颜巴赫燃气内燃机与2级涡轮增压器

GE’s new Jenbacher Gas Engines with 2-stage TurbochargingGE EnergyKlaus Payrhuberklaus.payrhuber@GE Power & WaterJenbacher Gas EnginesAchenseestrasse 1-36200 Jenbach, AustriaChristian Trappchristian.trapp@GE Power & WaterJenbacher Gas EnginesAchenseestrasse 1-36200 Jenbach, AustriaAbstractFor years gas engines have been gaining importance within the global energy mix. One reason for that is the comparatively good, long term availability of natural gas combined with achieving a high level of electrical and thermal efficiency. A total efficiency of 90% and above can be achieved using the new advanced 2-stage turbocharging technology GE’s Jenbacher gas engine business introduced in 2010. In addition to that GE’s Jenbacher gas engines meet the most stringent emission standards, for example the German Technische Anleitung Luft (TA Luft). This makes large gas engines a comparable cleaner technology for supplying electricity and heat around the globe as part of a decentralized structure.The J624 (type 6) design concept is based on a pre-chamber ignition system, favorable combustion geometry, reasonable piston speed with about 11 m/s, separation of the cool mixture intake section from the hot exhaust gas flow (cross flow cylinder head) and a four-valve cylinder head design. This concept allowed continuous performance improvements on the type 6 engine over time. The electrical efficiency could be increased from 38% in 1994 to 46.5% in 2010.The J920 design is also based on pre-chamber ignition system, favorable combustion geometry, reasonable piston speed with about 11 m/s, but compared to the type 6 engine the J920 is designed with a port injection system. The J920 is designed to achieve an electrical efficiency of 48.7%.With the new 2-stage turbocharging technology, both engines can achieve optimized combustion and best in class electrical efficiency. Now, both the J624 and the J920, are more suitable for operations in hot and humid environments, as well as high-altitude regions without output and efficiency derating. And for combined heat and power applications, a total efficiency of 90% and more can be achieved. That is about 3-4% pts more compared to standard single stage turbocharging.Key WordsGE, Jenbacher, Gas Engines, 2-stage turbocharging, J624, J920IntroductionGE’s Jenbacher gas engine business recently expanded their gas engine portfolio by adding a larger gas engine with 9.5 MW – the J920 – with a top of it’s class efficiency of 48.7%. Earlier in 2010, GE’s Jenbacher gas engine business introduced the new J624 with improved output of 4.4 MW and advanced efficiency of 46.5%. Both engines achieve high electrical efficiency due to the new 2-stage turbocharging system.Decentralized power generation plays an important role in providing reliable and sustainable power solutions in remote areas as well as in developed regions. Ideally decentralized power provides additional benefits when combining heat and power solutions, trigeneration with air conditioning or greenhouse applications. In developed regions, decentralized power has an additional role for grid stabilization and providing flexible power to support the growing renewable portfolio on the grid.For more than 50 years GE’s Jenbacher gas engine division has been developing solutions for the never-ending list of new technological challenges to stationary gas engines and is thus driving technology forward. In 2007, GE’s Jenbacher business introduced the world’s first 24-cylinder gas engine for commercial operation. The 24-cylinder engine builds on almost 20 years of experience with the type 6 engine family, which now has an installed fleet of more than 2,000 units.Figure 1: J624, 2-stage turbocharged Figure 2: J920, 2-stage turbochargedIn 2010 the new J624 with 10% more power output and about 1% point higher electrical efficiency was introduced and is the largest gas engine in our product program today. Due to 2-stage turbocharging this engine achieves a total efficiency of 90% and more. This is about 3 to 4 % pts more than a gas engine with state of the art single stage turbocharging. The first pilot engine of the new J624 is in commercial operation in the Netherlands since September 2010. Three more engines have been shipped to customer sites in Europe and Asia in 2010 – figure 1.In 2010 GE’s Jenbacher gas engine business also introduced the new J920 larger gas engine with a design based on GE’s long experience with high-speed gas engines having high power density. The J920 is designed with the same 2-stage turbocharging system as the J624 and can also achieve a total efficiency of 90% and more. The innovative three-module concept, offers a high quality, standardized generator-set comprised of the engine itself, a generator and an auxiliary module – figure 2.Technology TrendsThe GE Jenbacher type6 engine provides a perfect trend history of how highly efficient gas engines developed. By increasing the mean effective pressure (PME) in combination with a continuous improvement of combustion and optimization of the charging as well as the charge exchange process, the electrical efficiency of the generator set could be increased from an original 38% in 1994 (at 12 bar PME) to 45.6% in 2009 (at 22 bar PME) while always meeting TA Luft. The new J624 with 2-stage turbocharging, has an electrical efficiency of 46.5% and produces 4.4 MW (at 24 bar PME). It follows the same general path of development. However, new technology blocks are combined to push the limits of previous production level engines. The road to far advanced Miller valve control times and the optimized lean-burn combustion process, enabling high efficiency levels and low NO x emissions, was paved by 2-stage turbo charging - figure 3. Combined with the optimized MORIS high energy ignition system along with refined control strategies and algorithms, these technology blocks facilitate a sufficiently wide operating band between the knock and misfire limits. In particular they make operation possible at high altitudes and under tropical conditions without compromising efficiency.Figure 3: Principle design of the 2-stage turbocharging and intercoolingENGINE AND CHARGINGThe new J624 is based on a modular build consisting of base engine, turbocharger auxiliary module, and the generator. Like all GE’s previous Jenbacher gensets, the new engine runs at 1,500 rpm to generate a grid frequency of 50 Hz. The J624 version of the type 6, which had gone into customer operation in 2008, provided the basis for development work. Up to that point it was GE’s Jenbacher engine with highest electrical output of 4 MW. Type 6 engines work with exterior mixture preparation, which is done in a gas mixer located before the compressor, and with Miller valve timing plus a lean-burn combustion process with a gas-enriched pre-chamber.Far advanced Miller valve timing reduces the knock tendency, however, it also increases the required charge pressure beyond the level needed for the increased λ. Using single stage charging the required compression ratio of considerably >6 would have been just about achievable with special turbocharger technology. But even so the turbocharger efficiency would have dropped dramatically to a value of under <60 % which would have offered no buffer for future improvements.Therefore the decision was made to develop a 2-stage turbocharging which offers a potential charging pressure of up to 10 bar at a charging efficiency of >73 %. The newly developed charger module consists of a low-pressure compressor with subsequent mixture inter cooling, a high-pressure compressor with mixture cooling and the corresponding high- and low-pressure turbocharger turbines on the exhaust side - figure 4. Power control of the engine is done via a compressor by-pass. All three possible by-pass options – by-passing both compressors, high-pressure compressor by-pass, and low-pressure compressor by-pass – were analyzed during the early development phase together with the optimum design of turbine and compressor wheels.Figure 4: The turbochargers in the auxiliaries module (arrows indicate the flow)2-stage turbocharging is also used for the J920, GE’s larger Jenbacher gas engine with 9.5 MW output. Therefore this engine also benefits from all the advantages of this technology and this has a significant contribution to achieve the advanced efficiency of 48.7 %.The optimum realization of the two stage turbocharging not only provides the required pressure level in the intake pipe to facilitate far advanced Miller valve timing but it also provides the necessary pressure differential of 1,000 mbar between inlet and outlet side. To avoid scavenging losses caused by mixture charging (HC emissions and loss of efficiency) the valve timing was further optimized, particularly during the overlap phase, to find a trade-off between flushing (residual gas level) and HC-slip.Closing the inlet valves very early leads to a charge expansion and re-compression in the cylinder; this considerably brings down the temperature in the end gas zones and thus the knock tendency. The valve timing of the new J624 is defined to avoid knock during the entire engine lifetime despite a maximum permissible mixture temperature after the intercooler of above 70°C, a 24 bar PME, and a varying methane count.This high temperature level in the intake system avoids mixture condensation even under tropical conditions and thus permits harvesting the full efficiency and power at ambient temperatures of over 40°C, given a suitable dimension of the turbochargers. In addition the heat from the mixture cooler can be dissipated by much smaller horizontal air coolers under the above mentioned tropical conditions and without the need for a cooling tower. In a combined heat and power installation all this heat can be fed into the heat circuit and can help to increase the overall plant efficiency to more than 90%.The new J624 combustion process