Roller heat pump drying all-in-one machine
By using heat pump system components and heat exchangers in the tumble dryer, the waste heat in the waste gas is effectively utilized, and the problems of energy waste and thermal pollution in the prior art are solved, thereby improving drying efficiency and environmental protection effect.
Patent Information
- Application Number
- CN202421538948.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-01
- Publication Date
- 2025-05-02
- Estimated Expiration
- 2034-07-01
AI Technical Summary
The existing tumble dryers have problems of energy waste and thermal pollution during the heating process, especially the failure to effectively utilize the waste heat in the exhaust gas.
The heat pump system components and heat exchanger are used to heat the inflow air flow through the condenser, and the waste heat in the exhaust gas is absorbed through the evaporator, and the waste heat is transferred to the condenser by refrigerant circulation, and the gas flow is further heated.
The heating speed of drum drying is improved, the drying effect is improved, the heat pollution emission is reduced, and the waste heat is effectively utilized.
Smart Images
Figure CN222824706U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of heat pump equipment, and in particular to a drum heat pump drying machine. Background Art
[0002] At present, drum dryers are widely used in hospitals, schools, hotels, and mines. The heat sources of common drum dryers on the market mainly include steam heat exchangers and electric heaters, which heat the flowing air. The hot air flows through the materials rolling in the drum (such as dried fruits, linens, clothes, etc.), accelerates the evaporation of moisture in the materials and takes away the moisture to achieve the purpose of drying. However, the heating cost of steam and electricity is relatively high.
[0003] At the same time, the exhaust gas emitted by the drum dryer contains a lot of waste heat (including sensible heat and latent heat of water vapor), which is directly discharged into the air. Technical personnel in this field have also applied heat pump systems to drum dryers, but there is also a problem that the waste heat in the exhaust gas cannot be effectively utilized, which not only causes energy waste, but also forms thermal pollution. Utility Model Content
[0004] The present application aims to solve at least one of the above-mentioned technical problems in the prior art to a certain extent. To this end, the present application provides a drum heat pump drying machine, which uses a heat pump system component to heat the airflow entering the drum, and can effectively utilize the waste heat of the exhaust gas discharged from the exhaust gas discharge channel to improve the drum drying heating speed.
[0005] According to an embodiment of the present application, a drum heat pump drying machine includes a drum with an inner cavity, the drum is equipped with at least one drying component, the drying component includes an air duct assembly, the air duct assembly includes a hot air input channel and an exhaust gas exhaust channel, the hot air input channel has a first air inlet and a first air outlet, the first air outlet is connected to the inner cavity of the drum, the exhaust gas exhaust channel has a second air inlet and a second air outlet, the second air inlet is connected to the inner cavity of the drum, and the exhaust gas exhaust channel is provided with a fan so that the airflow flows into the first air inlet of the hot air input channel and flows to the second air outlet of the exhaust gas exhaust channel after passing through the inner cavity of the drum; A pump system component, the heat pump system component includes a compressor, a condenser, a throttling element and an evaporator that form a refrigerant cycle, the condenser is arranged in the hot gas input channel to heat the airflow flowing into the hot gas input channel, and the evaporator is arranged in the exhaust gas exhaust channel to absorb the residual heat of the airflow flowing out of the exhaust gas exhaust channel; and a heat exchanger, the heat exchanger has a first heat exchange unit and a second heat exchange unit that exchange heat with each other, the first heat exchange unit is arranged in the exhaust gas exhaust channel, and the second heat exchange unit is arranged in the hot gas input channel, so as to exchange heat between the airflow flowing out of the exhaust gas exhaust channel and the airflow flowing into the hot gas input channel.
[0006] In an optional or preferred embodiment, the heat exchanger is a composite phase change heat exchanger, the first heat exchange unit and the second heat exchange unit are respectively a first heat exchange end and a second heat exchange end arranged at two ends, the first heat exchange end is arranged in the exhaust gas discharge channel, and the second heat exchange end is arranged in the hot gas input channel, so as to perform heat exchange between the airflow in the exhaust gas discharge channel and the airflow in the hot gas input channel. Further, the second heat exchange end is arranged between the first air inlet and the condenser, so that the airflow flowing into the first air inlet first passes through the second heat exchange end and then flows to the condenser; the first heat exchange end is arranged between the second air inlet and the evaporator, so that the airflow flowing into the second air inlet first passes through the first heat exchange end and then flows to the evaporator.
