An automatic evaluation method for the available power of a turboshaft engine

Abstract

The present invention belongs to the technical field of turboshaft jet engines, and particularly relates to a method for automatically evaluating the available power of a turboshaft engine. The method comprises the following steps: Step 1: Filter the steady-state data of the engine operation characteristics data; Step 2: Detect the engine performance trend; Step 3: Calculate the torque coefficient. The beneficial effects of the present invention are as follows: The data collected in this method are all from the normal mission data collected by the current engine, and no additional maintenance procedures are required. The steady-state operation characteristic parameters of the engine are extracted through the steady-state data filter, which is convenient for online real-time processing of the data, and the performance curve of the engine to be inspected is established by using these processed parameters. The performance curve is used to estimate the limit power condition of the engine, and the torque coefficient of the available power is calculated for real-time display, so as to guide the pilot to decide the mission plan, scheduling, and the maintenance and overhaul of the engine. Compared with the existing manual evaluation method, it saves time and effort.

Description

Technical Field

[0001] The present invention belongs to the technical field of turboshaft jet engines, and particularly relates to a method for automatically evaluating the available power of a turboshaft engine. Background Art

[0002] As one of the parameters for helicopter flight safety, the indication of the available power of the engine is very important. The available power of a helicopter turboshaft engine varies throughout its life cycle. Wear of turbine blades, seals, contamination, etc. are the main factors causing this change. Helicopter operators rely to a certain extent on the indication of available power to determine mission plans, scheduling, and to perform maintenance and overhaul on the engine.

[0003] Existing methods for evaluating available power require maintenance pilots to perform manually: When performing a maximum available power check, the helicopter needs to be equipped with 2 engines, one well-operating turboshaft engine and the other being the turboshaft engine to be inspected. The maintenance pilot needs to keep the aircraft at a fixed altitude, airspeed, and power setting, while keeping the engine running stably, and then gradually reduce the power of the well-operating engine and increase the power of the engine to be inspected until the engine reaches its operating control limit. At this time, the pilot records the necessary aircraft and engine operating parameters, manually calculates the torque coefficient, and then indicates the available power. The existing method has cumbersome steps and relatively large workload. At the same time, the engine to be inspected will operate at its limit state, which poses a greater challenge to the safety of the engine and the maintenance pilot.

[0004] Therefore, there is an urgent need for an automated method to replace the current manual method for checking the maximum available power, which can simplify the process and enable real-time online evaluation of the available power of the engine. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for automatically evaluating the available power of a turboshaft engine, which can automatically evaluate the available power by using ordinary mission data of the helicopter, reduce the evaluation cost of the available power of the turboshaft engine, and achieve real-time evaluation of the available power.

[0006] The technical solution of the present invention is as follows: A method for automatically evaluating the available power of a turboshaft engine includes the following steps:

[0007] Step 1: Filter the steady-state data of the engine operating characteristic data;

[0008] Step 2: Detect the engine performance trend;

[0009] Step 3: Calculate the torque coefficient.

[0010] In step 1, the steady-state data filtering only uses parameters directly related to engine performance, including gas generator speed, turbine speed, torque, turbine temperature, atmospheric pressure and temperature, and airspeed, etc.

[0011] In step 1, the steady-state data filtering determines the steady-state operating point by calculating the standard deviation σ of the input parameters. First, ensure that the anti-ice bleed valve is closed.

[0012] Furthermore, ensure that the corrected gas generator speed Ng is higher than 90% to exclude the starting and idle slow-running points.

[0013] If the anti-ice bleed valve is closed and the corrected gas generator speed Ng is higher than 90%, then enter the data analysis window. The minimum data analysis window is 15 seconds. When the minimum data analysis window length is reached, start calculating the average value and standard deviation of each parameter included in the window. Compare the standard deviation with the specified threshold standard. If the steady-state standard is not met, the steady-state data filter advances the window and retains the data of the most recent 15 seconds. If the standard deviation of each parameter is less than its specified threshold, the data in the window is considered to be in a steady state.

