3. Vehicles and Emission Standards

Question 1

What determines the total emissions in a city (how emissions are measured) and how can we control it?

Answer 1

1- Vehicle specific emissions
a) Emission value per km under different conditions. b) Specificforeachvehicletype/model.
 By determine Vehicles emissions standards
2- Fleet composition: Percentage of the vehicle classes/ types in the total vehicle fleet
 By incentive for vehicles renewal
3- Total vehicle usage
a) Total vehicle km driven
b) Generaldrivingbehavior
 By Transportation demand/traffic management

Question 2

What influences the specific emissions of a vehicle?

Answer 2

1- Vehicle related factors:
a) Fuel type b) Size of the motor
b) Weightofthevehicle c)Formofthevehicle(aerodynamics)
2- Situation and use:
a) Temperature of the motor
b) Drivingstate(accelerating,decelerating,cruising)
c) Speed of acceleration/ deceleration
d) Aggressive/adjusteddrivingstyle e)Inclineoftheroad

Question 3

What is the influence of the Electric vehicles for the emissions?

Answer 3

Local emissions of pollutants from an electric motor are zero. however, the overall emissions depend on other factors
1- All emissions come from electric energy production which use for Electrical Vehicles
2- PM emissions which has not yet been assessed reliably

Question 4

Why we cannot determine vehicle emissions by Standardized exhaust gas tests?

Answer 4

a) Motors behave differently under random every day conditions
b) Non-tailpipe emissions and indirect emissions do not get evaluated

Question 5

What are the Vehicle related measures for emission reduction?

Answer 5

1- Reduction of vehicle weight
a) Light composite materials
2- Reduction of resistance
a) Drag b) Rolling resistance
b) Increase of capacity with constant vehicle weight
3- Acceleration resistance
4- Increase of motor efficiency
5- Reduction of power loss through secondary aggregates
6- Assistance systems for adjusted driving
7- Exhaust gas treatment

Question 6

What are the differences between the NEDC and the FTB-75? Give a rough draw of the two cycles.

Answer 6

New European Driving Cycle (NEDC) 1997:
1- Test starts with a cold motor at
surrounding temperatures of 20-
30°C
2- The test bench has no incline
3- 4 urban driving cycles (UDC) in two
faces with Vmax=50 km/h
4- 1 extra-urban driving cycle (EUDC)
with aggressive driving behavior
and Vmax=120 km/h
5- Criticism: it fails to reflect realistic
driving behavior and
underestimates emissions
 Underestimation of NOx emissions by
266% compared to real driving
measurements were reported in 2017* USA: FTP-75
1- Cold start transient phase (ambient temperature 20-30°C), 0-505 s,
2- Stabilized phase, 506-1372 s,
3- Hot soak (min 540 s, max 660 s),
4- Hot start transient phase, 0-505 s
Emissions from each phase are collected in a separate Teflon bag, analyzed and expressed in (g/km).

Question 7

Why can’t Diesel and FSI engines perform the reduction of NOX. Which Catalyst is used in this case?

Answer 7

Diesel: Because, Exhaust gas of diesel motors contains surplus oxygen which inhibits the chemical reduction
FSI= Fuel Stratified Injection: Because, the residual NOx is stored in a substrate with catalytic metals -> The Best Catalyst is Selective Catalytic Reduction (SCR):
a) NOx in high oxygen exhaust gases get reduced by adding a reductant fluid (DEF Diesel Exhaust Fluid)
b) NOxgetsreducedtoN2andH2O
c) Efficiency of up to 90% reduction of NOx are possible by temperatures of over 200°C*