سوال ۱۵ کنکور ارشد مهندسی مکانیک ۱۴۰۲

PART C: Reading Comprehension

PASSAGE 1:

Ever since the establishment of the California Air Resources Board (CARB) and Environmental Protection Agency (EPA), significant strides have been made in diesel engine emission control technology. The diesel emission control is being achieved using strategies involving in-situ and after-treatment techniques and even with their effective combinations. Among these techniques, recirculation of the exhaust gases back to the engine inlet is an in-situ approach for Nitrogen Oxides (NOx) control. Moreover, exhaust gas recirculation (EGR) has been used for controlling the onset of combustion process. Over the last five decades, the vehicle population across the globe has grown significantly. The concern over vehicular pollution increased steadily after 1960s Los Angeles episode. It is well known that vehicular emissions vary with engine type, operating conditions and fuel utilized, and all these aspects need to be addressed simultaneously for their abatement. The severity of engine pollutant depends on their concentration and exposure time and severely affects human health. Owing to inherent fuel economy advantage, diesel engines have made inroads into automotive applications beside their usual stationary domain. However, the diesel fuel operated vehicles are the major source of NOx and particulate emissions and responsible for the deterioration of ambient air quality. Many countries like Brazil, China, Sri Lanka, Denmark and France are in the process of eliminating diesel vehicles and enforcing heavy taxes and levies on such vehicles. Recently, Indian government banned the registration of diesel run private cars with capacity of 2000cc and above in certain cities. It is imperative that, the sustenance of diesel operated engines is possible with ultra-low emissions and lower fuel consumption. The NOx-PM trade-off in diesel engines is a classical challenge for developing emission control technology and hence stands at the forefront of diesel engine development. The NOx/PM emission could be restricted through in-cylinder control measures well ahead of their formation, or through after treatment control devices which involve the conversion of NOx/PM emission to relatively benign compounds

The NOx emissions could be controlled best by ----------.