A MORE POWERFUL more efficient master

A more powerful, more efficient

Following its succesful introduction several years ago, Wärtsilä’s 34DF dual-fuel engine has now been upgraded. The engine will offer customers more power with no increase in dimensions, and will be even more efficient.

Text: JUNIOR ISLES Photo: WÄRTSILÄ

In 2008, the Wärtsilä 34DF was introduced as the successor for the company’s first dual-fuel engine, the Wärtsilä 32DF. The Wärtsilä 34DF is based on the Wärtsilä 32 diesel engine platform. It offers the operators the same fuel flexibility that was pioneered in the Wärtsilä 50DF but in a smaller package.

This popular engine has seen strong sales in markets where complete fuel flexibility is paramount. It has now been upgraded to make it an even more attractive option for ship and power plant owners.

The improved performance is the result of incorporating the industry’s latest technical advances. These allow the engine to produce more power with lower fuel consumption.

Commenting on the upgrade, Rasmus Teir, General Manager of Wärtsilä’s 32/34 Engine Platform, said: “Higher power density and better fuel efficiency are always the two key drivers behind engine upgrades. Typically there has to be some compromise but fortunately this time we can provide both.”

The upgraded Wärtsilä 34DF engine, produces 11% more power than the original version. In diesel mode it now consumes 7 g/kWh less fuel, while in gas mode it features increased efficiency of 1.6 percentage points. The performance improvements have been achieved without altering the physical dimensions of the engine.

This all translates into a more competitive cost of power. As an example, take a 100 MWe plant running on gas 8000 h/year. Using Henry Hub average gas prices for 2013, the new Wärtsilä 34DF engine will produce fuel savings in excess of 800,000 USD/year, compared with the previous version. Investment cost is also reduced because one generating set less is needed for a 100 MWe size plant.

“Whether customers are operating in 50 Hz or 60 Hz markets, they can expect the same improvements,” says Teir.

MULTI-FUEL OPERATION

The engine is available in a number of cylinder configurations. The 6L, 9L, 12V and 16V configurations can be used in marine applications and are particularly suited to supply vessels.  For the land-based power industry the Wärtsilä 34DF is available in 6L, 9L, 12V, 16V and 20V configurations.

The Wärtsilä 34DF is capable of multi-fuel operation, allowing operators to switch fuels during operation without stopping the engine. With the ability to switch between gaseous and liquid fuels, the engine is ideal for when there is interruptible gas supply or in situations where gas is unavailable for part of the year.

The engine’s fuel system has been divided into three: one for gas, one for liquid fuel and one for the pilot fuel system.

The Wärtsilä 34DF can be started in either gas or diesel modes. In gas mode the gas admission is activated when pilot fuel system functionality has been confirmed by a separate automated safety check during engine starting. When running the engine in gas mode the pilot fuel, which is always present, amounts to less than 1% of full-load fuel consumption. When the engine is running in liquid fuel mode, the pilot is also in use to ensure cooling and prevent clogging of the pilot injector.

A WORTHY SUCCESSOR TO THE POPULAR WÄRTSILÄ 32DF, THE NEW DUAL-FUEL ENGINE CONTAINS THE LATEST TECHNICAL ADVANCES.

KEY REFINEMENTS

The 50 Hz version of the previous Wärtsilä 34DF design has a power output of 450 kW per cylinder. With these cylinder configurations the new upgrade of the Wärtsilä 34DF can deliver power outputs ranging from 3000 kW to 10,000 kW.

In terms of power output per cylinder the new Wärtsilä 34DF delivers 500 kW/cylinder.

The higher power density is achieved through several refinements. The major changes are in the turbocharger and charge air cooler; the pistons; crankshaft; and the camshaft.

Teir points out that turbocharger boost pressure (pressure ratio) and the maximum design firing pressure of the engine are the two limiting factors on engine development.

The Wärtsilä 34DF employs the latest generation turbochargers capable of boost pressures of more than 5.5. This higher boost pressure provides a larger window over which to optimise the engine, thus giving increased output with added efficiency. The upgraded engine is also now based on the Wärtsilä 32 diesel engine platform, which has a design firing pressure that is 20 bar higher.

“The new turbochargers and higher firing pressure are the key things that allow the engine to be optimised in a completely new way,” says Teir.

