# Aktu Btech IC Engine, Fuel and Lubrication KME-054 Short Question, Notes Pdf

Learn more about the IC Engine, Fuel and Lubrication Short Question Notes from the B.Tech. AKTU Quantum Book. Learn the fundamentals of lubrication, fuel systems, and internal combustion engines for effective operation.

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## Unit-I: Introduction to IC Engines (Short Question)

Q1. Write the formula for efficiency of Otto and diesel cycle.

Ans. A. Efficiency of Otto Cycle:

B. Efficiency of Diesel Cycle:

Q2. State two differences between two stroke and four stroke engines.

OR

Differentiate between two stroke and four stroke engines.

Ans.

Q3. Define compression ratio.

Ans. The ratio of the volume at the start of compression to the volume at the end of compression is known as the compression ratio.

Q4. Compare SI and CI engine with respect to compression ratio and ignition.

Ans.

Q5. Draw actual p-v diagram for four stroke engine.

Ans. A. Actual p-v Diagram of a Four Stroke Otto Engine:

B. Actual p-v Diagram of Four Stroke Diesel Cycle:

Q6. Draw p-v and T-s diagram for air standard Ericsson cycle.

Ans.

Q7. What is mean effective pressure ?

Ans. The average pressure inside the cylinders of an internal combustion engine is known as mean effective pressure, and it depends on the calculated power output.

Q8. Compute bmep of four cylinder 2 stroke engine, 100 mm bore, 125 mm stroke when it develops a torque of 490 Nm.

Ans. Given: D = 100 mm, L= 125 mm, Tb = 490 Nm

To Find: Brake mean effective pressure (bmep).

1. We know that,

Q9. What do you mean by blow by losses ?

Ans. The process known as blow by loss occurs when combustion byproducts flow from the cylinder past the piston and piston rings and into the crankcase.

Q10.  Give the value of compression ratio for Otto cycle, Diesel cycle and Dual cycle.

Ans. 1. Compression ratio for Otto cycle is 6 to 10.

2. Compression ratio for Diesel cycle is 16 to 20.

3. Compression ratio for DuaB cycle is 12 to 16.

Q11. Draw p-v and T-s diagram for Otto, diesel and dual cycle.

Ans. A. p-v and T-s Diagram for Otto Cycle:

B. p-v and T-s Diagram for Diesel Cycle:

C. p-v and T-s Diagram for Dual Cycle:

## Unit-II: Combustion (Short Question)

Q1. What do you mean by combustion ?

Ans. Combustion is described as the release of energy in the form of heat as a result of a relatively quick chemical reaction between the hydrogen and carbon in the fuel and the oxygen in the air.

Q2. What are the necessary conditions for combustion to take place ?

Ans. Following conditions are necessary for combustion to take place:

• 1. A combustible mixture.
• 2. Some means to initiate combustion.
• 3. Stabilization and propagation of flame in the combustion chamber.

Q3. Define ignition delay.

OR

Explain delay period in CI engine.

Ans. It is also referred to as the preliminary phase because some fuel has already been added during this time but has not yet started to burn. This time span is measured from the beginning of the injection process until the pressure time curve separates from the motoring curve, which is the beginning of combustion.

Q4. What do you mean by performance number ?

Ans. Its ratio to the knock-limited indicated mean effective pressure of iso-octane is what is known as the knock-limited indicated mean effective pressure of test fuel.

Q5. Mention different types of combustion chamber used in SI engines.

Ans. Types of combustion chamber used in SI engines are as follows:

• 3. I-head combustion chamber, and

Q6. What is the cause for diesel smoke?

Ans. Diesel smoke results from incomplete fuel combustion inside the combustion chamber. Inadequate mixing and an inadequate air-fuel ratio are the two main causes of incomplete combustion.

Q7. What are the factors affecting combustion in CI engine?

Ans. The factors affecting combustion in CI engine are as follow:

• 1. Ignition quality of fuel,
• 2. Compression ratio,
• 3. Intake temperature, and
• 4. Engine speed.

Q8. Write on swirl and squish.

Ans. Swirl: It is a planned air movement that is designed to create a high relative velocity between the air and the fuel droplet for efficient mixing of the two in a short amount of time.

Squish: The volume of gas mixture at the outer radius of the cylinder is driven radially inward when this outer volume is decreased to zero as the piston moves towards TDC. Squish is the name for this radial inward motion of the gas mixture.

Q9. What are the types of combustion chamber used in CI engines?

Ans. Types of combustion chamber used in CI engines are:

• 1. Open or direct injection combustion chamber,
• 2. Turbulent chamber,
• 3. Precombustion chamber, and
• 4. Energy cell.

Q10. What are the methods of controlling diesel knock?

Ans. Following are the methods of controlling diesel knock:

• 1. High charge temperature,
• 2. High fuel temperature,
• 3. Good turbulence,
• 4. A fuel with a short induction period, and
• 5. Turbocharger.

