Patent Application
20130333656
A portion of the disclosure of this patent document contains drawing materials that are subject to copyright protection. The owner has no objection to the facsimile reproduction by anyone of the patent document or patent disclosure, as it appears in the U.S. Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
The present disclosure relates to aircraft engines, and more specifically, to improved designs for valve seats in cylinder heads in aircraft engines.
Aircraft engines commonly in use in general aviation aircraft are primarily provided in an internal combustion, multi-cylinder, spark ignition configuration which is set up for the combustion of high octane aviation gasoline. Such engines are generally air cooled, with individually mounted cylinders, which in the trade are often called cylinder “jugs”. Cylinder jugs typically include a head portion and a cylinder portion. Each of such portions usually includes a plurality of cooling flanges to exchange heat with air passing the cylinder. Each engine is configured to route incoming combustion air through the head portion to the cylinder, and to route the hot exhaust gases out of the cylinder through the head portion to an exhaust header or manifold. Control of relatively cool combustion air entering the cylinder, and of hot exhaust gases leaving the cylinder, is accomplished by intake and exhaust valves operating in conventional fashion.
Cylinder heads in current general aviation aircraft engine designs include inlet passageways for incoming air flow, and outlet passageways for the outgoing exhaust gases, each of which passageways were in most cases designed decades ago. Little attention seems to have been given to optimizing the engine power output by optimization of the flow path for the incoming air, or of the flow path for the outgoing hot exhaust gases, or to the various portions of the intake valve seat, or to the various portions of the exhaust valve seat.
In various non-aviation engines, some attempts have been made, with varying degrees of success, to provide an upgrade to the inlet passageways or inlet valve seats, or to the exhaust valve seats or exhaust outlet passageways, to at least in part compensate for poor original designs of cylinder head components. With regard to inlet air passageways, an attempt at obtaining improved performance is described in U.S. Pat. No. 4,159,011, issued Jun. 26, 1979, for an Engine Cylinder Inlet Port, and which was assigned to General Motors Corporation, of Detroit, Michigan. In the described apparatus, a shaped flow deflector provided some improvement with respect to inlet air flow; however, that design leaves considerable room for improvement. With regard to exhaust gas outlet passageways, an attempt to obtain improved performance is described in U.S. Pat. No. 4,537,028, issued Aug. 27, 1985, for an Exhaust Port, and which is assigned to Deere & Company, of Moline, Ill.. In that design, flow dividers were provided around a valve stem, which reduced flow separation and loses. However, the configurations of such cylinder heads allow somewhat more latitude in what may be adjusted than the typical aircraft engine cylinder, and the aircraft cylinder heads and passageways therein.
Thus, in spite of prior art for attempts at improving air flow in other types of internal combustion, multi-cylinder spark ignition engines, there still remains an as yet unmet need for an improved cylinder head, including the intake valve seats and the exhaust valve sates in aircraft engines which can simply and effectively improve total engine power output. It would be advantageous to provide such a design by unique modifications to the current designs used for intake and exhaust valve seats in aircraft cylinder heads, so that adjacent (or other) engine components could be used with little or no modification (except as may be advantageous or necessary to accommodate the air flow volume and power output improvements as taught herein). Importantly, the use of such an improved intake valve seats and exhaust valve seats in an improved cylinder head design would provide increased horsepower output from existing aircraft engines. Such improvement would be particularly helpful when maximum engine performance is required, such as for short field takeoffs, and/or in high density altitude conditions. Alternatively, and just as important, an improved engine, using improved cylinder head designs as described herein, may be utilized in a method of operation to reduce fuel consumption at a given horsepower output, as compared to fuel consumption rates in engines that use existing cylinder head designs and components. Thus, fuel consumption for a given trip distance would decrease, as compared to a prior art engine design; such improved performance would also extend the range of an aircraft employing such improved cylinder head designs.
