When running mvn install on a local multi module project it builds and install the projects artifacts into the local repo. mvn clean seems to clean
You can purge artifacts from your local repository, but why do you like to do this? Apart from that you can do that via maven-dependency-plugin:
This will purge all project- and dependency artifacts
mvn dependency:purge-local-repository -DreResolve=false
This can be influenced by supplemental command line arguments (see the documentation) for further details.