Q11. What is the effect of compression ratio on the knocking in SI engine ?

Ans. With an increase in compression ratio, both pressure and temperature at the end of the compression stroke rise, increasing the likelihood of knocking.

Q12. What is swirl ratio ?

Ans. It is the ratio of the rotating speed of the air to that of the crankshaft.

Q13. Why should the surface to volume ratio of a combustion chamber be minimum ?

Ans. 1. The larger this ratio, the higher the heat losses and cooler the combustion chamber walls will be, which will lead to a higher concentration of hydrocarbons in the exhaust stream.

2. As a result, the surface to volume ratio should be as low as possible to reduce the production of hydrocarbons.

Q14. Define the term tumble.

Ans. It is characterized as secondary rotating flow produced by the tumble squish motion.

Q15. What is equivalence ratio ?

Ans. The ratio of the actual fuel-to-air mixture to the stoichiometric mixture is known as the equivalence ratio. It is denoted by 𝞍.

Q16. Explain stoichiometric air-fuel ratio.

Ans. A mixture of air and fuel known as a stoichiometric air-fuel ratio has just the right amount of oxygen for the fuel to burn completely.

## Unit-III: Carburetion and Fuel Injection (Short Question)

Q1. What do you mean by carburetion ?

Ans. Carburetion is the process of creating a combustible fuel-air combination outside the cylinder of a SI engine.

Q2. What is carburetor ?

Ans. It is an instrument that atomizes the fuel and blends it with air.

Q3. Mention types of carburetors.

Ans. Types of carburetors are as follows :

• 1. Open choke type, and
• 2. Constant vacuum type.

Q4. Why a rich mixture is required for maximum power ?

Ans. When slightly more fuel is consumed than necessary, the most energy is released because all of the oxygen in the cylinder is utilized. It is not advisable to mix a mixture that is richer than this since it will lead to poor combustion and a lower release of energy.

Q5. What are the functions of a fuel injection system ?

Ans. The main functions of a fuel injection system are:

• 1. Filter the fuel,
• 2. Meter the correct quantity of fuel to be injected,
• 3. Control the rate of fuel injection, and
• 4. Atomize the fuel into fine particles.

Q6. Why is float chamber vented to the atmosphere ?

Ans. In order to maintain a constant pressure on the fuel’s surface that is equivalent to that of the atmosphere, the float chamber is vented to the atmosphere through a tiny hole in the lid.

Q7. Mention various types of MPFI system.

Ans. Types of MPPI system are as follows:

• 1. Port injection system.
• 2. Throttle body injection system.

Q8. What is scavenging in two stroke cycle engine ?

Ans. In a two-stroke engine, intake air must be introduced at a pressure greater than atmospheric pressure; this high pressure air forces the majority of the exhaust residue out of the still-open exhaust port as it enters the cylinder. Scavenging is the term for this.

Q9. Can simple plain tube carburetor use at higher altitude ? If yes and no then why ?

Ans. No, a simple plain tube carburetor cannot be utilised at a high altitude due to the fact that the air density reduces and it is more difficult to make a rich air-fuel mixture at such a high altitude. To create a rich air-fuel mixture, it must be equipped with additional equipment. Simple carburetors cannot be used on their own at high altitudes.

Q10. State various types of injection system.

Ans. Types of injection system are as follows:

• 1. Air injection.
• 2. Solid injection:
• i. Individual pump and injector,
• ii. Common rails system, and
• iii. Distributor system.

Q11. What is the function of fuel pump?

Ans. The purpose of the fuel pump is to provide precisely measured fuel under pressure at the appropriate time to each cylinder’s injector.

Q12. What is the function of fuel injector ?

Ans. The primary purpose of a fuel injector is to atomize fuel into tiny droplets with a high surface area, which improves mixing and, ultimately, combustion.

Q13. Define injection timing.

Ans. The timing at which fuel is injected into the inlet manifold is known as the “injection timing,” according to definition.

Q14. What do you mean by turbocharger ?

Ans. Turbocharger is centrifugal compressor driven by the exhaust gas turbines.

Q15. What are the types of turbocharging?

Ans. Following are the types of:

• 1. turbocharging: Constant Pressure Turbocharging.
• 2. Pulse Turbocharging.
• 3. Pulse Converter.
• 4. Two-Stage Turbocharger.
• 5. Miller Turbocharging.

## Unit-IV: Engine Emission and Control (Short Question)

Q1. What are the major pollutants in exhaust emission ?

Ans. Major pollutants in exhaust emission are as follows:

• 1. Carbon monoxide (CO),
• 2. Hydrocarbons (HC), and
• 3. Oxides of nitrogen (NOx).

Q2. What is catalytic converter ?

