US20120315172A1

US20120315172A1 - Supplemental compounding control valve for rotary engine

Info

Publication number: US20120315172A1
Application number: US13/497,563
Authority: US
Inventors: Mark David Horn
Original assignee: Pratt and Whitney Rocketdyne Inc
Current assignee: Aerojet Rocketdyne of DE Inc
Priority date: 2009-10-08
Filing date: 2009-10-08
Publication date: 2012-12-13
Also published as: JP5496346B2; CN102667101A; WO2011043773A1; JP2013507560A; EP2486258A4; EP2486258A1

Abstract

A rotary engine includes a first transfer duct between a first rotor section and a second rotor section. A second transfer duct is between the second rotor section and the first rotor section. A supplemental compounding control valve selectively controls communication between the first transfer duct and the second transfer duct.

Description

BACKGROUND

The present disclosure relates to a rotary engine.
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

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:

FIG. 1 is a schematic block diagram view of an exemplary rotary engine;

FIG. 2 is a partial phantom view of an exemplary rotary engine;

FIG. 3 is a partially assembled view of the exemplary rotary engine of FIG. 1 illustrating the first rotor section;

FIG. 4 is a partially assembled view of the exemplary rotary engine of FIG. 1 illustrating the second rotor section;

FIG. 5 is an exploded view of the rotary engine;

FIG. 6 is one non-limiting embodiment of a supplemental compounding control valve between a first transfer duct and a second transfer duct with the second rotor schematically translated up and rotated 180 degrees about horizontal and vertical axes for illustrative purposes;

FIG. 7 is a chart of supplemental effects in response to various supplemental compounding control valve positions; and

FIG. 8 is a graphical representation of the supplemental compounding effect with respect to a continuum of supplemental compounding control valve positions.

DETAILED DESCRIPTION

FIG. 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.
Referring to FIG. 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 (FIGS. 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 (FIGS. 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 (FIG. 5).
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 an apex seal 44B, 46B, which are in a sliding sealing engagement with a peripheral surface 48P, 50P 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.
In operation, air enters the engine 20 through the intake port 26 (FIG. 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 (FIGS. 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 (FIGS. 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 (FIGS. 1 and 2). 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.
The shaft completes one revolution for every cycle, so there are three (3) crank revolutions for each complete rotor revolution. At the top dead center (TDC) position for the first rotor 44, the first rotor volume outlet port 48O and the first rotor volume inlet port 48I are in momentary communication. A supplemental compounding effect is thereby achieved as exhaust gases which are returned from the second rotor volume 50 through the second transfer duct 32 and first rotor volume inlet port 48I flow into the first rotor volume 48 then back into the first transfer duct 30 through the first rotor volume outlet port 48O for communication back into the second rotor volume 50. As the higher pressure exhaust gases are forced into the fixed volume of the first transfer duct 30, the residual compressed air within the first transfer duct 30 is forced into the second rotor volume 50. The residual compressed air from within the first transfer duct 30 is communicated into the second rotor volume 50 which thereby increases the effective compression ratio of the engine 10 through movement of the additional or supplemental air mass flow into the second rotor volume 50 to thereby increase or compound the initial pressure prior to the start of the second rotor 46 compression stroke. With the fixed, geometry defined compression ratio of the second rotor 46, the higher initial pressure for the second rotor 46 stroke results in a higher peak pressure from combustion. This higher pressure, combined with the increased air mass capture, results in increased power output for the engine 10.
Referring to FIG. 6, the supplemental compounding effect may be tuned with a supplemental compounding control valve 60 in communication with a bypass duct 62 between the first transfer duct 30 and the second transfer duct 32. A first check valve 64 may be located within the first transfer duct 30 adjacent to the compressor volume 48. A first bypass duct check valve 66 may be located within the bypass duct 62 adjacent to the first transfer duct 30. A second bypass duct check valve 68 may be located within the bypass duct 62 adjacent to the second transfer duct 32. The check valves 64, 66, 68 assure that the exhaust gases are returned from the second rotor volume 50 through the second transfer duct 32, into the first rotor volume 48 and back into the first transfer duct 30 under control of the supplemental compounding control valve 60. It should be understood that various additional or alternative valve arrangements may be utilized to control the flow within the bypass duct 62 in an alternative bi-directional manner.
The supplemental compounding control valve 60 may be utilized to control the supplemental compounding effect at various points in the engine cycle to increase throttling performance, altitude performance and emissions control with a module 70 which executes a supplemental compounding algorithm 72. The functions of the algorithm 72 are, for example, disclosed in terms of a chart (FIG. 7), and it should be understood by those skilled in the art with the benefit of this disclosure that these functions may be enacted in either dedicated hardware circuitry or programmed software routines capable of execution in a microprocessor based electronics control embodiment. In one non-limiting embodiment, the module 70 may be software, a portion of a control system, or a stand-alone line replaceable unit or other system.
The module 70 typically includes a processor 70A, a memory 70B, and an interface 70C. The processor 70A may be any type of known microprocessor having desired performance characteristics. The memory 70B may, include various computer readable mediums which store the data and control algorithms described herein. The interface 70C facilitates communication with a flight control computer (FCC) 74, as well as other avionics and systems in the disclosed non-limiting embodiment typical of an unmanned aerial vehicle (UAV).
Referring to FIG. 8, the supplemental compounding control valve 60 may be selectively moved along a continuum between a closed position and an open position in response to the module 70. Generally, the greater the portion of exhaust gas that is communicated through the supplemental compounding control valve 60, the greater the supplemental compounding effect. That is, the basic effect is one of more moles of air forced into a fixed volume prior to the start of the second rotor compression stroke.
Toward the closed position of the supplemental compounding control valve 60, the peak combustion pressure is minimized to provide for significant engine life. Minimal supplemental compounding occurs as the fixed port geometry between the compressor outlet port 48O and the compressor inlet port 48I alone achieve the minimum inherent supplemental compounding. Toward the open position of the supplemental compounding control valve 60, the effective compression ratio (peak combustion pressure with respect to atmospheric pressure) may be controlled with respect to altitude to generate a desired horsepower. The open position may also be utilized to maximize pressure and facilitate a cold start. The supplemental compounding control valve 60 is then selectively closed as the engine reaches operational temperature to provide a relatively fast engine warm-up. It should be understood that various positions along a continuum between the open and closed positions may be used at various operating conditions to provide desired operational effects.
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.
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.
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.

