Recirculating Fuel and Efficient Bubble Elimination Increases Fuel Measurement Accuracy
In an attempt to measure actual fuel consumption, early designs of fuel measurement systems employed two flow meters; one would measure supply fuel and the other, return fuel. By subtracting the return fuel from the fuel supplied, a consumption rate was derived. This technique is subject to large errors—especially during idle or lower rpm settings.
Example, using two flow meters, each with nominal 0.5% measurement error, a supply rate of 100 lb/hr and a return rate of 90 lb/hr produces a potential error of 0.5 lb/hr and 0.45 lb/hr respectively. Combined, these become a potential error of 9.5% when compared to the actual 10 lb/hr consumed.
Max recommends a fuel measurement system that avoids these errors by recirculating the return fuel into a Series 370 Level Controller before returning it to the engine.
When plumbed in the Level Controller configuration, the Model 370 products serve as a vented, recirculation tank to collect return fuel and route it back to the supply side of the engine. A float-activated, precision valve opens to control the flow of "make-up" fuel into the Level Controller. This "make-up" fuel passes through the single Max flow meter, providing accurate measurement of the actual fuel consumed.
- Internal plumbing reduces turbulent flow and consequent foaming.
- Efficient venting of return fuel vapors.
- Open to atmospheric pressure – eliminating back-pressure on the engine return line.
- Smooth float action maximizes stability of instantaneous readings.
- Models sized to consumption of 1.9 and 2.2 liters per minute, with recirculation rates of 2 and 3 liters per minute, respectively.