This tall, cylindrical structure is an incinerator, likely a burn-off stack, used for safely disposing of certain materials by combustion. The heavy rust suggests it has been in operation for some time and handles substances that cause significant corrosion or has been exposed to the elements for many years. Given its location at a model airplane field, it's possible it was used to destroy old fuel or other related waste, although its size might suggest a broader industrial or municipal purpose in the past for the area around the field.