Four Stroke Engine Geometry for Stratified Charge Combustion

2005 ◽  
Author(s):  
E. Musu ◽  
S. Zanforlin ◽  
R. Gentili
Keyword(s):  
Combustion Chamber ◽  
Numerical Study ◽  
Direct Injection ◽  
Combustion Efficiency ◽  
Loss Reduction ◽  
Stratified Charge ◽  
Conventional Combustion ◽  
Gas Expansion ◽  
Partial Loads ◽  
Stroke Engine

In four-stroke engines direct injection increases power and fuel economy, which is further improved by charge stratification, due to pumping loss reduction and better combustion efficiency at partial loads. Charge stratification can be obtained by different techniques and injector designs. In every case late injection is necessary for stratification, which however is impaired by fuel dilution and spreading in consequence of burnt gas expansion, leading to incomplete combustion at very light loads. A numerical study has been carried out modifying KIVA code to handle new piston shapes. An innovative combustion chamber that is split in two volumes and allows fuel confinement during combustion has been conceived. CFD comparison has been made between a conventional combustion chamber and the proposed new one in term of combustion efficiency. Combustion is enhanced by the new design and unburnt emissions are reduced.

scholarly journals Combustion Thermodynamics of Ethanol, n-Heptane, and n-Butanol in a Rapid Compression Machine with a Dual Direct Injection (DDI) Supply System

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2729
Author(s):  
Ireneusz Pielecha ◽  
Sławomir Wierzbicki ◽  
Maciej Sidorowicz ◽  
Dariusz Pietras
Keyword(s):  
Heat Release ◽  
Combustion Chamber ◽  
Internal Combustion Engines ◽  
Direct Injection ◽  
Combustion Process ◽  
Combustion Efficiency ◽  
Injection System ◽  
Rapid Compression Machine ◽  
Process Indicators ◽  
Rapid Compression

The development of internal combustion engines involves various new solutions, one of which is the use of dual-fuel systems. The diversity of technological solutions being developed determines the efficiency of such systems, as well as the possibility of reducing the emission of carbon dioxide and exhaust components into the atmosphere. An innovative double direct injection system was used as a method for forming a mixture in the combustion chamber. The tests were carried out with the use of gasoline, ethanol, n-heptane, and n-butanol during combustion in a model test engine—the rapid compression machine (RCM). The analyzed combustion process indicators included the cylinder pressure, pressure increase rate, heat release rate, and heat release value. Optical tests of the combustion process made it possible to analyze the flame development in the observed area of the combustion chamber. The conducted research and analyses resulted in the observation that it is possible to control the excess air ratio in the direct vicinity of the spark plug just before ignition. Such possibilities occur as a result of the properties of the injected fuels, which include different amounts of air required for their stoichiometric combustion. The studies of the combustion process have shown that the combustible mixtures consisting of gasoline with another fuel are characterized by greater combustion efficiency than the mixtures composed of only a single fuel type, and that the influence of the type of fuel used is significant for the combustion process and its indicator values.

Numerical Study to Achieve Stratified EGR in Engines

2002 ◽  
Author(s):  
Bassem H. Ramadan ◽  
Charles L. Gray ◽  
Harold J. Schock ◽  
Fakhri J. Hamady ◽  
Karl H. Hellman
Keyword(s):  
Numerical Study ◽  
Direct Injection ◽  
Fuel Mixture ◽  
Combustion Engines ◽  
Lean Burn ◽  
Complete Combustion ◽  
Stratified Charge ◽  
Automotive Emissions ◽  
Si Engines ◽  
Inlet Manifold

Exhaust Gas Re-circulation (EGR) has been used in intemal combustion engines to control automotive emissions. EGR is usually used to dilute the inlet charge, which consists of air, by redirecting part of the exhaust into the inlet manifold of the engine. This results in a reduction of the oxygen mass fraction in the inlet charge. However, dilution of the air-fuel mixture in an engine using stratified EGR could offer significant fuel economy saving comparable to lean burn or stratified charge direct-injection SI engines. The most critical challenge is to keep the EGR and air-fuel mixture separated, or to minimize the mixing between the two zones to an acceptable level for stable and complete combustion. Swirl-type stratified EGR and fuel-air flow structure is considered desirable for this purpose, because the circular shape of the cylinder tends to preserve the swirl motion. Moreover, the axial piston motion has minimal effect on the swirling motion of the fluid in the cylinder. In this study, we consider intake system design in order to generate a two-zone combustion system, where EGR is maintained in a layer on the periphery of the cylinder, and the fuel-air mixture is maintained in the center of the cylinder. KIVA-3V was used to perform numerical simulations on different EGR systems. The simulations were performed to determine if the two-zones can be generated in the cylinder, and to what extent mixing between the two zones occurs. For the engine geometries considered in this study, the results showed that it is possible to generate the two zones, but mixing is difficult to control.