[0007] In an optional or preferred embodiment, the heat exchanger is a partition-type heat exchanger, the first heat exchange unit and the second heat exchange unit are respectively a first heat exchange channel and a second heat exchange channel arranged in a cross flow, the first heat exchange channel is arranged in the exhaust gas discharge channel, and the second heat exchange channel is arranged in the hot gas input channel, so as to perform heat exchange between the airflow of the exhaust gas discharge channel and the airflow of the hot gas input channel. Further, the second heat exchange channel is arranged between the first air inlet and the condenser, so that the airflow flowing into the first air inlet first passes through the second heat exchange channel and then flows to the condenser; the first heat exchange channel is arranged between the second air inlet and the evaporator, so that the airflow flowing into the second air inlet first passes through the first heat exchange channel and then flows to the evaporator.
[0008] In an optional or preferred embodiment, the first air inlet of the hot air input channel is provided with a first filter device, and the first filter device is arranged at the air inlet front end of the second heat exchange unit, so that the airflow passes through the first filter device before flowing to the second heat exchange unit; the second air inlet position of the exhaust gas exhaust channel is installed with a second filter device, so that the airflow passes through the second filter device before flowing into the exhaust gas exhaust channel.
[0009] In an optional or preferred embodiment, an auxiliary heater is installed at the first air outlet position of the hot air input channel.
[0010] In an optional or preferred embodiment, two drying components are provided and are distributed on the left and right. Further, the two hot air input channels are interconnected at the first air outlet and share the first air outlet, and the first air outlet is connected to the inner cavity of the drum to supply hot air to the inner cavity of the drum. The two waste gas exhaust channels are interconnected at the second air inlet and share the second air inlet, and the second air inlet is connected to the inner cavity of the drum to exhaust waste gas from the inner cavity of the drum.
[0011] Based on the above technical solution, the embodiment of the present application has at least the following beneficial effects: In the above technical solution, the condenser of the heat pump system component heats the airflow flowing into the hot air input channel, and the heated fresh air can heat and dry the materials in the drum and take away the moisture, and then become waste gas and be discharged from the waste gas discharge channel. The evaporator of the heat pump system component can absorb the waste heat in the waste gas, and the refrigerant circulation transfers the waste heat to the condenser to heat the fresh air after natural heat exchange, so that it is further heated. The heat exchanger exchanges heat in a phase change manner or a partition wall manner. The first heat exchange unit absorbs the waste heat in the waste gas, and then exchanges heat to the second heat exchange unit to heat the airflow. The present application adopts a heat exchanger and a heat pump system component. The waste heat of the waste gas is utilized in two stages of the heat exchanger and the evaporator, which increases the heating speed of the drum drying, improves the drying effect, reduces thermal pollution emissions, and helps to improve the working environment. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The present application is further described below with reference to the accompanying drawings and embodiments;
[0013] Figure 1 It is a structural schematic diagram of Embodiment 1 of the present application;
[0014] Figure 2 It is a structural diagram of Embodiment 2 of the present application;
[0015] Figure 3 It is a structural diagram of the second embodiment of the present application.
[0016] Reference numerals: roller 11;
[0017] Hot air input channel 21, exhaust gas discharge channel 22, first air inlet 23, first air outlet 24, second air inlet 25, second air outlet 26, fan 27;
[0018] Compressor 31, condenser 32, throttling element 33, evaporator 34;
[0019] Heat exchanger 40, first heat exchange end 41, second heat exchange end 42;
[0020] A first filtering device 51, a second filtering device 52;
[0021] Auxiliary heater 61. DETAILED DESCRIPTION
[0022] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.
[0023] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.
[0024] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.
[0025] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.
[0026] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being “above”, “above”, and “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.
[0027] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.
[0028] Embodiment 1
[0029] Refer to the following Figure 1 This embodiment describes a drum heat pump drying machine, which includes a drum 11 having an inner cavity, and a drying component is installed in the drum 11.
[0030] Specifically, the drying component includes an air duct component, a heat pump system component and a heat exchanger 40 .
[0031] The air duct assembly includes a hot air input channel 21 and an exhaust gas exhaust channel 22. The hot air input channel 21 has a first air inlet 23 and a first air outlet 24. The first air outlet 24 is connected to the inner cavity of the drum 11. The exhaust gas exhaust channel 22 has a second air inlet 25 and a second air outlet 26. The second air inlet 25 is connected to the inner cavity of the drum 11. Figure 1 As shown, the hot air input channel 21 is connected to the upper part of the drum 11, the exhaust gas discharge channel 22 is connected to the lower part of the drum, and the inner cavity of the drum 11 is used to put materials.
