RRB JE Mechanical-IC ENGINE Questionbank 2

Mechanical-Engineering

Solex carburettors is —-? (RRB Mumbai SSE 05.10.2008)

multiple venturi
constant choke
constant vacuum
multi jet

Explanation:

Solex and Zenith carburettors belong to constant choke carburettor. In constant choke carburettor, air and fuel areas are always maintained constant. S.U. and Carter carburettors belong to constant vacuum carburettor.

Which of the following does not relate to spark ignition engine? (RRB Allahabad JE 19.12.2010)

Carburettor
Fuel injector
Spark plug
Ignition coil

Explanation:

Fuel injector is used in CI engine. Spark ignition engines use carburettor, spark plug, and ignition coil.

Which of the following cycle is used in spark ignition (SI) engine? (RRB Chandigarh SSE 25.10.2009)

Carnot cycle
Diesel cycle
Dual cycle
Otto cycle

Explanation:

Otto cycle is used in spark ignition (SI) engines. It consists of two constant volume (V-C) processes and two isentropic (S-C) processes. Efficiency η = 1 – 1/(r_c)^γ-1.

In an Otto cycle, how does heat addition takes place? (BMRCL JE 24 Feb. 2019)

Irreversibly at constant pressure
Irreversibly at constant volume
Reversibly at constant pressure
Reversibly at constant volume

Explanation:

All processes are reversible and heat rejection and heat addition occur at constant volume.

Ignition quality of petrol is expressed by —-? (JMRC JE 10.06.2017) (RRB JE Allahabad 2014)

octane number
cetane number
calorific value
self-ignition temperature

Explanation:

Ignition quality of petrol is expressed by octane number. High octane number means lower detonation. Iso-octane has ON = 100, n-Heptane has ON = 0.

Which factor contributes to the efficiency of the Otto cycle? (BMRCL JE 24 Feb. 2019)

Compression ratio
Operating pressure
Operating temperature
None of these

Explanation:

Efficiency of Otto cycle η = 1 – 1/(r_c)^γ-1. It depends on compression ratio (r_c) and adiabatic index (γ).

The minimum cranking speed in case of petrol engine is about —-? (RRB Mumbai SSE 19.12.2010) RRB Bangalore Section Eng. (Mech.), 01.02.2009

half the operating speed
one-fourth of operating speed
250 – 300 rpm
60 – 80 rpm

Explanation:

Minimum cranking speed in petrol engine is about 60-80 rpm. The starter motor rotates the flywheel, turning the crankshaft and starting piston movement.

For an Otto cycle, what is the air standard efficiency (in %), if the compression ratio is 5 for the swept volume? (Konkan Railway STA 2017)

45
47.46
49.74
50

Explanation:

η = 1 – 1/(r_c)^γ-1 = 1 – 1/5^0.4 = 1 – 1/1.903 = 0.4746 = 47.46%.

Which denoted path is followed by the Otto cycle in the below P-V diagram? (DMRC JE 2013)

1-2-4-7-1
1-2-3-5-7-1
1-2-6-7-1
None of these

Explanation:

1-2-4-7-1 path denotes the Otto cycle. Diesel cycle: 1-2-6-7-1. Dual cycle: 1-2-3-5-7-1.

Otto cycle is the air standard cycle of —-? (Konkan Railway TA 2017)

compression ignition (CI) engine
spark ignition (SI) engine
both SI and CI engines
None of these

Explanation:

Otto cycle corresponds to spark ignition engines. Process 1-2: Isentropic compression, 2-3: Heat supplied reversibly at constant volume, 3-4: Isentropic expansion, 4-1: Constant volume heat rejection.

With increasing temperature of intake air, IC engine efficiency —-? (RRB JE Bhopal Paper-1 (Shift-I), 28.08.2015)

Decreases
Increases
Remains same
Depends on other factors

Explanation:

η = 1 – T₁/T₂. When intake air temperature T₁ increases, efficiency of the IC engine decreases.

