The automotive industry is very important because of its links to other sectors, such as steel, chemicals, textile, information and communication technology (ICT), repair and mobility services. Automotive industry also has a huge impact on employment and economy. On the other hand, it is also major pollution contributor. That is the reason why it is one of the most regulated industries in the world.
Gas monitoring techniques are widely used in the automotive industry for measuring vehicle emissions. Typical applications include live on-board exhaust monitoring (CO, CO2, N2O, NOx, formaldehyde, acetaldehyde, oxygen and moisture), analysis of raw and dilute exhaust gas from the engine and tailpipe with gas-bags (CO2, N2O, NOx, CH4, EtOH, THC, H2S, SO2, NH3, formaldehyde and acetaldehyde), diesel Selective Catalytic Reduction (SCR) after-treatment monitoring (NH3) and Sealed Housing for Evaporative Determination (SHED).
WHAT IS SHED (SEALED HOUSING FOR EVAPORATIVE DETERMINATION)?
In the automotive industry, regulatory requirements applying to qualification type testing procedures have been upgraded since the introduction of new gasoline mixes on the market. According to several industry codes and standards, evaporative losses from gas handling and storage system have to be tested and quantified for vehicle certification. Sealed Housing for Evaporative Determination (SHED) is used to measure evaporative emissions. Photoacoustic spectroscopy (PAS) is approved by US government as a measurement method for SHED (regulation 40 CFR Part 1065.269). Vehicle, engine, and fuel testing is an important way for EPA to verify emission standards are met.
WHAT TO MEASURE?
Components of interest are ethanol, methanol and refrigerant freons (R-134a and HFO-1234yf). For example, E10 gasoline (10% ethanol) is used, ethanol vapors escape from the tank and permeate through plastic materials (e.g., fuel tanks and fuel hoses). The US EPA prescribes a conservative 1.08 correction factor on conventional FID measurements to account for ethanol emissions. This is unless its vapor fraction is directly measured by advanced instruments. Ethanol is supervised by regulations due to toxicity to environment. Various methods are approved for the ethanol measurement (e.g. GC-FID or PTR-MS) but PAS is currently the most practical one.
Freons and methanol are measured for additional information. Methanol is leaking from windshield washing liquid container and freons from the refrigeration system. Performance of the conventionally used PAS analyzer only marginally meets the requirements. As emission levels drop, higher performance will be required from the PAS analyzer in the future.
GASERA ONE photoacoustic multi-gas analyzer unit was characterized against requirements for the SHED application in laboratory. GASERA ONE is extremely sensitive and highly linear. It outperforms the currently used conventional optical filter based PAS technique in terms of sensitivity and selectivity in the SHED application. As the measurement channels are chosen to minimize the effect of water and carbon dioxide, GASERA ONE performs well in the true SHED environment containing H2O and CO2.
The selectivity that GASERA ONE can achieve using a widely scanning high resolution laser is not possible with conventional infrared optical filter-based PAS analyzer. Ethanol, methanol and freons can be successfully and simultaneously distinguished from each other. Stabilization time for ethanol and methanol will be shortened as gas exchange is enhanced in future product versions. GASERA ONE is a potential new multi-gas analyzer to be used in the SHED application. Read more about GASERA ONE here.