Download
1 / 20
210 likes | 233 Views
Explore the impact of artificially breathing capacity, turbine sizing, and advanced turbocharging systems on turbocharged engines. Learn how selecting the right turbine size affects boost threshold, turbolag, fuel consumption, and overall engine performance. Discover the benefits of large and small turbines, the significance of turbine exducer bore selection, and the role of geometric design in turbocharger efficiency. Dive into studies on engine power, compactness, fuel economy, and the future of turbocharging technology. Uncover insights into achieving high volumetric efficiency, compression ratio impact, and the importance of turbo-cooling in optimizing engine performance.
E N D
Performance of Turbocharged I.C. Engines P M V Subbarao Professor Mechanical Engineering Department Impact of Artificially Breathing ….
Turbine Sizing • The selection of the turbine size is a bit simpler than the sizing of the compressor. • Important to note that the turbine size effects boost threshold, turbolag and fuel consumption. • Boost threshold is the engine speed at which there is sufficient exhaust gas flow to generate positive (intake) manifold pressure, or boost. • Turbolag is the difference between the time of demand for an increase in power raised by the engine and the time of turbocharger started providing increased intake pressure, and hence increased power. • The selection is basically just a balancing act. • There are no complicated maps or processes used to select the turbine size.
Large Turbine • Larger turbines, conversely, allow much more airflow through the compressor and reduce back pressure. • Demands less enthalpy exhaust in manifold . • Leads to higher boost thresholds and larger turbo lag.
Small Turbine • Smaller turbines will provide lower boost thresholds and better turbo response. • Able to create limited airflow through the compressor. • Demands higher enthalpy exhaust in manifold. • Leads to lower turbine exit pressure.
Selection of Turbine Exducer bore Higher Limit Lower Limit
Geometric Parameter : Casing for Turbine The A/R ratio of the turbine is the ratio of the housing discharge area to the radius of the center of the discharge area to the center of the turbine blades
Guide for selecting a turbine A/R ratio High Power Engine Lower Boost Threshold
Strange Thinking/Understanding for Future • Turbocharged modes were found to match or exceed the capabilities of typical larger bore normally aspirated engines found in passenger vehicles. • Case studies showed that A normally aspirated engine could be readily matched with the smaller turbocharged unit, with a 66% reduction in engine capacity. • It is possible to achieve 22% reduction in fuel consumption and CO2 emissions, including a reduction of 62% at idle conditions.
Advanced Turbo-charging Systems • Higher volumetric efficiency is achieved through increased pressure @ IVC. • Go back to Era of Otto or Diesel. • Compression ratio has a great impact on fuel consumption of an engine. • Generally, the bigger the compression ratio is, the lower the fuel consumption can be reached. • Knock limit constrains the compression ratio increase of SI engines. • It is known to all that any effort resulting in intake air temperature decreasing will extend the knock limit. • Attainment of higher volumetric efficiency with lower Tivcis the theme of advanced turbo-charging methods.
