Papers by Keyword: CNG Engine

Abstract: This paper indicates the early experimental results of a Ricardo model CNG engine R&D activity in Vietnam, the experiments were mainly focused on the effects of compression ratio on operating parameters of the tested single cylinder CNG engine particularly designed and fabricated for varying compression ratio purpose. The compression ratio was set in the range of ε = 10 to 15 with the change step of Δε = 1. For each compression ratio, the engine speed were varried from 1000rpm to 2200rpm with the change step of Δn = 200. The early spark angle was also changed to find out the maximum break torque. The limitation of compression ratio and engine speed at each operating point was determined by vibration signal and abnormal sound. The experimental results indicated the early spark angle must be adjusted premature in case of compression ratio and/or engine speed enhenced. Especially, the portion of indispensable power to perform the compression stroke is smaller in comparison with the portion to execute the both strokes of intake and exhaust. In addition, the shape of combustion chamber affected strongly the operating characteristics also found in this study.

Abstract: Diesel engines are widely used in logistics and haulage as vehicular prime movers. In the mechanized and fast-moving forward world of today, the consumption of petroleum products has become an important yardstick of a country’s prosperity. This ever-increasing consumption has led the world to face the twin challenge of energy shortage and environmental deterioration. Natural gas has been one of the highly considered alternative fuels for both spark ignition (S.I) and compressed ignition (C.I.) engines. The advantages and benefits of CNG have made it the preferred choice as alternative fuel in the transportation sector. This present study focused on the effects of retrofitted direct injection C.I. engine with mono-CNG system to its performance and exhaust emissions. The engine speed was varied from 850 rpm to 2500 rpm, with load test conditions of 0Nm, 27.12Nm and 53.23Nm, using an engine dynamometer. Results indicated that CNG has the potential to provide better fuel consumption compared to diesel fuel. Meanwhile, the characteristics of exhaust gas emissions such as smoke opacity and CO2 gave promising results compared to CO, HC and NOX, for diesel combustion.

Abstract: Experimental research on the effect of excess air ratio on dynamic and emission performance of turbocharged lean-burned CNG engine. The 12 test conditions contain engine speeds of 1300r/min, 1600r/min, and 1900r/min, with 25%, 50%, 75%, 100% load separately. When keeping other combustion boundary conditions unchanged, the excess air ratio has little effect on engine output torque at almost all test conditions, but has obvious effect on CH4 and NOx emission. With the excess air ratio increasing, the emission of CH₄ has increased while the NOx emission has decreased significantly. When the λ value is in the range of 1.4-1.45, the emission level is lower.

Abstract: We set up one cylinder of CNG engine by using GT-Power software and the compression ratio and the knock are studied. The conclusions are as follows: when the compression ratio increases, the rate of pressure rise of acute burning period increases; The maximum cylinder pressure increases; The maximum temperature decreased slightly and after burning period the temperature increases; The critical knocking compression ratio appears at the full load of 4000rpm conditions; If we only consider it knocking or not, the engine compression ratios can change from 10 to 11.

Abstract: Experimental study on the combustion and emission performance of turbocharged lean-burned CNG engine by the ignition time. Speed of the engine is 1340r/min,1615r/min,1890r/min,with 25%, 50%,75%,100% load. Results show that when keeping other combustion boundary conditions unchanged, the effect of the ignition time on engine output torque and CH4 is little,the effect changes as speed varies from low speed and load conditions to higher level.However,the effects of ignition time on NOx emissions are huge.With the backward changes of the ignition time,NOx emissions has decreased significantly.

Abstract: The paper has modeled and simulated the combustion process of big bore CNG engine by three-dimensional simulation software AVL FRIE. Based on test validation in the model, the effect on position of the dual spark plug for cylinder initial flame kernel development and flame propagation process was researched. The results showed that: When A=0.5, the flame propagation distance shortened by half, a certain intensity of turbulence formed when the compression stroke ended, the combustion speed was the fastest, the combustion duration was the shortest. If dual spark plug spacing is too small, the two flames meet prematurely will cause interfere with each other, and reduce the combustion speed of the overlapping region of the flame surface, increase the heat losses. Otherwise,if the distance is too large , close to the combustion chamber wall, the combustion space is narrow, the flame propagation space is restricted, then flame development is slow.

Abstract: The distribution of temperature and NOX concentration field under different crank angle of a CNG direct-injection engine converted from a four-valve gasoline vehicle engine are calculated by the computation model of the CNG direct-injection engine work process using CFD software. The results show that the temperature field spreads around the center of the spark plug in initial combustion period. The position of maximum temperature in combustion chamber moves from the spark plug to the wall and temperature tends to uniform distribution as the piston goes down along with the spread of flame front and the completion reaction after the flame. Temperature distribution is vital to the generation of NOX which changes along with high-temperature zone. The change principle of quantity of NOX in the cylinder is that at first, the quantity continues increasing, then declines, and finally remains stable. Besides this, the generation amount of NOX increase along with the speed.

Abstract: To reduce the HC emissions of a CNG engine during starting period, starting experiments were carried out on a CNG engine. Injection pulse width (IPW) and spark advance angle () were controlled. The results indicate that wider injection pulse width and earlier spark timing cause higher HC emissions. To guarantee a reliable start and low HC emissions, the engine should start with relatively wider injection pulse width and earlier spark timing, and the injection pulse width and spark advance angle should be reduced gradually after the engine speed is steady.

Abstract: Power performance tests of natural gas engine were carried out using a self-dependent developed electronic injection system and ignition system, and a comparative analysis between the natural gas engine and original gasoline engine was conducted. The result shows that if the gasoline engine is fueled with NG torque of the engine decreases and with the throttle opening increases, the decrease amplitude increases. Developing a suitable electronic ignition system can recover engine torque to some extent. Under the conditions that both throttle opening and rotation speed of the engine are constant, MBT angle increases with the decrease of mixture concentration.

Abstract: Real-time model is one of the key elements in Hardware In Loop (HIL) simulations. A new Crush Natural Gas (CNG) Turbo Engine model and HIL simulation platform are presented in this paper. The platform provides simulations of engine speed, torque, dynamic load, turbo, exhaust gas temperature and emissions conditions. The platform is based on Matlab/Simulink, Labview and can be seamlessly connected with a CNG engine control unit (ECU). Simulation results indicate that platform provide us higher development efficiency as well as lower reduce development expense of ECU.