Claims

1. A rotary engine comprising:

a first rotor section;

a second rotor section;

a first transfer duct between said first rotor section and said second rotor section;

a second transfer duct between said second rotor section and said first rotor section; and

a supplemental compounding control valve which controls communication between said first transfer duct and said second transfer duct.

2. The rotary engine as recited in claim 1, wherein said first transfer duct communicates compressed air from said first rotor section to said second rotor section.

3. The rotary engine as recited in claim 1, wherein said second transfer duct communicates exhaust gases from said second rotor section to said first rotor section.

4. The rotary engine as recited in claim 3, wherein said supplemental compounding control valve is within said second transfer duct.

5. The rotary engine as recited in claim 1, further comprising a bypass duct between said first transfer duct and said second transfer duct, said supplemental compounding control valve within said second transfer duct.

6. The rotary engine as recited in claim 5, further comprising at least one check valve within said bypass duct.

7. The rotary engine as recited in claim 1, wherein said first rotor section provides a first stage of compression and said second rotor section in communication with said first rotor section through said first transfer duct to provide a second stage of compression, a combustion stage and a first stage of expansion, said second rotor section in communication with said first rotor section through said second transfer duct to provide a second stage of expansion,

8. The rotary engine as recited in claim 1, further comprising a module which controls operation of said supplemental compounding control valve.

9. The rotary engine as recited in claim 8, wherein said module communicates with a flight control computer.

10. A method of controlling a rotary engine comprising:

communicating compressed air from a first rotor section to a second rotor section through a first transfer duct;

communicating exhaust gases from the second rotor section to the first rotor section through a second transfer duct; and

selectively controlling communication between the first transfer duct and the second transfer duct.

11. A method as recited in claim 10, further comprising:

selectively controlling communication between the first transfer duct and the second transfer duct to control peak combustion pressure.

12. A method as recited in claim 10, further comprising:

selectively controlling communication between the first transfer duct and the second transfer duct to control peak combustion pressure with respect to atmospheric pressure.

13. A method as recited in claim 10, further comprising:

selectively controlling communication between the first transfer duct and the second transfer duct to control engine power.

14. A method as recited in claim 10, further comprising:

selectively controlling communication between the first transfer duct and the second transfer duct to control engine life.

15. A method as recited in claim 10, further comprising:

selectively controlling communication between the first transfer duct and the second transfer duct to control engine start.