Automotive Engine Auxiliary Systems Questions and Answers – Diesel Engine Fuel Supply System – Fuel Injector

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This set of Automotive Engine Design Assessment Questions and Answers focuses on “Diesel Engine Fuel Supply System – Fuel Injector”.

1. By adjusting which of the following we can vary the opening fuel line pressure?
a) Spring
b) Rocker arms
c) Rotor
d) Motor
View Answer

Answer: a
Explanation: The actual opening fuel- line pressure can be varied by adjusting the initial degree of spring compression. The fuel spray continues till the delivery from the injection pump is exhausted when the spring pressure again suddenly closes the nozzle valve back on its own.
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2. For what purpose a small quantity of fuel is purposely allowed to mean between the nozzle valve and its guide?
a) To control the temperature
b) To control the pressure
c) To lubricate
d) To keep a check-in entropy
View Answer

Answer: c
Explanation: A small quantity of fuel is purposely allowed to leak between the nozzle valve and its guide for lubrication purposes. The fuel accumulated around the spindle In this way is drained back to the fuel tank through the leak-off connection.

3. In which type of combustion chamber hole-type nozzle are preferred?
a) Pre-combustion
b) Open type
c) Both pre-combustion and self-cleaning
d) Self-cleaning
View Answer

Answer: b
Explanation: The nozzle used may be classified broadly into the hole type and the pintle type wherein the hole type nozzles are generally used in engines with the open type combustion chamber and the pintle type nozzle has an extension.
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4. What is the opening pressure range in MPa of a hole-type nozzle?
a) 5-7
b) 10-17
c) 17-34
d) 37-54
View Answer

Answer: c
Explanation: The opening pressure of the hole-type nozzle varies from 17 to 34MPa. Due to which the hole type fuel injector has good fuel atomization and this happens in a proper quantity. And the fuel is injected in the cylinder properly.

5. Which of the following is not a property of a good fuel injector?
a) Good atomization
b) Fuel uniformity
c) Faulty spraying
d) Proper injection angle
View Answer

Answer: d
Explanation: A good nozzle should atomize the fuel properly which is being supplied and it should also maintain the fuel uniformly and it also needs to maintain proper injection angle and proper direction of the fuel spray.
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6. What is the shape of the lower pintle end in a throttling pintle type?
a) Rectangle
b) Truncated cone
c) Sphere
d) Circle
View Answer

Answer: b
Explanation: The pintle type nozzle carries an extension, which produces a hollow cone-type spray. The pintle is much longer and is also shaped like a truncated cone at its lower end. Such shape causes only a small amount of the fuel to be injected at the ignition start.

7. What is the operating pressure in MPa of a pintle type nozzle?
a) 3-5
b) 5-7
c) 7-15
d) 17-25
View Answer

Answer: c
Explanation: In pintle type nozzle the rate of injection increasing gradually as the pintle: protrudes further from the nozzle end. The opening pressure of the pintle type nozzle varies from 7 to 15MPa which gives more fuel uniformity.
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8. In which type of combustion chamber pintle type nozzle injectors are preferred?
a) Pre – combustion
b) Open type
c) Self-cleaning
d) Both open type and self-cleaning
View Answer

Answer: a
Explanation: There are two types of nozzle mainly the hole type and the pintle type nozzle whereas the pintle type nozzle is preferred in common engines with pre-combustion chambers and some special swirl chambers.

9. What is the hole angle degree in an upward direction in a multi-hole nozzle?
a) 10
b) 15
c) 17
d) 20
View Answer

Answer: d
Explanation: In a multi-nozzle injector the nozzle consist of several holes bored in these tip of the nozzle. The number of while varies from 4 to 18 and the whole angle is about 20 degrees upwards.
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10. Which among the following is not a part of the injector?
a) Nozzle
b) Nozzle holder
c) Spark plug
d) Adjusting screw
View Answer

Answer: c
Explanation: The injector mainly consists of the nozzle, the.nozzle holder, the adjusting screw which is connected to the locking nut, spindle, valve, leak-off port, etc whereas there is no spark plug component in a fuel injector.

11. Which among the following is an advantage of the pintle type nozzle?
a) Self-cleaning
b) Uneven atomization
c) Different injection angle
d) Fault spraying
View Answer

Answer: a
Explanation: The pintle type of nozzle carries an extension, which produces a hollow cone-type spray. Such nozzle has the advantage of being self-cleaning and the advantage of a good nozzle is to atomize the fuel uniformly and to maintain proper injection angle and direction.

12. How much is the angle of spray cone in a single hole nozzle?
a) 10
b) 20
c) 15
d) 17
View Answer

Answer: c
Explanation: The single hole nozzle has a spray cone angle about 15 degrees and one of the major disadvantages of this nozzle is that they tend to dribble. Besides, their spray angle is too narrow to facilitate good mixing unless higher velocities are used.

13. What is the use of the additional hole present in a pintaux nozzle?
a) For self-cleaning
b) High-pressure relief
c) It injects a small amount of fuel
d) For temperature control
View Answer

Answer: c
Explanation: The function of the auxiliary hole drilled in the nozzle body is to inject a small amount of fuel through its addition hole which is called a pilot injection in an upstream direction slightly before the main injection.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter