<P> In the true diesel engine , only air is initially introduced into the combustion chamber . The air is then compressed with a compression ratio typically between 15 : 1 and 23 : 1 . This high compression causes the temperature of the air to rise . At about the top of the compression stroke , fuel is injected directly into the compressed air in the combustion chamber . This may be into a ( typically toroidal ) void in the top of the piston or a pre-chamber depending upon the design of the engine . The fuel injector ensures that the fuel is broken down into small droplets , and that the fuel is distributed evenly . The heat of the compressed air vaporizes fuel from the surface of the droplets . The vapour is then ignited by the heat from the compressed air in the combustion chamber , the droplets continue to vaporise from their surfaces and burn , getting smaller , until all the fuel in the droplets has been burnt . Combustion occurs at a substantially constant pressure during the initial part of the power stroke . The start of vaporisation causes a delay before ignition and the characteristic diesel knocking sound as the vapour reaches ignition temperature and causes an abrupt increase in pressure above the piston ( not shown on the P-V indicator diagram ) . When combustion is complete the combustion gases expand as the piston descends further ; the high pressure in the cylinder drives the piston downward , supplying power to the crankshaft . </P>
<P> In the true diesel engine , only air is initially introduced into the combustion chamber . The air is then compressed with a compression ratio typically between 15 : 1 and 23 : 1 . This high compression causes the temperature of the air to rise . At about the top of the compression stroke , fuel is injected directly into the compressed air in the combustion chamber . This may be into a ( typically toroidal ) void in the top of the piston or a pre-chamber depending upon the design of the engine . The fuel injector ensures that the fuel is broken down into small droplets , and that the fuel is distributed evenly . The heat of the compressed air vaporizes fuel from the surface of the droplets . The vapour is then ignited by the heat from the compressed air in the combustion chamber , the droplets continue to vaporise from their surfaces and burn , getting smaller , until all the fuel in the droplets has been burnt . Combustion occurs at a substantially constant pressure during the initial part of the power stroke . The start of vaporisation causes a delay before ignition and the characteristic diesel knocking sound as the vapour reaches ignition temperature and causes an abrupt increase in pressure above the piston ( not shown on the P-V indicator diagram ) . When combustion is complete the combustion gases expand as the piston descends further ; the high pressure in the cylinder drives the piston downward , supplying power to the crankshaft . </P>
how much compression does a diesel engine have
how much compression does a diesel engine have
between 15 : 1 and 23 : 1
between 15 : 1 and 23 : 1