Diesel engine can not give more than half load 10

[ViCH]

Hi everyone. I am electrical technician, and I have problem with Emergency Diesel Generators at site. Full Power Capacity is 2.7MW, but we get speed unstable starting from 1.3 MW, if we want to give more power then engine looks like can not accelerate and frequency start to drop until under-frequency trip. We already check all fuel injection pumps, fuel pressures condition of valves, fuel filters.. Check electronic controls and all auxiliaries, but did not find any major problems.
By trending I found fuel demand is adequately changes with load requested. But I also mentioned that manifold air pressure is maintain 14.2 PSI before start, and 14 PSI +-0.3 fluctuating during and after start. Is it OK? Could it be problem with turbocharger, or wastegate control?
Engine: GE 16V228.
Turbocharger: 7S1716 compressor end. E-40811A

Viktor
Electrical Technician II

 

[malbeare]

have you checked the air cleaner ?


A tidy mind not intelligent as it ignors the random opportunities of total chaos. Thats my excuse anyway
Malbeare

http://www.sixstroke.com

 

[ViCH]

U mean air filter? Yes, we have DP gauge which shows good reading, and DP safety switch, which is also healthy. Filters was replaced approximately 1000 run hours ago.

Viktor
Electrical Technician II

 

[Compositepro]

Clearly, without turbo boosting pressure, the engine cannot produce full power.

 

[ViCH]

Also think so. But as I am not mechanical, I need to know, how turbocharger maintain air pressure in intake air manifold? What values should be? Any experiences? I have two theory:
1) Air pressure not raising - problem.
2) Air pressure maintain even with high vacuum on exhaust - no problem.

Due to no experience, I am in doubt...

Viktor
Electrical Technician II

 

[dgallup]

It looks like your manifold air pressure is absolute (not relative to atmospheric) as it's ~ atmospheric when the the engine is stopped. The turbo should be building boost as the load comes up, probably in the 30 to 45 PSI range. Most diesels don't have a wastegate but it sounds like yours does. It's possible the wastegate is stuck open, letting most of the exhaust gases to bypass the turbine. Without the exhaust going through the turbine, the compressor is unable to create the boost you need to make full power.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[ViCH]

Thanks for reference bro! 30-45 PSI is your own experience? How big engine it was?
Regarding waste gate - very probably, thanks for idea. What about turbocharger itself? Could it simply stack? Or if it stack, I can not get any load at all?

Viktor
Electrical Technician II

 

[SwinnyGG]

The turbocharger being seized is highly unlikely- if there was a lubrication failure or some other issue, turbos will typically rapidly destroy themselves and send parts downstream, destroying more things, before they will seize.

 

[ViCH]

Most diesels don't have a wastegate but it sounds like yours does.

Well.. Looks like You are right, this engine also do not have waste gate. I thought that light gray solenoid upstair is a valve for waste gate, but it is not. This valve is just for vacuum ventilation after crankcase coalescer.

SwinnyGG, then why intake manifold pressure not raising? Any ideas?

Viktor
Electrical Technician II

 

[3DDave]

Still seems like a stuck turbocharger. Perhaps the last time it was shut down there was a lubrication failure and the bearings are damaged. That would put a lot of backpressure upstream in the exhaust.
Is there no RPM indicator for the turbocharger?

 

[ViCH]

no, no any... Only speed sensors for main wheel and crankshaft..
I did not notice any backpressure on exhaust, at least still can see smoke from muffler.
Looks like we have to dismantle turbocharger to check it. What if we try to disconnect income pipe to turbo compressor? Should compressor vanes rotate freely by hand if bearings is normal?

Viktor
Electrical Technician II

 

[catserveng]

For the turbo, yes, you should be able to move the shaft/wheel assembly easily by hand. You should also check radial and axial endplay if you suspect the turbo is a problem, the procedure should be in your service manual.

Can you verify the manifold pressure with another gauge? You may have an air manifold pressure sensor fault and the ECM may have a limiter map to prevent overfueling if the manifold pressure is not high enough. On some of these engines the air pressure fuel limit map was in the ECM, on others it was in the Woodward governor.

Also, where in the intake air system is the air manifold pressure sensor, before or after the aftercooler (intercooler in some engines)?

A medium speed engine that size and rating will likely see the inlet manifold pressure drop to a vacuum at very low speed and load, how much depends on the restriction of the aftercooler core, as speed/load comes up the turbo will start to develop boost pressure and the manifold pressure will increase.

If this engine has been lightly loaded a lot, you may have a plugged aftercooler core. If you're seeing boost pressure (air pressure out of the turbo compressor going into the aftercooler) but manifold pressure is not increasing, you'll need to inspect the air side of the aftercooler core.

I'd suggest you get two good pressure gauges, install one on the outlet of the turbo compressor before the aftercooler core, on that engine a range of 0-60 PSIG should be ok. On the air inlet manifold side you'll need either a vacuum/pressure gauge or an absolute pressure gauge to get an accurate reading, on the pressure side should go to about 60 PSIG.

On the aftercooler core you should see a pressure drop at load speed/load of less than 1 PSIG, at full load max pressure drop on a core that size is about 4 PSIG.

Hope that helps, MikeL.

 

[TugboatEng]

4-stroke diesel engines typically have intake manifold pressure based rack limits.

Is this an electronic governor or mechanical?

If electronic I would suspect a failed turbocharger or intake air pressure sensor.

If mechanical inspect the sensing tube and diaphragm in the governor.

