Catalytic exhaust gas fuel reforming for diesel engines—effects of water addition on hydrogen production and fuel conversion efficiency

Previous work in our laboratory has shown that the exhaust gas assisted fuel reforming process has the potential to provide a solution to the diesel engine exhaust emission problems. When simulated reformer product gas rich in hydrogen is fed to the engine, a reduction of both NO_x and smoke emissions can be achieved. In this paper, the optimisation of the reforming process by water addition in the reactor is presented. Using a prototype catalyst at 290°C reactor inlet temperature, up to 15% more hydrogen in the reformer product was obtained compared to operation without water. The process has been found to be mainly a combination of the fuel oxidation, steam reforming and water gas shift reactions. The reforming process efficiency has been shown to improve considerably with water addition up to a certain level after which the adverse effects of the exothermic water gas shift reaction become significant.     

A water–water preheater and a steam–water heater network: Temperature dynamics

The dynamic simulation of an integrated, double pipe heat exchanger network was validated through experimentation. A steam–water, concentric tube, heat exchanger was coupled to a water–water preheater. When the preheater was configured for cocurrent flow with equal fluid velocities in its annulus and core, Lagrangian-based derivations yielded analytical solutions that accurately predicted observed temperature dynamics. When the preheater was configured for countercurrent flow with distinct fluid velocities in its annulus and core, analytical solutions for the heater and connecting tubing were coupled with Eulerian based numerical solutions for the preheater. Programming used Mathcad. Nonlinear regression analysis of steady state data was used to determine system parameters. The significance of time delays through the integration of unit operations is illustrated.     

Experimental investigation and combustion analysis of a direct injection dual-fuel diesel–natural gas engine

A single-cylinder diesel engine has been converted into a dual-fuel engine to operate with natural gas together with a pilot injection of diesel fuel used to ignite the CNG–air charge. The CNG was injected into the intake manifold via a gas injector on purpose designed for this application. The main performance of the gas injector, such as flow coefficient, instantaneous mass flow rate, delay time between electrical signal and opening of the injector, have been characterized by testing the injector in a constant-volume optical vessel. The CNG jet structure has also been characterized by means of shadowgraphy technique.     

Exergetic performance and comparative assessment of bottoming power cycles operating with carbon dioxide–based binary mixture as working fluid

This paper presents CO₂-toluene (CO₂-C₇H₈) binary mixture as working fluid to enhance the energetic and exergetic performance of CO₂ bottoming power cycles in warm ambient conditions. A criterion for selection of CO₂-based binary mixture is defined, and 0.9 CO₂/0.1 C₇H₈ composition is decided based on the required minimum cycle temperature compatible with ambient conditions. Bottoming simple regenerative cycle (BSRC) and bottoming preheating cycle (BPHC) configurations are selected, and their realistic operating conditions are determined based on sensitivity analysis. The performance of bottoming cycles using CO₂-C₇H₈ binary mixture is compared with the bottoming cycles using pure CO₂ as working fluid at different ambient temperatures. It is observed that the cycles operating with pure CO₂ can only perform better at lower ambient temperature conditions, whereas, at the increased ambient temperatures, bottoming cycles with CO₂-C₇H₈ binary mixture outperform and produce significant gains in exergetic and energetic performance compared with pure CO₂ bottoming cycles. A maximum gain of exergetic efficiency for BSRC and BPHC observed is 26.83% and 18.71%, respectively, at an operating ambient temperature of 313 K, whereas an overall gain in energetic efficiencies for BSRC and BPHC observed is 28.92% and 10.12%, respectively. Taking into consideration thermodynamic performance, overall UA (product of overall heat transfer coefficient and heat transfer area for the heat exchanger) and specific investment cost, BPHC configuration is suggested as reasonable choice for higher ambient temperature conditions.     

Techno-economic comparison of energy usage between azeotropic distillation and hybrid system for water–ethanol separation

Conventional azeotropic distillation, consuming very high energy, is mostly used to produce high purity ethanol for renewable energy usage. In this study, the techno-economic comparison between azeotropic distillation (distillation followed by practical azeotropic distillation) and hybrid system (distillation followed by pervaporation system) for producing high purity of ethanol is demonstrated using the Pro II by Provision version 8.0. In the hybrid system, NaA zeolite membrane is used to separate the water from ethanol–water mixture. It is found that the hybrid system is the most effective technique for producing more than 99.4%wt of ethanol with an energy consumption of 52.4% less than the azeotropic distillation.     

