At the time of starting, idling and low speed operation, the carburretor supplies a mixture which can be termed as
Assertion (A): A simple carburettor which is set to give a correct mixture at low air speeds will give a progressively rich mixture as the air speed is increased.
Reason (R): As the pressure difference over the jet of a simple carburettor increases the weight of petrol discharge increases at a greater rate than does the air supply.
Ans. (a) Both A and R are true and R provides correct explanation for A
Match List I with List II and select the correct answer using the codes given below the lists :
Ans. (b) The idling system is used to compensate for dilution of charge, economizer is for meeting maximum power range of operation, acceleration pump for meeting rapid opening of throttle valve, and choke is used for cold starting.
Assertion (A): One of the important requirements of a carburettor is to supply leanmixture at starting.Reason (R): A rather lean mixture is required at No-load and low-load operation of a SI engine.
Ans. (d) At starting rich mixture is required
In some carburettor, meter rod and economiser device is used for
Ans. (c) An economizer is a valve which remains closed at normal speed and gets opened to supply enriched mixture at full throttle operation.
Consider the following statements:
1. Recycling exhaust gases with intake increases emission of oxides ofnitrogen from the engine.
2. When the carburettor throttle is suddenly opened, the fuel air mixtureleans out temporarily causing engine stall.
3. The effect of increase in altitude on carburettor is to enrich the entirepart-throttle operation.
4. Use of multiple venturi system makes it possible to obtain a high velocityair stream when the fuel is introduced at the main venturi throat.
Which of these statements are correct?
Consider the following statements regarding the advantages of fuel injection over carburetion in S.I. engines:
1. Higher power output and increased volumetric efficiency. [IES-2001]
2. Simple and inexpensive injection equipment.
3. Longer life of injection equipment.
4. Less knocking and reduced tendency for back-fire.
Select the correct answer using the codes given below:
Assertion (A): Air injection system finds wide application in modern diesel engines.Reason (R): Very good atomization of fuels is attained by the air injection system.
Ans. (a) Both A and R are correct and R is correct explanation of A.
Generally, in Bosch type fuel injection pumps, the quantity of fuel is increased or decreased with change in load, due to change in
Ans. (b) The quantity of fuel is varied by rotating helix on pump plunger, i.e. timing the end of fuel injection.
With increasing temperature of intake air, IC engine efficiency
In a variable speed S.I. engine, the maximum torque occurs at the maximum
Ans. (c) The torque developed by an engine is directly proportional to the indicated power.
Thus maximum torque will occur corresponding to maximum indicated power.
Consider the following statements:
I. The performance of an S.I. engine can be improved by increasing the compression ratio.
II. Fuels of higher octane number can be employed at higher compression ratio.Of these statements
Ans. (d) The performance of S.I. engine can't be improved by increasing the compression ratio because of pre-ignition and detonation.
Since high octane number tends to suppress detonation, t6 some extent fuels of higher octane number will be helpful at higher compression ratio.
The method of determination of indicated power of multi-cylinder SI engineis by the use of
Ans. (a) Morse test is used to determine indicated power of multi-cylinder S.I. engine
For a typical automobile C.I. engine, for conditions of increasing engine speed match List I with List II and select the correct answer using the codes given below the lists :
Keeping other parameters constant brake power of a diesel engine can be increased by
Ans. (c) Brake power of diesel engine can be increased by increasing pressure of intake air. Super charging.
Which one of the following quantities is assumed constant for an internal combustion engine while estimating its friction power by extrapolation through Willan's line?
Global warming is caused by
Ans. (b) carbon di-oxide acts as thermal shield to atmosphere.
Which one of the following set of materials is most commonly used in catalytic converters for CI engines?
Which one of the following cannot be controlled by a three-way catalytic converter?
With respect to I.C. engine emissions, consider the following statements:
1. Evaporative emissions have no carbon monoxide and oxides of nitrogen.
2. Blow by emissions is essentially carbon monoxide and suspended particulate matter.
3. Exhaust emissions contain 100% of carbon monoxide, 100% of oxides of nitrogen and around 50-55% of hydrocarbons emitted by the engine.
4. There are no suspended particulates in the exhaust.Of these statements are correct
Ans. (c) Evaporative emissions account for 15 to 25 per cent of total hydrocarbon emission from a gasoline engine. The two main sources of evaporative emissions are the fuel tank and the carburettor.