Piston aeroengine emission test system and method
By designing a piston-type aero-engine emission test system, we have achieved full envelope altitude environment simulation and emission testing, solved the problem that traditional loading modes cannot simulate the coupling characteristics of real flight loads, and provided a real emission testing method.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CATARC AUTOMOTIVE TEST CENT TIANJIN CO LTD
- Filing Date
- 2026-06-12
- Publication Date
- 2026-07-14
Smart Images
Figure CN122385194A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of aircraft engine emission testing technology, and in particular to an emission testing system and method for piston aircraft engines. Background Technology
[0002] Piston aircraft engines, as the primary power source for general aviation aircraft, are widely used in private planes, trainer aircraft, agricultural aviation, and low-altitude unmanned aerial vehicle platforms. With the rapid development of low-altitude aircraft, the impact of their low-altitude emissions on the atmospheric environment is receiving increasing attention. However, current domestic and international standards systems lack specific emission testing methods and specifications for piston aircraft engines.
[0003] The current emissions testing standards system includes two categories, neither of which is applicable to piston-type aircraft engines. The first is the emissions testing standards for automotive internal combustion engines. Existing automotive internal combustion engine emissions testing standards mostly use constant speed and constant torque loading modes or standardized operating cycles. However, in actual flight, piston-type aircraft engines mostly directly drive fixed-pitch or constant-speed propellers. The coupling relationship between their output speed and torque is constrained by the aerodynamic load characteristics of the propeller. Traditional loading modes cannot simulate the load coupling characteristics of real flight, resulting in a significant deviation between test conditions and actual flight conditions. Therefore, emissions data cannot reflect the engine's actual flight emissions levels. The second category is the emissions certification standards for aero-turbo engines. The International Civil Aviation Organization (ICAO) has established an emissions certification system for turbojet and turbofan engines in the Convention on International Civil Aviation and its subsidiary regulations, explicitly excluding piston-type aircraft engines. Furthermore, the ICAO certification system cannot assess the engine's emissions characteristics across its entire flight envelope.
[0004] In summary, there is an urgent need to establish a dedicated emission testing technology for piston-engine aircraft to address the aforementioned technical gaps, such as load distortion and lack of standards and specifications. Summary of the Invention
[0005] The purpose of this invention is to address the technical problems in existing emissions testing of aircraft piston engines, namely, the deviation between operating conditions and actual flight conditions, and the inability to simulate high-altitude emissions characteristics. This invention provides a piston-type aircraft engine emissions testing system and method. By setting up an altitude environment simulation system, a propeller load characteristic simulation system, and an emissions measurement system, full-envelope altitude environment simulation can be achieved, covering typical profile operating conditions for emissions testing. This solves the technical problems in existing aircraft piston engine emissions testing, namely, the deviation between operating conditions and actual flight conditions, and the inability to simulate high-altitude emissions characteristics.
[0006] This invention is achieved through the following technical solution:
[0007] One object of the present invention is to provide an emission testing system for a piston-type aircraft engine, comprising:
[0008] A test bench system is used to support the engine under test for testing.
[0009] The high-altitude environment simulation system includes an intake simulation unit and an exhaust pressure simulation unit. The intake simulation unit is used to connect to the intake port of the engine under test to provide the engine under test with intake air that matches the gas environment at different test flight altitudes. The exhaust pressure simulation unit is used to connect to the exhaust port of the engine under test to make the exhaust pressure of the engine under test consistent with the air pressure at the test flight altitude.
[0010] The propeller load simulation system includes a dynamometer and a load controller. The dynamometer is mechanically connected to the output shaft of the engine under test. The load controller is connected to the dynamometer and the altitude environment simulation system. It is used to read the atmospheric pressure and temperature at the target test flight altitude in real time, calculate the simulated air density at the target test flight altitude in real time, and calculate the loading torque at the corresponding steady-state test condition point in real time based on the simulated air density, the set equivalent advance ratio, and the target engine speed, according to the propeller aerodynamic attenuation model. Based on the loading torque, the dynamometer is driven in a closed loop to force the engine under test to output a speed consistent with the real propeller aerodynamic attenuation at the corresponding steady-state test condition point at different simulated altitudes.
[0011] An emission measurement system is used to connect to the exhaust port of the exhaust pressure simulation unit. The emission measurement system includes an active gas extraction and pressure stabilization unit, which is used to actively extract sample gas under the low pressure environment generated by the exhaust pressure simulation unit and maintain the sample gas pressure entering the emission analyzer within a set working pressure window. The emission measurement system actively extracts sample gas for sampling and heating. Then, the emission analyzer and particulate matter measuring device measure and analyze the heated sample gas to obtain emission measurement and analysis data.
