Mems

Abstract:
This paper reviews the applications of MEMs in the specific field of gas turbine power generation. The treatise goes from an introduction of MEMS and gas turbine power generation to the scaling issues, specific designs, micro manufacturing, experimental information and potentials of use. Specific scaling factors are addressed in the work and designing feasible arrangements that areupright in terms of mechanical performance and with the futuristic projection of making its portability and its power generation efficiency and capabilities.















Introduction to MEMS and gas turbines:
The development of small-scale systems has had a tremendous potential perspective on the industrialized field since the 80s. Although, the technology fromwhich MEMs come from are dated back with the production of monolithic integrated circuits, i.e. RCA in 1955 after the invention of transistor [1]. MEMs, the acronym for Microelectromechanical systems is a field that make usage of all modern engineering disciplines and sciences as chemical, physics, electoral engineering, etc. Apart from the effort of building integrated reduced circuitry, MEMsis the major step towards the miniaturization of machines and devices. Moreover, the idea of MEMs has enlightened the minds of scientists, researchers and industry to manufacture ideal and personalized devices. One of these potential applications is the production of energy in a portable scale.
For instance one of the most prominent uses of MEMs in the energy production field is the futuristicconcept of a portable gas turbine engine. Based upon the theory under macroscales gas turbine engines scientists of the Massachusetts Institute of technology (MIT) opened a program in 1995 to study the capabilities of a millimeter-scale microelectormechanical gas turbine engine.
Gas turbine engine cycles are one of the most fascinated concepts. It starts with an internal-combustion mechanismthat compresses air, drives it into a combustion chamber and uses the hot gases produced by the combustion to enter nozzle blades that are located in a specific arrange that will cause the main turbine disk to rotate and that will drive the compressor of the initial state. At final state of the cycle a shaft is attached to the turbine disk that will provide the motion needed for a generator head toproduce electrical power, as seen in figure 1.

Figure [ 1 ]. Profile of a regular gas turbine power generator

With this idea in mind MIT scientist looked into the idea mimicking a gas turbine cycle at the microscale.

Scaling considerations:
In order to scale down the idea of a gas turbine cycle, trends and studies were performed to predict how feasible a gas turbine cycle can be atthe microscale. One of the first actions was to consider thermodynamic and mechanic effects that could differ from the macroscale world. It is known that at micro scale physical phenomena tends to behave distinct. That is why scientist had to sort out most important fields in which to focus most effort to overcome the new challenges that miniature scale faces.

Thermodynamics scalingconsiderations
The conventional concept of gas turbine was applied to the microturbine. As its macroscale predecessor, microturbines are to be composed of a compressor, a combustion chamber and a turbine driven by the exhaust combustion gases, that it could power an electric generator. According to experimental data, a meter-diameter air intake area is able to generate about 100MW. Tens of watts would beproduced when such a device is scaled to millimeter size if the power per unit of air flow is maintained [2]. Thus, for a 1 mm of intake air diameter corresponds about 100W of power. Temperatures are also another issue, exit temperatures can range from 1200-1600K with a rotoperipheral speed of 300-600m/s [2]. Nevertheless, the most concerning down-scaling factors are related to fluid viscosity...