All isn't totally lost within this diesel flow measurement application being an acceptable metering system is possible in a single of two ways. The very first involves an entire fuel system re-build and for that reason isn't usually practical. With this particular method another tank (see schematic below) is installed to get the return fuel with no attempt is built to measure it.
The engine draws fuel out of this secondary tank which is provided fresh metered fuel from the primary reservoir. The only flowmeter is just calculating the fuel provided towards the secondary tank and it has therefore needs to be capable of meter the consumption within the whole selection of the engine. Great care needs to taken to make sure that the fuel temperature doesn't rise excessively hence coming back flow intercooler is needed out of the box a considerable tank volume to make sure that there's no foaming and also the fuel isn't hot for that engine fuel system because this will reduce horsepower. This is often an accurate approach to measurement but it's not usually practical.
The 2nd metering system (see schematic below) uses two flowmeters and a lot of care in set-up, however the results still might not be acceptable in each and every situation. The option of flow computer is crucial. The selected flow computer should have flowmeter linearization on channels along with the capability to perform density corrections using pre-determined fuel characteristics and fuel flow and return temperature measurements. The flow sensors should, preferably, stay positive displacement and they ought to be very repeatable certainly much better than ±0.1% and when possible ±0.05%. Their calibration must have the minimum uncertainty and also the temperature coefficient for that meters ought to be known. The temperature sensors ought to be ±0.1% devices even though this measurement is sort of decreased within the finish result.
The outcomes from the previous error calculations claim that, with this system, in which the performance graph is extremely straight line, the general precision at full flow is 4 occasions the sensor precision and also at low flow it's also 4 occasions the sensor precision but multiplied through the flow range turndown, which within this situation roughly 5:1. When the sensors have ±0.1% repeatability variation and built-in temperature measurement, density and flowmeter temperature correction will be done by the instrument which itself includes a finite precision ( ±0.01%) we finish track of roughly ±0.44% at high flow and ±2.2% at low fuel consumption. This can be a a lot more acceptable diesel flow meter measurement result.
An additional factor may be the uncertainty from the calibration and will also change from flowmeter supplier to supplier. To provide guidance many national flow calibration facilities claim ±0.05% uncertainty but many provided flow meters are unlikely to become this good and ±0.1% to .25% is really a more typical range. Regrettably some suppliers flowmeters offer uncertainty that's even outdoors this range. The health of the engine can also be critical as indicated formerly if it's not in top class running order the return line could contain spurious levels of gas growing the apparent amount of the return flow. An electric train engine flow measurement system installed and properly monitored might be a helpful indicator for such engine decline or any other anomalies within the fuel system.
Different fuels may have different characteristics and altering the mixture of bio-diesel will modify the results. Any recording instruments should ideally have the ability to easily be altered to mirror the choice mixing ratios. Most of the characteristics of those blends are unknown because the qualities of each and every oil is determined by the growing conditions and also the processing and whether or not this originates from the neighborhood junk food outlet shop.