Engine test bed exhaust system
By constructing a multi-stage noise reduction and cooling exhaust system for the engine test bench, the problem of difficult-to-control exhaust noise of the engine test bench was solved, achieving a significant noise reduction effect, meeting environmental protection standards, and reducing the impact on the environment.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-24
- Publication Date
- 2026-04-14
AI Technical Summary
Exhaust noise problems in existing engine test benches are difficult to solve effectively, and existing noise reduction measures are costly and ineffective, affecting the surrounding environment and the health of researchers.
The exhaust system, which consists of components such as wall-mounted air ducts, spray air ducts, exhaust air ducts, inner cylinders, connecting elbows, silencers, silencer pipes, and end silencer bends, reduces noise energy through multi-stage silencing and cooling treatment.
It achieved an overall noise reduction effect of over 50dB, met national environmental protection standards, solved the noise pollution problem of the test bench, and reduced the impact on the surrounding environment.
Smart Images
Figure CN224122174U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of exhaust technology, and in particular to an exhaust system for an engine test bench. Background Technology
[0002] With the vigorous development of China's economy, investment in aerospace, civil aviation and military is also increasing. The aero-engine industry is also receiving attention. my country's aero-engine industry will continue to dedicate itself to improving technical parameters and building technical systems, strengthening the industry's technical research and development and quality assurance capabilities, and realizing the widespread application of engine technology. As the engine is the heart of an aircraft, engine research is of paramount importance.
[0003] With the intensification of global warming and climate change, environmental protection has become a major focus of public attention. The aero-engine industry will continue to actively address environmental issues, which necessitates compliance with the environmental protection requirements of engine systems. To this end, the industry will continue to strengthen the environmentally friendly design of aero-engines, continuously improve the energy consumption and environmental protection levels of military aero-engines, and enhance the assessment and monitoring of environmental impacts. Generally, various performance tests of engines are conducted in laboratories, and improvements and adjustments are made based on the test data. Regardless of the type of engine used, they all share a common characteristic: the strong noise and gas emissions they produce. Our noise testing of different types of engines shows that exhaust noise levels all exceed 100dB. However, engine laboratories are typically located in office areas, schools, and industrial parks, creating a significant conflict with national noise control standards. The noise generated by engine test benches seriously affects the surrounding environment and the physical and mental health of researchers.
[0004] The pollution from engine test benches mainly comes from the noise and air pollution generated by their own exhaust. There are many noise reduction measures for engine test benches, but none of them are ideal and the investment costs are very high. Currently, the solution is to build complex exhaust channels and huge mufflers outside the exhaust port to solve exhaust noise. Utility Model Content
[0005] The purpose of this utility model is to at least solve one of the technical problems existing in the prior art, and to provide an exhaust system for an engine test bench that can solve the problems in the background art.
[0006] To achieve the above objectives, this utility model provides the following technical solution: an exhaust system for an engine test bench, including a wall-mounted air duct, a spray air duct installed on one side of the wall-mounted air duct, an exhaust air duct installed on one side of the spray air duct, an inner cylinder movably installed on one side of the exhaust air duct, a transition elbow provided on the upper end of the inner cylinder, a muffler provided on one end of the transition elbow, a muffler pipe installed on the upper side of the muffler, and an end muffler bend installed on the upper end of the muffler pipe.
[0007] Preferably, an annular connecting pipe is installed on the spray duct, one side of which is connected to a main water inlet pipe, and a branch pipe is connected to the annular connecting pipe. The branch pipe extends into the interior of the spray duct, and a spray head is fixedly installed on one end of the branch pipe that extends into the interior of the spray duct.
[0008] Preferably, a stainless steel mounting plate is provided on one side of the transition elbow.
[0009] Preferably, a conical block is fixedly installed inside the inner cylinder.
[0010] Preferably, the interior of the end silencing bend is provided with a low-frequency standing wave sound-absorbing component.