DPF is the acronym of —-? (RRB Kolkata Diesel JE 25.10.2009)

Direct purification filter
Differential proportional function
Diesel particulate filter
Diesel purification facility

Explanation:

DPF stands for Diesel Particulate Filter, a device designed to remove diesel particulate matter or soot from exhaust gas.

In a carburetor idling system is used —-? (RRB Chandigarh SSE 25.10.2009)

For cold starting
To compensate for dilution of charge due to residual gases
For rapid opening of throttle
For meeting maximum power requirements

Explanation:

The idling system compensates for dilution of charge due to residual gases. Economizer is for maximum power, acceleration pump for rapid throttle opening, and choke for cold starting.

How many power strokes per second shall take place in a four-stroke petrol engine rotating at 3000 r.p.m.? (RRB Mumbai C&G JE 25.10.2009)

1500
25
50
100

Explanation:

For a four-stroke engine, power strokes per second = N/(2×60) = 3000/120 = 25.

Thermal efficiency of CI engine is higher than that of SI engine due to —-? (RRB JE Bhopal Paper-I (Shift-II), 28.08.2015)

Fuel used
Higher compression ratio
Constant pressure heat addition
Lower compression ratio

Explanation:

Thermal efficiency of CI engine is higher due to higher compression ratio. CI engine CR: 16-24, SI engine CR: 6-12.

Alternator in an automobile is used to —-? (RRB JE Chandigarh 2014) RRB Kolkata Jr. Engineer-II Mech. DRG & Design, 11.06.2006

convert extra engine power into electric power
convert the DC of battery to AC
none of the above
recharge the battery continuously

Explanation:

Alternator in an automobile is used to recharge the battery continuously.

The compression ratio used in a high speed C.I. engine is of the order of —-? (RRB Allahabad JE 09.09.2012) RRB Bangalore Material Engg. 21.11.2004

Explanation:

The compression ratio used in a high speed CI engine is of the order of 20. Diesel engine CR: 16-24, Petrol engine CR: 6-12.

What is the cetane value of α-methyl naphthalene? (RRB Bhubneshwar JE II 29.11.2008)

Explanation:

Cetane value of α-methyl naphthalene = 0. Cetane value of n-cetane = 100. α-methyl naphthalene is short and complex chain paraffin, highly supportive to knock.

A high speed diesel engine theoretically operates on —-? (RRB Bhubneshwar JE-II 19.12.2010)

constant pressure cycle
constant volume cycle
constant temperature cycle
mixed cycle of constant pressure and constant volume

Explanation:

High speed diesel engines theoretically operate on mixed cycle (dual cycle) of constant pressure and constant volume.

Most high speed compression ignition engines operate on —-? (RRB Mumbai SSE 05.10.2008)

Diesel cycle
Otto cycle
Joule cycle
Mixed dual cycle

Explanation:

Most high speed compression ignition engines operate on Dual Combustion Cycle.

Cetane number is the measure of —-? (RRB JE Ahmedabad 2014)

Viscosity of fuel
Ignition quality
Calorific value of fuel
Auto-ignition

Explanation:

Cetane number is the measure of ignition quality of fuel. Higher cetane number means more resistance to knocking/detonation.

The fluid in the petrol engine (S.I.) during compression contain —-? (RRB Malda SSE 25.10.2009)

Fuel only
Fuel or Air
Air only
Mixture of air and fuel

Explanation:

During compression in petrol engine (SI), the fluid contains a mixture of air and fuel. In diesel engine, it contains only air.

Why we cannot achieve higher compression ratio for Otto engines like diesel engines? (RRB Mumbai C&G SSE 25.10.2009)

Otto engines generally have thinner walls
Petrol engines have high ignition temperatures
Knocking occurs due to pre-ignition
All of the above

Explanation:

Higher compression ratio cannot be achieved in Otto engines due to thinner walls, high ignition temperatures, and knocking due to pre-ignition.

The commercially available petrol in India has Octane rating of —-? (RRB Bhopal TM SSE 25.10.2009)

20-30
40-50
85-90
60-75

Explanation:

Commercially available petrol in India has octane rating of 85-90. Octane number can be greater than 100 for LPG and CNG.