Novel cylinder heads for aircraft engines as disclosed herein include an inlet passageway that is optimized to allow maximum airflow, by minimizing pressure drop (friction and flow turbulence losses) of air traversing through the inlet air passageway. Further, the inlet valve seat is optimized in shape to minimize pressure drop at inlet air flow rates. Likewise, the outlet valve seat is optimized in shape to minimize pressure drop as hot exhaust gases pass outward therethrough. And finally, the hot exhaust passageway is optimized to allow maximum exhaust flow, by minimizing the pressure drop (including friction and flow turbulence losses) experienced by exhaust gases, by minimizing obstructions to the outbound passage of high velocity hot exhaust gases.
The novel cylinder heads described herein are particularly advantageous in that they are configured to allow installation by an engine manufacturer on a new engine otherwise using existing design configurations, and thus allowing an increase in the horsepower output without the necessity to modify various other existing components. And, such novel cylinder heads (including novel intake and exhaust valve seats) could be substituted in the field, for example, during a “top overhaul” of an aircraft engine, to likewise improve horsepower output of a selected engine, and/or to reduced fuel consumption at a selected power output, as compared to the stock cylinders and heads. Such novel cylinder heads may be provided for overhauls as the key component of factory provided new cylinder kits for use in overhauls of existing engines.
Further, in an embodiment, it is an advantage that improved intake valves and intake valve seat configurations, and/or improved exhaust valves and exhaust valve seat configurations, may be used to provide yet further increases in power output, and in fuel economy, as compared to cylinder designs that only include new, improved inlet passageway and/or exhaust passageway designs described herein.
It is an advantage that improved cylinder heads provided by the designs disclosed herein may be manufactured using aluminum alloy castings, as presently used in many existing aircraft cylinder head designs.
These and other objects, advantages, and novel features of the cylinder head designs for aircraft engines as described herein will become apparent to the reader from the foregoing and from the appended claims, and the ensuing detailed description, as the discussion below proceeds in connection with examination of the accompanying figures of the drawing.
I have now developed improved intake valve seats and exhaust valve seats designed for aircraft engines. Such components may be easily and quickly installed in existing cylinder heads, or new engines that are otherwise of existing design, or may be easily and quickly installed on used engines, such as during an overhaul, when it may be useful to install new cylinders and related components, such as valves and/or cylinder heads.
The novel aircraft intake valve seat and exhaust valve seat designs disclosed herein may be scaled up or down as appropriate for the inlet airflow volume and exhaust gas flow volume resulting from the displacement provided by a particular cylinder. As an example, Lycoming Engines (a division of AVCO Corp., a Textron subsidiary), of Williamsport, Pa., produces a line of horizontally opposed, air cooled aircraft engines, with four, six, and eight cylinders, which in various configurations have from about 58 cubic inches displacement per cylinder to about 90 cubic inches displacement per cylinder. While the cylinder bore and head component dimensions for the various displacement sized cylinders are adjusted accordingly, the general principles described and claimed herein may be applied, and size variances easily accommodated.
The foregoing briefly describes certain aspects and elements of exemplary intake valve seats and exhaust valve seats for use in cylinder heads for aircraft engines, and various components thereof. The various objectives, features and advantages of the invention(s) will be more readily understood upon consideration of the detailed description, taken in conjunction with careful examination of the accompanying figures of the drawing.
In order to enable the reader to attain a more complete appreciation of the invention, and of the novel features and advantages thereof, attention is directed to the following detailed description when considered in connection with the accompanying figures of the drawing, wherein:
In the figures of the drawing, like features may be illustrated with the same reference numerals, without further mention thereof. Further, the drawing figures are merely exemplary, and may contain various elements that might be present or omitted from actual implementations of certain embodiments. An attempt has been made to draw the figures in a way that illustrates at least those elements that are significant for an understanding of the invention. However, the drawings are generalized in the interest of clarity and conciseness. Notably, other elements or functional components for an improved combustion air inlet passageway, an improved hot exhaust gas exit passageway, and improved valve designs, may be utilized in order to provide useful performance enhancing components for aircraft engines, while within the literal scope and coverage of the claims set forth herein, or legal equivalents thereof.