[0011] Compared with the prior art, the beneficial effects of this utility model are:
[0012] (1) The exhaust system of the engine test bench, through the setting of muffler and muffler pipe, can better reduce the energy of noise. After the airflow passes through the narrow space, it generates friction and expansion and compression process, which effectively reduces the energy of sound transmission. Attached Figure Description
[0013] The present invention will be further described below with reference to the accompanying drawings and embodiments:
[0014] Figure 1 This is a schematic diagram of the exhaust system of an engine test bench according to the present invention;
[0015] Figure 2 This is a schematic diagram of the spray duct of this utility model;
[0016] Figure 3 This is a schematic diagram of the adapter elbow of this utility model;
[0017] Figure 4 This is a schematic diagram of the end silencing bend of this utility model.
[0018] Reference numerals in the attached diagram: 1. Through-wall air duct; 2. Spray air duct; 3. Exhaust air duct; 4. Adapter elbow; 5. Inner cylinder; 6. Conical block; 7. Silencer; 8. Silencer pipe; 9. End silencer elbow; 10. Main water inlet pipe; 11. Annular connecting pipe; 12. Branch pipe; 13. Spray head; 14. Stainless steel mounting plate; 15. Low-frequency standing wave sound-absorbing component. Detailed Implementation
[0019] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.
[0020] To further understand the content of this utility model, a detailed description of this utility model will be provided in conjunction with the accompanying drawings.
[0021] Please see Figure 1-4 This utility model provides a technical solution: an exhaust system for an engine test bench, including a wall-mounted air duct 1, a spray air duct 2 installed on one side of the wall-mounted air duct 1, an exhaust air duct 3 installed on one side of the spray air duct 2, an inner cylinder 5 movably installed on one side of the exhaust air duct 3, a transition elbow 4 provided on the upper end of the inner cylinder 5, a muffler 7 provided on one end of the transition elbow 4, a muffler pipe 8 installed on the upper side of the muffler 7, and an end muffler bend 9 installed on the upper end of the muffler pipe 8.
[0022] The wall-mounted air duct 1 is connected to the engine exhaust port. When the engine is working, the generated gas enters the interior of the wall-mounted air duct 1, and then enters the interior of the spray air duct 2 through the wall-mounted air duct 1. The spray air duct 2 cools down the gas discharged from the engine. The cooled gas enters the interior of the inner cylinder 5 through multiple exhaust air ducts 3, and then enters the interior of the muffler 7 through the connecting elbow 4 for silencing. Then it is silenced again through the muffler pipe 8, and finally discharged through the end muffler elbow 9 to achieve the discharge of engine gas.
[0023] The main function of the through-wall air duct 1 is to connect to the engine exhaust port and, after passing through the outer wall of the test bench, to connect with the spray air duct. It is also the first-stage ejector of the exhaust system.
[0024] The main function of the silencer tube 8 is to assist the silencer in achieving a higher noise reduction effect. The noise reduction effect of the silencer has a limit. When the noise source value exceeds the noise reduction level of the silencer, in order to ensure that emissions meet the standards, the silencer tube is installed, which can effectively improve the overall noise reduction effect. All of them are processed and formed in the factory and assembled on site. The length of the silencer tube is finally determined through noise data collection and acoustic calculation.
[0025] A ring-shaped connecting pipe 11 is installed on the spray duct 2. One side of the ring-shaped connecting pipe 11 is connected to the main water inlet pipe 10. A branch pipe 12 is connected to the ring-shaped connecting pipe 11. The branch pipe 12 extends into the interior of the spray duct 2. A spray head 13 is fixedly installed on one end of the branch pipe 12 that extends into the interior of the spray duct 2.
[0026] The main water inlet pipe 10 is connected to an external water supply mechanism, thereby delivering external water into the interior of the annular connecting pipe 11, which then discharges into the interior of multiple branch pipes 12, and finally through multiple spray nozzles 13. The water discharged from the spray nozzles 13 cools the heat in the exhaust gas, thereby reducing the heat of the exhaust gas.
[0027] A stainless steel mounting plate 14 is provided on one side of the transition elbow 4.
