Basics of I.C.Engines: Heat Engine Classification
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Questions and Answers

What is the main function of a heat engine?

  • Converting electrical energy into mechanical work
  • Transforming thermal energy into chemical energy
  • Producing light energy from chemical combustion
  • Turning the chemical energy of a fuel into thermal energy for mechanical work (correct)

    • Which type of engine transfers heat to a second fluid that is the working fluid of the cycle?

  • Petrol engine
  • External combustion engine (correct)
  • Internal combustion engine
  • Diesel engine

    • What type of engine has the combustion of air and fuels taking place inside the cylinder?

  • Reciprocating engine (correct)
  • Rotary engine
  • External combustion engine
  • Gas engine

    • Which type of engines use a turbine for their basic design?

    <p>Rotary engine</p> Signup and view all the answers

    What distinguishes a four-stroke engine from a two-stroke engine?

    <p>The number of strokes per cycle</p> Signup and view all the answers

    In which type of heat engine does the combustion of air and fuels take place directly in the cylinder?

    <p>Internal combustion engine</p> Signup and view all the answers

    What type of engine has combustion of air-fuel inside the engine cylinder?

    <p>Diesel engine</p> Signup and view all the answers

    Which type of engine uses cheaper fuels including solid fuels?

    <p>External combustion engine</p> Signup and view all the answers

    What is the function of piston rings in a reciprocating IC engine?

    <p>Provide an airtight seal to prevent gas leakage</p> Signup and view all the answers

    Which component of a reciprocating IC engine is responsible for transmitting the force exerted by the burning of the charge to the connecting rod?

    <p>Piston</p> Signup and view all the answers

    What is the main purpose of a cylinder head in an IC engine?

    <p>Provide an airtight seal at the top of the cylinder</p> Signup and view all the answers

    In which type of engine is a boiler used for combustion of air-fuel?

    <p>External combustion engine</p> Signup and view all the answers

    Which type of ring on the piston provides an effective seal to prevent oil leakage into the engine cylinder?

    <p>Oil ring</p> Signup and view all the answers

    What is the main function of connecting rod in a reciprocating IC engine?

    <p>Convert reciprocating motion into circular motion</p> Signup and view all the answers

    What is the significance of using special alloys in internal combustion engines?

    <p>To withstand high pressure and temperature</p> Signup and view all the answers

    What feature distinguishes between single-cylinder and multi-cylinder engines?

    <p>Cylinder arrangement</p> Signup and view all the answers

    What is the reverse process to combustion?

    <p>Dissociation</p> Signup and view all the answers

    At what temperature does the dissociation of CO2 into CO and O2 start commencing?

    <p>1000°C</p> Signup and view all the answers

    Which gases tend to prevent the dissociation of CO2?

    <p>CO and O2</p> Signup and view all the answers

    In internal combustion engines, what causes a reduction in the maximum temperature and pressure?

    <p>Heat transfer to the cooling medium</p> Signup and view all the answers

    What reduces the maximum temperature by about 300°C even at the chemically correct air-fuel ratio?

    <p>Dissociation</p> Signup and view all the answers

    What is the effect of dissociation on output power in a spark-ignition engine?

    <p>Decreases output power</p> Signup and view all the answers

    What process can be looked at as the disintegration of combustion products at high temperature?

    <p>Dissociation</p> Signup and view all the answers

    What is the function of the crankshaft in an internal combustion engine?

    <p>Converts reciprocating motion of the piston into rotary motion</p> Signup and view all the answers

    Which alloy is commonly used for manufacturing the connecting rod in an internal combustion engine?

    <p>Aluminum alloys</p> Signup and view all the answers

    What is the Dead Centre in an internal combustion engine?

    <p>Position at the end point of the stroke where piston direction is reversed</p> Signup and view all the answers

    What is the main function of a flywheel in an internal combustion engine?

    <p>Stores excess energy during power stroke to maintain speed constant</p> Signup and view all the answers

    In a four-stroke engine, what happens during the suction stroke?

    <p>Suction valve open, fresh air-fuel charge drawn into the cylinder</p> Signup and view all the answers

    Which engine has a heavier flywheel due to non-uniform turning movement?

    <p>Four-stroke engine</p> Signup and view all the answers

    What is the role of the clearance volume in an internal combustion engine?

    <p>Volume of space on the combustion side of the piston at top dead centre</p> Signup and view all the answers

    Which term refers to the nominal volume generated by the working piston between two dead centres?

    <p>Swept volume</p> Signup and view all the answers

    'Volumetric efficiency' in an internal combustion engine relates to what aspect of its operation?

    <p>'Volumetric efficiency' refers to the air-fuel mixture drawn into the cylinder compared to its total volume.</p> Signup and view all the answers

    'Compression ratio' in an internal combustion engine is defined as what?

    <p>'Compression ratio' is the ratio of swept volume to clearance volume.</p> Signup and view all the answers

    What is the expansion ratio or pressure ratio in an Otto cycle?

