# Combustion



## Clydeman (Dec 13, 2010)

This weekend I spent on Combustion (which I do not think I ever saw in school). I must say that I am not impressed with how MERMs deals with this subject. It seems like much of the first half of the chapter deals with subject matter than is not that pertinent or helpful. I can see a concept question coming out of these areas though.

Anyway it seems the meat of the chapter is combustion reactions, stoichiometric air, flue gas analysis and heat of combustion. So after reading the chapter (quite thoroughly) I start in on the separate book of practice problems. Unfortunately I was not able to do many of them. The chapter does (in my opinion) a poor job of preparing for the practice problems. And for some reason there are a ton of practice problems on this chapter (19 of them).

I could really dig into all of the practice problems (which could take some time) but it would seem the wise decision would be to move on to subjects that are probably more pertinent (the rest of the thermo chapters and power cycles).

In all likelihood there might be 1 or 2 combustion questions or none right? So combustion is probably not time well spent right?

Any advice?


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## navyasw02 (Dec 13, 2010)

Anything is fair game so I dont want to lead you astray by telling you what may or may not be on the exam. That said, I dont remember too many problems in the practice exams on combustion. As for the real test, I'd say about half of the morning questions I could have done without cracking the MERM. Out of the other half, I knew the equation and looked at the book just to double check and make sure I didnt do something dumb. Nothing was complex enough that I needed more than one equation for the morning session. So if you're doing MD, I wouldn't sweat knowing every detail about the TF section, including combustion.


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## Relvinim (Dec 13, 2010)

Like Navyasw wrote...everything is fair game. But I think after you do all the sample exams and 6 minute solutions you will pick up on a pattern of what will be on the test. Of course...there is no guarantee there either. There were so many problems that I thought for sure would be on the test and they weren't.

The idea of reading the MERM again is giving me the shivers. I hope I passed!


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## chaocl (Dec 13, 2010)

Relvinim said:


> Like Navyasw wrote...everything is fair game. But I think after you do all the sample exams and 6 minute solutions you will pick up on a pattern of what will be on the test. Of course...there is no guarantee there either. There were so many problems that I thought for sure would be on the test and they weren't.
> The idea of reading the MERM again is giving me the shivers. I hope I passed!


I agree with you...Read MERM carefully and do practice problem on 6 min solution, Lidenburg sample, and Kaplan sample will help you to understand how the combusion questions will be on the exam.


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## Clydeman (Dec 13, 2010)

chaocl said:


> Relvinim said:
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> > Like Navyasw wrote...everything is fair game. But I think after you do all the sample exams and 6 minute solutions you will pick up on a pattern of what will be on the test. Of course...there is no guarantee there either. There were so many problems that I thought for sure would be on the test and they weren't.
> ...


This is exactly my plan.

The reason I brought this up was that this is the first chapter I have run across where reading the chapter did not enable me to be able to solve the practice problems.

I too cannot imagine having to read through MERMs again if I do not pass in April. I really hope I do not have to put the wife and kids through all this studying again.

I am trying to put in 25 hours a week (have been getting up at 4:30 to 5 every morning). I hope I can maintain this for the next 3 1/2 months. I am going to be very tired and burned out when this is all through.


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## navyasw02 (Dec 13, 2010)

Nathan Satter said:


> chaocl said:
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> > Relvinim said:
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I dont know what your background is, but I'd really suggest not studying until 2 months out at the earliest. I started at 2 months out and after the first month, I was at the point where I'd rather gouge my eyes out than do another practice problem. The last 3 weeks I dont think I did anything but read the MERM and flip through solutions because I just couldn't do anymore. I did every 6ms MD problem, every 6ms TF and HVAC breadth problem, both NCEES exams in full except for HVAC, the breadth lindeburg practice exam, and a schmorgasboard of other problems.


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## Clydeman (Dec 13, 2010)

navyasw02 said:


> Nathan Satter said:
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> > chaocl said:
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I hear you. I have been wondering how much I will recall of things I study now months from now. I realize I will need to go over much of what I am studying right now. I think though that the second time through I will know what to focus on and what not to.

Unfortunately I have been out of school for 14 years (ME design primarily, consumer products). I have likely forgetten a lot more than most of you. Most of my time the last few weeks has involved reading and understanding the concepts in MERMs. I have been doing some sample problems (1/3 of my time), but mainly I am reading (other 2/3rds). I plan to do a ton of practice problems toward the end.

Also I fear I am not a good test taker. In school I had to know my material well. If I am not confident going in, I will liklely not do well.


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## navyasw02 (Dec 13, 2010)

Nathan Satter said:


> navyasw02 said:
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> > Nathan Satter said:
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Dont let the practice problems discourage you. I'm finishing grad school now and I had a lot of trouble with the 6MS MD questions. Doing all the problems you can will make you over prepared for the exam. Had I known that, I wouldn't have spent more than about 2 weeks studying the morning session questions.


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## MadDawg (Dec 13, 2010)

Combustion was one of those topics where the practice problems really helped me understand the topics better. You're right--the MERM doesn't explain it well, but at least you'll have quite a few go-bys if you work the 6MS, Lindeburg, NCEES, etc.


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## FusionWhite (Dec 20, 2010)

My advice is to learn to use the combustion tables.

They are usually given in the format of: 1 mole of combusted A requires, X moles of O2, Y moles of air and gives Z moles of CO2.

The table gives all of these in multiple units (per pound, per mole, per SCF) and makes it really quick to figure up things like actual and excess air.


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## RobertR (Jan 13, 2011)

Keep in mind that the exam questions are meant to be answered in an average of 6 minutes, so always think of a table solution first.


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## jerrypalojr (Jan 18, 2011)

The only time I can remember a combustion problem showing up on the exam involved flue gas and it was a plug-and-chug exercise. Just like everybody else pointed, every topic is fair game and the exam might ask a word problem that pertains to combustion.

Good luck!


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