| 1. |
- Ahlgren, Fredrik, 1980-, et al.
(författare)
-
Energy integration of organic rankine cycle, exhaust gas recirculation and scrubber
- 2018
-
Ingår i: Trends and challenges in maritime energy management. - Cham, Switzerland : Springer. - 9783319745756 - 9783319745763 ; , s. 157-168
-
Bokkapitel (refereegranskat)abstract
- The vast majority of ships trafficking the oceans are fuelled by residual oil with high content of sulphur, which produces sulphur oxides (SOx) when combusted. Additionally, the high pressures and temperatures in modern diesel engines also produce nitrogen oxides (NOx). These emissions are both a hazard to health and the local environment, and regulations enforced by the International Maritime Organization (IMO) are driving the maritime sector towards the use of either distillate fuels containing less sulphur, or the use of exhaust gas cleaning devices.TwocommontechniquesforremovingSOx andlimitingNOx aretheopen loop wet scrubber and exhaust gas recirculation (EGR). A scrubber and EGR installation reduces the overall efficiency of the system as it needs significant pumping power, which means that the exhaust gases are cleaner but at the expense of higher CO2 emissions. In this paper we propose a method to integrate an exhaust gas cleaning device for both NOx and SOx with an organic Rankine cycle for waste heat recovery, thereby enhancing the system efficiency. We investigate three ORC configurations, integrated with the energy flows from both an existing state-of-the-art EGR system and an additional open loop wet scrubber.
|
|
| 2. |
- Ahlgren, Fredrik, 1980-, et al.
(författare)
-
Waste Heat Recovery in a Cruise Vessel in the Baltic Sea by Using an Organic Rankine Cycle : A Case Study
- 2015
-
Ingår i: ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. - : ASME Press. - 9780791856673 ; , s. 43392-43416
-
Konferensbidrag (refereegranskat)abstract
- Maritime transportation is a significant contributor to SOx, NOx and particle matter emissions, even though it has a quite low CO2 impact. New regulations are being enforced in special areas that limit the amount of emissions from the ships. This fact, together with the high fuel prices, is driving the marine industry towards the improvement of the energy efficiency of current ship engines and the reduction of their energy demand. Although more sophisticated and complex engine designs can improve significantly the efficiency of the energy systems in ships, waste heat recovery arises as the most influent technique for the reduction of the energy consumption. In this sense, it is estimated that around 50% of the total energy from the fuel consumed in a ship is wasted and rejected in fluid and exhaust gas streams. The primary heat sources for waste heat recovery are the engine exhaust and the engine coolant. In this work, we present a study on the integration of an organic Rankine cycle (ORC) in an existing ship, for the recovery of the main and auxiliary engines exhaust heat. Experimental data from the operating conditions of the engines on the M/S Birka Stockholm cruise ship were logged during a port-to-port cruise from Stockholm to Mariehamn over a period of time close to one month. The ship has four main engines Wärtsilä 5850 kW for propulsion, and four auxiliary engines 2760 kW used for electrical consumers. A number of six load conditions were identified depending on the vessel speed. The speed range from 12–14 knots was considered as the design condition, as it was present during more than 34% of the time. In this study, the average values of the engines exhaust temperatures and mass flow rates, for each load case, were used as inputs for a model of an ORC. The main parameters of the ORC, including working fluid and turbine configuration, were optimized based on the criteria of maximum net power output and compactness of the installation components. Results from the study showed that an ORC with internal regeneration using benzene would yield the greatest average net power output over the operating time. For this situation, the power production of the ORC would represent about 22% of the total electricity consumption on board. These data confirmed the ORC as a feasible and promising technology for the reduction of fuel consumption and CO2 emissions of existing ships.
|
|
| 3. |
- Ahlgren, Fredrik, 1980-, et al.
