Effect of Ethanol on Part Load Thermal Efficiency and CO2 Emissions of SI Engines

2013 ◽  
Vol 6 (1) ◽  
pp. 456-469 ◽  
Author(s):  
Hosuk H. Jung ◽  
Michael H. Shelby ◽  
Charles E. Newman ◽  
Robert A. Stein
Keyword(s):  
Co2 Emissions ◽  
Thermal Efficiency ◽  
Part Load ◽  
Si Engines

scholarly journals Experimental Research on Controllability and Emissions of Jet-Controlled Compression Ignition Engine

Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2936 ◽  
Author(s):  
Hua Tian ◽  
Jingchen Cui ◽  
Tianhao Yang ◽  
Yao Fu ◽  
Jiangping Tian ◽  
...  
Keyword(s):  
Thermal Efficiency ◽  
High Speed ◽  
Compression Ignition ◽  
Compression Ignition Engine ◽  
Engine Emissions ◽  
Spark Timing ◽  
Crank Angle ◽  
Marine Engines ◽  
Si Engines ◽  
Ci Engines

Low-temperature combustions (LTCs), such as homogeneous charge compression ignition (HCCI), could achieve high thermal efficiency and low engine emissions by combining the advantages of spark-ignited (SI) engines and compression-ignited (CI) engines. Robust control of the ignition timing, however, still remains a hurdle to practical use. A novel technology of jet-controlled compression ignition (JCCI) was proposed to solve the issue. JCCI combustion phasing was controlled by hot jet formed from pre-chamber spark-ignited combustion. Experiments were done on a modified high-speed marine engine for JCCI characteristics research. The JCCI principle was verified by operating the engine individually in the mode of JCCI and in the mode of no pre-chamber jet under low- and medium-load working conditions. Effects of pre-chamber spark timing and intake charge temperature on JCCI process were tested. It was proven that the combustion phasing of the JCCI engine was closely related to the pre-chamber spark timing. A 20 °C temperature change of intake charge only caused a 2° crank angle change of the start of combustion. Extremely low nitrogen oxides (NOx) emission was achieved by JCCI combustion while keeping high thermal efficiency. The JCCI could be a promising technology for dual-fuel marine engines.

Semi-Closed Recuperated Cycle With Wet Compression

2017 ◽  
Author(s):  
Hans E. Wettstein
Keyword(s):  
Gas Turbine ◽  
Thermal Efficiency ◽  
Gas Turbines ◽  
Specific Power ◽  
Efficiency Gain ◽  
Lower Efficiency ◽  
Part Load ◽  
Thermal Transients ◽  
Wet Compression ◽  
Main Compressor

The semi-closed recuperated cycle (SCRC) has been suggested earlier by the author in several versions. The best of them used two compressors with one intercooling stage each. In this paper the intercooled main compressor has been replaced by a compressor with high fogging and no intercooling anymore. It is assumed that the system and the main compressor have its design points in the middle of the intended fogging water injection range. This turns out to allow another thermal efficiency gain by 2 to 3 percent points to clearly above 60% also combined with increased specific power related to the consumed combustion air and with no bottoming cycle. This paper demonstrates the technical feasibility based on Turbomachinery technologies, which have already proven commercial viability. The thermodynamic assumptions have been derived from existing gas turbine (GT) technology and are used within already confirmed operating ranges. With the same firing temperature also the thermal efficiency level of current Combined Cycles (GTCC) can be achieved. A special feature of the SCRC is the opportunity for inventory control of part load operation. This means that part load operation can be made by pressure reduction instead of temperature reduction as in open gas turbines. Thermal transients leading to hot part life consumption can therefore be avoided to a large extent and the combustor can operate at nearly constant temperature also at low part load with corresponding low emissions. Low part load operation achieves the same efficiency as base load. The result is more flexibility than in current GTCC technology associated with less complexity due to the needlessness of an extra bottoming cycle. Realizing this type of cycle aiming at its best efficiency potential however needs the development capability of a highly skilled gas turbine manufacturer. But it could also be developed for a lower efficiency range by using existing components with conservative data. The SCRC concept could also be aimed at combined heat and power applications or at naval propulsion by replacing CODOG’s. Due to its specific features the SCRC in general or with wet compression could be developed in the micro turbine power output size as well as up to above 1000MW single block size. Its inherent water condensation at elevated pressure makes an external source of make-up water obsolete.

