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The development of a theoretical model for predicting the combustion, performance and emission characteristics of a cylinder head porous medium engine becomes necessary due to imposed requirements from the viewpoint of power, efficiency and toxic gases in the exhaust. The cylinder head porous medium engine was found to have superior combustion, performance and emission characteristics when compared to a conventional diesel engine. The paper aims to discuss these issues.

Due to heterogeneous and transient operation of diesel engine under conventional and porous medium mode, the combustion process becomes complex, and achieving a pure analytical solution to the problem was difficult. Although, closer accuracy of correlation between the computer models and the experimental results is improbable, the computer model will give an opportunity to quantify the combustion and heat transfer processes and thus the performance and emission characteristics of an engine.

In this research work, a theoretical model was developed to predict the combustion, performance and emission characteristics of a cylinder head porous medium engine through two-zone combustion modeling technique, and the results were validated through experimentation.

The two-zone model developed by using programming language C for the purpose of predicting combustion, performance and emission characteristics of a porous medium engine is the first of its kind.

The paper is mainly concerned with how the gas‐turbine designer can choose the best design of liquid or gaseous fuel combustion chamber for his purpose. In the method proposed, combustion chamber test data are expressed in a way which gives the most general information about the design, by introducing dimensionless performance criteria. These criteria are then plotted in ways which enable the various chamber designs to be compared. The treatment deals implicitly with the conditions which satisfactory model tests must fulfil. An idealized model of a gas‐turbine combustion chamber is introduced in the light of which the effects of changes in overall fuel/air ratio can be explained more satisfactorily than when conditions in the flame‐tube are supposed homogeneous.

Spark ignition (SI) engines are used in a wide area in the transportation industry, from road vehicles to piston-prop aircraft. On the other hand, the decrease in reserves of fossil fuels used in SI engines and the increase in greenhouse gas emissions makes the use of alternative fuels inevitable. In this paper, optimization of in-cylinder combustion and engine performance parameters by intake-charge conditions [i.e. intake-air temperature, injection timing and exhaust gas recirculation (EGR)] in a hydrogen (H₂)-fueled small SI engine is performed.

Experimental studies were performed at a 1,600 rpm engine speed of a single-cylinder, air-cooled engine having a stroke volume of 476.5 cm³, maximum output power of 13 HP and torque of 25 Nm. The hydrogen-fueled SI engine was operated by a lean air-fuel mixture (ϕ = 0.6) under wide-open throttle (WOT) conditions.

The findings of the paper show that improvements can be achieved in in-cylinder combustion, indicated engine performance, exhaust NO_x emissions with optimum intake-air temperature, the start of H₂ injection and the ERG rate.

It has been determined that a 32°C intake-air temperature, 395°C (bTDC) start of H₂ injection, and 5%–10% EGR rates are the most suitable values for the examined hydrogen fueled SI engine.

Hydrogen is a usable alternative fuel for SI engines used in a wide area from road vehicles to piston-prop aircraft engines. However, a number of problems remain that limit hydrogen fueled SI engines to some extent, such as backfire, a decrease of engine power, and high NO_x emissions. Therefore, it is appropriate to examine the effects of intake-charge conditions on in-cylinder combustion, engine performance, and NO_x emissions parameters in a hydrogen fuelled SI engine.

The purpose of this paper is to formulate a structured approach to design an annular diffusion flame combustion chamber for use in the development of a 1,400 kW range aero turbo shaft engine. The purpose is extended to perform numerical combustion modeling by solving transient Favre Averaged Navier Stokes equations using realizable two equation k-e turbulence model and Discrete Ordinate radiation model. The presumed shape β-Probability Density Function (β-PDF) is used for turbulence chemistry interaction. The experiments are conducted on the real engine to validate the combustion chamber performance.

The combustor geometry is designed using the reference area method and semi-empirical correlations. The three dimensional combustor model is made using a commercial software. The numerical modeling of the combustion process is performed by following Eulerian approach. The functional testing of combustor was conducted to evaluate the performance.

The results obtained by the numerical modeling provide a detailed understanding of the combustor internal flow dynamics. The transient flame structures and streamline plots are presented. The velocity profiles obtained at different locations along the combustor by numerical modeling mostly go in-line with the previously published research works. The combustor exit temperature obtained by numerical modeling and experiment are found to be within the acceptable limit. These results form the basis of understanding the design procedure and opens-up avenues for further developments.