(författare)
-
Waste Heat Recovery in a Cruise Vessel in the Baltic Sea by Using an Organic Rankine Cycle : A Case Study
- 2016
-
Ingår i: Journal of engineering for gas turbines and power. - : ASME Press. - 0742-4795 .- 1528-8919. ; 138:1
-
Tidskriftsartikel (refereegranskat)abstract
- Maritime transportation is a significant contributor to SOx,NOx, and particle matter (PM) emissions, and to a lesser extent, of CO2. Recently, new regulations are being enforced in special geographical areas to limit the amount of emissions from the ships. This fact, together with the high fuel prices, is driving the marine industry toward the improvement of the energy efficiency of ships. Although more sophisticated and complex engine designs can improve significantly of the energy systems on ships, waste heat recovery arises as the most effective technique for the reduction of the energy consump- tion. In this sense, it is estimated that around 50% of the total energy from the fuel con- sumed in a ship is wasted and rejected through liquid and gas streams. The primary heat sources for waste heat recovery are the engine exhaust and coolant. In this work, we present a study on the integration of an organic Rankine cycle (ORC) in an existing ship, for the recovery of the main and auxiliary engines (AE) exhaust heat. Experimental data from the engines on the cruise ship M/S Birka Stockholm were logged during a port-to- port cruise from Stockholm to Mariehamn, over a period of 4 weeks. The ship has four main engines (ME) W€artsil€ a 5850kW for propulsion, and four AE 2760kW which areused for electrical generation. Six engine load conditions were identified depending on the ship’s speed. The speed range from 12 to 14 kn was considered as the design condi- tion for the ORC, as it was present during more than 34% of the time. In this study, the average values of the engines exhaust temperatures and mass flow rates, for each load case, were used as inputs for a model of an ORC. The main parameters of the ORC, including working fluid and turbine configuration, were optimized based on the criteria of maximum net power output and compactness of the installation components. Results from the study showed that an ORC with internal regeneration using benzene as working fluid would yield the greatest average net power output over the operating time. For this situation, the power production of the ORC would represent about 22% of the total elec- tricity consumption on board. These data confirmed the ORC as a feasible and promisingtechnology for the reduction of fuel consumption and CO2 emissions of existing ships.
|
|
| 4. |
- Anton, Nicholas, et al.
(författare)
-
AXIAL TURBINE DESIGN FOR A TWIN-TURBINE HEAVY-DUTY TURBOCHARGER CONCEPT
- 2018
-
Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO. - : ASME Press. - 9780791851005
-
Konferensbidrag (refereegranskat)abstract
- In the process of evaluating a parallel twin-turbine pulse-turbocharged concept, the results considering the turbine operation clearly pointed towards an axial type of turbine. The radial turbine design first analyzed was seen to suffer from sub-optimum values of flow coefficient, stage loading and blade speed-ratio. Modifying the radial turbine by both assessing the influence of "trim" and inlet tip diameter all concluded that this type of turbine is limited for the concept. Mainly, the turbine stage was experiencing high values of flow coefficient, requiring a more high flowing type of turbine. Therefore, an axial turbine stage could be feasible as this type of turbine can handle significantly higher flow rates very efficiently. Also, the design spectrum is broader as the shape of the turbine blades is not restricted by a radially fibred geometry as in the radial turbine case. In this paper, a single stage axial turbine design is presented. As most turbocharger concepts for automotive and heavy-duty applications are dominated by radial turbines, the axial turbine is an interesting option to be evaluated for pulse charged concepts. Values of crank-angle-resolved turbine and flow parameters from engine simulations are used as input to the design and subsequent analysis. The data provides a valuable insight into the fluctuating turbine operating conditions and is a necessity for matching a pulse-turbocharged system. Starting on a 1D-basis, the design process is followed through, resulting in a fully defined 3D-geometry. The 3D-design is evaluated both with respect to FEA and CFD as to confirm high performance and durability. Turbine maps were used as input to the engine simulation in order to assess this design with respect to "on-engine" conditions and to engine performance. The axial design shows clear advantages with regards to turbine parameters, efficiency and tip speed levels compared to a reference radial design. Improvement in turbine efficiency enhanced the engine performance significantly. The study concludes that the proposed single stage axial turbine stage design is viable for a pulse-turbocharged six cylinder heavy-duty engine. Taking into account both turbine performance and durability aspects, validation in engine simulations, a highly efficient engine with a practical and realizable turbocharger concept resulted.
