Wolfgang Sanz

Thermodynamic and Economic Investigation of an Improved Graz Cycle Power Plant for CO2 Capture

Introduction of closed-cycle gas turbines with their capability of retaining combustion generated CO 2 can offer a valuable contribution to the Kyoto goal and to future power generation. Therefore, research and development at Graz University of Technology since the 1990s has lead to the Graz Cycle, a zero emission power cycle of highest efficiency. It burns fossil fuels with pure oxygen, which enables the cost-effective separation of the combustion CO 2 by condensation. The efforts for the oxygen supply in an air separation plant are partly compensated by cycle efficiencies far higher than 60%. In this work a further development, the S-Graz Cycle, which works with a cycle fluid of high steam content, is presented. Thermodynamic investigations show efficiencies up to 70% and a net efficiency of 60%, including the oxygen supply. For a 100 MW prototype plant the layout of the main turbomachinery is performed to show the feasibility of all components. Finally, an economic analysis of a S-Graz Cycle power plant is performed showing very low CO 2 mitigation costs in the range of

Design Optimization of the Graz Cycle Prototype Plant

10/ton CO 2 captured, making this zero emission power plant a promising technology in the case of a future CO 2 tax.

Design Concept for Large Output Graz Cycle Gas Turbines

Introduction of closed-cycle gas turbines with their capability of retaining combustion generated CO 2 can offer a valuable contribution to the Kyoto goal and to future power generation. The use of well-established gas turbine technology enhanced by recent research results enables designers even today to present proposals for prototype plants. Research and development work of TTM Institute of Graz University of Technology since the 1990s has lead to the Graz cycle, a zero-emission power cycle of highest efficiency and with most positive features. In this work the design for a prototype plant based on current technology as well as cutting-edge turbomachinery is presented. The object of such a plant shall be the demonstration of operational capabilities and shall lead to the planning and design of much larger units of highest reliability and thermal efficiency.

Numerical Investigation of the Secondary Flow of a Transonic Turbine Stage Using Various Turbulence Closures

The introduction of closed cycle gas turbines with their capability of retaining combustion generated CO 2 can offer a valuable contribution to the Kyoto goal and to future power generation. Therefore research and development work at the Graz University of Technology since the 1990s has led to the Graz Cycle, a zero emission power cycle of highest efficiency. It burns fossil fuels with pure oxygen which enables the cost-effective separation of the combustion CO 2 by condensation. The efforts for the oxygen supply in an air separation plant are partly compensated by cycle efficiencies far higher than for modern combined cycle plants. Upon the basis of the previous work, the authors present the design concept for a large power plant of 400 MW net power output making use of the latest developments in gas turbine technology. The Graz Cycle configuration is changed, insofar as condensation and separation of combustion generated CO 2 takes place at the 1 bar range in order to avoid the problems of condensation of water out of a mixture of steam and incondensable gases at very low pressure. A final economic analysis shows promising CO 2 mitigation costs in the range of

Transition Modeling Using Two Different Intermittency Transport Equations

20―30/ton CO 2 avoided. The authors believe that they present here a partial solution regarding thermal power production for the most urgent problem of saving our climate.

Design Optimisation of the Graz Cycle Prototype Plant

The accurate numerical simulation of the flow through turbine stages strongly depends on the proper prediction of turbulence phenomena. Especially investigations of heat transfer, skin friction, flow separation and secondary flow effects demand a reliable simulation of the turbulence respectively laminar to turbulent boundary layer transition. This paper presents a steady state three-dimensional numerical investigation of a transonic turbine guide vane at flow conditions similar to modern highly loaded gas turbines. At the Institute for Thermal Turbomachinery and Machine Dynamics extensive experimental investigations of the three dimensional flow trough this turbine stage were done to gain a better understanding of the flow physics and to verify computational results. The applied numerical code, which was developed at the institute, solves the Reynolds-averaged Navier-Stokes equations using a time-iterative finite volume method. Turbulence is modeled with the one equation model of Spalart and Allmaras, the two equation SST k-ω model of Menter and the V2F model of Durbin, the latter model is also able to capture boundary layer transition to turbulence. The objective of this paper is to compare the numerical results with experimental data and to figure out the impact of the different turbulence models on secondary flow effects.Copyright

