Showing papers on "Thermal efficiency published in 2007"
TL;DR: In this paper, the effect of reducing Jatropha oil's viscosity by increasing the fuel temperature (using waste heat of the exhaust gases) and thereby eliminating its effect on combustion and emission characteristics of the engine was investigated.
611 citations
TL;DR: In this paper, a single-cylinder diesel engine was tested with high speed diesel (HSD) and polanga oil methyl ester (POME) fuel blends (20, 40, 60, 80, and 100%) for short-term engine performance tests at varying loads.
520 citations
TL;DR: In this article, the performance of hydrogen production via steam methane reforming (SMR) is evaluated using exergy analysis, with emphasis on exergy flows, destruction, waste, and efficiencies.
404 citations
TL;DR: In this article, the effects of biodiesel (rapeseed methyl ester, RME) and different diesel/RME blends on the diesel engine NOx emissions, smoke, fuel consumption, engine efficiency, cylinder pressure and net heat release rate are analyzed and presented.
376 citations
TL;DR: In this paper, the authors investigated the performance of two low cost heat extraction improvement modifications in the channel of a PV/T air system to achieve higher thermal output and PV cooling so as to keep the electrical efficiency at acceptable level.
366 citations
TL;DR: In this paper, the effect of hydrogen addition on a natural gas engine's thermal efficiency and emission was analyzed using variable composition hydrogen/CNG mixtures (HCNG), and the results showed that hydrogen enrichment could significantly extend the lean operation limit, improve the engine's lean burn ability, and decrease burn duration.
337 citations
TL;DR: In this article, a closed cycle pressure-retarded osmosis (PRO) process known as an osmotic heat engine (OHE) is presented, using semi-permeable membranes to convert thermal energy into mechanical work.
253 citations
TL;DR: In this article, hydrogen was added in small amounts (5, 10% and 15% on the energy basis) to biogas and tested in a spark ignition engine at constant speed at different equivalence ratios to study the effects on performance, emissions and combustion.
245 citations
TL;DR: In this paper, the effects of injection timing and spark timing on engine performance and NO x emission were investigated under wide engine loads under a single-cylinder test engine using a high-pressure gas injector, and the results indicate that direct injection of hydrogen prevents backfire and high thermal efficiency and output power can be achieved by hydrogen injection during late compression stroke.
244 citations
TL;DR: In this paper, an artificial neural network (ANN) model was used to predict the brake specific fuel consumption, brake thermal efficiency, exhaust gas temperature and exhaust emissions of a gasoline engine.
231 citations
TL;DR: In this paper, an experimental investigation into heat transfer and mass flow in thermosyphoning air heaters, such as solar chimneys and Trombe walls, was conducted.
TL;DR: In this article, a direct injection engine operating on various fractions of natural gas-hydrogen blends was investigated and the results showed that the brake effective thermal efficiency increased with the increase of hydrogen fraction at low and medium engine loads and high thermal efficiency was maintained at the high engine load.
TL;DR: In this article, heat transfer of supercritical water has been investigated in various flow channels using the computational fluid dynamics (CFD) code CFX-5.6 to provide basic knowledge of the heat transfer behaviour and to gather the first experience in the application of CFD codes to heat transfer in supercritical fluids.
TL;DR: In this paper, a diesel engine using hydrogen as fuel was investigated with diesel as an ignition source for hydrogen, where hydrogen was injected into the intake port, while diesel was injected directly inside the cylinder.
TL;DR: In this paper, an experimental study of a centralized photovoltaic and hot water collector wall system that can serve as a water pre-heating system was conducted. But the authors did not consider the thermal efficiency of the system.
TL;DR: In this article, the results of a four-cylinder engine test with mixtures of hydrogen in methane of 0, 10, 20 and 30% by volume have been experimentally considered.
TL;DR: In this paper, the analysis of the combustion, performance and emission characteristics of a direct injection diesel engine with jatropha methyl ester (JTME), diesel and their blends is presented.
Abstract: This work involves the analysis of the combustion, performance and emission characteristics of a direct injection diesel engine fuelled with jatropha methyl ester (JTME), diesel and their blends JTME is prepared by the alkali transesterification of Jatropha oil with methanol The combustion parameters are determined by measuring in-cylinder pressure with respect to crank angle The results show that ignition delay, maximum heat release rate and combustion duration are lower for JTME and its blends compared to diesel Though JTME and its blends recorded lower Brake thermal efficiency, they have lower tail pipe emissions as compared to diesel, except for nitrogen oxides
TL;DR: In this paper, the effects of MEA on engine's power, fuel economy, emissions and combustion characteristics were studied on a single cylinder DI diesel engine under the same speed and load conditions, the maximum cylinder pressure decreases when fueled with the blends, while the ignition delays and the combustion duration becomes shorter.
TL;DR: In this paper, a novel ammonia-water cycle is proposed for the cogeneration of power and refrigeration, where a splitting /absorption unit is introduced and integrated with an ammonia Rankine cycle and an ammonia refrigeration cycle.
TL;DR: In this article, the authors reviewed the appropriateness of the Carnot cycle as the ideal model for geothermal binary power plants and showed that the ideal trilateral cycle is more suitable than the traditional triangular cycle.
