JB/T 5141-1991 Design parameters of small gasoline engine exhaust muffler
Some standard content:
Mechanical Industry Standard of the People's Republic of China
JB/T 5141-1991
Design parameters of exhaust mufflers for small gasoline enginesPublished on 1991-06-26
Standards Download Network of Ministry of Machinery and Electronics Industry of the People's Republic of China (www.bzxzw.com)
Implementation on 1992-07-01
Mechanical Industry Standard of the People's Republic of China
Design parameters of exhaust mufflers for small gasoline enginesSubject content and scope of application
JB/T 5141-1991
This standard is suitable for the selection and design of exhaust mufflers for gasoline engines with a power of less than 30kW and a cylinder diameter not exceeding 75mm. Reference standards
GB4759
JB5137
Measuring methods for exhaust silencers of internal combustion engines
Technical conditions for exhaust silencers of small gasoline engines Evaluation indicators, classifications, models of silencers
The main indicators for the selection, design and evaluation of silencer series are insertion loss D, power loss ratio, volume ratio and processability. 3.1
The definition and measurement method of the insertion loss D and power loss ratio r of silencers shall comply with the relevant provisions of GB4759. The volume ratio of silencers is defined as the ratio of the effective volume V. of silencers (excluding the inlet and exhaust pipes) to the total displacement V of gasoline engines, that is, V./V. The process and structural characteristics of silencers shall comply with the relevant provisions of JB5137. Classification and indicators of mufflers
According to the matching use of mufflers and main engines, mufflers are divided into four categories: 3.2.1
Applicable to gasoline engines for portable machinery;
Applicable to gasoline engines for general machinery;
Applicable to gasoline engines for machinery requiring low noise;
Applicable to gasoline engines for motorcycles.
The indicators of various types of mufflers should be in accordance with the provisions of Table 1. Table 1
Muffler category
3.3 Indication method of muffler model
Indication method of muffler model
Approved by the Ministry of Machinery and Electronics Industry on June 26, 1991 Loss D
dB (A)
Loss ratio r
Muffler structure model, according to Articles 6.1 to 6.4 of this standard Gasoline engine model
Implementation on July 1, 1992
Standard Download Network (www.bzxzw.com)
Marking example: 175F-B-2
JB/T 51411991
refers to the muffler being matched with the 175F gasoline engine, suitable for general supporting machinery, and having the structure of Figure 71E40F-C-3 in Article 6.2
refers to the muffler being matched with the 1E40F gasoline engine, suitable for supporting equipment requiring low noise, and having the structure of Figure 13 in Article 6.3.3.2
In addition to the name and model, the muffler nameplate or manual shall also indicate the main indicators of the muffler, and the content of the marking shall include:
dB (A)
4 Exhaust silencer characteristics
4.1 The exhaust noise of a small gasoline engine is a wide-band noise, and its frequency characteristics are mainly determined by the speed, displacement, number of cylinders and other parameters of the gasoline engine. Its main peak frequency components are periodic exhaust noise and cylinder resonance noise. For multi-cylinder gasoline engines, the exhaust noise is mainly periodic exhaust noise; for single-cylinder gasoline engines, the main noise is cylinder internal resonance noise. The muffler design should be based on this. 4.2 Periodic exhaust noise includes gasoline engine ignition frequency components and their higher harmonics. Its fundamental frequency can be calculated using formula (1): =
Where: f—frequency, Hz;
gasoline engine speed, r/min;
number of cylinders;
stroke coefficient, four-stroke gasoline engine = 2, two-stroke gasoline engine: = 1. 4.3 Cylinder resonance noise is generated by the combustion gas exciting the internal resonance of the cylinder. Its fundamental frequency can be calculated using formula (2): f.
Where:
frequency, Hz;
sound speed in the exhaust pipe, cm/s;
—total displacement, L;
1 exhaust pipe length, cm;
So—average exhaust port area, cm2.
5 Muffler design parameters
5.1 Effective volume of muffler V
1000V1+
The effective volume of the muffler directly affects its muffler performance and power loss. The reasonable effective volume of the muffler should be selected according to the displacement, speed, number of cylinders, number of strokes and the indicators to be achieved by the muffler. The effective volume of different types of mufflers can be estimated according to formula (3): V.=K,K, K, K, V
In the formula: V.
Effective volume of the muffler;
V—total displacement of the gasoline engine;
Correction value of the number of cylinders; K=（）-1;
JB/T51411991
Correction coefficient of the number of strokes of the gasoline engine, K=2 for two-stroke gasoline engine, K=1 for four-stroke gasoline engine;-Correction coefficient of the type of muffler, the correction coefficients of different types of mufflers are shown in Table 2: K
Muffler type
Correction coefficient of gasoline engine speed, which can be calculated by formula (4): K=0.7+10-*n
np gasoline engine rated speed, r/min.
