# A Study on the Impact of DPF Failure on Diesel Vehicles Emissions of Particulate Matter
## 3 Results
### Results of Emission Particle Number Concentration by DPF Damage Type  
Figures 6 and 7 show the graphs reflecting the average of the measured number of PN per unit volume, measured 10 times in the KD-147 driving mode with DPF samples installed in the experimental vehicle. Overall, the PM concentration increased rapidly when the experimental vehicle accelerated in the KD-147 driving mode, and it decreased when the engine was not loaded during vehicle deceleration or vehicle movement at constant speed. The maximum PM concentration was obtained in the rapid acceleration section of 70-80 s in the KD-147 driving mode. For the normal DPF, the maximum measured value of PN was approximately 1.5 \(\times\) 10\({}^{5}\) particle/cm\({}^{3}\), and the average PN value measured over 147 s was approximately 3.5 \(\times\) 10\({}^{4}\) particle/cm\({}^{3}\). For the cracked DPF, the maximum measured PN value was approximately 2.9 \(\times\) 10\({}^{6}\) particle/cm\({}^{3}\), and the average PN value measured over 147 s was approximately 7.8 \(\times\) 10\({}^{5}\) particle/cm\({}^{3}\). The maximum measured PN value was approximately 22 times higher than that of the normal DPF. This was attributed to the fact that the light transmission method of the smoke concentration meter was unable to measure the ultra-fine particles emitted from the crack gap. For the melt-damaged DPF, the maximum measured PN value was approximately 5.2 \(\times\) 10\({}^{7}\) particle/cm\({}^{3}\), and the average PN value measured over 147 s was approximately 2.7 \(\times\) 10\({}^{7}\) particle/cm\({}^{3}\). This result was attributed to the fact that the substrate channel inside the DPF had melted and moved to the channel without a plug, and PM was discharged in the absence of the filtering function. For the hollow DPF, the maximum measured PN value was approximately 7.1 \(\times\) 10\({}^{7}\) particle/cm\({}^{3}\), and the average PN value measured over 147 s was approximately 3.0 \(\times\) 10\({}^{7}\) particle/cm\({}^{3}\). This result was attributed to the fact that the central part of the DPF substrate was completely hollowed out, and it was unable to perform the filtering function properly.  
Figure 5: Smoke concentration averaged over 10 repetitions of exhaust test using samples with various types of DPF damage.  
For the plug DPF, the maximum measured PN value was approximately \(5.8\times 10^{7}\) particle/cm\({}^{3}\), and the average PN value measured over 147 s was approximately \(2.5\times 10^{7}\) particle/cm\({}^{3}\). This result was attributed to damage to the plug that filtered the PM, which decreased the PM reduction efficiency. In this study, DPF samples corresponding to each damage type were mounted on a test vehicle, and KD-147 driving mode tests were conducted to determine the particle concentration emitted during vehicle driving. The results confirmed that all damaged DPFs did not satisfy the PN regulations for operative vehicles in the European Union. Notably, the normal filter did satisfy these regulations. A correlation between the DPF failure type and the effluent concentration was not identified.  
Figure 6: Average particle number in concentration measurements of normal and crack-damaged DPF samples.  
Figure 7: Average particle number in concentration measurements of DPF samples.