DNV GL’s new tool helps overcome quality issues and protect engines by calculating the PKI methane number.
The PKI Methane Number Calculator can support ship operators in quantifying the effect of LNG quality on engine knock, thus to helping LNG users to ensure safe and efficient engine operations.
Engine knock is characterised by auto-ignition of the unburned fuel mixture, known as the end gas, ahead of the propagating flame in the engine cylinder. The knock resistance of LNG is characterised by a methane number, similar to the octane number used in gasoline engines. Users of the tool simply enter LNG composition information such as nitrogen, methane, ethane, propane, and n-butane, and the tool calculates a PKI methane number using an algorithm which can be matched with the engine specification.
The algorithm has been shown to give a significantly more accurate reflection of the impact of variations in fuel quality on engine knock than traditional tools. It can also be readily incorporated into an engine-control system to maximise knock-free performance when supplied with a wide range of fuel.
DNV GL’s Senior Vice President, Oil & Gas, Liv Hovem, says: “As LNG is produced at different locations around the world, using an assortment of production technologies, its composition can vary considerably. Determining its fitness-for-purpose can be difficult and the consequences of mismatching fuel quality to a specific ship engine can cause potentially dangerous effects such as significant loss of performance, engine shutdown and even damage. Knowledge of the knock characteristics of LNG fuels is therefore crucial for suppliers and traders to provide reliable and efficient products and to break down the perceived barriers of adopting LNG.”
He also said: “Step by step DNV GL is facilitating the removal of barriers hindering the safe and efficient adoption of LNG as fuel and the creation of an open and free LNG marketplace. Our cross-industry collaborations in this arena have already seen the development of a number of recommended practices relating to gas quality and bunkering. Our collaborative efforts will go a long way to increase knowledge and remove any remaining concerns about the adoption and application of LNG as a viable fuel for the future.”
DNV GL has also launched a joint industry project (JIP) to develop tools to support customers in investment decisions on the design of small-scale LNG distribution infrastructure. The project will perform economic and supply chain optimisation analyses to improve knowledge on LNG transportation, storage, quality, and safety.
The classification society also recently undertook a study on the LNG market in the EU as part of its efforts to drive the development of an EU-wide network of LNG refuelling points.
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