Due to the difference in the design structure of the muffler, the selected muffler volume can deviate from the value calculated by formula (3) by ±20%. 5.2 Aspect ratio and expansion ratio of silencer
5.2.1 Aspect ratio of silencer
For the same volume silencer, when the aspect ratio is different, it will affect the insertion loss and power loss of the silencer. If the aspect ratio of the silencer is too large, its acoustic characteristics are closer to the expansion chamber silencer, but its expansion is relatively small and the sound attenuation value is low; if the aspect ratio is too small, its acoustic characteristics are closer to the volume resonance silencer, and the effective sound attenuation frequency range is narrow. Therefore, the aspect ratio of the silencer should be selected appropriately. The aspect ratio of the silencer is defined as the ratio of the silencer length L to the silencer equivalent diameter D. The optimal aspect ratio can be selected according to Table 3. Table 3
Silencer category
Aspect ratio (LDa)
The equivalent diameter of the non-circular silencer is calculated using formula (5): Where: S—silencer cross-sectional area.
The selection of the aspect ratio of the muffler should also take into account the rationality of the overall layout of the gasoline engine. 5.2.2 Muffler expansion ratio
Miniature gasoline engine exhaust mufflers mostly use a combination of simple expansion chamber muffler units of multiple sections and different forms. The insertion loss values of different types of simple expansion chamber muffler units can be calculated according to formula (6) when there is no airflow influence: D=L.Lm
Where: D
Insertion loss value, dB;
L.=20lglcoskl,l+20lglsinkl,l+20lgGL.=20lglcoskl1
I\—Exhaust pipe length without muffler;wwW.bzxz.Net
1}, 13—Exhaust pipe length before and after the muffler; k=2 wave number;
Wavelength;
The values of different types of mufflers are shown in Table 4. (6)
Silencer unit shape
JB/T51411991
2+201gsink2
2+6+20lgsin-
2 +12 +201gsin-
+20lg/cos
2+12+201gsin-
The maximum insertion loss of each type of expansion chamber silencer is determined by the expansion ratio m=S./St, and its value is 20lgm. The expansion ratio of different types of small gasoline engine silencers can adopt the values given in Table 5. Table 5
Silencer category
Expansion ratio m
When the volume of the silencer is constant, its aspect ratio and expansion ratio have a certain relationship. When selecting design parameters, both should be taken into consideration. 5.2.3 Due to the volume limitation of the muffler and the influence of oil and carbon deposits, it is generally not recommended to use resistive muffler units and resonant muffler units in the muffler of small gasoline engines. If the volume allows or there are special requirements, the above two muffler units can also be used in part of the volume by taking certain measures.
5.3 Number of muffler cavities and volume distribution
JB/T5141-1991
Mufflers for small gasoline engines generally use a combination of multi-section expansion chamber mufflers. The number of cavities selected should be determined according to the required insertion loss and power loss. If the number of cavities is too small, the insertion loss is low; if the number of cavities is too large, the insertion loss may not be significantly improved, but the power loss may increase. Therefore, the number of cavities should be selected appropriately. The number of cavities of different types of mufflers can be selected according to Table 6. Table 6
Muffler categories
After the number of cavities is determined, the volume distribution ratio of each cavity is also very important. In order to ensure that the muffler has a muffler effect in a wider frequency band, the size of each cavity should be selected differently. Experiments have shown that the first cavity uses the largest volume, which is conducive to reducing airflow pulsation and back pressure. To a certain extent, it can improve the muffler effect and reduce power loss. For A, B, and C type mufflers, the volume of the first chamber should not be less than 1 to 3 times the engine displacement. For D type mufflers used in two-stroke gasoline engines, the first chamber should generally be designed as an exhaust boost chamber to increase the power of the gasoline engine. The total length of the exhaust pipe and the first chamber can be calculated according to formula (7): va
wherein: nmax
the maximum power speed of the gasoline engine, r/min;
α——the opening angle of the scavenging port;
Vthe pressure wave propagation speed in the gasoline engine exhaust pipe, generally 450~550m/s. 5.4 Muffler air flow velocity and exhaust port area 5.4.1 Muffler inlet area S,
The muffler inlet area is determined according to the exhaust port size of the gasoline engine: single-cylinder two-stroke gasoline engine: S,=(1.2~1.5)Sa; single-cylinder four-stroke gasoline engine; S,=So;
multi-cylinder gasoline engine: S,=exhaust manifold outlet area. (7)
S. of a single-cylinder two-stroke gasoline engine is the cross-sectional area of the cylinder exhaust port, and S. of a single-cylinder four-stroke gasoline engine is the cross-sectional area of the cylinder or cylinder head exhaust duct outlet. The exhaust of both types is appropriately expanded from the cylinder to the muffler inlet to reduce the exhaust gas flow velocity. For a multi-cylinder gasoline engine, since the exhaust phases of each cylinder are staggered, the exhaust manifold outlet area is usually slightly larger than the exhaust duct outlet cross-sectional area of each cylinder. 5.4.2 Gas flow velocity in the muffler
The average gas flow velocity in the muffler should not exceed the value given in Table 7. Table 7
Muffler beauty
Resistance muffler
Impedance muffler
Selection of perforated plate and inner tube parameters
Upper limit of flow rate
The perforation area of the perforated plate and the cross-sectional area of the inner tube should generally be close to the cross-sectional area of the muffler inlet. As the number of cavities increases, the flow area of each cavity behind can be gradually reduced, but it must not be lower than the outlet cross-sectional area of the muffler. 5
JB/T 51411991
Using perforated plates and tubes with small apertures and a large number of perforations can help reduce low-frequency sound, but considering the manufacturing process and preventing the holes from being blocked by carbon deposits, the aperture is generally selected in the range of 5~8mm.