Assessment of Future Aero Engine Designs With Intercooled and Intercooled Recuperated Cores

2010 ◽  
Author(s):  
Konstantinos G. Kyprianidis ◽  
Tomas Gro¨nstedt ◽  
S. O. T. Ogaji ◽  
P. Pilidis ◽  
R. Singh
Keyword(s):  
Co2 Emissions ◽  
Thermal Efficiency ◽  
Low Pressure ◽  
System Level ◽  
Nox Emissions ◽  
Variable Geometry ◽  
Lean Burn ◽  
Low Pressure Turbine ◽  
Aero Engine ◽  
Combustion Technology

Reduction of CO2 emissions is strongly linked with the improvement of engine specific fuel consumption, as well as the reduction of engine nacelle drag and weight. Conventional turbofan designs however that reduce CO2 emissions — such as increased OPR designs — can increase the production of NOx emissions. In the present work, funded by the European Framework 6 collaborative project NEWAC, an aero engine multidisciplinary design tool, TERA2020, has been utilised to study the potential benefits from introducing heat-exchanged cores in future turbofan engine designs. The tool comprises of various modules covering a wide range of disciplines: engine performance, engine aerodynamic and mechanical design, aircraft design and performance, emissions prediction and environmental impact, engine and airframe noise, as well as production, maintenance and direct operating costs. Fundamental performance differences between heat-exchanged cores and a conventional core are discussed and quantified. Cycle limitations imposed by mechanical considerations, operational limitations and emissions legislation are also discussed. The research work presented in this paper concludes with a full assessment at aircraft system level that reveals the significant potential performance benefits for the inter-cooled and intercooled recuperated cycles. An intercooled core can be designed for a significantly higher OPR and with reduced cooling air requirements, providing a higher thermal efficiency than could otherwise be practically achieved with a conventional core. Variable geometry can be implemented to optimise the use of the intercooler for a given flight mission. An intercooled recuperated core can provide high thermal efficiency at low OPR values and also benefit significantly from the introduction of a variable geometry low pressure turbine. The necessity of introducing novel lean-burn combustion technology, to reduce NOx emissions, at cruise as well as for the landing and take-off cycle, is demonstrated for both heat-exchanged cores and conventional designs. Significant benefits in terms of NOx reduction are predicted from the introduction of a variable geometry low pressure turbine in an intercooled core with lean-burn combustion technology.

scholarly journals The Influence of Charge Motion on Pre-Chamber and Main Chamber Combustion in a Highly Dilute Jet Ignition Engine

2021 ◽  
Vol 6 ◽  
Author(s):  
Michael Bunce ◽  
Alasdair Cairns ◽  
Sai Krishna Pothuraju Subramanyam ◽  
Nathan Peters ◽  
Hugh Blaxill
Keyword(s):  
Thermal Efficiency ◽  
Internal Combustion Engines ◽  
System Optimization ◽  
Combustion Stability ◽  
Main Chamber ◽  
Charge Motion ◽  
Ignition System ◽  
Lean Combustion ◽  
Si Engines ◽  
The Impact

Though there are multiple viable powertrain options available for the automotive sector, those that contain internal combustion engines will continue to account for the majority of global sales for the next several decades. It is therefore imperative to continue the pursuit of novel combustion concepts that produce efficiency levels significantly higher than those of current engines. Introducing high levels of dilution in spark ignited (SI) engines has consistently proven to produce an efficiency benefit compared to conventional stoichiometric engine operation. However, this combustion mode can present challenges for the ignition system. Pre-chamber jet ignition enables stable, highly dilute combustion by both increasing the ignition energy present in the system and distributing it throughout the combustion chamber. Previous work by the authors have shown that jet ignition produces 15–25% increases in thermal efficiency over baseline SI engines with only relatively minor changes to engine architecture. Lean combustion in general and jet ignition in particular represent fundamentally different engine operating modes compared to those of conventional stoichiometric SI engines. Therefore, there are some system sensitivities not present in stoichiometric engines that must be investigated in order to fully optimize the jet ignition system. Differing types and magnitudes of charge motion are incorporated in SI engines to aid with mixture preparation but the influence of charge motion over lean combustion performance, particularly in jet ignition engines, is less well understood. This study analyzes the impact that charge motion has on both pre-chamber and main chamber combustion. A 1.5 L 3-cylinder gasoline engine is outfitted with multiple intake port configurations producing varying magnitudes and types of charge motion. Pre-chamber and main chamber combustion stability and other burn parameter responses are analyzed across multiple speeds and loads, including at critical operating points such as a catalyst heating condition. The results show that there is combustion sensitivity to charge motion, resulting in >1 percentage point spread in peak thermal efficiency for the configurations tested, and that this sensitivity manifests most significantly under low ignitability conditions such as heavy dilution. These results provide guidance for future system optimization of jet ignition engines.

