Three technological bricks for a micro turbine concept for micro power generation O. Dessornes 1 , J. Guidez 1 , Y. Ribaud 1 , T. Courvoisier 1 , C. Dumand 1 , M. Orain 1 , Z. Kozanecki 2 , P. Helin 3 , P. Le Moal 3 , P. Minotti 3 PowerMEMS 2005 conference, Tokyo, Japan 1 Onera, DEFA, Chemin de la hunière 91761 Palaiseau CEDEX, France, E-mail : olivier.dessornes@onera.fr 2 Institute of turbomachinery, Technical university of Lodz, 219/223 Wolczanska St. 93-005 Lodz, Poland, E-mail : zkozan@p.lodz.pl 3 SilMach, 24 rue de l’épitaphe, 25 000 Besançon, France, E-mail : pminotti@silmach.com Abstract Research on three technological bricks applied to a microturbine, namely the microcombustion chamber, the gas bearings and the feasibility by MEMS technology have been conducted. A general concept was used as a guideline for the three topics. Concerning the combustion, first tests were carried out concerning the mixing in microchannels. A study of the combustion with 0D analysis focused on the influence of the heat losses and of the fuel/air mixing an finally 3D computations were also performed. Concerning the gas bearings, a concept suited to MEMS technology was chosen. Groove bearings as thrust bearings and tilting pads for journal bearings have been computed and will be soon tested at scale 5/1. Concerning the MEMS technology, process flow studies have begun and first microturbines have been satisfactory etched. The main concern for this issue is the etching of the gap for the tilting pads. Keywords : PowerMEMS, microturbine, combustion, gas bearing NOMENCLATURE C : radial clearance of the bearing Da : Damkholer number m' : mass flow rate Pa : ambient pressure Pg : gas pressure Re : Reynolds number Tg : gas temperature  : residence time μ : viscosity R : shaft radius V : volume  : angular speed 1 INTRODUCTION Due to the increase in power requirements, many efforts have been done over the past decade to build a micro heat engine able to produce electricity in order to replace batteries in portable systems such as robots or computers for example. Among those systems, Onera decided to focus on the microturbine concept which seems very promising for microdrone propulsion. The first work was mostly dedicated to the energetic behaviour of such engine which led to better understand the key points to address from a energetic point of view to make this concept feasible [1]. The resulting concept is a 8 mm diameter turbine with the combustor located above it (figure 1). Figure 1 : proposed microturbine concept The strategy is to separate the combustion chamber from the compressor/turbine. This allows to reduce the surface/volume ratio and then to decrease the heat losses. This also allows to benefit from a larger combustion chamber and then larger residence time that could help to increase the combustion efficiency. In addition, this also yeld to a cooler compressor compared to a annular design (MIT type) and finally this also simplify the combustion chamber machining by avoiding etched and then bonded silicon wafers. As a first stage, it was decided to study and the design three technological bricks that could be suited to this concept : • the microcombustion, • the gas bearings, 65