[0032] The exhaust gas discharge channel 22 is provided with a fan 27 so that the airflow flows in from the first air inlet 23 of the hot air input channel 21 and flows to the second air outlet 26 of the exhaust gas discharge channel 22 after passing through the inner cavity of the drum 11. It can be understood that when the fan 27 is turned on, the airflow enters the hot air input channel 21 through the first air inlet 23, then enters the drum 11, and finally flows to the exhaust gas discharge channel 22 and is discharged from the second air outlet 26.
[0033] The heat pump system component includes a compressor 31, a condenser 32, a throttling element 33 and an evaporator 34 that form a refrigerant cycle. The condenser 32 is arranged in the hot gas input channel 21 to heat the airflow flowing into the hot gas input channel 21. The evaporator 34 is arranged in the exhaust gas discharge channel 22 to absorb the residual heat of the airflow flowing out of the exhaust gas discharge channel 22. The heat pump system component is a prior art. The refrigerant runs in a circulation loop connected by the compressor 31, the condenser 32, the throttling element 33 and the evaporator 34. The condenser 32 performs heating. The condenser 32 is arranged in the hot gas input channel 21 to heat the inflowing airflow. The heated fresh air can heat and dry the materials in the drum 11 and take away moisture. After becoming exhaust gas, it is discharged from the exhaust gas discharge channel 22. The evaporator 34 of the heat pump system component can absorb the residual heat in the exhaust gas. The refrigerant cycle transfers the residual heat to the condenser 32 to heat the fresh air after natural heat exchange, so that it is further heated.
[0034] The heat exchanger 40 has a first heat exchange unit and a second heat exchange unit for mutual heat exchange. The first heat exchange unit is arranged in the exhaust gas exhaust channel 22, and the second heat exchange unit is arranged in the hot gas input channel 21, so as to perform heat exchange between the airflow flowing out of the exhaust gas exhaust channel 22 and the airflow flowing into the hot gas input channel 21.
[0035] In this embodiment, the heat exchanger 40 is a composite phase change heat exchanger, such as a heat pipe heat exchanger. The first heat exchange unit and the second heat exchange unit are respectively a first heat exchange end 41 and a second heat exchange end 42 disposed at two ends. The first heat exchange end 41 is disposed in the exhaust gas discharge channel 22. Specifically, the first heat exchange end 41 is disposed between the second air inlet 25 and the evaporator 34, so that the airflow flowing into the second air inlet 25 first passes through the first heat exchange end 41 and then flows to the evaporator 34. The second heat exchange end 42 is disposed in the hot air input channel 21. Specifically, the second heat exchange end 42 is disposed between the first air inlet 23 and the condenser 32, so that the airflow flowing into the first air inlet 23 first passes through the second heat exchange end 42 and then flows to the condenser 32.
[0036] It can be understood that after the drum heat pump drying machine is in operation, the first heat exchange end 41 arranged in the exhaust gas discharge channel 22 absorbs the residual heat in the exhaust gas, and then exchanges the heat to the second heat exchange end 42 to heat the airflow. The first heat exchange end 41 is arranged at the air intake front end of the evaporator 34. The residual heat in the exhaust gas has just been discharged from the exhaust gas discharge channel 22. At this time, the residual heat is relatively large. The first heat exchange end 41 of the heat exchanger 40 can exchange the residual heat to the second heat exchange end 42 to the greatest extent. At this time, the fresh air flow first passes through the second heat exchange end 42 for preheating, and then passes through the condenser 32 for the second heating through the heat pump system components. The heated and heated fresh air flows through the turning material in the inner cavity of the drum 11, heats the material and takes away the moisture therein, and becomes the exhaust gas discharge. At the same time, the heat pump system components absorb the heat of the exhaust gas, so that the heat can be recovered and reused repeatedly. In this embodiment, a heat exchanger and a heat pump system component are used at the same time, and the waste heat of the exhaust gas is utilized through the heat exchanger and the evaporator at two stages, thereby increasing the heating speed of the drum drying, improving the drying effect, reducing thermal pollution emissions, and helping to improve the working environment.
[0037] In some embodiments, the first air inlet 23 of the hot air input channel 21 is provided with a first filter device 51, and the first filter device 51 is arranged at the air intake front end of the second heat exchange end 42, so that the airflow passes through the first filter device 51 before flowing to the second heat exchange end 42. In this way, the fresh air can be purified first, then heated, and then sent to the drum to dry the material, and the purified fresh air can reduce the pollution to the material. Of course, a second filter device 52 can be installed at the second air inlet 25 of the exhaust gas discharge channel 22, so that the airflow passes through the second filter device 52 before flowing into the exhaust gas discharge channel 22. It can be understood that when the heated fresh air dries the material in the drum, the exhaust gas will be mixed with debris and other sundries. At this time, it can be processed by the second filter device 52 first to avoid affecting the operation of the heat exchanger 40 and the evaporator 34, and also to avoid exhaust gas discharge and polluting the environment. The first filter device 51 and the second filter device 52 can select filter cotton or conventional filter structures in the field.