|
|
| 5. |
- Anton, Nicholas
(författare)
-
Engine Optimized Turbine Design
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The focus on our environment has never been as great as it is today. The impact of global warming and emissions from combustion processes become increasingly more evident with growing concerns among the world’s inhabitants. The consequences of extreme weather events, rising sea levels, urban air quality, etc. create a desperate need for immediate action. A major contributor to the cause of these effects is the transportation sector, a sector that relies heavily on the internal combustion engine and fossil fuels. The heavy-duty segment of the transportation sector is a major consumer of oil and is responsible for a large proportion of emissions.The global community has agreed on multiple levels to reduce the effect of man-made emissions into the atmosphere. Legislation for future reductions and, ultimately, a totally fossil-free society is on the agenda for many industrialized countries and an increasing number of emerging economies.Improvements of the internal combustion engine will be of importance in order to effectively reduce emissions from the transportation sector both presently and in the future. The primary focus of these improvements is undoubtedly in the field of engine efficiency. The gas exchange system is of major importance in this respect. The inlet and exhaust flows as the cylinder is emptied and filled will significantly influence the pumping work of the engine. At the center of the gas exchange system is the turbocharger. The turbine stage of the turbocharger can utilize the energy in the exhaust flow by expanding the exhaust gases in order to power the compressor stage of the turbocharger.If turbocharger components can operate at high efficiency, it is possible to achieve high engine efficiency and low fuel consumption. Low exhaust pressure during the exhaust stroke combined with high pressure at the induction stroke results in favorable pumping work. For the process to work, a systems-based approach is required as the turbocharger is only one component of the engine and gas exchange system.In this thesis, the implications of turbocharger turbine stage design with regards to exhaust energy utilization have been extensively studied. Emphasis has been placed on the turbine stage in a systems context with regards to engine performance and the influence of exhaust system components.The most commonly used turbine stage in turbochargers, the radial turbine, is associated with inherent limitations in the context of exhaust energy utilization. Primarily, turbine stage design constraints result in low efficiency in the pulsating exhaust flow, which impairs the gas exchange process. Gas stand and numerical evaluation of the common twin scroll radial turbine stage highlighted low efficiency levels at high loadings. For a pulse-turbocharged engine with low exhaust manifold volume, the majority of extracted work by the turbine will occur at high loadings, far from the optimum efficiency point for radial turbines. In order for the relevant conditions to be assessed with regards to turbine operation, the entire exhaust pulse must be considered in detail. Averaged conditions will not capture the variability in energy content of the exhaust pulse important for exhaust energy utilization.Modification of the radial turbine stage design in order to improve performance is very difficult to achieve. Typical re-sizing with modifying tip diameter and trim are not adequate for altering turbine operation into high efficiency regions at the energetic exhaust pulse peak.The axial turbine type is an alternative as a turbocharger turbine stage for a pulse-turbocharged engine. The axial turbine stage design can allow for high utilization of exhaust energy with minimal pressure interference in the gas exchange process; a combination which has been shown to result in engine efficiency improvements compared to state-of-the-art radial turbine stages.
|
|
| 6. |
- Anton, Nicholas, et al.
(författare)
-
Exhaust volume dependency of turbocharger turbine design for a heavy duty otto cycle engine
- 2017
-
Ingår i: Proceedings of the ASME Turbo Expo. - : ASME Press. - 9780791850800
-
Konferensbidrag (refereegranskat)abstract
- This study is considering turbocharger turbine performance at "on-engine" conditions with respect to turbine design variables and exhaust manifold volume. The highly unsteady nature of the internal combustion engine will result in a very wide range of turbine operation, far from steady flow conditions. As most turbomachinery design work is conducted at steady state, the influence of the chosen turbine design variables on the crank-angle-resolved turbine performance will be of prime interest. In order to achieve high turbocharger efficiency with the greatest benefits for the engine, the turbine will need high efficiency at the energetic exhaust pressure pulse peak. The starting point for this paper is a target full load power curve for a heavy duty Otto-cycle engine, which will dictate an initial compressor and turbine match. Three radial turbine designs are investigated, differing with respect to efficiency characteristics, using a common compressor stage. The influence of the chosen turbine design variables considering a main contributor to unsteadiness, exhaust manifold volume, is evaluated using 1D engine simulation software. A discussion is held in conjunction with this regarding the efficiency potential of each turbine design and limitations of turbine types.
|
|
| 7. |
- Anton, Nicholas, et al.
