Turbo heat exchanger undersized on Jenbacher engine... suggestions?

[USAeng]

We have a 335 KW Jenbacher Type 2 CHP that has a upgraded turbo but the intercooler (see attached picture) heat exchanger after the turbo was never upgraded... the engine intake air is often hot here in summer... therefore the engine must run in reduction for most of the day every day until the weather starts to break. We are making power from waste - so the city wants this engine to run 100% most all the time

Jenbacher does not make a larger intercooler for this engine. Our plant water is about 70-75F degrees so we cant really run a heat exchanger with that for the intake air. They tried putting in a larger heat exchanger on the roof to cool the intercooler after the turbo, but the intercooler can only transfer so much heat to the heat exchangers on the roof... it just is not large enough.

Any ideas? thought of a fogging system like they do for gas turbines but I dont think it would work here. People tell me I cant make a bigger intercooler for engine as Jenbacher will not warranty the engine and also it has to meet EPA requirements and they tell me all parts just be OEM... I am just going by what people tell me so far... have not been here but a little more than 2 months.

Thanks for any suggestions.

 

[Lou Scannon]

Sounds like the turbo wasn't much of an upgrade. What benefit is it supposed to provide? Is it an emissions-compliant upgrade and is it endorsed (or provided directly) by Jenbacher?
If your installation is subject to emission regulations you can't really change anything unless the engine OEM or another responsible entity is there to stand behind the changes, from an emissions compliance point of view.
Even when emissions aren't a factor, you have to know what you're doing when you make changes. Do you know what you're doing?

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

 

[USAeng]

Jenbacher switched the turbo to get the engine producing the full 335 KW of its design... they are not standing behind their design change... they will not admit that their turbo is too big for the intercooler to handle... they would have to design a larger intercooler, but this is a small engine for them that they have pretty much forgotten about from what I've been told and they are not interested in helping as it would require work on their part.

 

[USAeng]

It would be nice to have someone just fab a larger intercooler but Jenbacher wouldnt stand by the change like you said. So maybe there is another option?

 

[patprimmer]

I only see two options. You modify or hot rod it to get the performance you want along with all the implications to warranty and emissions, or you accept the OEM power it makes.

If it where me, I would hot rod it with a bigger inter cooler of something else. I never really ever saw any downside to bigger inter cooler to go along with more boost. I guess a colder charge might be a bit harder to ignite and when it does go bang it might do so with a bit more force and place a bit more strain on the drive train, but how else do you get the required power.

Regards
Pat
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[USAeng]

I assume you guys know its not a vehicle but a CHP (combined heat/power) generation unit. Its just an engine with a generator attached to it. Anyways I would like to have a third party design and build a new intercooler but if I understood what one of my coworkers told me - its something like the OEM wont accept the part and stand by the design and they need to sign off on it or the EPA needs to have them sign off or something.... I will have to look more into that part unless someone here knows how that works

 

[patprimmer]

You can't modify then have it tested for emissions?

I know it's not in a car, but an engine is an engine.

Regards
Pat
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[JackAction]

If I understand you correctly, your problem is not that you are not producing enough power, but it is that you don't get rid of enough waste (which fuels your generator)?

If that is the case, you could cool down the air before it enters the engine with some air conditioning unit, just enough to bring it to a «normal» room temperature. This way, you don't modify the engine in any way. It might not be efficient in power recovery (did not do the calculations), but it will let you use your generator 100%, helping you getting rid of the waste you want to burn.

 

[Lou Scannon]

YOur best bet is to find a competent industial engine installer in your area and have them use their expertise to alleviate your issues. You should also review the emissions certification to which your engine is subject, and make sure you and the installer understand the implications of any changes that are made.

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

 

[mattsooty]

Might it be possible to introduce atomized distilled water, precompressor?
This would have a very favourable effect on the charge temps with few downsides, compressor wheel erosion a possibility.
It could be fabricated so as to be easily removed, as & when required.

MS

 

[catserveng]

You can try one of two possible options, depending on the turbo compressor outlet temperature. Many industrial gas engines are now using two stage aftercoolers, first stage is jacket water cooled and strips some heat from the charge air, and then the second stage on a seperate circuit brings it down to rated charge air temperature. Other option is to fit an air cooled aftercooler, there are many suppliers of ATAAC cores and assemblies for retrofit.

Is the engine a low gas pressure arrangement, where the fuel is introduced at the turbo compressor inlet, or a high pressure arrangement? From the picture it looks like a low pressure system, but it also looks like a stock photo, not your installed unit.

Likely your air permit is controlled by your local air quality district, since for stationary gas (SI) engines most emissions regulations are applied at the local level, at least in the Western US where I work. Likely the best suggestion is to find a local industrial engine dealer who has knowledge of your local air quality regulations and available retrofit options. There is probably not a cheap solution, especially for a unit that small, but I think an ATAAC solution is probably your best option if sized correctly, also depends on your installation and access.

When you say "waste", are you talking about digester gas, landfill gas, or some form of producer gas, like from wood or coal seam? If you have a poor BTU value the turbo change might have been Jenbacher's best hope to get enough boost to make power, but depending on pressure versus temp rise out of the compressor, may be at a point where the compressor outlet temp is way more than any "standard" aftercooler design they may have will work. Frankly on the smaller engines they don't have much population in CHP applications I know of, at least in the US, most Jenbachers I get around are above 1 MW.

Depending on what kind of fuel you're feeding the engine, water injection could be a benefit or an real additional problem, depends on what else is in the fuel stream. For that size engine I can't imagine you're doing much in the way of extensive fuel treatment.

WHat is your target air inlet temperature? What is current compressor outlet temperature? What emissions level are you trying to attain? What is you fuel BTU? Where are you located? I may be able to suggest someone who can help in your area.

Regards, Mike L.

 

[Hoxton]

Looks like some basic application problems.

Industrial engines are rated in accordance with ISO3046, I will check if there is a USA equivalent. With this, the standard reference temperature is 25C (80F?). So if the combustion air inlet temperature (that is the air temperature into the air filter) rises above this, the engine management system may reduce the power limit.

There may be a project specific agreement to rate the engine at a higher inlet temperature. Check the contract documentation!

Must modern gas engine have two stage inter coolers; the first stage after the turbo is cooled by jacket water, the second by a remote radiator (dry air cooler). This sounds like the one that has Ben increased in size. The water temperature into the second stage intercooler can be 50C. Because of cost /size/noise this radiator can be rated for 30C air on. This may be the reason that it was up sized.

What fuel gas are you using -digester gas? What is the methane% and other major constituents? Is this the same as the system was designed for? Remember that the engine wil always try to generate the power as demanded (usually full power, so as the energy only comes from the methane, if the methane% is low then the throttle will open to allow more fuel to enter. This wil increase the mass flow into the turbo, as non combustible gas will also enter.

This may explain why the turbo was changed......

How old is the engine? Have the intercoolers been inspected / cleaned? Biogas can be very dirty and intercoolers can get blocked / corroded very quickly.

Finally, what is derating the engine? Looking at the display screen may help.