Hello Gaurav sharma,
Can try to use the follwing mentioned class with the method insted of WS_DOWNLOAD.
DATA v_filename TYPE STRING.
DATA v_filetype TYPE C LENGTH 10.
v_filename = filename.
v_filetype = 'ASC'.
CALL METHOD
CL_GUI_FRONTEND_SERVICES=>GUI_DOWNLOAD
EXPORTING
FILENAME = v_filena
FILETYPE = v_filety
CHANGING
data_tab = int_tab[
EXCEPTIONS
FILE_NOT_FOUND = 1
FILE_WRITE_ERROR = 2
FILESIZE_NOT_ALLOWED = 3
INVALID_TYPE = 5
NO_BATCH = 6
UNKNOWN_ERROR = 7
OTHERS = 8.