[0014] After identifying the engine steady-state data points in step 2, compare them with the nominal engine performance and calculate the engine performance residual, expressed as the change in shaft power (ΔSHP). The specific calculation process is as follows:

[0015] The change in shaft power ΔSHP represents the difference between the corrected shaft power of the engine under test and the nominal engine operating under the same conditions at a determined steady-state operating point.

[0016] Among them, the nominal engine performance can be obtained by querying the database. By given four conditions: pressure altitude, airspeed, outside air temperature, and turbine gas temperature, the corresponding power of the nominal engine can be obtained.

[0017] After obtaining the shaft power performance residual, fit it with the turbine gas temperature.

[0018] The fitting algorithms include but are not limited to the analytical expression approximation method and the least squares method.

[0019] Update the residual fitting curve to the rated engine performance curve atlas to represent the corrected performance of the engine under test, that is, engine performance = nominal engine performance + residual curve fitting.

[0020] In step 2, when the engine is running, the turbine temperature curve is updated in real time. The new engine torque coefficient can be calculated through the following steps:

[0021] Determine the limit power value through the turbine temperature limit. At this time, the power turbine speed is 100%, and convert the power value into torque;

[0022] Divide the limit torque value by the target torque value to calculate the standard torque ratio. The target torque value is based on the rated power generated after ensuring the normal operation of the engine; use the specified linear relationship of this type of engine to convert the standard torque ratio into a torque coefficient.

[0023] The beneficial effects of the present invention are as follows: The data collected in this method all come from the normal mission data collected by the current engine, and no additional maintenance procedures are required. Extract the engine steady-state operation characteristic parameters through the steady-state data filter, which is convenient for online real-time processing of data, and use these processed parameters to establish the performance curve of the engine to be inspected. The performance curve is used to estimate the limit power condition of the engine, calculate the torque coefficient of the available power for real-time display, so as to guide the pilot to decide the mission plan, scheduling, and the maintenance and overhaul of the engine. Compared with the existing manual evaluation method, it saves time and effort. Brief Description of the Drawings

[0024] Figure 1 It is a schematic flow chart of an automatic evaluation method for the available power of a turboshaft engine provided by the present invention;

[0025] Figure 2 It is the operating point detected by the helicopter engine health monitoring system;

[0026] Figure 3 It is the steady-state operating point after steady-state data filtering;

[0027] Figure 4 It is the comparison between the power of the engine to be inspected and the power of the nominal engine;

[0028] Figure 5 It is the comparison of the torque coefficient between the automatic evaluation method and the manual calculation. Detailed Embodiment

[0029] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0030] An automatic available power evaluation method for a turboshaft engine provided by the present invention has a basic difference from the manual evaluation method in that the automatic available power evaluation method can extrapolate the engine power under the limit temperature condition based on the data obtained from the normal mission profile and perform real-time online indication. The automatic available power evaluation method for a turboshaft engine includes the following three aspects: (1) a steady-state data filter; (2) engine performance trend monitoring; (3) an automatic torque coefficient calculation logic. The data is collected from the health management system of a helicopter turboshaft engine. Through the steady-state data filter, the stable operating points of the engine are extracted and provided to the engine performance trend monitoring algorithm to update the engine power-gas turbine temperature performance curve. The torque coefficient is estimated by passing through the rated limit power condition (the gas turbine temperature limit point) and using the same procedure as the manual method.

[0031] As Figure 1 shown, an automatic available power evaluation method for a turboshaft engine includes the following steps:

[0032] Step 1: Perform steady-state data filtering on the engine operation characteristic data

[0033] The steady-state data filtering only uses the parameters directly related to the engine performance, including gas generator speed, turbine speed, torque, turbine temperature, atmospheric pressure temperature, airspeed, etc. Table 1 lists the parameters and the constraint conditions applied by the steady-state data filter.

[0034] Table 1 Parameters and Constraint Conditions

[0035]

[0036] The steady-state data filter determines the steady-state operating point by calculating the standard deviation σ of the input parameters. First, ensure that the anti-ice bleed valve is closed. Further, ensure that the corrected gas generator speed Ng is higher than 90% to exclude the starting and idle slow running points.

