Reed-type valves

Figure 14.3 Mechanical valves (a) flapper type and (b) reed type.

Fig. 2.6 Mechanical valves, (a) Flapper-type (b) Reed-type with petal-shaped lamella (c) Reed-type with rectangular lamella.

The reed valves normally used in heavy-duty pulse combustors are made from thin-sheet spring-sted (Fig. 2.6b and c), and the spring action of reed valves is such that, when normally shut, the valves are sprung lightly. In order to ensure a vigorous mixing of the fuel and air, the fully open flow area of the inlet reed valves must be considerably smaller than the cross-sectional area of the combustion zone. The major problem often encountered with reed-type mechanical valves is fatigue-based failure. 

As described above, position detection devices provide a method to determine the position of a valve or control rod. The four types of position indicators discussed were limit switches, reed switches, potentiometer valve position indicators, and LVDTs (Figure 7). Reed and limit switches act as ON/OFF indicators to provide open and closed indications and control functions. Reed switches can also be used to provide coarse, incremental position indication. 

Based on the manner in which fuel and air charge the combustion chamber, pulse combustors are divided into two general categories those with mechanical valves and those with aerodynamic valves (also called valveless combustors). Mechanical valves can be further divided into three types flapper valves, reed valves, and rotary valves. 

Flap valve position is detected by means of duplicated detectors. Detectors used are of the reed-switch type. Closed valve position is detected by two detectors. 

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