[0028] The stainless steel mounting plate 14 is connected to the adapter elbow 4 by bolts, which facilitates the installation and removal of the stainless steel mounting plate 14.
[0029] A conical block 6 is fixedly installed inside the inner cylinder 5.
[0030] The flange at one end of the inner cylinder 5 is connected to the exhaust duct 3. The conical block 6 is a conical flow guide structure. Corresponding to the conical structure, there are channels on the pipe wall. The channels are circular holes with a diameter of 60 mm, which are evenly distributed. The total effective ventilation area of the circular holes is exactly the same as the area of the exhaust duct 3. After the airflow passes through the conical flow guide structure, it is discharged through the circular holes distributed on the inner wall of the inner cylinder 5. The purpose of this design is to better reduce the energy of noise. After the airflow passes through the narrow space, it generates friction and expansion and compression processes, which effectively reduces the energy of sound transmission.
[0031] The interior of the end silencing bend 9 is equipped with a low-frequency standing wave sound-absorbing component 15.
[0032] Due to the low-frequency noise characteristics of the low-frequency standing wave sound-absorbing component 15, the propagation distance is farther and the penetration ability is stronger compared with mid- and high-frequency noise. The end silencing bend 9 is mainly composed of a metal shell and the internal low-frequency standing wave sound-absorbing component 15. Through this structure, the noise in the frequency band is effectively reduced. The standing wave silencing structure is designed as a streamlined arc, which transforms the right-angle bend of the shell into an arc-shaped bend structure suitable for airflow. It cleverly utilizes the straight-line propagation characteristics of sound waves. The low-frequency standing wave sound-absorbing component 15 is located at the reflection point of the sound wave. All sound waves passing through the pipe must pass through the standing wave silencing structure, which plays an important role in the overall noise reduction effect.
[0033] Working principle of muffler 7
[0034] The air intake flange is connected to the engine exhaust port. High-speed airflow enters the primary silencing chamber through a flange pipe with a perforation at one end. As the airflow passes through the holes in the flange, it undergoes a significant compression process, forcing it to slow down. After compression, the airflow enters the first silencing chamber, which is constructed with a thin metal plate. The plate forms a multi-layered hollow structure with the outer shell and the support angles. When sound waves radiate onto the surface of the metal plate, they cause the plate to vibrate. Another portion of the noise penetrates the first layer of the plate and is reflected onto the second layer. There is another hollow layer between the second layer and the outer shell. The sound waves are reflected to cause the plate to vibrate, which greatly reduces the noise energy. Furthermore, the metal plate is made of a high-temperature resistant material, which is better than the traditional method of adding sound-absorbing materials inside the cavity.
[0035] After passing through the first resonant cavity, the airflow will enter the next cavity through the array holes on the first-stage sound-absorbing baffle. The internal structure of the cavity is the same as that of the previous cavity. Both cavities use metal thin plate resonance to reduce low-frequency noise. After the low-frequency noise is reduced, the penetration ability of mid- and high-frequency noise is relatively low and the propagation distance is shorter, which is conducive to further noise control.
[0036] The airflow passes through the second cavity and enters the secondary silencing baffle, which also has an array of circular holes. A cylinder of a certain length is inserted into the holes, with open ends. The airflow passes through the channel inside the cylinder and enters the next silencing cavity. Through experimental research, the noise reduction effect when the noise passes through the narrow channel is much better than that when it passes through the circular holes, improving the noise reduction effect by at least 3 decibels. The second function of the cylindrical structure here is that the airflow passes through faster, creating a negative pressure effect inside the cavity, improving the exhaust effect and reducing pressure loss.
