An investigation of the performance of a free-piston engine using Miller cycle and renewable fuels

A dual-piston type two-stroke spark-ignition free-piston engine prototype has been developed. A comprehensive review on recent published researches and patent documents from academia and industrial organizations on free-piston engine, especially the application of renewable fuels such as hydrogen and ethanol, was conducted. Relevant parameters affecting the operating performance and a number of challenges had been identified as the common denominator for this technology. Modelling and simulations using one-dimensional tools were conducted in parallel with the development activities. Three main simulation models for the crankshaft engines were developed, validated and optimised before converted into the free-piston engine model. This was done by using imposed-piston motion sub-model. The two-stroke free-piston engine model had undergone parametric study for valve timing optimisation. By using similar methods, a two-stroke hydrogen free-piston engine was developed from the prototype and it was validated by experimental data. Emission performance, along with the relationship between equivalent ratio, in-cylinder temperature and NOx emission on the hydrogen FPE was investigated. Series of ethanol-gasoline blend free-piston engine were developed, essential parameters such as compression ratio, air/fuel ratio and valve timing, etc., were amended for each model and both engine performance and emission performance were analysed. Miller cycle has been applied on three types of free-piston engine models: gasoline FPE, hydrogen FPE and ethanol FPE. Two types of Miller cycle (LIVC and EIVC) were both applied and analysed, and different late/early intake valve closing angles (from 5°CA to 35°CA) have been converted to specific time to apply on the free-piston engine. Engine performance and emission performance of Miller cycle free-piston engines have been obtained and individually presented. It turns out that large late/early intake valve closing angles (time) are not suitable in renewable free-piston engines due to the efficiency reduction

Hydrogen SI and HCCI Combustion in a Direct-Injection Optical Engine

Hydrogen has been largely proposed as a possible alternative fuel for internal combustion engines. Its wide flammability range allows higher engine efficiency with leaner operation than conventional fuels, for both reduced toxic emissions and no CO2 gases. Independently, Homogenous Charge Compression Ignition (HCCI) also allows higher thermal efficiency and lower fuel consumption with reduced NOX emissions when compared to Spark-Ignition (SI) engine operation. For HCCI combustion, a mixture of air and fuel is supplied to the cylinder and autoignition occurs from compression; engine is operated throttle-less and load is controlled by the quality of the mixture, avoiding the large fluid-dynamic losses in the intake manifold of SI engines. HCCI can be induced and controlled by varying the mixture temperature, either by Exhaust Gas Recirculation (EGR) or intake air pre-heating. A combination of HCCI combustion with hydrogen fuelling has great potential for virtually zero CO2 and NOX emissions. Nevertheless, combustion on such a fast burning fuel with wide flammability limits and high octane number implies many disadvantages, such as control of backfiring and speed of autoignition and there is almost no literature on the subject, particularly in optical engines. Experiments were conducted in a single-cylinder research engine equipped with both Port Fuel Injection (PFI) and Direct Injection (DI) systems running at 1000 RPM. Optical access to in-cylinder phenomena was enabled through an extended piston and optical crown. Combustion images were acquired by a high-speed camera at 1°or 2°crank angle resolution for a series of engine cycles. Spark-ignition tests were initially carried out to benchmark the operation of the engine with hydrogen against gasoline. DI of hydrogen after intake valve closure was found to be preferable in order to overcome problems related to backfiring and air displacement from hydrogens low density. HCCI combustion of hydrogen was initially enabled by means of a pilot port injection of n-heptane preceding the main direct injection of hydrogen, along with intake air preheating. Sole hydrogen fuelling HCCI was finally achieved and made sustainable, even at the low compression ratio of the optical engine by means of closed-valve DI, in synergy with air-pre-heating and negative valve overlap to promote internal EGR. Various operating conditions were analysed, such as fuelling in the range of air excess ratio 1.2-3.0 and intake air temperatures of 200-400°C. Finally, both single and double injections per cycle were compared to identify their effects on combustion development. Copyright © 2009 SAE International

