Yes. Give them a brief intro of yourself and experience and interest in the project and ask based on that, if they think you should apply. If you are unsure of the level of experience or type required for the project then this is the best approach. Plus it might also give you an indication of the level of competition you may face, one person I spoke to told me the level of interest he had for the project.
I have just been offered a PhD at Nottingham for which I contacted the supervisor directly first informally so it does no harm.
Some people reply, some don’t, out of maybe 8 I emailed 5 replied.
Good luck :O)