5.4.4 Exhaust port area of muffler
The exhaust port area of muffler can be calculated by formula (8): S,=10K,V,K
Exhaust port area of muffler, cm2;
Where: S—
Total displacement of gasoline engine, I;
Correction coefficient of gasoline engine stroke number, two-stroke gasoline engine K=2, four-stroke gasoline engine K,=1; K,—Correction coefficient of gasoline engine speed, K,=0.7+10-n; np
Rated speed of gasoline engine, r/min.
5.5 Length of muffler tail pipe
The length of muffler tail pipe has a certain influence on the muffler characteristics and power loss of muffler. The relationship between the tail pipe length and the volume resonance frequency of the muffler is:
Where: o
muffler volume resonance frequency, Hz;
sound velocity in the muffler, cm/s;
Ss—muffler tail pipe cross-sectional area, cm;
l——muffler tail pipe length, cm;
V.—muffler effective volume, L.
1000V. (+ sign)
Theoretical and practical proofs show that as the exhaust tail pipe length increases, the effective lower limit cutoff frequency of the muffler moves toward low frequency, which can significantly increase the insertion loss value of the muffler, especially the insertion loss value in the low and medium frequency range. The influence of the tail pipe length on the power characteristics is mainly reflected in the influence of the tail pipe reflected pressure wave. The test results show that when the tail pipe is at a specific length, it has the best power characteristics. When designing the muffler, the tail pipe length should be appropriately lengthened under the conditions allowed by the gasoline engine and the supporting equipment. The optimal tail pipe length should take into account both insertion loss and power loss, and is determined by a gasoline engine bench test. Muffler structure
This chapter recommends some typical muffler structures that can achieve the indicators in Chapter 2 according to the design parameters in Chapter 5. The recommended structure is the acoustic design structure of the muffler. The specific dimensions of the muffler and its components can be determined based on this design parameter and test; its structural design can be selected by the production unit according to the structure in 6.1~6.4 according to the actual requirements of the product. 6.1A series muffler structure: See Figure 1~Figure 5. Figure 1A-1 Internally inserted tube type two-chamber structure
JB/T5141-1991
Figure 2A-2 Perforated plate type two-chamber structure
Figure 3A-3 Perforated plate type reflux two-chamber structure
Figure 4A-4 Internally inserted tube type three-chamber structure
Figure 5A-5 Perforated plate type three-chamber structure
6.2B series muffler structure: see Figures 6 to 10. Figure 6B-1 Internally inserted tube type three-chamber structure
Figure 7B-2 Perforated plate type three-chamber structure
Figure 8B-3 Internally inserted tube and perforated plate type reflux three-chamber structure7
JB/T5141-1991
Figure 9B-4 Internally inserted tube and perforated plate type reflux three-chamber structure main
Figure 10B-5 Internally inserted tube type four-chamber structure
6.3 Structure of C series muffler: see Figures 11 to 15 . 1
C-1 Internal insert pipe and perforated plate type reflux four-chamber structure Figure 12
C-2 Internal insert pipe and perforated plate type reflux four-chamber structure C-3 Internal insert pipe and perforated plate type reflux four-chamber structure Figure 14C-4 Internal insert pipe type reflux four-chamber structure
Figure 15C-5 Internal insert pipe type four-chamber structure
JB/T51411991
6.4D series muffler structure: see Figure 16~Figure 19. Figure 16D-1 Inserted pipe type perforated plate reflux four-chamber structure Figure 17D-2 Inserted pipe type perforated plate reflux four-chamber structure Figure 18D-3 Inserted pipe type four-chamber structure
Figure 19D-4 Inserted pipe type perforated plate reflux five-chamber structure 7
Shell and material structure
7.1 The sound radiation of the muffler shell structure is one of the sound transmission paths of the muffler. For mufflers requiring different insertion losses, a matching shell structure must be selected. The following methods are recommended to increase the shell sound transmission loss: Method
Increase shell thickness
Double-layer shell structure
Double-layer composite damping shell structure
Reduce shell sound radiation effect
5~9 dB
8~18dB
7.2 If resistive sound absorbing materials are used in the muffler, the materials must be able to withstand high temperatures above 400~500℃. 7.3 The muffler shell needs to be treated with anti-corrosion, such as high temperature resistant paint, chrome plating, porcelain or aluminum spraying, etc. If necessary, corrosion resistant materials such as aluminum-plated steel plates can also be used.
