[ ENERGY / IN DETAIL ]

] Introducing the world’s largest gas engine

AUTHOR: Mikael Wideskog, General Manager, Gas Plants, Power Plant Tecnology, Wärtsilä Power Plants ENERGY / IN DETAIL DETAIL IN / ENERGY [

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Wärtsilä has introduced the largest gas engine on the market. Based on the well-proven technology of the Wärtsilä 34SG and 50DF engines, the Wärtsilä 18V50SG has an output of 18 MW and offers an alternative to gas turbines for large power plants.

Power plants based on multiple engines gas engine once again makes combustion result in efficiency improvements have many advantages. For example, engines an attractive alternative to of around 0.5 percent per year. since operators need run only as many gas turbines for large power plants. The Wärtsilä 18V50SG is based on engines as are required, they offer flexible the same design principles as the well- power output with high plant efficiency. Design and development proven technology used in the Wärtsilä Operators can also carry out maintenance The Wärtsilä 50SG is a four-stroke, spark- 34SG and Wärtsilä 50DF engines. without shutting down the entire plant. ignited gas engine that works according As the engine was based on existing But as plant sizes increase increase, there to the Otto principle and the lean- technology, its development was very is a need for units with higher output. burn process. The engine runs at 500 or quickly implemented. Development The most engines that Wärtsilä has installed 514 rpm for 50 or 60 Hz applications, started in 2008, and the first 6-cylinder to-date in a single plant, is the 28 Wärtsilä and produces 18,810 and 19,260 kW laboratory engine was built in 2009. 34SG units for a 270 MW power plant of mechanical power respectively. Assembly of the first customer engine in Turkey. This seems to be the point This represents maximum electrical began the following year and its at which operators tend to opt for gas power outputs of 18.32 MW and testing was completed at the Trieste turbines due to their larger unit size. 18.76 MW respectively, at which the facility by the end of 2010. With the introduction of its latest gas Wärtsilä 50SG has an efficiency of 48.6 The engine frame is based on the engine Wärtsilä can now offer a product percent at the generator terminals – Wärtsilä 18V50DF dual-fuel engine, directly competing with the gas turbine 2.3 percentage points higher than the with the same advanced integrated technology. By doubling the output of the smaller Wärtsilä 34SG. This is a big step, lube oil and cooling water channels. Wärtsilä 34SG, the new Wärtsilä 50SG since typically product improvements The combustion system is based on

Table 1 – The output of the Wärtsilä 50SG engine. Table 2 – Dimensions and weights of the Wärtsilä 50SG generating set.

50 Hz/500 rpm 18V50SG Lenght mm 18 800

Power, electrical kW 18 321

Heat rate kJ/kWh 7411 Width mm 5330

Electrical efficiency % 48.6

Height mm 6340 60 Hz/514 rpm 18V50SG

Power, electrical kW 18 759 Weight tonne 360

Heat rate kJ/kWh 7411

Electrical efficiency % 48.6

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] the Wärtsilä 34SG, but has a larger a new technology for Wärtsilä, and bore size to maximize the power thus required more design and research potential of the engine block. work. Furthermore, its performance Increasing the bore size from 340 mm and possible consequential benefits to 500 mm on a spark-ignited engine was were also unknown for this bore size. a key area of technology development. Both concepts were tested and found In a modern gas engine, lean-burn to perform equally well. Based on technology is a necessity in achieving proven reliability and lower cost, it was low emission levels without external decided to opt for the spark ignition

ENERGY / IN DETAIL DETAIL IN / ENERGY exhaust gas after-treatment. In lean-burn with pre-chamber technology. [ technology, the charge in the cylinder has far more air than is actually needed Pre-chamber for complete combustion of the gas. The pre-chamber is the ignition Ignition of the extremely lean fuel source for the main fuel charge, and charge is very difficult, and the right is an essential component of a lean- ignition technology is needed to provide burn spark-ignited gas engine. a high-energy ignition source. It should be as small as possible to

