Is CRL rank in JEE Mains considered for admission in DTU ..? if yes then what should be the percentile required for OBC-NCL Delhi category student for mathematics and computing engineering???

Yes, CRL rank of Jee Mains is considered for admission in DTU. Generally the closing rank for Mathematics and Computing engineering is in the range 97,000-99,000 for Delhi region candidates. That means you should aim for a percentile score above 90 to ensure you that rank.
This cutoff varies every year so try to give your best and hopefully score 95+ percentile, then you will be eligible for top NITs or IIITs as an obc candidate.

Good Luck !