Hottændrør

Hottændrør, a Danish term, translates to "hot ignition plug" or "hot spark plug" in English. It refers to a component used in certain types of internal combustion engines, particularly older or simpler designs, to initiate combustion. Unlike a typical spark plug which relies on an electrical spark to ignite the fuel-air mixture, a hottændrør utilizes residual heat within the combustion chamber.

The principle behind a hottændrør is that the plug itself becomes extremely hot during the engine's operation, often through a process of compression heating or by absorbing heat from the exhaust gases. When the fuel-air mixture is introduced into the cylinder and compressed, the heat from the hottændrør is sufficient to cause auto-ignition. This method is generally less precise than spark ignition and can lead to less efficient combustion and higher emissions.

Hottændrør were more common in the early development of internal combustion engines and in specific applications where simplicity and robustness were prioritized over precise ignition control. They are often found in applications such as some types of stationary engines, older tractor engines, or certain diesel engine designs that utilize glow plugs, which function on a similar principle of heating to aid ignition. The use of hottændrør has largely been superseded by more advanced ignition systems in modern vehicles due to their limitations in performance and environmental impact.