The choice of ignition technology deliver low NOX values, but big enough most suited for a pure gas engine with for rapid and reliable combustion. a large bore was discussed extensively Extensive calculations and simulations at the beginning of the project. had to be performed to scale-up the Spark ignition with a pre-chamber, size and shape of the combustion also known as SG technology, is used pre-chamber in order to ensure on existing pure gas engines. However, the best combustion process. the consequences on performance In addition to the size and shape when scaling the technology to a of the pre-chambers, some of the key bore of 500 mm were unknown. design parameters considered were: the An alternative option of using a micro mixing of air and fuel; gas velocities pilot liquid fuel ignition through a pre- and turbulence at the spark plug; chamber was also proposed. This was cooling of pre-chamber and spark

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plug; and the selection of material. Engine frame Advanced three-dimensional, The engine frame is based on the computerised fluid dynamics were proven design of the Wärtsilä 50DF, used during design to deliver: and the block is made from cast O Reliable and powerful ignition iron. The engine has an under slung O High combustion efficiency crankshaft, which imparts high stiffness and stability to the engine block and provides O Extended spark plug life excellent conditions for maintenance.

O Very low NOX levels. The engine block has large crankcase doors to enable easy maintenance. The engines use a ported gas admission system, whereby gas is admitted Cooling system to the pre-chamber through a The Wärtsilä 50SG is designed with a mechanical, hydraulic-driven valve. Wärtsilä open interface cooling system The gas admission valves are for optimal cooling and heat recovery. located immediately upstream, The system has four cooling circuits: the and are electronically actuated cylinder cooling circuit (jacket), the low and controlled to feed the correct temperature charge air (LTCA) and high amount of gas to each cylinder. temperature (HTCA) cooling circuits, Since the gas valve is timed and the circuit for the lube oil cooler independently of the inlet valve, the (LO) built onto the auxiliary module. cylinder can be scavenged without The LTCA cooling circuit and jacket risk of the gas escaping from the cooling circuit have water pumps inlet directly to the exhaust. integrated within the cover module at Various parameters, such as engine the free end of the engine coolers, and load, speed, and cylinder exhaust the temperature of the water exiting temperatures, are monitored and used the jacket cooling circuit is controlled as input to the Engine Control System by external thermostatic valves. (ECS). The ECS is Wärtsilä’s latest The default cooling system is a single- UNIC (Unified Controls) C3 system, circuit radiator unit whereby the cooling which controls the entire engine. circuits on the engine are connected in This solution has proved to be series. For heat recovery applications, extremely reliable and it results in an each cooler can be individually connected excellent mixture in the pre-chamber. to an external cooling system.

Ignition system Lubricating oil system The Wärtsilä 50SG ignition system has The engine has an engine-driven been specifically designed for the new lubricating oil pump and is provided with engine and is closely integrated with the a wet sump oil system. Before entering the ECS. The ignition module communicates engine, the oil passes through a full-flow with the main control module, which then automatic back flushing filter. A duplex determines the global ignition timing. cartridge filter is installed in the back The ignition module controls the flushing line, and both filters are equipped cylinder-specific ignition timing based with differential pressure switches. on the combustion quality. The cylinder- A separate pre-lubricating system is used specific control ensures optimum before the engine is started to avoid combustion in every cylinder with engine wear. respect to reliability and efficiency. The ignition coil is located in the Pistons cylinder cover and is integrated into the The pistons are of the low-friction, spark plug extension. The coil-on-plug composite type, with a forged steel top design minimizes the number of joints and nodular cast iron skirt. Their long between the spark plug and the ignition life is ensured through the use of a skirt- coil, and thus increases reliability. lubrication system, a piston crown with The spark plug has been specially shaker-cooling, hardened piston ring developed for long life, and to withstand grooves, and low-friction piston rings. the high cylinder pressure and temperature resulting from the high engine output.