[0037] If the anti-ice bleed valve is closed and the corrected gas generator speed Ng is higher than 90% or more, enter the data analysis window. The minimum data analysis window is 15 seconds. When the minimum data analysis window length is reached, start calculating the average value and standard deviation of each parameter included in the window. Compare the standard deviation with the specified threshold standard shown in Table 1. If the steady-state standard is not met, the steady-state data filter advances the window and retains the data of the most recent 15 seconds. If the standard deviation of each parameter is less than its specified threshold, the data in the window is considered to be in a steady state.

[0038] Step 2: Engine performance trend detection

[0039] After the steady-state data points of the engine are recognized, they are compared with the nominal engine performance, and the engine performance residual is calculated, expressed as the change in shaft power (ΔSHP). The specific calculation process is as follows:

[0040] The change in shaft power (ΔSHP) represents the difference between the corrected shaft power of the engine under test and the nominal engine operating under the same conditions at a determined steady-state operating point;

[0041] In the architecture of the available power automatic evaluation method for turboshaft engines, the nominal engine performance can be obtained by querying the database. By specifying four conditions: barometric altitude, airspeed, outside air temperature, and turbine gas temperature, the corresponding power of the nominal engine can be automatically queried by this program.

[0042] After obtaining the shaft power performance residual, it is fitted with the gas turbine temperature;

[0043] The fitting algorithms include, but are not limited to, the analytical expression approximation method and the least squares method;

[0044] The residual fitting curve is updated to the rated engine performance curve atlas to represent the corrected performance of the engine under test, that is, engine performance = nominal engine performance + residual curve fitting.

[0045] Step 3: Calculation of the torque coefficient

[0046] When the engine is running, the turbine temperature curve is updated in real time. The new engine torque coefficient can be calculated through the following steps:

[0047] The limit power value is determined through the turbine temperature limit. At this time, the power turbine speed is 100%, and the power value can be converted into torque;

[0048] The limit torque value is divided by the target torque value to calculate the standard torque ratio. The target torque value is based on the rated power generated after ensuring the normal operation of the engine;

[0049] The standard torque ratio is converted into a torque coefficient using the specified linear relationship for this type of engine.

[0050] According to a specific implementation manner of an embodiment of the present invention, the steady-state data filter first screens the input data to ensure that the anti-icing bleed valve is closed; further screening ensures that the corrected gas generator speed Ng is higher than 90% to exclude the starting and idle slow running points; if the above conditions are met, it enters the data analysis window, and the minimum data analysis window is 15 seconds. When the minimum data analysis window length is reached, the average value and standard deviation of each parameter included in the window are calculated; the standard deviation is compared with the specified threshold standard shown in Table 1. If the steady-state standard is not met, the steady-state data filter advances the window forward, takes the data of the most recent 15 seconds, and then reapplies the algorithm for calculation; if the standard deviation of each parameter is less than its specified threshold, the data in the window is considered to be at a stable operating point; the algorithm continues to add the data of the next moment to the analysis window, repeats the steady-state data filtering, and if the defined steady-state conditions are met, the analysis window is expanded; if not, the average value of the previous analysis window is extracted as one of the steady-state operating points. The steady-state filter continues to analyze the next segment of data.

[0051] According to a specific implementation manner of an embodiment of the present disclosure, the engine power correction process is as follows: the engine operating range is divided into intervals with evenly spaced gas turbine temperatures; each time a new steady-state point is obtained by the steady-state data filter, the ΔSHP value is calculated according to the nominal engine performance of the four inputs by querying the database; the ΔSHP value is divided into the appropriate gas turbine temperature interval, and the average gas turbine temperature and the average ΔSHP value in the corresponding interval are updated. The algorithm is shown in the following formula:

[0052]

[0053]

[0054] In the formula, is the average value of the gas turbine temperature at the k-th step in the i-th interval, and α i,k is the forgetting factor at the k-th step in the i-th interval, and T4.5 i,k is the gas turbine temperature value input at the k-th step in the i-th interval. The definition of the relevant subscript of ΔSHP is the same as it.

[0055] According to a specific implementation manner of this embodiment, when the engine is running, its performance curve is updated in real time. The new engine torque characteristic (torque coefficient) can be calculated through the following steps: (1) Determine the limit power value through the gas turbine temperature limit. At this time, the power turbine speed is 100%, and the power value can be converted into torque; (2) Divide the limit torque value by the rated torque value to calculate the standard torque ratio. The rated torque value is converted based on the rated power generated after ensuring the normal operation of the engine; (3) Convert the standard torque ratio into a torque coefficient.