Methanol as a fuel for internal combustion engines

Transportation of people and goods largely relies on the use of fossil hydrocarbons, contributing to global warming and problems with local air quality. There are a number of alternatives to fossil fuels that can avoid a net carbon emission and can also decrease pollutant emissions. However, many have significant difficulty in competing with fossil fuels due to either limited availability, limited energy density, high cost, or a combination of these. Methanol (CH3OH) is one of these alternatives, which was demonstrated in large fleet trials during the 1980s and 1990s, and is currently again being introduced in various places and applications. It can be produced from fossil fuels, but also from biomass and from renewable energy sources in carbon capture and utilization schemes. It can be used in pure form or as a blend component, in internal combustion engines (ICEs) or in direct methanol fuel cells (DMFCs). These features added to the fact it is a liquid fuel, making it an efficient way of storing and distributing energy, make it stand out as one of the most attractive scalable alternatives. This review focuses on the use of methanol as a pure fuel or blend component for ICEs. First, we introduce methanol historically, briefly introduce the various methods for its production, and summarize health and safety of using methanol as a fuel. Then, we focus on its use as a fuel for ICEs. The current data on the physical and chemical properties relevant for ICEs are reviewed, highlighting the differences with fuels such as ethanol and gasoline. These are then related to the research reported on the behaviour of methanol and methanol blends in spark ignition and compression ignition engines. Many of the properties of methanol that are significantly different from those of for example gasoline (such as its high heat of vaporization) lead to advantages as well as challenges. Both are extensively discussed. Methanol's performance, in terms of power output, peak and part load efficiency, and emissions formation is summarized, for so-called flex-fuel engines as well as for dedicated engines. We also briefly touch upon engine hardware changes and material compatibility. Methanol fuel reforming using engine waste heat is discussed, as a potential route towards further increases in efficiency and decreases in emissions. Next to the experimental work, research efforts into modelling the behaviour of methanol as a fuel are also reviewed, including mixture formation, normal and abnormal combustion. Methanol's properties such as high latent heat, fast burning velocity, high knock-resistance and no carbon-to-carbon bonds are shown to leverage engine technology developments such as increased compression ratios, downsizing and dilution; enabling much increased engine efficiencies. Finally, we point out the current gaps in knowledge to indicate which areas future research should be directed at

THIESEL 2020.Thermo-and Fluid Dynamic Processes in Direct Injection Engines.8th-11th September

'The THIESEL 2020 Conference on Thermo-and Fluid Dynamic Processes in Direct Injection Engines planned in Valencia (Spain) for 8th to 11th September 2020 has been successfully held in a virtual format, due to the COVID19 pandemic. In spite of the very tough environmental demands, combustion engines will probably remain the main propulsion system in transport for the next 20 to 50 years, at least for as long as alternative solutions cannot provide the flexibility expected by customers of the 21st century. But it needs to adapt to the new times, and so research in combustion engines is nowadays mostly focused on the new challenges posed by hybridization and downsizing. The topics presented in the papers of the conference include traditional ones, such as Injection & Sprays, Combustion, but also Alternative Fuels, as well as papers dedicated specifically to CO2 Reduction and Emissions Abatement.Papers stem from the Academic Research sector as well as from the IndustryXandra Marcelle, M.; Desantes Fernández, JM. (2020). THIESEL 2020.Thermo-and Fluid Dynamic Processes in Direct Injection Engines.8th-11th September. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/150759EDITORIA