The cetane rating of diesel fuel is in the order of —-? (RRB Bhopal TM SSE 25.10.2009)

Explanation:

Cetane rating of diesel fuel is in the order of 45. Cetane and α-methylnaphthalene are reference fuels to determine cetane number.

The chemically correct stoichiometric ratio for petrol is —-? (RRB Bangalore SSE 09.09.2012)

18:1
15:1
14.8:1
11:1

Explanation:

The stoichiometric A/F ratio by mass for petrol is 14.8:1. For CI engines, it varies from 18:1 to 80:1.

If the air-fuel mixture ignites before the spark at spark plug, the condition is called —-? (RRB Bhopal SSE 09.09.2012)

Detonation
Ignition
Pre-ignition
Rumble

Explanation:

If the air-fuel mixture ignites before the spark at the spark plug, it is called pre-ignition. In SI engine, detonation occurs near the end of combustion.

For given compression ratio in Otto cycle, which of the following will give the highest efficiency? (RRB Bangalore SSE 09.09.2012)

Oxygen
Nitrogen
Air
Argon

Explanation:

Argon is monoatomic with the highest specific heat ratio (γ). Hence for argon, efficiency of Otto cycle will be highest for a given compression ratio.

If the compression ratio is increased in S.I. engine, the knocking tendency will —-? (RRB Bhubneshwar JE-II 19.12.2010)

Increase
Decrease
Not be affected
Cannot be predicted

Explanation:

By increasing compression ratio, air standard efficiency increases theoretically, but knocking tendency increases, decreasing engine efficiency. For diesel engine, knocking decreases with increase in CR.

In a low speed S.I. engine, the inlet valve closes approximately —-? (JMRC JE 10.06.2017) (RRB Chandigarh SSE 25.10.2009)

40° after BDC
30° before BDC
10° after TDC
10° before BDC

Explanation:

In a low speed SI engine, the inlet valve closes approximately 40° after BDC.

The function of carburettor is —-? (RRB Malda SSE 25.10.2009)

Refining the fuel
Increase the pressure of fuel vapours
Inject petrol in cylinder
Atomise and vapourise the fuel and to mix it with air in proper ratio

Explanation:

The function of carburettor is to atomise and vapourise fuel and mix it with air in proper ratio.

Air standard efficiency of an Otto cycle having compression ratio 4 and adiabatic exponent for air γ = 1.5 will be —-? (RRB Patna JE 25.10.2009)

50%
75%
35%
5.0%

Explanation:

η = 1 – 1/(r_c)^γ-1 = 1 – 1/(4)^0.5 = 1 – 1/2 = 0.5 = 50%.

Chemically correct air-fuel ratio by mass for combustion of petrol is approximately —-? (RRB Bangalore SSE 09.09.2012)

Explanation:

Chemically correct air-fuel ratio by mass for petrol is approximately 15. Starting: 3:1-5:1, Idling: 10:1, Cruising: 16:1, Max power: 12.5:1.

Higher octane rating for S.I. engine fuel indicates that it has —-? (RRB Chandigarh SSE 09.09.2012)

higher calorific value
higher volatility
higher ignition lag
lower ignition lag

Explanation:

Higher octane rating for SI engine fuel indicates higher ignition lag. Higher octane number means better fuel burns within the engine.

Air standard efficiency of an Otto cycle having compression ratio of 5 will be —-? (DMRC JE 20.04.2018)

1 – 5^γ-1
1 – 1/5^γ-1
1 + 1/5^γ-1
None of these

Explanation:

η = 1 – 1/(r_c)^γ-1 = 1 – 1/5^γ-1.

In an engine working on Otto cycle, air-fuel mixture is compressed from 400 C.C. to 100 C.C. if γ = 1.5, calculate the thermal efficiency of cycle. (RRB Allahabad JE 09.09.2012)

50%
55%
68%
None of these

Explanation:

Compression ratio = 400/100 = 4. η = 1 – 1/(4)^0.5 = 1 – 1/2 = 0.5 = 50%.

