CN107100704A - Anti-leak and jamproof radio frequency cut-off ring suitable for DPF radio-frequency measurements - Google Patents

Abstract

The invention relates to a radio frequency cut-off ring suitable for anti-leakage and anti-interference in DPF radio frequency measurement. The radio frequency cut-off ring includes a metal plate, and the metal plate is respectively arranged on the two sections of the DPF cavity and the intake pipe and the exhaust pipe. At the joint, a plurality of through holes are uniformly distributed on the ring surface of the metal disc; the joint between the metal disc and the DPF cavity is connected by multi-point brazing. The present invention welds a metal plate with a plurality of through holes at the joints of the cavity and the two sections of the intake pipe and the exhaust pipe, and prevents the internally measured radio frequency signal from being disturbed on the premise of improving the distribution of the flow field in the cavity. Leakage and interference of external radio frequency signals are beneficial to further promote the method of radio frequency measurement to market applications.

Description

RF cut-off ring suitable for anti-leakage and anti-interference in DPF RF measurement

technical field

The invention relates to an auxiliary device of a particle trap, in particular to a radio frequency cut-off ring suitable for anti-leakage and anti-interference in DPF radio frequency measurement.

Background technique

Diesel engine exhaust contains a large amount of inhalable particulate matter, which is harmful to human health. According to the newly released National V emission standards, there are strict requirements for the quality (PM) and number (PN) of particulate matter. Heavy-duty diesel vehicles generally need to use particle capture to meet emission regulations. Collector (DPF). The DPF achieves the purpose of cleaning by trapping the particulate matter in the exhaust on the wall of the filter body, but when the particulate matter accumulates to a certain extent, it will cause the DPF to be blocked, cause the exhaust back pressure to increase, and the fuel economy of the engine to decrease, etc. Therefore, it is necessary to make the DPF work under the best working conditions through periodic regeneration. When the carbon load reaches the regeneration setting limit, regeneration needs to be started, so accurately judging the carbon load in the DPF is an important prerequisite for regeneration.

The new technology at this stage uses radio frequency means for measurement. However, in the actual measurement process, due to the huge hole in the connection between the DPF and the inlet and outlet exhaust pipes, it is easy to cause leakage of radio frequency signals and external interference to affect the measurement, but the added structure at the connection will be to a certain extent It affects the flow field distribution of the cavity, resulting in a decrease in the collection effect of the filter body. Only by effectively solving this problem can the method of radio frequency measurement be further promoted to market applications.

Contents of the invention

For the possible impact of external radio frequency signals during the process of monitoring carbon load by radio frequency technology to achieve accurate DPF regeneration, and for the inaccurate measurement results caused by radio frequency signal leakage during the measurement process of monitoring carbon load by radio frequency technology to achieve accurate regeneration of DPF The invention provides a radio frequency cut-off ring suitable for anti-leakage and anti-interference in DPF radio frequency measurement.

A radio frequency cut-off ring suitable for anti-leakage and anti-interference in DPF radio frequency measurement, the radio frequency cut-off ring includes metal discs, and the metal discs are respectively arranged at the joints of the DPF cavity and the two sections of the intake pipe and the exhaust pipe, A plurality of through holes are evenly distributed on the ring surface of the metal disk.

Preferably, the connection between the metal disc and the DPF cavity is connected by multi-point brazing.

Preferably, the metal discs are respectively fixed at positions 10 mm inside the connecting section of the DPF cavity and the exhaust pipe connecting section of the inlet and outlet pipes. It can effectively prevent the occurrence of microwave leakage affecting the resonance phenomenon caused by the too large diameter of the exhaust gas connecting pipe, and also ensure that the exhaust gas can flow smoothly into the cavity.

Preferably, the metal disc has a diameter of 22-35mm.

Preferably, several first through holes with a diameter of 4 to 12 mm are evenly distributed on the ring surface of the metal disk, and several second through holes with a diameter of 3 to 9 mm are evenly distributed on the ring surface with a diameter of 8 to 12 mm. hole.

Preferably, the metal disc has a thickness of 6-10 mm.

As a preference, eight-point welding is used at the connection between the metal plate and the DPF cavity, and the welding points are evenly distributed. Can effectively prevent gap leakage.

Preferably, the metal disk has a diameter of 28mm.

Preferably, eight first through holes with a diameter of 8mm are evenly distributed on the ring surface of the metal disk, and four second through holes with a diameter of 6mm are evenly distributed on the ring surface with a diameter of 10mm.

Preferably, the thickness of the metal disk is 8mm.

