Question

Comparative Analysis of Engines Rank a chainsaw (2-stroke SI), mini-van (4-stroke naturally aspirated SI), and a semitruck (4-stroke turbocharged CI) from LEAST to GREATEST at their maximum torque point based on each of the following performance parameters. Explain the reasoning for your order.

- Brake Power (example) ranking: Chainsaw < Mini-Van < Semi-Truck rationale: size of the engine and magnitude of load associated with each application

- Engine Speed

- Bmep

- Air/Fuel Ratio

- Brake Specific Fuel Consumption

- Mechanical Efficiency

- Volumetric Efficiency

Answer 1

Here we have to analyse a 2 stroke spark ignition engine. 4 stroke spark iginition engine( naturally aspirated meaning no turbocharger) and a 4 stroke turbocharged compression ignition engine.

A diesel engine or CI engine with TC will have higher power output and lower RPM. As in CI engines, ignition of fuel occur due to compression pressure inside the cylinder which generates heat which is above the auto ignition temperature of diesel. Hence the engine components are heavier and more torque is generated.

Engine Speed - chainsaw<semitruck< mini-van . This is because 4 stroke engines have usually higher RPM and lesser torque. And comparetevely, an SI engine will have more RPM than a CI engine.

Bmep - chainsaw< mini van< semi truck< -- 4 stroke CI engines usually have higher Bmep as they are turbocharged, which results in boost of power. IF the engine was not having TC, Bmep would have been less.

Air/ Fuel Ratio - semi truck< mini van < Chinsaw -- Ci engines have abundant air during compression stroke as it is turbocharged, and fuel is introduced at a later stage( 5-10 degree After TDC).

Brake Specific Fuel COnsumption - semitruck< Mini van< Chinsaw - This parameter depends upon the calorific value of fuel used as well as the power output generated. Roughly a 4 stroke CI engine offer the maximum milegae so SFOC is minimum in this case.

Mechanical efficiency - chainsaw< mini van < semi truck -- Mechanical effiiciency of CI turbocharged engines are higher compared to gasoline engines. 4 stroke SI have higher mechanical efficieny than 2 stroke SI engines.

Volumetric efficiecy_ Chainsaw< minivan < semitruck

Volumetric effieciency is the ratio of mass of air entering the cylinder to the volume of the cylinder. A turbochaged engines will have more mass of air entering inside the cylinder. Also a 4 stroke engine will draw more air than a 2 stroke SI engine as 4 stroke engine have a dedicated suction stroke.