JPH0229507A - Premix type multihole burner - Google Patents

Abstract

PURPOSE: To protect the surface around a port against damage due to heating and to protect a burner against damage due to backfire by making one or more specified port at a multiport burner smaller in area than the remaining ports and providing means for detecting the presence of a flame within a specified port. CONSTITUTION: Outlet wall 1 of a burner is made of a slotted plate of ceramic, or the like wherein each slot 2 forms outlet of fuel and air having identical bore area. An aperture restrictor 4 is set in a recess adjacent to the upstream end 3 of a port 2' and the bore area is smaller than that of the remaining ports 2'. A thermocouple probe 5 extends into the port 2' through the restrictor 4 and the forward end 6 of the probe 5 terminates at a distance about 6 times as long as the bore diameter of the restrictor from the upstream end 3. At the time of normal combustion, no signal is delivered from the probe 5 and a valve 8 is opened by a control box 7. When the ratio of air in a fuel/air mixture decreases and the combustion face begins to be heated, retraction of flame (light back) takes place in the port 2' and the probe 5 is heated by the flame in the port 2' to provide the control box 7 with a signal for closing the fuel valve 8 thus protecting the burner.

Description

[Detailed description of the invention] The present invention relates to a premix type multi-burner.

Such burners include a plenum chamber for internally mixing fuel and air before reaching the burner outlet. The outlet is formed by one of the chamber walls, which has a number of ports through which the fuel/air mixture can pass and be combusted.

The problem with this type of burner is that the surfaces surrounding the spout can heat up and become damaged, and the combustion flame can back up through the spout, damaging the burner.

An object of the present invention is to provide a premix type multi-burner that can alleviate such problems.

According to the invention, one or more predetermined ports have an aperture, at least a part of which has an area smaller than the area of the remaining ports, and means for detecting a flame inside the predetermined port. A premix type multi-burner is provided.

In this configuration, once the surface begins to heat up, a safe constant propagation of the flame (writeback) is induced at a given port before the surfaces surrounding the remaining ports are heated. A write-back flame is detected and a signal is sent to the control box to close the fuel valve, thus preventing the combustion surface from heating too much.
Therefore, the burner is protected from writeback in the remaining mouth.

The means for detecting the flame at a given port is an elongated thermocouple probe.

A given port is constructed such that, following a constant write-back, the flame is drawn back into the interior of the port and travels upstream until the remaining port becomes a space that receives a supply of air/gas mixture.

A given port has a small area aperture formed by a perforated restrictor placed adjacent the upstream end of the port, and a probe is positioned between the restrictor and the downstream end of the port. It passes through the flow restrictor with its tip placed at the point.

Suitably, the thermocouple is placed downstream of the predetermined port at a hole diameter of 8 times or less.

A flow restrictor is a flow restrictor in which a given port receives the mixture at a significantly lower flow rate than the normal ports, so that the given port experiences a higher operating temperature and, therefore, faster writeback than the remaining ports. The size is such that it can be inserted.

Next, embodiments of the present invention will be described below with reference to the accompanying drawings.

Referring to Figures 1 to 3, only the outlet wall 1 of the burner is shown, which includes a plenum chamber (not shown) for receiving and internally mixing fuel and air. form part.

The outlet wall 1 consists of a slotted plate, for example made of ceramic, each slot 2 forming an outlet for fuel and air and having the same pore area.

A flow restrictor 4 with a hole is placed in a recess adjacent to the upstream end 3 of a given port 2', and the hole area is equal to the hole area of the remaining port 2' (and the hole area of the remaining port 2). pore area).

A thermocouple probe 5 extends through the restrictor 4 and into the port 2', with a tip 6 of the thermocouple probe 5 terminating approximately six times the restrictor bore diameter from the upstream end 3 of the port 2'. ing. The probe 5 is of such a diameter that there is an annular gap between the circumference of the probe 5 and the bore wall of the flow restrictor for admitting the fuel/air mixture into the mouth.

The probe 5 is connected to a control box 7 which, when receiving or receiving a signal from the probe, operates to close a valve 8 which controls the supply of fuel to the plenum chamber of the burner.

During normal combustion as shown in FIG. 2, there is no signal from the probe 5 and the valve 8 is opened by the control box 7.

However, when the proportion of air in the fuel/air mixture decreases and the combustion surface begins to heat up, flame recession (hereinafter referred to as ``lightback'') occurs at the mouth 2', as shown in Figure 3. 2′ heats the probe 5 and controls the control box 7.
A signal is sent to close the fuel valve 8.

Referring to FIGS. 4 and 5 (components that are the same as those shown in FIGS. 1 to 3 are designated by the same reference numerals):
The outlet wall 10 of the burner is formed as a whole by a number of corrugated metal pieces 11, each metal piece 11 being held between a pair of metal spacing means 120, with the metal piece 11 and the spacing means 12 being held together. The mouth 13 can be held at a distance between.

However, in this case, one metal piece 12 consists of two separate parts 14 , 15 spaced apart from each other to form a predetermined opening 16 .

A perforated restrictor 17 is fixed to the portion 14 at the upstream end of the port 16, the aperture area of which is smaller than the aperture area of the given port 16 and the remaining ports 13.

Thermocouple probe 5 extends through restrictor 17 and into port 16 . For the above embodiment, the thermocouple tip 6
terminates approximately six times the restrictor hole diameter from the upstream end of the port 16 and includes an annular gap between the circumference of the probe 5 and the restrictor hole wall to direct the fuel/air mixture to the port 16. Put it in.

[Brief explanation of the drawing]

Figure 1 is a plan view of the combustion surface of a typical multi-mouth burner whose openings are in the form of slots provided on the outer wall of the burner;
The figure is a cross-sectional view of the outer wall of Figure 1 showing a normal combustion state, Figure 3 is a diagram similar to that shown in Figure 2 showing the write-back phenomenon that occurs at a predetermined opening, and Figure 4 is a diagram of the present invention. FIG. 5 is a plan view of the combustion surface of the outer wall of a typical ribbon-type multi-burner modified by the above method, and FIG. 5 is a cross-sectional view of the outer wall shown in FIG. 1...Exit wall, 2...Slot, 5...Thermocouple probe, 7...
Control box, 8...Fuel valve.

Claims (3)

[Claims] (1) A premix type multi-hole burner, in which one or more predetermined ports detect a hole in which at least a portion of the hole has an area smaller than the area of the remaining ports, and a flame inside the predetermined port. A burner characterized in that it has means for. 2. The burner of claim 1, wherein the means for detecting the flame comprises an elongated thermocouple probe. (3) The smaller area hole section was formed by a perforated flow restrictor placed adjacent to the upstream end of the mouth, and the probe placed its tip between the flow restrictor and the downstream end of the mouth. 3. The burner according to claim 2, wherein the burner passes through the flow restrictor.