(författare)
-
ON THE CHOICE OF TURBINE TYPE FOR A TWIN-TURBINE HEAVY-DUTY TURBOCHARGER CONCEPT
- 2018
-
Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO. - : AMER SOC MECHANICAL ENGINEERS. ; 8
-
Konferensbidrag (refereegranskat)abstract
- In this study, a fundamental approach to the choice of turbocharger turbine for a pulse-charged heavy-duty diesel engine is presented. A standard six-cylinder engine build with a production exhaust manifold and a Twin-scroll turbocharger is used as a baseline case. The engine exhaust configuration is redesigned and evaluated in engine simulations for a pulse-charged concept consisting of a parallel twin-turbine layout. This concept will allow for pulse separation with minimized exhaust pulse interference and low exhaust manifold volume. This turbocharger concept is uncommon, as most previous studies have considered two stage systems, various multiple entry turbine stages etc. Even more rare is the fundamental aspect regarding the choice of turbine type as most manufacturers tend to focus on radial turbines, which by far dominate the turbochargers of automotive and heavy-duty applications. By characterizing the turbine operation with regards to turbine parameters for optimum performance found in literature a better understanding of the limitations of turbine types can be achieved. A compact and low volume exhaust manifold design is constructed for the turbocharger concept and the reference radial turbine map is scaled in engine simulations to a pre-set AFR-target at a low engine RPM. By obtaining crank-angle-resolved data from engine simulations, key turbine parameters are studied with regard to the engine exhaust pulse-train. At the energetic exhaust pressure pulse peak, the reference radial turbine is seen to operate with suboptimum values of Blade-Speed-Ratio, Stage Loading and Flow Coefficient. The study concludes that in order to achieve high turbine efficiency for this pulse-charged turbocharger concept, a turbine with efficiency optimum towards low Blade-Speed Ratios, high Stage Loading and high Flow Coefficient is required. An axial turbine of low degree of reaction-design could be viable in this respect.
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
- Bahrami, Saeed, et al.
(författare)
-
Performance Comparison between Steam Injected Gas Turbine and Combined Cycle during Frequency Drops
- 2015
-
Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 8:8, s. 7582-7592
-
Tidskriftsartikel (refereegranskat)abstract
- Single-shaft gas turbine and its cycles are sensitive to frequency drops and, therefore, sudden change loads or large frequency dips might affect their stability. This phenomenon is related to the reduction of the air mass flow passing through the machine during the frequency dips, which might lead to an interaction between governor and temperature control loop. In this paper, the performance of the combined cycle and steam-injected gas turbine are studied during frequency dips and transient maneuvers. For this purpose, two similar units are developed based on these cycles and their performances are studied in different scenarios. The simulation results show that the steam injected gas turbine has a better performance during frequency drops and it can handle relatively larger change loads.
|
|
| 11. |
- Dahlquist, Adrian, et al.
(författare)
-
Aerodynamic turbine design for an oxy-fuel combined cycle
- 2016
-
Ingår i: Turbomachinery. - 9780791849705 ; 2B-2016
-
Konferensbidrag (refereegranskat)abstract
- The oxy-fuel combined cycle (OCC) is one of several carbon capture and sequestration (CCS) technologies being developed to reduce CO2 emissions from thermal power plants. The OCC consists of a semi-closed topping Bryton cycle, and a traditional bottoming Rankine cycle. The topping cycle operates with a working medium mixture of mainly CO2 and H2O. This CO2-rich working fluid has significantly different gas properties compared to a conventional open gas turbine cycle, which thereby affects the aerodynamic turbine design for the gas turbine units. The aerodynamic turbine design for oxyfuel gas turbines is an unexplored research field. The topic of this study was therefore to investigate the aerodynamic turbine design of turbines operating with a CO2-rich working fluid. The investigation was performed through a typical turbine aerodesign loop, which covered the 1D mid-span, 2D through-flow, 3D blade profiling design and the steady-state 3D analysis. The design was performed through the use of conventional design methods and criteria in order to investigate if any significant departures from conventional turbine design methods were required. The survey revealed some minor deviations in design considerations, yet it showed that the design is feasible with today's state-of-the-art technology by using conventional design practice and methods. The performance of the oxy-fuel combined cycle was revised based on the performance figures from the components design. The expected total performance figures for the oxy-fuel combined cycle were calculated to be a net electrical power of 119.9 MW and a net thermal efficiency of 48.2%. These figures include the parasitic consumption for the oxygen production required for the combustion and the CO2 compression of the CO2 bleed stream.
|
|
| 12. |
- Deshpande, Srikanth, et al.
(författare)
-
Effect of spanwise variation of chord on the performance of a turbine cascade
- 2017
-
Ingår i: Turbomachinery. - 9780791850787 ; 2A-2017
-
Konferensbidrag (refereegranskat)abstract
- This paper compares the aerodynamic performance of two cascade designs, viz.: -constant-chord and varying-chord. The varying-chord design is typical of industrial gas turbines and steam turbine stators in order to reduce manufacturing costs. The present study aims to increase the understanding of the implications of this manufacturing constraint on the aerodynamics of the stator. Experiments are carried out in a linear cascade wind tunnel. Numerical simulations are performed using commercial code CFX. The profile losses and secondary losses in the two designs are compared. The overall total pressure losses indicate better aerodynamic performance of a turbine cascade with constant chord as compared to a turbine cascade of varying-chord design
|
|
| 13. |
- Deshpande, Srikanth, et al.