[0038] In some other embodiments, an auxiliary heater 61 is installed at the first air outlet 24 of the hot air input channel 21. In some cases, in order to increase the drying efficiency of the drum heat pump integrated dryer, an auxiliary heater 61 can be added to further heat the heated fresh air and enhance the drying effect.
[0039] The above-mentioned integrated drum heat pump dryer integrates the heat exchanger and heat pump system components with the drum drying, which greatly reduces the workload and maintenance difficulty, and reduces the equipment cost and floor space.
[0040] Embodiment 2
[0041] In order to increase the waste heat utilization efficiency of the drum heat pump integrated dryer, enhance the drying effect and increase the drying amount, the difference from the first embodiment is that two drying components are provided in this embodiment and are distributed on the left and right, such as Figure 2 As shown, the two drying components are arranged on the left and right sides of the drum respectively. It should be noted that Figure 2 The two drying components shown in the figure are one arrangement mode. In other embodiments, the two drying components can be arranged on the back of the drum and distributed on the left and right.
[0042] Specifically, the two hot air input channels 21 are interconnected at the first air outlet 24 and share the first air outlet 24, which is connected to the inner cavity of the drum 11 to supply hot air to the inner cavity of the drum 11. The two waste gas discharge channels 22 are interconnected at the second air inlet 25 and share the second air inlet 25, which is connected to the inner cavity of the drum 11 to discharge waste gas from the inner cavity of the drum 11.
[0043] Embodiment 3
[0044] Reference Figure 3 The difference between this embodiment and the first embodiment is that the heat exchanger 40 is a partition-type heat exchanger, wherein the first heat exchange unit and the second heat exchange unit are respectively the first heat exchange channel and the second heat exchange channel arranged in a cross-flow manner, the first heat exchange channel is arranged in the exhaust gas exhaust channel 22, and the second heat exchange channel is arranged in the hot gas input channel 21, so as to perform heat exchange between the airflow of the exhaust gas exhaust channel 22 and the airflow of the hot gas input channel 21. Figure 3 The internal structure of the heat exchanger 40 is not cut away. The partition wall heat exchanger is a mature product of the prior art. Those skilled in the art can Figure 3 and implemented as described in the specification.
[0045] Specifically, the first heat exchange flow channel is arranged between the second air inlet 25 and the evaporator 34, so that the airflow flowing into the second air inlet 25 first passes through the first heat exchange flow channel and then flows to the evaporator 34. The second heat exchange flow channel is arranged between the first air inlet 23 and the condenser 32, so that the airflow flowing into the first air inlet 23 first passes through the second heat exchange flow channel and then flows to the condenser 32.
[0046] It can be understood that after the drum heat pump dryer is put into operation, the airflow inside the first heat exchange channel of the heat exchanger 40 and the airflow inside the second heat exchange channel are heat exchanged, and the first heat exchange channel arranged in the exhaust gas discharge channel 22 absorbs the residual heat in the exhaust gas, and then exchanges the heat to the second heat exchange channel to heat the airflow. The first heat exchange channel is arranged at the front end of the air intake of the evaporator 34. The residual heat in the exhaust gas has just been discharged from the exhaust gas discharge channel 22. At this time, the residual heat is relatively large. The first heat exchange channel of the heat exchanger 40 can exchange the residual heat to the second heat exchange channel to the greatest extent. At this time, the fresh air flow is first filtered through the first filter device 51, enters the hot air input channel, and then flows to the second heat exchange channel for preheating to obtain the first heating, and then flows through the condenser 32 for the second heating through the heat pump system components. The heated and heated fresh air flows through the turning material in the inner cavity of the drum 11, heats the material and takes away the moisture therein, and becomes exhaust gas emission. The exhaust gas is filtered through the second filter device 52, enters the exhaust gas discharge channel 22, and then flows to the first heat exchange channel of the heat exchanger 40, exchanges the waste heat of the exhaust gas to the second heat exchange channel, and then flows through the evaporator 34 for discharge, and the heat pump system components absorb the heat of the exhaust gas at the same time.
