Fuel Flow Meters: Monitoring Diesel Engine Fuel Consumption – Part 2

Fuel Flow Meters Diesel engines are becoming increasingly popular in a whole variety of power applications. For everything from generators, boats, trains through to hydraulic packs these power sources are becoming the unit of choice. Fuel consumption and efficiency are generally not monitored in Diesel Engines and the unit’s performance has to be gauged from the manufacturer’s test figures and often never checked again. With increases in fuel prices, the possibility of theft from remote installations along with many other factors. Consequently the monitoring the fuel consumption of diesel engines has become increasingly important with the transport industries in particular taking a lot more interest in their vehicles fuel consumption. Vehicle manufacturers spend a lot of time and effort checking the fuel consumption figures for the engine on dedicated dynamometers and later with very sophisticated mobile set ups. These fuel systems are very costly and are unsuitable for general use. On a typical diesel engine the fuel is supplied to the injectors at pressure from a “lift pump”, the injectors use the amount of fuel required for the engine load and return the rest to the fuel tank. If you wish to measure the amount of fuel used you simply need to place one fuel flow meter in the supply line and a second in the return line and use electronics to subtract the difference. Unfortunately the reality of making such a measurement is not so simple. The table and graph below illustrates a hydraulic power pack running at fairly constant speed. This makes the metering somewhat easier as the ratio of maximum to minimum fuel consumption is quite small. A commercial road vehicle however would typically have a much larger ratio compounding the metering problems.