegetable oil was examined to determine if high volume blends with No. 2 ultra-low-sulfur diesel could be successfully utilized in micro gas turbine engines. Property data, and atomization and micro-gas turbine engine studies were examined for blends of up to 75% by volume soybean oil with No. 2 ultra-low-sulfur-diesel (ULSD). Kay's and Grunberg-Nissan mixing rules were found to predict specific gravity and viscosity, respectively, based on composition to a high level of accuracy. For Kay's mixing rule the AADs were below 1%, while AADs for the Grunberg-Nissan equation stayed under 4%. Atomization tests showed an increase in cone angle of 18° for a 30-degree nozzle with a mixture of 50% soybean oil/ULSD over that of pure soybean oil. The pour point for blends of V50 and V75 were found to meet the ASTM D2880-13b Fuel Oil Specifications for gas turbine engines. For a V50 blend the spray angle was increased by 50% over that of pure SBO. The micro-gas turbine engine performed well for fuel blends up to 75% vegetable oil, with comparable engine efficiencies to that of ULSD. Engine efficiency and thrust increase with increasing RPM. The studies indicate that high volume blends of straight vegetable oil with ULSD are suitable in micro-gas turbine engines.

하이브리드 타입 초소형 가스터빈엔진 개발 및 초도 시운전

In this study, a 2W micro-gas turbine engine was designed using micro-electro-mechanical systems (MEMS) technology, and experimental investigations of its potential under actual combustion conditions were performed. A micro-gas turbine (MGT) contains a turbo-charger, combustor, and generator. Compressor and turbine blades, and generator coil were manufactured using MEMS technology. The shaft was supported by a precision computer numerical control (CNC) machined static air bearing, and a permanent magnet was attached to the end of the shaft for generation. A heat transfer analysis found that the cooling effect of the air bearing and compressor was sufficient to cover the combustor’s high temperature, which was verified in an actual experiment. The generator performance test showed that it can generate 2W at design rotational speed. Prototype micro-gas turbine generated maximum 1 mW electric power and lasted up to 15 minutes.

High-efficiency approach for fabricating MTE rotor by micro-EDM and micro-extrusion

Micro-gas turbine engine (MTE) rotor is an important indicator of its property, therefore, the manufacturing technology of the microminiature rotor has become a hot area of research at home and abroad. At present, the main manufacturing technologies of the MTE rotor are directed forming fabrication technologies. However, these technologies have a series of problems, such as complex processing technology high manufacturing cost, and low processing efficiency, and so on. This paper takes advantage of micro electric discharge machining (micro-EDM) in the field of microminiature molds manufacturing, organizes many processing technologies of micro-EDM reasonably to improve processing accuracy, presents an integrated micro-EDM technology and its process flow to fabricate MTE rotor die, and conducts a series of experiments to verify efficiency of this integrated micro-EDM. The experiments results show that the MTE rotor die has sharp outline and ensure the good consistency of MTE rotor blades. Meanwhile, the MTE rotor die is applied to micro extrusion equipment, and technologies of micro-EDM and micro forming machining are combined based on the idea of the molds manufacturing, so the MTE rotor with higher aspect ratio and better consistency of blades can be manufactured efficiently. This research presents an integrated micro-EDM technology and its process flow, which promotes the practical process of MTE effectively.

Design and Fabrication of an Aerodynamic Micro-Air Journal Bearing Using Micro-Wire Electrical Discharge Machining

This paper proposed a removal analysis and a contouring strategy of accurate micro-WEDM processing for an aerodynamic micro-air journal bearing for micro-gas turbine engine. It is designed based on aerodynamic theory and can be self-acting by the compressed air pressure. The rotor is stably rotated in a relatively low speed which is below one hundred thousand revolutions per minute, and is much lower than other references. The extended and trimmed tool path is adopted in this paper, and the cusp at the corner of the micro-air journal bearing is obtained by this method which is better than the common arc tool path. The inner and outer diameter of the micro-air journal bearing with a satisfactory shape and good surface quality is 1.068mm and 1.165mm, respectively. The minimum radius at the bottom of wedged-structure is 15.9μm. The kerf of the blanking is 43μm, and the machining discharge gap is 18μm under this machining conditions. The MRR calculated by experimental data is 0.00144mm2/min.

POWER GENERATION AT THE MICRO SCALE

The present work is to show the development of micropower systems or power MEMS characterized by thermal, electrical and mechanical power density 1~20 Watts in sub-centimeter-sized packages. Three kinds of typical micro power systems, namely, the micro-gas turbine engine, the MEMS rotary micro engine, and a micro thermoelectric system, are described in this paper. A novel microthermophotovoltaic (micro-TPV) system, which is being developed in NUS, is also introduced in this work. The system uses hydrogen as fuel and is able to deliver electrical power in the order of watts in a package less than 1 cubic centimeter in volume. The main components of the system are a heat source, a selective emitter, and a photovoltaic (PV) array. The performance of the system is largely affected by the materials of the emitter and the PV cells. When the emitter is made of Co/Ni-doped MgO, and the PV cells are made of GaSb, a 4.4 W electrical power output can be expected.

Igniters and temperature sensors for a micro-scale combustion system

Abstract This paper presents the development of micro-fabricated “on-chip” polysilicon igniters and temperature sensors for the combustion system of a micro-gas turbine engine. We have reported the design and fabrication results of a novel through-wafer interconnect scheme that could greatly facilitate electrical contacts in multi-level MEMS devices by allowing direct electrical access to the backside of a wafer. This paper presents the results of a further effort that uses these interconnects to make electrical contacts to a thin-film polysilicon resistor so as to evaluate its ignition capability and its use as a wall temperature sensor for the micro-gas turbine engine. An application of the through-wafer interconnects to a concept demonstration of thin-film polysilicon resistive igniters for the micro-engine showed that it was possible to initiate combustion and locally raise the temperature of the igniter to 900 °C so long as the chip is thermally isolated. The results were found to be in good agreement with the predictions of an FEM thermal model. The possibility of using the resistors as temperature sensors is also examined. The non-linear variation of polysilicon resistivity with annealing temperatures due to complex effects resulting from dopant atom segregation, secondary grain growth and crystallographic relaxation reduced the operating range of the sensors to 450 °C.

Combustors for Micro-Gas Turbine Engines

The development of a hydrogen-air microcombustor is described. The combustor is intended for use in a 1 mm2 inlet area, micro-gas turbine engine. While the size of the device poses several difficulties, it also provides new and unique opportunities. The combustion concept investigated is based upon introducing hydrogen and premixing it with air upstream of the combustor. The wide flammability limits of hydrogen-air mixtures and the use of refractory ceramics enable combustion at lean conditions, obviating the need for both a combustor dilution zone and combustor wall cooling. The entire combustion process is carried out at temperatures below the limitations set by material properties, resulting in a significant reduction of complexity when compared to larger-scale gas turbine combustors. A feasibility study with initial design analyses is presented, followed by experimental results from 0.13 cm3 silicon carbide and steel microcombustors. The combustors were operated for tens of hours, and produced the requisite heat release for a microengine application over a range of fuel-air ratios, inlet temperatures, and pressures up to four atmospheres. Issues of flame stability, heat transfer, ignition and mixing are addressed. A discussion of requirements for catalytic processes for hydrocarbon fuels is also presented.