Aerodynamic valves, pulse combustors

The aerodynamic valves have a specially designed inlet (e.g., a profiled orifice in the inlet pipe, contoured diffuser, or a shrouding duct) in which the fluid flow characteristics act as a physical barrier (fluid diode) to the backflow of combustion products. Such pulse combustors are termed the valveless combustors. Example of valveless pulse combustor is shown in Figure 23.4 (Putnam et al., 1986). 

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. 

Aerodynamic valves employ the fluid mechanical properties of specially designed inlets to act as a physical barrier to the backflow of combustion products out of the combustor through the inlet section. The main advantage of aerodynamic conflgurations is lack of valves and moving parts so the risk of mechanical breakdown or failure is eliminated. This is a key consideration for heavy-duty pulse combustion burners where the inlet section undergoes severe operating conditions. 

An alternative design of a pulse combustor is a so-called valveless combustor in which the mechanical valves are replaced with an aerodynamic diode in the form of a profiled orifice in the inlet pipe, contoured diffuser, or a shrouding duct [28] (Figure 20.15). Similarly to the combustor with mechanical valves, the high-temperature gases from a combustion chamber start to flow just after a... 

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