To burn any kind of heavier fuel like vegetable oil, turpentine, kerosene, diesel fuel, etc., requires vaporizing the fuel before it will ignite. In modern diesels, this is accomplished by injecting a thin stream of diesel fuel into air that is superheated in the combustion chamber by extreme compression. Although I have found two examples of model, injected diesel engines running on youtube, they are scarce and virtually no informaton is available for them
In earlier engines, a bulb or tube was superheated by an external flame, at least to get it started. Fuel was injected or drawn into the heated bulb or tube and vaporized during the intake stroke. On the compression stroke, air was forced into the bulb or past the tube and combined with the vaporized fuel to ignite the mixture. Once the engine was running, engine combustion would keep the bulb or tube hot and the external flame could be removed.
The short answer to your question is that I have been unable to find any plans for hot tube or hot bulb engines currently available, even though I have been looking for some months now. There are recent examples of casting kits for engines that run on hot tube ignition, but are not currently available. A hit and miss version of a hot tube engine requires a constant external flame since the combustion cycles are too far apart to keep the hot tube hot. There are a few working models of hot tube engines built by individuals that burn kerosene or turpentine, but there are no plans available for them. I have not seen any models that burn vegetable oil.
Looks like this is your chance to break new ground!
Chuck