[0012] The data acquisition and processing system is connected to the engine under test, dynamometer, emission analyzer, and particulate matter measuring device. It is used to collect and process the test operating parameters of the engine under test, the operating parameters of the dynamometer, and emission measurement and analysis data during the test of the engine under test according to the preset experimental procedure, and output the test results.
[0013] Preferably, the intake simulation unit is formed by arranging and connecting an air filter, an intake heat exchanger, an intake electric pressure regulating valve, and an intake pressure stabilizing tank in sequence according to the intake direction. The intake electric pressure regulating valve is installed on the gas pipeline of the intake port of the intake heat exchanger and the intake pressure stabilizing tank, and the outlet port of the intake pressure stabilizing tank is connected to the intake port of the engine under test.
[0014] Preferably, the exhaust pressure simulation unit is formed by arranging and connecting an exhaust heat exchanger, an exhaust electric pressure regulating valve, an exhaust buffer tank, and a vacuum pump in sequence according to the exhaust direction. The air inlet of the exhaust heat exchanger is connected to the exhaust port of the engine under test. The exhaust electric pressure regulating valve is arranged on the air inlet connecting the exhaust heat exchanger and the exhaust buffer tank. The exhaust port of the exhaust buffer tank is connected to the air inlet of the vacuum pump.
[0015] Preferably, the emission measurement system is arranged in sequence according to the exhaust direction, including a sampling probe, an exhaust filter, an active air pump, a buffer pressure stabilizing chamber, a back pressure regulating valve, and a heated sampling pipeline. The outlet of the heated sampling pipeline is divided into two branches, which are respectively connected to the emission analyzer and the particulate matter measuring device. The buffer pressure stabilizing chamber contains a pressure sensor, and the signal output terminal of the pressure sensor is connected to a PID closed-loop controller. The control output terminal of the PID closed-loop controller is connected to the back pressure regulating valve.
[0016] Preferably, the emission analyzer includes at least a non-spectral infrared analyzer for measuring CO and CO2, a hydrogen flame ionization detector for measuring total hydrocarbons, and a chemiluminescence detector for measuring NOx. The particulate matter measuring device is equipped with a dilution sampling channel and is capable of outputting particulate matter mass concentration or particulate matter number concentration.
[0017] Preferably, the load controller has a built-in load calculation module and a PID closed-loop control module. The load calculation module is used to calculate the loading torque in real time based on the propeller aerodynamic attenuation model and output it to the PID closed-loop control module. The PID closed-loop control module is connected to the dynamometer controller.
[0018] Preferably, the test bench system includes a directional cooling airflow simulation device, which comprises an adjustable ducted fan and a fairing. This device dynamically adjusts the cooling airflow velocity blowing onto the cylinder bank of the air-cooled piston engine under test, proportionally to the typical flight speed of the target test condition, ensuring that the cylinder head temperature matches the actual flight thermodynamic boundary under different altitude conditions. When the piston-type aero-engine emission test system is used for liquid-cooled piston engine testing, the test bench system provides a corresponding closed-loop control interface for coolant temperature, ensuring that the coolant temperature matches the actual flight thermodynamic boundary under different altitude conditions.
[0019] Preferably, the different test flight altitudes are set according to the target application scenario and flight envelope of the engine under test. Multiple steady-state test conditions coupled with load are set at each test flight altitude. The steady-state test conditions include at least the idle condition, cruise power condition, maximum continuous power condition, and maximum takeoff power condition.
[0020] As a preferred method, the atmospheric temperature and atmospheric pressure at different test flight altitudes are determined by calculation using the ISA model.
[0021] Another object of the present invention is to provide a method for testing emissions from a piston-type aircraft engine, performed according to the piston-type aircraft engine emission testing system, comprising:
[0022] Start the engine under test and warm it up at sea level and idle speed until the preset temperature parameters stabilize. Then, conduct tests at each test flight altitude in order from low to high altitude. At each test flight altitude, conduct tests at each steady-state operating point in order from low to high power.
[0023] In tests at different flight altitudes, an altitude environment simulation system is used to simulate the intake air temperature and pressure to match the target flight altitude, and an exhaust simulation is used to make the exhaust pressure of the engine under test consistent with the air pressure at the flight altitude. A propeller load simulation system is used to calculate the loading torque at the corresponding steady-state test conditions in real time based on the propeller aerodynamic attenuation model. The dynamometer is driven in a closed loop according to the loading torque to force the engine under test to output a speed consistent with the real propeller aerodynamic attenuation at the corresponding steady-state test conditions at different simulated altitudes.
