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Turbines for propulsion and power

Turbines for propulsion and power 6
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Published Date:19-07-2017
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New Developments in Combustion Technology Part II: Step change in efficiency Geo. A. Richards, Ph.D. National Energy Technology Laboratory - U. S. Department of Energy 2014 Princeton-CEFRC Summer School On Combustion Course Length: 6 hrs June 23-24, 2014 Presentation Identifier (Title or Location), Month 00, 2008 This presentation Updated, expanded from 2012 CEFRC lecture: – Inherent carbon capture: chemical looping combustion (Day 1) – Step-change in generator efficiency: pressure gain combustion (Day 2) – Frontier approach (?): making oxy-fuel an efficiency advantage (Day 2) Sampling & Diagnostics RDC Flow P-gain rig NETL ‹› The role of capture AND generator efficiency • A simple Define: heat/energy a = (kg CO produced) / (kg fuel burned ) 2 balance defines w = (separation work, Joules ) / (kg CO ) CO2 2 CO 2 the overall efficiency h with ov a carbon separation unit. h g Generator Efficiency • Reducing the Q = m DH f W 1 W Fuel Heat o Net penalty from Gross Input Generator Output Generator Carbon carbon capture Work Separation comes from Unit BOTH: – Decreasing w CO2 – Increasing h g Approx Ranges: (30 – 60%) (6-10%) ‹› Turbines for propulsion and power Almost any fuel – even coal, via integrated gasification combined cycle (IGCC). Shale gas revolution = more turbines “…The research firm (Forecast international) anticipates that 12,054 turbines with a value of 218 billion will be sold world-wide in the coming decade…” Siemens Moves Fueled by U.S. Gas, Wall Street Journal, May 8, 2014, pp. B2 IGCC plant under construction, Kemper County, Mississippi, USA ‹› History and Turbine Efficiency Gas turbine efficiency trend • Combined Cycle Gas Turbine 70 Efficiency is today + 61% (LHV). 60 50 Linear… • Efficiency gains have occurred 40 y = 0.5x - 942 with steady progress in materials, 30 heat transfer, and system design. 20 – About +0.5 % per year (right). 10 0 1960 1980 2000 2020 • Impressive performance is still Year well-below potential: Test rig for h = 1-293/(1873) = 84% Carnot 1600C advanced aerothermal State of the art turbine inlet temperature cooling development • What can be done to “jump above” the line? Sources: (1) Herzog, H., Unger, D. (1998) Comparative Study on Energy R&D Perfrmance: Gas Turbine Case Study, Final Report for Central Research Institute of Electric Power Industry (CRIEPI), Figure B, pp. iii. , (2) Gas Turbine World 2012 Performance Specs, 28th ed Vol 42, No1, pp 31. ‹› Combined Cycle LHV Efficiency (%) A step-change in efficiency • Turbine pressure-ratio and firing temperature influence the combined cycle efficiency. • A combined cycle exploits the heat rejected by the “hotter” turbine cycle to the “colder” steam cycle. • If you want a “step-change” in efficiency, it is logical to identify the biggest losses and work on those. – Where is the biggest loss of thermodynamic availability (or exergy)? – An interesting example for a cogen system (e.g. no steam “bottom”, but steam heat) is presented by Bejan et al. in the table. Exergy Destruction (% of fuel Component input) Combustion 30.0 Chamber Steam generator 7.3 Turbomachinery 3.5 Gas turbine 3.1 Bejan, A., Tsatsaronis, recuperator Moran, M. (1996) Thermal Design and Compressor 2.5 Optimization, John Wiley publishing, Table Overall 46.4 3.2, page 140. ‹› Pressure Gain Combustion A different cycle Constant-volume combustion products are at a significantly greater thermodynamic availability than constant-pressure. 30 bar, 30 bar, 30 bar, 100 bar, 1600 K 600 K 600 K 2000 K Conventional steady combustion Pressure -gain combustion (constant pressure) (constant volume) DU = Q DH = Q C DT = Q C DT = Q v cons V p cons P ‹› Pressure Gain Combustion A different cycle Constant-volume combustion products are at a significantly greater thermodynamic availability than constant-pressure…..but what happens if the pressure is bled off to the ambient - Unrestrained unrestrained? expansion Returns to constant pressure availability –must capture the pressure gain to have a benefit. 