Acoustic pulsejet helmet

#The invention relates generally to pulsejet engines and more particularly to valve-less pulsejet engines that direct all thrust forces along an axis of positive thrust.

#Pulsejet engines are extraordinarily simple devices that provide an inexpensive means to provide thrust for an aircraft. Most pulsejets typically include a mechanical valve to prevent air and thrust from escaping through the inlet of the pulsejet when combustions occur in the combustion chamber of the pulsejet. A main disadvantage of these pulsejets is that they generally have a low efficiency and the mechanical valves have a limited durability. Some more recent pulsejet designs have implemented a pneumatic air inlet valve that eliminates the durability problem of the mechanical inlet valve. The pneumatic air valve generally injected air into a throat section of the inlet nozzle as the fuel in the combustion chamber ignited. This created a high pressure zone at the inlet nozzle throat that prevented thrust from the fuel combustion from escaping out the inlet. Notwithstanding the removal of the mechanical valve and greatly improved durability, implementation of the pneumatic air valve required supplemental equipment to provide and inject the air into the inlet nozzle of the pulsejet. And, the amount and complexity of the additional supplemental equipment significantly increases as the number of pulsejets included in a system multiply.

#Additionally, a typical bank of pulsejets would include a plurality of round pulsejets aligned in columns and rows. In this configuration, the pulsejets where interconnected using a webbing of orthogonal walls that formed a grid of square compartments with a single pulsejet within each compartment. The interconnected webbing adds considerable weight to each pulsejet bank and the space created by round pulsejets in square compartments created gaps that could allow a portion of the thrust generated by each pulsejet to escape in the wrong direction.

#The present invention will become more fully understood from the detailed description and accompanying drawings, wherein:

#FIG. 1A is an isometric cross sectional view of the valve-less pulsejet engine, in accordance with various embodiments of the present inventions;

#FIG. 1B is a cross sectional side view of the pulsejet engine shown in FIG. 1A;

#Corresponding reference numerals indicate corresponding parts throughout the several views of drawings.

#The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application or uses. Additionally, the advantages provided by the preferred embodiments, as described below, are exemplary in nature and not all preferred embodiments provide the same advantages or the same degree of advantages.

#FIGS. 1A and 1B are cross sections of the valve-less pulsejet engine, in accordance with various embodiments of the present inventions. The pulsejet engine will simply be referred to herein as the pulsejet 10. The pulsejet 10 includes a body 12 having an inlet 14, an exhaust nozzle 18, a combustion chamber 22 between the inlet 14 and the exhaust nozzle 18, and a flow turning device 26, herein referred to as a helmet 26, positioned over an end of the inlet 14. An air flow pathway (AFP) 30 through which air flows into and out of the pulsejet 10 is formed between a side wall 34 of the helmet 26 and an outer portion of the pulsejet 10 near combustion chamber 22 and the inlet 14. In various embodiments, as shown in FIG. 1, the AFP 30 is an annular AFP. In operation of the pulsejet 10, a propulsion cycle comprises an air intake phase, a compression phase and a combustion phase. Generally, during the compression phase, intake air flows through the AFP 30 in the A direction and enters the inlet 14. The intake air is mixed with fuel injected into the combustion chamber 22 and detonated during a combustion phase due to pressure created inside the combustion chamber 22. More particularly, initially air is injected into the combustion chamber 22 to mix with the injected fuel and an ignition source is provided to cause the air/fuel mixture to combust during at least one initial combustion phase. Each air/fuel combustion produces exhaust thrust that discharges from the exhaust nozzle 18 in B direction. This exhaust thrust will be referred to herein as the primary exhaust or primary thrust. Each combustion phase additionally produces exhaust thrust that exits the combustion chamber 22 through the inlet in the C direction. Thrust exiting the combustion chamber 22 through the inlet 14 of the pulsejet 10 will be referred to herein as secondary exhaust or secondary thrust.