China's Sun Yang gestures after competing in the men's 1500m freestyle heats at the 14th FINA World Championships in Shanghai July 30, 2011.  [Photo/Agencies]

SHANGHAI - China's Sun Yang loped into the final of the men's 1500 metres freestyle at the world championships on Saturday, powering his way to top the qualifying sheets with a time of 14 minutes, 48.13 seconds.

Sun, tipped to take over from retired Australian Grant Hackett as the world's dominant swimmer in the distance, was ruthlessly efficient in his heat, destroying Beijing Olympic champion Oussama Mellouli by almost a length of the pool.

Tunisian Mellouli finished in 15:13.56 and did not qualify for Sunday's final.

The tall 19-year-old Sun has already won the men's 800 freestyle in Shanghai and taken silver in the 400 freestyle behind South Korea's Park Tae-hwan. He added a bronze as a member of China's 4x200 freestyle relay team.

"The ... swim (on Saturday) was pretty good," Sun told reporters. "I will just be myself in the final.

"It would be great if I win but you never can tell in a competition, unexpected things can happen."

Double Quick

Jessica Hardy also produced a quick turnaround to qualify equal fastest for the women's 50 freestyle semi-finals, then fastest for the 50 breaststroke.

The 24-year-old American clocked 24.82 seconds with Sweden's Therese Alshammer in the second-last heat of the 50 freestyle before she was back in the pool less than 15 minutes later for the final heat of the 50 breastroke.

Hardy clocked 30.20 seconds to win that heat ahead of Russia's Yuliya Efimova and 100-200 breaststroke champion Rebecca Soni of the United States, who both clocked 30.72.

They compete in the semi-finals later on Saturday.

"I am really happy with that. Very excited," a buoyant Hardy said of her performance.

"This was just about making it top 16. You want to make sure you feel good and I did."

The United States quartet of Elizabeth Pelton, Soni, Christine Magnuson and Amanda Weir were comfortably the fastest qualifiers for the final of the women's 4x100 medley relay.

World champion and record holder Liam Tancock of Britain qualified 10th equal fastest for the semi-finals of the men's 50 backstroke.