In Petrol engine, air-fuel ratio is controlled by —-? (RRB Jammu SSE 09.09.2012)

Distributor
Injector
Governor
Carburettor

Explanation:

Carburettor is a device used for atomizing and vaporizing fuel and mixing it with air in varying proportions.

Mixture formation in a carburetor is based on the principle of —-? (RRB Chandigarh SSE 09.09.2012)

Pascal’s law
Buoyancy principle
Venturi principle
Pitot tube principle

Explanation:

Mixture formation in carburetor is based on Venturi principle (Bernoulli’s theorem).

Tetraethyl lead is used as —-? (RRB Bhopal SSE 09.09.2012)

Pain killer
Fire extinguisher
Mosquito repellent
Petrol additive

Explanation:

TEL (Tetra Ethyl Lead) is used as petrol additive to increase octane number.

Octane number of gasoline is a measure of its —-? (DMRC JE 2013)

Resistance to Knock
Ignition delay
Ignition temperature
Smoke point

Explanation:

Octane number is the measure of resistance of gasoline/petrol against knocking or pre-ignition.

In spark ignition (SI) engines, the possibility of knocking can be reduced by —-? (RRB Gorakhpur Design SSE 09.09.2012)

increasing compression ratio
decreasing compression ratio
increasing the coolant temperature
advancing the spark timing

Explanation:

In SI engines, knocking can be reduced by decreasing compression ratio, resulting in lower peak temperature generation.

The delay period in a petrol engine is of the order of —-? (RRB Kolkata SSE 09.09.2012)

0.001 s
0.003 s
0.01 s
0.05 s

Explanation:

The delay period in a petrol engine is of the order of 0.002-0.003 s. Delay period is the time difference between injection of fuel and combustion.

The fluid drawn in during suction in petrol engine contains —-? (RRB Bangalore SSE 09.09.2012)

Fuel only
Fuel or air
Air only
Mixture of air and fuel

Explanation:

A petrol engine draws a mixture of petrol and air during the suction stroke.

Best fuel for S.I. engines is —-? (Konkan Railway STA 2017)

Aromatic
Naphthalene
Paraffins
Olefins

Explanation:

Best fuel for SI engines is Aromatic. For CI engines, normal paraffin is the best fuel.

The function of fuel pump in petrol engine is —-? (DMRC JE 20.04.2018)

Inject fuel in cylinder
Supply fuel when carburetor fail
Pump fuel to reach it in carburettor
None of these

Explanation:

The fuel pump in petrol engine is used to supply fuel to the carburettor.

The thermal efficiency of an ideal Otto cycle —-? (DMRC JE 2013)

Increases with compression ratio
Increases with specific heat ratio
Increases with compression ratio and specific heat ratio
Increases with compression ratio but decreases with specific heat ratio

Explanation:

Thermal efficiency of ideal Otto cycle increases with compression ratio and specific heat ratio.

Tetra ethyl lead in fuel is used to —-? (RRB Mumbai SSE 19.12.2010)

Increase the lubrication
Decrease octane number
Increase octane number
None of the above

Explanation:

TEL is used to increase octane number of gasoline. It acts as a negative catalyst, preventing fuel from burning too quickly.

Which one of the following governing method is used in petrol engines? (RRB Mumbai JE 05.01.2008) (RRB Mumbai SSE 05.10.2008)

Hit and Miss governing
Qualitative governing
Quantitative governing
Combination governing

Explanation:

Quantitative governing is used in petrol engines. Qualitative governing is used in diesel engines.

By applying choke in a petrol engine, the engine gets —-? (RRB Mumbai JE 05.10.2008)

Rich mixture
Rich mixture
Lean mixture
Proper mixture

Explanation:

By applying choke in a petrol engine, the engine gets a rich mixture (more fuel, less air) for cold starting.

