PHYSICAL SIMULATION OF HIGH- AND MEDIUM-SPEED ENGINES POWERED BY NATURAL GAS

摘要

Engine conversion to natural gas facilitates reduction of expenses for fuel and motor oil, decrease in toxic emissions. This measure is especially urgent after validation of recent ecological norms for diesel engines, since it eliminates necessity to apply large and expensive urea-based catalytic converters required for diesel engines to conform with these requirements. In the course of projects performed by MADI aimed at development of high- and medium-speed natural gas engines, modular system of gas supply and electronic control system of gas diesel engine were designed and fabricated. Three modules can be applied for gas supply of the medium-speed 6 cylinder engine having D/S = 200/280 mm and one module -for the high-speed 6 cylinder engine having D/S = 107/124 mm. MADI carried out conversion of the high-speed diesel engine into gas diesel engine with minimized portion of ignition diesel fuel supplied by Common Rail system aiming at experimental adjustment of the aforementioned systems. Calibration of gas diesel engine was based on bench test results and simulation of operation using the computational complex developed by MADL The bench test results of the high-speed gas diesel engine demonstrated that experimental gas supply system and electronic control system made it possible to achieve higher rate of replacement of diesel fuel (from 5% under full loads to 33% at idle mode), high effective efficiency, as well as significant reduction of NO_x and CO_2 emissions. Lower torque was obtained at low speed than that of basic diesel engine. Calculated parameters of the medium-speed and high-speed gas diesel engines were compared under similar conditions (equal mean effective pressure, mean piston speed and pressure of boosted air), demonstrating close indicated values. It allowed to expect high parameters of the medium-speed gas diesel engine with application of the gas supply system and electronic control system developed for the high-speed gas diesel engine after their appropriate adaptation.