Modified Combustion Chamber Research Articles

Advanced Numerical Analysis of In-Cylinder Combustion and NOx Formation Using Different Chamber Geometries

In diesel engines, emission formation inside the combustion chamber is a complex phenomenon. The combustion events inside the chamber occur in microseconds, affecting the overall engine performance and emissions characteristics. This study opted for using computational fluid dynamics (CFD) to investigate the combustion patterns and how these events affect nitrogen oxide (NOx) emissions. In this study, a diesel engine model with a flat combustion chamber (FCC) was developed for the simulation. The simulation result of the heat release rate (HRR) and cylinder pressure was validated with the experimental test data (the engine test was conducted at 1500 rpm at full load conditions). The validated model and its respective boundary conditions were used to investigate the effect of modified combustion chamber profiles on NOx emissions. Modified chambers, such as a bathtub combustion chamber (BTCC) and a shallow depth chamber (SCC), were developed, and their combustion events were analysed with respect to the FCC. This study revealed that combustion events such as fuel distribution, unburnt mass fractions, temperature and turbulent zones directly impact NOx emissions. The modified chambers controlled the spread of combustion and provided better fuel distribution, improving engine performance and combustion rates. The SCC (63.2 bar) showed peak pressure rates compared to the FCC (63.02 bar) and BTCC (62.72 bar). This study concluded that the SCC showed better results than other chambers. This study further recommends conducting lean fuel mixture combustion with chamber modifications and optimising fuel spray, such as by adjusting the fuel injection profile, spray angle and injection timing, which has a better tendency to create complete combustion.

Effect of piston geometry on combustion characteristics of CI engine used Sal seed oil

The effect of piston bowl geometry on reducing soot emissions, improving combustion, and in-cylinder flow movements in a direct injection diesel engine was investigated. Standard combustion chamber (SCC) and newly modified combustion chamber (MCC) geometries were compared at the same compression ratio (17.5:1). Experimental analysis of diesel engines is expensive and time consuming, and therefore the Computational Fluid Dynamics program was used to analyze the combustion, flow and emission process. AVL Fire ESE Diesel software was used in the numerical study. The numerical work was compared with the experimental results, and it was validated. In addition, 10% biodiesel mixture (10% Sal seed oil methyl ester + 90% diesel fuel) and diesel fuel were used in the analysis. These fuels and two different bowl geometries were investigated at 2000 rpm and full load conditions. Thus, the effect of the used biodiesel fuel and the developed bowl geometry were investigated. Sal seed oil methyl ester was used as biodiesel fuel. The results show that higher turbulence velocity distribution, better mixture fraction values and lower soot formation distribution are obtained by directing the MCC type fuel according to SCC type. When the pressure, temperature and heat release in the combustion chamber are examined, the highest values were obtained with B10 blended fuel used at the SCC type combustion chamber. The maximum heat release rates are 8.72, 9.38, 8.21, and 9.30 J/° for SCCD100, SCCB10, MCCD100 and MCCB10 fuels, respectively.

Effect of modified combustion chamber configuration and enhanced squish flow on improving thermal efficiency in jet-plume-controlled direct-injection near-zero emission hydrogen engines

In direct injection hydrogen engines, the Plume Ignition and Combustion Concept (PCC) developed by the authors has been applied to improve thermal efficiency and reduce NOx emissions under high-load operation. The PCC combustion method burns an optimized hydrogen jet plume that is ignited immediately upon completion of injection in the latter half of the compression stroke. In addition to optimizing the hydrogen jet configuration, this basic combustion concept was applied to burn a lean mixture and supercharging was used to recover the decline in power output due to combustion of a diluted mixture. As a result, a near-zero emission engine has been achieved that simultaneously provides high thermal efficiency, high power output and low NOx emissions at a single-digit ppm level. Various techniques have been applied to improve thermal efficiency further and achieve much lower NOx emissions close to a zero-emission target. These included the adoption of a re-entrant combustion chamber to reduce unburned hydrogen emissions, enhanced squish flow to promote better mixing of air and the hydrogen jet injected into the combustion chamber, and a narrower nozzle hole diameter to promote entrainment of air into the hydrogen jet. In this study, the effect of each of these measures was made clear experimentally and by analysis. This paper presents the results obtained.

