Asymmetric side-exhausting nozzles

The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to me of any royalties thereon.

In the past, missile propulsion systems have used canted nozzles. The need for the canted nozzle arises when there is a requirement to have the missile base area free for guidance and control functions or in cases where forward facing thrust reversing nozzles are required. The most common arrangment of canted nozzles is that of multiple nozzles that are arranged symetrically about the missile axis. There are applications where a single canted nozzle is used. In some applications, such as nozzles exiting through the side of the missile, the nozzle terminates along the line of intersection of the nozzle exit cone and the missile's outer skin. The resulting configuration is called a scarfed nozzle. Exiting the propulsion mass flow to the side of the missile rather than along the axis results in a thrust loss that is proportional to the cosine of the nozzle cant angle. Accordingly, it can be appreciated that there is a need for minimizing propulsion loss in the use of canted nozzles.

Therefore it is an object of this invention to reduce the propulsion lose in canted nozzles by misaligning the flow entering the nozzle relative to the flow through the nozzle.

Another object of this invention is to provide a nozzle which has improved performance in thrust loss.

Other objects and advantages of this invention will be obvious to those skilled in this art.

In accordance with this invention, an asymmetric side exhausting nozzle is provided in which the throat plane of the exhaust nozzle is canted relative to the exhaust axis through the nozzle to improve the performance of the nozzle relative to the thrust produced.

FIG. 1 is a sectional view partially cut-away and illustrating a prior art side exhausting nozzle, and

FIG. 2 is a sectional view partially cut-away of an exhaust nozzle in accordance with this invention that has improved performance.

Referring now to the drawings, a prior art nozzle is illustrated in FIG. 1 and includes a throat 12 that has a plane 14 which is perpendicular to an axis 16 of the nozzle and exhaust plane 18 of the nozzle is likewise perpendicular to the axis through the nozzle. In a conventional side exhausting nozzle as illustrated in FIG. 1, the net thrust vector is normal to throat plane 18 at the throat plane and is also aligned with the nozzle exit axis. This alignment of the thrust and nozzle exit axis continues until the scarfed section of the nozzle is reached, where a small turning of the thrust vector occurs. This turning of the thrust vector is caused by the pressure distribution on lower wall 20 which is not balanced because of the absence of an opposite or upper wall in this region.

Applicant has discovered that the nozzle performance can be improved as illustrated in FIG. 2, wherein the nozzle throat 22 is skewed so that plane 24 is not normal or perpendicular to exit axis 26 of the nozzle. The thrust vector of throat 22 is normal to the throat plane at the throat, but it is no longer aligned with the nozzle exit axis 26. The direction of the thrust vector through throat 22 is caused to oscillate as the flow procedes down the nozzle. For any given configuration, the degree of throat plane skew can be selected to minimize the thrust vector angle at the nozzle exit plane or at the end of the scarfed extenion for a scarfed nozzle. Proper selection of nozzle parameter such as the throat radius of curvature and nozzle half-angle results in a reduction of the thrust vector angle by some fraction of the throat plane skew angle. Applicant has found that the skew angle for the nozzle can vary from about 2 degrees up to an angle approaching the nozzle half-angle. Since the performance of side exhausting nozzles is proportional to the cosine of the thrust vector angle, performance improvements are significant and in the order of 1 to 3 percent.