This is almost certainly a Klockner-Humboldt-Deutz Dz-710 single-cylinder experimental diesel on test, presumably post-war based on the 1949 date, and therefore in the U.S. somewhere. A single-cylinder and a complete 16-cylinder were brought back to the US in or after 1945, it is said to Wright Field, but subsequently they disappear from history.
This and the other three associated photos would appear to possibly shed some light on their final fate - any other information (eg: where is the location in the photograph, who is the technician, etc) would be welcomed.