Synthesis gas as a fuel for internal combustion engines in transportation

© 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).The adverse environmental impact of fossil fuel combustion in engines has motivated research towards using alternative low-carbon fuels. In recent years, there has been an increased interest in studying the combustion of fuel mixtures consisting mainly of hydrogen and carbon monoxide, referred to as syngas, which can be considered as a promising fuel toward cleaner combustion technologies for power generation. This paper provides an extensive review of syngas production and application in internal combustion (IC) engines as the primary or secondary fuel. First, a brief overview of syngas as a fuel is presented, introducing the various methods for its production, focusing on its historical use and summarizing the merits and drawbacks of using syngas as a fuel. Then its physicochemical properties relevant to IC engines are reviewed, highlighting studies on the fundamental combustion characteristics, such as ignition delay time and laminar and turbulent flame speeds. The main body of the paper is devoted to reviewing the effect of syngas utilization on performance and emissions characteristics of spark ignition (SI), compression ignition (CI), homogeneous charge compression ignition (HCCI), and advanced dual-fuel engines such as reactivity-controlled compression ignition (RCCI) engines. Finally, various on-board fuel reforming techniques for syngas production and use in vehicles are reviewed as a potential route towards further increases in efficiency and decreases in emissions of IC engines. These are then related to the research reported on the behavior of syngas and its blends in IC engines. It was found that the selection of the syngas production method, choice of the base fuel for reforming, its physicochemical properties, combustion strategy, and engine combustion system and operating conditions play critical roles in dictating the potential advantages of syngas use in IC engines. The discussion of the present review paper provides valuable insights for future research on syngas as a possible fuel for IC engines for transport.Peer reviewe

Diesel and Gasoline Engines

The internal combustion engine was invented around 1790 by various scientists and engineers worldwide. Since then the engines have gone through many modifications and improvements. Today, different applications of engines form a significant technological importance in our everyday lives, leading to the evolution of our modern civilization. The invention of diesel and gasoline engines has definitely changed our lifestyles as well as shaped our priorities. The current engines serve innumerable applications in various types of transportation, in harsh environments, in construction, in diverse industries, and also as back-up power supply systems for hospitals, security departments, and other institutions. However, heavy duty or light duty engines have certain major disadvantages, which are well known to everyone. With the increasing usage of diesel and gasoline engines, and the constantly rising number of vehicles worldwide, the main concern nowadays is engine exhaust emissions. This book looks at basic phenomena related to diesel and gasoline engines, combustion, alternative fuels, exhaust emissions, and mitigations

Research on The Ultra-Low Emission Technology in Internal Combustion Engine

Increasing the efficiency of internal combustion engines is a technologically proven and cost effective approach to dramatically improving the fuel economy of the nation’s fleet of vehicles in the near- to midterm, with the corresponding benefits of reducing our dependence on foreign oil and reducing carbon emissions. This review paper discusses on the research of ultra-low emission technology in internal combustion engine. Efficiency can be increased by improving combustion processes, minimizing engine losses such as friction, reducing the energy penalty of the emission control system and using recovered waste energy in propulsion. Compliance with exhaust emission regulations will be mandated and requires after-treatment technologies integrated with the engine combustion approaches. Fuels under consideration include hydrocarbon-based. Because of their relatively low cost, high performance, and ability to utilize renewable fuels, internal combustion engines, including those in hybrid vehicles, will continue to be critical to our transportation infrastructure for decades

Current Status of Research on Methanol as an Alternative Fuel to Conventional Fuels

With the rapid development of China's economy and society, the domestic demand for automobiles is growing explosively. At the same time, the dependence of China's crude oil on foreign countries exceeds 65%. This is a great hidden danger to the sustainable development of China's economy and energy security. Automobile consumes a large amount of petroleum resources, and automobile exhaust is one of the main factors causing environmental pollution. In view of the dual pressure of energy saving and emission reduction, methanol has been favored by many researchers for its many advantages (such as cleanliness, environmental protection, renewable and high accessibility). In this paper, the resource extensibility of methanol, the physicochemical properties of methanol, the application characteristics of methanol in internal combustion engine and the comparison of the combustion performance of methanol with traditional fuels are summarized and analyzed. Citation: Lan, D. (2022). Current status of research on methanol as an alternative fuel to gasoline. Trends in Renewable Energy, 9, 22-33. DOI: 10.17737/tre.2023.9.1.0014

A study of controlled auto ignition (CAI) combustion in internal combustion engines

