1 Scania Fuel System Scania Training September 2011

Combustion Theory Background Scania Training September 2011

Combustion Theory What is needed to start a combustion? Air = Oxygen Fuel = Gasoline Diesel Heat = Compression+ Ignition Scania Training September 2011

Combustion Theory Air consist of: 21 % Oxygen (O) 79 % Nitrogen (N) Scania Training September 2011

Combustion Theory Fuel (petrol and diesel) consists of: - Hydrocarbons (HC) Carbon (C) Hydrogen (H) Scania Training September 2011

Combustion Theory When gasoline burns optimally in the air a chemist writes the whole thing like this: The expression can be used to determine the relationship that should exist between air and fuel for optimized combustion. Scania Training September 2011

Combustion Theory Since many efforts have been made to find out how much weight molecules have, so you can set up the relationship between fuel and air mass for complete combustion. stoichiometric [,stɔikiə‘metrik] adj. 化学计量的；化学计算的 theoretical [θɪə'retɪk(ə)l] adj. 理论的；理论上的；假设的；推理的 Stoichiometric or Theoretical Combustion 14,6 kg air to 1 kg fuel. Scania Training September 2011

Combustion Theory Stoichiometric or Theoretical Combustion is the ideal combustion process where fuel is burned completely, and this means that Lambda has the value 1. Lamba higher than 1 is lean mixture. For example 1,05 Lambda lower than 1 is rich mixture. For example 0,95 stoichiometric [,stɔikiə‘metrik] adj. 化学计量的；化学计算的 theoretical [θɪə'retɪk(ə)l] adj. 理论的；理论上的；假设的；推理的 Scania Training September 2011

Combustion Theory It can be difficult to get an idea of ​​how much the 14.6 kg of air is so if we make it into a volume ratio so it is easier to get a reasonable idea of ​​how the relationship is. Mass ratio: 14,6 kg air to 1 kg fuel Volume ratio (approximately): 10,000 liters of air to 1 liter of fuel Scania Training September 2011

Dieselengine What is needed to create an engine? A. A closed tube. The cylinder. B. A movable piston. C. A fuel / air mixture which can be ignited. Scania Training September 2011

Dieselengine A connecting rod and a crankshaft, to get the piston´s forward and reciprocating motion converted into a rotary motion. Scania Training September 2011

Otto engine/Diesel engine Fuel = Gasolin Heat = Compression + Spark (Ignition) Air = Oxygen Nicolaus Otto 1877 Air and fuel are mixed and fed into the cylinder where it is compressed. A spark from the spark plug ignites the fuel / air mixture at the end of the compression. Scania Training September 2011

Otto engine/Diesel engine Rudolf Diesel 1893 The compression raises the temperature over the fuel's ignition temperature and the fuel is injected into the cylinder under high pressure. Air = Oxygen Heat = Compression Fuel = Diesel Scania Training September 2011

Diesel engine Four-stroke principle for a diesel engine. Intake 4-stroke diesel engine principle: (2 revolutions) The intake stroke. The piston moves down, air is sucked into (or pressed if the engine is equipped with turbo) in the cylinder through the open intake valves. The compression stroke. The piston moves upwards into the cylinder, both valves are closed, the air temperature rises due to the increase in pressure. The expansion stroke. Shortly before TDC, fuel is injected into the cylinder and ignited by the high air temperature. This increases the pressure in the cylinder and the piston is pushed down with great force (about 16-18 tons). The exhaust stroke. The piston moves upward and pushes out the exhaust gases through the open exhaust valve. Intake Compression Expansion Exhaust Scania Training September 2011

Diesel engine Turbo charger (exhaustgas-driven turbocharger) Turbo Chargers The turbocharger´s mission is to increase the amount of air (about 6x more than non-turbo) that goes into the cylinders. The combustion chamber´s design combined with the amount of air and the injected fuel into the cylinder provides a high power. The turbocharger consists of the turbine and the compressor. The turbine is driven by the exhaust gases from the engine. The compressor compresses the inlet air that goes into the engine. Higher power output from the engine produces more exhaust. More exhaust cause the turbine wheel and compressor to higher speed. In this way the quantity of air to the engine needs no special regulating devices. Turbo pressure between 1.7 -2.3 bar, industrial engines up to 2.7 bar. Scania Training September 2011

Diesel engine Intercooler Intercooler. The compressed air after the turbo compressor is fed through a tube to the intercooler which is placed in front of the Radiator. The air is cooled by the wind and the fan and then passes the Radiator. After cooling the intake air is led into the intake manifold which distributes the air to the cylinders. The colder the air is the more oxygen atoms is contained in the same volume. NOTE! There is also a water-cooled version (IP) Scania Training September 2011

Diesel engine Turbo Compound When exhaust gas leaves the engine's combustion chamber, they have a temperature of approximately 700 degrees C. When they passed the turbochargers turbine's temperature has dropped to about 600 degrees C. The difference of 100 degrees C means that some of the heat energy used to force around the turbine in the turbocharger. The remaining amount of heat, 600 degrees C, goes out through the exhaust pipe. Scania Training September 2011

Injection Injectionpump Unit injectors PDE -97 HPI -00 XPI -06 The right amount of fuel at the right time Injection Pump Unit injectors PDE -97 HPI -00 XPI -06 Scania Training September 2011

Injection What are we going to look at today? Scania Training September 2011

0,002380952 second Injection Today we'll talk about ... Two thousandth of a second Scania Training September 2011

Injection A diesel engine speed 1400 r / min It is converted 23.3333 r / second Scania Training September 2011

Injection One revolution takes 0.043 second 1 r = 0,043 second Scania Training September 2011

Injection What we are interested in is the injection. Injection takes place during 20% of one rotation. 20% of one rotation is 1 / 18 of 0.043 second. Injection takes place only once on two revolutions. Scania Training September 2011

Otto engine / Diesel engine Nicolaus Otto 1877 Rudolf Diesel 1893 Otto Diesel Air and fuel are mixed The fuel is ignited by a spark plug Compression ratio: 8:1 - 12:1 P-max 60 bar Air is compressed to high temperature The fuel is injected and ignites spontaneously Compression ratio: 17:1 - 28:1 P-max 180 bar Fuel with high octane number Fuel with high cetane number + Low noise level + Low emission level λ-1 and three-way catalytic converters - Low efficiency (approx. 33%) + High efficiency - High noise levels - Large amount of NOx and particles spontaneously [spɔn‘teiniəsli] adv. 自发地；自然地；不由自主地 cetane [‘siːteɪn] n. [有化] 十六烷，鲸蜡烷 octane ['ɒkteɪn] n. 辛烷 Scania Training September 2011

Otto engine / Diesel engine Stoichiometric Otto Engine (λ = 1) + Low-emission, λ-1 + three-way catalytic converters - Low efficiency - High exhaust temperature (about 900o C) Lean Otto engine (lean burn) (λ > 1) + High efficiency (35 - 37%) - Three-way catalytic converters is not useful Chance of misfiring near the limit of lean mixture stoichiometric [,stɔikiə'metrik] adj. 化学计量的；化学计算的 Scania Training September 2011

Injection pressure The development in fuel injection during is nothing short of a revolution! We can do things now that we couldn’t even dream about then. Generally, the big step towards electronic engine management was taken in conjunction with Euro 2. The breakthrough for unit injectors came with Euro 3. Injection pressures have doubled in this period – that’s one major reason why we have been able to maintain good fuel economy while reducing emissions. And for Euro 5 and Euro 6 … with Scania XPI … even more tricks are waiting round the corner. Scania Training September 2011