CN107497815B

CN107497815B - Ventilation cabinet

Info

Publication number: CN107497815B
Application number: CN201710939219.1A
Authority: CN
Inventors: 阮红正; 唐光野; 卢丙利
Original assignee: Yishi Energy Saving Technology Shanghai Co ltd
Current assignee: Yishi Energy Saving Technology Shanghai Co ltd
Priority date: 2017-10-11
Filing date: 2017-10-11
Publication date: 2020-08-07
Anticipated expiration: 2037-10-11
Also published as: CN107497815A; WO2019071864A1

Abstract

The invention provides a fume hood. The fume chamber may include a chamber body 100 with an opening 101 opened at a front side, and may further include an exhaust port 201, an air supplement passage 301, and a guide plate 400. Wherein, the air outlet 201 is installed at the top of the cabinet 100 near the rear side, and the air supply channel 301 may include an air supply opening 302; the air supply opening 302 is installed at the lower edge of the cabinet body opening 101, the guide plate 400 is erected at the rear side of the inner cavity of the cabinet body 100, and a plurality of through holes 401 are formed in the guide plate 400. In addition, the side wall of the cabinet 100 is a hollow structure, and the air supplement channel 301 is communicated with the air supplement inlet 303 and the air supplement opening 302 along the side wall. The ventilation cabinet provided by the invention can eliminate potential safety hazards and prevent harmful gas in the cabinet from overflowing, and has the characteristics of simple structure and low manufacturing cost.

Description

Ventilation cabinet

Technical Field

The invention relates to equipment, in particular to a fume hood.

Background

The fume hood (also called as fume hood or exhaust hood) is used for capturing, containing and removing waste gas and harmful gas, creating a safe working environment and preventing users from inhaling the waste gas or the harmful gas to cause harm to life and health. The traditional fume hood is connected with an exhaust fan at an exhaust outlet, or the exhaust outlet is connected with an exhaust air duct of a large-scale exhaust fan of a building, air in a working cavity of the fume hood is exhausted by utilizing the suction effect of the exhaust fan, ambient air is introduced from a front opening of the fume hood, and meanwhile, the high-power fan is used for exhausting air in the working cavity to contain and treat harmful substances in the air. Under the design philosophy of traditional fume hoods, the higher the amount of wind that is fed in from the front opening, the more effective the fume hood is in its control and discharge functions of harmful substances in the air, so it is necessary to make up a large amount of air through the heating, ventilating and air conditioning system of the building to the space in which the fume hood is used, for example a laboratory, in place of ambient air drawn into the working chamber of the fume hood. Since the air to be supplied to the laboratory is part of the ambient air supplied to the laboratory, it must be treated to the same degree of ambient air to ensure the comfort and safety of the laboratory working environment, and therefore the use of conventional fume hoods generally results in a great energy consumption of the building in which the laboratory is located, etc. In addition, the above-described air flow pattern often causes a vortex-type air structure to be generated in the vicinity of the air outlet and the front opening of the hood. In this case, regardless of the velocity of the air drawn through the front opening, the air flow structure within the working chamber, if there are turbulence and eddies, can cause the risk of air within the working chamber escaping from the fume hood working chamber outside the front opening, posing a threat to the health and safety of the experimenter.

Patent document No. CN106140769A discloses a ventilation hood that can reduce the energy consumption of an air conditioner, suppress the overflow of harmful substances in a working chamber, and has low installation cost and high consistency of product quality. The air supplementing system is connected with an air supplementing channel of a building and used for supplementing air to a working cavity of the fume hood, and the air supplementing system is provided with at least one air supplementing opening at the upper part and the lower part of a cabinet body respectively. Three air supply ports and corresponding positions are also specifically disclosed. As shown in fig. 1, a first air supply opening a1 is provided above the front opening of the fume hood, a second air supply opening a2 is provided below the front opening, and a third air supply opening A3 is provided above the cabinet and in front of the front wall.

Although the fume chamber has better energy-saving effect, the following defects are also found: when the ventilation cabinet works, the exhaust system performs suction, air in the ventilation cabinet flows along the hollow arrow shown in the figure, and the air supplementing system supplies air through the air supplementing opening to provide supplementing air; at the same time, indoor air near the exterior front opening of the fumehood is drawn through the front opening into the working chamber as make-up air. At this time, when the air supplement is provided at one or both of the upper two air supplement ports, a small vortex is formed between the upper air supplement air flow and the front opening supplement air (at the position indicated by the circle in fig. 1) due to the guidance of the air flow by the suction of the exhaust system and the guidance of the air flow by the air supplement of the air supplement system, and there is a possibility that the air in the cabinet is slightly entrained into the small vortex and is not sucked into the exhaust system. If there is an external disturbance airflow, such as a person walking over or an arm of an operator coming in and out, the balance of the small vortex is broken, and a small amount of harmful gas involved in the small vortex may overflow. In addition, the ventilation cabinet is provided with three air supply ports, so that the production process is complex and the manufacturing cost is high; meanwhile, the ventilation cabinet can achieve the safety and energy-saving effects only by accurately controlling the air output of the three air supply ports, and the control precision of the air supply system is also highly required.

There is a strong book of research and application of air curtain type exhaust hood (Ministry of university of south China, 2002, 3 months, 16 th volume, 1 st period: 44-49) in research and application of air curtain type exhaust hood, et al, which records that a blowing and sucking air curtain technology is introduced on the basis of the original exhaust hood, and develops a novel blowing and sucking air curtain type exhaust hood (as shown in figure 2), and thinks that the novel exhaust hood has the advantages of energy conservation, comfortable operation and good control effect. In fact, the structure that relies on the air curtain to separate the internal environment from the external environment has very high requirements on the environment where the exhaust cabinet is located, and the air curtain is greatly affected by the walking of personnel, heat convection, the air blowing direction of the air conditioner, cross air flow generated by an indoor air supply and exhaust system and the like, which may cause the air curtain to break and fail. Because the air curtain is close to the operator, once the air curtain breaks, the air curtain carrying the gas in the cabinet is easy to cause serious consequences harmful to life and health to the operator. In addition, when the operator uses the air curtain type exhaust cabinet, the air flow sent out by the air supply opening is simultaneously influenced by the pushing of the air supply opening and the suction of the air outlet to form an air curtain. When the operator uses the exhaust cabinet, the arm of the operator necessarily passes through the air curtain, and at the moment, the air supply flow from bottom to top is likely to overflow to the position of the operator along the lower side of the arm of the operator. That is, after the air from the air supply opening is polluted by the air in the cabinet, the air possibly overflows from the exhaust cabinet, and the air from the air supply opening is from bottom to top and directly faces the nose of an operator, once the air curtain of the ventilation cabinet is broken, the air containing the pollutants can be directly sent into the respiratory tract of the operator, and very serious safety hazard is caused.

Disclosure of Invention

The embodiment of the invention can provide the ventilation cabinet, can eliminate potential safety hazards, prevents harmful gas in the cabinet from overflowing, and has the characteristics of simple structure and low manufacturing cost.