scholarly journals Off-Design Performance Comparison Between Single and Two-Shaft Engines: Part 1 — Fixed Geometry

2020 ◽  
Author(s):  
Th. Nikolaidis ◽  
A. Pellegrini ◽  
H. I. H. Saravanamuttoo ◽  
I. Aslanidou ◽  
A. Kalfas ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Mass Flow ◽  
Thermal Efficiency ◽  
Rotational Speed ◽  
Pressure Ratio ◽  
Performance Comparison ◽  
Part Load ◽  
Design Performance ◽  
Research Activities ◽  
Compressor Pressure Ratio

Abstract This paper describes an investigation into the off-design performance comparison of single and two-shaft gas turbine engines. A question that has been asked for a long time which gas turbine delivers a better thermal efficiency at part load. The authors, notwithstanding their intensive searches, were unable to find a comprehensive answer to this question. A detailed investigation was carried out using a state of the art performance evaluation method and the answer was found to be: It depends! In this work, the performance of two engine configurations is assessed. In the first one, the single-shaft gas turbine operates at constant shaft rotational speed. Thus, the shape of the compressor map rotational speed line will have an important influence on the performance of the engine. To explore the implications of the shape of the speed line, two single-shaft cases are examined. The first case is when the speed line is curved and as the compressor pressure ratio falls, the non-dimensional mass flow increases. The second case is when the speed line is vertical and as the compressor pressure ratio falls, the non-dimensional mass flow remains constant. In the second configuration, the two-shaft engine, the two-shafts can be controlled to operate at different rotational speeds and also varying relationships between the rotational speeds. The part-load operation is characterized by a reduction in the gas generator rotational speed. The tool, which was used in this study, is a 0-D whole engine simulation tool, named Turbomatch. It was developed at Cranfield and it is based on mass and energy balance, carried out through an iterative method, which is based on component maps. These generic, experimentally derived maps are scaled to match the design point of a particular engine before an off-design calculation is performed. The code has been validated against experimental data elsewhere, it has been used extensively for academic purposes and the research activities that have taken place at Cranfield University. For an ideal cycle, the single-shaft engine was found to be a clear winner in terms of part-load thermal efficiency. However, this picture changed when realistic component maps were utilized. The basic cycle and the shape of component maps had a profound influence on the outcome. The authors explored the influence of speed line shapes, levels of component efficiencies and the variation of these component efficiencies within the operating range. This paper describes how each one of these factors, individually, influences the outcome.

A Gas Turbine Cycle Selection Issue: Recuperated or ICR

2007 ◽  
Author(s):  
Colin Rodgers ◽  
Aubrey Stone ◽  
David White
Keyword(s):  
Gas Turbine ◽  
Thermal Efficiency ◽  
Heat Dissipation ◽  
Cycle Performance ◽  
Specific Power ◽  
Exhaust Emission ◽  
Inlet Temperature ◽  
Part Load ◽  
Pressure Losses ◽  
Exhaust Temperature

The intercooled recuperative gas turbine (ICR) potentially offers the advantages of higher specific power, and improved thermal efficiency compared to the recuperative gas turbine, such advantages are however contingent upon the additional parasitic encumbrances of the intercooler heat dissipation or recovery apparatus and pressure losses, plus flowpath ducting and complexity. The thermodynamic performances, relative sizing and relative costs of both an ICR and recuperative gas turbine engine, with a thermal efficiency goal approaching 40%, combined with low exhaust emission requirements were studied. The study encompassed primary candidate engine flowpath configurations comprising of single shaft, two shaft, and two spool designs, with both recuperation (R), and combined Intercooling and Recuperation (ICR). In conducting the study all engine flowpaths were sized for 300kW with a maximum turbine inlet temperature of 1837F (1000C), representative of conservative life limits for conventional un-cooled superalloy turbine rotors. Heat exchanger effectivenesses of the intercooler and recuperator were selected at 80 and 85%, as a compromise between cost, weight, and thermal efficiency considerations. The study confirmed that the simple recuperated cycle is capable of comparable peak thermal efficiency levels to the ICR provided that ICR intercooling parasitic losses are duly accounted, and furthermore has intrinsically lower manufacturing and development costs than the ICR. The cycle performance code used for the studies included prediction of engine exhaust emissions, part load characteristics, and compressor operating lines. The emissions assessment slightly favored the ICR as a consequence of its higher specific power. Assuming part load operation at variable speed and constant turbine exhaust temperature, the two spool ICR showed slightly better part load fuel economy than a recuperated engine.

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