High-Speed Gas Engine for Marine
MTU’s new gas engine for marine applications has passed 3000 hours on test bench and will power Damen harbor tug boat for Svitzer shipping company
MTU Friedrichshafen, part of Rolls-Royce Power Systems, presented a new gas-powered high-speed marine engine Series 4000, which just completed 3000 hours on the test bench and is going to be put into operation at the end of 2017 on the first tug boat powered by high-speed gas engines by Damen Shipyards in the Netherlands.
The 16-cylinder engine S4000 gas engine will cover a power range from 1500 to 2000 kW and is based on the MTU 16V 4000 M63 diesel engine for workboats, MTU said.
The gas engine portfolio by MTU will be further expanded and will initially include an eight-cylinder engine—8V 4000—with power ratings from 750 to 1000 kW. In 2019, this engine will be used for the propulsion of a pure liquefied natural gas (LNG)-powered ferry on the Lake Constance, Germany, operated by the local public utility Stadtwerke Konstanz.
The RSD CNG tug boat by Dutch shipyard Damen will be powered by the MTU S4000 marine gas engine. The Reverse Stern Drive (RSD) tug can sail ahead and astern with the same bow height forward and aft and is designed for harbor ship handling.
The project with Damen Shipyards, in cooperation with Danish shipping company Svitzer, will launch the Reverse Stern Drive (RDS) compressed natural gas (CNG) tugboat, a world’s first according to André de Bie, senior design & proposal Engineer tugs, at Damen Shipyards.
De Bie explained that the RSD concept is a specific design for harbor ship handling, with tug boats below 20 m lenght. “Our RSD tugs are capable of sailing ahead and astern with the same bow height forward and aft.”
Damen is building three diesel RSD tugs (with MTU S4000 diesel engines) and the one CNG tug. The latter is part of the Horizon 2020 funding project by the European Commission that includes other projects for the development of ‘lean ships.’
The S4000 marine spark-ignited gas engine by MTU adopts multi-point (MPI) gas injection valves for a higher flexibility in managing the injected air/gas mixture. Jörg Breuer, development gas engines at MTU, and Peter Kunz, project manager MTU mobile gas engines, said that the MPI-valves can control several parameters, as for example the start of injection and the gas rail pressure.
“This is a fundamental feature to obtain combustion stability at each engine operating point,” Breuer said.
Since each cylinder is injected by its own MPI valve, a precise combustion control per cylinder is possible. “The observation from our testing of the S4000 marine gas engine showed that the management of in-cylinder individual burn rate minimizes the scatter band of cylinder individual pressures,” added Breuer. “With controlled combustion, the pressure delta among the 16 cylinders is contained within about 10-15 bar. We observed that the same engine without controlled combustion can show pressure deltas of over 40 bar.”
The precise control of the maximum firing pressure is a fundamental aspect to eliminate knocking with a richer gas mixture, while the control of the mean effective pressure insures more stability. In any case, controlled combustion allows for a reduction in fuel consumption and CO2 exhaust emissions.
In fact, in terms of emissions, testing showed a potential for 11% greenhouse gas emissions reduction compared to the same engine fueled with diesel, in a typical tug boat operational profile. The benefit is higher, and can reach up to 100% with liquefied biogas fuel.
The S4000 marine gas engine also adopts double-walled fuel piping (that is an IGF requirement for a safe engine room—the inner chamber is flushed with air or filled with nitrogen to detect a leakage—and two single-stage turbochargers (one per each cylinder bank) with bypass valve and wastegate.
Peter Kunz, project manager MTU mobile gas engines, explained that an analysis of the engine transient behavior during tests showed that the S4000 marine gas engine has almost identical performance characteristics of the current S4000 M63 diesel engine. In particular load acceptance and acceleration curve are quite similar.
As far as operation with LNG is concerned, Kunz said MTU has launched a R&D project to develop a standardized system solution for ferries, tugs and workboats. MTU is teaming up with Rolls-Royce Marine to benefit from their vast experience in LNG propulsion and storage systems, with the aim of being capable to offer a complete solution, from the filling station, to the storage tanks with cooling box, to the gas regulation units and finally to the engine.
The executive vice president of Development at MTU, Dr. Andreas Lingens, said that the company is focusing research and development activities in different areas. One of them is the extension of gas engine technology beyond the current stationary applications to include mobile applications.
Lingens said that the company aims to improve its engine technology and to develop modular propulsion systems ranging from the gas supply system to the electrical propulsion system.
“With the full range of technologies we will have available in the next 20 years, we expect to reduce the emissions of gases that are harmful to the climate by as much as 50% and to cut health-damaging emissions by over 90%,” he said.
According to Lingens, the marine propulsion system of the future, depending on the type of vessel, mission profile and the cost and availability of fuel, will incorporate a diesel or gas engine as the prime energy converter.
“The powertrain will be electrified to a greater extent, as this will enable us to reduce fuel consumption in most of the real-life operational profiles and to provide electrical power for other on-board applications. There will of course also be ships operating solely on electric power for applications with short mission periods.
Big data will not be confined to future marine propulsion systems, but we will also see improved maintenance, early detection of malfunctions and the appropriate response, and autonomous operation.”
In terms of natural gas as a fuel, Lingens expects that some areas will adopt it as the dominant fuel when fuel cost is a major factor. He said that for continuous-duty power generation, gas engines have already virtually displaced diesels. MTU is testing gas engines for marine applications, but even locomotives, large pump engines and mining vehicles could be operated much more economically with gas. Lingens added: “One challenge is the fuel supply, that is the storage in tanks and delivery to the engine. But we will find ways around that. Apart from lower fuel costs, lower CO2 emissions and more economical emissions control for future emission stages are increasingly important aspects.”
Currently under development are 16-cylinder vee and 8-cylinder vee configurations for marine propulsion that will be compliant with IMO Tier 3. Depending on market demand, MTU will include a 12-cylinder vee and a 20-cylinder vee, with 1500 and 2500 kW at 1800 r/min maximum power output, respectively. Even gas engines with 8-, 12-, 16- and 20-cylinders for marine gen-sets are under consideration, the company said.