The embodiment of the invention provides a ventilation cabinet, which comprises a cabinet body with an opening on the front side, and further comprises:

the air outlet is communicated with the cabinet body and is arranged at the top of the cabinet body close to the rear side;

an air supply channel comprising an air supply opening; and the number of the first and second groups,

a guide plate standing in the cabinet body and close to the rear side, the guide plate comprises a base plate and an inclined part, gaps are reserved between the lower end of the base plate and the bottom of the cabinet body and between the lower end of the inclined part and the base plate,

wherein,

the air supply opening is positioned below the opening, and the inclined part is arranged to cover the air exhaust opening when the front end of the inclined part is seen from the lower part.

Preferably, the center of the air outlet is positioned in the middle of the left side and the right side in the cabinet body when viewed from the front side; the center of the air outlet is positioned at the rear side in the cabinet body when viewed from the left side or the right side.

Preferably, the center of the air outlet is located between the front and rear sides of the cabinet body and one quarter of the distance from the rear side when viewed from the left or right side.

Preferably, the width of the air supply opening is larger than or equal to the width of the cabinet body when viewed from the front side, so that the air supply opening extends towards the left end and the right end of the opening and covers the opening.

Preferably, the top side and the rear side of the air supply opening are connected in an arc shape or a chamfer shape when viewed from the left side or the right side, so that the air supply opening supplies air upwards and backwards.

Further, the arc is a quarter arc.

Preferably, the outer side of the air supply opening and the inner side of the front part of the cabinet body are positioned in the same vertical plane, so that the upward air supply airflow sent out through the air supply opening covers the opening of the cabinet body.

Preferably, a guide plate is arranged in the air supply opening, and the guide plate divides the air supply opening into an outer air supply opening pointing upwards and an inner air supply opening pointing into the cabinet body.

Furthermore, the cross section of the guide plate is arc-shaped and is used for guiding the direction of the air supply flow sent out through the inner side air supply opening.

Furthermore, the lower end part of the guide plate is positioned in the air supplementing channel, and the lower end part is used for distributing air supplementing air quantities of the outer side air supplementing opening and the inner side air supplementing opening.

Preferably, the guide plate base plate is provided with through holes, the through holes are uniformly distributed along the horizontal width direction, and the ratio of the hole area to the unit area is gradually reduced from bottom to top.

Preferably, the distance between the through holes is gradually increased from bottom to top, or the hole area of the through holes is gradually reduced.

Furthermore, the through holes arranged on the guide plate substrate are narrow at the top and wide at the bottom and are radially arranged when viewed from the front side.

Furthermore, the guide plate base plate also comprises an upper guide plate part and a lower guide plate part, and a gap is reserved between the lower guide plate part and the upper guide plate part.

Preferably, an inclined plate is arranged above the front side in the cabinet body; the upward extending direction of the inclined plate and the upward extending direction of the inclined part form an included angle.

Preferably, the wind supplementing device further comprises a wind supplementing fan communicated with the wind supplementing channel, and the wind supplementing fan is a power-adjustable fan.

Furthermore, the air supply fan is arranged in the air supply channel.

Preferably, the air supply device further comprises an air supply valve communicated with the air supply channel, and the air supply valve is a variable-opening valve.

Preferably, the side wall and/or the lower wall of the fume hood are hollow structures, and the air supplementing channel is arranged on the side wall and/or the lower wall of the cabinet body.

Preferably, the method further comprises the following steps:

the sliding door is arranged at the opening and can slide along the opening and is used for adjusting the opening area of the opening; and

a top passage which communicates the inside of the cabinet body with the outside of the cabinet body, an outlet of the top passage is positioned in the cabinet body,

wherein, the fume chamber is set up as when the air exit exhausts, 40% -69% of the air output is supplemented by the air current that the air supplement mouth sends out.

Preferably, the outer side wall of the air supply opening and the outer side wall of the sliding door are positioned in the same vertical plane, so that upward air supply airflow sent out through the air supply opening covers the opening of the cabinet body.

Further, still include:

a position sensor for detecting a position of the sliding door; and the number of the first and second groups,

a control unit connected with the position sensor,

the guide plate further comprises an adjusting plate, the adjusting plate is hinged with the guide plate, and the control unit controls the adjusting plate to rotate according to detection information of the position sensor and is used for adjusting air volume distribution of the inner air supply port and the outer air supply port which are separated by the guide plate.

The embodiment of the invention also provides a control method of the fume hood, which comprises the following steps:

when the opening degree of the opening is 0% -4% due to the movement of the sliding door, the free end of the adjusting plate is set to be in contact with the bottom plate of the air supply channel, namely the outer air supply port is closed;

when the opening degree of the opening is 5% -60% due to the movement of the sliding door, the distance between the free end of the adjusting plate and the bottom plate of the air supplementing channel is set to be less than or equal to 40% of the height of the air supplementing channel;

when the opening degree is 61% -100% due to the movement of the sliding door, the distance between the free end of the adjusting plate and the bottom plate of the air supplementing channel is set to be less than or equal to 70% of the height of the air supplementing channel.

Furthermore, when the fume hood exhausts air, 40% -69% of the exhaust air quantity is supplemented by the air flow sent out by the air supply port.

According to the fume hood provided by the embodiment of the invention, the potential safety hazard that all exhaust air flow exhausted outside the fume hood is supplemented by active supplement air flow of an air supplement system or passive supplement air flow outside the fume hood is eliminated, and the air supplement port is arranged only below the opening of the hood body, and the proportion of the exhaust air quantity, the active supplement air quantity and the passive supplement air quantity (air flow entering the fume hood under the influence of negative pressure formed by exhaust air when the exhaust system exhausts from the fume hood) is controlled, so that one-way air flow always facing the exhaust port in the hood is formed at the opening of the fume hood, the safety of a user can be ensured, and the harmful gas in the hood can be effectively prevented from overflowing. In addition, compared with the prior art that the air supply quantity of the three air supply ports needs to be accurately controlled when the three air supply ports are arranged, otherwise, the risk of loss is caused once the balance effect and the safety are lost, the structure is simpler compared with a plurality of air supply ports due to the fact that only one air supply port is arranged, the production cost is lower, and the safety factor is increased.

Drawings

FIG. 1 illustrates a prior art fumehood;

FIG. 2 illustrates another prior art fume hood;

fig. 3 is a schematic structural diagram of a fume hood according to an embodiment of the present invention;

FIG. 4 is a top view of the schematic structure shown in FIG. 3;

FIG. 5 is a schematic cross-sectional view of an air supply port;

FIG. 6 is a schematic cross-sectional view of an air supply opening of a fumehood according to another embodiment of the present invention;

fig. 7 is a schematic view of a baffle structure of a fume hood according to an embodiment of the present invention;

FIG. 8 is a schematic structural view of a fumehood according to another embodiment of the present invention;

fig. 9 is a schematic perspective view of a fume hood according to another embodiment of the present invention;

fig. 10-1 to 10-3 are schematic diagrams illustrating an air volume control state of a fume hood according to an embodiment of the present invention;

FIGS. 11-1 and 11-2 show a fumehood Q according to an embodiment of the present invention_{Supplement device}＝40％×Q_{Row board}A perspective view and a side view of the leakage rate detection graph;