Attention is directed to
In the embodiment shown in
As shown in the schematic view provided at
As seen in
The inlet passageway 70 has inlet passageway sidewalls 80 that cooperate to define, between the upstream inlet 72 and the intake valve seat surface 42, an inlet passageway volume IPV for the inlet passageway 70. In an embodiment, the inlet passageway volume IPV may be about thirty percent (30%), or less, of the swept displacement volume DV as described above. In an embodiment, the inlet passageway volume IPV may be about twenty eight percent (28%), or less, of the swept displacement volume DV. In an embodiment, the inlet passageway volume IPV may be about twenty five percent (25%) or less, of the swept displacement volume DV.
As better seen in
As may be seen
Turning now to
As seen in
As may be appreciated from
In order to further increase the performance of an engine utilizing the designs taught herein, additional refinements may be made to the configuration of intake valve 32, and more particularly, the configuration of the intake valve seating face angle alpha (α), as noted in
In order to provide yet further increase in the performance of an engine utilizing the designs taught herein, additional refinements may be made to the configuration of exhaust valve 34, and more particularly, to the configuration of the exhaust valve seating face 44. In an embodiment, an exhaust valve seating face 44 may be provided having a length L44 and disposed at an exhaust valve seating face angle theta (θ), as noted in
As mentioned above, in
Alternately, as illustrated in
A series of performance tests were conducted on a test bench, using air flow measurements (cubic feet per minute—“cfm”) on a static test piece which had been modified. Table 1.1 shows a set of baseline measurements conducted on a standard, stock Lycoming engine head. Then, inlet passageway 70 of the Lycoming head was modified, and performance at various flow conditions was measured. As noted in Table 1.2, modification of the inlet passageway 70 alone as described herein may be anticipated to provide an average gain of 3.36 horsepower, and a peak gain of 5.74 horsepower, for a typical Lycoming nominal 180 horsepower engine (of nominal 360 cubic inch displacement). For the same engine, when intake valve 32 (or 132) improvements are additionally provided, an average gain of 5.32 horsepower may be expected, and a peak gain of 8.19 horsepower is anticipated. Addition of improved intake valve seats and exhaust valve seats may further improve performance.
Similarly, air flow bench testing was conducted on a test head portion having a modified exhaust passageway 74. As noted in Table 2.1, a baseline set of measurements was conducted. Then, the Lycoming head portion 26 was evaluated after modification of the exhaust passageway 74, and performance at various flow conditions was evaluated. With just modifications to the exhaust passageway 74, an average horsepower gain of four percent (4%) is expected, and a peak horsepower gain of six percent (6%). For the same head portion with additional modifications to the exhaust valve 34, average HP gain of ten percent (10%) is expected, and a peak gain of fourteen percent (14%).
1Bench test reference of 190.55 cfm at 10 inches of water pressure at the upstream inlet to the inlet passageway. Same for each of Table 1.1, Table 1.2, and Table 1.3.
2Same baseline reference for each of Table 2.1, Table 2.2, and Table 2.3.
In addition to the use of head portion 26, or cylinder and head assembly 30, as explained above, in a new aircraft engine, the various components described herein may be utilized in retrofit or the rebuilding of existing aircraft engines, in order to increase performance thereof. Candidate engines for such a retrofit may be found in aircraft designed for use with an existing air cooled spark ignited piston engine with an original rated maximum horsepower, and where the engine have a plurality of individual cylinders each having cylinder head portions, and where the existing piston engine is mechanically designed for operation by intake of combustion air through original inlet air passageways in the cylinder head portions, providing an air fuel mixture to the individual cylinders, and combusting the fuel to produce hot exhaust gases that exit through original exhaust passageways in the cylinder head portions. An improvement in performance may be obtained by substituting, the existing cylinder head portions with replacement cylinder head portions 26, wherein the replacement cylinder head portions 26 each providing an enhanced inlet air passageway 70 having reduced pressure drop during passage of combustion air therethrough as compared to pressure drop during passage of said combustion air through original air inlet passageways. Consequently, the use of the replacement cylinder head portions 26 provide an enhanced rated horsepower in excess of the original rated maximum horsepower for such an engine.
In addition to providing an enhanced inlet passageway 70 in such replacement head portion 26 (or 126), an enhanced exhaust passageway 74 may be provided, having reduced pressure drop during passage of exhaust gases therethrough as compared to passage of hot exhaust gases through an original exhaust passageway. The use of such a replacement cylinder head portion 26, or a cylinder and head assembly 30, as appropriate given a particular engine design or retrofit requirement, provides an enhanced rated horsepower in excess of the original rated maximum horsepower.