Heat and Flow Analysis of Different Piston Bowl Geometries in a Diesel Engine

In this study, heat and flow in a four cylinder direct injection diesel engine combustion chamber has been simulated by using AVL Fire ESE Diesel. In order to clarify the effect of the combustion chamber geometry on the flow area prop-erties, the bowl geometric shape of two different pistons, one of the combustion chamber as a standard, was taken into account in the flow analysis. Standard combustion chamber and modified combustion chamber geometries have been compared. The simulation results showed that the bowl shapes of the combustion chambers are quite effective on temperature-spray droplet distribution, turbu-lence kinetic energy distributions, turbulence velocity distributions and laminar flame speed distributions at the end of the compression stroke. The fuel reaches the cylinder wall more easily and then, the temperature distribution in the cham-ber is lower as a result of evaporation of the fuel with modified combustion chamber. Average turbulent kinetic energy value in the MCC type combustion chamber is 10.53 m²/s², in the standard combustion chamber type combustion chamber this value is 8.35 m²/s² at 720° CA. Turbulence velocity distribution is spread over a wider area in the modified combustion chamber geometry. As a re-sult of the large area of turbulence, the laminar flame velocity has also increased in this chamber geometry.

Numerical investigation on performance of convergent–divergent nozzle with multi‐inlet combustion chamber of a rocket engine

AbstractIn the present work, a convergent–divergent nozzle with a multi‐inlet combustion chamber of a rocket engine is numerically investigated to precisely understand the flow dynamics and variation of flow properties like pressure, temperature, and velocity distribution. The work also deals with a modified combustion chamber having multiple inlets. According to the entry conditions, when the propellants enter the combustion chamber, they are burning due to high velocity and temperature. Then there is a rapid increase in temperature and pressure in the combustion chamber, and afterward, they decrease over the nozzle's length. In this study, three configurations have been prepared in the design modular of ANSYS, a combined setup of the convergent–divergent nozzle with a combustion chamber with four inlets, six inlets, and one with increased combustion chamber length called a modified combustion chamber configuration. In this analysis, an investigation is performed to see the effect of multi‐inlet and increased length of the combustion chamber on the convergent–divergent nozzle's exit velocity. The results show that the configuration with six inlets modified combustion chamber has a 26.3% increase in velocity than six inlets and 38.6% higher exit velocity than four inlets convergent–divergent nozzle of the rocket engine.

Effect of Modified Combustion Chamber on Performance Characteristics by using Blends of Simarouba Biodiesel

This work aims to study combustion chamber geometry on combustion, performance and emissions of a biodiesel (Simarouba) fuelled modified piston diesel engine. In the existing consequence, biodiesels have established a lot of consideration as an alternate fuel for internal combustion engines. In accumulation, the biodiesels have poor atomization individualities due to diminished CA at the time of fuel injection. However, biodiesel properties are not similar to conventional CI engine fuels, predominantly their higher value of viscosity and lower volatility. This paper emphasizes adapting the internal burning engine combustion chamber structure to promote whirl to better the mixture burning. An assessment of works indicates that investigational studies have not accompanied a specially modified piston for appraising at a constant speed of 1500 revolutions per minute and a compression ratio (CR) of 17.50 at different injection pressure (IP) and different injection timing too. The performance considerations viz... Specific fuel consumption (SFC), brake thermal eff. (BTH), carbon monoxide (CO), oxides of nitrogen (NOx) and unburnt hydrocarbons have been studied. This effort aims to analyze the effect of cylinder structure on burning and exhaust gas emissions of a biodiesel (Simorouba) fuelled specially modified piston conventional diesel engine. It is observed that the IC engine with personalized piston contributes to optimal performance. This exertion is to overview the effect of the specially modified piston on burning, performance parameters and engine exhaust emissions of a biodiesel (Simorouba) fuelled specially modified piston conventional diesel engine. The internal combustion engine under contemplation with specially modified piston gives optimal performance for the internal combustion engine. It has been noticed that the engine under consideration with threaded piston gives optimum performance.

Analysis of different combustion chamber geometries using hydrogen / diesel fuel in a diesel engine

ABSTRACT In this study, the effects on combustion characteristics and emission were investigated in a direct injection diesel engine. In experimental and numerical studies, the engine was operated at 2000 rpm. The analyzes were made in the AVL-FIRE ESE Diesel part with Computational Fluid Dynamics (CFD) software. Standard combustion chamber (SCC) and Modified combustion chamber (MCC) geometry were compared in the modeling. By means of the designed MCC combustion chamber geometry, the fuel released from the injector was directed to the piston bowl area. Therefore, the mixture was homogenized and the combustion had been improved. In addition, the evaporation rate of the mixture increased with the MCC geometry. Also, lower NO and CO emissions were obtained with the MCC model compared to the SCC model. On the other hand, diesel fuel and mass 5% hydrogen fuel was used into diesel fuel as fuel in the study. The combustion process was investigated using hydrogen in different combustion chambers. The use of hydrogen as additional fuel resulted in higher combustion pressure, temperature and NO emissions. Compared to SCC type combustion chamber in the MCC type combustion chamber used diesel fuel, CO emission decreased of 6% and 3% for hydrogen-added mixture fuel. Also, compared to SCC type combustion chamber in the MCC type combustion chamber used diesel fuel, NO emission decreased of 11% and 32% for hydrogen-added mixture fuel. Moreover, flame velocity, heat release rate and flame propagation increased with the addition of hydrogen fuel.