FIGS. 11-3 and 11-4 show a fumehood Q according to an embodiment of the present invention_{Supplement device}＝40％×Q_{Row board}A time airflow velocity flow chart and an airflow velocity section chart;

fig. 12-1 and 12-2 show a fume hood Q according to an embodiment of the present invention_{Supplement device}＝45％×Q_{Row board}A perspective view and a side view of the leakage rate detection graph;

fig. 12-3 and 12-4 show a fume hood Q according to an embodiment of the present invention_{Supplement device}＝45％×Q_{Row board}A time airflow velocity flow chart and an airflow velocity section chart;

FIGS. 13-1 and 13-2 show a fumehood Q according to an embodiment of the present invention_{Supplement device}＝60％×Q_{Row board}A perspective view and a side view of the leakage rate detection graph;

FIGS. 13-3 and 13-4 show a fumehood Q according to an embodiment of the present invention_{Supplement device}＝60％×Q_{Row board}A time airflow velocity flow chart and an airflow velocity section chart;

fig. 14-1 and 14-2 show a fume hood according to an embodiment of the present inventionQ_{Supplement device}＝69％×Q_{Row board}A perspective view and a side view of the leakage rate detection graph;

FIGS. 14-3 and 14-4 show a fume hood Q according to an embodiment of the present invention_{Supplement device}＝69％×Q_{Row board}A time airflow velocity flow chart and an airflow velocity section chart;

fig. 15-1 and 15-2 show a fume hood Q according to an embodiment of the present invention_{Supplement device}＝70％×Q_{Row board}A perspective view and a side view of the leakage rate detection graph;

FIGS. 15-3 and 15-4 show a fumehood Q according to an embodiment of the present invention_{Supplement device}＝70％×Q_{Row board}A time airflow velocity flow chart and an airflow velocity section chart.

Detailed Description

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it is not intended that features of the invention be limited to only those embodiments. On the contrary, the invention is described in connection with the embodiments for the purpose of covering alternatives or modifications that may be extended based on the claims of the present invention. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The invention may be practiced without these particulars. Moreover, some of the specific details have been left out of the description in order to avoid obscuring or obscuring the focus of the present invention.

In the following description, the terms of orientation such as "upper", "lower", "left", "right", "top", "bottom", "front", "rear", "inside" and "outside" used in the fume hood are defined based on the spatial position of the fume hood when used by a laboratory worker, and should not be construed as limiting the present invention.

Fig. 3 is a schematic structural diagram of a fume hood according to an embodiment of the present invention. As shown in fig. 3, the ventilation hood may include a cabinet 100 having an opening 101 formed at a front side thereof, an air outlet 201, an air supplement passage 301, and a guide plate 400. Wherein, the air outlet 201 communicated with the inside of the cabinet 100 is arranged at the top of the cabinet 100 near the rear side. The air supplement channel 301 may include an air supplement opening 302, wherein the air supplement opening 302 is disposed below the cabinet opening 101, and the air supplement channel 301 is disposed at the bottom of the cabinet 100. The baffle 400 is erected at the rear side in the cabinet 100, and includes a substrate and an inclined portion 404, wherein the substrate is vertically erected, and the inclined portion 404 is located above the substrate and inclined toward the air outlet 201 from bottom to top; the upper end of the inclined part 404 is close to the top of the cabinet 100, the lower end is close to the base plate, and a gap 405 is left between the end part of the inclined part 404 close to the top of the cabinet 100 and the top of the cabinet 100; in the bottom view, the inclined portion 404 covers the air outlet 201. Also, a gap 405 or aperture is left between the deflector base plate and the bottom of the cabinet 100, between the angled portion 404 and the base plate, to allow airflow to pass through the gap 405 or aperture.

The air exhaust means exhausting air in the cabinet from the inside of the fume hood. In the embodiment of the present invention, all the air in the fume chamber is exhausted through the exhaust opening 201. When the fume hood provided by the embodiment of the invention exhausts, the supplementary gas is supplemented into the hood through the following two ways: one is active air supplement, namely supplement air is actively sent into the cabinet by an air supplement system; the other is passive air supplement, namely supplementing air is sucked or pumped into the cabinet under the influence of negative pressure formed by the exhausted air. In working condition, the air exhausting quantity and air supplementing quantity are in balance state, i.e. air exhausting quantity (Q)_{Row board}) Active air quantity (Q) supplement_{Supplement device}) + passive air supply (Q)_{Suction device})。

In the fume hood provided by this embodiment, the air outlet 201 may be externally connected to an exhaust system of a laboratory in which the fume hood is located, or externally connected to an exhaust system of a building in which the fume hood is located, so as to finally exhaust the gas in the fume hood to the outside of the laboratory or the building; similarly, the air supply channel 301 may be externally connected to an air supply system of a laboratory where the fume hood is located, or externally connected to an air supply system of a building where the fume hood is located. When the fume hood works, under the action of the exhaust system, air in the fume hood is exhausted through the exhaust port 201, so that negative pressure is generated in the cabinet body 100 of the fume hood; meanwhile, under the action of the air supply system, outside fresh air is sent into the cabinet body along the air supply channel 301 through the air supply opening 302 positioned below the opening 101 of the cabinet body 100, so as to form air supply airflow. Under the suction action of the exhaust system, a part of air supplement flow carries gas or particles in the cabinet to pass through a gap between the base plate of the guide plate 400 and the bottom of the cabinet body 100 and a gap 405 between the inclined part 404 and the base plate of the guide plate 400, reaches the exhaust port 201 along a channel between the guide plate 400 and the rear side wall of the cabinet body 100, and is finally exhausted to the exhaust system through the exhaust port 201; the other part of the air supply air flow is influenced by the negative pressure of the air exhaust, is sent out from the air supply opening 302 and then directly flows upwards with the air or particles in the cabinet to the air exhaust opening 201 and then is exhausted out of the ventilation cabinet. At this time, the volume of the make-up air flow is set to be smaller than the volume of the exhaust air, and the actively made-up make-up air flow is insufficient to fill the space left by the original air in the cabinet, so that the air outside the cabinet around the opening 101 of the cabinet 100 is also influenced by the suction of the exhaust system, and is entrained by the make-up air flow sent from the make-up air port 302 and flows to the exhaust port 201 together with the make-up air flow. With the above arrangement, the passive air supplement airflow entering the cabinet 100 from the outside of the cabinet 100 forms a unidirectional airflow from the outside to the inside at the opening 101, thereby ensuring that no air in the cabinet overflows from the opening 101 of the cabinet 100 to the outside of the cabinet 100.

Therefore, in the ventilation hood provided in this embodiment, only the air supply opening 302 for supplying active air supply to the cabinet body 100 is provided, so that the active air supply amount and the exhaust air amount form Q_{Supplement device}＝(40％～69％)×Q_{Row board}The relationship of (1); wherein Q is_{Supplement device}For active supply of air quantity, Q, through the supply opening 302_{Row board}Is the amount of exhaust air discharged through the exhaust port 201.

When the fume hood works, particles are generated in the cabinet body 100 as a working area for experimenters to carry out chemical experiments, and the particles are possibly harmful to human bodies. When the exhaust system is in operation, suction is created in the cabinet 100, creating a traction effect on the particles, which may be visually referred to as "pulling"; when the air supply system is in operation, the air supply flow from the air supply opening 302 will push the particles to move along with the flow direction of the air flow, which may be referred to visually as "pushing".

