A false ceiling for engine design
Modern ship engines are often significantly over-specified because they are optimised for unrealistic operating requirements, according to a leading engine designer.
“We need an artificial 100%.” Not a suggestion to a dictator’s election committee, but a design plea from one of the pioneers of modern engine technology. According to Ingemar Nylund, a key player in the development of four-stroke and then two-stroke dual-fuel engines for Wärtsilä and WinGD, the industry’s demand for optimisation across a wide operational field – particularly at full load, which may never be reached in practice – results in engines that are not optimised for the actual operation of modern shipping. A different rating strategy could result in more efficient engines.
Even before slow steaming, ships rarely reached 100% engine load. But ship specifications often demand fuel efficiency and environmental compliance at a range up to full load. Nylund believes that if engines were designed and tuned for the real operating point, rather than for a wide (and artificially high) range, designers could achieve greater efficiency.
The problem is compounded by the inherent caution of shipping, with further safety margins often required. The result is engines that are often significantly over-specified. Though such vessels may never have to fear being under-powered, their engines will be bigger and more expensive than owners need, and performance will not be optimised for their actual operation.
It’s a perspective that ship owners would do well to heed as the next stages of IMO’s Energy Efficiency Design Index kick in. Optimising at 85% of engine load, say, will mean 15% of engine power in reserve to speed out of difficult situations, without having to factor in a margin at full running. The result will be more carbon-efficient and, in the long run, smaller engine installations.
In the long term, the use of batteries may mean that engines never need to deviate from a single optimised load point. For example, ships could run their engines for a set time each day, charging batteries to power the ship for the remainder of the day (as well as taking any unexpected peaks during engine running).
It’s an insightful perspective from an engineer who, through his work on LNG-burning engines, set the course for a burgeoning marine fuel revolution. Convincing the market to specify for lower, narrower engine loads could drive another radical change in ship powering.
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