Advances in the Development of a Microturbine Engine

Abstract

Advances in the Development of a Microturbine EngineTo reduce the size and weight of power generation machines for portable devices, several systems to replace the currently used heavy batteries are being investigated worldwide. As micro gas turbines are expected to offer the highest power density, several research groups launched programs to develop ultra micro gas turbines: IHI firm (Japan), Power-MEMS Consortium (Belgium). At Onera, a research program called DecaWatt is under development in order to realize a demonstrator of a micro gas turbine engine in the 50 to 100 Watts electrical power range. A single-stage gas turbine is currently being studied. First of all, a calculation of the overall efficiency of the micro gas turbine engine has been carried out according to the pressure ratio, the turbine inlet temperature, and the compressor and turbine efficiencies. With realistic hypotheses, we could obtain an overall efficiency of about 5% to 10%, which leads to around 200 WI kg when taking into account the mass of the micro gas turbine engine, its electronics, fuel and packaging. Moreover, the specific energy could be in the range 300 to óOOWh/kg, which largely exceeds the performance of secondary batteries. To develop such a micro gas turbine engine, experimental and computational work focused on: (1) a 10-mm diameter centrifugal compressor, with the objective to obtain a pressure ratio of about 2.5: (2) a radial infiow turbine; (3) journal and thrust gas bearings (lobe bearings and spiral grooves) and their manufacturing: (4) a small combustor working with hydrogen or hydrocarbon gaseous fuel (propane): (5) a high rotation speed microgenerator: and (6) the choice of materials. Components of this tiny engine were tested prior to the test with all the parts assembled together. Tests of the generator at 700,000 rpm showed a very good efficiency of this component. In the same way, compressor testing was performed up to 500,000 rpm and showed that the nominal compression rate at the 840,000 rpm nominal speed should nearly be reached.

Study of KJ-66 micro gas turbine compressor: Steady and unsteady Reynolds-averaged Navier–Stokes approach

“…Besides the extensive study regarding conventional gas turbines, [1][2][3][4][5] ongoing endeavors are made to understand the MGT performance. [6][7][8][9][10][11] MGT differs itself from conventional gas turbine due to its low operating Reynolds number and hence a relatively higher skin friction and heat transfer rate. 12,13 Existing research mainly focuses on the design of the engine, 14,15 combustor development, [16][17][18] combustion and emission, 9 combustion instability, 19,20 heat transfer, 21 control strategy, 22 etc.…”

Design and optimization of a liquid ring thrust bearing

“…With the rapid development of microelectromechanical systems (MEMS), micro-turbines [1,2], micro-gyroscopes [3][4][5][6], and micro-generators [2,7] are becoming increasingly important due to their compact size and the unique function they perform. However, as the length scale reduces to millimeter sizes and below, capillary forces induced by surface tension, dominates other forces such as electrostatic force and inertia.…”

Theoretical design, manufacturing, and numerical prediction of a novel multileaf foil journal gas bearing for PowerMEMs

“…1,2 Some of their applications include propel systems of portable batteries, artificial pacemakers, micro-robots, and unmanned air vehicles. [3][4][5] With the intense requirement of high power density and efficiency for PowerMEMs, a stable high-speed operation bearing system is still the most critical challenge. 6 In particular, friction, wear, and lubrication problems become much pronounced due to size constraints.…”