Additional Notes:
This standard is proposed and managed by Tianjin Internal Combustion Engine Research Institute. This standard is jointly drafted by Beijing Labor Protection Science Research Institute and Tianjin Internal Combustion Engine Research Institute. The drafters of this standard are Ren Wentang and Zhao Shen.
From the date of implementation of this standard, NJ/Z2-82 "Design Parameters for Small Gasoline Engine Exhaust Mufflers" will be invalid. 9
People's Republic of China
Mechanical Industry Standard
Design Parameters of Exhaust Muffler for Small Gasoline Engines JB/T 51411991
Published and issued by the China Academy of Mechanical Science
Printed by the China Academy of Mechanical Science
(No. 2 Shouti South Road, Beijing
Format 880×1230
Postal Code 100044)
1/16 Printing Sheet 7/8
Word Count 18.000
First Edition in September 1991
First Printing in September 1991
Price 2.00 Yuan
Print Quantity 1-500
Mechanical Industry Standard Service Network: http://www.JB.ac.cn1661_cn1661_cn1661_2 Air velocity in the muffler
The average air velocity in the muffler should not exceed the value given in Table 7. Table 7
Muffler beauty
Resistance muffler
Impedance muffler
Selection of perforated plate and inner tube parameters
Upper limit of flow rate
The perforation area of the perforated plate and the cross-sectional area of the inner tube should generally be close to the cross-sectional area of the muffler inlet. As the number of cavities increases, the flow area of the subsequent cavities can be gradually reduced, but it must not be lower than the outlet cross-sectional area of the muffler. 5
JB/T 51411991
The use of perforated plates and tubes with small apertures and a large number of perforations can help reduce low-frequency sound, but considering the manufacturing process and preventing the holes from being blocked by carbon deposits, the aperture is generally selected in the range of 5~8mm.
5.4.4 Exhaust port area of muffler
The exhaust port area of muffler can be calculated by formula (8): S,=10K,V,K
Exhaust port area of muffler, cm2;
Where: S—
Total displacement of gasoline engine, I;
Correction coefficient of gasoline engine stroke number, two-stroke gasoline engine K=2, four-stroke gasoline engine K,=1; K,—Correction coefficient of gasoline engine speed, K,=0.7+10-n; np
Rated speed of gasoline engine, r/min.
5.5 Length of muffler tail pipe
The length of muffler tail pipe has a certain influence on the muffler characteristics and power loss of muffler. The relationship between the tail pipe length and the volume resonance frequency of the muffler is:
Where: o
muffler volume resonance frequency, Hz;
sound velocity in the muffler, cm/s;
Ss—muffler tail pipe cross-sectional area, cm;
l——muffler tail pipe length, cm;
V.—muffler effective volume, L.