(författare)
-
Efficiency improvements in an industrial steam turbine stage - Part 1
- 2016
-
Ingår i: Turbomachinery. - 9780791849705 ; 2B-2016
-
Konferensbidrag (refereegranskat)abstract
- The present work approaches the idea of increasing the efficiency of an industrial steam turbine stage. For this endeavor, an industrial steam turbine stage comprising of prismatic stator and rotor is considered. With the velocity triangles as input, airfoil design is carried out. Firstly, the rotor is redesigned to take care of any incidence issues in the baseline case. In rotor blades, the peak Mach number is reduced in blade to blade flow passage and hence, efficiency of stage is increased. Rotor is made front loaded. After finalizing the rotor, the stator is redesigned. Stator is made more aft-loaded when compared to the baseline case. By making the stator aft-loaded, the efficiency increased by reducing profile losses. This design modification also showed advantage in secondary losses. The total pressure loss in the stator was reduced by a delta of 0.15. When creating an airfoil for stator or rotor, MISES was used in order to evaluate profile losses. The design verification for the stage was numerically done using commercial CFD software ANSYS CFX. Steady state RANS simulations were carried out. The stator and the rotor still being prismatic, only by virtue of airfoil design, the total to total stage efficiency improvement of 0.33% was predicted.
|
|
| 14. |
- Deshpande, Srikanth, et al.
(författare)
-
Efficiency improvements in an industrial steam turbine stage - Part 2
- 2016
-
Ingår i: Turbomachinery. - 9780791849705 ; 2B-2016
-
Konferensbidrag (refereegranskat)abstract
- Improvement in isentropic total to total efficiency of a low reaction turbine stage by airfoil redesign was considered in first part of the paper. Further, modifications in the flow path of the baseline stage is considered in second part of the paper. Flow path of the baseline stage incorporates axisymmetric meridional endwall contour(commonly called Russian kink). For a stage comprising of high aspect ratio blades, assessment of performance with endwall contour is performed. Alternatives, if required for endwall contour had to be explored and numerically verified. Endeavor in the present paper is in this direction. Static pressure distribution at the stator exit is considered as the main objective. Along with flow path modification, stator modifications like vortexing and lean are attempted to obtain stator exit static pressure distribution similar to baseline case. Straight lean on stator provides good results in terms of reducing stator exit pressure gradient as well as reducing gradient of rotor inlet swirl. Since the pressure distribution at stator exit also drives the tip leakage flow, effect of flowpath and stator modifications on tip leakage flow is studied. Performance numbers are reported for cases with and without tip shroud.
|
|
| 15. |
- Deshpande, Srikanth, et al.
(författare)
-
Influence of compound lean on an industrial steam turbine stage
- 2015
-
Ingår i: ASME 2015 Gas Turbine India Conference, GTINDIA 2015. - 9780791857311
-
Konferensbidrag (refereegranskat)abstract
- Compound lean implemented on stator of an industrial steam turbine stage in order to reduce secondary losses are discussed. Baseline stator is a prismatic vane with aspect ratio of unity. Compound lean stator blade is designed by shearing the airfoil sections in tangential direction. Modifications are analyzed numerically using commercial code CFX. Three blade rows i.e. one complete stage with a downstream stator are analyzed. Steady state Reynolds averaged Navier Stokes equations are solved. Total pressure loss (TPL) is used as objective function to monitor reduction in secondary losses. Rotor is retained the same for baseline as well as compound leaned stator. Results show reduction in total pressure loss of stator in excess of 5%. Also, computations of coefficient of secondary kinetic energy shows significant reduction in secondary losses in excess of 30% in stator. Efficiency gained by implementation of compound lean are discussed.
|
|
| 16. |
- Deshpande, Srikanth, et al.
(författare)
-
Vortexing methods to reduce secondary losses in a low reaction industrial turbine
- 2015
-
Ingår i: Turbomachinery. - 9780791856635 ; 2A
-
Konferensbidrag (refereegranskat)abstract
- Vortexing methods implemented on an industrial steam turbine vane in order to reduce secondary losses are discussed. Three vortexing methods presented are prismatic blade design, inverse vortex and parabolic forced vortex. Baseline industrial vane considered for study is a prismatic blade design. Modifications are analysed numerically using commercial code CFX. Modified vanes along with baseline rotor as a complete stage is considered for analysis. Steady state Reynolds averaged Navier Stokes equations are solved. Total pressure loss (TPL) is used as target functions to monitor reduction in secondary losses. Rotor considered for the study is the baseline industrial rotor for all design modifications of vane.
|
|
| 17. |
- Lejon, Marcus, 1986, et al.
