Automotive Engine Design Assessment Questions and Answers 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
Answer: a
Clarification: 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.
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
Answer: c
Clarification: 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
Answer: b
Clarification: 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.
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
Answer: c
Clarification: 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
Answer: d
Clarification: 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.
6. What is the shape of the lower pintle end in a throttling pintle type?
a) Rectangle
b) Truncated cone
c) Sphere
d) Circle
Answer: b
Clarification: 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
Answer: c
Clarification: 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.
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