Admission to IIT Delhi is Not based on JEE Main it will be based on JEE Advance But You need to qualify JEE Main to be eligible to appear for JEE Advances, JEE Main is Just qualifying exam and shall not contain any weightage to the final rank calculation of JEE Advanced which is solely responsible for admission to IIT.

You can check Opening closing Rank of Pra]evious Year to know what rank You should get in Order to join IIT Delhi under various categories and various courses. Anyways if you are able to score more than 50% marks in JEE Advanced then there are quite good chances that You will be able to get admission to IIT Delhi in some course Kindly follow the link below to know the previous years closing ranks.

https://josaa.nic.in/webinfocms/public/view.aspx?page=46