In order to study the influence on engine performance by a variable-exhaust two-stroke engine as the unmanned aircraft power with removal of the variable exhaust system

the simulation of the cylinder's working process in the engine was established using Fire simulation software. In the model

the characteristics of the engine after removing the variable exhaust system were studied through simulation and test. The results showed that after removing the variable exhaust system under the condition of 2000r/min

10% throttle opening and 5500r/min

50% throttle opening

the scavenging efficiency of the engine and the output power were reduced. On this basis

using the simulation study method to optimize the exhaust outlet height parameters

the results showed that: after removing the variable system

the optimal value of the exhaust outlet height was 36.3mm

which can guarantee the common drone flight speed range. The scavenging efficiency is high under all operating conditions. The loss of engine indicator power is minimal

and the output power can satisfy the drone power demand.