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Thermal efficiency

About: Thermal efficiency is a research topic. Over the lifetime, 20911 publications have been published within this topic receiving 302373 citations. The topic is also known as: thermodynamic efficiency & efficiency.


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Journal ArticleDOI
TL;DR: In this paper, the performance, emissions, combustion characteristics and particulate size-number distribution of 10 and 20% methanol blends (M10 and M20) with gasoline in a medium duty spark ignition transportation engine, typically used in a mid-sized car vis-a-vis baseline gasoline.

144 citations

Journal ArticleDOI
TL;DR: In this paper, a literature review has been made about pre-chamber ignition systems as lean combustion technology, focusing in the several investigations regarding combustion and emissions characteristics and presenting the key advantages and challenges in pre chamber ignition technology application.

144 citations

Proceedings ArticleDOI
01 Jan 2009
TL;DR: In this paper, the authors compared the performance of conventional and geared turbofan engines for takeoff rating and showed that the main difference between the two types of turbofans is in the parts count.
Abstract: The potential for improving the thermodynamic efficiency of aircraft engines is limited because the aerodynamic quality of the turbomachines has already achieved a very high level. While in the past increasing burner exit temperature did contribute to better cycle efficiency, this is no longer the case with today’s temperatures in the range of 1900...2000K. Increasing the cycle pressure ratio above 40 will yield only a small fuel consumption benefit. Therefore the only way to improve the fuel efficiency of aircraft engines significantly is to increase bypass ratio — which yields higher propulsive efficiency. A purely thermodynamic cycle study shows that specific fuel consumption decreases continuously with increasing bypass ratio. However, thermodynamics alone is a too simplistic view of the problem. A conventional direct drive turbofan of bypass ratio 6 looks very different to an engine with bypass ratio 10. Increasing bypass ratio above 10 makes it attractive to design an engine with a gearbox to separate the fan speed from the other low pressure components. Different rules apply for optimizing turbofans of conventional designs and those with a gearbox. This paper describes various criteria to be considered for optimizing the respective engines and their components. For illustrating the main differences between conventional and geared turbofans it is assumed that an existing core of medium pressure ratio with a two stage high pressure turbine is to be used. The design of the engines is done for takeoff rating because this is the mechanically most challenging condition. For each engine the flow annulus is examined and stress calculations for the disks are performed. The result of the integrated aero-thermodynamic and mechanical study allows a comparison of the fundamental differences between conventional and geared turbofans. At the same bypass ratio there will be no significant difference in specific fuel consumption between the alternative designs. The main difference is in the parts count which is much lower for the geared turbofan than for the conventional engine. However, these parts will be mechanically much more challenging than those of a conventional turbofan. If the bypass ratio is increased significantly above 10, then the geared turbofan becomes more and more attractive and the conventional turbofan design is no longer a real option. The maximum practical bypass ratio for ducted fans depends on the nacelle drag and how the installation problems can be solved.Copyright © 2009 by ASME

144 citations

Journal ArticleDOI
TL;DR: In this article, the performance, combustion and emission characteristics of a single cylinder direct injection (DI) diesel engine with three fuel series: B20, B20A30C30 and B100A30 C30 were investigated.

144 citations

Journal ArticleDOI
TL;DR: In this paper, the authors have reviewed the performance of different types of natural gas engines, including pure NG engine, pure NG/gasoline bi-fuel engine, NG/diesel dual fuel engine and HCNG engine.
Abstract: Natural gas (NG) is one of the most important and successful alternative fuels for vehicles. Engine combustion and emission fuelled with natural gas have been reviewed by NG/gasoline bi-fuel engine, pure NG engine, NG/diesel dual fuel engine and HCNG engine. Compared to using gasoline, bi-fuel engine using NG exhibits higher thermal efficiency; produces lower HC, CO and PM emissions and higher NOx emission. The bi-fuel mode can not fully exert the advantages of NG. Optimization of structure design for engine chamber, injection parameters including injection timing, injection pressure and multi injection, and lean burn provides a technological route to achieve high efficiency, low emissions and balance between HC and NOx. Compared to diesel, NG/diesel dual fuel engine exhibits longer ignition delay; has lower thermal efficiency at low and partial loads and higher at medium and high loads; emits higher HC and CO emissions and lower PM and NOx emissions. The addition of hydrogen can further improve the thermal efficiency and decrease the HC, CO and PM emissions of NG engine, while significantly increase the NOx emission. In each mode, methane is the major composition of THC emission and it has great warming potential. Methane emission can be decreased by hydrogen addition and after-treatment technology.

144 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023418
2022839
20211,279
20201,203
20191,197
20181,145