[0024] During the test, engine operating parameters and pollutant concentrations are monitored in real time. After the preset steady-state judgment criteria are met, the emission measurement system is activated to continuously collect emission data. The emission measurement system actively extracts sample gas for sampling and heating. The heated sample gas is measured and analyzed by an emission analyzer and a particulate matter measuring device to obtain emission measurement and analysis data. The emission measurement and analysis data includes at least the emission index and specific emission of the emission components. The data acquisition and processing system collects and processes the test operating parameters of the engine under test, the dynamometer operating parameters, and the emission measurement and analysis data, and outputs the test results.
[0025] The emission test system of this invention, through a propeller load simulation system, can automatically achieve speed-torque coupling loading based on the real propeller aerodynamic characteristic spectrum with simulated altitude. The test conditions are completely consistent with the actual flight, effectively eliminating the deviation of the test conditions caused by the static loading mode of the traditional dynamometer. The test emission data can truly reflect the emission level of the engine in actual flight.
[0026] The emission test system of this invention precisely controls the intake pressure, temperature and exhaust environment pressure through an altitude environment simulation system, covering the altitude environment within the entire flight envelope of the engine, and provides a means of emission characteristic testing for the entire flight envelope; combined with the active exhaust pressure stabilization processing of the emission measurement system, it solves the technical problem of high-altitude low-pressure environment sample gas collection.
[0027] The emission test system of this invention sets steady-state operating conditions covering typical flight profiles, clarifies the criteria for determining operating condition stability and the data correction specifications, and effectively fills the technical gap in the steady-state emission test and verification standards for piston aero engines. Attached Figure Description
[0028] Figure 1 This is a schematic diagram of the emission test system for a piston-type aero-engine according to an embodiment of the present invention.
[0029] Figure 2 This is a schematic diagram of the connection between the high-altitude environmental simulation system and the engine under test in an embodiment of the present invention.
[0030] Figure 3 This is a schematic diagram of the emission measurement system according to an embodiment of the present invention.
[0031] Explanation of reference numerals in the attached figures:
[0032] 1—Test engine; 2—Bench system; 3—Coupling; 4—Intake simulation unit; 5—Exhaust pressure simulation unit; 6—Emission measurement system; 7—Dynamometer; 8—Load controller; 9—Data acquisition and processing system; 41—Air filter; 42—Intake heat exchanger; 43—Intake electric pressure regulating valve; 44—Intake pressure stabilizing tank; 51—Exhaust heat exchanger; 52—Exhaust electric pressure regulating valve; 53—Exhaust buffer tank; 54—Vacuum pump; 60—Sampling probe; 61—Exhaust filter; 62—Active suction pump; 63—Pressure sensor; 64—Buffer pressure stabilizing chamber; 65—Back pressure regulating valve; 66—Heated sampling pipeline; 67—Emission analyzer; 68—Particulate matter measuring device; 69—PID closed-loop controller. Detailed Implementation
[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
[0034] See Figure 1 As shown in the exemplary embodiment of this application, the piston-type aircraft engine emission testing system includes:
[0035] Test bench system 2 is used to support the engine under test 1 for testing;
[0036] The high-altitude environment simulation system includes an intake simulation unit 4 and an exhaust pressure simulation unit 5. The intake simulation unit 4 is used to connect to the intake port of the engine under test 1 to provide the engine under test 1 with intake air that matches the gas environment at different test flight altitudes. The exhaust pressure simulation unit 5 is used to connect to the exhaust port of the engine under test 1 to make the exhaust pressure of the engine under test 1 consistent with the air pressure at the test flight altitude.
[0037] The propeller load simulation system includes a dynamometer 7 and a load controller 8. The dynamometer 7 is mechanically connected to the output shaft of the engine under test 1 (e.g., via a coupling 3). The load controller 8 is connected to the dynamometer 7 and the altitude environment simulation system. It is used to read the atmospheric pressure and temperature at the target test flight altitude in real time, calculate the simulated air density at the target test flight altitude in real time, and calculate the loading torque at the corresponding steady-state test condition point in real time based on the simulated air density, the set equivalent forward ratio, and the target engine speed, according to the propeller aerodynamic attenuation model. Based on the loading torque, the dynamometer 7 is driven in a closed loop to force the engine under test 1 to output a speed consistent with the real propeller aerodynamic attenuation at the corresponding steady-state test condition point at different simulated altitudes.
[0038] The emission measurement system 6 is used to connect to the exhaust port of the exhaust pressure simulation unit 5. The emission measurement system 6 includes an active gas extraction and pressure stabilization unit, which is used to actively extract sample gas under the low pressure environment generated by the exhaust pressure simulation unit 5 and maintain the sample gas pressure entering the emission analyzer 67 within a set working pressure window. The emission measurement system 6 actively extracts sample gas for sampling and heating. The heated sample gas is then measured and analyzed by the emission analyzer 67 and the particulate matter measuring device 68 to obtain emission measurement and analysis data.