A number of components have been modified for the higher firing pressure and pressure ratio.

The pistons have been reinforced to give higher firing performance. Furthermore, the geometry of the top of the piston and compression ratio have been optimised to give the optimal combustion space.

The cylinder head, which is a common design for diesel, DF and SG engines, has been reinforced. So has the crankshaft, for the higher firing pressure. The stronger camshaft increases output in both diesel and gas mode.

Reinforcement of the main engine block was also necessary to carry the new higher capacity turbocharger. In addition to a stiffer engine block, the main bearing caps and large studs that hold the engine together have been reinforced to accommodate the higher firing pressure.   

The engines feature advanced Miller timing and variable inlet valve closing.

The variable inlet valve allows Miller timing to be switched on or off. Miller timing is advanced inlet valve closing i.e. the inlet valve is closed before the piston has reached the bottom of the cycle.

Variable inlet valve closing provides optimum load response at low loads. This is very beneficial on ships where there the propulsion system experiences fluctuating loads in rough seas.

Teir explains: “If you have a ship with four engines and there is poor load-taking on all engines, you could face a situation where you need to have additional redundancy in the form of a fifth engine to take the dynamic load fluctuations. If the engine has more robust load-taking, these situations can be handled with fewer engines.”

Better dynamic load response will also be a bonus in the power industry, where engines are increasingly used for grid stability or standby applications.

POWER CUBE IN PERU

Since its introduction, the Wärtsilä 34DF has proved to be a popular engine. At the heart of Wärtsilä’s ‘Power Cube’ solution, it provides users with a pre-engineered power plant within the cost-effective framework of a turnkey delivery.

A recent project involves an order for a Wärtsilä 34DF Power Cube to be installed at an open cycle gas turbine power project in Eten-Chiclayo, 750 km north of Lima, the country’s capital. The project’s sponsors are Cobra, a subsidiary of the Spanish construction group Grupo ACS, and Empresa de Mantenimiento Construccion y Electricidad (EMCE), a part of the energy division of Terra Group. The entire plant will be owned and operated by Terra Group, an energy conglomerate for Central America.

The open cycle plant will be based on a GE 7FA.05 dual-fuel gas turbine with an output of 218 MW. One of the technical requirements is that the plant must be capable of black-start operation i.e. without power from the grid. This means the plant requires a generating unit to provide the power needed to start the gas turbine. The size of this starting generating unit has been estimated at 8-10 MW.

Jyrki Anturaniemi, Power Plants Proposals Manager, Americas, said that the Wärtsilä 34DF engine is not only the right size for the job. It also meets the owner’s requirements for a package that offers high efficiency, complete fuel flexibility and can be delivered quickly.

Moreover, it satisfies the owner’s need for a compact, space-saving and fully engineered solution. The plant owner will be paid according to the emergency plant’s installed capacity.

Taking into account the highly flexible dynamic capabilities of the Wärtsilä 34DF, the owner decided to use Wärtsilä’s generating unit not only for providing black-start power, but also for delivering additional megawatts when the entire plant is operating, or when the system operator orders it. This would give the plant a total generating capacity of 218 MW + 8.2 MW.

The Power Cube therefore has two startup scenarios:

1. Standard start up: The plant is connected to the grid, where both the gas turbine and Wärtsilä engine take power from the grid to start and synchronize with the grid and go to full load, or the required load.

2. Black-start: The plant is disconnected from the grid; the Wärtsilä 34DF engine starts first to provide power to start main turbine. 

The entire plant is known in Peru as a ‘cold reserve’ plant. For such an emergency plant, there is no set number of operating hours each year. For emissions modelling and warranties, however, the plant owner has estimated it will be 10% of a baseload plant, i.e. about 800 h/year.

As the Wärtsilä engine will also be used during normal operation, it has to fulfil the technical requirements included in the concession contract: dual-fuel, efficiency above 32%, power factor (PF) of 0.8, etc. Meeting such requirements is straightforward and calls for no special effort from Wärtsilä.

In terms of black start operation the power output is described in a load profile that Cobra has provided to Wärtsilä. The profile is according to the power needed by the excitation system of the turbine. Wärtsilä has simulated the responses in voltage and frequency successfully. 

Wärtsilä dual-fuel engines

Wärtsilä 34DF

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