Effects Of Swirl Ratio Research Articles

Effect of swirl ratio on charge convection, temperature stratification, and combustion in gasoline compression ignition engine

Various low-temperature combustion strategies (namely, homogeneous charge compression ignition, reactivity controlled compression ignition, and partially premixed charge compression ignition) have shown the potential to comply with upcoming and prevailing stringent emissions legislations. Low octane gasoline has emerged as an ideal fuel candidate for premixed charge combustion under diesel-like conditions in gasoline compression ignition (GCI) engines. GCI is an excellent technology to rectify future global energy demand imbalance, because it aims to replace diesel (which is in short supply) with low octane fractions/naphtha (which is in surplus supply) in compression ignition engines. However, this novel combustion concept requires modifications in the conventional design of diesel engines. The combustion chamber shape and in-cylinder flows play a crucial role in charge distribution and temperature stratification. Therefore, understanding the combined effect of combustion chamber geometry and in-cylinder flows is essential for future engine designs. GCI combustion engine simulations for varying swirl ratios (SRs) were performed in CONVERGE CFD software to understand the effect of in-cylinder air motion on the mixture stratification and combustion. A 1/7th sector geometry for a conventional re-entry piston bowl was modeled and then simulated. Two different mechanisms were used for model validation. The results indicated that the large-scale flow structures govern the fuel distribution in the combustion chamber. The charge convection because of increased swirl has a substantial effect on the combustion characteristics of the engine. A distinguished ignition kernel was observed for all test cases. An interfacial region with counter-rotating vortices formed a lean mixture zone, hindering flame propagation and combustion. A lower SR, shallow depth piston, and modifications to avoid flame quenching in the squish zone need to be further investigated to optimize the engine performance.

A numerical investigation of isobaric combustion strategy in a compression ignition engine

Three-dimensional computational fluid dynamic simulations were conducted to study the means to achieve isobaric combustion mode in a compression ignition engine, which is intended to be used in the high-efficiency double compression-expansion engine (DCEE) concept. Compared to the conventional diesel combustion mode, the isobaric combustion mode generated a significantly lower peak combustion pressure, which was beneficial for the high load extension. For both combustion modes, the ignition was triggered downstream of the nozzle, with the heat release dominated by HCO + O2 = CO+HO2, while the injection-combustion duration for the isobaric combustion mode was significantly longer. The effects of swirl ratio, spray angle, and piston geometries on the isobaric combustion at various engine loads were also investigated. The higher swirl ratio resulted in a higher heat transfer loss and thus lower thermal efficiency. Due to the higher air utilization rates and lower heat transfer losses, cases with spray angles of 140° and 150° generated the higher thermal efficiencies. The piston bowl geometry was found to have a significant impact on the mixing and combustion processes, especially at high engine load conditions. For the conditions under study, the original piston geometry with a swirl ratio of 0 and a spray angle of 140° demonstrated the highest thermal efficiency for the isobaric combustion mode. The results of this work will provide guidance in the practical design and implementation of the DCEE concept.

Effects of the swirl ratio and spray angle on the mixture stratification in a diesel–NG RCCI engine

Reactivity Controlled Compression Ignition (RCCI) engine is the newest technology to settle the issue of excessive NOx emission of conventional diesel engines. In the present work, the effects of swirl ratio and spray angle on the performance and stratification of diesel–natural gas RCCI engines are investigated numerically. The local and global stratifications are measured by the field of equivalence ratio and its standard deviation (SD), respectively. It is concluded that the ignition delay and the location of ignition depend on the local and global stratifications controlled by the swirl ratio and spray angle. The increase in the swirl ratio increases the ignition delay by decreasing the value of equivalence ratio SD, $$ \phi $$ -SD, before ignition. On the other hand, the variation of spray angle controls the combustion duration by changing the sequence and the lag between the two ignition events happening in the bowl and squish area. Moreover, it is found that the position of the maximum stratification on $$ \phi $$ -SD curve is well correlated with CA50. Finally, the best operation is with a swirl ratio in the range 0.7–0.85 and spray angle of 145° which results in suppressed emissions and an efficiency above 50%.

Numerical Analysis of the Effects of Swirl Ratio on the Performance of Diesel Engine Fueled with N-Butanol–Diesel Blends

AbstractThe use of renewable alternative fuels in diesel engines has grown recently. In order to study the effects of different swirl ratios (SRs) on the performance of a diesel engine fueled with ...