Fig. 4 is a top view of the schematic structure shown in fig. 3. Wherein 510 denotes the width direction; and 520, the length direction. As shown in fig. 4, in the present embodiment, the air outlet 201 is cylindrical and is installed at a side of the top of the cabinet 100 away from the opening 101, that is, the center of the air outlet 201 is located at the rear side in the cabinet 100 when viewed from the left or right side; and the central axis thereof is located at or near the middle of the cabinet 100 in the width direction 510, that is, the center of the air outlet 201 is located at the middle of the left and right sides in the cabinet 100 when viewed from the front side. As shown in fig. 4, a is the width of the fume hood body 100, and the distance from the center of the air outlet 201 to either of the left and right sides of the fume hood is one half of the width of the fume hood body 100, i.e., a/2. In other embodiments, the air outlet 201 may be disposed in the middle of the cabinet 100 for better matching the space inside the cabinet 100, i.e. the distance from the center of the air outlet 201 to any side inside the cabinet 100 is one half of the width inside the fume hood 100. This arrangement enables the exhaust port 201 to efficiently perform the exhaust function.

In another embodiment of the present invention, the distance between the central axis of the air outlet 201 and the inner rear wall of the cabinet 100 in the length direction 520 is a quarter of the inner length of the cabinet 100, i.e. the center of the air outlet 201 is located in the front-rear side of the cabinet 100 and a quarter of the rear side when viewed from the left or right side. The positioning is beneficial to realizing the pulling effect of the exhaust fan, and the airflow is stable and difficult to generate turbulent flow.

As shown in fig. 3, the outside of the air supply opening 302 is located in the same vertical plane as the inside of the cabinet 100. This arrangement allows the flow of make-up air, and particularly the upward flow of make-up air, to be delivered through the make-up air opening 302 to cover the cabinet opening 101. In the present embodiment, the air supply opening 302 extends along the cabinet 100 in the width direction, and the width of the air supply opening 302 is equal to or greater than the width between the left side and the right side in the cabinet 100, so that the air supply flow sent by the air supply opening 302 covers the opening 101. As shown in fig. 3, the cross section of the air supply opening 302 perpendicular to the width direction is arc-shaped, that is, the top side and the rear side of the air supply opening 302 are arc-shaped when viewed from the left or right side; the air supply opening 302 is directed upward and rearward, so that the air supplied from the air supply opening 302 is directed upward and into the cabinet 100. In other embodiments, the cross-section of the air supply opening 302 may also be a quarter of a circular arc.

FIG. 5 is a schematic cross-sectional view of the air supply opening, as shown in FIG. 5, in the present embodiment, a guide plate 310 is disposed in the air supply opening 302, and the guide plate 310 divides the air supply opening 302 into an outer air supply opening 311 and an inner air supply opening 312. in addition, the cross-section of the guide plate 310 perpendicular to the width direction is arc-shaped. in other embodiments, the guide plate 310 may also be in an inverted L shape or a sickle shape. preferably, the guide plate 310 substantially divides the air supply opening 302 into two parts with equal area along the horizontal direction. the lower end 313 of the guide plate 310 is disposed in the air supply passage 301. those skilled in the art can understand that adjusting the position of the lower end 313 can control the distribution of the air supply amount of the outer air supply opening 311 and the inner air supply opening 312. therefore, the guide plate 310 can change.

When the ventilation hood provided by this embodiment is in operation, the air supply airflow passes through the air supply channel 301, and then is divided into two airflows by the guide plate 310, and the two airflows flow to the inner air supply opening 312 and the outer air supply opening 311 respectively. The air quantity distribution ratio of the inner air supply port and the outer air supply port is determined by the distance between the lower end of the guide plate 310 and the bottom plate of the air supply channel 301. The larger the distance is, the larger the air volume (Q) of the outside air supply opening 311 is_{Supplement the external}) The larger the air flow rate (Q) of the inner side air supply port 312 is_{Supplement the interior}) The smaller; conversely, the smaller the distance, the smaller the air quantity (Q) of the outside air supply opening 311_{Supplement the external}) The smaller the inside air supply opening 312 air quantity (Q)_{Supplement the interior}) The larger; air quantity Q of air supply_{Supplement device}＝Q_{Supplement the interior}+Q_{Supplement the external}. The outer air supply opening 311 forms an upward air curtain, so that the influence of disturbance in a laboratory on the air flow organization in the cabinet body 100 is reduced; the air supply air is pushed from the inner side air supply opening 312, the exhaust system is pulled, the air supply air and the exhaust system form pushing and pulling together, harmful gas is sent between the guide plate 400 and the rear wall of the cabinet body 100, and finally the harmful gas is pumped away by the exhaust system. Under the suction action of the exhaust system, a 'guide groove' is formed between the guide plate 400 and the rear wall of the cabinet body 100, and air cannot flow towards the opening 101 after being captured in the 'guide groove', so that the air is completely exhausted from the exhaust outlet, and the safety is ensured.

The guide plate 310 in this embodiment restricts the airflow passing through in some directions when performing the guiding function, and causes a certain loss of the pressure of the airflow, and when it is designed to be arc-shaped, the pressure loss of the airflow passing through is small.

Fig. 6 is a schematic cross-sectional view of an air supply opening 302 of a fume hood according to another embodiment of the present invention. As shown in the figure, the cross section of the air supply opening 302 perpendicular to the width direction can also be chamfered, that is, the top side and the rear side of the air supply opening 302 are connected in a chamfered shape when viewed from the left side or the right side.

Fig. 7 is a schematic view of a baffle structure of a fume hood according to an embodiment of the present invention. As shown in fig. 7, preferably, the baffle 400 is provided with a plurality of through holes 401, and the through holes 401 located at the lower portion 402 of the baffle are uniformly distributed along the horizontal width direction; the through-holes 401 in the upper part 403 of the baffle have a decreasing ratio of hole area to unit area from bottom to top.

In other embodiments, the through holes 401 disposed in the upper portion 403 of the baffle have a gradually increasing distance from bottom to top, and are arranged sparsely, or the area of a single hole is gradually reduced. In another embodiment, the through holes 401 disposed on the upper portion 403 of the baffle are arranged from top to bottom in a radial manner in the width direction, that is, the through holes 401 are arranged in a manner that the top is narrower and the bottom is wider along the center when viewed from the front side.

In this embodiment, the lower deflector portion 402 and the upper deflector portion 403 are integrally formed to form a deflector substrate; the through holes 401 are arranged on the baffle base plate, and are arranged on the upper part 403 and the lower part 402 of the baffle. In other embodiments, the upper baffle portion 403 and the lower baffle portion 402 may be separate. Whether the upper portion 403 of the baffle and the lower portion 402 of the baffle are separately arranged or not, a gap 405 is preferably left between the lower portion 402 of the baffle and the upper portion 403 of the baffle to allow the air flow to pass through the baffle 400 along the gap 405 or the through hole 401 under the influence of the negative pressure formed between the baffle 400 and the rear wall of the cabinet 100 by the exhaust port 201, so as to achieve the function of controlling the air flow direction. When the ventilation hood provided by the embodiment works, the inside air supply opening 312 pushes pollutants with higher concentration to the lower part 402 of the guide plate by virtue of positive static pressure and kinetic energy of air supply, and the pollutants are sucked away by a negative pressure channel behind the guide plate after passing through the lower part 402 of the guide plate; the outside air supply opening 311 generates a section of air curtain which is vertically upward, and separates the air flow inside and outside the opening 101, so as to prevent the disturbance outside the cabinet or the 'cylindrical streaming effect' generated by the human body in front of the cabinet from influencing the air flow inside the cabinet body 100.