The present invention welds a metal plate with a plurality of through holes at the joints of the cavity and the two sections of the intake pipe and the exhaust pipe, and prevents the internal measurement of the radio frequency signal on the premise of improving the distribution of the flow field in the cavity. Leakage and interference of external radio frequency signals are beneficial to further promote the method of radio frequency measurement to market applications.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is the structural representation that the present invention is arranged;

Fig. 3 is the distribution figure of the axial velocity that has radio frequency cut-off ring in the embodiment 1 of the present invention;

Fig. 4 is the distribution diagram of the axial velocity without radio frequency cut-off ring in embodiment 1 of the present invention;

Fig. 5 is the distribution diagram of the axial velocity after the through-hole enlargement in embodiment 2 of the present invention;

Fig. 6 is a distribution diagram of the axial velocity after the through hole is reduced in embodiment 3 of the present invention.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

Example 1

Referring to Fig. 1 and Fig. 2, a radio frequency cut-off ring suitable for anti-leakage and anti-interference in DPF radio frequency measurement, the radio frequency cut-off ring includes a metal disc 1, and the metal discs are respectively arranged on the DPF cavity 2 and the intake pipe 3 At the junction with the two sections of the exhaust pipe 4, a plurality of through holes are evenly distributed on the ring surface of the metal disk 1. The diameter of the metal disk 1 is 28mm, eight first through holes 5 with a diameter of 8mm are evenly distributed on the ring surface of the metal disk, and four second through holes 5 with a diameter of 6mm are evenly distributed on the ring surface with a diameter of 10mm. The through hole 6; the thickness of the metal disk 1 is 8mm.

The metal plate 1 and the DPF cavity 2 are connected by eight-point welding, and the welding spots are evenly distributed, which can effectively prevent the gap from leaking. The metal discs are respectively fixed at 10 mm in the connection section between the DPF cavity and the exhaust pipes of the inlet and outlet pipes. The setting of this position can effectively prevent the occurrence of microwave leakage affecting the resonance phenomenon caused by the too large diameter of the exhaust pipe. In addition, it also ensures that the exhaust gas can smoothly flow into the cavity.

Through simulation, it is found that the frequency of the microwave used by the device of the present invention is greater than 2 GHz, and the corresponding wavelength is 50 mm. And when the aperture is smaller than 1/4 wavelength, microwaves will not leak. In addition, through hydrodynamic analysis, the flow field of the cavity can be improved after adding a radio frequency cut-off ring.

Flow field improvement effect:

The magnetic field simulation simulation of the radio frequency cut-off ring under the cavity flow field is carried out by Fluent fluid mechanics simulation software, thereby verifying the effect of the present invention on improving the cavity flow field.

Generally speaking, the exhaust gas inlet velocity of the diesel vehicle particle filter changes with the change of the diesel engine operating conditions. When the diesel engine speed changes between 800r/min and 3000r/min, the exhaust gas inlet velocity of the particle filter is 20m/min s to 90m/s. So we choose 20m/s, 50m/s, 80m/s three kinds of exhaust velocity as representatives for research. The angle is the expansion angle, and A represents the calculation section. Since our PDF cavity is a rotating body, we intercept a section A along the axis for fluid dynamics simulation.

Under the condition that the expansion angle is 90°, compare the axial direction on the A section at three speeds of 20m/s, 50m/s, and 80m/s with the radio frequency stop ring cavity and without the radio frequency stop ring cavity in this embodiment. The distribution of speed, the results are shown in Figure 3 and Figure 4. It can be clearly seen from the figure that after the RF cut-off ring is added, the velocity in section A is relatively uniform, and does not change much with the radial position, so the addition of the RF cut-off ring can improve the flow field distribution in the cavity to a certain extent , so that the exhaust gas entering the filter body is more uniform.

Anti-leak effect:

In order to ensure that the signal will not leak during the measurement process, a radio frequency leak detection experiment was carried out. According to theory, when the microwave frequency used is greater than 2GHz, the corresponding wavelength of 2GHz is 50mm. When the aperture is smaller than 1/4 wavelength, microwaves will not leak, so when measuring leakage, we only need to ensure that the frequency band with the lowest frequency will not leak.

We place a radio frequency source with a power of 17.5dBm and a frequency of 2GHz in the cavity and outside the cavity, measure the energy received by the source and the receiving point at a distance of 1cm, 10cm and 50cm, and judge the RF cut-off ring The ratio of barrier energy, the results are shown in Table 1:

Table 1

Note: The source receives the energy received by the antenna inside the cavity and the source receives the energy received by the antenna outside the cavity after subtracting the background radiation energy/mW

It can be seen from Table 1 that the proportion of radio frequency signal energy leaked out by the present invention is no more than 0.01%, basically negligible; it shows that the present invention can effectively prevent the leakage of radio frequency signal energy.