Effect of swirl ratio on NG/diesel dual-fuel combustion at low to high engine load conditions

Recent regulation on pollutant and greenhouse gas (GHG) emissions has exerted great pressure on diesel engine industries which generate significant amount of GHG and pollutants. The concept of lean burn pilot ignited natural gas/diesel dual-fuel (NDDF) combustion is considered as one of the most suitable engine platforms to meet emissions and fuel economy regulations over a short to medium term. However, a major challenge is the slightly lower fuel efficiency and high level of methane (CH4) and carbon monoxide (CO) emissions, especially under low to medium engine load conditions. This paper numerically investigates the influence of swirl ratio on the combustion performance and emissions of a NDDF engine under low to high load conditions. The results at low load-low speed condition and retarded injection timing of 14 crank angle degrees before top dead center (BTDC) suggest that increasing swirl ratio from 0.5 to 1.5 significantly improves fuel efficiency and CH4 and CO emissions. However, under the same engine load-speed condition but at advanced injection timing of 30 crank angle degrees BTDC, increasing swirl ratio deteriorates the fuel efficiency and CH4 and CO emissions. Under a medium load-high speed condition, swirl ratio significantly improves diffusion combustion and turbulent flame propagation of natural gas. The results show that OH radical propagates more rapidly in the azimuthal direction when increasing the swirl ratio from 0.5 to 1.5. Further increase in the swirl ratio causes the peak pressure to exceed the limit (160 bar). At high load-low speed condition, increasing the swirl ratio significantly improves diesel diffusion and flame propagation of natural gas, which consequently enhances fuel efficiency. Under this engine load-speed condition, OH radical distribution shows that the combustion progresses rapidly within each jet in both the azimuthal and radial directions. Considering fuel efficiency and emissions, a swirl ratio of 1.5 is found to be the optimum. Overall, it is concluded that swirl motion may provide better mixture preparation, diesel diffusion, and natural gas flame propagation. However, this benefit may not persist under very high swirl ratio (swirl ratio > 1.5) due to higher heat losses.

Optimization of methanol powered diesel engine: A CFD approach

A two-stage strategy of emission reduction is applied to a single cylinder diesel locomotive to fulfill more stringent emission norms. First stage includes, the maximum possible emission reduction of diesel - methanol fuel through numerical simulation at low load operating condition. The higher emission reduction blend of diesel - methanol fuel is termed as ‘optimum blend’. Then, in the second stage, further emission reduction is attained by the application of three different methods of emission reduction at same operating condition. These methods are initial swirl ratio, EGR (Exhaust Gas Recirculation) and water addition. The commercially available CFD software AVL FIRE is used to perform simulation on a Kirloskar single cylinder diesel engine (model TV1). After selection of optimum blend from diesel-methanol fuel, effects of swirl ratio (1.0, 1.3, 1.6 and 2), variation in EGR percentage (10% and 20%) and effects of water addition (5%, 10% and 15%) in optimum blend is analyzed in terms of emission parameters. Furthermore, performance parameters (BSFC and BTE) are too analyzed for diesel fuel, diesel – methanol fuel and effective method from three emission reduction methods. The numerical simulation shows that, the water addition method is more efficient than the other two methods because it tends to reduce emissions effectively.

Numerical investigation of emission reduction techniques applied on methanol blended diesel engine

The present investigation works out a two-stage strategy to achieve higher level of emission reduction to meet more stringent emission norms. In the first stage, an optimum blend of diesel methanol fuel has been determined using numerical simulation to give maximum possible NOx and soot reduction. In the next stage, numerical simulation has been performed by three different methods of emission reduction namely through variation of swirl ratio, variation in quantity of recirculation of exhaust gases in Exhaust Gas Recirculation (EGR) technique and finally by means of adding water in various proportions to the same optimum diesel methanol blended fuel to obtain further reduction of emission. The numerical simulation has been performed on a single cylinder Kirloskar diesel engine (model TV1) using commercially available CFD softwareAVL FIRE. Simulation starting with the optimum diesel–methanol blend as the base fuel, effects of swirl ratio; 1.0,1.3,1.6 and 2, percentage EGR varied between 10% and 20% and addition of water to the base fuel in the ratio of 5%, 10% and 15% by volume on emission are analyzed. Results indicate that water blend method tends to reduce NOx emission by 95% and soot by 14% with respect to emissions of base fuel.

Characterization of the effect of intake air swirl motion on time-resolved in-cylinder flow field using quadruple proper orthogonal decomposition

The control of intake air swirl motion is often used in spark-ignition direct-injection (SIDI) engine to improve its in-cylinder fuel–air mixing process especially under engine idle and low load conditions. In this experimental investigation, a novel technique combining the time-resolved particle image velocimetry (PIV) with quadruple proper orthogonal decomposition (POD) is implemented to analyze the time-resolved in-cylinder velocity measurements in an optically-accessible SIDI engine. The intake air swirl motion is introduced into the engine cylinder by a control valve installed in one of two air intake ports. Experimental results show that a strong linear correlation exists between the intake flow swirl ratio and vorticity flow field in the cylinder. This correlation ensures high data reliability of swirl motion control and provides a novel basis to directly compare the flow field measurements under different swirl ratio conditions. The quadruple proper orthogonal decomposition analysis is then applied to the velocity flow fields to separate the highly dynamic in-cylinder flow characteristics into four distinct categories: (1) dominant flow structure; (2) coherent structure; (3) turbulent structure; and (4) noise structure. The results show that the dominant flow structure varies strongly with swirl ratio, and its kinetic energy is also directly related to the swirl ratio. The coherent structure captures the large scale flow characteristics, but its kinetic energy is much lower and exhibits larger cycle-to-cycle variations. The turbulent structure contains similar level of kinetic energy at different swirl ratios but without much cycle-to-cycle variation. Finally, the noise structure contains very low kinetic energy which only alters the dynamic nature of the flow field slightly. In summary, the effect of swirl ratio on in-cylinder flow field is mostly captured by the dominant flow structure and partially captured by the coherent flow structure. The turbulent flow structure can characterize the high-order flow variation. The noise structure can be neglected due to the low energy captured.

