04-08-2018 12:07 AM
The Gerp on this engine is to find the correct engine timing.
Maybe you need check all spark plug and gap, calibrate all inlet and exhaust valve.
Find the startup document, emission analyser, TMI document to see the emission from factory, and start adjust the engine step by step from no load to 100&% load is the best thing.
04-02-2018 09:20 PM
All NA G3304 and G3306 should have valve stem seals, regardless of load. You have to be careful on the G3306 TA, though. If you put inlet valve stem seals and run it consistently at high load, you will probably have some valves stick from lack of lubrication at the high load. I would say on a TA you probably would be okay with inlet valve stem seals up to maybe 70% load, maybe a bit more. I don't have sufficient experience to know exactly where the break point is. But if you are going to keep the G3306 TA below 60% load, you should probably have inlet valve stems seals. Anytime you have the load light enough to see the inlet manifold pressure near atmosphere absolute (or nearly zero gauge, getting close to a vacuum or negative pressure) then the valve stem seals help a TA to control the oil into the cylinder.
04-02-2018 09:01 PM
I can't thank you enough for your advices. It really helpful.
I checked right away on our unit and parts manual after read your post yesterday. And I found that intake valves of G3306TA has no valve stem seal on it. I compared with ex-used cylinder head of NA model and found the intake valve stem seal like this.
Next, I will install this seal on the Engine TA type which operates at light load.
04-01-2018 10:14 PM
It sounds like you arrived at a compromised load percentage after some trial and error. And that is what I would use a lot. For instance, if you had the ignition timing set at the standard 30 deg BTC and applied load, if the load was too much for the fuel btu and you had detonation, you could retard the timing a few degrees at a time and see where the detonation stopped for the existing load. This result would be an optimum for best fuel economy, coolest exhaust temperature, and least tendency to detonate. That is how I would approach finding the optimum timing. The air fuel ratio comes into play here and I would have a goal of between 2-2.5% O2 in the exhaust. This would be a bit lean from stoich and would help reduce nitration of the engine oil.
This would be my approach to running this fuel. Again, it would be almost imperative for the G3306 to have low compression pistons for the best results. The one thing that I would do is to be sure that you have valve stem seals on the inlet valves. This will minimize the oil drawn into the inlet path into the cylinders and help prevent ash deposit buildup. This buildup could lead to preignition which is not lessened by retarding ignition timing. You just have to clean out the deposits and clean up the cylinders to make that go away. Valve stem seals are a must on NA engines and light loads like you are working with. If you have deposit buildup, I would think that you could run a nil ash (0%) oil and not get into any trouble with lubrication issues in your situation.
The one thing that is important is to keep the lubricating oil hot (up near 200+F). Keeping the engine oil temperature up will be very beneficial. There are some tricks to do this if you find keeping the engine oil temp up. If you have problems keeping the oil temp up, you will need to install an Amot temperature valve off the engine in the cooling system to operate as an inlet controlled temperature control device. This will keep both the engine coolant and the engine oil temp up. If you install an Amot valve ahead of the water pump inlet, you will also have to install a shunt line to the radiator top tank or expansion tank to be sure that the water pump does not cavitate during operation.
I hope this helps you.
04-01-2018 09:09 PM
Dear AI Hunt,
Thank you again for analysis. Highly appreciated...
Your analysis result is similar with mine.
This gas fuel will be supplied for Gas Engine Caterpillar G3306TA with Serial Number G6X02084 to drive rotary screw compressor FRICK TDSH233XL. The engine will be operated at light load at about 40-60% of its maximum rating.
We had experiences with bad fuel like this. At full load, the detonation indeed occured. But it turned out run normally at light load. Is there anything we have to do for precaution if we use low MN fuel like this for light load operation?
04-01-2018 07:43 PM
Here is the current GERP MN calculation for your fuel:
for given gas properties
C1 = 68.653%
C2 = 8.785%
C3 = 5.668%
iC4 = 1.113%
nC4 = 1.727%
iC5 = 0.754%
nC5 = 0.608%
C6+ = 5.106%
CO2 = 7.525%
N2 = 0.061%
Methane Number 0.0
WOBBE INDEX 1322
THC FREE INERT RATIO 12.18
TOTAL % INERTS (N2, CO2, HE) 7.586 %
RPC (%) (TO 905 BTU/SCF FUEL ) 100%
COMPRESSIBILITY FACTOR 0.994
STOICH A/F RATIO (VOL/VOL) 13.07
STOICH A/F RATIO (MASS/MASS) 14.27
SPECIFIC GRAVITY (RELATIVE TO AIR) 0.916
FUEL SPECIFIC HEAT RATIO (K) 1.269
As you can see, the current MN software calculated a MN of 0.0, The reason for the MN of 0.0 is that the fuel heat content is just too hot (high btu) for controlled combustion. In simple terms, this is really not a usable fuel in a gas engine. The fuel is very hot (high btu) and it will be very susceptive to detonation, maybe even at light loads. The engine certainly will not be able to achieve rated horsepower without experiencing detonation. The inerts are over 5%, which will elevate the exhaust temperature as the combustion will continue past the open exhaust valve on the exhaust stroke.
To make this a usabe fuel, you would have to remove at least these items from the fuel:
iC4 = 1.113%
nC4 = 1.727%
iC5 = 0.754%
nC5 = 0.608%
C6+ = 5.106%
If you remove these, then we could recalculate the MN and have a better feel for how this new modified fuel would perform. My experience without doing any work says that it probable would work; the fuel would still be pretty hot. If you also remove the C3 then I know that you could use the fuel with little problems. We could again verify that with a new MN calculation of the new fuel.
Will an engine run on this fuel? Probably the engine will run and maybe carry some load but much less than rated. The ignition timing on a 3306 will need to be retarded to 1 deg BTC to minimize detonation. The engine also must be a low compression ratio to run this fuel and do much work at all.
I hope this has helped answer your question. If you have further questions, please don't hesitate to ask.
04-01-2018 07:04 PM
Thank you very much for your advice.
If you have the latest version of GERP, would you please help me calculate methane number for the sample I've given. I doubt the accuracy of MN calculation using my GERP since I don't update the software yet.
04-01-2018 10:00 AM
The current and most accurate Methane Number calculation is the one in the current GERP (6.0). Methane 4.04 is out of date. The current GERP calculation will give a more realistic indication of how the fuel will perform in the combustion process. Cat does not support any Methane calculation except the current software contained in GERP.