Test
Auto Tech Part 1
Preguntas del test (42)
1A large We number indicates that the deforming aerodynamic forces are much larger than the reforming surface tension forces.
- AVerdadero
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2What do the terms dng and sg represent in the log-normal distribution?
- Adng is the number geometric mean dropsize and sg is the geometric standard deviation.
- Bdng is the mean diameter of a droplet and sg is the standard deviation.
- CThe terms have the same significance as the mean and standard deviation of a normal distribution function.
- Ddng is the mean number of droplets in a sample and sg is the standard deviation.
3What is the acronym SMD stand for?
- ASauter Mean Diameter
- BSpecimen Mean Diameter
- CSample Mean Diameter
4SMD describes the "average" diameter of an ensemble of droplets by weighting the average by both the surface area and the volume.
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5Why is SMD used to characterize droplet size?
- AEvaporation is a surface behavior.
- BThe local AFR is volume dependent.
- CIt explains the tendency of a spray to evaporate and form a particular AFR.
- DReflects the spread of fuel through mass weighting.
- EIt helps describe what happens to the droplets in theory.
- FIt helps describes what happens to the droplets in reality.
6What is the We number?
- AIt is a dimensionless number describing the ratio of deforming aerodynamic forces to the reforming surface tension forces.
- BIt is a dimensionless number describing the ratio of activation energy to thermal energy.
- CIt is a dimensionless number describing the ratio of inertial fluid forces to viscous fluid forces.
- AIt is a dimensionless number describing the ratio of deforming aerodynamic forces to the reforming surface tension forces.
7The log normal distribution for droplet size is given by this equation.
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8What is one key advantage of the log-normal distribution?
- AIt can be written such that there is a simple relationship between the surface and volume distributions.
- BIt can be written such that there is a simple relationship between the weight and area distributions.
- CIt can be written such that there is a simple relationship between the volume and diameter distributions.
9What are some dropsizing techniques?
- AMalvern Particle Sizer (MPS)
- BPhase Doppler Velocimetry
- CLaser Sheet Dropsizing
- DDynamic Light Scattering
- EDilute Solution Viscometry
- AMalvern Particle Sizer (MPS)
10The log normal distribution is used because it has been found experimentally to be a good fit for sprays.
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11What are some of the disadvantages of using PDV as a dropsizing technique?
- ALine of sight
- BPoint specific
- CVery expensive
- DLow spatial resolution
- ERequires a specific off axis forward scatter geometry
12I want to measure a dense spray. Which drop-sizing technique should I use?
- ALSD
- BPDV
- CMPS
13A "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.
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14The process that govern CO formation are .....
- A.....controlled by the mass of fuel burnt.
- B......kinetically controlled.
- C..... controlled through AFR.
15In the premixed flame, the CO concentration.....
- A...increases rapidly in the flame zone to a super equilibrium maximum.
- B....decreases slowly in the flame zone to a near zero state.
16The 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.
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17What are some mechanisms of HC formation?
- AIncomplete combustion or a misfire in a fraction of the engine cycles.
- BLean AFR resulting in knocking.
- CTrapping of unburnt mixture in crevices formed by the pistons and ring packs.
- DBurning a nitrogen rich fuel.
- EFlame quenching at the combustion wall.
18Combustion behavior is substantially controlled by the AFR. What is this?
- AIt is the mass ratio of air to fuel present in a combustion process.
- BIt is the ratio of actual air to the theoretical air required for the complete combustion of fuel.
- CIt 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.
19How is No emissions mainly formed?
- AIt is formed by the reaction of nitrogen and oxygen present in the combustion air.
- BIt is formed by the reaction of nitrogen and fuel present during the combustion.
20What are the pollutant emissions produced by a conventional gasoline engine?
- ACarbon Dioxide (CO2)
- BCarbon Monoxide (CO)
- CHydrocarbons (HC)
- DNitrogen Oxide (NOx)
- ESulphur Dioxide (SO2)
21The reactions to produce NO are very sensitive to temperature because the production of O atoms is essentially exponential with temperature.
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22How can the production of NOx be controlled or reduced?
- ACatalytic Abatement
- BLean burn operation for AFR 22:1
- CExcess air and exhaust gas recirculation
- DIncreasing or decreasing temperature of combustion
23What are some of the requirements for using catalytic abatement to reduce NOx?
- AIt needs an AFR of 14.5:1.
- BIt needs a specially designed engine.
- CIt needs a high temperature to function.
24In 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.
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25Increasing the AFR can significantly reduce the formation of CO and HC.
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26Ignition 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?
- A Cetane number
- BAFR
- CPressure
- DTemperature
- EFuel air mixing
- FSwept Volume
- GCalorific value of fuel (ie how much energy the fuel gives off when it burns)
27What happens when there is a long ignition delay period?
- AIt risks a large amount of mixture since the in-cylinder temperature will be low
- BThe larger part of premixed combustion may take place
- CIt leads to an increase in compression work (and thus reduces engine power output)
- DIt leads to an increase of soot formation because a proportion of fuel may remain unburnt
- EIt results in high engine temperatures and "knocking"
28The three distinct phases of combustion for a diesel engine are premixed combustion, mixing controlled combustion, and end-phase combustion.
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29Which phase of the combustion process in a diesel engine produces the most NO?
- APre-mixed combustion
- BMixing-controlled combustion
- CEnd phase combustion
30During which phase of combustion in a diesel engine is most of the soot formed?
- APre-mixed combustion
- BMixing-controlled combustion
- CEnd-phase combustion
31What is the break up time of spray?
- ADefined from the experimental results, it is the rate at which the spray tip penetration changes.
- BDefined from the theory of sprays, it is the rate at which the spray tip penetration changes.
- CIt is the rate at which a jet spray changes to a fully atomized spray.
32Advanced diesel combustion combines split injection strategies with catalytic abatement.
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33What is the prime parameter in determining the quantities of NOx formed in a traditional gasoline engine?
- AMass of fuel burnt
- BAFR
- CIncomplete combustion or misfires.
- DTemperature.
34 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) .
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35How does a split injection system (single pulse) help reduce smoke production?
- AIt minimizes rich and hot zones of combustion
- BIt reduces the combustion efficiency and lowers the amount of soot and smoke produced
- CIt maximizes the rich and hot zones of combustion
- DIt increases the combustion efficiency and lowers the amount of soot and smoke produced
36How does using EGR help with diesel combustion?
- AIt increases the heat capacity which reduces NOx
- BIt dilutes the combustion which reduces NOx
- CIt increases the overall efficiency
- DIt reduces the amount of smoke production
37What are some benefits of using high pressure injection in a DI Diesel Engine?
- AHigher pressures improve fuel customization and enhance fuel-air mixing
- BA smaller SMD (Resulting from high pressure) enhances the formation of fuel-air mixture in diffusion combustion phase
- CIt reduces both soot and NOx production.
38A 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.
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39How does lean burn increase bfsc?
- AIt decreases pumping losses
- BIt allows for more air to be drawn into the cylinder for a given amount of fuel
- CThere is less throttling
- DIt improves the overall efficiency
- EIt restricts the amount of air drawn into the cylinder for a given amount of fuel
- FThere is more throttling
40The 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.- AVerdadero
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41Fuel 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.- AVerdadero
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42How is the cone angle mainly affected?
- AGeometric characteristics of the nozzle
- BThe fuel and air density
- CReynolds number of the fuel
- DVelocity and Pressure of the fluid
- EChange of crank angle
Información
- Descripción
- Revision quiz for Automotive Technologies Exam
- Autor
- echowhiskey
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- English
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