[0039] The data acquisition and processing system 9 is connected to the engine under test 1, the dynamometer 7, the emission analyzer 67, and the particulate matter measuring device 68. It is used to collect and process the test operation parameters of the engine under test 1, the dynamometer operation parameters, and the emission measurement and analysis data during the test of the engine under test 1 according to the preset experimental procedure, and output the test results.
[0040] According to embodiments of this application, the engine operating parameters include engine speed, torque, cylinder head temperature, exhaust temperature, intake pressure, intake temperature, fuel flow rate, air-fuel mixture ratio, ambient temperature, ambient atmospheric pressure, and ambient relative humidity.
[0041] According to an embodiment of this application, the emission measurement and analysis data processing in this application includes: plotting the correlation curves of the specific emission amount of the emission components with flight altitude and engine power, forming an emission characteristic map covering the entire emission envelope.
[0042] According to the embodiments of this application, the test bench system 2 may include an engine mounting base, an engine connection flange, and an auxiliary system interface, for mounting and fixing the piston-type aero-engine under test, and providing auxiliary functions such as fuel supply, lubrication circuit, and coolant circulation to the engine under test after connection.
[0043] According to one embodiment of this application, see Figure 2As shown, the intake simulation unit 4 is formed by an air filter 41, an intake heat exchanger 42, an intake electric pressure regulating valve 43, and an intake pressure stabilizing tank 44 arranged and connected in sequence according to the intake direction. The intake electric pressure regulating valve 43 is installed on the gas pipeline at the intake port of the intake heat exchanger 42 and the intake pressure stabilizing tank 44, and the outlet port of the intake pressure stabilizing tank 44 is connected to the intake port of the engine under test 1. According to the embodiment of this application, the intake simulation unit 4 generates a low-pressure and low-temperature environment corresponding to the target flight altitude in real time at the engine intake end. The pressure regulation simulation is achieved by using a combination structure of the intake electric pressure regulating valve 43 and the intake pressure stabilizing tank 44, thereby forming a controllable low-pressure environment corresponding to the target flight altitude upstream of the engine intake. For example, the intake pressure regulation accuracy should not be greater than ±0.5 kPa. A multi-stage heat exchanger is used as the intake heat exchanger 42 to cool the intake air to simulate the high-altitude low-temperature environment. For example, the intake temperature control accuracy should not be greater than ±2 ℃.
[0044] According to one embodiment of this application, see Figure 2 As shown, the exhaust pressure simulation unit 5 is formed by an exhaust heat exchanger 51, an exhaust electric pressure regulating valve 52, an exhaust buffer tank 53, and a vacuum pump 54 arranged and connected in sequence according to the exhaust direction. The inlet of the exhaust heat exchanger 51 is connected to the exhaust port of the engine under test 1. The exhaust electric pressure regulating valve 52 is arranged on the pipeline connecting the inlet of the exhaust heat exchanger 51 and the exhaust buffer tank 53. The exhaust port of the exhaust buffer tank 53 is connected to the inlet of the vacuum pump 54. According to an embodiment of this application, the exhaust pressure simulation unit 5 is equipped with an exhaust electric pressure regulating valve 52 and a vacuum pump 54 at the end of the exhaust pipeline to maintain the exhaust outlet pressure consistent with the atmospheric pressure at the target altitude. For example, the exhaust environment pressure control accuracy should not exceed ±0.5 kPa, and the dynamic response time of the throttling element should not exceed 2 seconds to ensure the back pressure control accuracy under engine exhaust pulse conditions.
[0045] According to one embodiment of this application, see Figure 3 As shown, the emission measurement system 6 is sequentially connected in the exhaust direction, comprising a sampling probe 60, an exhaust filter 61, an active air extraction pump 62, a buffer pressure stabilizing chamber 64, a back pressure regulating valve 65, and a heated sampling pipeline 66. The outlet of the heated sampling pipeline is split into two branches, connected to an emission analyzer 67 and a particulate matter measuring device 68, respectively. A pressure sensor 63 is located within the buffer pressure stabilizing chamber 64. The signal output of the pressure sensor 63 is connected to a PID closed-loop controller 69, and the control output of the PID closed-loop controller 69 is connected to the back pressure regulating valve 65. According to an embodiment of this application, the sampling probe is installed in the exhaust mixing uniformity area at least 0.5 meters or 3 times the pipe diameter downstream of the exhaust pipe outlet section of the engine under test, whichever is greater.
