The Combustion Chamber At first glance, the combustion chamber may seem a fairly straightforward part of the jet engine. After all, its just a place where the fuel and air get burnt, right? In fact the combustion chamber, even without any moving parts, is a lot more complicated than first meets the eye. A jet engine burns considerable quantities of fuel and the combustion chamber has to achieve this in quite a small area. It is just not possible to pump large amounts of fuel into the combustion chamber and expect it to burn. Sir Frank Whittle found this to be his greatest problem when building the world's first jet engine. If coping with the large amounts of fuel was not enough, the combustion chamber somehow has to deal with the airflow from the compressor which enters the chamber at speeds of up to 500 feet per second. The ideal mixture ratio of air to fuel is 15:1 but the total air to fuel ratio in the combustion chamber can vary between 45:1 and 130:1. This is because up to 80% of the air entering the combustion chamber is used to cool the sides of the combustion chamber and to stabilise the flame. This flame stabilisation is important because without this, the flame would simply blow out.
			Reproduced with kind permission of Rolls-Royce plc
	Although there are several types of combustion chamber designs, they all have an inner and an outer section. The inner section or liner as it is know, will be perforated with many holes which allow cooling and stabilising air to enter the combustion chamber throughout its length. The outer section is not perforated and acts as a sealed vessel for the liner. The liner is usually concentric within the outer casing and the passage formed between the two is used to form an area of cool air to prevent the materials of the combustion chambers from melting in temperatures in the region of 2000 deg C. More about combustion chambers Back to "How they work" index Back to "Home"