ROTARY ENGINE WITH DISTRIBUTED FUEL INJECTION

BACKGROUND

[0001] The present disclosure claims priority to and incorporates herein United States Provisional Patent Application No. 61/107,321, filed October 21, 2008. [0002] The present disclosure relates to a rotary engine.

[0003] Engine technology provides various tradeoffs between power density and fuel consumption. Gas turbine engine technology provides reasonably high power densities, but at relatively small sizes, fuel consumption is relatively high and efficiencies are relatively low. Small diesel piston engines have reasonable fuel consumption but may be relatively heavy with power densities typically below approximately 0.5 hp/lb while equivalently sized four-stroke engines have power densities typically below approximately 0.8 hp/lb. Two- stroke engines have greater power densities than comparably sized four-stroke engines, but have relatively higher fuel consumption.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiment. The drawings that accompany the detailed description can be briefly described as follows: [0005] Figure 1 is a schematic block diagram view of an exemplary rotary engine;

[0006] Figure 2 is a partial phantom view of an exemplary rotary engine; [0007] Figure 3 is a partially assembled view of the exemplary rotary engine of Figure 1 illustrating the first rotor section;

[0008] Figure 4 is a partially assembled view of the exemplary rotary engine of Figure 1 illustrating the power section;

[0009] Figure 5 is an exploded view of the rotary engine;

[0010] Figure 6 is a front view of a rotor housing to illustrate the multiple of discrete fuel jets distributed across the second rotor volume;

[0011] Figure 7 is an expanded face view of a fuel jet illustrating the fuel orifices thereof;

[0012] Figure 8 is a side view of a rotor housing to illustrate the multiple of discrete fuel jets distributed across the second rotor volume;

[0013] Figure 9 is a sectional plan view of the multiple of discrete fuel jets distributed across the second rotor volume; and [0014] Figure 10 is a sectional plan view of anther non-limiting embodiment of a multiple of discrete fuel jets distributed across the second rotor volume.

DETAILED DESCRIPTION

[0015] Figure 1 schematically illustrates a compound rotary engine 20 having a first rotor section 22 and a second rotor section 24. The rotary engine 20 is based on a rotary, e.g., Wankel-type engine. An intake port 26 communicates ambient air to the first rotor section 22 and an exhaust port 28 communicates exhaust products therefrom. A first transfer duct 30 and a second transfer duct 32 communicate between the first rotor section 22 and the second rotor section 24. A fuel system 36 for use with a heavy fuel such as JP-8, JP-4, natural gas, hydrogen, diesel and others communicate with the second rotor section 24 of the engine 20. The engine 20 simultaneously offers high power density and low fuel consumption for various commercial, industrial, compact portable power generation, and aerospace applications.

[0016] Referring to Figure 2, the compound rotary engine 20 generally includes at least one shaft 38 which rotates about an axis of rotation A. The shaft 38 includes aligned eccentric cams 40, 42 (Figures 3 and 4) which drive a respective first rotor 44 and second rotor 46 which are driven in a coordinated manner by the same shaft 38. The first rotor 44 and second rotor 46 are respectively rotatable in volumes 48, 50 formed by a stationary first rotor housing 52 and a stationary second rotor housing 54 (Figures 3 and 4). The fuel system 36, in one non- limiting embodiment, includes one or more fuel injectors with two fuel injectors 36A, 36B shown in communication with the second rotor volume 50 generally opposite the side thereof where the transfer ducts 30, 32 are situated in one non-limiting embodiment. It should be understood that other fuel injector arrangement, locations and numbers may alternatively or additionally be provided. The fuel system 36 supplies fuel into the second rotor volume 50. The first rotor volume 48 in one non-limiting embodiment provides a greater volume than the second

rotor volume 50. It should be understood that various housing configurations shapes and arrangements may alternatively or additionally be provided (Figure 5).

[0017] The first rotor 44 and the second rotor 46 have peripheral surfaces which include three circumferentially spaced apexes 44A, 46A respectively. Each apex 44A, 46A include a apex seal 44B, 46B, which are in a sliding sealing engagement with a peripheral surface 48P, 5OP of the respective volumes 48, 50. The surfaces of the volumes 48, 50 in planes normal to the axis of rotation A are substantially those of a two-lobed epitrochoid while the surfaces of the rotors 44, 46 in the same planes are substantially those of the three-lobed inner envelope of the two-lobed epitrochoid. [0018] In operation, air enters the engine 20 through the intake port 26 (Figure 1).

The first rotor 44 provides a first phase of compression and the first transfer duct 30 communicates the compressed air from the first rotor volume 48 to the second rotor volume 50 (Figures 2 and 3). The second rotor 46 provides a second phase of compression, combustion and a first phase of expansion, then the second transfer duct 32 communicates the exhaust gases from the second rotor volume 50 to the first rotor volume 48 (Figures 2 and 4). The first rotor 44 provides a second phase of expansion to the exhaust gases, and the expanded exhaust gases are expelled though the exhaust port 28 (Figures 1 and T). The shaft 38 completes one revolution for every cycle, so there are three (3) crank revolutions for each complete rotor revolution. As each rotor face completes a cycle every revolution and there are two rotors with a total of six faces, the engine produces significant power within a relatively small displacement.

