vehicle emissons measurement

Environment Department Environment Department

Vehicle Emissions Measurement

Andriannah Mbandi

Stockholm Environment Institute

University of York

Email: [email protected]

Environment Department

Agenda • Combustion process

• Combustion gases &

particulates

• Petrol or diesel?

• Units of measurement

• Vehicle emission

inventories

• World in-use and new

vehicle testing

• Conclusion


Combustion process

Oxygen

Nitrogen

Water Vapor

Fuel:

Petrol, Diesel


Combustion-air


Combustion process

Ideal Combustion λ = 1

Fuel

Fuel

Fuel

CO2

CO2

CO2

O2

O2

O2


Combustion process Lean Mixture λ > 1

Rich Mixture λ < 1

Fuel

Fuel

Fuel

CO2

CO2

CO2

O2

O2

O2

O2

O2 O2

O2

Fuel

Fuel

Fuel

CO2

CO2

O2

O2

Unburnt

Fuel

CO

O


Combustion gas: oxygen (O2)

• O2 levels inverse of CO levels-

without air injection system

• Lean Mixture: O2

• Rich Mixture: O2

• O2 content increases sharply

as λ>1

© http://www.youtube.com/watch?v=nIhDLnTGMAE


Combustion gas: carbon dioxide (CO2)

• Result of complete

combustion

• Overall combustion and

catalytic converter

efficiency

• Not a pass or fail gas

• CO2: 12-16%

© clickcarparts, 2014


Combustion gas: carbon monoxide (CO)

• Incomplete combustion

• Excess fuel = rich mixture

• Partially burnt fuel

• Catalytic converter requires air/fuel ratio to vary

lean to rich

Pre-catalytic converter: CO<1.5%

After catalytic converter: CO~0%

• Feedback carburetted ran rich at idle: CO~9%


Combustion gas: hydrocarbons (HC)

• Unburned fuel due to incomplete combustion

• All engines produce HC:

Pre-catalytic converter: 150-300 ppm

After catalytic converter: ~0 ppm

• Wasted fuel

1% partially burnt fuel produce 200 ppm HC


Combustion gas: oxides of nitrogen (NOX)

• Primary contributor of ozone

• Formed under high T & P: not formed at idle or

light loads

• Lean mixture at high T: excess O2 molecules

combine to form NOX

• Exhaust gas recirculation: O2 and T


Combustion gas: oxides of sulphur (SOX)

• High sulphur (S) content in fuel

Reduction in S

content reduces

emissions in

exhaust

Marine engines

have higher

contribution © Bilfinger, 2014


Combustion diagram for gases


Combustion particles-particulate matter (PM)

• Formed in combustion cylinder and in the exhaust

system of the vehicle.

• Mostly attributable to heavy duty diesel vehicles

Mix (condensed) liquid & solid-

Organic or Inorganic

• Sulphates

• Nitrates

• Ammonia

• Sodium chloride

• Black Carbon

• Mineral dust

• Water ©ARB, 2009


Petrol and Diesel Engines

Petrol Engine Diesel Engine

Spark Ignition Compression Ignition

Fuel/Air premixed before

compression

Fuel/Air not premixed

Lower efficiency & Lighter Higher efficiency-High

compression ratio & Heavier

AFR:14.7 (predetermined) AFR: 20-100/1 (air injected not

controlled)

Emissions: More fuel, >CO2,

less NOX and low PM

Emissions: less fuel, <CO2,

>NOX Higher PM

Pollutants: CO, HC, NOX Pollutants: NOX, PM


Units of measurement from the tail pipe of the

vehicle

Gases

O2: %

CO2: %

CO: %

HC: ppm

NOX: ppm

PM Particulate Mass (µg/m3)

Particulate Number (#/km)

Opacity: %

Smoke density: m-1


Vehicle emission inventories

𝐸𝑚𝑖𝑠𝑠𝑖𝑜𝑛𝑠 = 𝐸𝐹 𝑥 𝑉𝐾𝑇

𝑌𝑒𝑎𝑟

Units of emissions: g/year

EF: Emission factors (g/km)

VKT: Vehicle kilometres travelled

Inventories: SO2, NOX, CO, CO2, NMVOC, NH3,

PM10, PM2.5 , BC, OC and CH4.

© www.envirotest.co.za

http://www.envirotest.co.za/

http://www.envirotest.co.za/


World standards for in-use and new

vehicles: tail pipe emissions measurement

• California Air Resource Board (ARB)

• USA-Environmental Protection Agency (EPA)

• United Kingdom (UK)-Ministry of Transport

(MOT)


California Air Resources Board (ARB)

• Heavy-duty trucks and buses: control excessive smoke

emissions & prevent tampering (>6000lb)

• Test-Society of Automotive Engineers (SAE) J1667 snap

acceleration procedure-opacity measurement

• Test using PEMS

Periodic Smoke Inspection Program (PSIP)

Heavy-Duty Vehicle Inspection Program (HDVIP)

Allowable levels of Smoke Opacity

All post 1991 or newer engines Must not exceed 40% opacity

All pre-1991 engines Must not exceed 55% opacity


Snap acceleration (Free

acceleration Test): Opacity

SAEJ1667 snap acceleration:

• RPM recording (Idle/Max)

• Sensing probe inserted

• Driver accelerates 3 times with

transmission in neutral (to clear

loose particles) then repeat 3

times)

©Applus, 2009


US-EPA

• Inspection & maintenance (I/M) program with emissions

testing

• Test: IM 240

• Chassis dynamometer

I/M 240 driving schedule

Distance = 1.96 mile (3.1 km)

Average speed =29.4 mile/h

(47.3 km/h)

240 s test

Max speed = 56.7 mile/h

(91.2 km/h)


Chassis Dynamometer

• Simulate driving on a road

inside a laboratory under

controlled conditions.

IM240: 240-second transient

driving cycle: CO, HC,CO2,

and NOX determined g/mile

• Dynamometer's analyzers:

NDIR-CO/CO2

FID- HC

chemiluminescence-NOX

©Tuev & dieselnet, 2014


UK

• Petrol and diesel vehicles emissions testing

• Test-MOT

Test

(Petrol)

Type of Test Pass or Fail Age of

Vehicle

Visual

Inspection

Visual Black smoke/dense blue All

Standard

Emissions

Test

Gas Analyzer (non-

catalyst test)

CO :3.5%-4.5%

HC: 1200ppm

>1975

Basic

Emissions

Test

Gas Analyzer & EC Fast

Idle

Normal Idle

CO<0.2% HC<200ppm

0.97 < λ <1.03

CO <0.3%

>1992


MOT Testing centre

in UK

Tests:

• Visual inspection

• Standards

emissions test

• Basic Emission

Test Procedure

• Extended

emissions test

• Gases Test

(Petrol)

• Smoke Test

(Diesel)

©hicksmotandservice, 2014


New vehicles: use of PEMS to measure gases & PM

Exhaust sample

Heated sample line

GPS &

weather

probe

power supply 110

VAC, 220

VAC or 12 VDC

Exhaust

Flow

Meter

(EFM)

Weighing

Flow tube

Gas bench: CO/CO2 (NDIR)

NOx (NDUV), THC (FID)


Conclusion

• New technologies:

User friendly

Maintenance

Light

Robust

Precise

• Is it fit for purpose?

Vehicle fleet: age, technology

Fuel quality

R&D, vehicle manufacturers, Bureau of standards

© Nation, 2014

vehicle emissons measurement

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