Unit 1 Equipment and its Operation

(Answers to exercises)

Exercise 1.1.1A

1. By the opening of the exhaust valve towards the end of
the power stroke.

2. It uses the energy to drive a turbine wheel.

3. It propels a centrifugal compressor wheel. It takes
place at the same time as the turbine wheel is driven.

4. Yes. The turbochargers can extract the wasted energy up
to one third.

5. The manifolds back-pressure may be increased and this
makes it difficult for each successive burnt charge to be expelled from the
cylinders.

6. It impedes the clearing process in the cylinders in the
exhaust stroke.

Exercise 1.1.1B

1. It comes from the opening of the exhaust valve and the
expansion of the gas down to atmospheric pressure.

2. It could cause detonation in petrol engines.

3. By reducing the engines compression ratio by a factor
of one or two.

4. They are 10:1 and 16:1 respectively.

5. When it uses much higher supercharged inlet pressures.

Exercise 1.1.1C

1. The centrifugal fore effect which increases with the
square of the rotational speed of the impellor wheel.

2. When there is light load and low engine speed
conditions.

3. There will be very little extra boost pressure to make
any marked improvement to the engine torque and power output.

4. The torque and power outputs and fuel consumption values
of the turbocharged engine are smaller than the naturally aspirated engine.

5. It happens when the engine is suddenly accelerated. It
means effective pressure will be rather sluggish.

Exercise 1.1.2A Compressor

It is made from aluminum alloy.

It looks like a disc mounted on a hub.

Its components are radial blades projected from one side.

It is placed on a hub that is curved.

Its step of operation are:

1.      Air enters the cell.

2.      The enclosed air is divided up by the passage way.

3.      The flow path moves through a right angle

4.      Air is expelled radially from the cells.

5.      Air reaches the periphery and passes to parallel
diffuser.

6.      Air flows into circular volute-shaped collector.

Exercise 1.1.2B Turbine

1. High-temperature heat-resistant nickel-based alloy such
as Inconel and ceramic materials such as sintered silicon nitride

2. It is like a hub.

3. A hub      4. A disc     5. Radial blades

6. Exhaust gases enter housing flange.

7. Gases flow around volute passageway surrounding turbine
wheel.

8. Gases are forced tangentially inwards from the throat of
turbine housing.

9. Gases impinge onto the blade faces.

10. Flow path directs the gases through a right angle.

11. Gases come out axially from the center of turbine
wheel.

12. Gases are expelled into the exhaust pipe system.

Exercise 1.1.2C Spindle

1. Medium carbon steel

2. Two piston rings at the turbine wheel end

3. One piston ring next to the compressor wheel

4. It is supported on a pair of free-floating phosphorus
bronze plain bearings.

5. The spindle rotates.

6. Oil from the end of the bearing spills into the cavity
and drains to the exit funnel.

7. The oil deflector shields the bearing oil spray from the
piston rings, and the oil drains down to bearing housing exit.

8. Exhaust gas impinges onto the turbine wheel.

9. Compressed air react on compressor wheel, producing end
thrust as the spindle moves axially first in one direction and then in the
other.

1.1.3A

1 are joined     2 is    3 are brought    4 is generated   
5 is    6 is stopped   

7 is increased    8 are broken up    9 (is) removed    10
are then ground

Exercise 1.1.3A

1. The friction welding solid phase technique

2. By the increase of the end force

3. The surface films and inclusions might interfere with
the formation of bonds.

    They can be broken up by friction and removed from the
weld area.

4. By grinding the burrs surrounding the joint

1.1.3B

1 is provided    2 is sandwiched    3 is attached    4
forms   

5 is created    6 is enclosed    7 is located    8 provides 
  9 insulates

10 are supplied    11 can be established

12 incorporates    13 is made

Exercise 1.1.3B

1. Heat transference from the turbine-wheel exhaust gas
flow path to the bearing housing

2. By the large air gap or air space created between the
turbine wheel and the bearing housing. This provides an effective heat barrier.

3. To lubricate the bearings and to remove excess heat from
the bearing assembly.

Exercise 1.1.4A

3. Force produces radial outward motion to air.

4. Air velocity and pressure is greater.

5. Air moves out from center of rotation.

6. It moves through diverging passages to periphery.

8. More air is drawn into inducer, generating slight
depression.

9. Continuous supply of fresh charge is encouraged.

10. Kinetic energy at entrance is partially converted into
pressure energy.

11. Air leaving diffuser is collected in volute.

12. Volute prevents air becoming congested.

Exercise 1.1.4B

2. It is directed tangentially inwards through throats of
turbine housing.

3. Released gas kinetic energy impinges on turbine-blades,
imparting energy to turbine wheel.

5. Its flow path moves through right-angle.

6. It passes axially along hub.

7. It leaves turbine housing.

8. Expansion of gas ejected from turbine-wheel produces
sudden drop in velocity and pressure as it enters silencer pipe system.