[0019] Referring to Figure 6, each of the fuel injectors 36A, 36B are located within the second rotor housing 54 to disperse a multiple of discrete fuel jets F1-F4 into the second rotor volume 50. Although the fuel injectors 36A, 36B are illustrated in particular positions in the disclosed non-limiting embodiment, it should be understood that the fuel injectors 36A, 36B may be located in other positions and orientations other than those illustrated. It should also be understood that although four fuel jets F1-F4 are illustrated in the disclosed non-limiting embodiment as being directed from each fuel injector 36A, 36B, any number and pattern may benefit herefrom.

[0020] Referring to Figure 7, each of the multiple of discrete fuel jets F1-F4 are defined by a respective fuel orifice fl-f4. The respective fuel orifice fl-f4 are of a predefined diameter or shape to define the respective fuel jet F1-F4. Although the fuel orifice fl-f4are

illustrated in particular positions in the disclosed non-limiting embodiment, it should be understood that the fuel orifice fl-f4 may be located in other positions and orientations other than those illustrated. Furthermore, fuel provided to the respective fuel orifice fl-f4 may be along a particular path to time the fuel flow from the respective fuel orifice fl-f4. For example, only a longer fuel path to fuel orifice f4 than fuel orifice f 1 will delay fuel jet F4 relative to fuel jet Fl.

[0021] Referring to Figure 8 and 9, the multiple of discrete fuel jets F1-F4 are distributed with respect to the depression 46D in each peripheral surface or face 46P of the second rotor 46 as the depression 46D rotates into the ignition cycle. [0022] The multiple of discrete fuel jets F1-F4 are directed across the second rotor volume 50 from a near field to a far field of the depression 46D along the axis of rotation A. The multiple of discrete fuel jets F1-F4 are also distributed along the width - apex-to-apex - of the second rotor volume 50 along the depression 46D defined around the axis of rotation A (Figure 8). The fuel jets F1-F4 direct fuel in the direction of rotation and typically initiate fuel injection approximately fifteen degrees before second rotor 46 top dead center (TDC) and complete the fuel injection approximately fifteen degrees after top dead center (TDC). Although the fuel is directed in the direction of rotation as illustrated in the disclosed non-limiting embodiment, it should be understood that the fuel jets may alternatively or additionally be directed otherwise.

[0023] The multiple of discrete fuel jets F1-F4 provide a penetration length and mixing time which is generally controlled by the diameter and the pressure of the fuel jet F1-F4. The relatively smaller diameter jets are tailored for mixing and ignition enhancement while the relatively larger diameter jets provide for full penetration across the second rotor volume 50. That is, the relatively smaller diameter jets mix quickly as compared to relatively larger diameter jets which mix more slowly. [0024] In one non-limiting embodiment, fuel jets Fl, F2 are of a relatively smaller diameter and shorter than fuel jets F3, F4. Fuel jets Fl, F2 are distributed in the near field while fuel jets F3, F4 are distributed to the far field. Also, fuel jet F4 is angled relative to fuel jets Fl, F2, F3 such that fuel jet F4 is directed directly across the depression 46D. Fuel jets Fl, F2, F3 are distributed in a pattern across the depression 46D but displaced from fuel jet F4. Fuel jet F4 lags fuel jets Fl, F2, F3 with regard to a rotational direction of the second rotor 46. It should be understood that alternative distributions may be provided.

[0025] The multiple of discrete fuel jets F1-F4 may be of various sizes to facilitates controlled fuel distribution and controlled mixing which optimizes plume compatibility, high compression ratios and direct mixing to facilitate low specific fuel consumption and low weight propulsion systems for vehicles such as Unmanned Aerial Vehicles (UAVs). [0026] Fuel jet penetration and direction are designed to control fuel distribution within the second rotor chamber 50 so as to provide a desired resultant fuel mix rate and controlled mixing. The fuel mix rate and controlled mixing may be tailored to, for example, a desired pressure profile. Furthermore, the multiple of discrete fuel jets F1-F4 may be staged circumferentially to drive the air charge in a predetermined direction. That is, the multiple of discrete fuel jets F1-F4 operate in a predetermined sequence. Control of the predetermined sequence may be provided, for example, by the length of the fuel paths within the each of the fuel injectors 36A, 36B which generate the multiple of discrete fuel jets F1-F4

[0027] In one example, the fuel jet penetration and direction are designed with regard to limit the pressure experienced by the apex seals 46B. If, for example, the Figure 8 fuel jet array provides too rapid of mixing, the jet size may be too small. Fuel jet F4 may thus be made larger, redirected so that fuel jet F4 is no longer directed directly across the depression 46D or a combination thereof to slow the mixing rate such as in FigurelO. In other words, the controlled mixing may be adjusted from a relatively smaller jet directed directly across the depression 46D which may provide too high a pressure upon the apex seals 46B to a relatively larger jet which is directed at an angle to mix more slowly and stretch out the combustion process over a longer period of time to thereby reduce the pressure.

[0028] It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom.

[0029] Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure.

[0030] The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above

teachings will fall within the scope of the appended claims. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content.