The following is a description of a twin egr engine edited from
https://mechcontent.com/ and other sources
It is not a detailed examination of the Fiat engine, if theres anything obviously wrong please advise.
The internal combustion engine uses fuel and air to turn chemical energy to Kinetic energy movement by mechanical means . in our case a 4 stroke engine. The combustion of fuel (basicaly Carbon Hydrogen )with Air
The diesel engine has advantages in terms of fuel consumption, combustion efficiency and durability. It also emits lower carbon dioxide (CO2), carbon monoxide(CO) and hydrocarbons(HC). However, diesel engines are the major source of NOx and particulate matter emissions in urban areas. As the environmental concern increases, a reduction of NOx emission is one of the most important tasks for the automotive industry.
Exhaust gas recirculation (EGR) is a NOx emission control technique applicable to a wide range of diesel engines. There are two types HPEGR and LPEGR ours is dual loop EGR system with both. Each has its advantages and disadvantages as does the alternative SCR (adblue).
Thats why now how.
Power is controlled simply by varying the amount of fuel injected. As the mixture is richened (lower air-fuel ratio or AFR) to give more power, eventually a point is reached where all the oxygen is used up. Beyond this, soot (fine Carbon particles) starts to be emitted. Theoretically, complete combustion requires 14.5 AFR by weight (The stoichiometric air fuel ratio is the ratio that gives the amount of air required for the complete combustion of the unit amount of fuel.
If the mixture has a lower air-fuel ratio than a stoichiometric ratio then it is known as a lean mixture.
And if the air-fuel ratio of the mixture is higher than the stoichiometric ratio then this mixture is considered a rich mixture.
Petrol 14.7:1 Diesel14.5:1.
Lambda of 1.0 (lambda refers to air-fuel equivalence ratio).
when fully combusted, would yield nothing but CO2, H2O and the Nitrogen and any unused Oxygen passes through.
Some level of soot is always produced, but it can be held to acceptable levels by keeping the AFR below about 18. Other low level pollutants like unburned fuel and Carbon Monoxide are mostly oxidised with the use of a Catalyst (when hot enough). The soot is trapped by the DPF in the exhaust and oxidized at certain times. If combustion temperature/pressure is too high, some Nitrogen oxidises to unwanted NOx.
The purpose of Exhaust Gas Recirculation (EGR) is to reduce the percentage of oxygen entering the combustion chamber, and to add some water vapour. This reduces combustion temperature and pressure under part load conditions, which has the benefit of reducing the production of NOx
A High Pressure Loop (HPL) routes pre-catalyst exhaust gas via an EGR valve and a cooler into the inlet manifold. There is also a Throttle Body (TB) which restricts the incoming fresh air, lowering inlet manifold pressure to encourage EGR flow. The HPL has a fast response and high flow, but the recirculated gas has some soot content which can combine with residual oil vapour and leave deposits which cause eventual blockage. The HPL is best suited to lower speeds and loads.
A Low Pressure Loop (LPL) is an additional refinement, used in the twin EGR system. It routes post-catalyst exhaust gas via a LP EGR valve and a cooler into the inlet manifold. The LPL has a slower response and low flow at lower engine speeds, but the recirculated gas is cooler and cleaner (lower in soot). The LPL is best suited to higher speeds and loads.
Notice temperature and pressure is important in many of these stages hence the number of sensors used by the ECU to control the various valves and EGR systems, DPF regeneration and injector system.
The HPL and LPL are under the control of the engine management software, which relies upon the input from a multitude of sensors to determine the engine operating status. One of these sensors is an Oxygen Sensor (Lambda Sensor), as the level of residual oxygen in the exhaust is a sensitive indicator of AFR. Since the use of EGR reduces the oxygen level going into the combustion chamber, care must be taken that there is still enough for complete (or very near complete) combustion.
Regeneration of soot stored in the DPF is burnt to ash by the injection of diesel. World class would inject via a 5th injector in the DPF some Fiats use this method but others with space implications like the Ducato use diesel injection on the exhaust stroke (during the regen process to increase the exhaust temperature, which is necessary for the process to run. Some of that diesel finds its way past the piston rings into the sump, which is why the vans are fitted with oil degredation algorythym to notify you that an oil change is required, if the system calculates that the oil has been diluted beyond a certain threshold.
https://mechcontent.com/stoichiometric-air-fuel-ratio/
https://mechcontent.com/ and other sources
It is not a detailed examination of the Fiat engine, if theres anything obviously wrong please advise.
