Operation Of Microturbine Research Articles

Steam injection experiments in a microturbine – A thermodynamic performance analysis

This paper reports on a series of steam injection experiments on a Turbec T100 microturbine. Combined Heat and Power (CHP) systems, such as the considered T100 microturbine, use one single primary fuel to simultaneously produce electric and thermal power. In doing so, they realize significant energy savings compared to conventional schemes of separated production. However, a reduction in the demand for heat (e.g. in summertime) will force this type of units to shutdown. This significantly reduces the amount of operating hours and has a severe negative impact on the net present value of such CHP investment projects.The aim of this paper is to investigate and demonstrate the effects of steam injection in the compressor outlet of a microturbine operating under reduced heat demand conditions, in order to keep the unit running. The necessary steam can be auto-raised with heat available in the turbine exhaust downstream of the recuperator. Such an injection will keep the unit running and thus avoid a forced shutdown. Furthermore, it is expected that the electric efficiency will rise and that the power production will become more economically viable as a result of the increasing operating hours.This paper reports on the influence of steam injection on the electrical efficiency and shaft speed of a T100 unit. ASPEN® simulations of the behavior of the CHP unit are also presented. These simulations predicted a 2.2% rise in electric efficiency at nominal electrical output when 5% of the mass flow rate of air is replaced by steam.The steam injection experiments resulted in stable runs of the unit, a predicted reduction in shaft speed and increasing electrical efficiency. Validation of the ASPEN® simulations against the experimental data revealed the necessity for a more accurate determination of the air mass flow rate and more precise compressor characteristics.

Long-Term Microturbine Exposure of an Advanced Alloy for Microturbine Primary Surface Recuperators

Haynes alloy HR-120 (Haynes and HR-120 are trademarks of Haynes International, Inc.) forms a protective oxide scale when exposed to the harsh operating environment of a microturbine primary surface recuperator. Primary surface recuperators manufactured from HR-120 are currently in use on the Capstone C65 MicroTurbine (MicroTurbine is a registered trademark of Capstone Turbine Corporation). Long-term microturbine tests of this alloy are currently being conducted at an elevated turbine exit temperature (∼100°F higher than that in a normal operation) at Capstone Turbine Corporation. Alloy samples that have been tested under steady-state microturbine operating conditions are removed after predetermined exposure intervals for characterization by Capstone Turbine Corporation in collaboration with Oak Ridge National Laboratory. Such evaluations include the characterization of surface oxide scales and the associated alloy compositional changes following a steady-state operation ranging from 1800 h to 14,500 h. Results from the microstructural and compositional analyses of these long-term steady-state engine-tested HR-120 samples are used to illustrate the progression of alloy oxidation in the microturbine operating environment.

Design analysis of Tesla micro-turbine operating on a low-boiling medium

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Hammerstein-model-based predictive control of micro-turbines

Micro-turbine operation is restricted due to mechanical, thermal, and flow limitations. Model predictive control is selected because it can explicitly handle the nonlinearities, and constraints of many variables in a single control formulation. The Hammerstein models are particular kinds of nonlinear systems where the nonlinear block is static and is accompanied by a linear system. This paper suggests a model-based controller for the regulation of a micro-turbine. The performances using both the linear and Hammerstein models are studied with constraints. The results show the capabilities of the proposed control to track a periodic reference trajectory and a significantly better closed-loop response. Copyright © 2005 John Wiley & Sons, Ltd.

Development and Operation of Micro Turbine

Takuma's TCP 30 Micro Turbine Co-Generation Package is built around a 28kW micro gas turbine power generator made by Capstone. Compared with a gas engine and other reciprocating engines, microturbine has excellent features such as small size and light weight, high efficiency, low environmental burden, no vibration, no maintenance etc. It also embodies waste heat recovery by the use of Takuma's steam generator of supplemental firing with an economizer. The package consists of the engine, a gas compressor. microturbine control and power conversion units, waste heat recovery equipment, its control unit and other ancillaries. It solves the dilemma of reducing noise inherent to an ultra-high speed generation system and removing heat from electronic equipment efficiently within a compact package.This package has the capacity of generating 26 k W of effective electricity, 600kg/h of evaporation (712kg/h of equivalent evaporation), with high system efficiency of 93%. Because of its high efficiency, the package saves roughly 20% in energy and reduces approximately 25% of CO2 emission over the conventional system of purchased power from the utility and steam from a boiler. It also reduces the user's operating cost significantly. and rapid increase of application is anticipated in areas such as hotels, athletic clubs, public baths, hospitals and factories where large demand for steam exists.

Microturbines-an economic and reliability evaluation for commercial, residential, and remote load applications

Most distributed self-generation operates base loaded and in parallel with the electric utility system: (1) to minimize peak loads; (2) to improve reliability; (3) to eliminate the need for reserve margin (standby); and (4) may or may not sell back excess generation. This paper examines the economics of distributed microturbine generation operating isolated from the electric utility system and having enough reserve margin to either match or improve the existing reliability of service provided by central station generation and the T&D system. This analysis shows the isolated operation of microturbines with a reserve margin can provide the same or a higher level of reliability as the electric utility, yet the costs can be lower. Sensitivity analysis for different investment costs, O&M costs, fuel costs, reliability, load shapes (load factors) and alternative fuels were performed and the economic comparisons are made in terms of c/kWh. This analysis shows a strong economic preference in applying microturbines to high load factor commercial loads. The cost of standby (from the utility) was found to be from .52 to 1.09 c/kWh greater than if the microturbine generation provided its own standby through a built in reserve margin.