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1 (2015-08-11 14:08:27 отредактировано Mechatronica)

Тема: How fuel flow meters affects to diesel engine operation

Fuel flow meters – simple and precise method of real-time fuel consumption control. But fleet owners may be aware of some arising technical difficulties with engines and flow meters.

Let us give some advices.

Fuel flow meters can be single-chamber or differential (dual chambers).

Differential fuel flow meters:
diff


Single-chamber fuel flow meters:
direct

Differential flow meters can measure both supply and return flow. To install single-chamber flow meter on diesel engine you need to change fuel supply system. Only fuel consumption flow rate must pass via single-chamber flow meter, without return flow.

Here is a typical scheme of differential flow meter installation:

https://www.massflow-online.com/cms/wp- … Manual.pdf

Dif eng


There is no serious changes in fuel supply system. Fuel flow meter chamber flow resistance is low.   Nothing to worry about. But according to this scheme you need to install 2 non-return valves (check valves) – in each chamber of fuel meter. These valves usually open with pressure 0.25 Bar approx.
On big fuel flows these valves also add its hydraulic resistance. If bypass valve of engine opens at 1 Bar (sometimes even at 0.5 Bar), with check valves fuel pressure in supply channel is growing. And Low pressure fuel pump constantly works under higher pressure. Check valves also have a tendency to stuck.
Check valves are needed for flow meters based on reed switch sensor. Meter can see only one reed switch pulse per chamber rotation, so can’t detect its direction. Due to possible back-flow in fuel lines we need to install these check valves.


In Eurosens Delta we use several Hall effect sensors, per 1 measure chamber turn we receive 3 pulses. With this innovation we can detect direction of fuel flow and no need in check valves.
So, you can install only Eurosens Delta flow meter that have no any affect to fuel supply system.

Second issue with flow meter it is freezing of the fuel inside flow meter chambers in winter.

From installation scheme we can see that the measuring chambers are installed after the fuel fine filter, and through them a large flow of fuel is passing.

If the fuel is liquid enough to pass through the filter of thin clearing of fuel - it will pass through flow meter too. Perhaps short-term pause in flow meter operation is possible during cold start of engine at winter, but a large flow of heated fuel warms up quickly the camera, and the meter start to work.
Another weak point during winter operation is built-in small petrol filters used by several flow meter manufacturers. They are not suitable for diesel fuel. Their main function is to protect measuring chamber from dirt during installation. In the future, they become a potential weak point and place of fuel thickening at winter.
Eurosens flow meters don’t have such built-in filters, we recommend to use an extra external fuel filter by proper quality and volume.

Resume:
No any reasons to be afraid of Eurosens Delta fuel meters.
No any engine or fuel meter problems during everyday operation.

Now we will speak about single chamber flow meter installation.
Usually single chamber flow meter is installed like this:
direct eng

Conditions of high-pressure pump operation are changed:
1.    High-pressure pump is not cooling anymore by passing fuel flow
2.    Fuel tank is heating with less, because return fuel flow after fine fuel filter is cooler compared to return fuel flow from high pressure fuel pump (before modification).

In general, this scheme is OK, but sometimes you can face problems.
On this scheme we can see again non-return valve (check valve). It can create problems:
1.    This valve can stuck
2.    If bypass valve begins to operate with lower pressure and its pressure can be compared with check valve opening pressure – high pressure pump will be short of fuel. All fuel will return in tank without coming to high pressure pump. Engine will lost power.
3.    This check valve makes high pressure pump section completely isolate from bypass valve. It may cause hydroblows and immersion of fuel to lubrication system

So, we can recommend single-chamber Eurosens Direct PN fuel flow meter, equipped with Hall-effect sensors. Installation of non-return valve is not needed.  It simplifies fuel system and hydroblows are avoided, because all parts of fuel supply system are connected to bypass valve.

Eurosens Direct also has bigger metering chamber volume that increases operation life and adds some immunity to high viscous fractions of fuel  (at winter).
                                        DFM100(90, 50), VZP4          - 5000 mm3.
                                        Eurosens Direct PN100          -10000 mm3


Resume

Single chamber flow meters you can be used when:
1. Diesel engine is low-boosted, not equipped by electronic systems. Operation mode of high-pressure fuel pump will be changed.

2. There are no problems with high-viscous fractions of fuel in winter.
3. You want to save a little money (compared to differential flow meter).

We hope that our advices will help to make right choice and save a lot of money with help of precise and simple real-time fuel monitoring device: fuel flow meters.