The internal combustion engine uses fuel and air to turn chemical energy to Kinetic energy movement by mechanical means . in our case a 4 stroke engine. The combustion of fuel (basicaly Carbon Hydrogen )with Air
The diesel engine has advantages in terms of fuel consumption, combustion efficiency and durability. It also emits lower carbon dioxide (CO2), carbon monoxide(CO) and hydrocarbons(HC). However, diesel engines are the major source of NOx and particulate matter emissions in urban areas. As the environmental concern increases, a reduction of NOx emission is one of the most important tasks for the automotive industry.
Exhaust gas recirculation (EGR) is a NOx emission control technique applicable to a wide range of diesel engines. There are two types HPEGR and LPEGR ours is dual loop EGR system with both. Each has its advantages and disadvantages as does the alternative SCR (adblue).
Thats why now how.
Power is controlled simply by varying the amount of fuel injected. As the mixture is richened (lower air-fuel ratio or AFR) to give more power, eventually a point is reached where all the oxygen is used up. Beyond this, soot (fine Carbon particles) starts to be emitted. Theoretically, complete combustion requires 14.5 AFR by weight (The stoichiometric air fuel ratio is the ratio that gives the amount of air required for the complete combustion of the unit amount of fuel.
If the mixture has a lower air-fuel ratio than a stoichiometric ratio then it is known as a lean mixture.
And if the air-fuel ratio of the mixture is higher than the stoichiometric ratio then this mixture is considered a rich mixture.
Petrol 14.7:1 Diesel14.5:1.
Lambda of 1.0 (lambda refers to air-fuel equivalence ratio).
when fully combusted, would yield nothing but CO2, H2O and the Nitrogen and any unused Oxygen passes through.
Some level of soot is always produced, but it can be held to acceptable levels by keeping the AFR below about 18. Other low level pollutants like unburned fuel and Carbon Monoxide are mostly oxidised with the use of a Catalyst (when hot enough). The soot is trapped by the DPF in the exhaust and oxidized at certain times. If combustion temperature/pressure is too high, some Nitrogen oxidises to unwanted NOx.
The purpose of Exhaust Gas Recirculation (EGR) is to reduce the percentage of oxygen entering the combustion chamber, and to add some water vapour. This reduces combustion temperature and pressure under part load conditions, which has the benefit of reducing the production of NOx
A High Pressure Loop (HPL) routes pre-catalyst exhaust gas via an EGR valve and a cooler into the inlet manifold. There is also a Throttle Body (TB) which restricts the incoming fresh air, lowering inlet manifold pressure to encourage EGR flow. The HPL has a fast response and high flow, but the recirculated gas has some soot content which can combine with residual oil vapour and leave deposits which cause eventual blockage. The HPL is best suited to lower speeds and loads.
A Low Pressure Loop (LPL) is an additional refinement, used in the twin EGR system. It routes post-catalyst exhaust gas via a LP EGR valve and a cooler into the inlet manifold. The LPL has a slower response and low flow at lower engine speeds, but the recirculated gas is cooler and cleaner (lower in soot). The LPL is best suited to higher speeds and loads.
Notice temperature and pressure is important in many of these stages hence the number of sensors used by the ECU to control the various valves and EGR systems, DPF regeneration and injector system.
The HPL and LPL are under the control of the engine management software, which relies upon the input from a multitude of sensors to determine the engine operating status. One of these sensors is an Oxygen Sensor (Lambda Sensor), as the level of residual oxygen in the exhaust is a sensitive indicator of AFR. Since the use of EGR reduces the oxygen level going into the combustion chamber, care must be taken that there is still enough for complete (or very near complete) combustion.
Regeneration of soot stored in the DPF is burnt to ash by the injection of diesel. World class would inject via a 5th injector in the DPF some Fiats use this method but others with space implications like the Ducato use diesel injection on the exhaust stroke (during the regen process to increase the exhaust temperature, which is necessary for the process to run. Some of that diesel finds its way past the piston rings into the sump, which is why the vans are fitted with oil degredation algorythym to notify you that an oil change is required, if the system calculates that the oil has been diluted beyond a certain threshold.
https://mechcontent.com/stoichiometric-air-fuel-ratio/