Alternative fuel for gas turbine: Esterified jatropha oil–diesel blend

The oil crisis and the global effort to control the greenhouse effect have forced the researchers to think of various alternative energy sources. This decade has seen increasing importance of chemically treated vegetable oil biodiesel fuels for various applications in heat engines. Post-Kyoto negotiations refer to high level talks attempting to address global warming by limiting greenhouse gas emissions. During Climate Change Conference in Copenhagen the potential topics discussed were carbon capture and storage, biofuels, adaptation financing, technology transfer, sustainable agriculture, emissions targets, tropical forests and rural and transport electrification. Our area of interest is biofuels under which nonedible Jatropha oil due to its properties which are very close to diesel fuel is being explored as an alternative fuel. A lot of research is underway in the use of different biodiesel fuels in Internal Combustion engines, but very limited work has been reported in its use in gas turbines. This paper describes the results of an ongoing development program aimed at determining the technical feasibility of utilizing biodiesel in IS/60 Rovers gas turbine. The test rig is equipped with a dynamometer for turbine loading and AVL exhaust gas analyzer has been used to record emissions. The test results of 2 blends have been reported in this paper. Analyzing the results compared with the base line performance using diesel fuel under normal conditions show encouraging outcomes.     

Comparison between two optimization strategies for solid oxide fuel cell–gas turbine hybrid cycles

This paper compares the performance characteristics of a combined power system with solid oxide fuel cell (SOFC) and gas turbine (GT) working under two thermodynamic optimization strategies. Expressions of the optimized power output and efficiency for both the subsystems and the SOFC-GT hybrid cycle are derived. Optimal performance characteristics are discussed and compared in detail through a parametric analysis to evaluate the impact of multi-irreversibilities that take into account on the system behaviour. It is found that there exist certain new optimum criteria for some important design and operating parameters. Engineers should find the methodologies developed in this paper useful in the optimal design and practical operation of complex hybrid fuel cell power plants.     

Innovative concept for gasification for hydrogen based on the heat integration between water gas shift unit and coal–water–slurry gasification unit

In order to achieve the energy cascade utilization and improve the energy utilization efficiency of coal–water–slurry (CWS) gasification for hydrogen system, the heat integration scheme (HIS) between the water gas shift unit and the gasification unit is put forward. The effects of temperature change of CWS and oxygen on the gasification performance are investigated. Both the HIS and the non-heat integration scheme (NHIS) are analyzed by using gasification performance, energy conversion efficiency and exergy efficiency. The results show that the specific coal consumption and the specific oxygen consumption decrease by 2.7% and 6.5%, respectively, as the feedstock is preheated up to the temperature of 150 °C. The energy conversion efficiency of HIS and NHIS are nearly the same. The exergy efficiency of HIS (62.66%) is better than that of NHIS (62.02%). Therefore, the HIS is better than the NHIS by heat integration between the WGS unit and the gasification unit.     

Capillary pressure of a continuous gas–oil–water flow in a horizontal micron capillary

Capillary pressure is one of the most important factors in characterizing the fluid behavior in a wide variety of processes with environmental and energy concerns. In this paper, Washburn equation is extended to describe the displacement kinetics of the continuous gas–oil–water flow in a single horizontal tube. Experimental investigations of the continuous two- and three-phase flows in capillaries with diameters of 2–10 μm were performed to study the effect of the capillary pressure on their fluid behavior. The results indicate that the total capillary pressure of a continuous three-phase flow is affected by the combined action of the two fluid interfaces presented: gas–liquid and liquid–liquid interfaces.     

Performance and emission characteristics of a diesel engine fueled with coconut oil–diesel fuel blend

The objective of the present study is to reveal the effects of pure coconut oil and coconut oil–diesel fuel blends on the performance and emissions of a direct injection diesel engine. Operation of the test engine with pure coconut oil and coconut oil–diesel fuel blends for a wide range of engine load conditions was shown to be successful even without engine modifications. It was also shown that increasing the amount of coconut oil in the coconut oil–diesel fuel blend resulted in lower smoke and NO_x emissions. However, this resulted in an increase in the BSFC. This was attributed to the lower heating value of neat coconut oil fuel compared to diesel fuel.     

Effect of engine parameters and type of gaseous fuel on the performance of dual-fuel gas diesel engines—A critical review