The cylindrical bypass is characterized in that when fluid flows around a cylinder, a flow cross section is contracted, the flow velocity is increased along the way, the pressure is reduced along the way, and due to the existence of viscous force, boundary layer separation can occur around the cylinder to form cylindrical bypass.

In some prior art fume hoods are designed to only passively replenish the exhaust air when exhausting, and all of the exhaust air is passively replenished by air from outside the hood and through the openings, i.e., all of the air flow must flow from the outside to the inside through the openings and be drawn into the hood. At this point, any physical obstruction or disturbance at or in front of the opening, such as a person walking in front of the opening, an operator blocking the opening, or an instrument placed in front of the opening, can cause the stability of the airflow structure within the cabinet to be compromised, resulting in a "cylindrical bypass effect". The stability of the airflow organization in the cabinet is damaged to generate turbulence, and the risk that the gas in the cabinet overflows out of the cabinet can be generated.

Fig. 8 is a schematic structural diagram of a fume hood according to another embodiment of the present invention. As shown in fig. 3 and 8, the baffle 400 is further provided with an inclined portion 404 connected to the upper portion 403 of the baffle near the top wall of the cabinet 100, and a gap 405 is left between the inclined portion 404 and the upper portion 403 of the baffle. As shown in fig. 8, an inclined plate 104 is arranged above the opening 101 in the fume hood; the upward extension of the inclined plate 104 forms an angle (not shown) with the upward extension of the inclined portion 404.

In general, in a fume hood in an operating state, a pollution source is generally placed on an inner bottom end surface of the cabinet 100, such as a beaker, a heating magnetic stirrer, and the like, so that the concentration of pollutants in the cabinet 100 is distributed in a height direction in the fume hood: the closer to the bottom of the cabinet 100, the higher the concentration, and the further away from the bottom of the cabinet 100 (e.g., the top of the cabinet 100), the lower the concentration. The air flow organization design concept in the fume chamber that this embodiment provided does:

1. by reasonably setting the size of the gap between the lower part 402 of the air deflector and the bottom of the cabinet body 100 and the sum of the hole areas of the through holes 401 arranged on the lower part 402 of the air deflector, the air quantity discharged to the air outlet 201 from the air outlet accounts for 60 percent of the air discharge quantity;

2. the air quantity discharged to the air outlet 201 from the air outlet accounts for 25 to 30 percent of the air discharge quantity by reasonably setting the size of a gap between the upper part 403 and the lower part 402 of the guide plate and the sum of the hole areas of the through holes 401 arranged on the upper part 403 of the guide plate;

3. the air quantity discharged to the air outlet 201 from the air outlet is 10-15% of the air discharge quantity by reasonably setting the size of the gap between the inclined part 404 of the air deflector 400 and the upper part 403 of the air deflector and the size of the gap between the inclined part 404 and the top of the cabinet body 100;

due to the fluid mechanics principle, the closer to the air outlet 201, the greater the negative pressure. The pressure loss of the lower part 402 of the deflector, which is far from the air outlet 201, due to the on-way resistance, is relatively small.

The design of the baffle 400 needs to comply with the above requirements and to meet the following characteristics:

1. the through holes 401 on the lower part 402 of the guide plate have larger or more dense holes, and the air flow passing requirement of 60 percent of exhaust volume is met. Meanwhile, the position of the opening can ensure that the wind speed on the surface passing through the lower part 402 of the guide plate in the width direction is uniform.

2. The through holes 401 on the upper part 403 of the guide plate are provided with smaller and smaller holes from bottom to top, the area of a single hole is smaller and smaller, the arrangement between rows is more and less, and the number of holes in each row is less and less, so as to ensure the requirement that the air volume entering the guide plate 400 is reduced progressively from bottom to top.

3. The angled portion 404 of the baffle 400 is spaced from the top of the cabinet 100 and from the upper portion 403 of the baffle 405. The size of the void 405 can be derived from CFD (english abbreviation of Computational Fluid Dynamics) Fluid analysis. Too large a gap may cause contaminants to rise directly to the top, bypassing the upper deflector portion 403 and lower deflector portion 402, creating turbulence at the top, increasing the risk of spillage outside the cabinet 100.

In another embodiment of the present invention, the air supply channel 301 is further communicated with an air supply fan, and the air supply fan is a power adjustable fan. In other embodiments, the air supply fan may also be disposed in the air supply channel 301. Further, the air supply channel 301 may further communicate with an air supply valve, which may be a variable-opening valve.

In another embodiment of the present invention, the lower wall of the ventilation hood is a hollow structure, and the air supplement channel 301 is disposed on the lower wall of the cabinet 100. In addition, the top wall of the cabinet 100 may also be a hollow structure. Therefore, the air supplement channel 301 may also pass through the top wall and the bottom wall of the cabinet 100. In other embodiments, the top wall, the bottom wall, and the side wall, which are hollow and effectively sealed, may be used as the air supply channel 301.

Fig. 9 is a schematic perspective view of a fume hood according to another embodiment of the present invention. As shown in fig. 9, this embodiment provides a fume hood, further comprising a sliding door 106 provided at the opening 101, the sliding door 106 being slidable along the opening 101 for adjusting an opening area of the opening 101; the fume hood further comprises a top passage 105, the top passage 105 communicates the inside of the cabinet body 100 with the external environment, one end of the top passage 105 is arranged outside the cabinet body 100 and can be arranged at the top of the cabinet body 100 to be used as an inlet; the other end is arranged in the cabinet body 100 and is used as an outlet. In addition, the outer side wall of the air supply opening 302 and the outer side wall of the sliding door 106 are positioned in the same vertical plane, so that the air supply airflow sent out through the air supply opening 302, particularly the upward air supply airflow, covers the cabinet body opening 101. In other embodiments, in order to make the sliding door 106 slide smoothly relative to the cabinet 100, a large gap tends to be left between the sliding door 106 and the cabinet 100. Therefore, controlling the gap to function as the top passage 105 is also one of the optional technical means, and has the advantages that the top passage 105 does not need to be separately arranged, and the structure is simplified.

When the fume hood of this embodiment is in operation, air in the top passage 105, which is located near one end of the exterior of the cabinet 100, is drawn from the exterior of the fume hood through the top passage 105 or a region corresponding to the top passage into the cabinet by the exhaust vents 201 to remove the contaminating air that may be present in the interior of the cabinet 100 on the upper front side. At this time, the top passage 105 is controlled to provide a small proportion of passive air supply amount, which is 5% -10% of the exhaust amount, into the cabinet, so that the greater intercepting capability of the polluted gas can be ensured, the risk that the polluted gas in the cabinet overflows out of the cabinet is eliminated, and no additional fan is needed to supply air into the cabinet through the top passage 105.