Controlled Auto Ignition (CAI) combustion is a new combustion principle in internal combustion engines which has in recent years attracted increased attention. In CAI combustion, which combines features of spark ignition (SI) and compression ignition (CI) principles, air/fuel mixture is premixed, as in SI combustion and auto-ignited by piston compression as in CI combustion. Ignition is provided in multiple points, and thus the charge gives a simultaneous energy release. This results in uniform and simultaneous auto-ignition and chemical reaction throughout the whole charge without flame propagation. CAI combustion is controlled by the chemical kinetics of air/fuel mixture with no influence of turbulence. The CAI engine offers benefits in comparison to spark ignited and compression ignited engines in higher efficiency due to elimination of throttling losses at part and idle loads. There is a possibility to use high compression ratios since it is not knock limited, and in significant lower NOx emission (≈90%) and particle matter emission (≈50%), due to much lower combustion temperature and elimination of fuel rich zones. However, there are several disadvantages of the CAI engine that limits its practical application, such as high level of hydrocarbon and carbon monoxide emissions, high peak pressures, high rates of heat release, reduced power per displacement and difficulties in starting and controlling the engine. Controlling the operation over a wide range of loads and speeds is probably the major difficulty facing CAI engines. Controlling is actually two-components as it consists of auto-ignition phasing and controlling the rates of heat release. As CAI combustion is controlled by chemical kinetics of air/fuel mixture, the auto-ignition timing and heat release rate are determined by the charge properties such as temperature, composition and pressure. Therefore, changes in engine operational parameters or in types of fuel, results in changing of the charge properties. Hence, the auto-ignition timing and the rate of heat release. The Thesis investigates a controlled auto-ignition (CAI) combustion in internal combustion engines suitable for transport applications. The CAI engine environment is simulated by using a single-zone, homogeneous reactor model with a time variable volume according to the slider-crank relationship. The model uses detailed chemical kinetics and distributed heat transfer losses according to Woschini's correlation [1]. The fundamentals of chemical kinetics, and their relationship with combustion related problems are presented. The phenomenology and principles of auto-ignition process itself and its characteristics in CAI combustion are explained. The simulation model for representing CAI engine environment is established and calibrated with respect to the experimental data. The influences of fuel composition on the auto-ignition timing and the rate of heat release in a CAI engine are investigated. The effects of engine parameters on CAI combustion in different engine concepts fuelled with various fuels are analysed. The effects of internal gas recirculation (IEGR) in controlling the auto-ignition timing and the heat release rate in a CAI engine fuelled with different fuels are investigated. The effects of variable valve timings strategy on gas exchange process in CAI engine fuelled with commercial gasoline (95RON) are analysed

Fuel consumption and engine-out emissions estimations of a light-duty engine running in dual-mode RCCI/CDC with different fuels and driving cycles

[EN] This work compares the performance and emissions of two dual-mode combustion concepts over different driving cycles by means of vehicle systems simulations. The dual-mode concept relies on switching between the dual-fuel concept known as reactivity controlled compression ignition (RCCI) and conventional diesel combustion (CDC) to cover the whole engine map. The experimental RCCI maps obtained with diesel-E85 and diesel-gasoline used as inputs to perform the simulations were obtained in a high compression ratio light-duty diesel engine (17.1:1) following the same mapping procedure in both cases. The driving cycles simulated to perform the comparison were the Real Driving Emissions cycle (Europe), Worldwide harmonized Light vehicles Test Cycle (Europe), Federal Test Procedure FTP-75 (United States) and JC08 (Japan). The results show that the dual-mode concept has potential to be implemented in flexible-fuel vehicles. Using gasoline as low reactivity fuel (LRF) for RCCI, the vehicle mileage would be equal to CDC, but having reductions in NOx and soot emissions of 16% and 50%, respectively, along the RDE cycle. Using E85 instead of gasoline, the reductions in NOx and soot emissions increase up to 50% and 85%, respectively, but in this case promoting higher thermal efficiency than CDC. (C) 2018 Elsevier Ltd. All rights reserved.The authors gratefully acknowledge General Motors Global Research & Development for providing the engine used to acquire the experimental data shown in this investigation. The authors also acknowledge FEDER and Spanish Ministerio de Economia y Competitividad for partially supporting this research through HiReCo project (TRA2014-58870-R).Benajes, J.; García Martínez, A.; Monsalve-Serrano, J.; Lago-Sari, R. (2018). Fuel consumption and engine-out emissions estimations of a light-duty engine running in dual-mode RCCI/CDC with different fuels and driving cycles. Energy. 157:19-30. https://doi.org/10.1016/j.energy.2018.05.144S193015