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] Piston ring set corrosion-resistant precision bearing. The two compression rings and the oil control ring are located in the piston Crankshaft and bearings crown. This three-ring concept has The crank gear has to be able to operate proven its efficiency in all Wärtsilä reliably at high cylinder pressures. The engines. Most of the frictional loss from crankshaft must be robust and the a combustion engine originates from specific bearing loads maintained at the piston rings. A three-ring pack has acceptable levels. This is achieved by proven to be the optimal solution, offering careful optimization of the crank throw

ENERGY / IN DETAIL DETAIL IN / ENERGY both function and efficiency. In a three- dimensions and fillets. The specific bearing [ pack, each ring is dimensioned and loads are conservative and the cylinder profiled for the task it must perform. spacing, which is important for the overall length of the engine, is minimized. In Cylinder head addition to low bearing loads, the other The engine uses four-screw cylinder head crucial factor for safe bearing operation is technology. At high cylinder pressures oil film thickness. Ample oil film thickness this technology has proven to be superior, in the main bearings is ensured by optimal especially when liner roundness and balancing of the rotational masses, and dynamic behaviour are considered. In in the big-end bearing by un-grooved addition to easier maintenance and bearing surfaces in the critical areas. reliability, it provides the freedom to employ the most efficient air inlet and Turbo charging system exhaust outlet channel port configurations. The Wärtsilä 50SG is equipped with A distributed water flow pattern is used a single pipe exhaust turbo charging for proper cooling of the exhaust valves, system designed for minimum flow the cylinder head flame plate, and the losses on both the exhaust and air sides. pre-chamber. This minimizes thermal The interface between the engine and stress and guarantees a sufficiently low turbocharger is streamlined, The engine exhaust valve temperature. Both inlet and uses high-efficiency turbochargers, exhaust valves are fitted with rotators for with the engine lubricating oil also even thermal and mechanical loading. being used for the turbocharger.

Cylinder liner and anti-polishing ring Automation The cylinder liner features an anti- All engine functions are controlled by polishing ring, which reduces lube oil the UNIC C3 engine control system, consumption and wear. The bore-cooled a microprocessor-based distributed collar design of the liner ensures minimum control system mounted on the engine. deformation and efficient cooling. Each The various electronic modules are cylinder liner has two temperature dedicated and optimized for specific sensors for continuous monitoring of functions, and they communicate piston and cylinder liner behaviour. with each other via a CAN databus.

Connecting rod and big-end bearings Cylinder pressure control The connecting rod is designed for optimal Each cylinder is equipped with a bearing performance. It features a three- pressure sensor. The cylinders can be piece design, in which combustion forces individually set to run at their optimum are distributed over a maximum bearing point to achieve the highest engine area, and relative movements between power and efficiency. This also applies if mating surfaces are minimized. The design operating conditions change, as in the also allows the compression ratio to be case of varying methane numbers and varied to suit gases with different knocking ambient temperatures. Additionally, resistance. The three-piece design reduces this means that the engine can be run the height required for piston overhauling. with increased safety and reliability. Piston overhaul is possible without Cylinder pressure measurements provide touching the big-end bearing, and the significantly improved engine control. big-end bearing itself can be inspected From the signal emitted by the pressure without removing the piston. The big-end sensors, UNIC can instantaneously bearing housing is hydraulically tightened, determine the rate of heat release, the resulting in a distortion-free bore for the magnitude and location of peak pressures

