J.A.C. Kentfield designed pulsejets without valves. He was a researcher of this type of engines.

-He used the so-called "recuperators" of forward flame deflection, to return them in the direction of travel.

“Kentfield's concept”

“Two ideas on recuperators"

-He made practical engine, such as the one in the below photograph.

-It has four tubes in the front, with 180° turns.

“Practical realization of a Kentfield”