Ans. It is a device that is installed in the exhaust system of a vehicle to lower the amount of HC and CO by acting as an oxidising catalyst and the amount of NO by acting as a reducing catalyst.

Q3. Write the name of various fuels used in IC engines.

Ans. Following fuels are used in IC engines:

• 1. Solid fuel: Powdered coal.
• 2. Liquid fuel: Gasoline and diesel.
• 3. Gaseous fuel: Coal gas.

Q4. What is octane and cetane number ?

OR

Explain octane number and cetane no. in brief.

Ans. Octane Number: It is described as the volume percentage of iso-octane in a mixture of iso-octane and regular heptane that precisely matches the fuel knocking intensity in a typical engine under a given set of typical operating circumstances.

Cetane Number: When combustion is carried out in a typical engine under predetermined operating circumstances, it is defined as the volume percentage of normal cetane in a combination of normal cetane and a-methyl naphthalene that has the same igniting properties as the test fuel.

Q5. What is motor octane no. and research octane no. ?

Ans. Motor Octane Number: It describes how fuel in an engine responds to high temperatures and speeds.

Research Octane Number: It explains how fuel in the engine behaves at lower temperatures and speeds.

Q6. List the use of LPG as SI engine fuel.

Ans. LPG is widely used in buses, trucks and cars.

Q7. Define emission.

Ans. The term “emission” refers to the combustion byproducts that occur inside an automobile’s engine cylinders and are released into the atmosphere through the exhaust system when the engine is running.

• 1. Economical.
• 2. Reduces harmful engine emission.

• 1. Low volumetric efficiency.
• 2. Large pressure required for storage.

Q9. Explain fuel quality standards.

Ans. The regulations governing fuel quality are a crucial and necessary precaution for both the environment and customers. The guidelines are designed to limit car emissions that harm our air quality and cause environmental and health issues.

Q10. What is the significance of octane no. and cetane no. for the different fuels ?

Ans. Significance of Octane Number: The engine can be supercharged to high output without detonating at higher octane numbers.

Significance of Cetane Number: Less diesel knocking occurs when the fuel has a higher cetane rating.

Q11. Differentiate between 2 way catalytic converter and 3 way catalytic converter.

Ans.

Q12. What are the alternate fuels for IC engines?

Ans. Following are the alternate fuels for IC engines:

1. LPG,                                           2. CNG,

3. Biogas, and                                4. Coal gas.

## Unit-V: Engine Cooling and Lubrication (Short Question)

Q1. Differentiate among flash point temperature, fire point temperature and self ignition temperature.

Ans.

Q2. How ignition system is necessary in IC engine ?

Ans. An ignition system is required to ignite the mixture and begin combustion.

Q3. Write the different types of cooling system.

Ans. Types of cooling systems are as follows:

• 1. Air cooling system, and
• 2. Water cooling system.

Q4. What is the purpose of engine cooling ?

Ans.  Engine cooling is used to maintain a low engine temperature in order to prevent the loss of volumetric efficiency and the threat of engine failure.

Q5. What is the significance of flash and fire points of a lubricant ?

Ans. Flash Point: A tiny flame is swept across the lubricating oil’s surface to determine the lowest temperature at which it will flash.

Fire Point: The oil will burn continually down to the fire point, which is the lowest temperature.

Q6. What is the function of radiator?

Ans. Radiators have the function of rejecting coolant heat to the outside air.

Q7. Write down the names of different types of radiator matrices.

Ans. Following are the different radiator matrices:

• 1. Honeycomb block type,
• 2. Ribbon-cellular type,
• 3. Tube and fin type, and
• 4. Tube and corrugated fin type.

Q8.  Write the importance of fan in the radiator.

Ans. To maintain the necessary air movement across the radiator matrix and to lower the temperature of the water, a fan is provided.

Q9. Write the name of ignition systems.

Ans. Following are the name of ignition systems:

• 1. Battery ignition system,
• 2. Magneto ignition system, and
• 3. Electronic ignition system.

Q10. What is engine friction ?

Ans. The discrepancy between the advertised horsepower and the brake horsepower available at the output shaft is known as engine friction.

Q11. What are the disadvantages of overcooling?

Ans. Following are the disadvantages of overcooling:

• 1. There is a potential that an engine component will corrode.
• 2. Starting an engine becomes challenging at extremely low temperatures.
• 3. The heat that may be used to expand the gases will be lost if the engine is overcooled.

Q12. What are the disadvantages of undercooling?

Ans. Following are the disadvantages of undercooling:

• a. Undercooling may cause a piston’s size to grow, which would stop it from moving inside the cylinder.
• b. Undercooling may cause the lubricant to evaporate.

Ans. The combustion performance of fuels produced by knock and surface ignition is improved by the use of additives.

Q14. By what process crude oil is separated into gasoline, kerosene and fuel oil?

Ans. Fuel oil, kerosene, and petrol are produced from crude oil using the fractional distillation process.