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and the knock severity. The sensors can gas quality. The main control module Monitoring modules also be used to determine the indicated reads the information sent by all the Monitoring modules are located close mean effective pressure, which is essentially other modules. Using this information, it to groups of sensors, which reduces the a measure of the power developed in adjusts the engine’s speed and load control amount of cabling on the engine. The each cylinder. The sensor is designed to by determining reference values for the monitored signals are transmitted to the withstand high cylinder temperatures main gas admission, air-fuel ratio, and main control module, and are used for and pressures – up to 300°C and 300 ignition timing. The main control module the engine control and safety systems. bar. The maintenance interval of the automatically controls the start and stop The monitored values are also transferred sensor equals that for the cylinder head sequences of the engine and the safety to the Wärtsilä Operators Interface System overhaul, i.e. around 16,000 hours. The system. The module also communicates (WOIS) on the plant automation system. location of the pressure sensor is also with the plant control system. important. The measuring membrane Customer benefits of each sensor is flush-mounted in Cylinder control module In addition to higher efficiency and the combustion chamber, to ensure Each cylinder control module monitors increased power output, another key measurement of correct and reliable data. and controls three cylinders. The cylinder benefit of the Wärtsilä 50SG, as with all control module controls the cylinder- Wärtsilä engines, is its ability to run up Main control module specific air-fuel ratio by individually and down in load without affecting the The core of the engine control system adjusting the gas admission for each maintenance schedule. This is useful for is the main control module. This is cylinder. The cylinder control module peak applications, or in markets where responsible for ensuring the engine’s measures the knock intensity, i.e. there is a significant amount of wind reliable operation and for keeping the uncontrolled combustion in the cylinder, power on the grid – it can reach full engine at optimum performance in all which is used to control the cylinder- power in 10 minutes in the event of a operating conditions, including varying specific ignition timing and gas admission. sudden drop in wind capacity. The engines ambient temperatures and fluctuating can also be stopped in one minute and reloaded in just five minutes, something that is not possible with gas turbines. Compared to gas turbines, the performance of the engine is also less sensitive to ambient conditions. There is little drop-off in efficiency or power output at higher ambient temperatures. Already customers are keen to take advantage of this new engine. The first has been installed at the Aksa Samsun power plant in Turkey, and will serve as a pilot engine, allowing Wärtsilä to continue its field testing. At the beginning of March, an order was also placed by Odas Elektrik Uretim, an independent power producer, for the installation of seven engines at its new plant at Urfa in southeastern Turkey. Upon completion in autumn 2011, the plant will supply 135 MW of electricity to the national grid. The new Wärtsilä 18V50SG spark- ignited gas engine has been developed in response to the increasing market need for larger gas engines to run power plants with outputs of up to the 500 MW range. It meets current and future requirements for overall cost of ownership, with very high simple and combined cycle efficiency. It is also designed for easy maintenance and many hours of maintenance-free operation.

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] REFERENCE: SAMSUN, TURKEY ENERGY / IN DETAIL DETAIL IN / ENERGY [

The Aksa Samsun combined cycle plant will be equipped with the first Wärtsilä 18V50SG generating set.

THE NEW WÄRTSILÄ 50SG ENGINE MAKES ITS DEBUT IN TURKEY

Wärtsilä was awarded an engineering and equipment contract relating to the extension of the Aksa Samsun power plant in Samsun, Turkey.

The Aksa Samsun power plant has been extended to incorporate The Aksa Samsun combined cycle plant, owned by AKSA the Wärtsilä 18V50SG engine, the latest addition to Wärtsilä’s ENERJI, currently operates using seven Wärtsilä 18V46 gas engine portfolio. This is the very first installation of the engines running on heavy fuel oil (HFO), six of which will Wärtsilä 18V50SG unit, which features an exceptionally high be converted to Wärtsilä 18V46GD engines for gas-fired power plant efficiency rating of over 50 per cent in combined operation. When the Wärtsilä 18V50SG engine has been cycle mode. In converting the Aksa Samsun facility from HFO commissioned in 2011, the power plant will have a total to gas-fired operation, its environmental sustainability is electrical output of approximately 130 MW in combined obviously enhanced. At the same time, the efficiency of the cycle mode, which will be fed to the national grid. new Wärtsilä 50SG engine sets a benchmark for the industry. Wärtsilä already has a very strong presence in Turkey’s The scope of supply also includes the controls, energy market, and expects to have delivered close to 3 GW automation and auxiliary equipment related to the fuel of power generating capacity by the end of 2011. Some 85 per gas, charge air, cooling and exhaust gas systems. cent of these power plants will be running on natural gas.

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