[0056] To verify the available power automatic evaluation method for the turboshaft engine, its specific implementation results applied to a certain type of helicopter engine will be described. The steady-state data extraction from a certain flight data is as follows Figure 2 shown. Since the helicopter is in a flight mission rather than at a fixed operating point, there are significant fluctuations in the monitoring data of the engine. After being processed by a self-written steady-state data filter, the results are as follows Figure 3 shown. The extracted steady-state operating points are relatively close to the engine steady-state operation line, proving the application effect of the steady-state data filter. After extracting the steady-state data, engine power correction is performed. The comparison between the power of the engine to be inspected and the nominal engine power is as follows Figure 4 shown, indicating that the performance of the engine after serving for a certain period has declined, and this algorithm can accurately predict this result.

[0057] To further verify the accuracy of the finally calculated torque coefficient, the available power automatic evaluation method for the turboshaft engine is applied to the data of multiple engines, and manual calculations are carried out simultaneously. The comparison results of the two methods are as follows Figure 5 shown. The average error between the results of the automatic evaluation and the manual calculation is 5.1%.

[0058] In summary, this method can automatically evaluate the available power using the general mission data of the helicopter, reduce the evaluation cost of the available power of the turboshaft engine, and achieve real-time evaluation of the available power.

Claims

1. An automatic evaluation method for available power of a turboshaft engine, characterized in that It includes the following steps: Step 1: Perform steady-state data filtering on the engine operation characteristic data; In the steady-state data filtering of Step 1, only the parameters directly related to the engine performance are used, including the gas generator speed, turbine speed, torque, turbine temperature, atmospheric pressure temperature, and airspeed; In Step 1, the steady-state operating point is determined by calculating the standard deviation σ of the input parameters. First, ensure that the anti-ice bleed valve is closed; Ensure that the corrected gas generator speed Ng is higher than 90% to exclude the starting and idle slow-running points; If the anti-ice bleed valve is closed and the corrected gas generator speed Ng is higher than 90%, enter the data analysis window. The minimum data analysis window is 15 seconds; when the minimum data analysis window length is reached, start calculating the average value and standard deviation of each parameter included in the window; compare the standard deviation with the specified threshold standard. If the steady-state standard is not met, the steady-state data filter advances the window forward, keeping the data of the most recent 15 seconds. If the standard deviation of each parameter is less than its specified threshold, the data in the window is considered to be in a steady state; Step 2: Detect the engine performance trend; Step 3: Calculate the torque coefficient.

2. The automatic evaluation method for available power of a turboshaft engine according to claim 1, characterized in that, After identifying the engine steady-state data points in Step 2, compare them with the nominal engine performance and calculate the engine performance residual, expressed as the shaft power change ΔSHP. The specific calculation process is as follows: The shaft power change ΔSHP represents the difference between the corrected shaft power of the engine under test and the nominal engine operating under the same conditions at a determined steady-state operating point; Among them, the nominal engine performance can be obtained by querying the database. By giving four conditions: barometric altitude, airspeed, outside air temperature, and turbine gas temperature, the corresponding power of the nominal engine can be obtained; After obtaining the shaft power performance residual, fit it with the turbine gas temperature; The fitting algorithms include but are not limited to the analytical expression approximation method and the least squares method; Update the residual fitting curve to the rated engine performance curve atlas to represent the performance of the engine under test after correction, that is, engine performance = nominal engine performance + residual curve fitting.

3. The automatic evaluation method for available power of a turboshaft engine according to claim 1, characterized in that In Step 2, when the engine is running, the turbine temperature curve is updated in real time. The new engine torque coefficient can be calculated through the following steps: Determine the limit power value through the turbine temperature limit. At this time, the power turbine speed is 100%, and convert the power value to torque; Divide the limit torque value by the target torque value to calculate the standard torque ratio. The target torque value is based on the rated power generated after ensuring the normal operation of the engine; convert the standard torque ratio to the torque coefficient using the specified linear relationship of the engine.

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