Alcaraz makes semi-finals at Queen's as Rune and Korda also progress
The world No. 2 is playing on grass for the first time since his fourth-round Wimbledon exit last year as he acclimatises to the surface and the win was his best performance this week.
"The movement on grass, I try to move easy and move well," Alcaraz told the BBC after the match.
"I watched the best players in the world, trying to imitate them a bit. And I think I did well.
"I'm a guy who learns so fast... I'm playing at such a great level and feeling really, really comfortable playing on grass."
He will face big-serving American Sebastian Korda, who beat Briton Cameron Norrie 6-4 7-6 (7-1) to extend his Queen's debut.
Australia's seventh seed Alex de Minaur was the first player to book a place in the semi-finals, holding off Adrian Mannarino of France for a 6-4 4-6 6-4 victory.
De Minaur faces second-seeded Dane Holger Rune on Saturday after the 20-year-old beat Italy's Lorenzo Musetti 6-4 7-5.
Alcaraz, who studied Andy Murray and Roger Federer to improve his tennis on grass, had 10 winners in the first set to Dimitrov's four but trailed the former Queen's champion 3-0 in the second before finding his rhythm and roaring back to win.
"Obviously the two matches before (Friday) helped me a lot," Alcaraz said.
Korda, meanwhile, cruised comfortably past fifth seed Norrie in the tiebreak, with the Briton double-faulting to go down 4-0.
"I'm playing really well on grass and feeling really comfortable," said Korda. "I'm just enjoying myself.
"It's a great place. I've played some really good players this week. I'm definitely clicking."
Rune trailed Musetti 4-1 in the first set before receiving treatment on his right wrist during a medical timeout and the world No. 6 did not lose another game in the set.
Musetti also hit Rune hard with an overhead.
"This just gives me fire in the belly to beat him even more," Rune said. "I'm super happy to beat him. It feels good. I'm in the semis. He's not."
