You are specifically targetting _blank when opening your window, and this is a special case that will always open in a new window or tab.
You need to change this to a unique name so if you open the URL again, if it has the same unique name as the previous window it will open in that and not a new window.
For more information on the target names and special cases, please take a look at the following page.
I hope this helps.
Hi Ryan Ge,
You had given as blank so it will open in 3 different tabs. Do u want to open in same window?