Effect of EGR on emissions of a modified DI compression ignition engine energized with nanoemulsive blends of grapeseed biodiesel

This research work investigates the effect of Exhaust Gas Recirculation (EGR) in a CI engine fueled with Grapeseed oil biodiesel derived from winery biomass waste. As the brake thermal efficiency of any biodiesel are generally lesser compared to diesel, fuel modification and design changes in combustion chamber geometry are made to improve the thermal efficiency. The above strategy not only decrease fuel consumption, but also reduces the engine emissions like HC, CO and NO. To further reduce NO emission that is formed due to high combustion pressure and temperature, EGR technique is used at four different rates, 5%, 10%, 15% and 20% and the optimum rate is decided based on NO soot tradeoff. Engine tests were conducted at various loads to study the performance of nanoemulsive grapeseed biodiesel with modified combustion chamber shape. NO emissions were noticed to increase at high loads. Nano blends of grapeseed oil biodiesel injected at 23°bTDC at 5% EGR rate was found to reduce NO emissions from 8.07 g/kWh to 5.5 g/kWh with a slight compromise in smoke. UBHC and BSCO emissions were reasonably reduced at this EGR rate by 20.7% and 6.2% compared to diesel. The novel finding of this investigation is that biomass derived from winery waste could be a viable fuel for CI engines with suitable engine modifications.

Numerical Simulations of Rich Burn Quick Mix Lean Combustor

Objectives: This paper aims to present a summary of Nitrogen oxide formation in designed Rich Burn Quick Mix Lean Burn Gas Turbine Combustor. The combustor uses Hydrogen as a fuel and designed for 20 kW power output. Methods/Statistical Analysis: The numerical study has been carried out for designed combustion chamber by using Modified O’Conaire Mechanism. The output of numerical study concludes that the design combustion chamber has high velocities of the order of 600m/s in the quick mix zone which in turns suggest very high pressure drop. The highpressure drop is not advisable for gas turbine engine. The modifications in quick mix zone are redesigned to reduce the velocities and in turn reduce pressure drop. Redesign of quick mix zone is carried out providing diffuser at the exit of quick mix zone. The redesigned combustor is numerically simulated at different overall equivalence ratio. Findings: The results suggest low velocity levels in the rich zone leading to better mixing of fuel and air streams, near uniform temperature distribution in annulus liner, flame blow out in quick mix zone, and stable combustion in lean zone. Application/Improvements: Modified Combustion chamber was numerically tested for different altitude condition and different equivalence ratio for stable operation during real life condition. Keywords: Equivalence Ratio, NOx, Numerical Simulations, RQL

Multi-Dimensional Modeling of the Effects of Air Jet and Split Injection on Combustion and Emission of DirectInjection Diesel Engine

One of the most important problems in reducing the emissions of diesel engines is to exchange between the oxides of nitrogen and soot emissions. Fuel multiple injection and air injection into combustion chamber are among the most powerful tools to concurrent reduction of these two emissions. In this research, the effect of multiple injection and air injection on combustion and emission parameters has been studied by AVL fire computational fluid dynamic software. Six states of base and modified combustion chamber have been studied in two different injection patterns including 90 (25) 10 and 75 (25) 25 mods. Results show that concurrent applying of both multiple injection and air injection methods has resulted in simultaneous reduction of oxide nitrogen and soot pollutants and a negligible loss is seen in the operational parameters of engine. Compression between six studied cases show that the 90 (25) 10 mode of injection with modified combustion chamber is the optimum mode by decreasing of soot and oxides of nitrogen emissions about 29% and 20% respectively and 6% indicated power loss in compression to the base combustion chamber and single injection mode. The obtained results from the computational fluid dynamic code have been compared with the existing results in the technical literature and show acceptable behavior.

Experimental Studies on Diesel Engine with Piston Crown Modification Using an Optimum Alternative Fuel

The drawbacks associated with bio-fuels can be minimized by making modifications to combustion chamber. Modification of combustion chamber is achieved by providing an air gap in between the crown and the body of the piston with the top crown made of low thermal conductivity material. Experimentation is carried on a diesel engine with brass as piston crown material and karanja as test fuel, which is found to be a better alternative fuel based on the tests carried out prior to modification. Investigations are carried out on the performance of the engine with modified combustion chamber consisting of air gap insulated piston with 2 mm air gap with brass crown when fuelled with karanja oil. Comparative studies are made between the two configurations of engine with and without modification at an injection timing of 29o bTDC. Performance, heat balance and emission plots are made with respect to brake power. Fuel consumption increased with modification. The mechanical and volumetric efficiencies are similar in both the cases. Indicated and brake thermal efficiencies got reduced with modification. But, it is good to see that HC and CO emissions are showing positive trend. Thus, the present investigation hints the possibility of improvements while making piston modification and providing air gap insulation.

