Wuqiang Long

PDA and LDA Measurements of Large Angle Hollow Cone Spray Proposed for Hot-Premixed Combustion Type Diesel Engine

To study the characteristics of flow velocity and particle diameters in large angle conical spray proposed for hot-premixed combustion type Diesel engines, steady, and unsteady conical sprays have been analyzed using laser Doppler anemometry (LDA), and phase Doppler anemometry (PDA). Three injection pressures were used in steady experiments. In unsteady experiments, the frequency of injection was 20.7 Hz and the amount of injection fuel was 10.3 mg or 25.6 mg in each cycle. Distributions of bulk velocity, fluctuation intensity of the velocity, air entrainment rate, Sauter mean diameter of particles and correlation between particle diameter and velocity of the spray were obtained.

The influence of the enrichment injection angle on the performance of a pre-chamber spark ignition natural-gas engine

Using an enriched pre-chamber is an effective way to extend the lean limit, to reduce the nitrogen oxide emissions and to avoid abnormal combustion in spark ignition natural-gas engines. Enrichment injection in the pre-chamber of a spark ignition natural-gas engine determines the flow field and the fuel–air mixture formation quality in the pre-chamber and has a profound influence on the combustion performance of the engine. In order to study the characteristics of enrichment injection in the pre-chamber of a natural-gas engine, two-dimensional particle image velocimetry measurements and three-dimensional computational fluid dynamics calculations were carried out. The influence of the enrichment injection angle on the engine performance was investigated with the aid of a computational fluid dynamics simulation tool. The results indicate that a change in the enrichment injection angle directly affects the gas motion, the fuel–air mixture formation, the flame propagation and the formation of nitrogen oxides in the pre-chamber and further influences the penetration of the flame jets, the combustion temperature distribution and the formation of nitrogen oxides in the main chamber. There is an optimal injection angle for this research engine. Of the four injection angles that were investigated, an injection angle of 14° results in the lowest nitrogen oxide emissions.

Combustion characteristics of an SI engine fueled with biogas fuel

An experimental research of the effect of H2 substitution and CO2 dilution on CH4 combustion has been carried out on a spark ignition engine. The results show that H2 addition could improve BMEP, thermal efficiency, CO and THC emissions. NOX emissions increased for higher low heating value (LHV) of H2 than CH4. CO2 dilution could effective reduce NOX emission of H2-CH4 combustion. Although engine performance, thermal efficiency and exhaust get unacceptable under high fuel dilution ratio (F.D.R.) conditions, it could be solved by decreasing F.D.R. and/or increasing hydrogen substitution ratio (H.S.R.).

Investigation on the development and the controllability of a compact multi-functional, fully variable-valve-actuation system

A compact multi-functional, fully variable valve actuation system for six-cylinder engines was proposed. The system can run in both the drive mode and the brake mode of internal-combustion engines. With the help of a distributor, fully variable valve events were achieved with two oil-supply sets, two solenoid valves and one drain valve. The operational parameters of the valve can be adjusted independently for individual cylinders. A numerical study on the controllability of the system was carried out with AVL Hydsim. The calculation results revealed that the timing of the valve opening, the maximum lift, the duration and the time–area value can be adjusted independently or synchronously by controlling the solenoid valves and/or the drain valve. Further correlation analysis results revealed that all the operational parameters of the valve had approximately linear relationships with the corresponding control parameters, and all the correlation coefficients were larger than 0.95, indicating good controllability of the system.

Effect of Equivalence Ratio on Particle Variation of CH4 /Air Mixture of Coaxial Dielectric Barrier Discharge

The effect of equivalence ratio on particle components of dielectric barrier discharge of CH4/air mixture were carried out by employing a coaxial cylindrical electrode. The result shows that molar fraction of active particles such as H, O3, CH3 and NO decrease slightly with the equivalence ratio, however, enough active particles could be obtained even at the smallest equivalence ratio conditions; no obvious change in the electron density with the equivalence ratio has been obtained, which has a very beneficial effect on the methane-air combustion reaction under the conditions of low equivalence ratio.

