Showing papers on "Thermal efficiency published in 2011"
TL;DR: In this article, a fuel reactivity controlled compression ignition (RCCI) concept is demonstrated as a promising method to achieve high efficiency, which is demonstrated in a heavy-duty test engine over a range of loads.
Abstract: A fuel reactivity controlled compression ignition (RCCI) concept is demonstrated as a promising method to achieve high efficiency – clean combustion. Engine experiments were performed in a heavy-duty test engine over a range of loads. Additionally, RCCI engine experiments were compared to conventional diesel engine experiments. Detailed computational fluid dynamics modelling was then used to explain the experimentally observed trends. Specifically, it was found that RCCI combustion is capable of operating over a wide range of engine loads with near zero levels of NOx and soot, acceptable pressure rise rate and ringing intensity, and very high indicated efficiency. For example, a peak gross indicated efficiency of 56 per cent was observed at 9.3 bar indicated mean effective pressure and 1300 rev/min. The comparison between RCCI and conventional diesel showed a reduction in NOx by three orders of magnitude, a reduction in soot by a factor of six, and an increase in gross indicated efficiency of 16.4 per cen...
707 citations
TL;DR: In this article, an optimization procedure was conducted with a simulation program written in Matlab using five indicators: thermal efficiency, exergy efficiency, recovery efficiency, heat exchanger area per unit power output (APR), and the levelized energy cost (LEC).
617 citations
TL;DR: In this paper, a sizing model of the ORC is proposed, capable of predicting the cycle performance with different working fluids and different components sizes, based on the thermodynamic and economic optimization of a small scale ORC in waste heat recovery application.
613 citations
TL;DR: In this article, a dual-fuel engine with high-cetane fuel and natural gas injection is used to provide a source of ignition for the charge of a spark-ignition (SI) engine.
595 citations
TL;DR: In this paper, the suitability of waste cooking oil methyl ester as a biofuel has been established in a single cylinder four stroke variable compression ratio multi fuel engine when fueled with waste cooking oils methyl esters and its 20, 40, 60% and 80% blends with diesel (on a volume basis) are investigated and compared with standard diesel.
390 citations
TL;DR: In this article, a procedure to compare ORC working fluids based on their molecular components, temperature-entropy diagram and fluid effects on the thermal efficiency, net power generated, vapor expansion ratio, and exergy efficiency of the Rankine cycle has been proposed.
376 citations
TL;DR: In this article, Euro V diesel fuel, biodiesel, and ethanol-biodiesel blends (BE) were tested in a 4-cylinder direct-injection diesel engine to investigate the combustion, performance and emission characteristics of the engine under five engine loads at the maximum torque engine speed of 1800rpm.
337 citations
TL;DR: In this paper, the authors compared energy and exergy analyses of thermal power plants stimulated by coal and gas and provided a detailed review of different studies on thermal power plant over the years.
Abstract: The energy supply to demand narrowing down day by day around the world, the growing demand of power has made the power plants of scientific interest, but most of the power plants are designed by the energetic performance criteria based on first law of thermodynamics only. The real useful energy loss cannot be justified by the fist law of thermodynamics, because it does not differentiate between the quality and quantity of energy. The present study deals with the comparison of energy and exergy analyses of thermal power plants stimulated by coal and gas. This article provides a detailed review of different studies on thermal power plants over the years. This review would also throw light on the scope for further research and recommendations for improvement in the existing thermal power plants.
331 citations
TL;DR: In this article, high-temperature thermal storage in a packed bed of rocks is considered for air-based concentrated solar power plants, and the unsteady 1D two-phase energy conservation equations are formulated for combined convection and conduction heat transfer, and solved numerically for charging/discharging cycles.
317 citations
TL;DR: In this paper, a shell and finned tube heat exchanger integrated with an IC engine setup to extract heat from the exhaust gas and a thermal energy storage tank used to store the excess energy available is investigated in detail.
278 citations
TL;DR: In this paper, a supercritical Rankine cycle using zeotropic mixture working fluids for the conversion of low-grade heat into power is proposed and analyzed, and the proposed cycle can achieve thermal efficiencies of 10.8e13.4% with the cycle high temperature of 393 Ke473 K as compared to 9.7e10.1% for the organic rankine cycle.