[0046] Since conventional analyzers cannot operate effectively in high-altitude, low-pressure environments, embodiments of this application include an active exhaust gas extraction and stabilization unit consisting of an active exhaust gas pump and a buffer pressure stabilization chamber. The active exhaust gas pump actively extracts the sample gas from the low-pressure exhaust flow and pumps it into the buffer pressure stabilization chamber. The buffer pressure stabilization chamber reduces the impact of exhaust gas pulsation on the stability of the gas analyzer's inlet pressure, and a pressure sensor monitors the pressure inside the buffer pressure stabilization chamber in real time. A PID closed-loop control module (such as a PID closed-loop controller) dynamically adjusts the opening of the back pressure regulating valve and the rotation speed of the active exhaust gas pump based on pressure feedback, eliminating engine exhaust gas pulsation and forcibly maintaining the sample gas pressure entering the gas analyzer inlet at a constant level within the gas analyzer's specified atmospheric pressure operating window.
[0047] According to embodiments of this application, the sample gas contact component of the active exhaust extraction unit is made of high-temperature resistant material and can be equipped with a heat tracing structure to prevent hydrocarbon condensation and particulate matter deposition. In this application, the sampling pipeline uses a heated pipeline throughout, with a heating temperature not lower than 191±11℃.
[0048] According to one embodiment of this application, the emission analyzer is equipped with at least a non-dispersive infrared analyzer (NDIR) for measuring CO and CO2, a flame ionization detector (FID) for measuring total hydrocarbons (THC), and a chemiluminescence detector (CLD) for measuring NOx; the particulate matter measuring device is configured with a dilution sampling channel and is capable of outputting particulate matter mass concentration (PM) or particulate matter number concentration (PN).
[0049] According to one embodiment of this application, the load controller communicates in a closed loop with the altitude environment simulation system and the dynamometer. The load controller has a built-in load calculation module and a PID closed-loop control module. The load calculation module is used to calculate the loading torque in real time based on the propeller aerodynamic attenuation model and output it to the PID closed-loop control module. The PID closed-loop control module is connected to the dynamometer controller.
[0050] According to one embodiment of this application, the test bench system includes a directional cooling airflow simulation device. This device comprises an adjustable ducted fan and a fairing, capable of dynamically adjusting the cooling airflow velocity blown onto the cylinder bank of the air-cooled piston engine under test in proportion to the typical flight speed of the target test condition, thus ensuring that the cylinder head temperature matches the actual flight thermodynamic boundary under different high-altitude conditions. According to another embodiment of this application, the outlet of the adjustable ducted fan is connected to the inlet side of the fairing, and the outlet side of the fairing faces the cylinder bank of the air-cooled piston engine to blow cool air onto the cylinder bank of the air-cooled piston engine under test, thereby regulating the cylinder head temperature. This technical solution is specific to air-cooled piston engines; this device is not required for liquid-cooled piston engines.
[0051] According to one embodiment of this application, the different test flight altitudes are set according to the target application scenario and flight envelope of the engine under test. Each test flight altitude is equipped with multiple steady-state test conditions coupled to the load. The steady-state test conditions include at least the idle condition, cruise power condition, maximum continuous power condition, and maximum takeoff power condition.
[0052] According to one embodiment of this application, the atmospheric temperature and atmospheric pressure at different test flight altitudes are determined by calculation using an ISA model. As an example, based on the target application scenario and flight envelope of the engine under test, multiple typical flight altitudes are set, with no fewer than five test flight altitudes. These altitudes should include at least sea level and the highest altitude permissible for normal operation of the engine under test, and should be evenly distributed within an intermediate altitude range. The corresponding atmospheric temperature T(h) and atmospheric pressure P(h) for each flight altitude are calculated using the International Standard Atmosphere (ISA) model.
[0053] , ;
[0054] In the formula, T0 is the standard sea-level temperature, 288.15 K; h is the altitude (m); L is the temperature lapse rate, 0.0065 K / m; P0 is the standard atmospheric pressure at sea level, 101325 Pa; T(h) is the atmospheric temperature (K) at altitude h; P(h) is the atmospheric pressure (Pa) at altitude h; and g is the acceleration due to gravity, 9.80665 m / s². 2 R is the gas constant for dry air, 287.05 J / (kg·K).
[0055] As an example, at each set test flight altitude, no fewer than five steady-state test conditions are set. These steady-state test conditions should include at least idle, cruise power, maximum continuous power, and maximum takeoff power conditions. For instance, the rotational speed and torque at each steady-state test condition in this application are dynamically determined by the load calculation module in the load controller according to the following formula:
[0056] For a fixed-pitch propeller, the torque calculation formula for each steady-state test point is as follows:
[0057] ;
[0058] In the formula, For height Equivalent forward ratio The load torque at the point is expressed in N·m. To correspond to the propeller torque coefficient at the equivalent advance ratio, from The corresponding values are obtained by interpolation of the graph (provided by propeller wind tunnel test data, flight test data, or verified aerodynamic design simulation data); For height Air density at this location, in kg / m³ 3 Calculated based on the international standard atmospheric model; The propeller speed is expressed in r / s. The diameter of the propeller is in meters (m).
