Is there a way to use your voice to open apps in Android?
Yes, there is. At least for some app names it should work fine. You should start a voice search with the "Google App" and press the microphone button in it to speak and say "open application". I've tested trying to open a couple programs: 


open gmail
open telegram
abrir caixa (Portuguese for open and a bank app...)
open just java


All of those worked and it is not limited to English. If you have a phone like a Samsung Galaxy, I think there is another app that lets you voice control, but I am not sure if it is worse/better than the Google App.

References: "Ok Google" voice search &amp; actions and some testing by myself on Android 5