Yet further, improved inlet valve seats 150 (see
In an embodiment, the intake valve seat inserts 150 have intake valve seat sidewalls 154, which are configured for passage there through of intake air. In an embodiment, the intake valve seat sidewalls 154 may be provided in cross-sectional shape as seen in
For general description purposes, each facet may have an “in-plane” width described as its facet width Fw. In an embodiment the facet I2 associated with the angle β2 may have a facet width Fw of about zero point one two inches (0.120″).
In an embodiment, as seen in
In an embodiment, the intake valve seat sidewalls 154 may be configured, in cross-sectional shape, as a curve-fitted shaped surface corresponding approximately to the facets I1, I2, I3, I4, I5, I6, or I7, respectively defined by one or more of the angles β1, β2, β3, β4, β5, β6, or β7, all as noted above, at the respective cross-section locations as set forth in
Similarly, the exhaust valve seat 152 may comprise an insert having exhaust valve seat sidewalls 156. In an embodiment, the exhaust valve seat inserts 152 have exhaust valve seat sidewalls 156, which are configured for passage there through of exhaust gases. In an embodiment, the exhaust valve seat sidewalls 156 may be provided in cross-sectional shape as seen in
For general description purposes, each facet (E1, E2, E3, E4, E5, E6, E7, etc.) of an exhaust valve seat insert may have an “in -plane” width described as its facet width Fw. In an embodiment the facet E3 associated with the angle Σ3 may have a facet width Fw of about zero point one five inches (0.150″).
In an embodiment, as seen in
In an embodiment, the exhaust valve seat sidewalls 156 may be configured, in cross-sectional shape, as a curve-fitted shaped surface corresponding approximately to the facets E1, E2, E3, E4, E5, E6, or E7, respectively defined by one or more of the angles Σ1, Σ2, Σ3, Σ4, Σ5, Σ6, or Σ7, all as noted above, at the respective cross-section locations as set forth in
As briefly noted above, the intake valve seat inserts 150 and the exhaust valve seat inserts 152 may be each provided in a parallel valve configuration engine. OR, the intake valve seat inserts 150 and exhaust valve seat inserts 152, as just described above, may be provided for use in an angled valve configuration engine.
It is to be appreciated that the various aspects, features, structures, and embodiments of a cylinder head, intake valve seats, and exhaust valve seats for internal combustion, spark ignition aircraft engines as described herein is a significant improvement in the state of the art. The components described are simple, reliable, and easy to use in lieu of existing cylinder head designs and components, whether on new engines, or as may be retrofitted on existing engines. Although only a few exemplary aspects and embodiments have been described in detail, various details are sufficiently set forth in the drawing figures and in the specification provided herein to enable one of ordinary skill in the art to make and use the invention(s), which need not be further described by additional writing.
Importantly, the aspects, features, structures, and embodiments described and claimed herein may be modified from those shown without materially departing from the novel teachings and advantages provided, and may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Therefore, the various aspects and embodiments presented herein are to be considered in all respects as illustrative and not restrictive. As such, this disclosure is intended to cover the structures described herein and not only structural equivalents thereof, but also equivalent structures. Numerous modifications and variations are possible in light of the above teachings. The scope of the invention, as described herein is thus intended to include variations from the various aspects and embodiments provided which are nevertheless described by the broad meaning and range properly afforded to the language herein, as explained by and in light of the terms included herein, or the legal equivalents thereof.
This application is a Continuation-In-Part of pending U.S. patent application Ser. No. 13/756,891, filed on Feb. 1, 2013, which application claimed priority from prior U.S. Provisional Patent Application Ser. No. 61/595,049, filed Feb. 4, 2012, entitled CYLINDER HEADS FOR AIRCRAFT ENGINES, the disclosures of each are incorporated herein in their entirety, including their specification, drawing, and claims, by this reference.
| Number | Date | Country | |
|---|---|---|---|
| 61595049 | Feb 2012 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13756891 | Feb 2013 | US |
| Child | 13955365 | US |