Internal flow and combustion dynamics obtained from numerical simulation are not experimented owing to non-availability of adequate research facilities.

This study contributes toward the understanding of basic procedures and firsthand experience in the design aspects of combustors for aero-engine applications. This work also highlights one of the efficient, faster and economical aero gas turbine annular diffusion flame combustion chamber design and development.

The main novelty in this work is the incorporation of scoops in the dilution zone of the numerical model of combustion chamber to augment the effectiveness of cooling of combustion products to obtain the desired combustor exit temperature. The use of polyhedral cells for computational domain discretization in combustion modeling for aero engine application helps in achieving faster convergence and reliable predictions. The methodology and procedures presented in this work provide a basic understanding of the design aspects to the beginners working in the gas turbine combustors particularly meant for turbo shaft engines applications.

THE advent of gas‐turbines as power plants for military and civil aircraft has demonstrated certain actual and potential advantages over the use of conventional piston engines which ensure the increased adoption and importance of this type of prime mover. This increased use of gas‐turbines in the aircraft field has necessitated careful reconsideration of the fuel supply position in the light of the new engine requirements. It is clear therefore that a detailed knowledge of all aspects of fuel performance in gas‐turbine‐powered aircraft is needed in order to enable the necessary usable fuel supply position to be assessed, and any resulting problems to be surmounted.

Compression ignition engines are being used in transportation, agricultural and industrial sectors due to its durability, fuel economy and higher efficiency. This paper aims to present investigation focuses on the utilization of nano additives in emulsified blends of Pongamia biodiesel and its impact on combustion, emission and performance characteristics of a diesel engine.

Pongamia biodiesel was produced through two-stage transesterification process. Taguchi method with L₉ Design of experiment was adopted to study the stability of fuel blends and 75 per cent diesel, 20 per cent biodiesel, 5 per cent water and 6 per cent of surfactant was found to be stable. Further, aluminum oxide nanoparticle was blended into the emulsified fuel in mass fraction of 100 ppm (D75-BD20-W5-S6-AO100) through ultrasonicating technique.

Oleic acid was found to be in prominent proportion in the Pongamia biodiesel. It was observed that D75-BD20-W5-S6 and D75-BD20-W5-S6-AO100 had the ability to produce lower in-cylinder pressure and rate of heat release compared to D100, B100 and D75-BD20 fuel blends. However, a higher rate of pressure rise was noticed in D75-BD20-W5-S6 and D75-BD20-W5-S6-AO100. Lower brake specific fuel consumption and relatively higher brake thermal efficiency were noticed in D75-BD20-W5-S6 and D75-BD20-W5-S6-AO100. Moreover, lower NO_x and smoke emission were also observed for nano-emulsified fuel blends.

Metal-based nano-additive significantly improved the physio-chemical properties of the fuel. Based on the literature, it is understood that emulsified biodiesel blend with nano enrichment using Pongamia biodiesel as base fuel was not carried out. Identifying a stable blend of diesel-biodiesel-water-nano additive using Taguchi’s design of experiments approach was an added value in formulating the test fuels. Furthermore, the formulated test fuel was compared with mineral diesel, biodiesel, and diesel-biodiesel blend to understand its suitability to use as a fuel in compression ignition (CI) engine.

Typical performance data for combustion chambers with separate introduction of fuel and air have already been presented in FIG. 1. Comparison with FIG. 7, typical of one‐stream chambers, reveals some important differences. Firstly, the data are neither confined within the inflammability limits nor have their peak at the stoichiometric O.F.A.R.; the shift is usually towards the weak side. Secondly, the ratio of the maximum O.F.A.R. to minimum O.F.A.R. of a given curve may be many times the corresponding range of a one‐stream chamber. Thirdly, the curves do not all terminate at substantially the same value of combustion efficiency. Particularly the second of these features is of great practical importance, for, in gas turbines, combustion chambers are required to cope with a very wide range of O.F.A.R. and must maintain a high efficiency throughout this range. The possibility of designing for a wide O.F.A.R. range is one of the reasons for using a two‐stream in preference to a one‐stream chamber. Some of the design features influencing O.F.A.R. range will be discussed below.

