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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.

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Committee, Reports and Technical Notes of the U.S. National Advisory Committee for Aeronautics, and publications of other similar research bodies as issued

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Committee, Reports and Technical Notes of the U.S. National Advisory Committee for Aeronautics, and publications of other similar research bodies as issued

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Committee, Reports and Technical Notes of the U.S. National Advisory Committee for Aeronautics, and publications of other similar research bodies as issued

The purpose of this study is to get much insight about the combustion and emission characteristics of partially processed high free fatty acid linseed oil, i.e. esterified linseed oil (ELO), and diesel fuel in a single-cylinder compression ignition engine.

The variable compression ratio (CR) diesel engine (3.5 kW) of CR ranging from 12:1 to 18:1 is used for the experimentation purpose. In this study, CR varied from 16:1 to 18:1 for investigating the combustion and emissions characteristics of ELO. Various features such as combustion pressure, net heat release rate and mean gas temperature are analysed. The emission characteristics such as hydrocarbon, carbon monoxide, carbon dioxide and nitrogen dioxide are investigated with different loads and CRs. The effect of an ambient temperature condition is also reported.

Results from this investigation reveal that the burning of ELO is found to be advanced for all CRs as compared to diesel fuel, whereas these features were found to be lower for a CR of 17. Emissions of ELO are found to be higher at all loads and CRs. Overall, this study provides a necessary framework to enhance further research in this area.

This investigation shows that ELO has better combustion in the first phase of combustion. However, the exhaust emissions of ELO have higher value due to improper combustion in the second and subsequent phase of combustion due to higher viscosity.

In the carbon dioxide capture and storage (CCS) project, the integrity of CO₂ injection wells plays a vital role in the long‐term safety of CO₂ storage. The authors aim to practically investigate possible CO₂ leakage of a CO₂ injection well section during the injection operation and shut‐in by the thermomechanical FEM simulation. The application of numerical simulation to the CO₂ injection well deep underground is the first step that will help in the quantitative evaluation of the mechanical risks.

The injection of CO₂ at a temperature different from those of the well and the surrounding geological formation is likely to cause different thermal deformations of constitutive well materials. This could lead to cement cracking and microannuli openings at the interfaces of different materials such as casing/cement and cement/rock. In this paper, the possibility and order of magnitude of cement cracking and microannuli creation in the cross section of the well are assessed from a numerical case study within a classical thermomechanical finite element model framework.

The possibility of compressive failure and tensile cracking in the cement of the studied wells due to CO₂ injection is small unless a large casing eccentricity or an initial defect in the cement is present. Some microannuli openings are generated at interfaces cement/casing and/or cement/rock during the CO₂ injection because of different thermal shrinkage of each material. However, the width is not important enough to cause significant CO₂ leakage under the studied conditions. The use of “flexible” cement especially developed for oil well applications could mitigate the risk of cement cracking during CO₂ injection.

Numerous experimental studies on the chemical deterioration of the cement under severe conditions have been carried out. On the other hand, only a few investigations have focused on the mechanical behavior under thermal/pressure changes related to CO₂ injection. In this paper, the quantitative analysis to investigate cement cracking and microannuli formation is achieved to help in the identification of possible mechanical defects to cause CO₂ leakage. In addition, the discussion about the risk of the possible casing eccentricity and the application of flexible cement in the oil and gas field to CO₂ injection well could be practically useful.

A numerical analysis is given for the prediction of unsteady, two‐dimensional fluid flow induced by a heat and mass source in an initially closed cavity which is vented when the internal overpressure reaches a certain level. A modified ICE technique is used for solving the Navier–Stokes equations governing a compressible flow at a low Mach number and high temperature. Particular attention is focused on the treatment of the boundary conditions on the vent surface. This has been treated by an original procedure using the resolution of a Riemann problem. The configuration investigated may be viewed as a test problem which allows simulation of the ventilation and cooling of such cavities. The injection of hot gases is found to play a key role on the temperature field in the enclosure, whereas the vent seems to produce a distortion of the dynamic flow‐field only. When the injection of hot gases is stopped, the enclosure heat transfer is strongly influenced by the vent. A comparison with the results obtained when the radiative heat transfer between the walls of the enclosure is considered, indicate that radiation dominates the heat transfer in the enclosure and alters the flow patterns significantly.

IN the year 1890, Herbert Akroyd Stuart took out a British patent in which, for the first time, mention is made of an engine which may be said to bear some resemblance to the modern compression‐ignition engine.

ON aircraft operating in the rarefied atmosphere at high altitude, the idea of supplementing the air consumed by the engine with extra oxygen would seem to be a logical and desirable development, because the power output of a reciprocating engine is a direct function of the oxygen content of the air charge, provided that all the oxygen is burnt in the cylinder. However, the normal and most satisfactory line of development has been to fit the aircraft with engines of increased capacity or supercharge, so that the oxygen content of the air charge is increased simply by increasing the total mass of air consumed by the engine.