30 bar, 30 bar, 30 bar, 100 bar, 1600 K 600 K 600 K 2000 K 30 bar, 1600 K Conventional steady combustion Pressure -gain combustion (constant pressure) (constant volume) Noisy, but no DU = Q DH = Q benefit C DT = Q C DT = Q v cons V p cons P ‹› Pressure Gain Combustion Cycle DP 0 • Convention gas turbines combustion results in a C T pressure loss across the combustor (Brayton cycle) DP 0 C T • Pressure gain with constant volume combustion (Humphrey cycle) – Deflagration or detonation pressure wave increases pressure and peak temperatures at turbine inlet - reduced entropy production during combustion. ‹› History • The idea of capturing the available energy from confined combustion (versus constant pressure) is well recognized. – Piston engines do this already. – Early gas turbines used the concept (Holzwarth “explosion” turbine). – Compound piston-turbines have been built and flown. – Constant-volume combustion eclipsed by easier improvements THYSSEN-HOLZWARTH OIL AND GAS TURBINES, Journal of the American Society for Naval Engineers Volume 34, Issue 3, pages 453–457, August 1922. . From the article: “……Holzwarth- turbine working with a compression of 2.2 atmospheres and an explosion pressure of 17.3 atmospheres absolute….” Photo used with permission FIG. 8. – THE 500B.H.P. THYSSEN-HOLZWARTH OIL from Naval Engineers Journal TURBINE, WHICH MAY BE THE POWER OF THE FUTURE FOR MERCHANT SHIPS. Napier Nomad Engine (1950) Nomad photo credit: Kimble D. McCutcheon via the Aircraft Engine Historical Society. ‹› Why is pressure-gain appealing now? Pressure-Gain Combustion for Power Generation Michael Idelchik, Vice President of Advanced Technologies at GE Research… Research…Sept 2009 interview on Pulse Detonation for Technology Review published by MIT. “An existing turbine burns at constant pressure. With detonation, pressure is rising, and the total energy available for the turbine increases. We see the potential of 30 percent fuel-efficiency improvement. Of course realization, including all the hardware around this process, would reduce this. I think it (efficiency gains) will be anywhere from 5 percent to 10 percent. That's percentage pointssay from 59 to 60 percent efficient to 65 percent efficient. We have other technology that will get us close to that but no other technology that can get so much at once. It's very revolutionary technology. The first application will definitely be land-basedit will be power generation at a natural-gas power plant. “ “If we can turn 5% pressure loss in a turbine into 5% pressure gain, it has the same impact as doubling the compression ratio” – Dr. Sam Mason, Rolls-Royce (2008) Quotation courtesy Fred Schauer AFRL 2012 lecture Gas Turbine World Pequot Publishing Nov – Dec 2013 issue December 2013 Pulse detonation for 65% plant efficiency Page 20 ASME Mechanical Engineering Magazine, Image used with permission Image used with permission of Gas Turbine World ‹› Current Technology Approaches Resonant Pulsed Combustion † ( deflagration) † Envisioned as a canular arrangement Detonation or ‘Fast’ Deflagration G.E. Global Research Center NASA Glenn, 2005 2005 University of Cambridge, 2008 IUPUI/Purdue/LibertyWorks, 2009 Rotating Detonation DOE National Energy Technology Laboratory, 1993 Engine (NRL) Slide provide by Dan Paxson, NASA Glenn ‹› Pulse deflagration combustion Current R&D at NASA, Cambridge-Whittle Past Work at NETL ‹› Aerovalved Pressure Gain Combustor ‹› NETL Atmospheric Pressure Rig (1991) • Combustor constructed with standard pipe fittings. • Allows simple changes in inlet and tailpipe geometry. ‹› One-Dimensional Modeling Characteristic Timescales • Divide combustor into three distinct zones. • Solve conservation equations of mass, momentum and energy. • Provides estimation of frequency and amplitude. ‹› One-Dimensional Modeling Why not CFD? Characteristic Timescales 1) Hint: this was 1990. 2) No theory for initial design & scaling. Nice Computer • Divide combustor into three distinct zones. • Solve conservation equations of mass, momentum and energy. • Provides estimation of frequency and amplitude. ‹› Atmospheric Pressure Rig Data NG/Air f=0.82 • Baseline geometry (L =10 cm, L =60 cm). in ex • Resonant frequency 160 Hz ‹› Optimized Geometry • Maximum of 0.45% pressure gain achieved. ‹› NETL High Pressure Rig (1994) • NG/Air up to 11 atm. • Simple non-rectified design. ‹›