From another perspective, the top passageway 105 is provided as a means of stabilizing the airflow pattern within the cabinet. The internal physical structure of the fume hood determines that a vortex is generally generated at the top of the cabinet 100 near the opening 101, and the air in the vortex is difficult to be discharged. The top passageway 105 is arranged such that air drawn into the cabinet 100 through the top passageway 105 disrupts the aforementioned vortex and "pushes" the vortex-forming gases towards the baffle 400 and the exhaust 201, thereby preventing escape of the cabinet gases through the opening 101 and making the fume hood safer. It will be appreciated by those skilled in the art that the location of the vortex generation described above is just near the nose and mouth of the operator standing in front of the cabinet opening 101, and therefore the presence of a vortex at this location is most dangerous, especially when the sliding door 106 is in an open position.

By the design of the fume hood structure, for example, adjusting the position of the lower end 313 of the guide plate 310 in the air supply passage 301, or adjusting the height of the sliding door 106, when the fume hood provided by this embodiment is in operation, 40% to 69% of the air supply amount is provided by the air supply opening 302, and the remaining 31% to 60% is provided by other means. For example, in the present embodiment, 31% to 60% of the amount of the make-up air is provided by the cabinet door opening 101 and the top passage 105 together. The optimal state is that the air volume distribution ratio is as follows:

Q_{supplement device}＝60％×Q_{Row board}；

Q_{Door with a door panel}＝30％×Q_{Row board}；

Q_{Side wall}＝10％×Q_{Row board}；

Q_{Suction device}＝Q_{Door with a door panel}+Q_{Side wall}。

Wherein Q is_{Row board}For the amount of exhaust, Q_{Supplement device}For actively supplementing the air quantity, Q, delivered through the air supplementing opening 302_{Door with a door panel}In order to achieve the passive air supply quantity Q drawn into the cabinet 100 from the outside of the cabinet 100 through the opening 101_{Side wall}Is the passive supply air volume drawn into the cabinet 100 from outside the cabinet 100 through the top duct 105.

Therefore, the pollutants generated in the experiment are pumped out from the air outlet 201 through the air guide plate 400 and the negative pressure channel formed by the air guide plate 400 and the inner rear side wall of the cabinet body 100.

1. When the amount of contaminants present is of small or medium volume, the contaminants are drawn directly from the lower portion 402 of the baffle;

2. when the volume of contaminants is large, contaminants are pumped away from the lower baffle portion 402 and the upper baffle portion 403

3. When the volume of contaminants is excessive, contaminants that are not being drawn through the lower and

upper baffle portions

402, 403 rise to the top and are drawn through the upper and lower gaps of the angled portion 404 of the baffle 400.

In the above embodiment, the distribution of the amount of the supplementary air can be controlled by the position of the lower end 313 of the guide plate 310. In other embodiments, the adjusting plate 314 can be pivoted about a hinge by hinging the adjusting plate 314 to the guide plate 310, the adjusting plate 314 having a fixed end near the hinge and a free end at the other end. Thus, the function of controlling the distribution of the air supply quantity can be achieved by controlling the position of the free end of the adjusting plate 314. In addition, the adjusting plate 314 and the sliding door 106 can be connected by other mechanical structures, such as a spring-ball structure, so that the position of the adjusting plate 314 can be triggered by the position change of the sliding door 106.

Fig. 10-1 to 10-3 are schematic diagrams illustrating an air volume control state of the fume hood according to an embodiment of the present invention. As shown in the figure, C is the distance between the free end of the adjusting plate 314 and the lower bottom plate of the air supplement channel 301; d is the distance between the lower end of the sliding door 106 and the air supply opening 302. The 3 operating states used by the fume hood are generally:

1. the sliding door 106 is in a closed state, an experiment non-operation state or an experiment without supervision. At this time, the movable door 106 moves to cause the opening degree of the opening 101 of the cabinet 100 to be 0% -4%, and the free end of the adjusting plate 314 is set to be in contact with the bottom plate of the air supply channel 301, namely, the outer air supply opening 311, Q is closed_{Supplement device}＝Q_{Supplement the interior}；

2. The opening degree of the sliding door 106 is 5% -60%, and experimenters need to carry out experiment operation in the cabinet. At this time, the free end of the adjusting plate 314 is set to be spaced from the bottom plate of the wind supply channel 301 by 40% of the height of the wind supply channel 301, and in this state, Q is set to be equal to_{Supplement the external}＝40％×Q_{Supplement device}，Q_{Supplement the interior}＝60％×Q_{Supplement device}；

3. When the sliding door 106 is in the fully open state, which is a state that an experimenter usually performs experimental operation at the height, the free end of the adjusting plate 314 is set to be 70% of the height of the air supply channel 301 away from the bottom plate of the air supply channel 301, and in the state, Q is set_{Supplement the external}＝70％×Q_{Supplement device}，Q_{Supplement the interior}＝30％×Q_{Supplement device}。

Fig. 10-1 to 10-3 can be used to illustrate a control method of a fume hood according to an embodiment of the present invention. The fume chamber that this embodiment provided can further guarantee safety through accurate automatic control, prevents that harmful gas from spilling over in the cabinet.

In this embodiment, the fume hood further comprises:

a position sensor for detecting a position of the sliding door 106; and

a control unit electrically connected to the position sensor,

the guide plate 310 further includes an adjusting plate 314, and the adjusting plate 314 is hinged to the guide plate 310. In the operation of this embodiment, the control unit controls the adjusting plate 314 to rotate a certain angle according to the detection information of the position sensor, so as to adjust the air distribution of the inner and outer air supply ports separated by the guiding plate 310.

As shown in fig. 10-2 to 10-3, C is the distance between the free end of the adjusting plate 314 and the bottom plate of the wind supplementing channel 301; d is the distance between the lower end of the sliding door 106 and the air supply opening 302.

The control method of the embodiment is respectively controlled according to the following working states, and the 3 working states used by the fume hood are generally as follows:

2. The opening degree of the sliding door 106 is 5% -60%, and experimenters need to carry out experiment operation in the cabinet. At this time, the distance between the free end of the adjusting plate 314 and the bottom plate of the air supply channel 301 is set to be 40% of the height of the air supply channel 301, and Q is set to be Q_{Supplement the external}＝40％×Q_{Supplement device}，Q_{Supplement the interior}＝60％×Q_{Supplement device}；

3. When the sliding door 106 is in a fully open state, the experimenter usually performs experimental operation at the height, the free end of the adjusting plate 314 is set to be 70% of the height of the air supplementing channel 301 at the distance from the bottom plate of the air supplementing channel 301, and Q is set to be_{Supplement the external}＝70％×Q_{Supplement device}，Q_{Supplement the interior}＝30％×Q_{Supplement device}。

In this embodiment, when the fume hood exhausts air, the following effects can be achieved by controlling the rotation angle of the adjusting plate 314 according to the sensing of the control unit to the position of the sliding door 106: 40% -69% of the air supplement amount is provided by the air supplement opening 302, 31% -50% of the air supplement amount is provided by the cabinet door opening 101, and the rest air supplement amount is provided by the top passage 105.

The beneficial effects of the embodiments provided by the present invention are illustrated below based on experimental data. The requirement of the fume hood leakage not exceeding AM0.05PPM (5e-08PPM) is based on the ANSI/ASHRAE110-2016 standard. Wherein, ANSI is American national standards institute, make the standard; ASHRAE is the american society of heating and ventilation engineers, and sets up inspection specifications based on standards.