is based on burning a lean mix in combination with a gas-enriched pre-chamber. The very lean mixture (λ > 2) in the main combustion chamber is ignited by the flame jets emerging from the pre-chamber, which ensures a complete combustion. Within the pre-chamber the lean mixture, which is enriched by additional gas, is ignited by a special spark plug that ensures ignition even at 60 bar firing pressure. This combustion process, in particular the tuning of flame orifice channel shape, charge movement, piston and pre-chamber design had to be newly developed to warrant an optimum combustion timing and a complete combustion even under very lean conditions - figure 5. The J624 development was completed by more sophisticated and improved control strategies and algorithms which mostly serve tocontrol power, knock and emissions, but which are still based on the LEANOX® concept’s patented approach.Figure 5: Flame progress of the combustion and level of burn-outDEVELOPMENT METHODOLOGYIt takes a lot to keep up or even exceed the high level of quality during a new development while pushing previous limits at the same time: On top of more than 50 years of experience a powerful and reliable development methodology is needed - figure 6. It integrates the various tools and methodologies, such as databases, simulation processes and tests, in a simultaneous engineering process.The beginning of any development is formed by analyzing requirements in detail, which in turn is based on a profound understanding of customer requirements and legal standards around the world. These are driven down from the product level to functions, systems, and sub-systems, right to the individual component. During this the engine base design is defined, a process that draws on databases, experience with similar types, competition analyses, working-process calculation as well as 1D flow simulation.Figure 6: Schematic view of the development methodologyAs early as in the first concept stage the most important target parameters of the engine, such as power, efficiency, emissions, but also cost, have to be modeled with sufficient precision to be able and evaluate the influence of operating conditions, gas quality, plus engine and systems concepts. During the next step the concepts are described in more details via more powerful simulation, such as 3D in-cylinder flow and combustion, FEA analyses, single cylinder engine testing and component testing. Along with the progress more and more test results either confirm or replace the simulation data. Within the detail design phase the final engine construction is defined and the individual component design is simulated with a focus on service-life considerations.Full engine testing, which serves to optimize systems and components, forms the transition from the development phase to validation. It is now, that the engines have to demonstrate their readiness for production on the test beds. Finally, pilot customers together with the development teams carry out the ultimately decisive field testing. It is only after this phase that a new product such as the J624 with 2-stage turbocharging gets approval for full production.ApplicationsThe trend to de-centralized power generation with smaller units and multiple units installations is in favour for gas engines. Because gas engines offer high simple cycle efficiency, most of the installations are in simple cycle mode and that reduces investment costs. Due to the availability of low grade heat, gas engines are best suitable for CHP applications and offer very attractive solutions.Combined Heat and Power:As explained in the previous paragraph, 2-stage turbocharging enables 90% total efficiency – about 3 to 4 %pts higher than a gas engine with single stage turbocharging. Figure 7 shows how all the heat from the engine and engine exhaust can be utilized in a combined heat and power plant. A water return temperature of up to 70°C is allowed and cold enough for cooling all the heat exchangers on the engine.Gas engine power plants for CHP are running with constant high electrical efficiency, independent if heat is extracted or not. Only one additional gas/water heat exchanger is needed at the gas engine exhaust, all other heat exchangers are available on the engine frame. Together with the use of simple water circuits and straight forward power plant designs make gas engines very attractive for combined heat and power solutions.Figure 7: CHP Concept with 2-stage turbocharging (J624 / J920)If we compare the previous version of the J624 with single stage turbocharging and the new J624 with 2-stage turbocharging, the difference in the example below in total efficiency is 3.4% - Table 1. The electrical efficiency is set at 45.5% without a difference between the 2 versions of engines. If we assume 5,000 operating hours per heating season, there is a potential for substantial revenue increase. These additional revenues can be achieved without additional specific fuel consumption or significant additional specific investment costs.Table 1: CHP comparison between the previous and new J624•Power Output……….4 MWe •Total Efficiency……..86.6%•El. Efficiency…………..45.5%•Power Output.