1000V. (+ sign)
Theoretical and practical proofs show that as the exhaust tail pipe length increases, the effective lower limit cutoff frequency of the muffler moves toward low frequency, which can significantly increase the insertion loss value of the muffler, especially the insertion loss value in the low and medium frequency range. The influence of the tail pipe length on the power characteristics is mainly reflected in the influence of the tail pipe reflected pressure wave. The test results show that when the tail pipe is at a specific length, it has the best power characteristics. When designing the muffler, the tail pipe length should be appropriately lengthened under the conditions allowed by the gasoline engine and the supporting equipment. The optimal tail pipe length should take into account both insertion loss and power loss, and is determined by a gasoline engine bench test. Muffler structure
This chapter recommends some typical muffler structures that can achieve the indicators in Chapter 2 according to the design parameters in Chapter 5. The recommended structure is the acoustic design structure of the muffler. The specific dimensions of the muffler and its components can be determined based on this design parameter and test; its structural design can be selected by the production unit according to the actual requirements of the product according to the structure in Articles 6.1 to 6.4. 6.1A series muffler structure: See Figures 1 to 5. Figure 1A-1 Internally inserted tube type two-chamber structure
JB/T5141-1991
Figure 2A-2 Perforated plate type two-chamber structure
Figure 3A-3 Perforated plate type reflux two-chamber structure
Figure 4A-4 Internally inserted tube type three-chamber structure
Figure 5A-5 Perforated plate type three-chamber structure
6.2B series muffler structure: see Figures 6 to 10. Figure 6B-1 Internally inserted tube type three-chamber structure
Figure 7B-2 Perforated plate type three-chamber structure
Figure 8B-3 Internally inserted tube and perforated plate type reflux three-chamber structure7
JB/T5141-1991
Figure 9B-4 Internally inserted tube and perforated plate type reflux three-chamber structure main
Figure 10B-5 Internally inserted tube type four-chamber structure
6.3 Structure of C series muffler: see Figures 11 to 15 . 1
C-1 Internal insert pipe and perforated plate type reflux four-chamber structure Figure 12
C-2 Internal insert pipe and perforated plate type reflux four-chamber structure Figure 14C-4 Internal insert pipe type reflux four-chamber structure
Figure 15C-5 Internal insert pipe type four-chamber structure
JB/T51411991
6.4D series muffler structure: see Figure 16~Figure 19. Figure 16D-1 Inserted pipe type perforated plate reflux four-chamber structure Figure 17D-2 Inserted pipe type perforated plate reflux four-chamber structure Figure 18D-3 Inserted pipe type four-chamber structure
Figure 19D-4 Inserted pipe type perforated plate reflux five-chamber structure 7
Shell and material structure
7.1 The sound radiation of the muffler shell structure is one of the sound transmission paths of the muffler. For mufflers requiring different insertion losses, a matching shell structure must be selected. The following methods are recommended to increase the shell sound transmission loss: Method
Increase shell thickness
Double-layer shell structure
Double-layer composite damping shell structure
Reduce shell sound radiation effect
5~9 dB
8~18dB
7.2 If resistive sound absorbing materials are used in the muffler, the materials must be able to withstand high temperatures above 400~500℃. 7.3 The muffler shell needs to be treated with anti-corrosion, such as high temperature resistant paint, chrome plating, porcelain or aluminum spraying, etc. If necessary, corrosion resistant materials such as aluminum-plated steel plates can also be used.
Additional Notes:
This standard is proposed and managed by Tianjin Internal Combustion Engine Research Institute. This standard is jointly drafted by Beijing Labor Protection Science Research Institute and Tianjin Internal Combustion Engine Research Institute. The drafters of this standard are Ren Wentang and Zhao Shen.
From the date of implementation of this standard, NJ/Z2-82 "Design Parameters for Small Gasoline Engine Exhaust Mufflers" will be invalid. 9
People's Republic of China
Mechanical Industry Standard
Design Parameters of Exhaust Muffler for Small Gasoline Engines JB/T 51411991
Published and issued by the China Academy of Mechanical Science
Printed by the China Academy of Mechanical Science
(No. 2 Shouti South Road, Beijing
Format 880×1230
Postal Code 100044)
1/16 Printing Sheet 7/8
Word Count 18.000
First Edition in September 1991
First Printing in September 1991
Price 2.00 Yuan
Print Quantity 1-500
Mechanical Industry Standard Service Network: http://www.JB.ac.cn1661_2 Air velocity in the muffler
The average air velocity in the muffler should not exceed the value given in Table 7. Table 7
Muffler beauty
Resistance muffler
Impedance muffler
Selection of perforated plate and inner tube parameters
Upper limit of flow rate
The perforation area of the perforated plate and the cross-sectional area of the inner tube should generally be close to the cross-sectional area of the muffler inlet. As the number of cavities increases, the flow area of the subsequent cavities can be gradually reduced, but it must not be lower than the outlet cross-sectional area of the muffler. 5
JB/T 51411991
The use of perforated plates and tubes with small apertures and a large number of perforations can help reduce low-frequency sound, but considering the manufacturing process and preventing the holes from being blocked by carbon deposits, the aperture is generally selected in the range of 5~8mm.
5.4.4 Exhaust port area of muffler
The exhaust port area of muffler can be calculated by formula (8): S,=10K,V,K
Exhaust port area of muffler, cm2;
Where: S—
Total displacement of gasoline engine, I;
Correction coefficient of gasoline engine stroke number, two-stroke gasoline engine K=2, four-stroke gasoline engine K,=1; K,—Correction coefficient of gasoline engine speed, K,=0.7+10-n; np
Rated speed of gasoline engine, r/min.
