Conventional aircraft engines, such as piston aircraft engines, typically require adjustment to the ratio of air to fuel, termed the air-fuel mixture, provided to the engines during operation. For example, during takeoff, a piston aircraft engine typically utilizes a rich air-fuel mixture where the air-fuel mixture is stoichiometric. For better fuel economy after takeoff when the aircraft reaches lower-power cruising conditions, the aircraft engine can utilize a leaner air-fuel mixture where the amount of air added to the air-fuel mixture is increased such that the air-fuel mixture is greater than stoichiometric.
In conventional piston aircraft engines, once the aircraft reaches a cruising speed, a pilot manually controls leaning of the air-fuel mixture in an attempt to optimize fuel economy. During operation the pilot visually monitors an exhaust gas temperature (EGT) gauge, maintains the aircraft's throttle in a fixed state, and adjusts a fuel control lever to control the amount of fuel delivered to the engine. Based upon an output from the EGT gauge, the pilot adjusts the fuel control lever to set the air-fuel mixture to a certain amount to allow the engine to operate at an efficient fuel economy. For example, as the pilot reduces the amount of fuel delivered to the engine, the pilot can observe an increase in the EGT as provided by the EGT gauge up to a certain range of EGT values. As the pilot further decreases the amount of fuel delivered to the engine, the pilot will typically observe a decrease in the EGT provided by the EGT gauge. Such a decrease in the EGT value indicates to the pilot that he has reduced the amount of fuel delivered to the engine past an amount that allows the engine to operate at an efficient fuel economy. Therefore, in order to maximize the efficiency of the aircraft engine, the pilot increases the amount of fuel delivered to the engine until the EGT gauge indicates an increase in the EGT up to the previously detected range of EGT values.
Conventional methods for adjusting the air-fuel mixture provided to an aircraft engine suffer from a variety of deficiencies. As described above for aircraft having conventional piston aircraft engines, the aircraft pilot visually observes changes in the engine's EGT and manually adjusts the air-fuel mixture accordingly. However, because the procedure is operator driven, the operator may not be able to provide the aircraft engine with an optimal air-fuel ratio, corresponding with a peak EGT, in order to provide optimal fuel economy to the engine. For example, as the pilot reduces the amount of fuel delivered to the engine, the pilot can observe an increase in the EGT as provided by the EGT gauge up to a certain range of EGT values. Because the pilot's attention must be divided among several tasks, the detection of peak EGT can be inaccurate. For certain engines, it is not even possible to achieve peak EGT because running those engines at or near peak EGT can cause either detonation in the engine's cylinder assemblies or excessive turbocharger turbine inlet temperatures, the occurrence of which can damage or destroy engine components. Additionally, during operation of the conventional piston aircraft engines, the aircraft pilot must adjust the air-fuel mixture for all cylinders simultaneously. Accordingly, because the pilot cannot adjust the air-fuel mixture provided to the engine on a cylinder-by-cylinder basis, the pilot cannot accurately optimize the fuel efficiency of the engine.
Embodiments of the present invention overcome these deficiencies and provide an apparatus and method for providing fuel to an aircraft engine to account for an increase in or a reduction of a fuel injector's flow rate over time. In one arrangement, an aircraft engine includes an aircraft engine controller configured to detect an actual peak exhaust gas temperature of a cylinder assembly independently of the other cylinder assemblies. For each cylinder assembly, the aircraft engine controller detects an intersection between a first function representing a relationship between a set of rich exhaust gas temperature signals and a corresponding set of rich fuel-air ratio values and a second function representing a relationship between a set of lean exhaust gas temperature signals and a set of lean fuel-air ratio values. Based upon the intersection between the first and second functions, the engine controller detects the actual peak EGT and the corresponding fuel-air ratio value for the cylinder assembly and, accordingly, can determine if a correction in the fuel-air ratio provided to the cylinder assembly is required. With such a configuration, the engine controller provides each cylinder assembly of the aircraft engine with an accurate fuel-air mixture to allow for operation of the engine with optimal fuel economy. Because the engine controller determines the actual peak exhaust gas temperature for the cylinder assembly, the engine controller can skip over the fuel-air mixtures which tend to result in the occurrence of detonation events or excessive turbine inlet temperatures.
