The core of particle filter regeneration lies in particle oxidation, which requires high temperature, oxygen enrichment, and sufficient time. However, the exhaust temperature of diesel engines is usually below 500 ℃, especially for buses operating in urban conditions, where the exhaust temperature can even be below 300 ℃. Therefore, reducing the equilibrium temperature has become a key issue in the regeneration process. The equilibrium point temperature refers to the state where the particle formation and oxidation rates are equal, and the system is in equilibrium with a constant back pressure. However, reducing the equilibrium point temperature involves multiple factors, including flow rate, particulate composition, NOx content, sulfur concentration, soot formation, and the characteristics of the engine and fuel.

In order to achieve DPF regeneration, two methods are usually used: active regeneration and passive regeneration. In the active regeneration method, burner fuel injection heating regeneration is a common technique, which involves setting up a burner at the inlet of the particulate filter, injecting diesel and secondary air for combustion, and igniting the soot particles for regeneration. But this method requires providing additional fuel and controlling the burner temperature, while the vehicle needs to remain stable during the regeneration process, avoiding sudden acceleration and other operations to prevent extinguishing the regeneration flame.

Another active regeneration method is electric heating regeneration, which heats the particulate filter by passing electricity to promote the ignition of soot particles. Although this method has no smoking phenomenon, it requires high control system requirements and consumes a large amount of electricity, which may be difficult to meet the electricity demand for small and medium-sized diesel engines.

In addition, unevenness during the heating process may lead to uneven regeneration of the filter body, resulting in local overheating and damage to the filter body. Microwave heating regeneration technology utilizes the unique characteristics of microwaves, such as selective heating and volumetric heating, to form a heat source inside the filter body, efficiently heating the deposited soot particles and achieving in-situ ignition combustion. The frequency range of microwave heating is from 300 MHz to 300 GHz. It generates a heating effect in the electromagnetic field through dielectric loss, and energy is transmitted in the form of electromagnetic waves, which is closely related to the polarization of molecules inside the material.

The key to this technology lies in exciting multi-mode resonance within the resonant cavity and strictly controlling the combustion temperature of the soot particles inside the cavity to prevent overheating of the filter body. In contrast, infrared radiation heating regeneration has selective advantages, which can directly act on the heat receiving body, shorten the heating time, reduce energy consumption, and have high regeneration efficiency. The highest regeneration temperature is suitable, and it has little effect on the temperature gradient of the filter body, making it very suitable for the regeneration of honeycomb ceramics.

The mechanism of infrared radiation heating is that when the wavelength of the radiation source matches that of the object being radiated, the latter can efficiently absorb infrared energy, enhance molecular motion, and achieve rapid heating. Common passive regeneration methods include fuel additive catalysis, CRT (Continuous Regeneration Technology), and CCRT systems. Fuel additives, as catalysts dissolved in fuel, enter the exhaust after engine combustion and are captured by filters along with particles, reducing the regeneration temperature of particles. However, this additive may pose a risk to human health. The CRT system consists of an oxidizer and a particulate trap, without a catalytic coating, and achieves the conversion and removal of particles through physical interception and high-temperature oxidation.

Therefore, for diesel vehicles equipped with diesel particulate filters (DPF), it is crucial to choose low ash engine oil and regularly clean and regenerate the interior of the DPF. This not only ensures efficient conversion of DPF, reduces pollutant emissions, but also extends its service life, lowers maintenance costs, and reduces engine power loss and fuel consumption.