Hi Aakash,

With your JEE Main's rank, you won't get any decent college. Below is the list of colleges in Chennai where you might get Mechanical or Computer Science through your TNEA rank:

• St. Joseph's College of Engineering 
• Loyola- ICAM College of Engineering and Technology 
•  SRM Eswari College of Engineering 
• Meenakshi Sundararajan Engineering College
• Chennai Institute of Technology
• College of Engineering Guindy
• Panimalar Engineering College
• Sri Ram Engineering College

All the best