DTU - Delhi Technological University

Sorry to say, but with 18000 rank in OBC Category, you will not be able to fetch a seat in DTU in any of the branch.
You need to score a rank under 5000 in OBC Category to secure the lowest preferred branch in DTU.

If the given ranks are your category rank. Then, I will have to say that it is enough to get you into DTU. DTU is one of the topmost college of the country and holds a good reservation for delhiites.
If you are resident of Delhi then you can go try for it, you might get some non-core branch there. Or maybe, you will have to go for another options.

Deciding a college depends on various factors like stream you wish to take, and the place where you belong to. NIT-Trichy is one of the top most colleges in our country and is certainly the better option out of the three if you look in terms of academics and placements point, but as said, if you belong to North India, it would be easier for you to blend with DTU rather than NIT Trichy. I would say NIT-Trichy, then DTU, then NSIT.

You can choose any one because both the options are good for B.Tech, and I don't think any IIT is not good.

Hello
As you have scored really good marks and have category also you have chances to get DTU but you also have chances for good nits and GFTIs so for you to decide I'm attaching a link, there you can check the opening and closing rank for the various colleges.
Http://josaa.nic.in/result2016/result/openingclosingrank.aspx
And congratulations.
All the best.

If you are a resident of Delhi then you hold a chance to get in DTU, else it seems quite impossible. There is 5% reservation under CW quota. You can try for other regional colleges to get the benefit of your quota.
Good luck!

Hello Himanshu,
DTU and NSIT are the top most engineering colleges of india. So, you can go with any of them. But, considering mechanical engineeing, DTU is bit more better than NSIT.

Hello Sagar,
It's difficult to say about admission since it depends on dynamic factors. However there are softwares that will predict college in which you can get admission. I am attaching a link that will predict your probable college.
https://www.resonance.ac.in/reso/news/JEE-Main-Branch-Predictor.aspx

Both the institute are better If you want an NITian tag, then go for NIT. Placement is good in both of them. Placement depends on individual's talent. Institute only provides platform and various number of companies visit in both campus.