| 1. |
- Duwig, Christophe, et al.
(författare)
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Efficient operation of a gas turbine on methanol using chemical recuperation
- 2012
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Ingår i: ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. ; 1, s. 615-623
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Konferensbidrag (refereegranskat)abstract
- Environmental and political concerns, together with new legislations, are pushing for a fuel shift in the power industry and more generally for many thermal applications. Adding to the coming decrease of oil and natural availability (or price increase), it opens avenues for new fuels. Among those, alcohols are strong candidates. In fact, short alcohols are easily produced and stored and require only moderate modifications of existing combustion systems. For example, operating an existing gas turbine (GT) on methanol requires moderate modifications (mainly in the combustion system). However, methanol can be used more efficiently. Unlike methane or other hydrocarbons that decompose at high temperature (1000K), methanol undergoes an endothermic decomposition at low temperatures (400K to 600K) to give CO and H2. It therefore opens avenue for coupling the GT with a chemical recuperation system. In other words, the methanol will be cracked using the waste heat of the flue gases with a gain in fuel heating value hence the original fuel is thermally upgraded. The present study will investigate the upgraded fuel combustion properties. The laminar flame speed of the upgraded fuel/air mixtures will be presented and compared to methane and methanol under conditions relevant to GT combustion. Several upgraded fuel compositions will be considered depending on the water content in the feed methanol. Further, we consider a recuperated micro GT (Turbec T100) based cycle fueled with methanol. The numerical study focuses on different thermodynamic cycles. Firstly, a reference case is considered assuming a direct fueled GT. Further, cycles including the cracker are studied keeping the power constant. The fuel efficiency gain due to the cracker will be investigated as function of the water content in the feed methanol. Finally, a case including CO2-removal will be presented and it will be shown that the cracker enables an efficient carbon capture and sequestration scheme.
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| 2. |
- Narayanan, Prakash, et al.
(författare)
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A Comparative Analysis of WHR System in HD Engines Using Conventional Diesel Combustion and Partially-Premixed Combustion
- 2012
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Ingår i: SAE Technical Paper Series. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
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Konferensbidrag (refereegranskat)abstract
- In the truck industry there is a continuous demand to increase the efficiency and to decrease the emissions. To acknowledge both these issues a waste heat recovery system (WHR) is combined with a partially premixed combustion (PPC) engine to deliver an efficient engine system. Over the past decades numerous attempts to increase the thermal efficiency of the diesel engine has been made. One such attempt is the PPC concept that has demonstrated potential for substantially increased thermal efficiency combined with much reduced emission levels. So far most work on increasing engine efficiency has been focused on improving the thermal efficiency of the engine while WHR, which has an excellent potential for another 1-5 % fuel consumption reduction, has not been researched that much yet. In this paper a WHR system using a Rankine cycle has been developed in a modeling environment using IPSEpro. A comparative investigation of the WHR potential between the existing conventional diesel combustion and the novel PPC combustion is done. Even though the PPC is a low temperature combustion concept (LTC), implying that the exhaust temperatures are lower than for the traditional diesel combustion, the EGR quantity is higher which in total still offers improved WHR potential as that of conventional combustion. The EGR cooler offers higher quality heat when compared to exhaust gas and CAC, hence the WHR potential using only the EGR system is considered in this paper.
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| 3. |
- Nyberg, Björn, et al.
(författare)
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Aerodynamic Analysis of a Humid Air Turbine Expander
- 2012
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Ingår i: ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. ; 3, s. 217-225
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Konferensbidrag (refereegranskat)abstract
- This paper presents a reduced-order through-flow expander design for the Humid Air Turbine (HAT) also called the Evaporative Gas Turbine (EvGT). The HAT cycle is an innovative gas turbine cycle that uses humid air to enhance efficiency and power output. This means that there will be a higher water vapour content in the exhaust gases than for a simple cycle. This high water content affects the design of the HAT expander. The design of a wet expander is presented and compared with the results obtained with an expander working under dry exhaust gas conditions. The study was conducted using the reduced-order turbine design tool LUAX-T, developed at Lund University, which is freely available for academic use upon request. LUAX-T allows a flow-path analysis of the expander by specifying important flow-path parameters such as blade root stress and wall-hade angle. The HAT cycle enables cooling flow to the expander under different conditions and design differences for three different options are presented. The first cooling air bleeding point evaluated is the original position, where air is bled from the compressor discharge. The second position is just before the humidification tower, where the air has been cooled down to a low temperature. The third position is just after the humidification tower, where the air has been humidified thus changing its thermodynamic properties. Results in this paper shows that there is a need for an additional turbine stage in a humid expander compared to a dry expander. There are also results indicating that the compressor power can be reduced depending on which cooling strategy is used which can yield an increased total efficiency for a HAT cycle.
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| 4. |
- Nyberg, Björn, et al.
(författare)
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Thermodynamic studies of a HAT cycle and its components
- 2012
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Ingår i: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 89:1, s. 315-321
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Tidskriftsartikel (refereegranskat)abstract
- The electric power grid contains more and more renewable power production such as wind and solar power. The use of renewable power sources increases the fluctuations in the power grid which increase the demand for highly efficient, fast-starting power-producing units that can cope with sudden production losses. One of the more innovative power plant cycles, that have the potential of competing with conventional combined power plants in efficiency but has a higher availability and faster start up time, is the Evaporative Gas Turbine (EvGT) or Humid Air Turbine (HAT). A thermodynamic evaluation of different HAT cycle layouts has been done in this paper. Each layout is evaluated separately which makes it possible to study different components individual contribution to the efficiency and specific power. The thermodynamic evaluation also shows that it is important to look at different cool-flow extracting positions. The effect of water temperature entering the cycle, called make-up water, and where it is introduced into the cycle has been evaluated. The make-up water temperature also affects the optimal pressure level for intercooling and it is shown that an optimal position can be decided considering design parameters of the compressor and the water circuit. (C) 2011 Elsevier Ltd. All rights reserved.
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| 5. |
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