A compression ignition engine is a —-? (RRB JE Jharkhand 2014)

Diesel engine
CNG engine
Steam engine
Petrol engine

Explanation:

A compression ignition engine is a diesel engine, while a spark ignition engine is a petrol engine.

The charge sucked in cylinder suction stroke of diesel engine is —-? (RRB Mumbai C&G JE 25.10.2009)

Diesel
Air
Diesel + Air
Diesel + Air + lubricating oil

Explanation:

The charge sucked in suction stroke of diesel engine is air. In petrol engine, it is air + fuel (carburetor mixture).

The compression ratio for a practical diesel engine usually lies in the range —-? (RRB Allahabad JE 19.12.2010) RRB Kolkata Technical-Engg., 20.08.2006

3-5
6-8
10-15
16-33

Explanation:

Compression ratio for practical diesel engine usually lies in the range 16-33. Petrol engine CR is approximately 6-10.

Fuel injector is used in —-? (RRB Patna JE 25.10.2009) RRB Chennai Technical (Eng.), 15.04.2007

steam engines
gas engines
spark ignition engines
compression ignition engines

Explanation:

Fuel injector is used in compression ignition engines (diesel). In spark ignition engines, carburetor is used for air-fuel mixture.

The knocking tendency in C.I. engines increases with —-? (BMRCL JE 24 Feb. 2019)

decrease of compression ratio
increase of compression ratio
increasing the temperature of inlet air
increasing cooling water temperature

Explanation:

Knocking tendency in CI engines increases with decrease in compression ratio. Low CR means insufficient temperature for ignition, causing fuel accumulation and explosive combustion.

Compression ratio for diesel engine may have a range of —-? (RRB SSE (Shift-I), 03.09.2015)

8 to 10
16 to 30
10 to 15
None of these

Explanation:

Diesel engine CR range: 16-30. Otto CR range: 6-12.

For diesel engine, the method of governing employed is —-? (RRB Mumbai JE 05.10.2008)

Quality governing
Quantity governing
Hit and miss governing
None of the above

Explanation:

Qualitative governing is used in diesel engines. Quantitative governing is used in petrol engines.

In a diesel engine, the fuel is ignited by —-? (RRB Mumbai SSE 19.12.2010)

Spark
Injected fuel
Heat resulting from compressing air that is supplied for combustion
Ignitor

Explanation:

In diesel engine, fuel is ignited by the heat resulting from compressing air supplied for combustion.

Anti knock property of C.I. engine fuel can be improved by adding —-? (Konkan Railway STA 2017)

Tetra-ethyl lead
Amyl nitrate
Hexadecane
Trimethyl pentane

Explanation:

Anti-knock property of CI engine fuel can be improved by adding amyl nitrate. Tetra ethyl lead is used to increase octane number of gasoline.

The injection pressure in diesel engine is of the order of —-? (RRB Mumbai C&G JE 25.10.2009)

30-40 bar
100-150 bar
200-300 bar
400-600 bar

Explanation:

During peak performance, fuel injection pressure can go up to 1600-1800 bar. It would be around 100-150 bar.

The function of fuel injector is to —-? (RRB Jammu JE 25.10.2009)

Pump the fuel at high pressure
Mix diesel with air
Atomise the fuel
Ignite the fuel

Explanation:

The function of fuel injector is to atomise the fuel and deliver it into engine cylinders with precise timing.

In diesel engine, the governor controls —-? (RRB Patna JE 25.10.2009)

Fuel pressure
Fuel volume
Fuel flow rate
Fuel temperature

Explanation:

In diesel engine, the governor controls fuel flow rate to maintain mean speed by controlling fuel supply.

The firing order for six cylinder diesel engine is —-? (RRB Allahabad SSE 09.09.2012)

1,3,5,3,4,6
1,5,3,6,2,4
1,4,3,6,3,5
1,6,3,5,3,4

Explanation:

The firing order for six cylinder diesel engine is 1,5,3,6,2,4.