Comparison study on combustion characteristics and emissions of a homogeneous charge compression ignition (HCCI) engine with and without pre-combustion chamber

There is an urgent need to develop new combustion strategies such as homogeneous charge compression ignition (HCCI) mode to meet current and future emissions regulations. In this study, experiments and a coupled AVL-CHEMKIN CFD (computational fluid dynamic) model were adopted to compare combustion phasing, engine performance and emissions in term of equivalence ratio for both HCCI combustion engines with and without pre-combustion chamber to investigate the effect of pre-combustion chamber on HCCI combustion engine. Results revealed that with an equivalence ratio of 0.2, HCCI engine with pre-combustion chamber (comet MK.V) tolerates misfiring process, while HCCI engine without pre-combustion chamber (modified chamber) experiences a complete combustion. HCCI engine with modified chamber has higher combustion pressure, narrower heat release rate (HRR), more advanced start of combustion (SOC) and higher indicated mean effective pressure (IMEP) in comparison with comet MK.V chamber. For equivalence ratios between 0.2 and 0.5, the average increase in IMEPs is 49.3%. Furthermore, HCCI engine with modified chamber generates higher work per kg fuel compared to comet MK.V chamber. While a high level of nitrogen oxide (NOx) emissions is produced by HCCI combustion with modified chamber, both carbon monoxide (CO) and hydrocarbon (HC) emissions decreased drastically. In terms of combustion phasing, engine performance and emissions, the HCCI engine with modified combustion chamber is preferred at low equivalence ratios (Φ<0.3) compared with comet MK.V chamber.

Effect of Combustion Chamber Geometry on Performance and Emission Characteristics of a Diesel Engine Fueled with Mahua Biodiesel Blends

The present work investigates the effect of change in combustion chamber geometry on performance and emission characteristics of single cylinder diesel engine fuelled with mahua biodiesel. Since plant oil derived from the mahua tree has high fatty acids, it undergoes esterification followed by transesterification process to reduce its viscosity. Experiments were conducted using a blend of 20% biodiesel (B20) 40% biodiesel (B40) with diesel and compared with diesel by using two types of combustion chamber geometry, explicitly hemispherical and modified hemispherical combustion chamber. Performance parameters such as Brake Thermal Efficiency (BTE), Brake Specific Fuel Consumption (BSFC) and emission parameters like Unburned Hydro Carbon (UBHC), Oxides of Nitrogen (NOx) were studied from the diesel engine with above mentioned configurations. It is obvious that there is considerable improvement in the performance parameter viz, BTE, BSFC and reduction in UBHC emissions by using the modified geometry piston. However, the NOx emission was found to be higher than that of standard configuration. The results obtained from the blend B20 at modified combustion chamber geometry are on par with diesel and hence mahua biodiesel can be suggested as an alternative fuel for Compression Ignition (C.I) engine with modified combustion chamber geometry.

Optimizing the design of a hydrogen engine with pilot diesel fuel ignition

A diesel engine was converted to dual–fuel hydrogen operation, ignition being started by a 'pilot' quantity of diesel fuel but with 65 to 90% of the energy being supplied as hydrogen. With later injection timing, use of delayed port admission of the gas, and a modified combustion chamber, thermal efficiencies were achieved nearly 15% greater than those for diesel as the sole fuel. A 'solid' water injection technique was used to curb knock under full load conditions when the power output equalled or exceeded that of a similar diesel engine. The indicator diagrams under these conditions closely approach those of the Otto cycle. The development was assisted by computer simulation using a novel self–ignition and flame propagation model. The very fast burning rates obtained with stoichiometric hydrogen–air mixtures show combustion to occur within 5 degrees of crank rotation yet Otto cycle thermal efficiency was not achieved. However, greenhouse gases are shown to be reduced by more than 80%, nitrogen oxides by up to 70%, and exhaust smoke by nearly 80%.

Low polluting, energy efficient C.I. hydrogen engine

A diesel engine was converted to dual-fuel hydrogen operation, ignition being started by a ‘pilot’ quantity of diesel fuel, but 65–90% of the energy was supplied as hydrogen. Delayed port admission of the gas, later injection timing and a modified combustion chamber allowed 15% increase in efficiency. A ‘solid’ water injection technique was employed to curb knock under full load conditions when the power output equalled or exceeded that of the engine with diesel fuel alone. The indicator diagrams under these conditions closely approach those of the Otto cycle. The greenhouse gases are shown to be reduced by more than 80%, nitrogen oxides by up to 70%, and exhaust smoke by nearly 80%. These single cylinder engine test results and application of a vehicle simulation model allow forecasts to be made of the on-road performance of a converted diesel engine. Small energy gains are predicted with substantial reduction in emissions under urban and highway driving conditions.