Auto Tech Part 1

echowhiskey
Quiz by echowhiskey, updated more than 1 year ago
echowhiskey
Created by echowhiskey almost 6 years ago
21
1

Description

Revision quiz for Automotive Technologies Exam

Resource summary

Question 1

Question
A large We number indicates that the deforming aerodynamic forces are much larger than the reforming surface tension forces.
Answer
  • True
  • False

Question 2

Question
What do the terms dng and sg represent in the log-normal distribution?
Answer
  • dng is the number geometric mean dropsize and sg is the geometric standard deviation.
  • dng is the mean diameter of a droplet and sg is the standard deviation.
  • The terms have the same significance as the mean and standard deviation of a normal distribution function.
  • dng is the mean number of droplets in a sample and sg is the standard deviation.

Question 3

Question
What is the acronym SMD stand for?
Answer
  • Sauter Mean Diameter
  • Specimen Mean Diameter
  • Sample Mean Diameter

Question 4

Question
SMD describes the "average" diameter of an ensemble of droplets by weighting the average by both the surface area and the volume.
Answer
  • True
  • False

Question 5

Question
Why is SMD used to characterize droplet size?
Answer
  • Evaporation is a surface behavior.
  • The local AFR is volume dependent.
  • It explains the tendency of a spray to evaporate and form a particular AFR.
  • Reflects the spread of fuel through mass weighting.
  • It helps describe what happens to the droplets in theory.
  • It helps describes what happens to the droplets in reality.

Question 6

Question
What is the We number?
Answer

Question 7

Question
The log normal distribution for droplet size is given by this equation.
Answer
  • True
  • False

Question 8

Question
What is one key advantage of the log-normal distribution?
Answer
  • It can be written such that there is a simple relationship between the surface and volume distributions.
  • It can be written such that there is a simple relationship between the weight and area distributions.
  • It can be written such that there is a simple relationship between the volume and diameter distributions.

Question 9

Question
What are some dropsizing techniques?
Answer

Question 10

Question
The log normal distribution is used because it has been found experimentally to be a good fit for sprays.
Answer
  • True
  • False

Question 11

Question
What are some of the disadvantages of using PDV as a dropsizing technique?
Answer
  • Line of sight
  • Point specific
  • Very expensive
  • Low spatial resolution
  • Requires a specific off axis forward scatter geometry

Question 12

Question
I want to measure a dense spray. Which drop-sizing technique should I use?
Answer
  • LSD
  • PDV
  • MPS

Question 13

Question
A "hollow core" or "air core" is formed by the swirl of the liquid.The tangential velocity of the outgoing liquid is given by two equations, relating the mass of liquid, the port area, and the chamber radius. At a radial position of r=0, the tangential velocity is equal to infinity. As this is impossible, a low pressure or vapor core is observed.
Answer
  • True
  • False

Question 14

Question
The process that govern CO formation are .....
Answer
  • .....controlled by the mass of fuel burnt.
  • ......kinetically controlled.
  • ..... controlled through AFR.

Question 15

Question
In the premixed flame, the CO concentration.....
Answer
  • ...increases rapidly in the flame zone to a super equilibrium maximum.
  • ....decreases slowly in the flame zone to a near zero state.

Question 16

Question
The Zeldovich mechanism is the mechanism that describes the formation of NO by breaking down O2 to O atoms and N2 to N atoms. The subsequent reactions produce NO.
Answer
  • True
  • False

Question 17

Question
What are some mechanisms of HC formation?
Answer
  • Incomplete combustion or a misfire in a fraction of the engine cycles.
  • Lean AFR resulting in knocking.
  • Trapping of unburnt mixture in crevices formed by the pistons and ring packs.
  • Burning a nitrogen rich fuel.
  • Flame quenching at the combustion wall.

Question 18

Question
Combustion behavior is substantially controlled by the AFR. What is this?
Answer
  • It is the mass ratio of air to fuel present in a combustion process.
  • It is the ratio of actual air to the theoretical air required for the complete combustion of fuel.
  • It is the ratio of the number of moles of fuel and air to the number of moles of fuel and air in a stoichiometric mixture.

Question 19

Question
How is No emissions mainly formed?
Answer
  • It is formed by the reaction of nitrogen and oxygen present in the combustion air.
  • It is formed by the reaction of nitrogen and fuel present during the combustion.

Question 20

Question
What are the pollutant emissions produced by a conventional gasoline engine?
Answer
  • Carbon Dioxide (CO2)
  • Carbon Monoxide (CO)
  • Hydrocarbons (HC)
  • Nitrogen Oxide (NOx)
  • Sulphur Dioxide (SO2)

Question 21

Question
The reactions to produce NO are very sensitive to temperature because the production of O atoms is essentially exponential with temperature.
Answer
  • True
  • False

Question 22

Question
How can the production of NOx be controlled or reduced?
Answer
  • Catalytic Abatement
  • Lean burn operation for AFR 22:1
  • Excess air and exhaust gas recirculation
  • Increasing or decreasing temperature of combustion

Question 23

Question
What are some of the requirements for using catalytic abatement to reduce NOx?
Answer
  • It needs an AFR of 14.5:1.
  • It needs a specially designed engine.
  • It needs a high temperature to function.