5.5 Length of muffler tail pipe
The length of muffler tail pipe has a certain influence on the muffler characteristics and power loss of muffler. The relationship between the tail pipe length and the volume resonance frequency of the muffler is:
Where: o
muffler volume resonance frequency, Hz;
sound velocity in the muffler, cm/s;
Ss—muffler tail pipe cross-sectional area, cm;
l——muffler tail pipe length, cm;
V.—muffler effective volume, L.
1000V. (+ sign)
Theoretical and practical proofs show that as the exhaust tail pipe length increases, the effective lower limit cutoff frequency of the muffler moves toward low frequency, which can significantly increase the insertion loss value of the muffler, especially the insertion loss value in the low and medium frequency range. The influence of the tail pipe length on the power characteristics is mainly reflected in the influence of the tail pipe reflected pressure wave. The test results show that when the tail pipe is at a specific length, it has the best power characteristics. When designing the muffler, the tail pipe length should be appropriately lengthened under the conditions allowed by the gasoline engine and the supporting equipment. The optimal tail pipe length should take into account both insertion loss and power loss, and is determined by a gasoline engine bench test. Muffler structure
This chapter recommends some typical muffler structures that can achieve the indicators in Chapter 2 according to the design parameters in Chapter 5. The recommended structure is the acoustic design structure of the muffler. The specific dimensions of the muffler and its components can be determined based on this design parameter and test; its structural design can be selected by the production unit according to the structure in 6.1~6.4 according to the actual requirements of the product. 6.1A series muffler structure: See Figure 1~Figure 5. Figure 1A-1 Internally inserted tube type two-chamber structure
JB/T5141-1991
Figure 2A-2 Perforated plate type two-chamber structure
Figure 3A-3 Perforated plate type reflux two-chamber structure
Figure 4A-4 Internally inserted tube type three-chamber structure
Figure 5A-5 Perforated plate type three-chamber structure
6.2B series muffler structure: see Figures 6 to 10. Figure 6B-1 Internally inserted tube type three-chamber structure
Figure 7B-2 Perforated plate type three-chamber structure
Figure 8B-3 Internally inserted tube and perforated plate type reflux three-chamber structure7
JB/T5141-1991
Figure 9B-4 Internally inserted tube and perforated plate type reflux three-chamber structure main
Figure 10B-5 Internally inserted tube type four-chamber structure
6.3 Structure of C series muffler: see Figures 11 to 15 . 1
C-1 Internal insert pipe and perforated plate type reflux four-chamber structure Figure 12
C-2 Internal insert pipe and perforated plate type reflux four-chamber structure C-3 Internal insert pipe and perforated plate type reflux four-chamber structure Figure 14C-4 Internal insert pipe type reflux four-chamber structure
Figure 15C-5 Internal insert pipe type four-chamber structure
JB/T51411991
6.4D series muffler structure: see Figure 16~Figure 19. Figure 16D-1 Inserted pipe type perforated plate reflux four-chamber structure Figure 17D-2 Inserted pipe type perforated plate reflux four-chamber structure Figure 18D-3 Inserted pipe type four-chamber structure
Figure 19D-4 Inserted pipe type perforated plate reflux five-chamber structure 7
Shell and material structure
7.1 The sound radiation of the muffler shell structure is one of the sound transmission paths of the muffler. For mufflers requiring different insertion losses, a matching shell structure must be selected. The following methods are recommended to increase the shell sound transmission loss: Method
Increase shell thickness
Double-layer shell structure
Double-layer composite damping shell structure
Reduce shell sound radiation effect
5~9 dB
8~18dB
7.2 If resistive sound absorbing materials are used in the muffler, the materials must be able to withstand high temperatures above 400~500℃. 7.3 The muffler shell needs to be treated with anti-corrosion, such as high temperature resistant paint, chrome plating, porcelain or aluminum spraying, etc. If necessary, corrosion resistant materials such as aluminum-plated steel plates can also be used.
Additional Notes:
This standard is proposed and managed by Tianjin Internal Combustion Engine Research Institute. This standard is jointly drafted by Beijing Labor Protection Science Research Institute and Tianjin Internal Combustion Engine Research Institute. The drafters of this standard are Ren Wentang and Zhao Shen.