Petroleum resources are finite and, therefore, search for their alternative non-petroleum fuels for internal combustion engines is continuing all over the world. Moreover gases emitted by petroleum fuel driven vehicles have an adverse effect on the environment and human health. There is universal acceptance of the need to reduce such emissions. Towards this, scientists have proposed various solutions for diesel engines, one of which is the use of gaseous fuels as a supplement for liquid diesel fuel. These engines, which use conventional diesel fuel and gaseous fuel, are referred to as ‘dual-fuel engines’. Natural gas and bio-derived gas appear more attractive alternative fuels for dual-fuel engines in view of their friendly environmental nature. In the gas-fumigated dual-fuel engine, the primary fuel is mixed outside the cylinder before it is inducted into the cylinder. A pilot quantity of liquid fuel is injected towards the end of the compression stroke to initiate combustion. When considering a gaseous fuel for use in existing diesel engines, a number of issues which include, the effects of engine operating and design parameters, and type of gaseous fuel, on the performance of the dual-fuel engines, are important. This paper reviews the research on above issues carried out by various scientists in different diesel engines. This paper touches upon performance, combustion and emission characteristics of dual-fuel engines which use natural gas, biogas, producer gas, methane, liquefied petroleum gas, propane, etc. as gaseous fuel. It reveals that ‘dual-fuel concept’ is a promising technique for controlling both NO_x and soot emissions even on existing diesel engine. But, HC, CO emissions and ‘bsfc’ are higher for part load gas diesel engine operations. Thermal efficiency of dual-fuel engines improve either with increased engine speed, or with advanced injection timings, or with increased amount of pilot fuel. The ignition characteristics of the gaseous fuels need more research for a long-term use in a dual-fuel engine. It is found that, the selection of engine operating and design parameters play a vital role in minimizing the performance divergences between an existing diesel engine and a ‘gas diesel engine’.     

Theoretical and experimental study on the performance of a diesel engine fueled with diesel–biodiesel blends

This study reports the effects of engine load and biodiesel percentage on the performance of a diesel engine fueled with diesel–biodiesel blends by experiments and a new theoretical model based on the finite-time thermodynamics (FTT). In recent years, biodiesel utilization in diesel engines has been popular due to depletion of petroleum-based diesel fuel. In this study, performance of a single cylinder, four-stroke, direct injection (DI) diesel engine fueled with diesel–biodiesel mixtures has been experimentally and theoretically investigated. The simulation results agree with the experimental data. After model validation, the effects of engine load and biodiesel percentage on engine performance have been parametrically investigated. The results showed that, effective power increases constantly, effective efficiency increases to a specified value and then starts to decrease with increasing engine load at constant biodiesel percentage and compression ratio. However, effective efficiency increases, effective power decreases to a certain value and then begins to increase with increasing biodiesel percentage at constant equivalence ratio and compression ratio.     

Experimental investigation on the performance and emissions of a diesel engine fuelled with ethanol–diesel blends

An experimental investigation on the application of the blends of ethanol with diesel to a diesel engine was carried out. First, the solubility of ethanol and diesel was conducted with and without the additive of normal butanol (n-butanol). Furthermore, experimental tests were carried out to study the performance and emissions of the engine fuelled with the blends compared with those fuelled by diesel. The test results show that it is feasible and applicable for the blends with n-butanol to replace pure diesel as the fuel for diesel engine; the thermal efficiencies of the engine fuelled by the blends were comparable with that fuelled by diesel, with some increase of fuel consumptions, which is due to the lower heating value of ethanol. The characteristics of the emissions were also studied. Fuelled by the blends, it is found that the smoke emissions from the engine fuelled by the blends were all lower than that fuelled by diesel; the carbon monoxide (CO) were reduced when the engine ran at and above its half loads, but were increased at low loads and low speed; the hydrocarbon (HC) emissions were all higher except for the top loads at high speed; the nitrogen oxides (NO_x) emissions were different for different speeds, loads and blends.     

Evaluation of vibration characteristics of a hydroxyl (HHO) gas generator installed diesel engine fuelled with different diesel–biodiesel blends

There are two main reasons of alternative fuel search of scientists: environmental problems resulted from combustion of fossil fuels and limited reserves of crude oil. Biodiesel and Hydrogen (H₂) are two of the most promising alternative fuels with their environmental friendly combustion profiles. The aim of this study was to evaluate vibration level of a hydroxyl (HHO) gas generator installed and diesel engine using different kinds of biodiesel fuels. In this study, at different flow rates, the effect of HHO gas addition on engine vibration performance was investigated with a Mitsubishi Canter 4D34-2A diesel engine. HHO gas introduced to the test engine via its intake manifold with 2, 4 and 6 L per minute (LPM) flow rates when the engine was fuelled with sunflower, canola, and corn biodiesels. The vibration data was collected between 1200 and 2400 rpm engine speeds by 300 rpm intervals. Finally, artificial neural network (ANN) approach was conducted in order to predict the effect of fuel properties and HHO amount on engine vibration level.     

