Full time lean running aircraft piston engine

Abstract

A full time lean air fuel mixture running spark ignited air cooled aircraft piston engine. In one embodiment, a drop-in substitution is provided for an equivalent make, model, and engine size, wherein the new, rebuilt, or reconfigured engine provides as much or more horsepower when compared to the original engine, but runs at a lean air fuel ratio condition during normal operating modes, including takeoff, climb, and cruise, thus saving significantly on fuel. In yet another embodiment, a drop-in substitution having a somewhat larger cylinder displacement volume may be provided to attain equivalent or enhanced maximum horsepower while operating at lean air fuel ratios. Enhanced engine life may be anticipated, since cylinder head temperatures (CHTs) may be reduced, compared to engines using rich air fuel ratios for climb and cruise conditions. Aircraft using such engines are also disclosed.

1 . An aircraft, said aircraft comprising:
 at least one air cooled spark ignition piston engine configured for full time lean run during normal operations, said normal operations comprising takeoff, climb, and cruise flight conditions,   said full time lean run engine having a stated engine total displacement volume and a selected maximum horsepower, and mechanically designed for said normal operations using a lean air fuel mixture ratio, said full time lean run engine comprising a plurality of cylinders, fuel injectors, and a compressor to increase the pressure of combustion air entering said cylinders to a second pressure level wherein said full time lean run engine will provide at least said selected maximum horsepower, and   wherein said lean air fuel mixture ratio comprises an equivalence ratio of less than 1.0.   
     
     
         2 . The aircraft as set forth in  claim 1 , wherein said takeoff operations comprise full power takeoff. 
     
     
         3 . The aircraft as set forth in  claim 1 , wherein said climb operations comprise high power climb. 
     
     
         4 . The aircraft as set forth in  claim 1 , wherein during said climb conditions, said engine operates in excess of 92% of said selected maximum horsepower. 
     
     
         5 . The aircraft as set forth in  claim 1 , wherein during said climb conditions, said engine operates at about 95% or more of said rated maximum horsepower. 
     
     
         6 . A spark ignited air cooled aircraft piston engine, comprising:
 a plurality of cylinders;   a plurality of fuel injectors, one of said plurality of fuel injectors for each of said cylinders;   a compressor for supply of compressed inlet air to charge said plurality of cylinders;   a fuel supply system to supply fuel to said cylinders, said fuel supply system comprising a fuel pump and a fuel mixture regulation device, said fuel supply system operable for selectively responding to a first output and to a second output from a fuel mixture regulation device, said fuel supply system configured to provide a first mixture level responsive to an first input, and to a second mixture level responsive to a second input;   said fuel supply system selectively placed into a first operating mode in response to said first input and selectively placed into a second operating mode in response to said second input,   said engine having a rated maximum horsepower and configured for   a normal operating mode wherein said first mixture level comprises a lean fuel air mixture, said normal operating mode comprising full power takeoff, full power or high power climb and cruise engine configurations, comprising climb or cruise at from in excess of about 92% to about 100% of said rated maximum horsepower, and   a standby operating mode wherein said second operating mode comprises a rich fuel air mixture for full power takeoff, or for full power or high power climb configuration, or for cruise engine configurations.   
     
     
         7 . An engine as set forth in  claim 6 , wherein said fuel injectors are tuned to provide precisely regulated fuel flow to each one of said plurality of cylinders, wherein each cylinder receives a lean fuel air mixture, and wherein air fuel mixtures are substantially matched as compared between cylinders. 
     
     
         8 . An engine as set forth in  claim 7 , wherein said compressed air is supplied to said plurality of cylinders at a substantially constant manifold absolute pressure during at least a portion of said normal operating mode of said engine. 
     
     
         9 . An engine as set forth in  claim 8 , wherein said substantially constant manifold pressure comprises an absolute pressure in the range from about 29 inches of mercury to about 41 inches of mercury. 
     
     
         10 . An engine as set forth in  claim 9 , wherein said substantially constant manifold pressure comprises an absolute pressure of from about 31 to about 33 inches of mercury. 
     
     
         11 . An engine as set forth in  claim 6 , or in  claim 9 , wherein said lean fuel air mixture is defined by an equivalence ratio in the range of from about 0.8 to about 0.9. 
     