The tendency of knocking in CI engines is reduced by —-? (RRB Kolkata SSE 09.09.2012)

high self-ignition temperature of fuel
decrease in jacket water temperature
injection of fuel just before TDC
decrease in injection temperature

Explanation:

Just before TDC, fuel is injected and atomised. If there is a longer delay period, fuel accumulates and knocking occurs.

In diesel engines, the duration between the time of injection and ignition, is known as —-? (RRB Bhopal SSE 09.09.2012)

Pre-ignition period
delay period
ignition period
burning period

Explanation:

Ignition delay period is the duration between injection and ignition. It can be subdivided into physical delay and chemical delay.

Self-ignition temperature of diesel as compared to petrol —-? (RRB Jammu SSE 09.09.2012)

is higher
is lower
is same
varies considerably

Explanation:

Self-ignition temperature of diesel as compared to petrol is lower.

Cetane number of petrol is around —-? (RRB Mumbai JE 19.12.2010)

10
15-20
30-35
55-70

Explanation:

Relationship between octane number and cetane number: CN = 60 – ON/2. For ON 85-90, CN is around 15-20.

Valve-overlapping happens —-? (Konkan Railway STA 2017)

Completely before TDC
Completely before TDC
Partially before TDC and partially after TDC
Completely before BDC

Explanation:

Valve overlap is the number of degrees of crankshaft rotation during which both valves are partially open before TDC and partially after TDC.

Which one of the following has zero cetane number? (RRB Mumbai C&G JE 25.10.2009)

α-methylnaphthalene
n-heptane
Tetra ethyl lead
Tri-methyl butane

Explanation:

α-methylnaphthalene has zero cetane number. If a fuel is equivalent to 85% cetane and 15% α-methylnaphthalene, cetane number is 85.

Cetane number is measure of —-? (RRB Jammu JE 25.10.2009)

Auto-ignition temperature
Viscosity of fuel
Calorific value of fuel
Ignition quality of fuel

Explanation:

Cetane number is measure of ignition quality of fuel. Higher cetane number results in quicker ignition.

In a diesel engine, the pipe carrying fuel from fuel pump to nozzle is made of —-? (JMRC JE 10.06.2017)

Plastic
P.V.C.
Steel
Aluminium

Explanation:

The pipe is made of steel to withstand high pressure (up to 150 MPa).

What could be the probable reason of power loss in a diesel engine? (BMRCL JE 24 Feb. 2019)

Clogging of air cleaner
Restricted exhaust
Low injection pressure
Ineffective cooling

Explanation:

Low injection pressure may cause power loss in a diesel engine.

A normal diesel engine will need minimum changes if made to run on —-? (RRB Allahabad JE 19.12.2010)

Petrol
Kerosene
Alcohol
Ammonia

Explanation:

Lower speed engines will do better on kerosene than modern high speed engines because historically diesel fuel specifications called for lower cetane.

Efficiency of IC engine is normally of the order of —-? (RRB Mumbai JE 05.10.2008)

15-30%
35-60%
35-30%
30-35%

Explanation:

Efficiency of IC engine is normally of the order of 30-35%.

Pressure in the fuel rail of CRDI diesel engine is approximately equal to —-? (RRB Allahabad JE 25.10.2009)

10 MPa
25 MPa
100 MPa
1000 MPa

Explanation:

CRDI (Common Rail Direct Injection) system has injection pressure over a range of 100-150 bar (approximately 100 MPa).

The correct sequence of combustion stages in C.I. Engine is —-? (RRB Patna JE 25.10.2009)

Ignition delay period → Controlled combustion → Uncontrolled combustion → After burning
Ignition delay period → After burning → Controlled combustion → Uncontrolled combustion
Ignition delay period → Uncontrolled combustion → After burning → Controlled combustion
Ignition delay period → Uncontrolled combustion → Controlled combustion → After burning

Explanation:

Correct sequence: Ignition delay period → Uncontrolled combustion → Controlled combustion → After burning.

During the combustion process in compression-ignition engines, increasing which parameter would increase the delay period? (RRB Allahabad SSE 09.09.2012)

Compression ratio
Intake temperature
Intake pressure
Injection advance angle

Explanation:

Delay period increases with increase in injection advance angle. With increase in injection angle, pressure and temperature are lower when injection begins.

