High-time resolution measurements of black carbon particles in the exhaust emissions of a diesel engine during acceleration, deceleration and cruise conditions

Abstract

Carbono negro (BC) é o componente principal de emissões de motores a diesel. Aethalometer ® foi usado nas medições das concentrações de BC (com resolução temporal de 5 s) emitido pelo escapamento de uma caminhonete tipo pick-up a diesel Dodge RAM 2500 1995 equipada com catalisador de oxidação. As medições foram feitas com um dinamômetro de chassis durante os modos de aceleração, desaceleração e de cruise (velocidade constante) do arranque a quente do ciclo de ensaio MEC01 (versão 7.0). Partículas de exaustão foram coletadas em paralelo nos filtros de fibra de quartzo para a medição de carbono elementar (EC) e carbono orgânico (OC) pelo método termo-óptico por reflectância (TOR), e em filtros de Teflon ® para determinação gravimétrica da massa total de partículas (PM). A rápida aceleração foi acompanhada por correspondentes aumentos nas emissões instantâneas de BC. Sob condições de aceleração totalmente aberta (WOT), a concentração de BC medida pelo Aethalometer ® atingiu um pico de 1,2 mg m -3 , mas reduziu a apenas 0,03 mg m -3 em condições cruise de 20 mph. Estes resultados mostram que é possível medir as emissões especiadas de material particulado de motores a diesel em tempo real em função da carga do motor e outras condições de funcionamento.Black carbon (BC) is a major constituent of diesel-engine exhaust emissions. Aethalometer ® was used in the measurements of the BC concentrations (with time resolution of 5 s) in the exhaust of a truck model 1995 Dodge RAM 2500 diesel pick-up equipped with an oxidation catalyst. The measurements were made from a chassis dynamometer during the acceleration, deceleration and cruise (constant speed) modes of the hot start of the MEC01 test cycle (version 7.0). Exhaust particles were collected in parallel on quartz fiber filters for elemental carbon (EC) and organic carbon (OC) measurement by the thermal-optical reflectance (TOR) method, and on Teflon ® filters for gravimetric total particle mass (PM). Rapid acceleration was accompanied by corresponding instantaneous increases in BC emissions. Under wide open throttle acceleration (WOT), Aethalometer ® BC concentrations peaked at 1.2 mg m -3 , but reduced to only 0.03 mg m -3 under cruise conditions at 20 mph. These results show that it is possible to measure speciated diesel particulate emissions essentially in real time as a function of engine load and other operating conditions. Keywords: high-time, black carbon, BC, diesel engine, exhaust emissions IntroductionCombustion-derived aerosol consists mainly of solid carbonaceous particles, including BC (black carbon), sometimes denoted EC (elemental carbon), and OC (organic carbon) that is associated with a complex mixture of toxic organic species. BC emissions contribute significantly to fine particle mass and are an important cause of atmospheric visibility impairment. They change the atmospheric radioactive balance and influence the nucleation and optical properties of clouds, leading to perturbation of rainfall and a very important component of the forcing for global cli...