[0047] The embodiments of the present application are described in detail above in conjunction with the accompanying drawings, but the present application is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the technical field without departing from the purpose of the present application.
Claims
1. A drum heat pump drying machine, characterized in that: The drum comprises an inner cavity, wherein the drum is provided with at least one drying component, wherein the drying component comprises An air duct assembly, the air duct assembly comprising a hot air input channel and an exhaust air exhaust channel, the hot air input channel having a first air inlet and a first air outlet, the first air outlet being connected to the inner cavity of the drum, the exhaust air exhaust channel having a second air inlet and a second air outlet, the second air inlet being connected to the inner cavity of the drum, and the exhaust air exhaust channel being provided with a fan so that air flows from the first air inlet of the hot air input channel and flows to the second air outlet of the exhaust air exhaust channel after passing through the inner cavity of the drum; A heat pump system component, the heat pump system component comprising a compressor, a condenser, a throttling element and an evaporator forming a refrigerant cycle, the condenser being arranged in the hot gas input channel to heat the airflow flowing into the hot gas input channel, and the evaporator being arranged in the exhaust gas discharge channel to absorb the residual heat of the airflow flowing out of the exhaust gas discharge channel; and A heat exchanger, wherein the heat exchanger has a first heat exchange unit and a second heat exchange unit for exchanging heat with each other, wherein the first heat exchange unit is arranged in the exhaust gas exhaust channel, and the second heat exchange unit is arranged in the hot gas input channel, so as to perform heat exchange between the airflow flowing out of the exhaust gas exhaust channel and the airflow flowing into the hot gas input channel.
2. The drum heat pump drying machine according to claim 1, characterized in that: The heat exchanger is a composite phase change heat exchanger, wherein the first heat exchange unit and the second heat exchange unit are respectively a first heat exchange end and a second heat exchange end which are arranged at two ends, the first heat exchange end is arranged at the exhaust gas discharge channel, and the second heat exchange end is arranged at the hot gas input channel, so as to perform heat exchange between the airflow in the exhaust gas discharge channel and the airflow in the hot gas input channel.
3. The drum heat pump drying machine according to claim 2, characterized in that: The second heat exchange end is arranged between the first air inlet and the condenser, so that the airflow flowing into the first air inlet first passes through the second heat exchange end and then flows to the condenser; the first heat exchange end is arranged between the second air inlet and the evaporator, so that the airflow flowing into the second air inlet first passes through the first heat exchange end and then flows to the evaporator.
4. The drum heat pump drying machine according to claim 1, characterized in that: The heat exchanger is a partition-type heat exchanger, and the first heat exchange unit and the second heat exchange unit are respectively the first heat exchange channel and the second heat exchange channel arranged in cross-flow. The first heat exchange channel is arranged in the exhaust gas discharge channel, and the second heat exchange channel is arranged in the hot gas input channel, so as to perform heat exchange between the airflow in the exhaust gas discharge channel and the airflow in the hot gas input channel.
5. The drum heat pump drying machine according to claim 4, characterized in that: The second heat exchange channel is arranged between the first air inlet and the condenser, so that the airflow flowing into the first air inlet first passes through the second heat exchange channel before flowing to the condenser; the first heat exchange channel is arranged between the second air inlet and the evaporator, so that the airflow flowing into the second air inlet first passes through the first heat exchange channel before flowing to the evaporator.
6. The drum heat pump drying machine according to claim 3 or 5, characterized in that: The first air inlet of the hot air input channel is provided with a first filter device, and the first filter device is arranged at the air inlet front end of the second heat exchange unit, so that the airflow passes through the first filter device before flowing to the second heat exchange unit; the second air inlet position of the exhaust gas exhaust channel is installed with a second filter device, so that the airflow passes through the second filter device before flowing into the exhaust gas exhaust channel.
7. The drum heat pump drying machine according to claim 1, characterized in that: An auxiliary heater is installed at the first air outlet position of the hot air input channel.
8. The drum heat pump drying machine according to any one of claims 1 to 5, characterized in that: The drying components are provided with two and are distributed on the left and right.
9. The drum heat pump drying machine according to claim 8, characterized in that: The two hot air input channels are interconnected at the first air outlet and share one first air outlet, and the first air outlet is connected to the inner cavity of the drum to supply hot air into the inner cavity of the drum.
10. The drum heat pump drying machine according to claim 8, characterized in that: The two exhaust gas discharge channels are interconnected at the second air inlet and share one second air inlet, and the second air inlet is connected to the inner cavity of the drum to discharge the exhaust gas in the inner cavity of the drum.