The CFD fluid sub-plate physical model and boundary conditions show that the SF6 tracer gas generator jet flow rate is 4L/min, which is placed according to ANSI/ASHRAE 110-:

the experimental parameter is set to Q_{Supplement device}＝480CMH，Q_{Row board}＝1200CMH，Q_{Supplement device}＝Q_{Row board}× 40%, the leakage rate is-5.4396 e-011 PPM;

the experimental parameter is set to Q_{Supplement device}＝540CMH，Q_{Row board}＝1200CMH，Q_{Supplement device}＝Q_{Row board}× 45%, the leakage rate is 8.8284e-011 PPM;

the experimental parameter is set to Q_{Supplement device}＝720CMH，Q_{Row board}＝1200CMH，Q_{Supplement device}＝Q_{Row board}× 60%, the leakage rate is-1.7025 e-010 PPM;

the experimental parameter is set to Q_{Supplement device}＝828CMH，Q_{Row board}＝1200CMH，Q_{Supplement device}＝Q_{Row board}× 69% of the total leakage is 1.4958e-009PPM；

The experimental parameter is set to Q_{Supplement device}＝840CMH，Q_{Row board}＝1200CMH，Q_{Supplement device}＝Q_{Row board}× 70%, the leakage rate is 4.0223e-008 PPM.

Therefore, when the air supply amount of the ventilation cabinet provided by the embodiment of the invention is 40% -69% of the air exhaust amount, the leakage amount is far lower than the standard requirement of 5e-08PPM, and the safety requirement is completely met. However, once Q is satisfied_{Supplement device}＝Q_{Row board}× 70%, the leakage rate begins to approach the standard value, indicating a safety hazard.

FIGS. 11-1 and 11-2 show a fume hood Q according to an embodiment of the present invention_{Supplement device}＝40％×Q_{Row board}A perspective view and a side view of the leakage rate detection graph; FIGS. 11-3 and 11-4 show a fumehood Q according to an embodiment of the present invention_{Supplement device}＝40％×Q_{Row board}A time airflow velocity flow chart and an airflow velocity section chart.

Fig. 12-1 and 12-2 show a fume hood Q according to an embodiment of the present invention_{Supplement device}＝45％×Q_{Row board}A perspective view and a side view of the leakage rate detection graph; fig. 12-3 and 12-4 show a fume hood Q according to an embodiment of the present invention_{Supplement device}＝45％×Q_{Row board}A time airflow velocity flow chart and an airflow velocity section chart.

FIGS. 13-1 and 13-2 show a fumehood Q according to an embodiment of the present invention_{Supplement device}＝60％×Q_{Row board}A perspective view and a side view of the leakage rate detection graph; FIGS. 13-3 and 13-4 show a fumehood Q according to an embodiment of the present invention_{Supplement device}＝60％×Q_{Row board}A time airflow velocity flow chart and an airflow velocity section chart.

FIGS. 14-1 and 14-2 show a fume hood Q according to an embodiment of the present invention_{Supplement device}＝69％×Q_{Row board}A perspective view and a side view of the leakage rate detection graph; FIGS. 14-3 and 14-4 show a fume hood Q according to an embodiment of the present invention_{Supplement device}＝69％×Q_{Row board}A time airflow velocity flow chart and an airflow velocity section chart.

From above Q_{Supplement device}＝(40％～69％)×Q_{Row board}The perspective view and the side view of each leak rate detection chart show the range of the volumetric component of the tracer gas concentration at 0.01 PPM. Required in ANSI/ASHRAE110-2016 StandardThe leakage rate of the tracer gas is not more than 0.05PPM, and the position of a boundary surface when the concentration of the tracer gas (SF6 sulfur hexafluoride) is 0.01PPM is shown in the figure, so that the tracer gas is exhausted without diffusing to two sides, the boundary of the tracer gas does not overflow in a working cavity of the exhaust hood all the time, the ventilation hood has strong flow stopping capacity, no leakage exists at two sides, and the safety performance of 'no leakage' is realized.

From above Q_{Supplement device}＝(40％～69％)×Q_{Row board}As shown in a flow chart of the speed of each air flow, the internal air flow is organized into a laminar state, and the overflow of internal pollutants is well prevented. The air supply of the air supply opening 302 is mainly discharged from the lower part 402 of the guide plate, and the passive air supply quantity Q outside the cabinet at the opening_{Door with a door panel}Mainly discharged from the upper part 403 of the guide plate, and the passive air supply quantity Q of the top passage 105_{Side wall}The air is mainly discharged from the gap of the inclined part 404 of the guide plate 400, and completely meets the requirement of safety design. In this case, the amount of air discharged from the gap between the inclined portion 404 of the baffle 400 and the upper portion 403 of the baffle is 10%, the amount of air discharged from the upper portion 403 of the baffle is 30%, and the amount of air discharged from the lower portion 402 of the baffle is 30% to 60%.

It is worth noting that it is essential for the hood that not only is there no spillage at the door opening, but that in an optimal condition there is no turbulence or any reverse movement of the air moving within the hood.

From above Q_{Supplement device}＝(40％～69％)×Q_{Row board}As shown by the sectional view of each air flow speed, the outlet jet of the air supply opening 302 is a fan-shaped laminar structure without any turbulent flow or reverse air flow. The importance here is that if any one of the air supply opening, the air supply quantity, the arrangement of the internal space of the cabinet body and the design of the guide plate is insufficient, the arrow in the figure can be vertically directed up and down or directed in the opposite direction. Except for the air close to the exhaust opening 201 or between the baffle 400 and the rear wall of the cabinet 100, if the arrow in the cabinet 100 is vertically directed up and down or the arrow is directed in the reverse direction, the fluid structure in the cabinet 100 is disordered, and the vortex, the reverse flow and the overflow risk are generated during the operation, so that the basic safety performance requirement of the ventilation cabinet is damaged.

FIG. 15-1 and FIG. 15-2 are views of the present inventionEmbodiment provides a fume hood Q_{Supplement device}＝70％×Q_{Row board}A perspective view and a side view of the leakage rate detection graph; FIGS. 15-3 and 15-4 show a fumehood Q according to an embodiment of the present invention_{Supplement device}＝70％×Q_{Row board}A time airflow velocity flow chart and an airflow velocity section chart.

As can be seen in fig. 15-2, tracer gas (indicated by the black portion within the cabinet) has escaped from the opening 101 out of the cabinet 100, indicating that the fume hood safety performance requirements cannot be met when the fume hood is set to 70% × Q rows Q plus.

As can be seen from fig. 15-1, the boundary surface of the trace gas at a concentration of 0.01PPM extends to the vicinity of the left and right sides within the fume hood. At this time, the flow rate of the passive make-up air flow entering the cabinet 100 through the opening 101 is low, and the trace gas is difficult to be pushed to the air outlet 201 by the make-up air flow because the left and right sides in the cabinet are far away from the air outlet 201, so that the pollutants are in risk of overflowing out of the opening 101.

Although the air supply opening 302 is divided into the outer air supply opening 311 and the inner air supply opening 312 by the guide plate 310 in the embodiments of the present invention, it can be understood by those skilled in the art that the air supply opening 302 can be divided into a plurality of outer air supply openings 311 and a plurality of inner air supply openings 312 by a plurality of guide plates 310, and therefore, the number of the guide plates 310 and the number of the inner air supply openings 312 and the outer air supply openings 311 are not limited in the present invention.

