Compared with the traditional fuel vehicle, the noise of hydrogen fuel cell vehicles is much less, but even so, there are still some noise sources on hydrogen fuel cell vehicles, which will affect the comfort of the occupants, especially in the air supply system of the fuel cell system, the noise of the air compressor is larger, generally need to install a muffler in the exhaust road to reduce exhaust noise.

Some time ago, we have introduced the air filter, flowmeter, air compressor, intercooler and electronic throttle in the air path of the fuel cell system. Next, we focus on the muffler.

Toyota Mirai Fuel cell System

As an important device for eliminating air dynamic noise, mufflers have various forms and types. According to different working principles, they can be divided into three types, namely, resistance mufflers, resistance mufflers and impedance compound mufflers.

Resistive silencer

The resistive muffler absorbs energy through the porous sound absorbing material installed in the air flow channel. When the noise passes through the internal pipe of the muffler, the noise will be dissipated into heat energy through the vibration of the air medium in the hole of the porous sound absorbing material through friction and damping, so as to achieve the purpose of noise reduction.

Generally speaking, the resistive muffler is the principle of sound absorption, so that the sound wave is propagated in the sound absorbing medium, by converting the sound energy into other types of energy (generally heat), so as to achieve the effect of noise reduction. Resistive silencer is like a pure resistance circuit in electricity, and the sound absorbing material is similar to a resistance. Therefore, this kind of noise is called a resistive silencer.

Resistive silencer

Generally speaking, the resistive muffler has a good effect on the noise of middle and high frequency band, but poor effect on the noise of low frequency band. According to the construction form and installation position of the airflow channel, the resistance muffler can be divided into straight tube type, plate type, honeycomb type, folding plate type, acoustic flow type, bending tube type and labyrinth type.

Because of the high flow resistance of the resistive silencer, it is not suitable for the fuel cell system.

Resistant silencer

In contrast to resistive silencers, resistant silencers do not require the use of porous sound-absorbing materials. The resistant muffler uses the pipe connected with the interface mutation or the resonant cavity connected by the pipe, and uses the sound wave to reflect and interfere in the mutation section, so as to achieve the purpose of noise reduction. According to different muffler principles, resistant mufflers can be divided into resonance type, expansion type, micro perforated plate, etc.

The resistant muffler has a particularly good noise reduction effect in the range of low and middle frequency. It can adapt to work under high speed, high temperature and pulsating airflow. It is especially suitable for exhaust muffler of engine.

Resistant silencer

Impedance compound muffler

Impedance compound muffler, that is, the combination of resistive muffler and resistant muffler, also combines the advantages of resistive muffler and resistant muffler, and achieves better noise suppression effect under relatively wide frequency.

Muffler for fuel cell vehicles

As mentioned earlier, resistive silencers are not suitable for fuel cell systems due to their high flow resistance. The muffler used in the car needs to work under different loads and different speeds. Therefore, it is required that the muffler can also operate normally under different temperatures and flow rates. At the same time, it needs to have a good noise reduction effect in a wide range and low flow resistance.

Specifically for fuel cell vehicles, the muffler is generally required to have the following characteristics:

1. Good noise reduction effect and noise reduction ability in broadband;

2. Low pressure loss;

3. High temperature resistance, corrosion resistance, air impact resistance

4. Good reliability

5. Low cost

During the development of fuel cell system, pressure loss is an important factor affecting its performance. Large pressure loss means that relatively large power needs to be consumed to overcome large pressure loss, and large power consumption means that the fuel cell system has high parasitic power and low output power, which has a direct impact on the output performance. Therefore, in the design of muffler, pressure loss should be paid special attention to.

Fuel cell system cooling system

At this point, the fuel cell system of the key components of the air road has been introduced one after another, next, will introduce the fuel cell system of the cooling waterway core components, including electronic thermostat, electronic water pump, radiator, electronic fan, deionizer, expansion tank, etc.

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