Effect of Operating and Sampling Conditions on the Exhaust Gas Composition of Small-Scale Power Generators

Small stationary diesel engines, like in generator sets, have limited emission control measures and are therefore responsible for 44% of the particulate matter (PM) emissions in the United States. The diesel exhaust composition depends on operating conditions of the combustion engine. Furthermore, the measurements are influenced by the used sampling method. This study examines the effect of engine loading and exhaust gas dilution on the composition of small-scale power generators. These generators are used in different operating conditions than road-transport vehicles, resulting in different emission characteristics. Experimental data were obtained for gaseous volatile organic compounds (VOC) and PM mass concentration, elemental composition and nitrate content. The exhaust composition depends on load condition because of its effect on fuel consumption, engine wear and combustion temperature. Higher load conditions result in lower PM concentration and sharper edged particles with larger aerodynamic diameters. A positive correlation with load condition was found for K, Ca, Sr, Mn, Cu, Zn and Pb adsorbed on PM, elements that originate from lubricating oil or engine corrosion. The nitrate concentration decreases at higher load conditions, due to enhanced nitrate dissociation to gaseous NO at higher engine temperatures. Dilution on the other hand decreases PM and nitrate concentration and increases gaseous VOC and adsorbed metal content. In conclusion, these data show that operating and sampling conditions have a major effect on the exhaust gas composition of small-scale diesel generators. Therefore, care must be taken when designing new experiments or comparing literature results

Mean VOC concentration in the exhaust gas.

<p>Mean VOC concentration in the exhaust gas.</p

Chemical analysis of the undiluted samples with EDXRF and IC (± S.E.).

<p>Chemical analysis of the undiluted samples with EDXRF and IC (± S.E.).</p

Properties of Gasoil extra.

<p>Properties of Gasoil extra.</p

PM mass concentrations (± standard error) determined by the gravimetric method (A) and with the DustTrak (B).

<p>PM mass concentrations (± standard error) determined by the gravimetric method (A) and with the DustTrak (B).</p

SEM pictures of PM collected at different load conditions of the diesel engine.

<p>The SEM picture of stage 2 is 10 000 times zoomed in, for stage 4 the enlargement is 1000 times.</p

Iron (A), lead (B), sulfur (C) and nitrate (D) concentration on PM (± S.E.) for different load conditions and dilution ratios.

<p>Iron (A), lead (B), sulfur (C) and nitrate (D) concentration on PM (± S.E.) for different load conditions and dilution ratios.</p

Relative abundance of alkanes and aromatic VOCs in the gas phase.

<p>Relative abundance of alkanes and aromatic VOCs in the gas phase.</p