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Machines, Volume 1, Issue 3 (December 2013), Pages 81-141

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Research

Open AccessArticle Pollutant Emission Validation of a Heavy-Duty Gas Turbine Burner by CFD Modeling
Machines 2013, 1(3), 81-97; doi:10.3390/machines1030081
Received: 17 June 2013 / Revised: 27 August 2013 / Accepted: 27 September 2013 / Published: 16 October 2013
Cited by 1 | PDF Full-text (736 KB) | HTML Full-text | XML Full-text
Abstract
3D numerical combustion simulation in a can burner fed with methane was carried out in order to evaluate pollutant emissions and the temperature field. As a case study, the General Electric Frame 6001B system was considered. The numerical investigation has been performed using
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3D numerical combustion simulation in a can burner fed with methane was carried out in order to evaluate pollutant emissions and the temperature field. As a case study, the General Electric Frame 6001B system was considered. The numerical investigation has been performed using the CFD code named ACE+ Multiphysics (by Esi-Group). The model was validated against the experimental data provided by Cofely GDF SUEZ and related to a real power plant. To completely investigate the stability of the model, several operating conditions were taken into account, at both nominal and partial load. In particular, the influence on emissions of some important parameters, such as air temperature at compressor intake and steam to fuel mass ratio, have been evaluated. The flamelet model and Zeldovich’s mechanism were employed for combustion modeling and NOx emissions, respectively. With regard to CO estimation, an innovative approach was used to compute the Rizk and Mongia relationship through a user-defined function. Numerical results showed good agreement with experimental data in most of the cases: the best results were obtained in the NOx prediction, while unburned fuel was slightly overestimated. Full article
(This article belongs to the Special Issue Advances in Control Engineering)
Open AccessArticle Reduced-Friction Passive Magnetic Bearing: Innovative Design and Novel Characterization Technique
Machines 2013, 1(3), 98-115; doi:10.3390/machines1030098
Received: 1 August 2013 / Revised: 1 October 2013 / Accepted: 3 October 2013 / Published: 28 October 2013
Cited by 1 | PDF Full-text (1574 KB) | HTML Full-text | XML Full-text
Abstract
Friction is mostly unwanted in rotating machines. In order to reduce its impact on the system, the integration of magnetic bearings is frequently regarded as a valid solution. In rotating systems like flywheel energy storage systems (FESS), mechanical losses created by mechanical bearings
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Friction is mostly unwanted in rotating machines. In order to reduce its impact on the system, the integration of magnetic bearings is frequently regarded as a valid solution. In rotating systems like flywheel energy storage systems (FESS), mechanical losses created by mechanical bearings greatly reduce the overall performance. Magnetic bearings are thus frequently integrated in FESS to eliminate mechanical losses. The simple design of passive magnetic bearings (PMBs), their inherent security, and their very low friction make them perfect candidates for FESS. The main objective, and most important contribution of this paper, is to document an innovative PMB that minimizes energy losses induced by the axial thrust bearing, and to document the methodology used to measure its stiffness and damping. Although PMBs are fairly well documented in literature, no other PMB is designed to reduce the friction generated by the thrust bearing. In order to promote their integration, it is critical to identify their mechanical properties such as stiffness and damping. Hence, another contribution of this paper is to propose a new way to easily characterize any magnetic bearing topology to replace available techniques that only provided the properties for a precise configuration of the bearing. The new technique provides an unprecedented mapping of the forces generated by complex combinations of permanent magnets. Experimental results show that the new PMB can be configured to effectively reduce the force applied to the thrust bearing, resulting in lower friction. This friction reduction is achieved while allowing the proper operation of the bearing. Results also show that the measured stiffness is different from those obtained analytically, suggesting that a magnetic bearing should always be characterized prior to its use. Full article
Open AccessArticle Calculating Restart States for Systems Modeled by Operations Using Supervisory Control Theory
Machines 2013, 1(3), 116-141; doi:10.3390/machines1030116
Received: 21 September 2013 / Revised: 4 November 2013 / Accepted: 12 November 2013 / Published: 4 December 2013
Cited by 5 | PDF Full-text (582 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a supervisory control theory based offline method for calculating restart states in a manufacturing control system. Given these precalculated restart states, an operator can be given correct instructions for how to resynchronize the control system and the manufacturing resources during
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This paper presents a supervisory control theory based offline method for calculating restart states in a manufacturing control system. Given these precalculated restart states, an operator can be given correct instructions for how to resynchronize the control system and the manufacturing resources during the online restart process. The proposed method enables restart after unforeseen errors. It is assumed that the control system is modeled by operations and that possible operation sequences emerge through dependencies between the operations. The paper shows how reexecution requirements may be included in the calculation to obtain a correct behavior for the restarted system. In addition, it is shown how to filter out restart states that require less effort for the operator during the online restart, and how to adapt the nominal production to always enable restart in desired restart states. Full article
(This article belongs to the Special Issue Advances and Challenges in Manufacturing Automation)
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