Supersonic ion beam formation has been observed in a geometrically expanding low-pressure inductively coupled argon plasma. It is found that the ion beam is only observed below 3mTorr and only when the discharge is operated in inductive mode. The geometrical expansion of the plasma induces density and potential gradients leading to the ion beam formation. The ion beam energy increases with decreasing source tube radius. The results show that ion beam formation can be achieved by geometrical expansion alone and that the ion beam energy depends on the ratio of the cross-sectional area of the source and expansion region.
The spatial distribution of an ion beam—created at the interface of a small diameter plasma source and much larger diameter diffusion chamber—is studied in a low-pressure inductively coupled plasma using a retarding field energy analyzer. It is found that the ion beam density decays axially and radially in the diffusion chamber following the expansion of the plasma from the source region. The radial distribution of the ion beam indicates that the acceleration region has a convex shape and is located just outside the source exit, giving rise to a hemispherical plasma expansion into the diffusion chamber.
To establish micro gas turbine (MGT) systems in a wide field of CHP applications, innovative combustion concepts are needed to meet the demands for low exhaust gas emissions, high efficiency and reliability as well as high fuel flexibility. A promising technology for future MGT combustion is the FLOX® concept. The goal of the presented work is to prove the feasibility of a double–staged, FLOX®–based MGT combustion system on a MGT test rig. The paper reports a reliable operating behavior of a Turbec T100 MGT in combination with the new FLOX®–based combustion chamber utilizing natural gas. The measured exhaust gas emissions are compared for different configurations of the combustion chamber and the standard Turbec system. It is shown that the carbon monoxide emissions are reduced whereas the nitrogen oxide emissions exceed the emission levels of the standard MGT burner. However, they still fall far below the German legal limits. For helping to interpret the results of the MGT combustion system, the double–staged combustor is compared to a single–staged FLOX®burner on basis of atmospheric measurements. Here, it is shown that the margin to lean blow–off is substantially increased by the fuel staging. Moreover, it is demonstrated that the exhaust gas emissions of the double–staged combustor could be kept at a similar very low level by applying the staging. Additionally, the overall reaction regions are reported by OH* chemiluminescence imaging as a function of burner air number. Based on this atmospheric study the transfer to MGT conditions is made and appropriate measures are derived to optimize the exhaust gas emissions of the MGT FLOX® combustion system.
For the development of efficient and fuel flexible decentralized power plant concepts a test rig based on the Turbec T100 micro gas turbine is operated at the DLR Institute of Combustion Technology. This paper reports the characterization of the transient operating performance of the micro gas turbine by selected transient maneuvers like start-up, load change and shut-down. The transient maneuvers can be affected by specifying either the electrical power output or the turbine speed. The impact of the two different operation strategies on the behavior of the engine is explained. At selected stationary load points the performance of the gas turbine components is characterized by using the measured thermodynamic and fluid dynamic quantities. In addition the impact of different turbine outlet temperatures on the performance of the gas turbine is worked out. The resulting data set can be used for validation of numerical simulation and as a base for further investigations on micro gas turbines.
Auxiliary power unit (APU) operators face increasingly stricter airport requirements concerning exhaust gas and noise emission levels. To simultaneously reduce exhaust gas and noise emissions and to satisfy the increasing demand of electric power on board, optimization of the current technology is necessary. Prior to any possible demonstration of optimization potential, detailed data of thermodynamic properties and emissions have to be determined. Therefore, the investigations presented in this paper were conducted at a full-scale APU of an operational aircraft. A Pratt & Whitney APS3200, commonly installed in the Airbus A320 aircraft family, was used for measurements of the reference data. In order to describe the APS3200, the full spectrum of feasible power load and bleed air mass flow combinations were adjusted during the study. Their effect on different thermodynamic and performance properties, such as exhaust gas temperature, pressure as well as electric and overall efficiency is described. Furthermore, the mass flows of the inlet air, exhaust gas and fuel input were determined. Additionally, the work reports the exhaust gas emissions regarding the species CO 2 , CO and NOx as a function of load point. Moreover the acoustic noise emissions are presented and discussed. With the provided data the paper serves as a database for validating numerical simulations and provides a baseline for current APU technology.
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