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Explore Related Products. DMS Fast engine particulate analyzer. For this reason, mtu is equipping its Series engines for under floor drive systems with an SCR exhaust aftertreatment — with no exhaust gas recirculation. In this case, the nitrogen oxide limits are down 90 percent to 0. To meet these demanding targets, mtu uses both exhaust recirculation technology and an SCR system. As the introduction of Tier 4 final emissions regulations involves no further tightening of NOX values, mtu will retain ist exhaust gas recirculation technology.
This will involve optimization and further development of the injection and combustion systems and of turbocharging technology. The resultant mixture of fresh air and exhaust gas has a lower calorific value in terms of the volume. This lowers combustion chamber temperatures, thus reducing the production of nitrogen oxide NOX.
Benefits of exhaust gas recirculation from mtu Generally speaking, systems designed to reduce emissions must be modified to match the drive systems. It is necessary to modify the radiator, however, in order to cope with the increased cooling capacity of the engine. Compared to engine modifications involving an SCR system, this makes it much easier for customers to convert their units to meet new emissions standards because EGR systems for reducing nitrogen oxides require no additional operating media and thus involve no further expense or work on extra tanks and lines.
The customer benefits in terms of reduced costs for handling and maintenance. Principle of operation In exhaust gas recirculation, some of the exhaust gas is drawn off from the exhaust system, cooled and redirected back into the cylinders see Figure 2.
Although the exhaust fills the combustion chamber, it is not involved in the combustion reaction that takes place in the cylinder due to its low oxygen content. The speed of the combustion process overall is thus reduced, with the result that the peak flame temperature in the combustion chamber is lowered.
This dramatically reduces the production of nitrogen oxides. Patented solution from mtu : the donor cylinder concept Exhaust gas recirculation places higher demands on exhaust gas turbocharging, since higher boost pressures have to be achieved with reduced mass flow in the turbocharging system.
These high boost pressures are required to direct the increased mass flow resulting from the exhaust gas recirculation rate into the cylinder during the gas cycle. In addition, the exhaust gas can only be redirected back into the cylinders when there is a pressure drop between the exhaust and the charge air systems. This pressure drop must be established with an appropriately configured turbo charging system, which results in a reduction in turbocharging efficiency.
The pressure drop between the exhaust and the charge air systems leads to gas cycle los - ses. These factors tend to result in lower engine performance or higher fuel consumption. To improve the combined effect of exhaust gas recirculation and turbocharging, mtu has developed what is known as the donor cylinder exhaust gas recirculation system see Figure 3.
An exhaust valve donor valve holds back the exhaust gas flow downstream of the donor cylinders and thus creates the necessary pressure drop between the exhaust and the charge air systems. This means that the turbocharging system can be optimized to a very good efficiency level, with gas cycle losses only affecting the donor cylinders. Compared with conventional high-pressure exhaust gas recirculation as in the case of the Series engine , the donor cylinder concept Series and achieves lower fuel consumption, since it reduces the gas cycle losses in the engine and permits higher turbocharger efficiency levels.
Revised : 08 September Issue Date : June Anyone you share the following link with will be able to read this content:. Sorry, a shareable link is not currently available for this article. Provided by the Springer Nature SharedIt content-sharing initiative. Skip to main content. Search SpringerLink Search. Abstract In diesel engines, NOx formation is a highly temperature-dependent phenomenon and takes place when the temperature in the combustion chamber exceeds K.
SAE Download references. However as more torque and power is required, for example during full acceleration, the EGR valve closes to ensure as much oxygen enters the cylinder. As well are reducing NOx, EGR valves can be used in downsized GDi engines to reduce pumping losses and improve both combustion efficiency and knock tolerance. In diesel, it can also help to reduce diesel knock at idle.
Although there are several types of EGR valve -- earlier systems use a vacuum-operated valve, while newer vehicles are electronically controlled -- the main types can be broadly summarized as:. Diesel high pressure EGR valves divert the high-flow, high-soot exhaust gas before it enters the diesel particulate filter — the soot can combine with the oil vapor to create sludge. The gas is then passed back to the inlet manifold either via a pipe or internal drillings in the cylinder head.
A secondary valve is also used to help create a vacuum in the inlet manifold as this is not naturally present on diesel engines. Diesel Low pressure EGR valves divert the exhaust gas after it has passed through the diesel particulate filter -- this gas has a lower flow but is almost completely clean of soot.
The gas is then passed back to the inlet manifold via a pipe. Gasoline EGR valves divert the exhaust gases, much like the high pressure diesel equivalent. The vacuum created by cylinder depression, draws the exhaust gases in and the flow is regulated by the opening and closing of the EGR valve itself.
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