Abstract
Power efficiency of two-stroke spark-ignition engine is generally low because improper amount of fuel injection leads to a lot of unburned fuel loss during the engine working process. However, parameters of the fuel injection system are hard to confirm by aviation experiments due to expensive test costs. This paper proposes a method of calibrating injection parameters of two-stroke spark-ignition engine based on thermodynamic simulation and parameter optimum algorithm. Firstly, the one-dimensional thermodynamic model is built according to the internal structure and thermodynamic process of the engine; then, the model parameters are corrected according to the operating principle of the injector; after experimental verification of the model, considering both the engine power sufficiency and fuel economy, Analytic Hierarchy Process method is applied to look for the optimal injection amount and fuel injection advance angle at different engine working speeds; finally, an aeroengine experiment station with an electronic fuel injector system is built. Through simulation and experiment studies, it can be seen that when the engine speed changes from 3000 to 3500 RPM, the oil consumption rate of the optimal results is higher than that of the previous ones; when the aeroengine speed is higher than 4000 RPM, the oil consumption rate results of the optimal method are 10% to 27% higher than the original results. This paper can be a reference in the optimization of UAV aircraft engine.
Highlights
Two-stroke engine has been widely applied in the power system of small aerial equipment fuel-powered UAV because of the advantages of strong explosive and small size [1]
Performance of the engine with the Electronic fuel injector (EFI) system has been generally studied by setting up experimental stations which can test the output speed, torque, air-fuel ratio (AFR), cylinder pressure, and exhaust contents, and the researchers do a lot of experiments to optimize the engine structure or control method [4, 5]
When the two-stroke aeroengine starts to work, during the first stroke, firstly, the air-fuel mixture is sucked into the crankcase, and the scavenging port is opened when the pistons move from the bottom dead center (BDC) until the crankshaft rotates to the intake valve closed (IVC) angle, which can be seen in Figure 2. e exhaust port is opened from BDC until the crankshaft rotates to the emission valve closed (EVC) angle; the air-fuel mixture is compressed, and at the ignition advance angle before the top dead center (TDC), the engine is sparked
Summary
Two-stroke engine has been widely applied in the power system of small aerial equipment fuel-powered UAV because of the advantages of strong explosive and small size [1]. In order to estimate engine performance such as cylinder pressure, heat release rate, and fuel consumption, Venkatraman and Devaradjane [6] build the working mathematical model of a 4-stroke engine. Raut [10] use an exponential rate-based Wiebe heat release model, and the Pflaum formula is applied in the estimation of empirical coefficient of the heat transfer process From these works, it can be seen that engine performance study by using the mathematical model method is effective. Yang et al [18] have designed the controlled fuel process and studied the different intake air parameters to improve the engine dynamic performances In these works, the engine confirmatory experiments are far away from the real application of the aeroengine because the torque propeller mainly comes from the propeller air resistance. Engine experiment results which use the optimize injection MAP demonstrate that the oil consumption rate can be improved differently
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