Vehicle Emissions Measurement Andriannah Mbandi Stockholm Environment Institute University of York Email: andriannah.mbandi@york.ac.uk 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 Environment Department Combustion process Fuel: Oxygen Nitrogen Water Vapor Petrol, Diesel Environment Department Combustion-air Environment Department Combustion process Ideal Combustion λ = 1 O2 Fuel O2 Fuel CO2 CO2 Fuel CO2 O2 Environment Department Combustion process Lean Mixture λ > 1 O2 O2 O2 CO2 Fuel CO2 Fuel Fuel O2 CO2 O2 O2 O2 Rich Mixture λ < 1 CO2 Fuel O2 Fuel Fuel CO O Unburnt Fuel CO2 O2 Environment Department Combustion gas: oxygen (O2) • O2 levels inverse of CO levelswithout air injection system • Lean Mixture: O2 • Rich Mixture: O2 • O2 content increases sharply as λ>1 © http://www.youtube.com/watch?v=nIhDLnTGMAE Environment Department 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 Environment Department 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% Environment Department 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 Environment Department 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 Environment Department 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 Environment Department Combustion diagram for gases Environment Department Combustion particles-particulate matter (PM) • Formed in combustion cylinder and in the exhaust system of the vehicle. • Mostly attributable to heavy duty diesel vehicles ©ARB, 2009 Mix (condensed) liquid & solidOrganic or Inorganic • Sulphates • Nitrates • Ammonia • Sodium chloride • Black Carbon • Mineral dust • Water Environment Department Petrol and Diesel Engines Petrol Engine Diesel Engine Spark Ignition Compression Ignition Fuel/Air premixed before compression Lower efficiency & Lighter Fuel/Air not premixed AFR:14.7 (predetermined) Emissions: More fuel, >CO2, less NOX and low PM AFR: 20-100/1 (air injected not controlled) Emissions: less fuel, <CO2, >NOX Higher PM Pollutants: CO, HC, NOX Pollutants: NOX, PM Higher efficiency-High compression ratio & Heavier Environment Department Environment Department 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 Environment Department Vehicle emission inventories 𝑉𝐾𝑇 𝐸𝑚𝑖𝑠𝑠𝑖𝑜𝑛𝑠 = 𝐸𝐹 𝑥 𝑌𝑒𝑎𝑟 Units of emissions: g/year EF: Emission factors (g/km) VKT: Vehicle kilometres travelled © www.envirotest.co.za Inventories: SO2, NOX, CO, CO2, NMVOC, NH3, PM10, PM2.5 , BC, OC and CH4. Environment Department 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) Environment Department 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 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   Periodic Smoke Inspection Program (PSIP) Heavy-Duty Vehicle Inspection Program (HDVIP) Environment Department 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 Environment Department US-EPA • Inspection & maintenance (I/M) program with emissions testing • Test: IM 240 • Chassis dynamometer  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) I/M 240 driving schedule Environment Department 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 Environment Department 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 (noncatalyst test) CO :3.5%-4.5% HC: 1200ppm >1975 Basic Emissions Test Gas Analyzer & EC Fast Idle CO<0.2% HC<200ppm 0.97 < λ <1.03 Normal Idle >1992 CO <0.3% Environment Department 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 Environment Department Emission legislations complexity © AVL, 2014 Environment Department New vehicles: use of PEMS to measure gases & PM GPS & weather probe Exhaust Flow Meter (EFM) Weighing Flow tube Heated sample line Gas bench: CO/CO2 (NDIR) NOx (NDUV), THC (FID) power supply 110 VAC, 220 VAC or 12 VDC Exhaust sample Environment Department 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 Environment Department