    <p>rp = p3/p2</p> Signup and view all the answers

    During which process in the Otto cycle is heat rejected to an external sink?

    <p>Constant Volume Heat Rejection Process</p> Signup and view all the answers

    What is the characteristic gas constant R in relation to specific heats?

    <p>R = Cp - Cv</p> Signup and view all the answers

    At what temperature range do gases generally show an increase in specific heat?

    <p>300 K to 2000 K</p> Signup and view all the answers

    What is the relationship between temperature T2 and T1 during adiabatic compression in an Otto cycle?

    <p>$T2 = T1(1-r^{(\gamma-1)})$</p> Signup and view all the answers

    Which equation represents the increase in specific heat for gases at higher temperatures?

    <p>$Cp = a_1 + k_1T + k_2T^2$</p> Signup and view all the answers

    What happens to the final temperature and pressure if variable specific heats are considered during the compression stroke in an Otto cycle?

    <p>They decrease</p> Signup and view all the answers

    What does the difference between Cp and Cv depend on for gases?

    <p>$T$</p> Signup and view all the answers

    What is the value of specific heat for air at 300 K?

    <p>$Cp = 1.005 kJ/kg K$</p> Signup and view all the answers

    What is the work done formula in an Otto cycle?

    <p>$W = Cp(T3-T2) - Cv(T4-T1)$</p> Signup and view all the answers

    What is a characteristic of a two-stroke engine?

    <p>One power stroke in each revolution of the crankshaft</p> Signup and view all the answers

    Why is the flywheel lighter in a two-stroke engine?

    <p>As a result of more uniform turning movement</p> Signup and view all the answers

    What is a downside of a two-stroke engine?

    <p>Higher rate of wear and tear</p> Signup and view all the answers

    Which type of engine uses the Otto cycle?

    <p>SI engine</p> Signup and view all the answers

    What is a characteristic of a diesel engine?

    <p>Low self-ignition temperature</p> Signup and view all the answers

    What type of heat addition does the Otto cycle operate with?

    <p>Isochoric</p> Signup and view all the answers

    What assumption is made about the gas in the cylinder for air-standard cycles?

    <p>'Air' obeys gas laws and has constant specific heats</p> Signup and view all the answers

    Why is the air-cycle approximation used despite not closely representing actual cylinder conditions?

    <p>To obtain approximate answers to complex engine problems</p> Signup and view all the answers

    What defines the simplest theoretical cycle used for calculating conditions in internal combustion engines?

    <p>'Air' acting as a perfect gas with certain assumptions</p> Signup and view all the answers

    What happens to the maximum temperature as the air-fuel ratio decreases in an internal combustion engine?

    <p>Increases</p> Signup and view all the answers

    Why are dissociation effects less pronounced in a CI engine compared to an SI engine?

    <p>Presence of excess air and heterogeneous mixture</p> Signup and view all the answers

    How does dissociation affect the pressure in the expansion stroke of an internal combustion engine?

    <p>Decreases pressure</p> Signup and view all the answers

    Which type of loss occurs when combustion gases leak past the piston rings into the crankcase?

    <p>Blowby Losses</p> Signup and view all the answers

    What is the main cause of incomplete combustion in an internal combustion engine?

    <p>Ineffective spark-ignition and combustion</p> Signup and view all the answers

    How do exhaust heat losses affect the overall efficiency of an internal combustion engine?

    <p>Reduce efficiency</p> Signup and view all the answers

    Which process in the Otto Cycle corresponds to spark-ignition and combustion in an actual engine?

    <p>2?3</p> Signup and view all the answers

    Why do engine designers work to minimize friction losses between moving engine components?

    <p>To improve overall efficiency</p> Signup and view all the answers

    What effect does a rich mixture have on dissociation effects in an internal combustion engine?

    <p>Increases dissociation effects</p> Signup and view all the answers

    What is the primary reason for lower peak gas temperatures in a compression-ignition (CI) engine compared to a spark-ignition (SI) engine?

    <p>Heterogeneous mixture composition and excess air in CI engines</p> Signup and view all the answers

    What is the expression for the thermal efficiency of an Otto cycle?

    <p>1 - (T4 - T1)/(T3 - T2)</p> Signup and view all the answers

    What is the impact of increasing the compression ratio on the thermal efficiency of an Otto cycle?

    <p>Increases efficiency</p> Signup and view all the answers

    What does the thermal efficiency of an Otto cycle depend on?

    <p>Compression ratio only</p> Signup and view all the answers

    In the Otto cycle, what is the relationship between temperatures T1, T2, T3, and T4?

    <p>T1 = T2, T3 = T4</p> Signup and view all the answers

    What factor contributes to increasing the efficiency of an Otto cycle?

    <p>Increasing the compression ratio</p> Signup and view all the answers

    How is the net work output for an Otto cycle represented?

    <p>(p3V3 - p4V4)/(x-1) - (p2V2 - p1V1)/(x-1)</p> Signup and view all the answers

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