It is likely that the essential oils will be destroyed by chlorine, resulting (as long as there is an excess of chlorine) in the formation of chloramines, haloforms, aldehydes, etc. Some of these compounds (e.g. nitrogen trichloride) will have a high vapour pressure which will increase the "chlorine smell" you attribute to the hypochlorous acid solution. It is possible that the smell of essential oils will predominate, but this will not happen without a decrease in the amount of free chlorine.
These things are fairly well documented for swimming pools. Examples below:
Thank you Michel Héry Sir for your reply. Indeed, the amount of free chlorine will decrease, we just do not want it to dramatically decrease (few hunderds ppm for example nothing more is OK). We need to add just a small amount of essential oil to either neutralize chlorine odor or have essential oil's odor.
"It is possible that the smell of essential oils will predominate, but this will not happen without a decrease in the amount of free chlorine" : could you ,Sir, give me some possible natural essential oils candidates that we could use in small amount?
There is a Japanese patent on this, they used eucalyptus and peppermint oil it seems. https://patents.google.com/patent/WO2018174136A1/en I just tried it and in small amounts dissolved in alcohol, it still has potent free chlorine. However cross the line and add too much and the HOCl is ruined. As others have mentioned, organochlorine chemicals are potentially unsafe, doesn't seem like a great idea. Hypochlorous odor will dissipate quickly, if it is not actually hypochlorite... check the pH.
You will certainly need a solvent or emulsifier for any essential oil to dissolve in water. Salt can potentially replace alcohol if you add enough, according to readings on making essential oil aroma sprays. The answer of which oils to use is already in the Japanese patent.
However, properly acidified hypochlorous smells clean and fresh (more like swimming pool than bleach), and evaporates quickly. Why bother covering it up with chlorinated terpenes which will probably smell weird (not like pure oils) and have a questionable safety profile?
Obviously it also adds complexity and possible problems if one adds additional variables to an equation. But at least there is a commercially available solution using HOCl & Eucalyptus oil, so it might be interesting to look that way for a possible answer.
A method for preparing a stabilized antimicrobial hypochlorous acid solution by diluting an aged stock solution to provide a hypochlorous acid solution at a concentration of about 50 to about 7000 ppm at a pH range of about 2.8 to about 4.0. The antimicrobial hypochlorous acid solution maintains at least 75 percent of the available chlorine present...