A new hydrogenation-coupling approach for supra-equilibrium conversion in a water–gas shift reaction: Simultaneous hydrogen generation and chemical storage

This work reports a practical system of hydrogenation-coupled water–gas shift reaction (HC-WGSR) for simultaneous hydrogen production and storage. The performance of the HC-WGSR system was predicted through thermodynamic simulation. The proof-of-concept tandem water–gas shift and propene hydrogenation strategy was successfully demonstrated using a bifunctional catalyst. The hydrogen produced from the WGSR was successfully stored in propane simultaneously, and the overall CO conversion of nearly 100% overcame the equilibrium limitation of the WGSR over a wide range of space velocities (3000 - 6000 h⁻¹) at 200 ^°C and 1 bar. This study demonstrated that the in situ removal/storage of H₂ using the hydrogenation-coupling approach is promising even in a CO₂-rich environment (20% CO₂). The new approach shall see a great opportunity in using organic hydrogen carriers, e.g., benzene, toluene, N-ethylcarbazole, to expand the industrial applications, underpinning the global supply chain for hydrogen energy.     

Turbulent forced convection of Cu–water nanofluid: CFD model comparison

This study compares the predictions of five types of computational fluid dynamics (CFD) models, including two single-phase models (i.e. Newtonian and non-Newtonian) and three two-phase models (Eulerian–Eulerian, mixture and Eulerian–Lagrangian), to investigate turbulent forced convection of Cu–water nanofluid in a tube with a constant heat flux on the tube wall. The Reynolds (Re) number of the flow is taken between 10,000 and 25,000, while the volume fraction of Cu particles used is in the range of 0% to 2%. The results from the CFD models are compared with results of experimental investigations from literature. According to the results of this study, the non-Newtonian single-phase model, in general, does not show a good agreement with Xuan and Li's correlation in the prediction of the Nu number. The Eulerian–Eulerian model gives inaccurate results except for φ = 0.5%. The mixture model gives a maximum error of 15%. The Newtonian single-phase model and Eulerian–Lagrangian model, overall, are the recommended models. This work can be used as a reference for selecting an appropriate model for future investigation. The study also gives a proper insight into the important factors such as the Brownian motion, fluid behavior parameters and effective nanoparticle conductivity which should be considered or changed by each model.     

Adsorption properties of a natural zeolite–water pair for use in adsorption cooling cycles

The equilibrium adsorption capacity of water on a natural zeolite has been experimentally determined at different zeolite temperatures and water vapor pressures for use in an adsorption cooling system. The Dubinin–Astakhov adsorption equilibrium model is fitted to experimental data with an acceptable error limit. Separate correlations are obtained for adsorption and desorption processes as well as a single correlation to model both processes. The isosteric heat of adsorption of water on zeolite has been calculated using the Clausius–Clapeyron equation as a function of adsorption capacity. The cyclic adsorption capacity swing for different condenser, evaporator and adsorbent temperatures is compared with that for the following adsorbent–refrigerant pairs: activated carbon–methanol; silica gel–water; and, zeolite 13X–water. Experimental results show that the maximum adsorption capacity of natural zeolite is nearly 0.12 kg_w/kg_ad for zeolite temperatures and water vapor pressures in the range 40–150 °C and 0.87–7.38 kPa.     

High-purity hydrogen gas from the reaction between BOF steel slag and water in the 473–673 K range

A novel method for producing hydrogen with water and BOF steel slag was developed. The steel slag was reacted with water during 2–57 days at 50 MPa for temperatures ranging from 473 to 673 K. The quantitative evolution of the slag and gas compositions indicated that the main H₂ producing reaction is:     

Experimental investigation on performance and emission characteristics of waste tire pyrolysis oil–diesel blends in a diesel engine

Disposal of waste tires is one of the most important problems that should be solved. This problem can be solved by considering waste tires for production of hydrogen or fuel for diesel engines. This paper presents the studies on the performance and emission characteristics of a four stroke, four cylinders, naturally aspirated, direct-injected diesel engine running with various blends of waste tire pyrolysis oil (WTPO) with diesel fuel. Fuel properties, engine performance, and exhaust emissions of WTPO and its blends were analyzed and compared with those of petroleum diesel fuel. The experimental results showed that WTPO–diesel blends indicated similar performance with diesel fuel in terms of torque and power output of the test engine. It was found that the blends of pyrolysis oil of waste tire WTPO10 can efficiently be used in diesel engines without any engine modifications.     

Performance comparison of double-effect parallel-flow and series flow water–lithium bromide absorption systems

The double-effect parallel flow absorption refrigeration cycle with water–lithium bromide as working fluid is analysed based on the concept of equilibrium temperature at the low pressure generator. Coefficient of performance (COP) and its sensitivity to operating conditions are compared with those for series flow cycle. Maximum attainable COP for parallel flow cycle is greater than that for series flow cycle throughout the range of operating conditions considered here. Performance of parallel flow system is more sensitive to the effectiveness of low pressure heat exchanger than that of series flow system.