WinGD is evolving its popular two-stroke Otto-cycle engine for new IMO energy efficiency regulations and future fuel flexibility, backed by Wärtsilä long-term service
The low-pressure, two-stroke, dual-fuel X-DF engine has been a commercial success for Switzerland-based Winterthur Gas & Diesel Ltd (WinGD) since the first customer engine was delivered in 2015. Now, with some 400 X-DF engines in operation and on order and more than 1M operating hours under its belt, WinGD is pushing the development of its Otto-cycle engine even further.
At the webinar X-DF two-stroke engines – operational efficiency and future developments, panellists from WinGD and its long-term service partner, engine designer and builder Wärtsilä, examined the technology and emission profile advancements being made in X-DF engines.
The webinar featured presentations by WinGD general manager, head of global sales Carmelo Cartalemi, Wärtsilä Marine business general manager, agreement sales Jörgen Naajier and WinGD general manager, customer support Adrian Siegfried.
Kicking off the webinar, Mr Cartalemi provided a development timeline for the X-DF model, which began as a concept in 2011, when WinGD (Wärtsilä Switzerland Ltd) was still part of Wärtsilä. This was followed by full-scale testing of the RT-flex50DF engine (2014), first customer engine deliveries (2015) and sea trials (2016). An X-72DF technology demonstrator was initiated in 2015, with the first sea trials of the engine in an LNG carrier in June 2017.
In 2020, WinGD unveiled the next generation of the engine, X-DF 2.0, with a 50% reduction in methane slip and improvements in fuel consumption performance, both supported by Intelligent Control Exhaust Recycling (iCER) technology.
Since its introduction, the X-DF has built a presence in various LNG-fuelled ship types – Aframax tankers, VLCC, bulk carriers and shuttle tankers and container ships – and become “the standard” for LNG carrier newbuilds, Mr Cartalemi noted.
Among its portfolio is the world’s largest LNG-fuelled ship – the ultra-large container ship CMA CGM Jacques Saade. The 23,000-TEU, 400-m ULCS and its eight sister ships are each fitted with a 12X92DF engine, the world’s most powerful LNG-fuelled engines, which carries a maximum power rating of 63,840 kW.
The secret to success
The “secret” of the engine’s success, said Mr Cartalemi, is its low pressure. “This means we inject gas into the combustion chamber at 13 bar. The gas supply system is relatively economically convenient and, from a technology point of view, using the Otto cycle, we have very low NOx – much lower than the Tier III limits – and the efficiency is at a good level.”
While X-DF engines are IMO Tier III compliant out of the box, emitting low NOx emissions and virtually no SOx or particulate matter, critics of the technology point to its methane slip. Methane – a potent greenhouse gas – is some 28 times more powerful than CO2 on a 100-year timescale.
Mr Cartalemi addressed methane slip in his presentation highlighting the use of iCER technology, which allows the combustion process to be controlled and optimised for “the best gas fuel consumption” –
slashing methane slip in half – and improving liquid fuel consumption in diesel mode.
Introduced with its second-generation X-DF 2.0 engine, WinGD’s iCER technology captures the unburnt fuel (methane) before it is ejected through the exhaust, providing the engine a second chance to combust it.
There has clearly been a step change in dual-fuel engine technology in just a decade. “I remember 10 years ago, the standard methane slip for the industry was 6.0 g/kWh. Today, with X-DF 2.0, we are below 1 g/kWh – 0.8 g kWh,” he said. “This is an important step forward.”
Using iCER technology, there has been significant fuel consumption gains in both gas and diesel mode, particularly in partial loads between X-DF 1.0 and X-DF 2.0. For example, in gas mode at a 40% load, a second-generation 5X72DF engine, rated at 11,400 kW at 74 rpm, would consume 6.4 g/kWh less than a first-generation X-DF engine. In diesel mode, X-DF 2.0 outperforms its predecessor, too. In partial loads, it ranged from -8.1 g kWh at 40% to -5.7 g kWh at 80%.
“The secret of the engine’s success is its low pressure”
In concluding, Mr Cartalemi said: “This is the first step in decarbonisation. We’re also considering alternative fuels to burn on the same engine platform.”
On cue, a webinar poll asked delegates ‘A future-proofed main engine should be able to operate with the following fuels?’ Audience members choose LNG/bioLNG and hydrogen as the top answers, each garnering 29% of the vote, followed by ammonia (28%), methanol/ethanol (9%) and biofuel (5%).
Operational lessons learned
Wärtsilä serves as the long-term service supplier for WinGD engines and the Sulzer two-stroke diesel and gas engines. Highlighting Wartsila’s ability to be responsive to shipowners’ service needs during Covid, Mr Naajier said: “90% of issues were resolved remotely, 80% of which were done within a day.”
Mr Siegfried highlighted some learnings from operating experience regarding the root causes of cylinder scuffing that occurred in 2019 and 2020 on mid-bore DF engines.
“We were able to trace these incidents to water ingress into the cylinder liner through the pre-chamber,” said Mr Siegfried. He noted what he characterised as a “design flaw” in one of its most popular engines, the X72DF engine, which was resolved by adopting the design to the same dimensions as in the X50DF, X52DF and X62DF engines. “The whole fleet was upgraded,” he said.
Other issues encountered related to the cylinder lubricants – originally used on diesel engines – which were found to be not suitable for the Otto-cycle combustion process, resulting in deposits and sticking cylinders. This was rectified with new cylinder oil formulations. Additionally, high cylinder liner wall temperatures affecting the behaviour of the cylinder lubrication were resolved with an enhanced cooling system.
Mr Siegfried detailed WinGD’s four new variations of the X72DF that were launched in February.
Alongside baseline design improvements to the platform, an option is now available to optimise lower power output in five- and six-cylinder configurations, which are also available with enhanced methane slip-reducing X-DF2.0 technology.
The base version, X72DF-1.1, incorporates the enginebuilder’s new engine control architecture, WinGD Integrated Control Electronics (WiCE). Among the engine modifications are the addition of a modular scavenging concept to improve control over combustion and emissions.
For five and six-cylinder engines, further optimisation is available to improve efficiency at lower power outputs. The X72DF-1.2 features a selected power/speed range with a lower specific fuel consumption. This lean burn engine is designed for LNG carriers and other vessel types in need of limited installed power, in line with the IMO Energy Efficient Design Index (EEDI) for newbuilds and Energy Efficiency Existing Ship Index (EEXI) for existing vessels.
The option of reduced power rating and limited cylinder configuration enables a more compact design, with a shorter thrust section, an optimised gear drive and a smaller fuel supply unit contributing to reduced engine length. This equates to greater flexibility in the engineroom and more versatility for the ship design. The X72DF-2.1 and 2.2 have been specifically tailored for LNG-fuelled vessels.
Pointing to the future and shipping’s path to decarbonisation, Mr Naajier said: “Today’s choices have a long-term impact. There is a need for flexibility for fuels.” He said this in turn means “the complexity is increasing; that has a direct effect on how you operate these installations. You need to adopt to the new technologies, but you need to adopt to the new environmental regulations.”