BOS Emulsified Fuel System (EFS) makes fuel savings

Introduction

The price of marine fuels has skyrocketed in recent years from about USD400/mt for HFO in 2010 to more than USD600/mt today. Reducing fuel cost has become one of the priority of shipowners. Different technologies claiming fuel savings ranging from 2% to more than 10% are been marketed to ship owners looking for every means of saving every drop of fuel. These include: emulsified fuel systems, self polishing paints, air bubbles hull lubrication, all types of stern and propeller vortex/drag reducers, bulbous bow optimization, fuel and lubricant additives, sludge homogenizers, slow steaming, , engine de-rating, low temperature heat recovery, dynamic trim systems, voyage/fleet management and optimisation and so on. Test results at sea trails are frequently obfuscated by changing weather and sea conditions. Ship owners can be overwhelmed and it can be daunting to figure out who to trust with the myriad of claims. Therefore, it is imperative that there must be a reliable and accurate method of verifying the savings claimed, to separate the wheat from chaff.

Why BOS EFS works

BOS EFS works by producing stable water-in-fuel emulsions to improve injector fuel atomisation and combustion efficiency.

The key innovation of BOS EFS is the patented emulsifier which is superior to older devices like homogenizer, cavitation and ultrasonic type emulsifiers. Unlike the older devices, BOS emulsifier has no moving, cavitating or vibrating parts that suffer from rapid wear and tear in the engine room environment. It is designed to produce optimal emulsions on demand to achieve 2-5% fuel savings consistently and reliably. The optimal emulsion has water content of 10% v/v and water-in-fuel particle sizes of 2-8 microns. In a HFO fuel system, unconsumed emulsified fuel after the engine, is re-circulated back to the close-loop fuel system. The BOS emulsifier re-emulsifies the re-circulated water-in-fuel emulsions to exactly the same optimum emulsion of the 10% v/v water content and water-in-fuel particle sizes of 2 to 8 microns. BOS emulsifier is able to achieve this consistently and reliably because of two design characteristics which were developed after extensive R&D:

the water content is control automatically using feedback control to ensure accurate dosage of water even in extreme fluctuations of fuel rates;
it is designed parametrically to ensure sufficient energy to break the water particles to below 8 micron but not with sufficient energy to smaller than 2 micron.

Older type devices would produce water-in-fuel particle sizes that are either too small (due to repeated re-emulsification) or too big (due to wear and tear). This is the key reason why BOS EFS works while others do not, when decades of comprehensive R&D and proven laboratory tests were applied to actual ship board implementations.

Reliable and accurate verification

Since the 1980’s, it has been recognized that the fuel consumption measurement on ships has been inaccurate and ship owners had viewed the results with distrust. The poor reliability and inaccuracy then, were due to a large extent, to the lack of reliable and accurate instrumentations like flow meters and power meters. There were also no common standards nor references for measuring the performance of ship’s engines at that time. Since then, ISO 3046 and ISO 15550 have been established to provide the common standards to measure and determine the performance of engines. The results are generally plotted as specific fuel consumption (gm/kW-hr) against power (kW). The specific fuel consumption curves allow the fuel efficiencies of different engines to be compared on a apple-to-apple basis.

In applying ISO 3046 and ISO 15550 to measure the performance of the engine at sea, many parameters need to be measured and recorded. Some of the parameters are: speed over ground (SOG) ,speed through water (STW),wind speed and direction,

wave height and heading, draft fore and aft (trim),engine power,engine RPM,fuel consumption rate,fuel temperature at flow meter, fuel viscosity, fuel temperature after viscometer and before engine, fuel governor/racks indices, ambient temperature, barometric pressure, relative humidity, sea water temperature or charge air coolant temperature, lower calorific value of fuel, energy consumption of auxiliary equipment,% water content, etc.

Generally, the wind speed should be less than 15 knots and the sea state should below 4 Beaufort during each measurements. It can be seen that the measurement of engine performance at sea can be fairly complicated because many parameters must be measured and recorded. Determining the % improvements of engine performance when fuel saving technologies are implemented can be even more complicated because some of the uncontrollable parameters like weather and sea conditions must be the same in order to compare apple with apple.