Anti-interference effect:

In order to ensure that the present invention can effectively prevent measurement inaccuracy caused by energy attenuation caused by leakage. The anti-interference effect was tested. We used the device to measure the carbon load with radio frequency, and placed the radio frequency source with a power of 17.5dBm and a frequency of 1.75GHz to 2.0GHz outside the cavity. The distance from the radio frequency cut-off ring At 1cm, observe whether the measurement results are affected during the measurement process, the results are shown in Table 2:

Table 2

It can be seen from Table 2 that although the measured image is changing as the frequency of the external interference radio frequency source changes, the resonant frequency peak we selected for measurement has not changed, and only the intensity of the received amplitude has changed. Weak, so our cavity will not be affected in the frequency band of 1.8-2GHz.

Example 2

The influence of RF cut-off rings with different size designs on the flow field is compared, and the influence of changing the diameter of different through-holes on the flow field distribution is compared when the number of designed through-holes is fixed. Under the condition that the expansion angle is 90°, the diameter of the first through hole of the radio frequency cut-off ring is 9mm, and the diameter of the second through hole is 7mm. , 80m/s three speed distribution of axial velocity on section A, the results are shown in Figure 5. It can be clearly seen from Fig. 5 that after the RF cut-off ring is added, the velocity in section A is relatively uniform, but after the size of the through-hole increases, compared with the condition of the through-hole aperture in Example 1, the radial position The change is large, so the RF cut-off ring after the through-hole size is increased can improve the flow field distribution in the cavity to a certain extent, but it also has a certain impact on the flow field distribution.

Example 3

The influence of RF cut-off rings with different size designs on the flow field is compared, and the influence of changing the diameter of different through-holes on the flow field distribution is compared when the number of designed through-holes is fixed. Under the condition that the expansion angle is 90°, the diameter of the first through hole of the radio frequency cut-off ring is 5mm, and the diameter of the second through hole is 3mm. , 80m/s three speed distribution of axial velocity on section A, the results are shown in Figure 6. It can be seen from Figure 6 that the smaller size of the through hole will make the exhaust gas entering the filter body in the cavity more uniform, but the reduction of the size of the through hole will lead to excessive peaks in the flow field distribution on both sides, and the flow field distribution will also appear A certain degree of turmoil is achieved, and at the same time, the flow resistance is increased to a certain extent.

Claims (10)

1. A radio frequency cut-off ring suitable for anti-leakage and anti-interference in DPF radio frequency measurement, characterized in that: the radio frequency cut-off ring comprises a metal disc, and the metal disc is respectively arranged on the DPF cavity and the intake pipe and the exhaust pipe At the junction of the two sections, a plurality of through holes are evenly distributed on the ring surface of the metal disc. 2. The RF cut-off ring suitable for anti-leakage and anti-interference in DPF radio frequency measurement according to claim 1, characterized in that: the connection between the metal plate and the DPF cavity is connected by multi-point brazing. 3. The radio frequency cut-off ring suitable for anti-leakage and anti-interference in DPF radio frequency measurement according to claim 1, characterized in that: the metal discs are respectively fixed in the connecting section of the tail gas connection between the DPF cavity and the inlet and outlet pipes The position at 10mm. 4. The radio frequency cut-off ring suitable for anti-leakage and anti-interference in DPF radio frequency measurement according to claim 1, characterized in that: the diameter of the metal disc is 22-35 mm. 5. The radio frequency cut-off ring suitable for anti-leakage and anti-interference in DPF radio frequency measurement according to claim 1, characterized in that: several first pass rings with a diameter of 4 to 12 mm are evenly distributed on the metal disk ring surface. For the hole, several second through holes with a diameter of 3-9 mm are evenly distributed on the ring surface with a diameter of 8-12 mm. 6 . The radio frequency cut-off ring suitable for anti-leakage and anti-interference in DPF radio frequency measurement according to claim 1 , characterized in that: the thickness of the metal disc is 6-10 mm. 7. The RF cut-off ring suitable for anti-leakage and anti-interference in DPF radio frequency measurement according to claim 2, characterized in that: the connection between the metal plate and the DPF cavity adopts eight-point welding, and the welding points are evenly distributed. 8. The radio frequency cut-off ring suitable for leakage prevention and anti-interference in DPF radio frequency measurement according to claim 4, characterized in that: the diameter of the metal disc is 28 mm. 9. The radio frequency cut-off ring suitable for anti-leakage and anti-interference in DPF radio frequency measurement according to claim 8 is characterized in that: eight first through holes with a diameter of 8mm are evenly distributed on the metal disk ring surface, Four second through holes with a diameter of 6 mm are evenly distributed on the ring surface with a diameter of 10 mm. 10. The radio frequency cut-off ring suitable for anti-leakage and anti-interference in DPF radio frequency measurement according to claim 9, characterized in that: the thickness of the metal disc is 8mm.