(författare)
-
Multidisciplinary Design of a Three Stage High Speed Booster
- 2017
-
Ingår i: ASME Turbo Expo 2017: Turbine Technical Conference and Exposition. - : ASME Press. ; 2B-2017
-
Konferensbidrag (refereegranskat)abstract
- The paper describes a multidisciplinary conceptual design of an axial compressor, targeting a three stage, high speed, high efficiency booster with a design pressure ratio of 2.8. The paper is outlined in a step wise manner starting from basic aircraft and engine thrust requirements, establishing the definition of the high speed booster interface points and its location in the engine. Thereafter, the aerodynamic 1D/2D design is carried out using the commercial throughflow tool SC90C. A number of design aspects are described, and the steps necessary to arrive at the final design are outlined. The SC90C based design is then carried over to a CFD based conceptual design tool AxCent, in which a first profiling is carried out based on a multiple circular arc blade definition. The design obtained at this point is referred to as the VINK compressor. The first stage of the compressor is then optimized using an in-house optimization tool, where the objective functions are evaluated from detailed CFD calculations. The design is improved in terms of efficiency and in terms of meeting the design criteria put on the stage in the earlier design phases. Finally, some aeromechanical design aspects of the first stage are considered. The geometry and inlet boundary conditions of the compressor are shared with the turbomachinery community on a public server. This is intended to be used as a test case for further optimization and analysis.
|
|
| 18. |
- Lundbladh, Anders, 1964, et al.
(författare)
-
High Power Density Work Extraction from Turbofan Exhaust Heat
- 2015
-
Ingår i: ISABE-2015-20101.
-
Konferensbidrag (refereegranskat)abstract
- Integration of steam and air bottoming cycles with a conventional transport category turbofan is discussed. A conceptual design of a turbofan with a steam bottoming cycle yielded a 5% efficiency improvement for realistic component performance, but the weight eliminated in principal all gain on an aircraft level. For an air bottoming cycle simplified core cycle simulations showed the potential for up to 8% efficiency improvement. A novel Exhaust Heated Bleed engine where the bottoming cycle is integrated with a conventional turbofan turbo machinery is proposed. Simulation of this engine for take-off, climb and cruise conditions shows a 3-7% efficiency benefit. A concept for an exhaust heat exchanger and a conceptual turbine design for the Bleed Turbine to convert the exhaust heat to shaft power are illustrated.
|
|
| 19. |
- Mondejar, Maria E., et al.
(författare)
-
Quasi-steady state simulation of an organic Rankine cycle for waste heat recovery in a passenger vessel
- 2017
-
Ingår i: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 185:Special Issue Part 2, s. 1324-1335
-
Tidskriftsartikel (refereegranskat)abstract
- In this work we present the quasi-steady state simulation of a regenerative organic Rankine cycle (ORC)integrated in a passenger vessel, over a standard round trip. The study case is the M/S Birka Stockholmcruise ship, which covers a daily route between Stockholm (Sweden) and Mariehamn (Finland).Experimental data of the exhaust gas temperatures, engine loads, and electricity demand on board werelogged over a period of four weeks. These data where used as inputs for a simulation model of an ORC forwaste heat recovery of the exhaust gases. A quasi-steady state simulation was carried out on an offdesignmodel, based on optimized design conditions, to estimate the average net power production ofthe ship over a round trip. The maximum net power production of the ORC during the round trip wasestimated to supply approximately 22% of the total power demand on board. The results showed apotential for ORC as a solution for the maritime transport sector to accomplish the new and morerestrictive regulations on emissions, and to reduce the total fuel consumption.
|
|
| 20. |
- Mondejar, Maria, et al.