[0059] The air density at each test flight altitude is calculated using the following formula:
[0060] ;
[0061] Equivalent forward ratio Typical flight speeds corresponding to each operating condition Sure:
[0062] ;
[0063] in, The typical flight speed for this operating condition is taken from the flight manual of the aircraft equipped with the engine. If only ground static thrust data is available, then... =0.
[0064] When the load factor k0 is known under ground conditions, the load torque is corrected and simplified into the following calculation form:
[0065] ;
[0066] in, The standard air density at sea level is 1.225 kg / m³. 3 This simplified form only applies to the equivalent advance ratio at each altitude. This method is applicable when the change is not significant (e.g., the rate of change is less than 5%). M(h) is the simplified load torque at height h, and k0 is the load coefficient.
[0067] According to an embodiment of this application, when the load calculation module calculates the loading torque of the dynamometer, it also limits the electric minimum loading torque according to preset conditions and set limits: for example, the minimum load torque actually applied by the dynamometer under idle conditions shall not be less than 5% of the rated torque of the engine under maximum takeoff conditions, and shall not be less than the minimum stable control load specified by the dynamometer; when the calculated torque value is less than 5% of the rated torque of the engine under maximum takeoff conditions or the limit of the minimum stable control load specified by the dynamometer, the limit shall be used instead, and the deviation between the actual loading value and the calculated value shall be recorded in the test report.
[0068] For a constant speed variable pitch propeller, the load of the dynamometer is determined based on its load characteristic spectrum, which represents the relationship between power and torque at the target constant speed during each flight phase. The target constant speed is determined by the propeller governor setting value, and the power at each flight phase is determined by the engine operating power specified in the aircraft flight manual.
[0069] According to the embodiments of this application, during specific testing, the engine under test is started and warmed up under sea-level conditions and idle operation until the preset temperature parameters stabilize: for liquid-cooled engines, both coolant and lubricating oil temperatures stabilize within the normal operating range specified in the engine flight manual; for air-cooled engines, both cylinder head and lubricating oil temperatures stabilize within the normal operating range specified in the engine flight manual. Before testing, it is confirmed that all auxiliary systems are operating normally, with no oil or air leaks or abnormal vibrations; the sampling system heating pipe temperature reaches the set value; and the data acquisition system is functioning normally before proceeding to the formal test.
[0070] According to the embodiments of this application, during testing, emissions tests are performed sequentially at each flight altitude, from low to high altitude. At each flight altitude, emissions tests are performed sequentially at each steady-state operating point, from low power to high power. When switching flight altitudes, the engine is first adjusted to idle mode, and then the intake pressure, intake temperature, and exhaust ambient pressure of the engine output by the altitude environment simulation system are adjusted at a preset rate (e.g., not exceeding 1 kPa / min) to match the target flight altitude. Significant adjustments to the intake pressure and exhaust ambient pressure at power levels exceeding cruise power are strictly prohibited to prevent engine surge or stalling. After altitude switching, the operating condition test at that altitude can only begin after the parameters of the altitude environment simulation system have stabilized and remained stable for at least 5 minutes. When switching between adjacent operating conditions at the same flight altitude, a wait of at least 3 minutes should be made to allow the engine thermal state and emission concentration to fully respond to the new operating condition.
[0071] According to the embodiments of this application, at each steady-state operating point, after the engine speed, torque, exhaust temperature, and gaseous pollutant concentration meet the following stability criteria, emission data and engine operating parameters are simultaneously and continuously collected: within 30 consecutive seconds, the engine speed fluctuation does not exceed ±1% of the target value, the torque fluctuation does not exceed ±2% of the target value, the relative standard deviations of CO, HC, and NOx concentrations are all less than 5%, and the fluctuations of intake pressure and exhaust back pressure should not exceed ±0.5 kPa. After meeting the stability criteria, the data collection time is not less than 60 seconds.
[0072] According to the embodiments of this application, after data collection, the validity of the collected raw data is checked, and invalid data segments caused by instrument malfunction, excessive fluctuations in operating conditions, etc., are removed; the duration of a valid data segment must not be less than 30 seconds, otherwise the test under that operating condition is considered invalid and must be retested. If the concentration of gaseous pollutants is measured on a dry basis (i.e., the sample gas is dried before entering the analyzer), the dry basis concentration should be corrected to a wet basis concentration according to the standard method of GB / T 8190.1-2010 before subsequent calculations. Since the water vapor content in the atmosphere will affect the formation and measurement results of NOx, the measured NOx concentration should be corrected for humidity according to the standard method of GB / T 8190.1-2010.
