Introduction and Performance Prediction of a Nutating-Disk Engine

Abstract

A new type of internal combustion engine and its thermodynamic cycle are introduced. The core of the engine is a nutating nonrotating disk, with the center of its hub mounted in the middle of a Z-shaped shaft. The two ends of the shaft rotate, while the disk nutates. The motion of the disk circumference prescribes a portion of a sphere. A portion of the area of the disk is used for intake and compression, a portion is used to seal against a center casing, and the remaining portion is used for expansion and exhaust. The compressed air is admitted to an external accumulator, and then into an external combustion chamber before it is admitted to the power side of the disk. The accumulator and combustion chamber are kept at constant pressures. The engine has a few analogies with piston-engine operation, but like a gas turbine it has dedicated spaces and devices for compression, burning, and expansion. The thermal efficiency is similar to that of comparably sized simple-cycle gas turbines and piston engines. For the same engine volume and weight, this engine produces less specific power than a simple-cycle gas turbine, but approximately twice the power of a two-stroke engine and four times the power of a four-stroke engine. The engine has advantages in the 10 kW to 200 kW power range. This paper introduces the geometry and thermodynamic model for the engine, presents typical performance curves, and discusses the relative advantages of this engine over its competitors.

Thermodynamic analysis of nutating disc engine topping cycles for aero-engine applications

“…This engine concept is referred to as the Nutating Disc (ND) engine. The operation of the ND engine, as well as the definition of its thermodynamic performance, is described by Korakianitis et al [13] The ND engine ( Fig. 2(a)) uses separate chambers for compression, combustion and expansion processes, in comparison to most piston engines, where all the processes take place within the same chamber.…”

“…2(a)) uses separate chambers for compression, combustion and expansion processes, in comparison to most piston engines, where all the processes take place within the same chamber. Its operation is more comparable to that of a gas turbine since the thermodynamic processes are carried out in separate components [13]. A unique feature of the ND engine is its ability to use both sides of its working disc during a full shaft revolution.…”

“…2(a) illustrates the components of a naturally-aspirated singledisc nutating-disc engine. The layout comprises an inlet, compression chamber, accumulator, combustion chamber, expansion chamber and exhaust manifold, with the nutating disc mounted inside the compressor and expander chambers [13]. The disc itself is basically bi-conical with a spherical hub.…”

“…Optionally, the two discs may have different sizes in order to optimise the overall design. Korakianitis et al claim the operational benefits offered by the ND engine include significantly lower bearing loads relative to piston engines, a relatively smooth torque curve to ensure high mechanical transmission efficiency, and a high power to volume ratio [13]. These features of the ND engine make it an attractive potential candidate for an aero-engine.…”

“…To date, the state-of-the-art work reported on the ND engine is that performed by Korakianitis et al In addition to having presented the thermodynamic model of the ND engine [13], the performance of a multi-disc ND engine configuration and the potential of using single-disc ND engines for unmanned aerospace vehicle (UAV) applications have been presented [14] [15]. The conclusions drawn from [14] claim that the ND engine in the dual-disc engine configuration offers a significant degree of design flexibility in terms of providing variable-compression ratio and having an expansion ratio greater than the compression ratio.…”