Steam Bottoming Cycles for the W20V34SG Gas Engine
2006 (English)Report (Other academic)
Modern internal combustion engines fired with natural gas offer comparatively low installation costs, long life, good efficiency characteristics, and show reliable performance in power applications. Additional positive features such as short delivery times, quick start-up, and retained high efficiency at part-loads have made gas engines the preferred choice for many small- to medium-scale power plants. Wärtsilä’s gas engine portfolio offers several well-proven engine models optimised for stationary power applications in the size range from 4 to 8.7 MWe, and two dual-fuel gas-diesel engine modifications of 6 MWe and 16.6 MWe. There is a rising interest in combined cycle mode engines with possibly higher electrical efficiencies, at locations where heat energy is not needed or where electricity prices inspire investments in maximum power production. Various types of bottoming cycles can be applied to utilise the waste energy streams from the main engine and deliver additional power output. The basic hurdle though is the low electrical efficiency of the bottoming cycle due to low temperature levels of the engine waste energy streams, and the consequent low economic performance of the bottoming cycle hardware, which in itself can often require investment costs close to those for the main engine. Therefore, more efficient bottoming cycle alternatives should be examined, as well as a better optimisation and thermodynamic/economic evaluation of those should be performed in order to find an applicable solution. The work presented herein concentrates on heat-balance simulations and thermodynamic evaluation of conventional cold-condensing steam bottoming cycles optimised for high electrical efficiency utilizing the waste energy streams from the W20V34SG gas engine of 8730 kWe net power output. Highest possible electrical efficiency for the combined cycle is sought, i.e. the bottoming cycle is configured and designed to match the given topping engine and to utilize the exergy content of the engine’s exhaust streams in the best possible way, while using only conventional steam technology with standard components, and applying a slightly optimistic approach with regards to isentropic efficiencies, generator efficiencies, steam condenser conditions, and heat-exchanger effectiveness. Steam bottoming cycles of varying complexity have been simulated and evaluated with the help of computer simulations based on the heat-balance software product ProSim. The simulation results show that the net electrical power output of the steam bottoming cycle alone can reach from around 847 kWe (i.e. 9.7% of the main engine power output) for the simplest single-pressure cold-condensing configuration, up to 1270 kWe for a very complex yet practical configuration, which is 14.5% of the main engine output. The electrical efficiency of the combined cycle can reach up to 50.8 % LHV and even more, which is a 6 %-point increase above that of the main engine in single-cycle operation.
Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2006. , 33 p.
Wärtsilä Power Plants, Natural Gas, Internal Combustion Engine, Steam Bottoming Cycle, Combined Cycle, Simulation, Heat-Balance, Electrical Efficiency
IdentifiersURN: urn:nbn:se:kth:diva-89856OAI: oai:DiVA.org:kth-89856DiVA: diva2:503761
QC 201202172012-02-172012-02-162013-11-12Bibliographically approved