……..4.4 MWe•Total Efficiency…….90.0%•El. Efficiency………….45.5%3.4%pt higher totalefficiency for CHPGreenhouse Concepts:The greenhouse concept based on Jenbacher gas engines is a very attractive concept providing power, heat and CO2 as fertilizer for greenhouse crop production. Using the CO2 from the exhaust of the gas engine the CO2 concentration inside the greenhouse can be increased from around 350 ppm to approx. 1,000 ppm. With this higher CO2 concentration the productivity of the crops can be increased by 20-30%. This kind of CO2 fertilization is used to grow vegetables like peppers, tomatoes or cucumber. Today most of our greenhouse applications can be found in the Netherlands where GE’s Jenbacher team has installed more than 1.5 GW, representing about 5% of the installed capacity on the Dutch grid.The greenhouse application goes together with Ultra-low emissions on NO x, CO, C2H4. Before the exhaust gas is used in the greenhouse, a special exhaust cleaning system is reducing NO x emissions to less than 25 ppm (based on 5% O2) and reducing CO emissions by more than 99%.With a simultaneous supply of heat, electricity and CO2 a very high fuel efficiency of up to 95% is achieved. Due to the use of heat storage tanks the application allows more independent power and heat production, which makes the greenhouse concept even more attractive when operating in a liberalized energy market.Figure 8: Greenhouse ConceptMultiple gas engine power plants:Either for combined heat and power or power generation only, multiple gas engines offer several customer advantages. Due to multiple installed generating units, higher plant availability is achieved and plant output is reduced only by the incremental output - depending on the number of engines installed – in case one engine is down for maintenance. Starting from a pre-heated engine, both the J624 and the J920 offer a 5 minutes start-up time from initial to start to full load. Multiple engines can be started in parallel. The short start-up time makes gas engine power plants a preferable solution for frequent start stop operations and offers great load following capability. Figure 9 shows a J920 multiple gas engine power plant from inside.One other big advantage of multiple gas engine power plants is the high plant part load efficiency. Starting from a high simple cycle gas engine efficiency, the efficiency stays high in part load operation due to incremental engine shut-down. Only the number of engines are online and running that are required to meet the target plant output, and those engines are running at full load, hence at maximum efficiency - figure 10.Constant high plant efficiencyFigure 9: J920 Multiple gas engines plant Figure 10: Multiple gas engines efficiencySummary2-stage turbocharging is the enabling technology for higher efficiency and higher heat output of gas engine power plants. The new J624 and the J920 underline this with advanced electrical efficiencies while meeting TA Luft emission requirements. 2-stage turbocharging implemented in the new engines makes it the starting point of a new generation of GE gas engines. Testing the engine at a factory test stand and the staged field introduction of the above-mentioned improvements allows a reliable field validation of single features and minimizing customer risk.An intelligent combination of innovative technology blocks with two-stage turbocharging at their very core makes it possible to push previous limits even further: Higher brake mean effective pressures, higher levels of efficiency and wider operating areas. However, only by simultaneously optimizing, charge exchange, valve timing, combustion process and control strategy, these potentials can be utilized.Multiple engines offer a big advantage because of redundancy and if the plant needs to go to part load operation. Combined with a 5 minute start-up time, gas engines offer very attractive solutions for peak shaving and flexible power generation.References[1] Christian Trapp, Stefan Laiminger, Dieter Chvatal GE Jenbacher, Prof. A. Wimmer, E. Schneßl, G. Pirker Technische Universität Graz, Die neue Gasmotorengeneration von GEJenbacher - mit zweistufiger Aufladung zu höchsten Wirkungsgraden, 32. Internationales Wiener Motorensymposium 2011[2] Payrhuber K., Schneider M., Advancements on GE’s Jenbacher Type 6 Engines, PowerGen Europe 2010[3] Payrhuber K., Trapp Ch., Zweistufig Aufgeladener Gasmotor, Energie 2.0-Kompendium 2011[4] Payrhuber K., Dick Kramp, The new Jenbacher J624 gas engine with 2-stage turbocharging, Russia Power 2011[5] Trapp Ch., Klausner J., Lang J., J624 – der weltweit erste Gasmotor mit zweistufiger Aufladung, MTZ 2011[6] Trapp Ch., Klausner J., Schaumberger H., Lang J., Haidn M., GE Jenbacher Gas Engines, CIMAC 2010。