two ROR project with one application server , is it possible

I assume you are limited to one available port on a static address
that you want to use for multiple Rails applications.

You can accomplish this by configuring Apache so that it talks to the
correct mongrel instance based on the incoming request.

Example: http://xyz.com/app1 would go to mongrel instance on port xxx
and http://xyz.com/app2 would go to mongrel instance on port yyy.

A simpler way to do this is to use mod_rails. Configuring multiple
Rails app in subdomains is quite easy with mod_rails. http://www.modrails.com