The induction fan with a new ventilation concept adopts the concept of jet induced ventilation system, consisting of a supply fan, multiple induction fans (or ducted induction fans), and an exhaust fan. The main application of theory comes from aerodynamics, and with the disturbance characteristics of a small amount of high-speed jet gas, the disturbance jet can effectively induce the surrounding stationary air and drive air circulation. Under the condition of no air duct, according to the law of conservation of momentum, the central velocity of the jet gradually decreases from the outlet point, but the jet width gradually increases, and the induced amount of surrounding air also gradually increases. According to this principle, fresh air is induced and sent to the second fan (nozzle) installed within the first effective range. It then goes down in sequence and is sent to the necessary area before being discharged outdoors through the exhaust fan. And with appropriate system design and layout, achieve optimal indoor airflow organization, and achieve efficient and economical ventilation and air exchange effects.
Traditional underground garage ventilation systems use low-speed air duct supply and exhaust systems arranged inside the garage, but their biggest drawback is that the cross-sectional size of the air ducts is relatively large. Gases often gather in blind spots far away from the airflow; The net height of the garage is generally low, and the use of low-speed air ducts creates a sense of pressure; Large installation workload, high investment: high operating costs. At the same time, some buildings cannot install air ducts due to their inherent characteristics.
Induced draft fans have become a widely used ventilation equipment in large spaces such as parking lots, various warehouses, sports stadiums, and workshops in industrialized countries such as Europe, America, and Japan. This ventilation device has been adopted as a conventional ventilation method for underground parking lots and included in the building equipment design specifications, and is gradually being promoted and popularized.

Design of induced draft fan airflow

1. YDF series ducted induction fan airflow design:
1) First, calculate the floor area and ventilation rate of the building: according to Article 139 of Chapter 5 of the Building Design and Construction Regulations, the standard ventilation rate is 35m/h. m '.
2) Install an appropriate number of exhaust fans at the air supply and exhaust ports (with a total air volume of Q for each fan), where the supply fan is used to supply fresh air and the exhaust fan is used to remove exhaust gas.
3) Proper installation of high-pressure fans and nozzles: For every 1000 square meters of area, arrange one ducted fan, and for every 30 square meters of area, install one nozzle. Each high-pressure fan can supply about 30 nozzles. Install the high-pressure fan at a certain location and roughly distribute the nozzles evenly, but pay attention to arranging them towards the outlet.
4) The high-pressure fan is connected to the nozzle through a high-speed spiral air duct, with the main pipe measuring 35cm and the branch pipes gradually decreasing to the appropriate aperture and passing through the beam.
2. Wind volume design of YDF series multi fan induced draft fan
1) According to the regulations, the air volume of the underground garage shall be determined based on a ventilation rate of no less than 6 times per hour: Q>6. V m/h
2) Select appropriate air supply and exhaust fans at the air supply and exhaust outlets;
3) The number of units is determined based on the principle that one jet machine can cover 100-250 square meters. When the garage area is small and there are few obstacles such as walls, the upper limit is taken. Conversely, when the garage area is large and there are many obstacles such as walls, the lower limit is taken;
4) Arrange the units based on the determined number of units and building form, with the principle of smooth airflow from the inlet to the outlet.
3. The downward angle of the nozzle (H is the height from the nozzle to the ground)
H<2.5m
A=0°
H=2.5m~3.0m A=15°
H=3.0m~4.0m A=20°
H=4.0m~4.5m A=30°
4. Design Description
1) The jet guidance system consists of three parts: a supply fan, an induction fan unit, and an exhaust fan. The supply fan is used to supply fresh air, while the induction fan unit mixes the air in the garage evenly and guides the fresh air along the designed path from the supply outlet to the exhaust outlet, while driving the exhaust gas to the exhaust fan; Then the exhaust fan discharges the exhaust gas outdoors.
2) The position of the supply and exhaust fans should be located at both ends of the fire compartment.
3) There are car entrances and exits in the garage that directly lead to the outside, which are fire compartments and do not require air supply fans.
4) Underground garages with an area not exceeding 2000m may not be equipped with mechanical smoke exhaust systems. A non duplex garage equipped with an automatic fire extinguishing system has a fire compartment with a building area of up to 4000 square meters
5) Regarding the smoke exhaust duct, as it is no longer used for exhaust purposes, the wind speed inside the duct can be increased to 20m/s, and the coverage distance of each smoke exhaust outlet can reach 30m. This ultimately leads to a significant reduction in the size and density of the smoke exhaust duct compared to conventional methods (usually by 50%). Moreover, due to the elongated spacing between ducts, the smoke exhaust duct can often be arranged around the garage walls or other locations that do not occupy the garage floor height.