[0037] After passing through the cylindrical air vents on the secondary silencing plate, the airflow enters the mid-to-high frequency silencing chamber. The outer walls are equipped with two layers of perforated metal sound-absorbing panels. The first layer has a perforation rate of 35%, and the second layer has a perforation rate of 30%. The two layers are fixed together by metal supports, forming a 50mm hollow layer. There is also a 35mm thick hollow layer between the two layers of perforated panels and the outer metal shell. Sound-absorbing cotton, which is a 50mm thick sound-absorbing structural layer, is filled between the two layers of perforated panels. The sound waves expand and reflect within the cavity, passing through the perforated sound-absorbing panels and the sound-absorbing cotton, and working in conjunction with the back cavity between the perforated panels and the outer shell to achieve noise reduction in the mid-to-high frequency range. The sound absorption coefficient of the material reaches over 0.9. At the same time, the two layers of perforated metal panels with different perforation rates avoid the misalignment effect.
[0038] After the first noise reduction of the mid-to-high frequency range, the sound waves pass through the three-stage silencing baffle with the airflow. The third-stage baffle is the same as the first-stage silencing baffle, with an array of circular holes. The total cross-sectional area of the holes is exactly the same as the inner diameter of the flange. The airflow enters the next silencing cavity, and the surrounding structure is the same as the previous cavity. It mainly weakens the mid-to-high frequency range again and is also the end of the silencing process.
[0039] The outlet flange adopts an inner sleeve type that extends into the end silencer cavity. The inlet of the pipe is closed, and there are holes around the pipe wall. The holes are arranged in multiple rows to ensure that the ventilation cross-sectional area of the holes is consistent with the inner diameter cross-sectional area of the inlet flange. The diameter of the round hole is 35mm.
[0040] Our practical application has demonstrated that this structure achieves a sound insulation performance of over 40dB. After connecting the two ends with exhaust muffler pipes totaling 4 meters in length, the overall noise reduction effect reaches over 50dB. The noise level generated during the turbojet engine test was 132dB. By measuring the noise level at the factory boundary 30 meters away, the noise level reached below 44dB, achieving the highest national standard emission limit for Class I areas. This data shows that this technology has made a significant breakthrough and has also solved the problem of test bench site selection.
[0041] Working principle:
[0042] The wall-mounted air duct 1 is connected to the engine exhaust port. When the engine is working, the generated gas enters the interior of the wall-mounted air duct 1, and then enters the interior of the spray air duct 2 through the wall-mounted air duct 1. The spray air duct 2 cools down the gas discharged from the engine. The cooled gas enters the interior of the inner cylinder 5 through multiple exhaust air ducts 3, and then enters the interior of the muffler 7 through the connecting elbow 4 for silencing. Then it is silenced again through the muffler pipe 8, and finally discharged through the end muffler elbow 9 to achieve the discharge of engine gas.
[0043] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.
Claims
1. An exhaust system for an engine test bench, comprising a wall-mounted air duct (1), characterized in that: A spray duct (2) is installed on one side of the wall-mounted air duct (1), an exhaust duct (3) is installed on one side of the spray duct (2), an inner cylinder (5) is movably installed on one side of the exhaust duct (3), a transition elbow (4) is provided on the upper end of the inner cylinder (5), a silencer (7) is provided on one end of the transition elbow (4), a silencer pipe (8) is installed on the upper side of the silencer (7), and an end silencer elbow (9) is installed on the upper end of the silencer pipe (8).
2. The exhaust system for an engine test bench according to claim 1, characterized in that: An annular connecting pipe (11) is installed on the spray duct (2). One side of the annular connecting pipe (11) is connected to the main water inlet pipe (10). A branch pipe (12) is connected to the annular connecting pipe (11). The branch pipe (12) extends into the interior of the spray duct (2). A spray head (13) is fixedly installed on one end of the branch pipe (12) that extends into the interior of the spray duct (2).
3. The exhaust system for an engine test bench according to claim 2, characterized in that: A stainless steel mounting plate (14) is provided on one side of the transition elbow (4).
4. The exhaust system for an engine test bench according to claim 3, characterized in that: A conical block (6) is fixedly installed inside the inner cylinder (5).
5. The exhaust system for an engine test bench according to claim 4, characterized in that: The end silencing bend (9) is equipped with a low-frequency standing wave sound-absorbing component (15).