[0073] The emission index and specific emission amount of each emission component are calculated as follows:
[0074] Emissions index based on fuel consumption:
[0075] (g / kg);
[0076] Based on the specific emissions from the output power:
[0077] (g / kWh);
[0078] In the formula, To represent the mass emission of exhaust component i during the stable sampling period under this operating condition, g; is the engine fuel consumption during the same period, in g; W is the engine output power during the same period, in kWh.
[0079] Based on the processed data, correlation curves of the specific emissions of each emission component as a function of flight altitude and engine power are plotted to form an emission characteristic map covering the entire emission envelope.
[0080] A further embodiment of the present invention provides a method for testing emissions from a piston-type aircraft engine, performed according to the piston-type aircraft engine emission testing system, comprising:
[0081] Start the engine under test and warm it up at sea level and idle speed until the preset temperature parameters stabilize. Then, conduct tests at each test flight altitude in order from low to high altitude. At each test flight altitude, conduct tests at each steady-state operating point in order from low to high power.
[0082] In tests at different flight altitudes, an altitude environment simulation system is used to simulate the intake air temperature and pressure to match the target flight altitude, and an exhaust simulation is used to make the exhaust pressure of the engine under test consistent with the air pressure at the flight altitude. A propeller load simulation system is used to calculate the loading torque at the corresponding steady-state test conditions in real time based on the propeller aerodynamic attenuation model. The dynamometer is driven in a closed loop according to the loading torque to force the engine under test to output a speed consistent with the real propeller aerodynamic attenuation at the corresponding steady-state test conditions at different simulated altitudes.
[0083] During the test, engine operating parameters and pollutant concentrations are monitored in real time. After the preset steady-state judgment criteria are met, the emission measurement system is activated to continuously collect emission data. The emission measurement system actively extracts sample gas for sampling and heating. The heated sample gas is measured and analyzed by an emission analyzer and a particulate matter measuring device to obtain emission measurement and analysis data. The emission measurement and analysis data includes at least the emission index and specific emission of the emission components. The data acquisition and processing system collects and processes the test operating parameters of the engine under test, the dynamometer operating parameters, and the emission measurement and analysis data, and outputs the test results.
[0084] The foregoing has shown and described the basic principles and main features of the present invention and its advantages. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects. The scope of the present invention is defined by the appended claims rather than the foregoing description, and therefore all changes falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention.
[0085] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
Claims
1. A piston-type aircraft engine emission testing system, characterized in that, include: A test bench system is used to support the engine under test for testing. The high-altitude environment simulation system includes an intake simulation unit and an exhaust pressure simulation unit. The intake simulation unit is used to connect to the intake port of the engine under test to provide the engine under test with intake air that matches the gas environment at different test flight altitudes. The exhaust pressure simulation unit is used to connect to the exhaust port of the engine under test to make the exhaust pressure of the engine under test consistent with the air pressure at the test flight altitude. The propeller load simulation system includes a dynamometer and a load controller. The dynamometer is mechanically connected to the output shaft of the engine under test. The load controller is connected to the dynamometer and the altitude environment simulation system. It is used to read the atmospheric pressure and temperature at the target test flight altitude in real time, calculate the simulated air density at the target test flight altitude in real time, and calculate the loading torque at the corresponding steady-state test condition point in real time based on the simulated air density, the set equivalent advance ratio, and the target engine speed, according to the propeller aerodynamic attenuation model. Based on the loading torque, the dynamometer is driven in a closed loop to force the engine under test to output a speed consistent with the real propeller aerodynamic attenuation at the corresponding steady-state test condition point at different simulated altitudes. An emission measurement system is used to connect to the exhaust port of the exhaust pressure simulation unit. The emission measurement system includes an active gas extraction and pressure stabilization unit, which is used to actively extract sample gas under the low pressure environment generated by the exhaust pressure simulation unit and maintain the sample gas pressure entering the emission analyzer within a set working pressure window. After the emission measurement system actively extracts the sample gas for sampling and heating, the emission analyzer and particulate matter measuring device measure and analyze the heated sample gas to obtain emission measurement and analysis data. The data acquisition and processing system is connected to the engine under test, dynamometer, emission analyzer, and particulate matter measuring device. It is used to collect and process the test operating parameters of the engine under test, the operating parameters of the dynamometer, and emission measurement and analysis data during the test of the engine under test according to the preset experimental procedure, and output the test results.