air exchange efficiency

Life experience tells us that if the air in a fixed space is polluted, the best way to ventilate is to form air convection, commonly known as "cross ventilation". 'Cross ventilation' can completely replace gas in a fixed space in the shortest possible time, with the highest efficiency.
Similarly, in underground garages or larger spaces, rapid ventilation and air exchange should be achieved, preferably with "cross ventilation". However, due to the particularity of this situation, it is impossible to use natural "ventilation" for ventilation, and induced ventilation equipment is the device that realizes artificial "ventilation".
The core principle is to use the law of conservation of momentum to rapidly spray wind speed with a certain amount of energy, gradually spreading it into a "wind surface". The various "wind surfaces" are artificially arranged into a wall, moving along a set path and carrying polluted air along the way to a designated location. Because wind has shape uncertainty, it can change with various cross-sectional changes during the process, like a piston filling the entire space and moving forward, with a theoretical ventilation efficiency of 100%. This ventilation method is called "displacement type" or "cross flow type" ventilation.
Induced ventilation equipment is a key device for achieving artificial "cross ventilation". Due to its high ventilation efficiency, this technology originated in Europe and America and has been in use for nearly 20 years. In recent years, it has gradually been accepted and applied by numerous domestic users and professional technicians. Beijing Institute of Architectural Design and Research included this system and equipment in Chapter 3, Chapter 6, Section 4 of the "Technical Code for Professional Design of Building Equipment" in 1999. The measures clearly require that the mechanical ventilation of the parking garage should adopt the jet guided ventilation method to ensure good ventilation inside the garage and reduce the cost of air ducts and the height of equipment occupied in the garage.

Induction fan workflow and application

The purpose of intelligent control of induced draft fans is to effectively save energy and prevent misoperation. It is to induce the ventilation system to operate more safely, reliably, and economically. At the same time, it is also to improve the intelligence level of the entire building.

1. Due to the unique environment of the underground garage (insufficient oxygen supply). In the early stages of a fire, a large amount of smoke and carbon monoxide C0 will be generated. If the induced draft fan starts working at this time, the consequences can be imagined. So, simply detecting C0 concentration as a startup indicator is inaccurate. Because C0 produces more than just the only vehicle exhaust. Smoke indicators must be increased.
2. It is obviously uneconomical to turn on the entire system when C0 exceeds the standard for the first time. So, the program setting: the first detection of C0 exceeding the standard only requires opening one nearby device for dilution. The entire garage space also has enough space to accommodate one Point pollution.
3. When the same machine still exceeds the C0 standard after the set dilution time, the program has reason to believe that the entire garage is saturated and the entire system must be turned on for ventilation.
4. After the entire induction system is activated, only a flow field is formed inside the garage, and air is transported to the exhaust outlet according to the designed route. The exhaust fan in the exhaust shaft must be turned on in order to discharge outwards. So it is necessary to link the exhaust fan. Similarly, if it is within a safe zone, the air supply fan should be linked to supplement fresh air.

Comparison between YDF series shower induction fan and traditional fan

YDF induced draft fan performance parameter table

YDF induced draft fan external dimensions