From the date of implementation of this standard, NJ/Z2-82 "Design Parameters for Small Gasoline Engine Exhaust Mufflers" will be invalid. 9
People's Republic of China
Mechanical Industry Standard
Design Parameters of Exhaust Muffler for Small Gasoline Engines JB/T 51411991
Published and issued by the China Academy of Mechanical Science
Printed by the China Academy of Mechanical Science
(No. 2 Shouti South Road, Beijing
Format 880×1230
Postal Code 100044)
1/16 Printing Sheet 7/8
Word Count 18.000
First Edition in September 1991
First Printing in September 1991
Price 2.00 Yuan
Print Quantity 1-500
Mechanical Industry Standard Service Network: http://www.JB.ac.cn1661_(+ sign)
Theoretical and practical proofs show that as the exhaust tail pipe length increases, the effective lower limit cutoff frequency of the muffler moves toward low frequency, which can significantly increase the insertion loss value of the muffler, especially the insertion loss value in the low and medium frequency range. The influence of tail pipe length on power characteristics is mainly reflected in the influence of the tail pipe reflected pressure wave. The test results show that when the tail pipe is at a specific length, it has the best power characteristics. When designing the muffler, the tail pipe length should be appropriately lengthened under the conditions allowed by the gasoline engine and the supporting equipment. The optimal tail pipe length should take into account both insertion loss and power loss, and is determined by the gasoline engine bench test. Muffler structure
This chapter recommends some typical muffler structures that can achieve the indicators of Chapter 2 according to the design parameters of Chapter 5. The recommended structure is the acoustic design structure of the muffler. The specific dimensions of the muffler and its components can be determined according to this design parameter and test; its structural design can be selected by the production unit according to the structure in 6.1~6.4 according to the actual requirements of the product. 6.1A series muffler structure: See Figure 1~Figure 5. Figure 1A-1 Internally inserted tube type two-chamber structure
JB/T5141-1991
Figure 2A-2 Perforated plate type two-chamber structure
Figure 3A-3 Perforated plate type reflux two-chamber structure
Figure 4A-4 Internally inserted tube type three-chamber structure
Figure 5A-5 Perforated plate type three-chamber structure
6.2B series muffler structure: see Figures 6 to 10. Figure 6B-1 Internally inserted tube type three-chamber structure
Figure 7B-2 Perforated plate type three-chamber structure
Figure 8B-3 Internally inserted tube and perforated plate type reflux three-chamber structure7
JB/T5141-1991
Figure 9B-4 Internally inserted tube and perforated plate type reflux three-chamber structure main
Figure 10B-5 Internally inserted tube type four-chamber structure
6.3 Structure of C series muffler: see Figures 11 to 15 . 1
C-1 Internal insert pipe and perforated plate type reflux four-chamber structure Figure 12
C-2 Internal insert pipe and perforated plate type reflux four-chamber structure C-3 Internal insert pipe and perforated plate type reflux four-chamber structure Figure 14C-4 Internal insert pipe type reflux four-chamber structure
Figure 15C-5 Internal insert pipe type four-chamber structure
JB/T51411991
6.4D series muffler structure: see Figure 16~Figure 19. Figure 16D-1 Inserted pipe type perforated plate reflux four-chamber structure Figure 17D-2 Inserted pipe type perforated plate reflux four-chamber structure Figure 18D-3 Inserted pipe type four-chamber structure
Figure 19D-4 Inserted pipe type perforated plate reflux five-chamber structure 7
Shell and material structure
7.1 The sound radiation of the muffler shell structure is one of the sound transmission paths of the muffler. For mufflers requiring different insertion losses, a matching shell structure must be selected. The following methods are recommended to increase the shell sound transmission loss: Method
Increase shell thickness
Double-layer shell structure
Double-layer composite damping shell structure
Reduce shell sound radiation effect
5~9 dB
8~18dB
7.2 If resistive sound absorbing materials are used in the muffler, the materials must be able to withstand high temperatures above 400~500℃. 7.3 The muffler shell needs to be treated with anti-corrosion, such as high temperature resistant paint, chrome plating, porcelain or aluminum spraying, etc. If necessary, corrosion resistant materials such as aluminum-plated steel plates can also be used.
Additional Notes:
This standard is proposed and managed by Tianjin Internal Combustion Engine Research Institute. This standard is jointly drafted by Beijing Labor Protection Science Research Institute and Tianjin Internal Combustion Engine Research Institute. The drafters of this standard are Ren Wentang and Zhao Shen.