In one arrangement, a method for adjusting a fuel-air ratio of the mixture provided to an engine cylinder of an engine includes detecting a set of rich exhaust gas temperature signals corresponding to a set of rich fuel-air ratio values, each of the set of rich fuel-air ratio values having a fuel-air ratio value that is greater than a threshold or theoretical peak EGT fuel-air ratio value. The method includes detecting a set of lean exhaust gas temperature signals corresponding to a set of lean fuel-air ratio values, each of the set of lean fuel-air ratio values having a fuel-air ratio value that is less than the theoretical peak EGT fuel-air ratio value. The method includes detecting an intersection between the set of lean exhaust gas temperature signals and the set of rich exhaust gas temperature signals, the intersection associated with the actual peak EGT fuel-air ratio value. The method includes comparing the actual peak EGT fuel-air ratio value with the theoretical peak EGT fuel-air ratio value and adjusting the fuel-air ratio of the mixture provided to the cylinder assembly so that the theoretical EGT fuel-air ratio value and actual peak EGT fuel-air ratio value are substantially the same.
In one arrangement, an aircraft engine control system includes an exhaust gas temperature sensor, the exhaust gas temperature sensor configured to generate gas temperature signals associated with an aircraft engine cylinder of an aircraft engine and an engine controller disposed in electrical communication with the exhaust gas temperature sensor, the engine controller being operable to adjust a fuel-air ratio for a fuel-air mixture provided to the aircraft engine cylinder of an aircraft engine. The engine controller is configured to detect a set of rich exhaust gas temperature signals corresponding to a set of rich fuel-air ratio values, each of the set of rich fuel-air ratio values having a fuel-air ratio value that is greater than a theoretical peak EGT fuel-air ratio value. The engine controller is configured to detect a set of lean exhaust gas temperature signals corresponding to a set of lean fuel-air ratio values, each of the set of lean fuel-air ratio values having a fuel-air ratio value that is less than the theoretical peak EGT fuel-air ratio value. The engine controller is configured to detect an intersection between the set of lean exhaust gas temperature signals and the set of rich exhaust gas temperature signals, the intersection associated with an actual peak EGT fuel-air ratio value. The engine controller is configured to compare the actual peak EGT fuel-air ratio value with the theoretical peak EGT fuel-air ratio value and adjust the fuel-air ratio of the mixture provided to the cylinder assembly so that the theoretical EGT fuel-air ratio value and actual peak EGT fuel-air ratio value are substantially the same.
The foregoing and other objects, features and advantages will be apparent from the following description of particular embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of various embodiments of the invention.
Embodiments of the present invention provide an apparatus and method for providing fuel to an aircraft engine to account for an increase in or a reduction of a fuel injector's flow rate over time. In one arrangement, an aircraft engine includes an aircraft engine controller configured to detect an actual peak exhaust gas temperature of a cylinder assembly independently of the other cylinder assemblies. For each cylinder assembly, the aircraft engine controller detects an intersection between a first function representing a relationship between a set of rich exhaust gas temperature signals and a corresponding set of rich fuel-air ratio values and a second function representing a relationship between a set of lean exhaust gas temperature signals and a set of lean fuel-air ratio values. Based upon the intersection between the first and second functions, the engine controller detects the actual peak EGT and the corresponding fuel-air ratio value for the cylinder assembly and, accordingly, can determine if a correction in the fuel-air ratio provided to the cylinder assembly is required. With such a configuration, the engine controller provides each cylinder assembly of the aircraft engine with an accurate fuel-air mixture to allow for operation of the engine with optimal fuel economy. Because the engine controller determines the actual peak exhaust gas temperature for the cylinder assembly, the engine controller can skip over the fuel-air mixtures which tend to result in the occurrence of detonation events or excessive turbine inlet temperatures.