The fume hood provided by the embodiments of the invention breaks through the recognition in the original industry that harmful gas in the fume hood can be prevented from overflowing only by completely supplementing air or isolating the inner cavity of the fume hood from the external environment. For example, there are indications in the research and application of air curtain type exhaust hood (Ministry of university of south China, 3.2002, 16, 1 st period: 44-49) that the compensation air provided by the air supplement type exhaust hood 1 is easy to interfere with the surface air speed and destroy the sealing effect of the exhaust hood, and obviously, the authors think that the air supplement type exhaust hood has the problem of gas overflow in the exhaust hood due to the 'easy damage of the sealing effect of the exhaust hood'.

The fume hood provided by the embodiments of the invention is not confined on the original knowledge of the fume hood, and creatively guides the external environment air supplement of the fume hood, so that the external air flow which is originally considered to be interference closed is changed into 'beneficial' air flow which is used as passive air supplement air flow and works together with active air supplement air flow and is mutually matched.

According to the fume hood provided by the embodiment of the invention, the potential safety hazard that all exhaust air flow exhausted outside the fume hood is supplemented by active supplement air flow of an air supplement system or passive supplement air flow outside the fume hood is eliminated, and the unidirectional air flow always facing to the exhaust port in the fume hood is formed at the opening 101 of the fume hood by arranging the air supplement port 302 below the opening 101 of the hood body 100 and controlling the mutual proportion of the exhaust air quantity, the active supplement air flow quantity and the passive supplement air flow quantity, so that the safety of a user can be ensured, and the harmful gas in the hood is effectively prevented from overflowing. In addition, compared with the prior art that the air supply quantity of the three air supply ports needs to be accurately controlled when the three air supply ports are arranged, or the risk that the effect and the safety are lost is reduced once the balance is lost, the structure is simpler compared with a plurality of air supply ports due to the fact that only one air supply port is arranged, the production cost is lower, and the safety factor is increased.

Claims

1. The utility model provides a fume chamber, includes that the front side is opened there is the open-ended cabinet body, its characterized in that still includes:

the air outlet is communicated with the cabinet body and arranged at the top of the cabinet body close to the rear side;

a guide plate standing in the cabinet body and close to the rear side, wherein the guide plate comprises a base plate and an inclined part, gaps are reserved between the lower end of the base plate and the bottom of the cabinet body and between the lower end of the inclined part and the base plate,

the air supply port is positioned below the opening, a guide plate is arranged in the air supply port, and the guide plate divides the air supply port into an outer air supply port pointing upwards and an inner air supply port pointing into the cabinet body; the guide plate is also provided with an adjusting plate, the adjusting plate is hinged with the guide plate, and the air quantity distribution of the outer side air supply port and the inner side air supply port can be adjusted by adjusting the rotating angle of the adjusting plate relative to the guide plate;

the inclined portion is arranged such that a front end thereof covers the air discharge opening when viewed from below.

2. A ventilation cabinet as claimed in claim 1, wherein said air exit is centrally located in said cabinet body intermediate the left and right sides thereof when viewed from the front; the center of the air outlet is positioned at the rear side in the cabinet body when viewed from the left side or the right side.

3. A fumehood according to claim 1 wherein said air exit is centrally located in said cabinet body between and one quarter of the way to the rear of the front and rear sides, as viewed from the left or right side.

4. A fumehood according to claim 1 wherein said air supply opening has a width, as viewed from the front, greater than or equal to the width of said cabinet body such that said air supply opening extends to and covers both the left and right ends of the opening.

5. A fumehood according to claim 1 wherein said air supply opening is curved or chamfered between a top side and a rear side of said air supply opening when viewed from the left or right side, such that said air supply opening supplies air upwardly and rearwardly.

6. A fumehood according to claim 5 wherein said arc is a quarter arc.

7. A fumehood according to claim 1 wherein the outside of said air supply opening is in the same vertical plane as the inside of the front portion of said cabinet such that upward air supply flow delivered through said air supply opening covers said opening in said cabinet.

8. A fumehood according to claim 1 wherein said guide plate is arcuate in cross-section for directing the flow of make-up air delivered through said inboard air supply opening.

9. A fumehood according to claim 1 wherein a lower end portion of said guide plate is located within said air supply duct, said lower end portion being adapted to distribute the air supply from said outboard air supply opening to said inboard air supply opening.

10. A ventilation hood according to claim 1 wherein the base plate of the baffle plate is provided with through holes which are uniformly distributed in the horizontal width direction and whose hole area ratio to unit area decreases from bottom to top.

11. A fumehood according to claim 10 wherein said perforations are progressively spaced from bottom to top.

12. A fumehood according to claim 10 wherein said through holes provided in said base plate of said baffle plate are narrow at the top and wide at the bottom, as viewed from the front, and are arranged radially.

13. A fumehood according to claim 10 wherein said baffle base plate further comprises an upper baffle portion and a lower baffle portion, said lower baffle portion being spaced from said upper baffle portion.

14. A fumehood according to claim 1 wherein an inclined plate is provided in the cabinet body above the front side; the upward extending direction of the inclined plate and the upward extending direction of the inclined part form an included angle.

15. A fumehood according to claim 1 further comprising an air supply fan in communication with said air supply passage, said air supply fan being a variable power fan.

16. A fumehood according to claim 15 wherein said air supply fan is disposed within said air supply passage.

17. A fumehood according to claim 1 further comprising a supplementary air valve in communication with the supplementary air passage, said supplementary air valve being a variable opening valve.

18. A ventilation cabinet as claimed in claim 1, wherein the side walls and/or lower wall of the cabinet are hollow, and the air supply duct is provided in the side walls and/or lower wall of the cabinet.

19. A fumehood according to claim 1 further comprising:

the sliding door is arranged at the opening and can slide along the opening to adjust the opening area of the opening; and a top passage communicating the inside of the cabinet body with the outside of the cabinet body, the top passage outlet being located inside the cabinet body,

and the fume hood is set to make up 40-69% of the air exhaust amount by the air flow sent out by the air supply port when the air exhaust port exhausts air.

20. A fumehood according to claim 19 wherein the exterior side wall of said air supply opening is in the same vertical plane as the exterior side wall of said sliding door such that upward air supply flow delivered through said air supply opening covers said opening in said cabinet body.

21. A method of controlling a fumehood according to claim 19, said fumehood comprising:

a control unit connected to the position sensor,

the control unit controls the adjusting plate to rotate by an angle according to the detection information of the position sensor, and is used for adjusting the air volume distribution of the inner air supply opening and the outer air supply opening which are separated by the guide plate;

the control method comprises the following steps:

when the opening of the opening is 0% -4% due to the movement of the sliding door, the free end of the adjusting plate is set to be in contact with the bottom plate of the air supplementing channel, namely the outer air supplementing opening is closed;

when the opening degree of the opening is 61-100% due to the movement of the sliding door, the distance between the free end of the adjusting plate and the bottom plate of the air supplementing channel is set to be less than or equal to 70% of the height of the air supplementing channel.

22. A control method of a fume hood according to claim 1, characterized in that when the fume hood exhausts air, 40% -69% of the exhausted air volume is supplemented by the air flow sent from the air supply port.