Effect of Injection Timing on Fuel-Air Mixing and Combustion in a Direct Injection Stratified Charge SI Engine

2007 ◽  
Author(s):  
T. Anand Kumar ◽  
J. M. Mallikarjuna ◽  
V. Ganesan
Keyword(s):  
Numerical Study ◽  
Direct Injection ◽  
Combustion Characteristics ◽  
Spark Ignition Engine ◽  
Injection Timing ◽  
Flame Surface ◽  
Si Engine ◽  
Stratified Charge ◽  
Spark Plug ◽  
Air Mixing

This paper describes a numerical study on fuel-air mixing and combustion in a direct injection stratified charge spark ignition engine. The in-cylinder flow, fuel-air mixing and combustion characteristics are investigated in a single cylinder, four-valve, four stoke, direct injection SI engine with pent-roof head and reverse tumble ports. The engine combustion chamber had the side mounted injector and spark plug at the center of pent-roof. Wall guided fuel-air mixing scheme has been adopted. The pre processor code Es-ice, used for dynamic grid generation preparation including description of piston and valve motion. Commercial computational fluid dynamics code Star-CD is used for solving governing equations and post processing of results. Combustion in the present study is simulated using Extended Coherent Flame Model-3z (ECFM-3Z). This model is based on a flame surface density transport equation that can describe inhomogeneous turbulent premixed combustion. In the present study, engine simulations has been carried out from 370 CAD before TDC and upto 90 CAD aTDC. The process includes the closing of the exhaust valves, the whole intake stroke, injection, combustion, and part of expansion. Three different injection timings are simulated viz. 55, 60 and 65 CAD bTDC. For validation of the code predicted results are compared with experimental results available in the literature. It is observed that, injection timing has an important role in mixture preparation and distribution around the spark plug. Hence, for the better combustion characteristics start of injection timing should be optimized.

Flow Dynamics of Charge Stratification in Small GDI Two-Stroke Engines

2002 ◽  
Author(s):  
Stefania Zanforlin ◽  
Roberto Gentili ◽  
Pierluigi Dell’Orto
Keyword(s):  
High Pressure ◽  
Combustion Chamber ◽  
Liquid Fuel ◽  
Fuel Injection ◽  
Flow Dynamics ◽  
Mixing Process ◽  
Stratified Charge ◽  
Fuel Distribution ◽  
Multidimensional Modelling ◽  
Partial Loads

Direct high-pressure liquid fuel injection is able to control the mixing process inside the cylinder for getting either stratified charge at partial loads or quasi-homogeneous conditions, as it is required at full load. This paper shows the development of this solution for small two-stoke engines, using multidimensional modelling. The aim is investigating how the design of scavenging ducts and combustion chamber influences charge stratification behaviour, taking into account fuel distribution and stratification stability varying engine load and speed.

Modeling and Experiment on Combustion Characteristics for Biomass Rotary Burner

2020 ◽  
Vol 04 ◽  
Author(s):  
Guohai Jia ◽  
Lijun Li ◽  
Li Dai ◽  
Zicheng Gao ◽  
Jiping Li
Keyword(s):  
Combustion Chamber ◽  
Combustion Temperature ◽  
Combustion Efficiency ◽  
Middle Part ◽  
Combustion Characteristics ◽  
Maximum Temperature ◽  
Excess Air ◽  
Element Simulation ◽  
Excess Air Coefficient ◽  
Secondary Air

Background: A biomass pellet rotary burner was chosen as the research object in order to study the influence of excess air coefficient on the combustion efficiency. The finite element simulation model of biomass rotary burner was established. Methods: The computational fluid dynamics software was applied to simulate the combustion characteristics of biomass rotary burner in steady condition and the effects of excess air ratio on pressure field, velocity field and temperature field was analyzed. Results: The results show that the flow velocity inside the burner gradually increases with the increase of inlet velocity and the maximum combustion temperature is also appeared in the middle part of the combustion chamber. Conclusion: When the excess air coefficient is 1.0 with the secondary air outlet velocity of 4.16 m/s, the maximum temperature of the rotary combustion chamber is 2730K with the secondary air outlet velocity of 6.66 m/s. When the excess air ratio is 1.6, the maximum temperature of the rotary combustion chamber is 2410K. When the air ratio is 2.4, the maximum temperature of the rotary combustion chamber is 2340K with the secondary air outlet velocity of 9.99 m/s. The best excess air coefficient is 1.0. The experimental value of combustion temperature of biomass rotary burner is in good agreement with the simulation results.

