costs and less rotational mass. Wankel rotary combustion engines Yanmar Diesel, a Japanese engine maker, was pioneer in introducing reed valves for flow control at intake ports of its small Wankel engines, showing an improvement in torque and performances at low rpm and under partial load of the engine. Toyota discovered the benefits of injecting fresh air into the Wankel RCE exhaust port, and also used a reed valve in prototypes where they tested the SCRE concept (Stratified Charge Rotary Engine). However, this kind of intake port arrangement never reached the production line for automobile size RCEs. According to David W. Garside, who developed the Norton line of Wankel-powered motorcycles, data from other RCE producers pointed that reed valves do improve performances at low rpm and under partial load, but reduce the high speed power output of the engine, a feature considered inconvenient for motorcycle engines. Pulse jets Reed valves are used in the cheap but inefficient pulse jet engine, such as the one used by the Argus As 014 engine in the German V-1 (flying bomb). The valves at the front of the cylindrical engine are opened by the low pressure in the combustion chamber caused by the resonance of the air column in the engine, fuel is squirted into the combustion chamber and ignited by the hot combustion gases of the previous cycle. Once the charge has expanded and mostly left the engine, pressure inside drops again to below-atmospheric values and the reed valve allows fresh air to enter and the cycle be repeated. Some ram-air pressure due to forward motion helps scavenging and filling the combustion chamber with the new, fresh air charge, thus improving the power of the engine at higher speeds. Design and modelling Reed valves are designed considering the pressure gradient and mass flow. The pressure gradient is used to evaluate the valve lift during open condition; the lift and overall component geometry (considering also a pressure loss coefficient) are then used to calculate the mass flow. For high speed applications (compressors and engines) the dynamic response has to be considered. A simple approach consists in the evaluation of first eigenvalue that is compared with exciting frequency. Design of reed valves can be refined using simulations. The dynamic of petals can be studied neglecting the coupling between fluid and structure: in this case the evolution of the structural part are simulated using lumped parameters