Key points for matching burners and boilers

Whether a fully active oil (gas) burner with superior performance still has the same superior combustion performance when installed on a boiler depends largely on whether the gas dynamic characteristics of the two match. Only good matching can give full play to the performance of the burner, achieve stable combustion in the furnace, achieve the expected heat energy output, and obtain excellent thermal efficiency of the boiler.

1. Matching of gas dynamic characteristics

A single fully active burner is like a flamethrower, which sprays the fire grid into the furnace (combustion chamber), achieves effective combustion in the furnace and outputs heat. The combustion effectiveness of the product is measured by the burner manufacturer. carried out in a specific standard combustion chamber. Therefore, the conditions of standard experiments are generally used as the selection conditions for burners and boilers. These conditions can be summarized as follows:
(1) Power;
(2) Air flow pressure in the furnace;
(3) The space size and geometric shape (diameter and length) of the furnace.
The so-called matching of gas dynamic characteristics refers to the degree to which these three conditions are met.

2.Power

The power of the burner refers to how much mass (kg) or volume (m3/h, under standard conditions) of fuel it can burn per hour when it is fully burned. It also gives the corresponding thermal energy output (kw/h or kcal/h). ). The boiler is calibrated for steam production and fuel consumption. The two must match when selecting.

3. Gas pressure in the furnace

In an oil (gas) boiler, the hot gas flow starts from the burner, passes through the furnace, heat exchanger, flue gas collector and exhaust pipe and is discharged to the atmosphere, forming a fluid thermal process. The upstream pressure head of the hot air flow generated after combustion flows in the furnace channel, just like water in a river, with the head difference (drop, water head) flowing downward. Because the furnace walls, channels, elbows, baffles, gorges and chimneys all have resistance (called flow resistance) to the flow of gas, which will cause pressure loss. If the pressure head cannot overcome the pressure losses along the way, flow will not be achieved. Therefore, a certain flue gas pressure must be maintained in the furnace, which is called back pressure for the burner. For boilers without draft devices, the furnace pressure must be higher than the atmospheric pressure after considering the pressure head loss along the way.

The size of the back pressure directly affects the output of the burner. The back pressure is related to the size of the furnace, the length and geometry of the flue. Boilers with large flow resistance require high burner pressure. For a specific burner, its pressure head has a large value, corresponding to a large damper and large air flow conditions. When the intake throttle changes, the air volume and pressure also change, and the output of the burner also changes. The pressure head is small when the air volume is small, and the pressure head is high when the air volume is large. For a specific pot, when the incoming air volume is large, the flow resistance increases, which increases the back pressure of the furnace. The increase of the back pressure of the furnace inhibits the air output of the burner. Therefore, you must understand it when choosing a burner. Its power curve is reasonably matched.

4. Influence of the size and geometry of the furnace

For boilers, the size of the furnace space is first determined by the selection of the heat load intensity of the furnace during design, based on which the volume of the furnace can be preliminarily determined.

After the furnace volume is determined, its shape and size should also be determined. The design principle is to make full use of the furnace volume to avoid dead corners as much as possible. It must have a certain depth, a reasonable flow direction, and sufficient reversal time to enable the fuel to burn effectively in the furnace. In other words In other words, let the flames ejected from the burner have sufficient pause time in the furnace, because although the oil particles are very small (<0.1mm), the gas mixture has been ignited and started to burn before it is ejected from the burner, but it is not sufficient. If the furnace is too shallow and the pause time is not enough, ineffective combustion will occur. In the worst case, the exhaust CO level will be low, in the worst case, black smoke will be emitted, and the power will not meet the requirements. Therefore, when determining the depth of the furnace, the length of the flame should be matched as much as possible. For the intermediate backfire type, the diameter of the outlet should be increased and the volume occupied by the return gas should be increased.

The geometry of the furnace significantly affects the flow resistance of the air flow and the uniformity of radiation. A boiler needs to go through repeated debugging before it can have a good match with the burner.