How accurate engine pressure measurement ensures optimum vessel performance

Opinion | September 4, 2023

Rising fuel costs have made ships more expensive to operate, while tightening global regulations are putting pressure on reducing engine emissions. Bjorn Kindblom of ABB’s Force Measurement business looks at how ABB’s Cylmate pressure transducers maximize engine combustion performance, enhancing vessel efficiency and improving environmental performance.  

The stresses imposed by long periods of operation in a wide variety of operating conditions can take their toll on diesel engines in shipping applications. With potentially thousands of miles between ports, and the need to keep to delivery schedules, the last thing any crew wants is an unexpected engine failure while at sea that could cause potentially long delays and missed collection and delivery deadlines.    

Combined with this is the need to meet increasingly stringent environmental legislation that is putting tighter controls on emissions at sea. The International Maritime Organization (IMO) has introduced a strict cap on sulphur emissions, cutting the permitted levels from 3.5 percent to 0.5 percent. In the long run, the industry will also have to achieve a 40 percent target for cutting greenhouse gas emissions by 2030 compared to 2008 levels. While this is being partly achieved by the introduction of cleaner lower sulphur fuels, there is a need to ensure that engine combustion performance is also maximized to help further lower emissions.  

With fuel costs representing a significant proportion of total operating costs, especially as prices continue to rise, it is also essential for shipping operators to keep a close eye on engine performance to maximize fuel efficiency.  

 

The importance of accurate engine pressure measurement

Ship engines typically run for days, weeks or even months without stopping, either for propulsion or for generating electrical energy. With this constant operation increasing the risk of wear and tear that could affect engine performance and increase the risk of excessive emissions and impaired fuel efficiency, it is important to be able to identify any problems before they can escalate. 

One way to do this is by measuring the combustion pressure in the engine cylinders. An engine in good balance will avoid thermal and mechanical overloads by assuring equal power distribution between the cylinders. By effectively sharing the load, wear and tear is reduced and fuel efficiency is improved. An optimized engine will also make it easier to comply with environmental regulations. If the engine balance is impaired, all these benefits will be lost, increasing maintenance requirements and running costs, reducing fuel efficiency and potentially risking compliance with emissions legislation.   

To help ensure that engine performance is maintained at optimum levels, ABB’s Cylmate pressure transducers can be used to provide real-time measurement of the combustion pressure in each cylinder, continuously and in parallel, under all load conditions.  

 

How do Cylmate pressure transducers work?

The Cylmate pressure transducer is based on the proven Pressductor magneto-elastic technology, which uses the mechanical forces that change the magnetic properties of a ferro-magnetic material to provide an induced voltage proportional to the applied force up to a given value. When attached to the cylinder’s indicator bore, the Cylmate pressure transducer can be used to provide a continuous overview throughout the complete combustion cycle.    

The transducer features a thin-walled Inconel tube contained within a sensor that uses the Pressductor technology to measure changes in the cylinder pressure. These changes are measured and used by the autotuning system supplied by the engine designers.  

Designed specifically to continuously monitor the performance of two stroke diesel engines in both marine and power plant applications, the transducers can continuously measure combustion pressures up to 250 bar at high temperatures to an accuracy of within 0.5 percent.  

Compared to many standard membrane-based pressure transducers, the measurement performance of Cylmate transducers is not affected by any clogging or heat flash from combustion gases, enabling them to provide an accurate indication of the true cylinder pressure. 

To give some idea of the importance of enhanced accuracy on engine performance and fuel consumption, consider that a deviation of just 1.0 bar in Pmax pressure in a cylinder equates to 0.2 g/kWh SFOC (Specific Fuel Oil Consumption), potentially resulting in reduced fuel efficiency throughout the course of a voyage.  

 

High performance, reduced maintenance 

A key benefit of Cylmate pressure transducers is their robust design and reduced maintenance requirement. With a blow-through design that simplifies the cleaning of combustion residues that could otherwise affect pressure measurement accuracy, the transducer can operate for long periods without maintenance. If maintenance is required for cleaning, the indicator valve mounted on the top of the transducer can be opened to allow the tube to be blown through. 

Furthermore, because Cylmate transducers have no components that can age or deteriorate and are unaffected by pressure or temperature cycling, combustion gases or combustion deposits, measurement performance can be maintained around the clock without the need for any recalibration.  

The reliability of ABB’s Cylmate combustion pressure transducers for large two-stroke diesel engines enables them to offer maintenance- and calibration-free performance during years of continuous operation. In many cases, transducers installed for over a decade are still in operation, with no deterioration in accuracy or performance. As further support, all Cylmate transducers also have a five-year warranty.   

 

Summary

The need for operators to improve vessel efficiency will increase as costs rise and regulations continue to get tighter. As this happens, operators will need technologies such as Cylmate to help them find ways to make their ships more fuel efficient and sustainable.  

By supplying a highly accurate pressure signal from each cylinder in real time to the governing auto tuning system provided by the engine designer, Cylmate ensures that the auto tuning is always tuning the engine with the correct pressure signal to achieve optimum performance. By maintaining a good engine balance, operators can ensure maximum combustion efficiency with minimum wear and tear, improving fuel efficiency, reducing maintenance, and staying compliant with emissions regulations. 

This article was first published on rivieramm.com. 

 

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