In open-combustion chamber of a diesel engine —-? (RRB Bhopal SSE 09.09.2012)

Fuel injected into a separate turbulence chamber
Fuel injected in cavity provided at the top of piston
Partial combustion of fuel before main combustion chamber
Combustion of fuel takes place outside the cylinder

Explanation:

In the open combustion chamber, fuel is injected directly into space or cavity on top of the cylinder. It is suitable for slow-speed 4-stroke engines.

Pistons of diesel engine are usually cooled by —-? (RRB JE (Shift-2), 29.8.2015)

Air
Water
Lubricating oil
Fuel oil

Explanation:

Pistons of diesel engine are usually cooled by lubricating oil.

A four stroke diesel engine has —-? (RRB JE Bhopal Paper II (Shift-II), 26.08.2015)

One valve
Two valves
Three valves
Four valves

Explanation:

There are three types of valves in a diesel engine cylinder: inlet valve, exhaust valve, and injector valve.

The two reference fuels used for cetane rating are —-? (RRB JE (Shift-II), 29.8.2015)

Cetane and iso-octane
Cetane and tetraethyl lead
Cetane and n-heptane
Cetane and α-methyl naphthalene

Explanation:

The two reference fuels used for cetane rating are cetane and α-methyl naphthalene.

Which one of the following types of swirls is generated by a precombustion chamber in the diesel engine? (RRB JE (Shift-II), 16.09.2015)

Spanish
Compression swirl
Induction swirl
Combustion induced swirl

Explanation:

Precombustion chamber generates combustion induced swirl. Swirl chamber generates compression swirl.

The effectiveness of a fin will be maximum in an environment with —-? (RRB JE Bhopal Paper-I (Shift-II), 28.08.2015)

Free convection
Forced convection
Radiation
Convection and radiation

Explanation:

Effectiveness of fin will be more in free convection than forced convection because h_forced > h_free.

Which of the following characteristics does not belong to CI engine? (RRB SSE (Shift-III), 01.09.2015)

Self ignition temperature of its fuel is low
Its compression ratio is comparatively higher
They are low speed engine
They are light weight engine

Explanation:

CI engines are heavy weight engines due to high compression ratio requiring bigger flywheel.

Diesel cycle is —-? (RRB SSE (Shift-II), 01.09.2015)

Constant pressure heat addition cycle
Constant volume heat addition cycle
Constant temperature heat addition cycle
Constant entropy heat addition cycle

Explanation:

Diesel cycle is constant pressure heat addition and constant volume heat rejection cycle.

Presently the Emission Standards in force for 4-wheel petrol vehicles in Rajasthan are —-? (RRB Chandigarh SSE 09.09.2012)

Bharat Stage – I
Bharat Stage – II
Bharat Stage – III
Bharat Stage – IV

Explanation:

Presently the Emission Standards in force for 4-wheel petrol vehicles in Rajasthan are Bharat Stage – III.

Compression ratio in case of SI engine is in the range of —-? (RRB JE (Shift-3), 28.08.2015) (RRB JE Gorakhpur 2014)

6-10
10-15
16-25
25-40

Explanation:

Compression ratio in SI engine is in the range of 6-10. r_c = (V_c + V_s)/V_c.

An engine has a clearance volume of 100 cm³ and a swept volume of 800 cm³. The compression ratio is —-? (RRB Bangalore SSE 09.09.2012)

7:1
8:1
9:1
10:1

Explanation:

r_c = (V_c + V_s)/V_c = (100 + 800)/100 = 900/100 = 9:1.

Mean effective pressure of Otto cycle is —-? (RRB JE (Shift-3), 28.08.2015)

Inversely proportional to pressure ratio
Directly proportional to pressure ratio
Does not depend on pressure ratio
Proportional to square root of pressure ratio

Explanation:

Mean effective pressure of Otto cycle is directly proportional to pressure ratio.