From the date of implementation of this standard, NJ/Z2-82 "Design Parameters for Small Gasoline Engine Exhaust Mufflers" will be invalid. 9
People's Republic of China
Mechanical Industry Standard
Design Parameters of Exhaust Muffler for Small Gasoline Engines JB/T 51411991
Published and issued by the China Academy of Mechanical Science
Printed by the China Academy of Mechanical Science
(No. 2 Shouti South Road, Beijing
Format 880×1230
Postal Code 100044)
1/16 Printing Sheet 7/8
Word Count 18.000
First Edition in September 1991
First Printing in September 1991
Price 2.00 Yuan
Print Quantity 1-500
Mechanical Industry Standard Service Network: http://www.JB.ac.cn1661_(+ sign)
Theoretical and practical proofs show that as the exhaust tail pipe length increases, the effective lower limit cutoff frequency of the muffler moves toward low frequency, which can significantly increase the insertion loss value of the muffler, especially the insertion loss value in the low and medium frequency range. The influence of tail pipe length on power characteristics is mainly reflected in the influence of the tail pipe reflected pressure wave. The test results show that when the tail pipe is at a specific length, it has the best power characteristics. When designing the muffler, the tail pipe length should be appropriately lengthened under the conditions allowed by the gasoline engine and the supporting equipment. The optimal tail pipe length should take into account both insertion loss and power loss, and is determined by the gasoline engine bench test. Muffler structure
This chapter recommends some typical muffler structures that can achieve the indicators of Chapter 2 according to the design parameters of Chapter 5. The recommended structure is the acoustic design structure of the muffler. The specific dimensions of the muffler and its components can be determined according to this design parameter and test; its structural design can be selected by the production unit according to the structure in 6.1~6.4 according to the actual requirements of the product. 6.1A series muffler structure: See Figure 1~Figure 5. Figure 1A-1 Internally inserted tube type two-chamber structure
JB/T5141-1991
Figure 2A-2 Perforated plate type two-chamber structure
Figure 3A-3 Perforated plate type reflux two-chamber structure
Figure 4A-4 Internally inserted tube type three-chamber structure
Figure 5A-5 Perforated plate type three-chamber structure
6.2B series muffler structure: see Figures 6 to 10. Figure 6B-1 Internally inserted tube type three-chamber structure
Figure 7B-2 Perforated plate type three-chamber structure
Figure 8B-3 Internally inserted tube and perforated plate type reflux three-chamber structure7
JB/T5141-1991
Figure 9B-4 Internally inserted tube and perforated plate type reflux three-chamber structure main
Figure 10B-5 Internally inserted tube type four-chamber structure
6.3 Structure of C series muffler: see Figures 11 to 15 . 1
C-1 Internal insert pipe and perforated plate type reflux four-chamber structure Figure 12
C-2 Internal insert pipe and perforated plate type reflux four-chamber structure Figure 14C-4 Internal insert pipe type reflux four-chamber structure
Figure 15C-5 Internal insert pipe type four-chamber structure
JB/T51411991
6.4D series muffler structure: see Figure 16~Figure 19. Figure 16D-1 Inserted pipe type perforated plate reflux four-chamber structure Figure 17D-2 Inserted pipe type perforated plate reflux four-chamber structure Figure 18D-3 Inserted pipe type four-chamber structure
Figure 19D-4 Inserted pipe type perforated plate reflux five-chamber structure 7
Shell and material structure
7.1 The sound radiation of the muffler shell structure is one of the sound transmission paths of the muffler. For mufflers requiring different insertion losses, a matching shell structure must be selected. The following methods are recommended to increase the shell sound transmission loss: Method
Increase shell thickness
Double-layer shell structure
Double-layer composite damping shell structure
Reduce shell sound radiation effect
5~9 dB
8~18dB
7.2 If resistive sound absorbing materials are used in the muffler, the materials must be able to withstand high temperatures above 400~500℃. 7.3 The muffler shell needs to be treated with anti-corrosion, such as high temperature resistant paint, chrome plating, porcelain or aluminum spraying, etc. If necessary, corrosion resistant materials such as aluminum-plated steel plates can also be used.
Additional Notes:
This standard is proposed and managed by Tianjin Internal Combustion Engine Research Institute. This standard is jointly drafted by Beijing Labor Protection Science Research Institute and Tianjin Internal Combustion Engine Research Institute. The drafters of this standard are Ren Wentang and Zhao Shen.
From the date of implementation of this standard, NJ/Z2-82 "Design Parameters for Small Gasoline Engine Exhaust Mufflers" will be invalid. 9
People's Republic of China
Mechanical Industry Standard
Design Parameters of Exhaust Muffler for Small Gasoline Engines JB/T 51411991
Published and issued by the China Academy of Mechanical Science
Printed by the China Academy of Mechanical Science
(No. 2 Shouti South Road, Beijing
Format 880×1230
Postal Code 100044)
1/16 Printing Sheet 7/8
Word Count 18.000
First Edition in September 1991
First Printing in September 1991
Price 2.00 Yuan
Print Quantity 1-500
Mechanical Industry Standard Service Network: http://www.JB.ac.cn1661_
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