Prediction of gaseous pollutant emissions from a spark-ignition direct-injection engine with gas-exchange simulation

2021 ◽  
pp. 146808742110050
Author(s):  
Stefania Esposito ◽  
Lutz Diekhoff ◽  
Stefan Pischinger
Keyword(s):  
Gas Exchange ◽  
Combustion Chamber ◽  
Direct Injection ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Operating Parameters ◽  
Gaseous Pollutant ◽  
Fuel Ratio ◽  
No Emissions

With the further tightening of emission regulations and the introduction of real driving emission tests (RDE), the simulative prediction of emissions is becoming increasingly important for the development of future low-emission internal combustion engines. In this context, gas-exchange simulation can be used as a powerful tool for the evaluation of new design concepts. However, the simplified description of the combustion chamber can make the prediction of complex in-cylinder phenomena like emission formation quite challenging. The present work focuses on the prediction of gaseous pollutants from a spark-ignition (SI) direct injection (DI) engine with 1D–0D gas-exchange simulations. The accuracy of the simulative prediction regarding gaseous pollutant emissions is assessed based on the comparison with measurement data obtained with a research single cylinder engine (SCE). Multiple variations of engine operating parameters – for example, load, speed, air-to-fuel ratio, valve timing – are taken into account to verify the predictivity of the simulation toward changing engine operating conditions. Regarding the unburned hydrocarbon (HC) emissions, phenomenological models are used to estimate the contribution of the piston top-land crevice as well as flame wall-quenching and oil-film fuel adsorption-desorption mechanisms. Regarding CO and NO emissions, multiple approaches to describe the burned zone kinetics in combination with a two-zone 0D combustion chamber model are evaluated. In particular, calculations with reduced reaction kinetics are compared with simplified kinetic descriptions. At engine warm operation, the HC models show an accuracy mainly within 20%. The predictions for the NO emissions follow the trend of the measurements with changing engine operating parameters and all modeled results are mainly within ±20%. Regarding CO emissions, the simplified kinetic models are not capable to predict CO at stoichiometric conditions with errors below 30%. With the usage of a reduced kinetic mechanism, a better prediction capability of CO at stoichiometric air-to-fuel ratio could be achieved.

A comparative numerical study of the combustion performance of the syngas-fueled HCCI engine using a toroidal piston, square bowl piston, and flat piston shape at different loads

2021 ◽  
pp. 1-27
Author(s):  
Kabbir Ali ◽  
Changup Kim ◽  
Yonggyu Lee ◽  
Seungmook Oh ◽  
Ki-Seong Kim
Keyword(s):  
Numerical Study ◽  
Pressure Rise ◽  
Fuel Mixture ◽  
Combustion Efficiency ◽  
Maximum Pressure ◽  
Cross Sectional ◽  
Combustion Performance ◽  
Hcci Engine ◽  
Heat Loss Rate ◽  
Piston Bowl

Abstract This study analyzes the combustion performance of a syngas-fueled homogenous charge compression ignition (HCCI) engine using a toroidal piston, square bowl, and flat piston shape, at low, medium, and high loads, with a constant compression ratio of 17.1. In this study, the square bowl shape is optimized by reducing the piston bowl depth and squish area ratio (squish area/cylinder cross-sectional area) from (34 to 20, 10, and 2.5) %, and compared with the flat piston shape and toroidal piston shape. This HCCI engine operates under an overly lean air–fuel mixture condition for power plant usage. ANSYS Forte CFD with GRI Mech3.0 chemical kinetics is used for combustion analysis, and the calculated results are validated by the experimental results. All simulations are accomplished at maximum brake torque (MBT) by altering the air–fuel mixture temperature at IVC with a constant equivalence ratio of 0.27. This study reveals that the main factors that affect the start of combustion , maximum pressure rise rate (MPRR), combustion efficiency, and thermal efficiency by changing the piston shape are the squish flow and reverse squish flow effects. Therefore, the square bowl piston D is the optimized piston shape that offers low MPRR and high combustion performance for the syngas-fueled HCCI engine, due to the weak squish flow and low heat loss rate through the combustion chamber wall, respectively, compared to the other piston shapes of square bowl piston A, B, and C, flat piston, and toroidal (baseline) piston shape.

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