On the Navier–Stokes Calculation of Separation Bubbles With a New Transition Model

The accurate numerical simulation of the flow through turbomachinerydepends on the correct prediction of boundary-layer transitionphenomena. Especially heat transfer and skin friction investigationsdemand a reliable simulation of the transition process.Therefore, in this work two different one-equation transport modelsfor a transitional weighting factor are selected and modified for theimplementation into a Reynolds-averaged Navier–Stokes solver. Thisfactor is used to modify the eddy viscosity obtained from a turbulencemodel to simulate the transition process. The first model was originallydeveloped by Steelant and Dick [1] to simulate by-passtransition for high free-stream turbulence. The second model wasproposed by Huang and Suzen [2] as a blending of two modelsfor near-wall intermittency and cross-stream variation of intermittency.In contrast to one-dimensional transition models, the new approachesmodel the transition process not only in flow direction but also acrossthe boundary-layer and thus provide a more realistic prediction of thetransition process. Whereas the Steelant and Dick model (SD) allowsturbulent quantities in the free-stream prior and after transition, thesecond model by Huang and Suzen (HS) sets the free-stream turbulence tozero in the whole flowfield.The models are validated on transitional skin friction experimentson a flat plate (T3 test cases of ERCOFTAC SIG 10), on heat transfermeasurements in a linear turbine cascade done at the VKI and on laservibrometer measurements of a linear turbine cascade. Both models showgood agreement with the skin friction data, but the heat transfer canonly be predicted correctly by the Steelant and Dick model due to itsability to consider the free-stream turbulence.

Investigation of Stator-Rotor Interaction in a Transonic Turbine Stage Using Laser-Doppler-Velocimetry and Pneumatic Probes

Introduction of closed cycle gas turbines with their capability of retaining combustion generated CO2 can offer a valuable contribution to the Kyoto goal and to future power generation. The use of well established gas turbine technology enhanced by recent research results enables designers even today to present proposals for prototype plants. Research and development work of TTM Institute of Graz University of Technology since the 90’s has lead to the Graz Cycle, a zero emission power cycle of highest efficiency and with most positive features. In this work the design for a prototype plant based on current technology as well as cutting-edge turbomachinery is presented. The object of such a plant shall be the demonstration of operational capabilities and shall lead to the planning and design of much larger units of highest reliability and thermal efficiency.Copyright

DESIGN DETAILS OF A 600 MW GRAZ CYCLE THERMAL POWER PLANT FOR CO2 CAPTURE

Laminar separation bubbles are commonly observed on turbomachinery blades and therefore require effective methods for their prediction. Therefore, a newly developed transition model by Gostelow et al. (1996) is incorporated into an upwind-biased Navier-Stokes code to simulate laminar-turbulent transition in the boundary layer. A study of the influence of the two adjustable parameters of the model, the transition onset location and the spot generation rate, is conducted and it is found that it can predict laminar separation bubbles, measured on a NACA 0012 airfoil. Additional results are presented for separation bubbles in an annular compressor cascade.

A FURTHER STEP TOWARDS A GRAZ CYCLE POWER PLANT FOR CO2 CAPTURE

The current paper presents steady and unsteady flow data of a transonic test turbine stage operating under flow conditions similar to modern highly loaded gas turbines. Measurements were performed between stator and rotor as well as downstream of the rotor in planes perpendicular to the rotor axis. Time resolved axial and tangential velocities were measured by a two-component Laser Doppler Velocimeter (LDV) to investigate unsteady phenomena, while time-averaged flow properties were measured by means of a pneumatic seven-hole probe for all three spatial directions. The time-resolved investigation done by LDV allows to present velocity fields, flow angles and turbulence data at different stator-rotor positions during one blade passing period. Averaging these results enabled comparison with the pneumatic multi-hole probe measurement. LDV data and stage geometry can be obtained per email request and used for CFD code verification.Copyright