TL;DR: In this article, a solar desalination system based on membrane distillation (MD) is presented and evaluated in the context of a European project, the MEDESOL project, a pilot plant was built to evaluate the system, which consists of three commercial MD modules coupled with a static solar collector's field.
TL;DR: In this paper, the effect of intake air temperature on combustion parameters, thermal efficiency, combustion efficiency and emissions in a modified two-cylinder, four-stroke HCCI engine was analyzed and discussed in detail.
TL;DR: In this paper, a turbocharged, direct injection, multi-cylinder truck diesel engine fitted with a mechanical distributor type fuel injection pump using biodiesel-methanol blend and neat karanji oil derived biodiesel under constant speed and varying load conditions without altering injection timings.
Abstract: The increased focus on alternative fuels research in the recent years are mainly driven by escalating crude oil prices, stringent emission norms and the concern on clean environment. The processed form of vegetable oil (biodiesel) has emerged as a potential substitute for diesel fuel on account of its renewable source and lesser emissions. The experimental work reported here has been carried out on a turbocharged, direct injection, multi-cylinder truck diesel engine fitted with mechanical distributor type fuel injection pump using biodiesel-methanol blend and neat karanji oil derived biodiesel under constant speed and varying load conditions without altering injection timings. The results of the experimental investigation indicate that the ignition delay for biodiesel-methanol blend is slightly higher as compared to neat biodiesel and the maximum increase is limited to 1 deg. CA. The maximum rate of pressure rise follow a trend of the ignition delay variations at these operating conditions. However, the peak cylinder pressure and peak energy release rate decreases for biodiesel-methanol blend. In general, a delayed start of combustion and lower combustion duration are observed for biodiesel-methanol blend compared to neat biodiesel fuel. A maximum thermal efficiency increase of 4.2% due to 10% methanol addition in the biodiesel is seen at 80% load and 16.67 s−1 engine speed. The unburnt hydrocarbon and carbon monoxide emissions are slightly higher for the methanol blend compared to neat biodiesel at low load conditions whereas at higher load conditions unburnt hydrocarbon emissions are comparable for the two fuels and carbon monoxide emissions decrease significantly for the methanol blend. A significant reduction in nitric oxide and smoke emissions are observed with the biodiesel-methanol blend investigated.
TL;DR: In this article, a 5.9-kW stationary diesel engine was converted into spark ignition mode and run on compressed natural gas (CNG), methane enriched biogas (Bio-CNG) and Biogas produced from biomethanation of jatropha and pongamia oil seed cakes.
TL;DR: In this paper, a photovoltaic/thermal (PV/T) solar air heater with a double pass configuration and vertical fins in the lower channel is investigated.
TL;DR: In this article, the design of a single glazed flat plate photovoltaic-thermal (PV-T) solar collector is discussed, focusing on the heat transfer between PV cells and fluid, and also on optical properties of materials.
TL;DR: In this article, the properties of the oil derived from waste plastics were analyzed and found that it has properties similar to that of diesel, and the engine could operate with 100% waste plastic oil and can be used as fuel in diesel engines.
TL;DR: In this article, a detailed analysis of an organic rankine cycle (ORC) heat recovery power plant using R134a as working fluid is presented, where mathematical models for the expander, evaporator, air cooled condenser and pump are developed to evaluate and optimize the plant performance, and the relationship between controlled variables (optimal relative working fluid mass flow rate, the optimal relative condenser fan airmass flow rate) and uncontrolled variables (the heat source temperature and the ambient dry bulb temperature) are near liner function for maximizing system net power generation and quadratic function
TL;DR: In this article, the authors investigated the possibility of exploiting wasted heat, converting it into electric energy by means of different energy systems, by extending the usual range of operation of existing technologies or introducing novel concepts.
TL;DR: In this paper, the influence of injection timing on the performance and emissions of a single cylinder, four stroke stationary, variable compression ratio, diesel engine was studied using waste cooking oil (WCO) as the biodiesel blended with diesel.
TL;DR: In this paper, the influence of compression ratio on the performance of a spark ignition engine fuelled by a blend of 78% gasoline-22% ethanol (E22) or hydrous ethanol(E100) was investigated.
