Monitoring Diesel Engine Fuel Consumption with Fuel Flow Meters

As carbon footprints and green-thinking come to mind, so does the inclination to steer away from gas engines and turn towards diesel fuel. Because of this, diesel engines are increasingly becoming utilized as a whole for a variety of power applications, such as:

  • Generators
  • Boats
  • Trains
  • Hydraulic packs
  • And more!

Monitoring Diesel Fuel Consumption Efficiency to Improve Performance Data

However, fuel consumption and efficiency are generally not monitored for diesel engines, which in turn compromises the unit’s performance data. This must be gauged from the manufacturer’s test figures and then is likely never checked again.

Following the increase in fuel cost and spending, the possibility of theft from remote installations or any other factors is certainly high. Consequently, monitoring the fuel consumption of diesel engines becomes progressively important for transport industries in particular.

Vehicle manufacturers also take much time and effort checking their fuel consumption figures on dedicated dynamometers and sophisticated mobile setups for their diesel engines. These fuel systems are not only extremely costly but also are unsuitable for general use.

Flow Meters Streamline Calculating Diesel Engine Fuel Efficiency

On quintessential diesel engines, the fuel is supplied to the injectors at pressure from a “lift pump.” The injectors use the amount of fuel that is required for the engine load and return the remaining to the fuel tank. If the intention is to measure the amount of fuel used, it is very simple to place a single fuel flow meter in the supply line and one in the return line, using the electronics to subtract the difference.

Making this measurement, however, is not an easy task. The table below shows a hydraulic power pack running at a relatively constant speed, making the metering somewhat easier, as the ratio of maximum to minimum fuel consumption is small. Meanwhile, a commercial road vehicle would typically have a larger ratio compounding the metering issues.

Engine power Fuel consumption “Lift pump” Flow Return fuel Flow
kWm lph lph lph
970 224 570 346
880 202 567 365
660 151 560 409
440 102 555 453
220 54 550 496

Diesel Engine Fuel Consumption

Courtesy of Titan Enterprises

An example: if two low accuracy fuel flow meters in the flow and return lines of a diesel engine each have an accuracy of ±2% of reading and the instrument performing the subtraction is absolute, the figures are shown in the chart with the possible reading bands within the accuracy of the fuel flow meters.

Choosing the Right Fuel Flow Meter for Your Application

In terms of diesel engines, fuel flow meters measure the amount of fuel input into the system. The consumer is then able to visualize the amount of fuel in the engine. Fuel flow meters can have an analog or digital display. Not all flow meters are created equally. As such, they can differ in the accuracy of the data they provide. Flow meters take the flow rate of a given liquid — in this case, diesel fuel — into account. Unless the diesel engine is being used for heating applications, flow rate is typically measured in liters per minute. 

Deciding on the best right fuel flow meter for your application depends on the amount of fuel in the system. Standard diesel flow meters have a maximum flow rate of 120 lmp, while a larger system, such as heavy machinery, may require a flow meter with a higher maximum flow rate of 500 lmp. The above table will help users determine the most accurate flow rate meter for a given application. 

Reflect On Accuracy vs. Repeatability

When choosing a flow meter for a given application, it’s important to reflect on the accuracy of the chosen device and the possibility that the results could become less accurate over time. In general, if you are given the choice between an analog flow meter and a flow meter with a lot of moving parts, it’s advisable to pick the flow meter with as few moving parts as possible. Flow meters with a lot of moving parts can create too many variables; this can create something known as “slippage” in the measured flow. If the flow meter will be exposed to frequent fluctuations in temperature, that’s an important factor to consider as well. 

For more information about monitoring diesel engine fuel consumption, please contact JLC International today. Our experts are also able to explore any details pertaining to air velocity transmitters, shaw dew point meters, or even industrial humidity sensors.