Question 24

Question
In order to reduce the production of NO, a lean burn operation is used. This requires a specifically designed engine where a port fuel injector is made through an open inlet valve.
Answer
  • True
  • False

Question 25

Question
Increasing the AFR can significantly reduce the formation of CO and HC.
Answer
  • True
  • False

Question 26

Question
Ignition delay period (or time) is the delay time between the start of injection and the start of combustion in a Diesel engine. What determines the delay time?
Answer
  • Cetane number
  • AFR
  • Pressure
  • Temperature
  • Fuel air mixing
  • Swept Volume
  • Calorific value of fuel (ie how much energy the fuel gives off when it burns)

Question 27

Question
What happens when there is a long ignition delay period?
Answer
  • It risks a large amount of mixture since the in-cylinder temperature will be low
  • The larger part of premixed combustion may take place
  • It leads to an increase in compression work (and thus reduces engine power output)
  • It leads to an increase of soot formation because a proportion of fuel may remain unburnt
  • It results in high engine temperatures and "knocking"

Question 28

Question
The three distinct phases of combustion for a diesel engine are premixed combustion, mixing controlled combustion, and end-phase combustion.
Answer
  • True
  • False

Question 29

Question
Which phase of the combustion process in a diesel engine produces the most NO?
Answer
  • Pre-mixed combustion
  • Mixing-controlled combustion
  • End phase combustion

Question 30

Question
During which phase of combustion in a diesel engine is most of the soot formed?
Answer
  • Pre-mixed combustion
  • Mixing-controlled combustion
  • End-phase combustion

Question 31

Question
What is the break up time of spray?
Answer
  • Defined from the experimental results, it is the rate at which the spray tip penetration changes.
  • Defined from the theory of sprays, it is the rate at which the spray tip penetration changes.
  • It is the rate at which a jet spray changes to a fully atomized spray.

Question 32

Question
Advanced diesel combustion combines split injection strategies with catalytic abatement.
Answer
  • True
  • False

Question 33

Question
What is the prime parameter in determining the quantities of NOx formed in a traditional gasoline engine?
Answer
  • Mass of fuel burnt
  • AFR
  • Incomplete combustion or misfires.
  • Temperature.

Question 34

Question
A "split injection" system allows the rich zone of the fuel to be significantly reduced whilst maintaining flexibility with engine load (eg the amount of fuel injected) .
Answer
  • True
  • False

Question 35

Question
How does a split injection system (single pulse) help reduce smoke production?
Answer
  • It minimizes rich and hot zones of combustion
  • It reduces the combustion efficiency and lowers the amount of soot and smoke produced
  • It maximizes the rich and hot zones of combustion
  • It increases the combustion efficiency and lowers the amount of soot and smoke produced

Question 36

Question
How does using EGR help with diesel combustion?
Answer
  • It increases the heat capacity which reduces NOx
  • It dilutes the combustion which reduces NOx
  • It increases the overall efficiency
  • It reduces the amount of smoke production

Question 37

Question
What are some benefits of using high pressure injection in a DI Diesel Engine?
Answer
  • Higher pressures improve fuel customization and enhance fuel-air mixing
  • A smaller SMD (Resulting from high pressure) enhances the formation of fuel-air mixture in diffusion combustion phase
  • It reduces both soot and NOx production.

Question 38

Question
A DIG achieves a lean burn by manipulating a rich region to the spark plug by controlling the timing and form of injection in conjunction with the in-cylinder air flow.
Answer
  • True
  • False

Question 39

Question
How does lean burn increase bfsc?
Answer
  • It decreases pumping losses
  • It allows for more air to be drawn into the cylinder for a given amount of fuel
  • There is less throttling
  • It improves the overall efficiency
  • It restricts the amount of air drawn into the cylinder for a given amount of fuel
  • There is more throttling

Question 40

Question
The cone angle is defined as the angle between two straight lines originating from the orifice exit of the nozzle and being tangent to the spray outline. This angle usually ranges from 5 to 30 degrees.
Answer
  • True
  • False

Question 41

Question
Fuel spray tip penetration is defined as the maximal distance measured from the injector to the spray tip. It represents the maximum penetration length achieved by the droplets in the center of the spray.
Answer
  • True
  • False

Question 42

Question
How is the cone angle mainly affected?
Answer
  • Geometric characteristics of the nozzle
  • The fuel and air density
  • Reynolds number of the fuel
  • Velocity and Pressure of the fluid
  • Change of crank angle
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