Characteristic of Electron Density of Coaxial Dielectric Barrier Discharge of CH4 /Air Mixture

Numerical study of dielectric barrier discharge of CH4/air mixture were carried out by employing a coaxial cylindrical electrode with diameter of 10mm under the condition of the discharge voltage of 6000V. The influence of electrode structure parameter and equivalence ratio on electron density were analyzed. The result shows that the electron density which increases with the decrease of the distance from the cathode has a quick increase at the small position near the cathode (0.05~0.4mm), and the maximum value of electron density appears at the position of 0.1mm. The electron density has no obvious change with the equivalence ratio, it is benefit to the lean combustion of natural gas application.

Experimental Research of Impinging Spray with Basic Impinging Scheme

Visualization experimental system of impinging spray including high-pressure vessel, oil supply system, light path system, image collection and treatment system and control system was designed, and the visualization experiments of basic impinging schemes of flat wall was carried out under existing conditions without laser. The effect of impinging distance on rebounding distance and diffusing area of dripping was analyzed. The results show that both of diffusing distance along the wall and distribution area linearly increased within a certain time under the same impinging distance. Both of diffusing distance along the wall and rebounding distance decreased with the increase in impinging distance.

Structure of Swirl Chamber of Turbulent Combustion Diesel Engine

Numerical simulation was conducted on three types of swirl chamber of turbulent combustion diesel engine, i.e. cone-shaped flat-bottomed, cylindrical flat-bottomed and spherical shape. The characteristics of flow field in cylinder were studied within the time range for the piston to move from BTDC 108°CA to BTDC 8°CA (at the instant of fuel injection), thus analyzed the changes of flow field in swirl chambers of such three different structures prior to fuel injection based on the velocity vector diagram at all times and the final temperature characteristic diagram of the flow field. The results show that: in the process of piston motion, an organized fierce vortex can be developed inside the swirl chamber, while in the vicinity of fuel nozzle, the air flow rate is 111.14m/s, 83.01m/s or 175.76m/s and the air temperature is 1384.15K, 1337.38K or 1350.46K respectively. A small fluid stagnation zone will be formed in the lower right end of the cone-shaped flat-bottomed swirl chamber or the cylindrical flat-bottomed swirl chamber and is adverse to the mixing of fuel and air. In comparison with the swirl chambers of other two structures, the smaller temperature gradient of fluid and the larger high-temperature area in the cylindrical swirl chamber are beneficial to the mixing of injected fuel and air.

An Experimental Investigation on a New Combustion System of Diesel Engine for Performance Optimization

In this work, based on the concept of spray-orientation and space-atomization, a new double-layers diffluent combustion system for diesel engine is proposed which has a collision table with circular oriented-surface. Experiments are carried out on a 135 single-cylinder diesel engine by utilization of the new combustion system which is equipped with a high-pressure common-rail fuel injection system. The optimized rail pressure and fuel injection advanced angle are selected for diesel engine at different work conditions. Comparing with the data of original combustion system, the decrease of the brake specific fuel consumption and soot emission is 3.10% and 31.8% respectively while the NOX emission increased by 8.49% at rated work condition for this new combustion system. These results indicate that the new double-layers diffluent combustion system can preferably optimize the performance of diesel engine.

Combustion System Optimization of a Gasoline Direct Injection Engine

With the purpose of optimizing the combustion system of a homogeneous charged gasoline direct injection engine, its working process was simulated with a 3-D CFD software package. The authors investigated the influence of injection timings and combustion chamber shapes on the charge motion, fuel injection and their influence on fuel-air mixture formation. With the comparisons of fuel-air mixture quality and combustion processes between two typical injection timings, the optimal injection strategy was chosen. To further improve the mixture quality, configuration on piston crown was optimized and analysis on mixture formation processes of the new configurations was made. Simulation results indicate that the new configurations have faster fuel evaporation rate and better mixture homogeneity.