ISO 3046 and ISO 15550 are sufficient to meet the requirements of ship owners for determining the performance of the ship’s engines against that guaranteed by engine manufacturers. However, the permissible error of +/- 3% inherent in the methodology provided by ISO 3046 and ISO 15550 often exceeded the % savings claimed by fuel saving technologies, rendering a situation reminiscence of the 1980’s. Ship owners are again distrustful; it can be difficult to know who to trust with the myriad of claims while there are no sufficiently reliable and accurate methods to measure the % fuel savings.

ISO 3046 and ISO15550 do provide a reliable methodology that served their intended purpose well. The maritime industry should not throw the baby out together with the water. What is needed is more than just to measure the engine performance. What is needed is to measure the change in performance of engines reliably and accurately. The existing ISO standards can be tweak to enable the existing methodology to achieve this goal.

To ensure a reliable and accurate measurement of change in performance of engines, two issues need to be addressed, namely theeffects of weather and sea conditions

and good repeatability and accuracy.

The common practice of measuring the improvements in the performance of the engine is to first determine the baseline reference performance curve of specific fuel consumption against Power . Then, the new performance curve is determined with the new fuel saving technologies installed. The improvements in performance are then derived from the differences between the two performance curves. There are two problems associated with this methodology. Firstly, the weather and sea conditions may not be the same when each performance curves were measured. Therefore, the results may not be repeatable even when ISO 3046 are applied to correct the test results to the reference conditions. Secondly, with the % change derived from two performance curves, the errors of the derived % change are increased (the increased error is the square root of the sum of the squares of each errors) as illustrated below; which means, the results are unreliable and inaccurate.

Total error of drived % change, Error_total= √[Error ²_curve1 + Error ²_curve2 ]

The better methodology adopted by BOS is to measure the % improvements in engine performance directly (instead of deriving them from two curves) with sample size of at least 25 measurements for each Power, so that the standard deviations can be used as a reliable and accurate measurement of errors. .

As BOS EFS can be switched OFF and ON easily, a single measurement of % improvement in engine performance at a particular Power (for example, at 75% load) can be easily measured directly by comparing the specific fuel consumption corrected to ISO 3046 reference, with the EFS OFF (i.e. burning neat fuel) and then with the EFS ON (burning emulsion). Generally, it takes 10mins to obtain a reliable measurement with BOS EFS ON or OFF and 30 mins for the fuel system to stabilize in between switching the BOS EFS from OFF to ON or vice versa. Total time to take one measurement of % improvement in engine performance at a particular Power is less than 1 hr. 25 sample size is obtained by repeating the measurements 25 times or in about 1 day. The big advantage of this method of measuring % improvement in engine performance is that it gives the ship owner a real feel of the improvement in engine fuel efficiency. The ship owner can see the improvement in fuel rates immediately under the same engine, weather and sea conditions, during the tests. This is something the ship owner can trust.

The curve of % improvement against Power is plotted by testing at, typically, 25%, 50%, 75% and 100% load. The complete curve can be plotted in 4 to 5 days of testing with good weather and sea conditions.

The key points are:

The objective of the methodology is to determine the % improvements in engine performance at different Power, not the specific fuel consumptions.
Each % improvement point is measured directly within a short time window of an hour, thus ensuring a high likely hood of stable weather and sea conditions. If the weather and sea conditions were not stable, that particular measurement shall be discarded and re-taken.
Each % improvement point is measured from specific fuel consumptions in the same time window (approx 1 hr). The specific fuel consumption measured at a particular time window will not be compared to another specific fuel consumption measured at another time window, thus eliminating the effects of weather and sea conditions.
The error of % improvement in engine performance at a particular Power is determined by the standard deviation of sample size of at least 25 measurements, thus ensuring good reliability and accuracy. (It can be of the order of 1% or better).
The methodology of measuring each % improvement in specific fuel consumptions within each time window of approx 1 hr complies with ISO 3046 and ISO 15550.

The above methodology provides ship owners with a reliable and accurate method of determining the % improvement in fuel efficiency which complies with ISO standards and which they can trust. The main point is that the % improvement in engine performance is measured directly; it is not derived from two performance curves.

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