Abstract:
Injection advance angle has a great effect on diesel engine performance, exhaust and sound emissions. An experimental investigation was conducted to acquire enough data and apply acoustic emission analysis techniques in order to analyze engine sound with respect to injection advance angle changing. A single cylinder diesel engine was used and the test rig was equipped with all necessary instruments to measure and record all the needed parameters. Engine sound emission is recorded and analyzed to determine the fundamental frequencies especially those relevant to the combustion process. Measurements were conducted at wide range of variations of injection advance angles and at different engine speeds and loads set by changing the dynamometer readings and fuel pump rack position. A special mechanism was designed, machined assembled to the injection pump drive coupling in order to enable the setting of different static fuel injection points. Optimum injection advance is 19 degree BTDC (the angle at which engine produces its maximum torque and operate smoothly and is achieved from BMEP calculations), measurements are done at it, before, and after it. A set of four microphone-audio amplifier arrays was used to measure the engine acoustic emission while a PC multichannel data acquisition system was used to collect and record the measured signals. Fast Fourier transform is applied on the combustion sound signals to get the amplitude-frequency relations at different operating conditions. The results show remarkable changes of these relations with the injection advance angle. Too early or very late injection advance angles result in irregular and rough engine operation.