TL;DR: In this article, the performance of the Kalina cycle system 11 (KCS11) is examined for low-temperature geothermal heat sources and is compared with an organic Rankine cycle.
Abstract: The possibility of exploiting low-temperature heat sources has been of great significance with ever increasing energy demand. Optimum and cost-effective design of the power cycles provide a means of utilization of low-temperature heat sources which might otherwise be discarded. In this analysis, the performance of the Kalina cycle system 11 (KCS11) is examined for low-temperature geothermal heat sources and is compared with an organic Rankine cycle. The effect of the ammonia fraction and turbine inlet pressure on the cycle performance is investigated in detail. Results show that for a given turbine inlet pressure, an optimum ammonia fraction can be found that yields the maximum cycle efficiency. Further, the maximum cycle efficiency does not necessarily yield the optimum operating conditions for the system. In addition, it is important to consider the utilization of the various circulating media (i.e., working fluid, cooling water, and heat resource) and heat exchanger area per unit power produced. For given conditions, an optimum range of operating pressure and ammonia fraction can be identified that result in optimum cycle performance. In general, the KCS11 has better overall performance at moderate pressures than that of the organic Rankine cycle.
TL;DR: In this article, a unique solar thermal electric system is proposed and tested in the present study, which uses an organic working fluid, which is suitable for a temperature range appropriate for solar energy, is adopted.
Abstract: A unique solar thermal electric system is proposed and tested in the present study. In this system, an organic working fluid, which is suitable for a temperature range appropriate for solar energy, is adopted. We call this system as “solar organic Rankine cycle system” (SORCS). In order to improve the thermal efficiency by using solar energy, a displacement-type scroll expander and compound parabolic concentrator (CPC) solar collector are used. This system consists of very simple components that are similar to the ones used in an air conditioner and is very cost effective. The present paper reports on the experimental results of the scroll expander unit and the practical operation of the proposed SORCS under actual solar radiation input. The total thermal efficiency of the present SORCS attains 7% (42% when cooling water is used for the cogeneration system).
TL;DR: In this article, a numerical study of a thermodynamic cycle is described: solar energy powered Rankine cycle using supercritical carbon dioxide as the working fluid for combined power and heat production.
TL;DR: In this article, a very high temperature gas-cooled Reactor (VHTR) assisted hydrogen production system using the high temperature electrolysis of steam (HTES) technology was investigated.
TL;DR: In this article, the effect of varying water inlet temperature to the collector on the exergy efficiencies of the SWH system components was investigated, and an exergy efficiency correlation for the solar collector studied was also presented to determine its exergetic performance.
TL;DR: In this article, the performance of a small-scale two-staged gasification system is reported, where wood chips are gasified with a fixed bed gasifier and then tar in the produced gas is reformed in a non-catalytic reformer, finally the production gas is used to generate electricity.
Patent•
04 Oct 2007
TL;DR: In this article, a cascaded organic Rankine cycle (ORC) system with two waste heat sources from a positive-displacement engine (106) was proposed. But the system was not shown to work well in the real world.
Abstract: A method and system for operating a cascaded organic Rankine cycle (ORC) system (100) utilizes two waste heat sources from a positive-displacement engine (106), resulting in increased efficiency of the engine (106) and the cascaded ORC system (100). A high temperature waste heat source from the positive-displacement engine (106) is used in a first ORC system (102) to vaporize a first working fluid (118). A low temperature waste heat source from the positive-displacement engine (106) is used in a second ORC system (104) to heat a second working fluid (130) to a temperature less than the vaporization temperature. The second working fluid (130) is then vaporized using heat from the first working fluid (118). In an exemplary embodiment, the positive-displacement engine (106) is a reciprocating engine. The high temperature waste heat source may be exhaust gas and the low temperature waste heat source may be jacket cooling water.
21 Dec 2007
TL;DR: A simplified combined cycle gas power plant and a MEA (monoethanol amine) based CO2 removal process have been simulated with the process simulation tool Aspen HYSYS.
Abstract: A simplified combined cycle gas power plant and a MEA (monoethanol amine) based CO2 removal process have been simulated with the process simulation tool Aspen HYSYS. The thermodynamic properties are calculated with the Peng Robinson and Amines Property Package models which are available in Aspen HYSYS. The adiabatic efficiencies in compressors, gas turbines and steam turbines have been fitted to achieve a total thermal efficiency of 58 % in the natural gas based power plant without CO2 removal. The efficiency is reduced to about 50 % with CO2 removal. The CO2 removal in % and the energy consumption in the CO2 removal plant are calculated as a function of amine circulation rate, absorption column height, absorption temperature and steam temperature. With CO2 removal of 85 %, heat consumption is calculated to 3.7 MJ/kg CO2 removed, close to a literature value of 4.0 MJ/kg CO2.
TL;DR: In this paper, a single cylinder hydrogen-fired engine was run at different equivalence ratios at full throttle and NO levels were found to rise after an equivalence ratio of 0.55, maximum value was about 7500 ppm.
TL;DR: In this paper, the control of ignition timing in the homogeneous charge compression ignition (HCCI) of n-heptane by port injection of reaction inhibitors was studied in a single-cylinder engine.