(författare)
-
Study of the on-route operation of a waste heat recovery system in a passenger vessel
- 2015
-
Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 75, s. 1646-1653, s. 1646-1653
-
Tidskriftsartikel (refereegranskat)abstract
- Waste heat recovery systems for power generation are gaining interest among the marine transport sector as a solution to accomplish the upcoming more restrictive regulations on emissions, and to reduce the total fuel consumption. In this paper we evaluate how a waste heat recovery system based on a regenerative organic Rankine cycle (rORC) could improve the performance of a passenger vessel. The case study is based on the M/S Birka Stockholm cruise ship, which covers a daily route between Stockholm (Sweden) and Mariehamn (Finland). Experimental data on exhaust gas temperatures, fuel consumption and electricity demand on board were logged for a period of four weeks. Based on the results of a fluid and configuration optimization performed in a previous work, an off-design model of a rORC working with benzene was used to estimate the net power production of the rORC at the different load conditions during a port-to-port trip of the vessel. The power generation curve of the rORC over time was compared to that of the electricity demand of the ship. Results showed that the rORC could provide up to 16 % of the total power demand. However, this value should be corrected if the auxiliary engines load is reduced as a consequence of the partial coverage of the electricity demand by the ORC.
|
|
| 21. |
- Sammak, Majed, et al.
(författare)
-
Performance of a Semi-Closed Oxy-Fuel Combustion Combined Cycle (scoc-cc) with an Air Separation Unit (ASU)
- 2018
-
Ingår i: Coal, Biomass, and Alternative Fuels; Cycle Innovations; Electric Power; Industrial and Cogeneration; Organic Rankine Cycle Power Systems. - 9780791851043 ; 3
-
Konferensbidrag (refereegranskat)abstract
- The objective of this paper is to evaluate the performance of a semi-closed oxy-fuel combustion combined cycle (SCOC-CC) and its power penalties. The power penalties are associated with CO2 compression and high-pressure oxygen production in the air separation unit (ASU). The paper discusses three different methods for high pressure oxygen (O2) production. Method 1 is producing O2 directly at high pressure by compressing the air before the air separation takes place. Method 2 is producing O2 at low pressure and then compressing the separated O2 to the desired pressure with a compressor. Method 3 is alike the second method, except that the separated liquid O2 is pressurized with a liquid oxygen pump to the desired pressure. The studied SCOC-CC is a dual-pressure level steam cycle due to its comparable efficiency with three pressure level steam cycle and less complexity. The SCOC-CC, ASU and CO2 compression train are modeled with the commercial heat and mass balance software IPSEpro. The paper analyzed the SCOC-CC performance at different combustion outlet temperatures and pressure ratios. The combustion outlet temperature (COT) varied from 1200 °C to 1550 °C and the pressure ratio varied from 25 to 45. The study is concerned with mid-sized SCOC-CC with a net power output 100 MW. The calculations were performed at the selected design point which was at 1400°C and pressure ratio at 37. The calculated power consumption of the O2 separation at a purity of 95 % was 719 kJ/kgO2. The power consumption for pressurizing the separated O2 (method 2) was 345 kJ/kgO2 whereas it was 4.4 kJ/kgO2 for pumping liquid O2 to the required pressure (method 3). The calculated power consumption for pressurizing and pumping the CO2-enriched stream was 323 kJ/kgCO2. The SCOC-CC gross efficiency was 57.6 %. The SCOCCC net efficiency at method 2 for air separation was 46.7 %. The gross efficiency was reduced by 9 % due to ASU and other 2 % due to CO2 compression. The SCOC-CC net efficiency at method 3 of the air separation was 49.6 %. The ASU reduced the gross efficiency by 6 % and additional 2 % by CO2 compression. Using method 3 for air separation gave a 3 % gain in cycle efficiency.
|
|
| 22. |
- Topel, Monika, 1988-
(författare)
-
Improving Concentrating Solar Power Plant Performance through Steam Turbine Flexibility
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The amount of incoming solar energy to earth is greater than any other source. Among existing technologies to harness solar energy there is concentrating solar power (CSP). One advantage of CSP is that is dispatchable, meaning that it can provide power even when the sun is not shining. However, CSP is undergoing challenges which hinder its development such as operating variabilities caused by the fluctuations of the sun or the fact that these systems are not yet cost competitive with respect to other technologies. One way of improving the performance of CSP plants (CSPPs) is by increasing their operational flexibility, specifically their capability for fast starts. In this way it is possible for the CSPP to harness the solar energy as soon as possible, thus producing more energy and increasing its profitability. Over 90% of CSPPs use a steam turbine to generate electricity. Steam turbines are not currently designed with the flexibility required by the CSP application. Steam turbine start-up is limited by thermal stress and differential expansion. If not carefully controlled, these phenomena either consume lifetime or even result in machine failure.The aim of this work was to understand the improvement potential of steam turbine start-up and quantify this in terms of CSPP performance indicators. For this, a thermo-mechanical steam turbine model was developed and validated. The model was then used to analyze potential improvements and thermal constraints to steam turbine start-up operation. Furthermore, a CSP plant techno-economic model was developed including steam turbine details. This modeling approach including two levels of detail allowed for the particularities of the component to be included within the dynamics of the plant and thus be able to connect the perspectives of the equipment manufacturer with those of the plant operator. Reductions of up to 11.4% in the cost of electricity were found in the studies carried out.
|
|
| 23. |
- Topel, Monika, 1988-, et al.