Experimental study of wind pressures acting on a cooling tower exposed to stationary tornado-like vortices

Wind pressures acting on a cooling tower exposed to stationary tornado-like vortices are studied physically. This study focuses on the effects of swirl ratio and the distance between a cooling tower and a stationary tornado vortex on the pressure distribution around a cooling tower. Particular attention is devoted to the differences of pressure distribution and cross-correlation coefficients of pressures in a tornado with that in a conventional boundary-layer-type straight-line wind. The results show that a cooling tower exposed to a tornado experiences combined effects of pressure drop accompanying a tornado and aerodynamic flow-structure interaction. The pressure drop accompanying a tornado dominates the pressure coefficient magnitudes when the cooling tower is located at the tornado core center. The cooling tower experiences maximum wind force when it is located at the tornado core radius. Results show that the tornado-induced wind pressure is significantly different than that in conventional straight-line winds, and highlight the need to study tornado-induced wind loads on structures.

Numerical Investigations of Spray Droplet Parameters in a Direct Injection Diesel Engine Using 3-Z Extended Coherent Flame Model

Diesel engine combustion modeling presents a challenging task as the injection starts with the spray formation and breakup of spray into droplets. The computation involved in predicting the in-cylinder fluid mixture during combustion using eulerian and lagrangian approach is rather a cumbersome task. In this work, 3D-CFD computations are performed to understand the behaviour of spray droplet variables on combustion process and emissions in a direct injection diesel engine. The study involves the computation of turbulent flow-field quantities, modelling various processes such as fuel spray distribution, atomization, collision, evaporation, combustion and pollutant formation using a commercial CFD code. Grid independence and time independent studies are carried out for finding the optimum grid size and time step. The numerical results predicted using CFD code is validated with the experimental data available from the literature. The process of combustion and emission characteristics is investigated numerically with respect to spray characteristics. The work is further extended to study the effect of swirl ratio and injection timing on droplet parameters.

Effect of Swirl Ratio and Wall Temperature on Pre-lnjection Chemiluminescence During Starting of an Optical Diesel Engine

Effect of Swirl Ratio and Wall Temperature on Pre-lnjection Chemiluminescence During Starting of an Optical Diesel Engine

Combustion in High-Speed Direct Injection Diesel Engines—A Comprehensive Study

This paper reports the latest results of a comprehensive project investigating the performance of a Ricardo Hydra direct injection diesel engine. Early work covered a number of aspects of research into the gross behaviour of this engine: this paper concentrates on techniques for obtaining quantitative data from photographs of the combustion process. High-speed photographs, at framing rates up to 20 000 frames/s, were taken using a piston with a quartz bowl, at engine speeds up to 3000 r/min. The pre-combustion period was illuminated using a synchronized copper vapour laser. After the initiation of combustion, the process is self-illuminating and information on the combustion process was obtained by analysing the radiation emitted by the carbon particles. The two-colour method was used to evaluate the temperature of the combustion gases over the full field of view. The images have also been analysed by a cross-correlation technique to obtain velocity information. Tests have been performed on the engine over a wide range of operating conditions, but this paper concentrates on the effect of swirl ratio on combustion. It will be shown that too much swirl increases the ignition delay period and results in an increase in the NOx emissions but a decrease in the soot. It will also be shown that the velocity pattern after combustion is in good agreement with that evaluated by Arcoumanis et al. at the end of compression, which implies that swirl persists through the combustion period despite significant decay.

Combustion of a Diesel Engine with the M-combustion System : Effects of Swirl Ratio and Surface Temperature of Combustion Chamber

This paper gives the experimental results obtained with a two-stroke cycle single-cylinder research engine using an electrically heated combustion chamber to simulate the combustion chamber of a low-heat-rejection(LHR) DI diesel engine with the M-combustion system. In this report, the experiment was performed to investigate the influences of combustion chamber surface temperature and swirl ratio on the combustion of a LHR DI diesel engine with the M-conbustion system. It is found that the combustion of fuel deposited on the surface is greatly affected by the combustion chamber surface temperature, and the diesel combustion is controlled by the swirl and the surface temperature of the combustion chamber.

Combustion of a diesel engine with the M-combustion system. Effects of swirl ratio and surface temperature of combustion chamber.

This paper gives the experimental results obtained with a two-stroke cycle single-cylinder research engine using an electrically heated combustion chamber to simulate the combustion chamber of a low-heat-rejection (LHR) DI diesel engine with an M-combustion system. In this report, the experiment was performed to investigate the influences of combustion chamber surface temperature and swirl ratio on the combustion of an LHR DI diesel engine with an M-combustion system. It is found that the combustion of deposited fuel on the surface is greatly affected by the combustion chamber surface temperature, and the diesel combustion is controlled by the swirl and the surface temperature of the combustion chamber.