Over past decades, the fossil fuel reserves in the world have been decreasing at an alarming rate and a lack of crude oil is expected in the early decades of this century. Also, the eco-neutral pollutants such as carbon monoxide (CO), oxides of nitrigen (NOx) and unburnt hydrocarbons (UHC) are also increasing. This calls for innovative research in non-conventional fuels to replace fossil fuels. Hydrogen is one such fuel which has an exceptional combustion property and appears to be proving itself as the best transportation fuel of the future. On the other hand, compressed natural gas(CNG) has already been credited as a remarkable fuel for its better emission characteristics and has been implemented as a transportation fuel in metros. Therefore, the use of hydrogen blended with natural gas seems to be a viable alternative to pure fossil fuels because of the expected reduction of the total pollutants and increase of efficiency. This paper aims to investigate this issue.

In the present experimental investigation, 10 and 20 per cent of hydrogen–CNG mixture(HCNG) by mass of fuel is inducted into the combustion chamber in conjunction with air in HCNG–diesel dual fuel mode. The variation in injection opening pressure is assessed to optimize the performance and emission characteristics.

Experiments were conducted at three different injection opening pressures, i.e. 200, 220 and 240 bar, at full-load condition and the performance characteristics were calculated. The effect of injection operating pressure(IOP) on emissions were measured and compared with pure diesel mode.

Brake thermal efficiency (BTE) was increased by 1.2 per cent at 220 bar. Minimum BSFC of 0.2302 kg/kWh, 0.2114 kg/kWh was noticed for 220 bar with a changing ratio of 20 per cent of HCNG. It was noticed that CO and UHC decreased with variation in IOP and HCNG content in the blend. However, there was an increase in NOx emissions.

The purpose this experimentation is to study the combustion characteristics of compression ignition engine fuelled with mineral diesel. The reason behind the numerical simulation is to validate the experimental results of the combustion characteristics.

The numerical analysis was carried out in this study using MATLAB Simulink, and the zero dimensional combustion model was applied to predict the combustion parameters such as in cylinder pressure, pressure rise rate and rate of heat release.

Incorporating the dynamic combustion duration with respect to variable engine load in the zero dimensional combustion model using MATLAB Simulink reduced the variation of experimental and numerical outputs between 5.5 and 6 per cent in this analysis.

Validation of the experimental analysis is very limited. Investigations were performed using zero dimensional combustion model, which is the very appropriate for analysing the combustion characteristics.

Existing studies assumed that the combustion duration period as invariant in their numerical analysis, but with the real time scenario occurring in CI engine, that is not the case. In this analysis, mass fraction burnt considering the dynamic combustion duration was incorporated in the heat transfer model to reduce the error variation between experimental and numerical studies.

This study aims to contrastively investigate the effects of biodiesel and diesel on the power, economy and combustion characteristics of a compression ignition aviation piston engine for unmanned aerial vehicles.

Biodiesel used as alternative fuel will not be mixed with diesel during experimental study. Pure diesel fuel is used for the comparative test. Same fuel injection strategies, including pilot and main injection, are guaranteed for two fuels in same test points.

The engine-rated power of biodiesel is lower than diesel, which results in higher specific fuel combustion (SFC) and effective thermal efficiency (ETE). Biodiesel has the faster burning rate, shorter combustion duration. The crank angle of 50% mass fraction burned (CA50) is earlier than diesel. The ignition delay angle of biodiesel and diesel in the pilot injection stage is almost the same at high engine speed. As the speed and load decrease, the ignition delay angle of biodiesel in the pilot injection stage is smaller than diesel. At 100% high load conditions, the fuel-burning fraction of biodiesel in the pilot injection is the same as diesel. The peak heat release rate (HRR) of biodiesel is slightly lower than diesel. At 20% part load conditions, the fuel-burning fraction of biodiesel in the pilot injection stage is lower than diesel. Because of the combustion participation of unburned pilot injected fuel, the peak HRR of biodiesel in the main injection is equal to or even higher than diesel.

The application feasibility of alternative fuel and its effects on aviation engine power, economy and combustion characteristics will be evaluated according to the “drop-in“ requirements and on the low-cost premise without changing the aviation engine structure and parameters.