2. The piston-type aero-engine emission testing system according to claim 1, characterized in that, The intake simulation unit is formed by an air filter, an intake heat exchanger, an intake electric pressure regulating valve, and an intake pressure stabilizing tank arranged and connected in sequence according to the intake direction. The intake electric pressure regulating valve is installed on the gas pipeline of the intake port of the intake heat exchanger and the intake pressure stabilizing tank, and the outlet port of the intake pressure stabilizing tank is connected to the intake port of the engine under test.
3. The piston-type aero-engine emission testing system according to claim 1, characterized in that, The exhaust pressure simulation unit is formed by an exhaust heat exchanger, an exhaust electric pressure regulating valve, an exhaust buffer tank, and a vacuum pump arranged and connected in sequence according to the exhaust direction. The air inlet of the exhaust heat exchanger is connected to the exhaust port of the engine under test. The exhaust electric pressure regulating valve is arranged on the air inlet connecting the exhaust heat exchanger and the exhaust buffer tank. The exhaust port of the exhaust buffer tank is connected to the air inlet of the vacuum pump.
4. The piston-type aero-engine emission testing system according to claim 1, characterized in that, The emission measurement system is arranged in sequence according to the exhaust direction, including a sampling probe, an exhaust filter, an active air pump, a buffer pressure stabilizing chamber, a back pressure regulating valve, and a heated sampling pipeline. The outlet of the heated sampling pipeline is divided into two branches, which are respectively connected to the emission analyzer and the particulate matter measuring device. The buffer pressure stabilizing chamber contains a pressure sensor, and the signal output terminal of the pressure sensor is connected to a PID closed-loop controller. The control output terminal of the PID closed-loop controller is connected to the back pressure regulating valve.
5. The piston-type aero-engine emission testing system according to claim 1, characterized in that, The emission analyzer includes at least a non-spectral infrared analyzer for measuring CO and CO2, a flame ionization detector for measuring total hydrocarbons, and a chemiluminescence detector for measuring NOx. The particulate matter measuring device is equipped with a dilution sampling channel and is capable of outputting particulate matter mass concentration or particulate matter number concentration.
6. The piston-type aero-engine emission testing system according to claim 1, characterized in that, The load controller has a built-in load calculation module and a PID closed-loop control module. The load calculation module is used to calculate the loading torque in real time based on the propeller aerodynamic attenuation model and output it to the PID closed-loop control module. The PID closed-loop control module is connected to the dynamometer controller.
7. The piston-type aircraft engine emission testing system according to claim 1, characterized in that, The test bench system includes a directional cooling airflow simulation device, which includes an adjustable ducted fan and a wind guide fairing. It can dynamically adjust the cooling airflow velocity blown onto the cylinder group of the air-cooled piston engine under test according to the typical flight speed of the target test conditions, so that the cylinder head temperature is consistent with the actual flight thermodynamic boundary under different high-altitude conditions.
8. The piston-type aero-engine emission testing system according to claim 1, characterized in that, The different test flight altitudes are set according to the target application scenario and flight envelope of the engine under test. Multiple steady-state test conditions coupled with load are set at each test flight altitude. The steady-state test conditions include at least the idle condition, cruise power condition, maximum continuous power condition and maximum takeoff power condition.
9. The piston-type aircraft engine emission testing system according to claim 1, characterized in that, Atmospheric temperature and atmospheric pressure at different test flight altitudes were determined using the ISA model.
10. A method for testing emissions from a piston-type aircraft engine, performed using the piston-type aircraft engine emission testing system according to any one of claims 1-9, comprising: Start the engine under test and warm it up at sea level and idle speed until the preset temperature parameters stabilize. Then, conduct tests at each test flight altitude in order from low to high altitude. At each test flight altitude, conduct tests at each steady-state operating point in order from low to high power. In tests at different flight altitudes, an altitude environment simulation system is used to simulate the intake air temperature and pressure to match the target flight altitude, and an exhaust simulation is used to make the exhaust pressure of the engine under test consistent with the air pressure at the flight altitude. A propeller load simulation system is used to calculate the loading torque at the corresponding steady-state test conditions in real time based on the propeller aerodynamic attenuation model. The dynamometer is driven in a closed loop according to the loading torque to force the engine under test to output a speed consistent with the real propeller aerodynamic attenuation at the corresponding steady-state test conditions at different simulated altitudes. During the test, engine operating parameters and pollutant concentrations are monitored in real time. After the preset steady-state judgment criteria are met, the emission measurement system is activated to continuously collect emission data. The emission measurement system actively extracts sample gas for sampling and heating. The heated sample gas is measured and analyzed by an emission analyzer and a particulate matter measuring device to obtain emission measurement and analysis data. The emission measurement and analysis data includes at least the emission index and specific emission of the emission components. The data acquisition and processing system collects and processes the test operating parameters of the engine under test, the dynamometer operating parameters, and the emission measurement and analysis data, and outputs the test results.