Question 1

Use of ordinary (light) water as a reactor moderator with enriched uranium fuel: evaluate the statement.  Statement: “Ordinary water is sometimes used as a moderator when enriched uranium is used as fuel in nuclear power plants.” Choose whether the …

Accepted Answer

Concept/Approach Light-water reactors (PWR/BWR) use ordinary water as moderator and coolant but require enriched uranium fuel (typically 3–5% U-235) to maintain criticality. Natural uranium needs better moderators like heavy water or graphite. Final Answer Agree.

Question 2

Purpose of supercharging an engine: select the most complete objective.  Context: Supercharging increases intake air density for higher specific output. Choose the correct statement describing why engines are supercharged.

Accepted Answer

Concept/Approach By boosting intake density, supercharging raises the power produced by a given displacement. This enables downsizing (lower mass and space for a given power) and provides higher power on demand. Final Answer All of the above.

Question 3

Key requirement of a good I.C. engine combustion chamber: choose the best criterion.  Select the most appropriate characteristic of a well-designed combustion chamber.

Accepted Answer

Concept/Approach An effective combustion chamber promotes rapid, stable combustion (adequate turbulence and mixture motion), good volumetric efficiency, and supports higher compression ratios—leading to high efficiency and power density. Why others are wrong “Minimum turbulence” harms combustion speed; “low compression ratio” and “low volumetric efficiency” reduce performance. Final Answer High thermal efficiency and power output.

Question 4

Diesel ignition delay terminology: identify the correct name for the interval between injection and ignition.  Definition prompt: In a CI (diesel) engine, the time between start of injection and actual start of combustion is called what?

Accepted Answer

Concept/Approach After fuel injection begins, atomization, vaporization, and mixing with hot compressed air take finite time before auto-ignition occurs. This interval is the ignition delay period. Final Answer Delay period.

Question 5

Typical diesel injection pressure: choose the closest standard value.  Select the approximate fuel injection pressure used in conventional diesel engines.

Accepted Answer

Concept/Approach Traditional mechanically-controlled DI diesels commonly use injection pressures in the ~150–250 bar range. Modern common-rail systems can exceed 1000 bar, but for textbook basics, ≈150 bar is the representative value among the given choices. Elimination 10 bar and 100 bar are too low; 500 bar is high for older conventional systems. Final Answer 150 bar.

Question 6

Secondary (bred) nuclear fuels used in power reactors: select the correct pair.  Definition: “Secondary fuel” refers to fissile material bred from fertile isotopes inside reactors. Choose the correct pair commonly identified as secondary fuels.

Accepted Answer

Concept/Approach Fertile isotopes Th-232 and U-238 breed fissile U-233 and Pu-239 respectively under neutron capture and subsequent decay. These bred fissile nuclides are termed secondary fuels. Final Answer U-233 and Pu-239.

Question 7

Effect of compression ratio on knock in petrol (SI) engines: evaluate the statement.  Statement: “Detonating (knocking) tendency in petrol engines increases as compression ratio increases.” Choose whether the statement is correct.

Accepted Answer

Concept/Approach Higher compression ratio raises end-gas temperature and pressure, reducing the ignition delay of the end-gas and making auto-ignition (knock) more likely for a given fuel octane. Therefore, knock tendency increases with CR unless higher-octane fuel or mitigating design measures are used. Final Answer Agree.

Question 8

Nuclear marine/space propulsion: fuel form for compact propulsion reactors  Reactors designed for propulsion applications (e.g., naval or space power units) require which fuel form to achieve a compact, long-life core at practical power density? Cho…

Accepted Answer

Given data Application: compact propulsion reactors (e.g., submarines, icebreakers). Concept/Approach To achieve high power density in a small core with long refueling intervals, the fuel must have a high fraction of fissile nuclei. Enriched uranium (typically enriched in U-235) provides sufficient reactivity in a compact geometry, unlike natural uranium which generally requires heavy moderation and large cores. Why others are not best “Any form” is too broad and incorrect; natural uranium would require impractically large cores for most propulsion uses; plutonium fuels pose different handling and design issues and are not the standard baseline choice. Final Answer Enriched uranium

Question 9

Diesel engines on weak (lean) mixtures: effect on thermal efficiency  For compression-ignition (diesel) engines operating with weak or lean mixtures (excess air), how does the thermal efficiency change? Choose the correct option.

Accepted Answer

Given data Engine type: compression-ignition (diesel), typically unthrottled and operating lean with excess air. Concept/Approach Diesel engines admit air first and inject fuel later. Running lean reduces pumping losses and often reduces heat transfer per unit fuel, bringing operation closer to the idealized cycle. Hence, thermal efficiency generally increases on leaner operation compared with richer diesel combustion. Notes Real engines have multiple influences (injection timing, combustion phasing, EGR), but foundational MCQ theory states that leaner (weak) mixtures in diesels indicate higher efficiency. Final Answer Higher

Question 10

Diesel ignition principle: fuel spray ignition due to hot compressed air  Statement: In a diesel (compression-ignition) engine, fuel is injected as a fine spray into the cylinder and it ignites because the compressed air temperature is high. Decide …

Accepted Answer

Given data Engine type: compression-ignition diesel. Concept/Approach In CI engines, air is compressed to a high pressure and temperature. Near the end of compression, finely atomized fuel is injected; the high air temperature causes auto-ignition without a spark. Final Answer True

Question 11

The correct mixture strength (by weight) for petrol is about

Accepted Answer

14.6:1

Question 12

A petrol engine, during suction stroke draws

Accepted Answer

a mixture of petrol and air

Question 13

A moderator

Accepted Answer

does not absorb neutrons

Question 14

A turbo-jet does not require a turbine to drive the compressor.

Accepted Answer

False

Question 15

For the same maximum pressure and heat input, the exhaust temperature of petrol engine is __________ than that of diesel engine.

Accepted Answer

more

Question 16

A supercharged engine as compared to an ordinary engine

Accepted Answer

all of these

Question 17

The ratio of the brake power to the indicated power is called

Accepted Answer

mechanical efficiency

Question 18

The frictional power (F.P.) is given by

Accepted Answer

F.P. = I.P. - B.P.

Question 19

The theoretically correct mixture of air and petrol is

Accepted Answer

15:1

IC Engines and Nuclear Power Plants Questions