Exercise 1.2.1 (Please instruct the students to
underline the parts that are changed. Tell them to underline in the examination
also for ease of marking.)

1. Small direct-injection semi-open combustion
chambers

            The present generation of car high-speed
direct-injection diesel engines is designed to reach speeds up to 4500 rev/min
with low emission exhaust gas products.

             With the conventional semi-open chamber the
fuel is injected directly into the cylinder where it is distributed and
mixed within 30˚ to 45˚ crank-angle movement at the end of the compression
stroke and the beginning of the power stroke.

            This is achieved with the direct-injection
engine. A moderate amount of rotational swirl and a large amount of
compression squish are promoted and combined to produce a toroidal swirl
pattern within the piston bowl.

2. Small direct-injection semi-open combustion
chambers (Continued)

            The extra air movement has been achieved
by utilizing a helical vortex form of induction port passage, where the
incoming are flow is given a helical twist motion about the valve stem
before it passes out between the opened valve head and its seat in a tangential
direction to the cylinder axis. As a result, a high degree of air swirl is
generated within the curved port passage before it is expelled into
the cylinder.

            To match the increased in organized air
movement, the fuel injection pump camshaft has been strengthened and modified
to raise the rate of injection and correspondingly to shorten the duration in
which fuel is discharged into the cylinder, thus giving more time for
mixing and combustion. At the same time, injection timing has been designed
to be valuable and precise so that it rapidly responds to the changes in
operating conditions of the engine.

3. Viscous friction Lanchester-type vibration
damper

            This form of damper comprises a multi-plate
clutch attached between a hub and a ring mass spacer. There are two sets of
friction disc plates: the drive plates which are internally splined to
the hub and the driven plates externally splined to the inertia ring mass. The clutch pack is held together by side-plates which are bolted on
either side to the ring mass spacer. The friction discs are lightly squeezed
together by six evenly spaced coil springs. Oil is supplied from the
crankshaft front main bearing and this way the friction discs are submerged
in lubricant.

4. Separate System

In this system the foul water
is conveyed in one pipe to the sewage treatment works and all the surface
water is conveyed in another pipe completely independently of the foul water;
thus there is no need for water treatment. Connections to surface water
drains do not need (are not needed) to be trapped because there should be no
unhealthy smells, but with the foul water drain, all connections must be
trapped. One problem with this system is the danger of cross-connections,
i.e. foul water that is connected to a surface water drain.

Exercise 1.2.3

1. The turbocharged engine may have torque and power
outputs that are inferior to the unsupercharged engine.

2. The pressure in the exhaust manifold that impinges
onto the turbine wheel remains substantially the same.

3. The impellor compressor wheel is an aluminum alloy
casting which takes the form of a disc.

4. The devices which step up or down the voltage from an
a.c. supply are called transformer.

    The devices which are called transformer step up
or down the voltage from an a.c. supply.

5. The cleaners sink which has a protective strip
is provided with a hinged metal grating.

    The cleaners sink which is provided with a hinged
metal grating has a protective strip.

6. Foul water is water that is contaminated by soil,
waste and trade effluent.

7. The grease converter allows the effluent to pass over a
series of baffles which cause the grease to form in globules on the surface.

8. A design of outlet which allows for an internal
downpipe is sometimes necessary.

9. For joints that run in the same direction as the flow
of water, standing seams are used.

10. The fuel that flows through the metering slits
will produce a drop in fuel pressure on its way out.

Exercise 1.2.4

1. The extra energy discharged into the turbine housing
volute can speed up the turbine wheel.

2. With the engine operating at high altitudes,
there will still be some power loss.

3. Air enters the cells formed between adjacent pairs of
blades.

4. The energy contained by the air cannot be
destroyed.

5. The impellor is cast with blades forming the walls of
the cells.

6. The air flinging out at the rim of the impellor
enters the scroll where it is diffused

7. When the air flowing through the impellor radial
cells reaches the periphery of the blades, it will have attained a very high
velocity.

8. The diffuser consists of an annular ring with vanes positioned tangentially around one side.

9. The air leaving the impellor and passing through the
parallel diffuser will reduce its speed.

10. Each of the two volute passages commences feeding into
a common throat completely surrounding the circumference of the turbine wheel.

11. The gas had a tendency to reverse its flow out due to
the centrifugal force exceeding the inward pulse thrust.

12. The center of each countershaft has skewed helical
teeth machined around it.

13. When a valve attached to an armature is
energized, it will open.

14. Most baths commonly installed today are made
from acrylic materials.

15. Any foul matter adhering to the insides of pipes
soon dried and was washed away.