     
         12 . An engine as set forth in  claim 11 , wherein said lean fuel air mixture is defined by an equivalence ratio in the range of from about 0.85 to about 0.9. 
     
     
         13 . An engine as set forth in  claim 11 , wherein said lean fuel air mixture is provided with an equivalence ratio of about 0.87. 
     
     
         14 . An engine as set forth in  claim 6 , further comprising an ignition circuit for use with a spark igniter for creating a spark for igniting fuel in said engine, said ignition circuit comprising one or more sensors responsive to an actual operating conditions to generate an output signal, said output signal providing spark timing in said engine to effect smooth combustion when said engine is operated with said lean air fuel mixture. 
     
     
         15 . An engine as set forth in  claim 6 , further comprising an ignition circuit for use with a spark igniter for creating a spark for igniting fuel in said engine, said ignition circuit comprising one or more sensors responsive to an abnormal ignition condition, and wherein in response to receipt of an abnormal ignition condition signal from said one or more sensors, said operation of said engine is converted from said normal operating mode to said standby operating mode. 
     
     
         16 . An engine as set forth in  claim 6 , wherein said engine further comprises an electronic ignition system, said electronic ignition system configured for providing selected spark timing commensurate with said lean fuel air mixture ratios at a selected engine manifold absolute pressure. 
     
     
         17 . An engine as set forth in  claim 16 , wherein spark timing is temporarily retardable from a normal set point value. 
     
     
         18 . An engine as set forth in  claim 17 , wherein retarding of said spark timing is controlled with respect to a selected cylinder head temperature limit. 
     
     
         19 . An engine as set forth in  claim 16 , wherein retarding of said spark timing is controlled to provide operating conditions including a margin of safety with respect to one or more selected adverse operating conditions. 
     
     
         20 . An engine as set forth in  claim 19 , wherein said one or more selected adverse operation conditions comprises detonation, and wherein timing may be retarded from about 2 to about 8 degrees from said normal set point value. 
     
     
         21 . The method as set forth in  claim 19 , wherein said one or more selected adverse operation conditions comprises pre-ignition, and wherein timing may be retarded from about 2 to about 8 degrees from said normal set point value. 
     
     
         22 . A method for improving the performance of spark ignition air cooled aircraft piston engines, comprising:
 modifying the operating parameters of an existing fuel system configuration to full time lean run conditions wherein an equivalence ratio of less than 1.0 is provided during normal operating modes, said normal operating modes comprising full power takeoff, full or high power climb, and cruise power settings;   increasing the total air mass flow through the engine sufficient to achieve selected full time lean run operating parameters, said operating parameters comprising brake horsepower output and cylinder head temperature.   
     
     
         23 . The method as set forth in  claim 22 , wherein increasing total air mass flow through the engine comprises adding a compressor to compress air entering said engine. 
     
     
         24 . The method as set forth in  claim 23 , wherein said compressor comprises an exhaust gas driven turbocharger. 
     
     
         25 . The method as set forth in  claim 23 , wherein increasing total air mass flow through the engine comprises increasing the displacement of said engine. 
     
     
         26 . The method as set forth in  claim 22 , or in  claim 23 , further comprising an electronic ignition system, said electronic ignition system configured to provide selected spark timing commensurate with said lean fuel air mixture ratios at selected engine manifold absolute pressures. 
     
     
         27 . The method as set forth in  claim 14 , wherein spark timing is adjustably retardable from its otherwise normal set point value. 
     
     
         28 . The method as set forth in  claim 27 , wherein retarding of said spark timing is controlled with respect to a selected cylinder head temperature limit. 
     
     
         29 . The method set forth in  claim 27 , wherein retarding of said spark timing is controlled to provide operating conditions including a margin of safety with respect to one or more selected adverse operating conditions. 
     
     
         30 . The method as set forth in  claim 29 , wherein said one or more selected adverse operation conditions comprises detonation, and wherein timing may be retarded from about 2 to about 8 degrees from said normal set point value. 
     
     
         31 . The method as set forth in  claim 29 , wherein said one or more selected adverse operation conditions comprises pre-ignition, and wherein timing may be retarded from about 2 to about 8 degrees from said normal set point value.