The fuel delivery system 18 is configured to provide fuel from a fuel source to each of the cylinder assemblies 16. The fuel delivery system 18 includes a fuel pump, fuel rails 26-1, 26-2, and fuel delivery devices 28, as shown in
The engine control system, such as an aircraft engine control system 12, is configured to control the performance of the aircraft engine 10 during operation. The aircraft engine control system 12 includes an engine controller 30 and a set of sensors (not shown) disposed in electrical communication with the engine controller 30. The set of sensors measure various engine and environmental conditions, engine fluid pressures, exhaust gas temperature, air temperature, and air density and provide signals corresponding to the measured conditions to the engine controller 30. In one arrangement, the set of sensors includes an exhaust gas temperature (EGT) sensor 31, as shown in
In one arrangement, the engine controller 30 is configured to optimize the fuel efficiency of the aircraft engine 10 as it operates. For example, as will be described below, the engine controller 30 is configured to detect an actual peak exhaust gas temperature for each cylinder assembly 16 of the aircraft engine 10. Based upon such detection, the engine controller 30 detects if a correction in the fuel-air ratio for a fuel-air mixture provided to each cylinder assembly 16 is required.
With reference to
With reference to
Once the fuel-air mixture provided to the cylinder assembly 16-1 is sufficiently enriched, the engine controller 30 detects the set of rich exhaust gas temperature signals 52 corresponding to the set of rich fuel-air ratio values. For example, with reference to
Returning to
Once the fuel-air mixture provided to the cylinder assembly 16-1 is sufficiently leaned, the engine controller 30 detects the set of lean exhaust gas temperature signals 54 corresponding to the set of lean fuel-air ratio values. For example, with reference to
Returning to
Returning to
As indicated above, the engine controller 30 is configured to detect an actual peak fuel-air ratio value 56 for the cylinder assembly 16-1 and determine if a correction in the fuel-air ratio of the fuel-air mixture provided to the cylinder assembly 16-1 is required. With such a configuration, the engine controller 30 can provide each cylinder assembly 16 of the aircraft engine 10 with an accurate fuel-air mixture to optimize fuel economy for each cylinder assembly 16. Additionally, because the engine controller determines the actual peak exhaust gas temperature for each cylinder assembly 16, the engine controller 30 limits the provision of a too lean fuel-air mixture to each cylinder assembly 16 thereby minimizing the occurrence of detonation events.
In certain cases, during operation the EGT sensor 31 for a cylinder assembly 16 can generate one or more rich or lean exhaust gas temperature signals 52, 54 having temperature values that are out-of-range from expected temperature values. For example, a detonation event can occur within the cylinder assembly 16-1 as an EGT sensor 31 generates an exhaust gas temperature signal. Such detonation can cause the EGT sensor 31 to generate an exhaust gas temperature signal indicative of a lower than normal temperature value. These lower than normal temperature value affect the accuracy of the linear regression relationship for the set of rich exhaust gas temperature signals and the set of rich fuel-air ratio values or the linear regression relationship, for the set of lean exhaust gas temperature signals and the set of lean fuel-air ratio values. Accordingly, in one arrangement, the engine controller 30 is configured to detect the accuracy of the linear regression relationships prior to detecting the actual peak fuel-air ratio value 56 for a cylinder assembly 16.
For example, in one arrangement, the engine controller 30 is configured to detect the accuracy of the linear regression relationship based upon a linear regression value for a linear regression of either the set of rich exhaust gas temperature signals and the set of rich fuel-air ratio values or the set of lean exhaust gas temperature signals and the set of lean fuel-air ratio values. With reference to
In another example, the engine controller 30 is configured to detect the accuracy of the linear regression relationship based upon a slope of the linear regression for either the set of rich exhaust gas temperature signals and the set of rich fuel-air ratio values or the set of lean exhaust gas temperature signals and the set of lean fuel-air ratio values. With reference to
In one arrangement, the aircraft engine's 10 operating speed, as measured in RPM's, can affect an amount of the fuel-air mixture required to be provided to a cylinder assembly 16 to allow for optimal fuel-efficient operation of the aircraft engine 10. For example, the higher the RPM's of the engine, the larger the volume of the fuel-air mixture that is required to be delivered to a cylinder assembly 16 in order to provide optimal engine efficiency. Accordingly, when operating the fuel delivery devices 28, such as fuel injectors, associated with each cylinder assembly 16, the engine controller 30 is configured to adjust the amount or volume of the fuel-air mixture delivered to the cylinder assembly 16 to take into account different engine operating speeds of the engine 10.
