Study of Gasoline Particulate Filter to Reduce Particulate Emissions from Spark Ignited Direct Injection Vehicle

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II METHOD

In the Second method, 2011 Hyundai Sonata SIDI vehicle with stoichiometric mixture and Volvo S40 PFI vehicle were used as the test vehicles. The specifications of both the test vehicles is shown in the table. 2 [Ref. 2]

Table. 2 Specifications of tested vehicles

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FTP-75 and US06 cycles were used for testing the vehicles so as to figure out the emissions at different conditions. The exhaust gases from both the vehicles undergoes the Constant Vehicle Sampling process whose setup is shown in fig. 3 [Ref. 2].

Fig. 3 Emission testing and sampling sytem setup

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RESULTS & DISCUSSIONS

I METHOD

To check the different parameter variability on GPF, various tests were carried out. When different material with different mean pore size (MPS) were tested, it was found that as the as the MPS decreases, filtration efficiency increases. [Ref. 1] because as the MPS decreases, particles with Nano size can be filtered more efficiently. It was also found that with the thick filter walls, filter efficiency and pressure drop can increase. Because it reduces the backpressure which declines the % of CO2 emissions [Ref. 5]. Moreover, due to low PN emissions in SIDI emissions, the wall gas velocity reduces resulting in better filtration efficiency [Ref. 1]. It is shown in following figures.

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Fig. 4 Impact of MPS on Filtration Efficiency

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Fig. 5 Impact of wall thickness on Pressure Drop

For analyzing the PM regeneration, NEDC cycle was selected. PM combustion was seen in a better way when decelerating the engine due to which presence of oxygen was seen.

II METHOD

Both the vehicles were tested and it was found that with GPF, a backpressure was formed which affects the CO and CO2 emissions. This results as reduction in fuel consumption in SIDI as compared to PFI by 6% and 3% with E0 as the fuel when GPF is not used (Stock SIDI) which increases marginally to 7% and 5% when E10 is used.

It was found that PN concentration for the stock SIDI and SIDI post GPF had similar pattern all over the LA4 cycle, though later one had less magnitude at some points which shows the effectiveness of GPF. In case of PFI, it had more PN concentration at cold start which reduces as the components warms up. But, in case of US06 cycle, it was found that filtration efficiency of GPF decreases as soot regeneration increases.

According to some studies, it was concluded that ethanol blends take more volume and time to generate same amount of energy as of gasoline fuels [Ref. 6, 7]. Due to this, wall wetting phenomenon comes into the play which could be possible reason for higher PM emissions for E10 as compared to E0.

Fig. 6 and 7 shows the particle size distribution of E0 and E10 fuels for SIDI and PFI vehicles over FTP-75 and US06. From the figures, it can be seen that stock SIDI and SIDI post GPF had the similar pattern of particle size distribution, although former had higher magnitudes because of the presence of cold start.

Fig. 6 Avg. PN size distributions for SIDI and PFI vehicles over FTP-75 cycle

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Fig.7 Avg. PN size distribution for SIDI and PFI vehicles over US06 cycle

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Nevertheless over US06 cycle, PFI vehicles shows a typical different variation than GDI vehicles in case of ultrafine particles because of their high speed. Accumulation of particles may be some of the outcome of the above variation which can affect the filtration efficiency of GPF.

When tested for PN emission rate, SIDI post GPF shows 20 – 30 % higher values than PFI in case of both E0 and E10 fuels. E0 shows the higher filtration efficiency than Ethanol Gasoline blend. FTP-75 cycle observed filtration efficiencies were more than the US06 cycle due to the particulate regeneration which decreases the PM layer in GPF.

CONCLUSIONS

In this era, all automobile manufacturers wants to make fuel efficient vehicles with lower CO2 emission limit. From both the methods, it can be concluded that CO2 emission rate and fuel consumption decreases for SIDI engine vehicles as compared to PFI, but at the cost of higher particulate emissions. To reduce this drawback, use of GPF as one of the measure comes into the play. Following is the overall summary of various conditions of GPF with different fuels (E0 and E10) and different engine system (SIDI and PFI).

By increasing the porosity and decreasing the pore size, increases the filtration efficiency of the GPF. Moreover, increasing the wall thickness and cell density affects the filtration efficiency and improves the pressure drop which reduces the backpressure to make vehicle more fuel efficient. PM regeneration can be seen at lower speed which reduces the filtration efficiency by reducing the PM layer formation in GPF.

GPF can reduce the Particulate emissions by 8 to 25 times than stock SIDI vehicles. Particle size mainly depend on the fuel injection strategies and timing for ethanol gasoline blend. Filtration efficiency decreases for ethanol gasoline blend fuel over US06 cycle than FTP-75 cycle due to presence of soot regeneration.

So, from the two method it can be concluded that GPF has the potential to effectively and reliably reduce particulate emissions over a wide range of operating points over different running drive cycles. The GPF is definitely one solution to reduce the harmful particle emissions and help to maintain the air clean.

REFERENCES

1. Saito, C., Nakatani, T., Miyairi, Y., Yuuki, K.et al., “New Particulate Filter Concept to Reduce Particle Number Emissions,” SAE Technical Paper 2011-01-0814, 2011, doi: 10.4271/2011-01-0814.

2. Chan W., Meloche, Kubsh , “Evaluation of a Gasoline Particulate Filter to Reduce Particle Emissions from a Gasoline Direct Injection Vehicle”, SAE Technical Paper 2012-01-1727, 2012, doi: 10.4271/2012-01-1727.

3. Piock, Hoffmann, Berndorfer.A, Salemi, Fusshoeller, “Strategies towards Meeting Future ParticulateMatter Emission Requirements in Homogeneous Gasoline