Search

For a long time, pre-chamber jet ignition has been an effective method to achieve stable lean-combustion of the engine. However, due to the lack of an additional fuel injector, the passive pre-chamber easily leads to unstable combustion and even misfires during the engine's low-speed working conditions. This study used simulation and optical single-cylinder engine visualization experiments to investigate the ignition and combustion performance of the pre-chamber spark plug (PCSP) ignition system and different orientations of the scavenging jet nozzle in the cylinder. The results indicate that the PCSP at low speed (1200 r/min) can improve the lean-combustion load performance by up to 6.7% compared with traditional high-energy spark ignition but cannot significantly improve the lean combustion limit and stability. In addition, under each λ condition, the scavenging jet nozzle face toward one of the intake valves (IV2) is most advantageous. The effect of lean combustion on reducing NO began to manifest after λ > 1.3 and achieved the best at 1.6. This kind of jet ignition pre-chamber provides a more stable ignition solution than high-energy spark ignition for low speed and medium/low load aspects. [ABSTRACT FROM AUTHOR]

Knock combustion has become the main barrier in the development of hydrogen internal combustion engine (ICE). This study investigated the factors (engine speed, spark timing, injection timing, and injection pressure) influencing knock combustion based on the data of a bench test and a 1D simulation model on GT-Power. And the Taguchi-Grey method was applied to rank the four factors. Results showed that knock combustion occurs under lower relative air-fuel equivalence ratio, the percentage of the knock cycle in 100 continuous cycles decreased from 45.8% to 0 when λ raised from 2.47 to 3.37. The advancement of injection timing and the decreasing of injection pressure, along with higher engine speed, facilitate the occurrence of knock. However, the knock tendency increases first and then declines with the advancement of spark timing. Among all the factors considered, engine speed has the greatest influence on knock combustion, whose contribution rate is 50.64%. • Injection timing and pressure, spark timing, and engine speed can affect knock. Engine speed has the largest impact on knock. • The advancement of spark timing makes the knock tendency increase first and then decline. • Engine speed has the largest contribution on knock combustion through the Taguchi-Grey method. [ABSTRACT FROM AUTHOR]

Hydrogen engines show great potential as a power source with good combustion performance, zero carbon emissions, and diverse sources. However, the exhaust emission characteristics with high water vapor (H 2 O) content have not yet been clarified. This study presents the exhaust emissions of a heavy-duty direct-injection hydrogen engine under various operational parameters, with a focus on the H 2 O content. The results reveal important exhaust emissions characteristics of the hydrogen engine, including lower exhaust temperature (200 °C–400 °C), higher unburned H 2 emissions (up to 17100 ppm), less nitrogen oxide (NO) generation (<1000 ppm), and higher H 2 O content (6%–40%). Additionally, unburned H 2 rises, and NO and H 2 O decrease as the excess air ratio (λ) increases. When λ is greater than 3, NO levels fall sharply to below 100 ppm. Optimal emissions performance is achieved with a 5 °CA BTDC ignition timing where low levels of H 2 , H 2 O, and NO are maintained. Increasing hydrogen injection pressure decreases H 2 but raises exhaust temperature, H 2 O, and NO emissions. Excessively delaying hydrogen injection timing adversely affects the concentration gradient in the cylinder, increasing unburned H 2 emissions. The best emissions performance is observed at a hydrogen injection timing of 110 °CA BTDC. • Studied the exhaust emissions of heavy-duty direct-injection hydrogen engine. • Clarified the high H 2 O and H 2 emission characteristics of hydrogen engines. • Analyzed lower NO emissions and exhaust temperature from hydrogen engines. • Explored the effects of operating conditions on emission characteristics. [ABSTRACT FROM AUTHOR]

Poor designed powertrain mounting system can lead to severe resonance when road excitation frequency is consistent with the natural frequency of the powertrain mounting system, which results in vertical vibration of the vehicle. In addition, double-layer vibration isolation and hydraulic engine mount (HEM) are widely used for vibration attenuation of electric powertrain. This paper focuses on the vertical vibration of electric vehicles under road excitation. An analytic model of powertrain shake characteristics considering the amplitude-frequency dependent nonlinearity of HEMs is established. Furthermore, the proposed nonlinear model is experimentally validated through rigid body modal test of the powertrain. Numerical simulation is carried out to investigate the influence of HEM parameters on powertrain shake characteristics. Simulation results demonstrate that the effective pumping area, upper chamber stiffness and inertia track effective cross-sectional area, and length of HEM have obvious impact on powertrain shake characteristics. Under the premise of ensuring vibration isolation performance under other conditions, optimization of the above HEM parameters can reduce peak value of car body vibration under road excitation and thus improve ride comfort. [ABSTRACT FROM AUTHOR]