 

[ViCH]

Thanks guys, for your comments.
Engine is 1000 rpm rated, governor Woodwart 723plus.
And yes, this engine usually runs on low load (0-40%).
Manifold intake pressure sensor located on the end of left manifold, after intercooler. On right side manifold same hole is plugged, i plan to install 4bar gauge there.
Regarding gauge between compressor and intercooler, i have to check, is it any point(hole) for that.

Viktor
Electrical Technician II

 

[ViCH]

Well, I have some updates.

1) We achieve to compressor vanes of turbocharger and found it clean and free rotating. No abnormalities.
2) Double check air inlet filters - condition clean.
3) Install pressure gauge (55 PSI) to inlet manifold. Standby reading ZERO.
4) Dismantle pressure sensor from manifold air inlet, and found it is giving 14.5 PSI, like it was calibrated in vacuum. Done blows inside sensor - governor feels changes. So sensor not stack. Install sensor back.

One interesting thing I also found, when I disconnected sensor for Manifold inlet pressure, governor controller shows false signal of MAP, and..... false signal of Waste Gate... Once sensor install back, and reset alarms, both of them gone. I could not find any waste gate locally. If it is absent, why we need it in logic?
Another question, should I re-calibrate MAnifold sensor pressure, to make it show real pressure, or it is normal practice, to show atmospheric pressure (~1 bar) as real zero PSI?

Viktor
Electrical Technician II

 

[BrianPetersen]

Disclaimer: I don't know stationary engines. BUT ... In the automotive world, manifold pressure sensors (MAP) are "absolute" pressure sensors. Key on but engine off, they should read whatever the local barometric pressure is.

By "Standby reading zero" ... What do you mean by "standby"? Engine off, or engine idling, or running at rated speed but no load, or under load?

It is totally normal for turbochargers to not generate much, if any, boost pressure when the engine is not running under load! They're driven by exhaust pressure, and if the engine is not running under load, there's not much exhaust pressure, so therefore not boost pressure. The turbocharger will be spinning (at a relatively low speed), but not really doing anything.

Try to load the engine a bit, and see what your intake manifold pressure gauge does when you do that.

 

[ViCH]

Standby - I mean engine stop condition. On running without load MAP readings drop a bit (~13.9). Gauge not tested yet, no chance for test run until Wednesday.

I still can not find any waste gate, bypass or throttle valve in air intake system.. Governor do not have any intakes of that. Does it mean all this device absent, or it could be mechanical without any feedback? If absent, then how engine control speed, only by fuel injection? If mechanical, then where I can find it, how it looks like? Refer to photos on topic please.

Viktor
Electrical Technician II

 

[BrianPetersen]

That engine's speed and torque are established through fuel delivery control only. Since stationary engines are normally designed to run under load at a fixed speed, there is no regulation of boost pressure. The turbocharger is free-spinning and you get whatever boost pressure it feels like delivering. The smart people who designed it originally, carefully sized the turbine and compressor so that when the engine is running at rated power, the turbocharger operates at rated speed (and boost pressure). At part load there's less exhaust pressure so the turbo spins slower so it makes less boost naturally. No wastegate control is necessary if the original designers got the design right (provided, of course, something hasn't gone wrong).

Since turbochargers take a finite amount of time to get up to speed, the fuel delivery controls have an upper limit based on whatever the intake manifold pressure is, to avoid producing a big cloud of smoke if someone asks for a step-increase in engine torque/power output without waiting for the turbocharger to spin up and make the needed boost pressure.

HOW it does that, is outside of my knowledge. In automotive applications, the old-school diesel engines had a mechanical governor inside the injection pump. The new stuff uses electronically-actuated injectors and everything is in the ECU calibration.

 

[catserveng]

Yes, speed and load are only directly controlled by fuel rate. Certain applications that needed fast transient response had a wastegate option, you don't appear to have a wastegate installed but the 723 firmware could have the programming for it.

This worked before and made rated load, right?

Based on you pictures the MAP sensor is mounted at the rear of the left bank inlet manifold. Based on the info you provided it is an absolute pressure sensor, so if your site is close to sea level that the engine stopped reading you are seeing is correct. The fact it drops slightly into a vacuum with the engine running at no load is also a valid reaction by the absolute pressure MAP sensor. As you add load the pressure should go up, is it?

Based on your pictures looks like a port is available on the right bank inlet manifold to connect a gauge. install a mechanical gauge (vacuum/pressure) there, compare its reading to the MAP sensor readings.

You are able to connect and read data from the Woodward 723, right? You should be able to see parameters for the fuel limiters and see if the MAP sensor is affecting the fuel demand output to the ECM. I'm assuming this is the same unit you did another post on before, right?

MikeL.

 

[ViCH]

Exactly, same. I did not find any problem on governor and EFI site, and started looking for problem in mechanical site.
Gauge I already installed this night, 4 bar rated.
Problem is, that i can not simply test this engine, due to we are production plant. Every wednesday we have no load test. And we do not have option to do load test, except of power failure situation. So I have to be ready, when it happens
I am self learner in all this controller and metering devices, now its time to learn more about mechanical site,
I hope one day engine will surrender...
Regarding running on rated load before - no, we never got this engine run on more than 2MW. But I remember time, when it was stable on 1.6-1.8MW. Now its not stable even on 1.2MW.
Yes, I have laptop with Woodward software. Governor have inputs of MAP, MAT, water and lube oil temperatures and pressures, camshaft position, speed sensors. Output only one - fuel demand to EFI board. During run without load fuel demand is about 45%, and load calculated shows about 1%.
Regarding wastegate- if this engine does not have it, could active alarm and warnings of wastegate make problem to stability? Can I disable it, or it still can be useful in soft logic?

Viktor
Electrical Technician II