Before the combustion machine ignition, there must be a period of pre-blowing, the furnace and flue in the residual air blown away or diluted. Because the combustion chamber is inevitably left over gas, if not pre-blowing and ignition, there is a risk of explosion. The residual gas must be blown clean or diluted to ensure that the gas concentration is not within the explosion limit. The preblowing time is generally set to 15-60 seconds depending on the structure of the furnace and the blowing volume.
Electric spark ignition is suitable for gas burning machine, which is easy to realize automatic control. High voltage ignition transformer can be used to generate arc ignition, and its output energy is required to be: voltage ≥ 3.5K V, current ≥15mA, ignition time is generally: 2 ~ 5 seconds.
The combustion state must be dynamically monitored. Once the flame detector detects the flameout signal, it must be fed back to the burner within a very short time. The burner will then enter the protection state and cut off the gas supply.The flame detector should be able to sense the flame signal normally, neither sensitive nor dull. Because of sensitivity, if the combustion state fluctuates, it is easy to produce false action and slow, and the feedback flame signal lags behind, which is not conducive to safe operation.It is generally required that the response time from flameout to flame-detector flameout signal should not exceed 0.2 seconds.
When the burner ignites, the gas is fed into the burner and ignited. The ignition action should take place before the gas inlet, and the ignition temperature field should be formed first to facilitate the ignition and combustion. If the fire is not lit, the flame detector cannot detect the flame signal, and the burner enters the protective state.The time from ignition to protection should be appropriate, neither too short nor too long. Too short, too late to form a stable flame; Too long, when the ignition does not cause a large amount of gas into the furnace. Generally, it is required that the burner judge the flame signal detected by the flame detector in 2-3 seconds after the gas is injected. If there is no fire, the burner will enter the protective state, and if there is fire, the combustion will be maintained.
In the combustion process, if the combustion machine accidentally shut off, the combustion machine into the protection state. Because the furnace is hot. Gas entry is prone to deflagration, so it is necessary to enter the protection state in a very short time and cut off the gas supply.The response time is required to be no more than 1 second from the occurrence of flameout to the state of combustion entry protection.
The steady combustion of the gas burner has a certain range, and only the gas pressure is allowed to fluctuate within a certain range. The purpose of limiting the gas high and low pressure is to ensure the flame stability: it does not take off, does not flameout and does not temper, and at the same time, it limits the heat output power of the burner to ensure the safe and economic operation of the equipment. When the gas pressure exceeds this range, the burner should be locked in operation.Generally, gas pressure switch is used in the design of combustion machine to sense pressure signal and output switching signal, so as to control the corresponding work of combustion machine.
Gas-fired combustion engine is designed with high thermal intensity, and its combustion mode adopts blast forced mode. If the failure of the fan causes air interruption or air shortage, cut off the gas immediately, otherwise the furnace deflagration or tempering to the fan will occur. Therefore, while improving the quality of the fan, the gas control must be interlinked with the air pressure. When the air pressure is insufficient, the gas supply should be cut off immediately.Generally, the gas pressure switch is used to sense the air pressure signal and output the switching signal to control the corresponding work of the gas solenoid valve.
If the power is suddenly cut off in the working process of the burner, the gas supply must be cut off immediately to protect the safety of the equipment. Gas control solenoid valve must be normally closed, once power off, automatically shut off the gas supply. Solenoid valve closing response time ≤5s.
Gas leakage may cause boiler explosion. There are several ways to solve the problem of gas leakage in the gas furnace: first, strengthen the pre-blowing time and blowing volume, blow off or dilute the gas in the furnace; Second, the gas pipeline adopts two solenoid valves in series to improve the system safety; Third, the pipeline leakage detection device is used to detect the gas pipeline before ignition. If the gas leakage reaches a certain amount, the combustion machine will be locked.
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