Digitalizing Fuel Efficiency over Engine Efficiency: Integrating Technology to Measure Consumption

By: Rob Mortimer, Director, Fuelre4m

Modern ships are already starting to bristle with technology to measure vessel efficiency, yet one thing stands out over all the results, tech and noise. The importance of the efficiency of fuel isn’t quite understood or calculated. You’ll hear reference back to SFOC (Specific Fuel Oil Consumption) at any time fuel consumption is measured, yet while the principal is right, the measuring and calculating is far from ideal.

Heavy Fuel Oil has an energy density of between 39MJ/kg and 42MJ/kg when burnt. That’s a wide range and depends very much on the source and quality of the fuel. How is it stored, transferred, settled, heated and purified to remove pollutants, particulate, water and reduce the ‘drop’ size to help with better atomisation when introduced into the engine. Large drops of fuel don’t fully combust in the engine. They undergo secondary combustion and turn into heat energy and emissions. Our goal, and what should be the goal of the whole shipping industry, irrelevant of fuel, vessel size and function, should be to be able to account for every drop of fuel consumed.

The Fuel System Lockdown:

MFM Bunker to Bunker

The first challenge is to know and agree what is being bunkered onto the vessel in the first place. To know the mass of the bunker, we must be using a correctly ranged Mass Flow Meter.

MFM Bunker to Settling Tank

When using Fuelre4m’s Re4mx Fueloil re4mulator, we need to dose the correct amount of product for the weight of fuel that is being treated either in the bunker or in the settling tank.

MFM Settling to Purification

 Having a mass flow meter after the settling and before purification isn’t wholly necessary, but can be beneficial in understanding the temperature and density of transferred fuel, as well as understanding what the percentage of water and waste material has been lost to this point.

MFM Before Mixing Column, Pre Main Engine – Fuel In

This is the last reference check point of the fuel before it is injected into the engine. What will be reported as accurately as possible from this point will be how much fuel by weight is now passing through for combustion.

MFM Post Main Engine – Fuel Out

To understand the fuel consumption of the main engine, it’s important to be able to measure as close to the Fuel In and Fuel Out points as possible. Fuel consumption of the Main Engine should be as simple as MFM IN minus MFM OUT.

Torque / Shaft Power Meter

So, we’ve locked down the mass of the fuel flowing into the engine, now how do we measure the power produced?  Despite how it sounds, a torque meter does not measure torque. It simply measures time and distance. As forces against the propellor change, the amount of power needed to maintain the same turning speed will also change, and the propellor shaft with ‘twist’ with torque.

Why is the ranging important? Because the maximum power rating of the engine changes depending on the quality of the fuel and the energy it can release.

If your fuel produces 1kWh for 160g, 1000kg of fuel will produce 6,250kWh of power. If your fuel produces 1kWh for 180g, 1000kg of fuel will produce only 5,550kWh of power. If the maximum Fuel In capacity of the engine, from where the power rating is calculated, is 1000kg, your maximum power rating of that engine, and with it, the SFOC, has now changed.

Power Cards / Power Curves

The taking of indicator cards, allows the ship’s engineer to receive more information about the combustion process (via the draw or out of phase card), measure the cylinder power output of the engine (via the power cards), and check the cleanliness of the scavenging process (via the light spring diagram).

For the purposes of measuring the efficiency of the fuel, the power cards can be used to calculate the energy release of the fuel. This can then be used to build an algorithm to ‘range’ or adjust the power readings from the torque meter to the quality of the fuel.

MFM Auxiliary Engines – Fuel In

The auxiliary engines, strangely, are probably the easiest to prove fuel efficiency and the efficiency of the fuel on. Why? Because they’re generating electrical power that can easily be measured.

MFM Auxiliary Engines – Fuel In

A common fuel flow in and fuel flow out MFM will suffice if all of the auxiliary engines are sharing a common fuel flow system.

Auxiliary Engines – Constant Power Meter

Being able to monitor the amount of power produced at a given moment is not enough. Electrical loads can vary, and at the time once an hour that the kW reading is taken, or the kWh counter is recorded, the load just two seconds later could change. The fuel consumption for 100kWh over 3 minutes is vastly different than 100kWh over 1 hour.

Boilers & Cargo Offload Systems

Some vessels use boilers to generate steam power, running off the same fuel as the main engines. It is important to lock down all fuel consumers to understand where the fuel is being consumed.

MFM Boiler – Fuel In

Often fed straight from the settling tank without needing to go through further purification, the boiler directly combusts the fuel to generate steam from water.

To be able to calculate the boiler and fuel efficiency, we now need to firstly look at how much fuel in mass is being consumed.

Volumetric or MFM – Water In

Fresh water has a very well-known density of 1g per ml, but this is also affected by temperature. The use of a temperature compensated mass flow meter will improve accuracy of water used to produce the required steam.  

Recordable Pressure Gauge

The last variable? How much water and fuel is being used to produce the same amount of steam pressure.