Initially, the engine controller 30 determines a scaling factor, s, configured to normalize the actual peak fuel-air ratio value 56 to remove the dependency of the actual peak fuel-air ratio value 56 on engine speed. For example, the engine controller 30 utilizes the following relationship:
s=(((peak fuel-air ratio value/theoretical fuel-air ratio value)−1)/k)+1
to determine the scaling factor s where k in the relationship represents a scaling factor based upon a current operating condition of the engine 10. In one arrangement, the engine controller 30 is configured with a table that includes various values for k for various operating conditions (i.e., taking into consideration engine speed and load) of the engine 10.
Once the engine controller 30 determines a value for s, the engine controller 30 uses the s value to determine a current fuel multiplier value, m, to be used in adjusting the amount or volume of the fuel-air mixture delivered to a cylinder assembly 16. In one arrangement, the engine controller 30 utilizes s value in the following relationship: m=(k*(s−1))+1 to determine a current fuel multiplier value, m. The engine controller 30 then utilizes the current fuel multiplier value, m to adjust the duration of operation of a fuel delivery device 28 associated with a cylinder assembly 16. In one arrangement, the engine controller 30 is configured to control the duration of operation of the fuel delivery device 28 to provide a given volume of the fuel-air mixture to a cylinder assembly 16. For example, assume the engine controller 30 is configured to allow the fuel delivery device 28 to operate for a period of two seconds to deliver the fuel-air mixture to the cylinder assembly 16. Prior to activating the fuel delivery device 28, the engine controller multiplies the preconfigured duration value by the calculated m value. Based upon the value of m, this process results in either an increase or a decrease in the duration of operation of the fuel delivery device 28 to either increase or decrease the volume of the fuel-air mixture provided by the fuel delivery device 28 to the cylinder assembly 16.
While various embodiments of the invention have been particularly shown and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
For example, as indicated above, when performing the linear regression among the four rich data elements 60, 62, 64, and 66 or among the four lean data elements 70, 72, 74, and 76, the engine controller 30 calculates a linear regression (e.g. R2) value 90, indicative of the accuracy of the linear regression for the cylinder assembly 16-1. Such description is by way of example only. In one arrangement, the engine controller performs the linear regression among the first three rich data elements 60, 62, and 64 and among the three lean data elements 70, 72, and 74. The engine controller 30 calculates a rich linear regression (e.g. R2) value 90 based upon the rich data elements 60, 62, and 64 and calculates a lean linear regression value 90 based upon the three lean data elements 70, 72, and 74. Taking the rich data elements 60, 62, and 64 as an example, the engine controller 30 then compares the resulting rich linear regression value 90 to the threshold fit value 92.
In the case where the engine controller 30 detects that the linear regression value 90 is greater than or equal to the threshold fit value 92 (e.g., a threshold fit value of 0.90), the engine controller 30 detects that the linear regression relationship is accurate. Accordingly, in such a case, the engine controller 30 can continue with steps 108 and 110 described above for the cylinder assembly 16-1. In the case where the engine controller 30 detects that the linear regression value 90 is less than the threshold fit value 92, the engine controller 30 detects that the linear regression relationship is inaccurate. Accordingly, in such a case, the engine controller 30 will obtain the fourth rich data element 66 and recalculate the rich linear regression (e.g. R2) value 90 based upon the rich data elements 60, 62, 64, and 66.