There is a federal program for funding of small business research concepts. It is called the Small Business Innovation Research Program (SBIR). Each agency puts out a procurement document each year with desired topics of interest, i.e., army, navy, air force, nasa, and all the other agencies. Novel propulsion topics are always a topic of interest. Look up this program on the internet and get on the list for the procurement docs.
Write up your idea in a proposal format and submit it. You can submit the same proposal to many different agencies interested in new propulsion concepts. Your proposal will be reviewed by propulsion experts from every service. If successful, you could receive a Phase I grant to expand the work and you also would know of the merit of your idea. Phase II follow on efforts are 10x the phase 1 grants.
If unsuccessful, you can request copies of the evaluations to see where the experts disagreed with your idea.
This is a relatively easy way to get your idea in front of dozens of propulsion specialists. Better than hustling a dozen different aerospace companies.
Also a paper at a major scientific meeting like the American Institute of Aeronautics and Astronautics (AIAA) could generate some interest if you circulate around the meeting.