TL;DR: In this article, a mathematical model for the overall thermal efficiency of the solar-powered high temperature differential dish-Stirling engine with finite-rate heat transfer, regenerative heat losses, conductive thermal bridging losses and finite regeneration processes time is developed.
TL;DR: In this paper, the authors describe possible implementations of an oxygen transport membrane (OTM) into an oxyfuel process, in particular that is three-end and four-end integration of the membrane whereby the focus is put on overall cycle efficiency and possible measures to improve cycle efficiency.
TL;DR: In this paper, a combined thermodynamic cycle for waste heat recovery of an internal combustion engine (ICE) is proposed, which consists of two cycles: the organic Rankine cycle (ORC) for recovering the waste heat of lubricant and high-temperature exhaust gas, and the Kalina cycle, for recovering waste heat from low-time temperature cooling water.
TL;DR: In this article, the authors presented the results of thermodynamics modelling studies of a 2kW biomass-fired CHP system with organic Rankine cycle (ORC) and three environmentally friendly refrigerants, namely HFE7000, HFE 7100 and n-pentane, have been selected as the ORC fluids.
Abstract: This paper presents the results of thermodynamics modelling studies of a 2 kW (e) biomass-fired CHP system with organic Rankine cycle (ORC). Three environmentally friendly refrigerants, namely HFE7000, HFE7100 and n-pentane, have been selected as the ORC fluids. The thermodynamic properties of the selected ORC fluids which have been predicted by commercial software (EES) are used to predict the thermal efficiency of ORC. The results of modelling show that under the simulated conditions (1) the ORC thermal efficiency with any selected ORC fluid is well below (roughly about 60% of) the Carnot cycle efficiency; the ORC efficiency depends on not only the modelling conditions but also the ORC fluid – the highest predicted ORC efficiency is 16.6%; the predicted ORC efficiency follows the following order: n-pentane > HFE7000 > HFE7100 (2) both superheating and sub-cooling are detrimental to the ORC efficiency (3) the electrical efficiency of the CHP system with the selected ORC fluids is predicted to be within the range of 7.5%–13.5%, mainly depending on the hot water temperature of the biomass boiler and the ORC condenser cooling water temperature as well as the ORC fluid, and corresponding to about 1.5 kW and 2.71 kW electricity output (4) the overall CHP efficiency of the CHP system is in the order of 80% for all three ORC fluids although the amount and quality of heating supplied by the CHP system depend on the ORC fluid selected and the modelling conditions.
TL;DR: In this paper, the potential for harnessing waste heat from power generation and thermal processes to perform such tasks is assessed by matching power plant outlet streams with applications at corresponding temperature ranges, and sufficient waste heat is identified to satisfy all USA space and water heating needs.
TL;DR: In this article, a novel method of extracting heat from a solar pond is to draw the heat from the gradient layer, which is analyzed theoretically and results of an experimental investigation at Bundoora East, RMIT, are presented.
TL;DR: In this paper, an empirical relationship between the gas turbine's ability to generate power when exposed to site ambient conditions, such as the ambient temperature, which differ from ISO conditions, was proposed.
TL;DR: In this article, a review summarizes the progress and recent trend made in the R&D of moderate or intense low oxygen dilution (MILD) combustion and recommends further fundamental studies for improving our knowledge and widening its applications.
Abstract: Moderate or intense low oxygen dilution (MILD) combustion plays a significant role in the mitigation of combustion- generated pollutants and greenhouse gases whilst meeting thermal efficiency needs. However, due to the lack of the fundamental knowledge on this combustion, there is a misconception that MILD combustion should be established by high preheating of the air, which has limited its application. Our research and development on this combustion has been performed for several years. We have found that the requirements for establishing the MILD combustion are more relaxed than previously. It is also revealed that this combustion of different type, i.e., non-premixed, partially premixed and fully premixed, can be achieved by firing various fuels (i.e., gaseous, liquid and solid fuels). It is suggested that the application of the MILD combustion can be expanded significantly. The present review summarizes the progress and recent trend made in the R&D of this combustion and recommends further fundamental studies for improving our knowledge and widening its applications.