(författare)
-
Operational Improvements for Startup Time Reduction in Solar Steam Turbines
- 2015
-
Ingår i: Journal of engineering for gas turbines and power. - : ASME Press. - 0742-4795 .- 1528-8919. ; 137:4
-
Tidskriftsartikel (refereegranskat)abstract
- Solar steam turbines are subject to high thermal stresses as a result of temperature gradients during transient operation, which occurs more frequently due to the variability of the solar resource. In order to increase the flexibility of the turbines while preserving lifting requirements, several operational modifications for maintaining turbine temperatures during offline periods are proposed and investigated. The modifications were implemented in a dynamic thermal turbine model and the potential improvements were quantified. The modifications studied included: increasing the gland steam pressure injected to the end-seals, increasing the back pressure and increasing the barring speed. These last two take advantage of the ventilation and friction work. The effects of the modifications were studied both individually as well as in different combinations. The temperatures obtained when applying the combined modifications were compared to regular turbine cool-down (CD) temperatures and showed significant improvements on the startup times of the turbine.
|
|
| 24. |
- Topel, Monika, et al.
(författare)
-
Thermo-Economic Study on the Implementation of Steam Turbine Concepts for Flexible Operation on a Direct Steam Generation Solar Tower Power Plant
- 2016
-
Ingår i: SOLARPACES 2015. - : American Institute of Physics (AIP). - 9780735413863
-
Konferensbidrag (refereegranskat)abstract
- Among concentrating solar power technologies, direct steam generation solar tower power plants represent a promising option. These systems eliminate the usage of heat transfer fluids allowing for the power block to be run at greater operating temperatures and therefore further increasing the thermal efficiency of the power cycle. On the other hand, the current state of the art of these systems does not comprise thermal energy storage as there are no currently available and techno-economically feasible storage integration options. This situation makes direct steam generation configurations even more susceptible to the already existing variability of operating conditions due to the fluctuation of the solar supply. In the interest of improving the annual performance and competitiveness of direct steam generation solar tower systems, the present study examines the influence of implementing two flexibility enhancing concepts which control the steam flow to the turbine as a function of the incoming solar irradiation. The proposed concepts were implemented in a reference plant model previously developed by the authors. Then, a multi-objective optimization was carried out in order to understand which configurations of the steam turbine concepts yield reductions of the levelized cost of electricity at a lower investment costs when compared to the reference model. Results show that the implementation of the proposed strategies can enhance the thermo-economic performance of direct steam generation systems by yielding a reduction of up to 9.2% on the levelized cost of electricity, mainly due to allowing 20% increase in the capacity factor, while increasing the investment costs by 7.8%.
|
|
| 25. |
- Vaccarelli, Maura, et al.
(författare)
-
Combined cycle power plants with post-combustion CO2 capture : Energy analysis at part load conditions for different HRSG configurations
- 2016
-
Ingår i: Energy. - : Elsevier BV. - 0360-5442. ; 112, s. 917-925
-
Tidskriftsartikel (refereegranskat)abstract
- The part-load behaviour of combined cycle power plants (CCPP) equipped with post-combustion CO2 capture is analyzed. Different CCPP configurations are compared, including single-, dual- or triple-pressure level steam generators. The gas turbine is a single shaft unit using the variable guide vanes and fuel flow to control the load. The 90% CO2 capture is achieved using monoethanolamine (MEA 30%wt) as absorbent. In all configurations, the reboiler duty to regenerate the absorbent is partly covered by the hot water of the economizer. This economizer-reboiler loop allows to increase the plant efficiency as the possibility to extract more energy from the economizer results in lowering the steam extraction from the turbine. The dual-pressure level CCPP with CO2 capture gives the best efficiency at the design operation. As the load is reduced, the efficiency of the single-pressure plant becomes comparable to the efficiency of the dual-pressure plant, due to the effective thermal integration between the heat recovery steam generator and the absorbent regeneration process. Hence, when CCPPs with CO2 capture operate at part-loads, a further benefit can be achieved with the single-pressure level plant, having it both design simplicity and low efficiency penalties for the CO2 capture.
|
|
