Setup Of Small Diesel Engine Test Bench And Simulation Model Validation

The increasingly severer energy crisis and tighter emission regulations have drawn much attention among automobile companies and engine factories to reducing emissions and decreasing fuel consumption. Small diesel engine is characterized by its bad combustion performance and high emissions of NOx and particulate, which means improvement of engine’s working performance is necessary to meet requirement of emission regulations. Therefore, in order to find methods to improve small diesel engine’s performances, relevant tests should be conducted to acquire diesel engine’s performance parameters including power and economy performance, and one/three dimensional simulations need to be performed to analyze diesel engine’s cycle working process.In this paper, the setup of engine test bench is performed for a small diesel engine of non-load mobile machinery according to the general design scheme, based on general requirements and main functions. Diesel engine’s power, economy, and emission performance are tested and analyzed after installation and adjustment of test bench. After geometric model of diesel’s intake/exhaust port and combustion chamber are achieved by reverse engineering, 1-D and 3-D simulation models are built up respectively with the help of AVL BOOST and AVL FIRE software and validated through experimental data. Finally the processes of in-cylinder flow, spray and combustion are generally analyzed.The main contents and conclusions are as follows:1) According to diesel engine’s performance parameters and experimental target, test bench’s general requirements and main functions can be determined. Due to limited fund and special construction requirement, engine test bench should be set up through purchase and self-design.2) Selection and self design of corresponding component are performed according to general design scheme. Firstly, measuring and control equipment including dynamometer, accelerograph actuator, in-cylinder pressure sensor and NOx analyzer are chosen after brief description of their function and requirement. Then, basic function of controlling software is briefly introduced. Besides, design schemes of mechanical instruments such as engine base, resilient coupling, and encoder bracket are put forward and better design scheme is chosen according to application effect. Finally fuel-supplying system and exhaust pipe system are self-designed and processed.3) Corresponding performance tests are conducted after the installation and adjustment of test bench. Torque calibration, throttle position calibration, reference pressure calibration and TDC position calibration are achieved in order to get accurate experimental data. External characteristic, speed characteristic and emission characteristic test are performed under different working conditions and related characteristic curves and indicator diagrams are acquired. Finally, interfering signal of indicator diagrams is removed by FFT(=Fast Fourier Transmission) method by Matlab software.4) Cloud point model of diesel engine’s inner-flow field including combustion chamber and intake/exhaust port is obtained by 3-D scanning, then 3-D geometric model of diesel engine’s inner-flow field is acquired by reverse engineering. 1-D and 3-D simulation model are set up to investigate flow field, fuel injection and combustion process after validated by experimental data, which can be basic work to improve diesel engine’s performances.