evaluation of engine running data-new

7/25/2019 Evaluation of Engine Running Data-new

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Evaluation of engine running parameters

• Measured running parameters.

– Engine speed – TC speed

– Fuel rack position

– Charge air pressure / temperature – Pressure difference over CA cooler

– Pressure difference over cylinders

– Exhaust gas temperatures




Engine speed:

- Measured by cam shaft wheel, or flywheel.

- Unstably engine speed can be caused by wrong governor

settings, worn/jamming regulating mechanism.

- Engine speed controls pre.lub pump start and stop,

pre.heating start and stop, by-pass valve function.




• Alarm / safety blockings.

• Safety functions; clutch opening, over speed.




Turbo charger speed:

– An important factor to follow since the turbo speed gives

an indication when the nozzle ring gets dirty. I.e. the turbo

speed increases slightly.




Fuel rack position.

- Indicates amount of sprayed fuel oil (engine load).

- Increased fuel rack index (same load) can be result of worn

pump (bigger internal leakages) or change on fuel quality,lower heat value.




• Ignition quality parameters:

1. Energy

2. Viscosity

3. Maximum firing pressure.

4. Injection delay

5. Ignition delay .




• Energy comparison

• The injection pump is a volumetric pump

• The higher the density the more energy it contains per

volume unit

• The density difference between HFO and MDO is larger

than the difference in net calorific value




• Viscosity comparison

The viscosity of MDO is lower than the viscosity of HFO

(even HFO is heated)

• Lower viscosity fuels result in more internal leakage in the

injection pump from the high pressure side to low pressure

side.

• Internal leakage has to be compensated by giving more fuel

rack




• Maximum firing pressure

• Dependent on the charge air pressure

• To achieve proper combustion, the firing pressure has to be

high and thus also the charge air pressure• Timing of the fuel pump




• Injection delay is the time it takes to build up a pressure

higher than the opening pressure of the nozzle.

• Normally 4...5 ° of crank angle

• The delay is comparable to the condition of injection

equipment




• Ignition delay is the time gap between the commencement

of injection and the commencement of ignition.

• Dependent on the fuel quality

• Compression temperature has a big influence on the

ignition delay

• Compression temperature is not high enough for the fuel to

ignite longer ignition delay




Higher peak pressures and higher exhaust gas

temperatures.

• Normally 1...2 ° of crank angle.

• Too early timing of injection

• Higher peak pressure




• Exhaust gas temperature after cylinder

• Measured individually after each cylinder

• Each cylinder has two measuring points.• The average temperature of all exhaust temperature

sensors is approximately 100 °C lower than the exhaustgas temperature before the turbine.

• Maximum allowed difference between valves in onecylinder.

• Maximum allowed difference of one cylinders average fromthe average of the all cylinders , alarm.




• In normal operation the average temperature Cylinder

temperature deviation can be up to 30 - 40 °C.

• Engine is (depending of installation) provided with a safety

slow down arrangement if the temperature difference is too

big

• A 10 °C increase in ambient temperature will result

approximately 15 °C increase in exhaust gas temperature




• Exhaust gas temperature after turbocharger

• Indicates the kinetic energy of the exhaust gases that arerunning the turbine

• Indicates the condition of the turbo, i.e. scavenging of the

engine

• If a de-Nox catalysator is installed the temperature has to

exceed certain level to ensure the function of the

catalysator




Pressure difference over the cylinders:

• Measuring the pressure difference between charge airmanifold and exhaust gas manifold.

gives an indication of how well the scavenging works.

• Depends on the turbocharger, therefore values belowshould be considered as allusive

• The bigger the Dp is the better scavenging.

• Is normal value with 100% load varies depending ofinstallation once the value has been dropped down, it is an

indication that something is wrong with the engine-e.g. dirty nozzle ring & turbine




Dirty charge air cooler:

• Indicated by the increase of the pressure difference overthe cooler, remember that the cleaning of the cooler is

aggravated with the dirtiness of the cooler.




Consequences:

• Less fresh air to cylinders• Higher exhaust gas temperatures

• Improper combustion

• Low peak pressures• More deposits to nozzle ring

• Increased SFOC

• Increased SLOC• Higher fuel rack reading at the same load




Condense water in charge air:

• Condense water that is condensing in the cooler has to be

drained out

• Causes wear in the pistons, piston rings and cylinder heads

• Will cause inlet seat ring problems

• The amount of condensed water may be reduced byincreasing the charge

• Air temperature, but the maximum temp must not be

exceeded which is 55°

C• Increases thermal loading of the engine



Influence onoperating data Wärtsilä Vasa 32 n = 750 rpm

Output constant pe = 20 bar Charge air temp. constant

-10%

-20%

0

+10%

+20%

Firing pressure

Charge air pressure / mass f low

Fuel consumption

Exhaust temp. after cyl inder

Inlet air

temperature

-30° -20° -10° 0° 10° 20° 30° 40°

50°





Dirty nozzle ring:

– Indicated by;

– Slightly higher turbine speed

– Higher receiver temperature

– Decreased pressure difference over the cylinders




2. Possible consequences;

• Remainder pressure in the cylinders increase

• less fresh air to cylinders• worse scavenging

• delayed combustion

• more deposit accumulations

• higher exhaust gas temperatures

• increased thermal load

• increased risk of engine failure

• piston seizure• hot corrosion

• increased fuel consumption.




NOMINAL OUTPUT:

_____________________

NOMINAL SPEED:

_____________________

ENGINE DRIVEN PUMPS:

_____________________

FUEL:

_____________________

TURBO CHARGER:

_____________________

INJECTION PUMP:

_____________________




Low peak pressures-high exhaust gas temperatures:

• Obvious reason:

• DELAYED COMBUSTION• Dirty air cooler

• dirty nozzle ring(s)

• injection nozzles in bad condition

• worn injection pumps

• a long injection delay

• bad fuel

• high CCAI value poor ignition properties• high water content

• high exhaust gas temp




High exhaust gas temperatures:

• Obvious reason

• Injection valves in bad condition

• dirty nozzle ring

• dirty air cooler

• Low fuel viscosity

• worn injection pumps

• bad fuel

• burned valves or seats




High Fuel Rack Reading Compared to Load

• Worn injection pumps

• more internal leakage

• too low viscosity of the fuel

• more internal leakage

• low heat value of the fuel

• high water content

• dirty fuel filter

• too low fuel pressure

• big fuel leakage

evaluation of engine running data-new

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