The winners of yesterday's 15th annual National Capital Open bicycle races around the Ellipse were almost all previous winners who came roaring out of the past to beat a strong field of more than 400 amateur and professional racers.

Bruce Donaghy, a New Jersey amateur who won here in 1980 and again in 1981, when he set a national 50-kilometer record around the fast, flat oval, won again in a wild and windy finish that appeared to set an unofficial record of 1 hour 3 minutes 5 seconds, two minutes faster than his 1981 record. He collected $700 of the $20,000 in prize money.

Right behind him in the photo finish were Mark Whitehead and Canadian Steve Bauer. Whitehead recently set an unofficial national record for the 50-mile criterium. Bauer, the defending Open champion, was the top amateur finisher last Sunday in the three-day Tour of America race when he finished fifth. Chris Meerman of McLean was the top local rider yesterday, finishing sixth.

Canadian Karen Strong-Hearth returned to win her third Open title, also in a close finish of 27 U.S. and Canadian women riders. She received $475.

Pam Deem of California, one of the nation's top women sprinters, finished a wheel behind Strong-Hearth. Three women were injured in one of the numerous mass pile-ups that marred each of the day's five races.

In the race for junior riders, under 18, more than a dozen racers crashed in a huge flying tangle of bodies and bikes in front of the finish line crowd of more than 2,000.

The Open's reputation as one of the nation's fastest and bloodiest amateur races was confirmed by volunteer race physician Dr. Frederick Barrick of McLean. His preliminary report of this year's injuries: one broken leg, a broken hand, several head injuries sent to the hospital and too many cuts and abrasions to count.

The winning junior, among those left after the accident and a restart, was Matt Willis of Princeton. Bobby Livingston, last year's winner, finished second, and David Underhill of New Jersey, was third.

A veterans' race, for men over 35, was included in the Open several years ago when the Washington-Baltimore area began producing the nation's top over-the-hill bike racers.

Yesterday it was won by Baltimore "Bullet" Bobby Phillips. Second was national Veterans champion Jim Montgomery, a computer systems specialist from McLean, and third was the gray-beard national masters (45 and over) champion Jerry Nugent, a medical film maker for the U.S. Army from Bowie. All three ride with the National Capital Velo Club, which organizes the Open.