Variable-structure control with complementarity-inputs for a lean-burn IC engine of a series hybrid vehicle

This paper presents a robust controller for an internal combustion (IC) engine, as the first stage of a project to develop a hybrid light urban vehicle, running on ethanol in lean burn. In particular, this work focuses on the design of a sliding mode control for an IC engine of a series hybrid power train. The controller must allow for optimal speed regulation and high fuel efficiency. To attain the latter, a complementary operation mode is proposed for the system inputs. Simulation results are presented and discussed showing the viability and advantages of the control strategy employed.Postprint (author's final draft

Review of modern low emissions combustion technologies for aero gas turbine engines

Pollutant emissions from aircraft in the vicinity of airports and at altitude are of great public concern due to their impact on environment and human health. The legislations aimed at limiting aircraft emissions have become more stringent over the past few decades. This has resulted in an urgent need to develop low emissions combustors in order to meet legislative requirements and reduce the impact of civil aviation on the environment. This article provides a comprehensive review of low emissions combustion technologies for modern aero gas turbines. The review considers current high Technologies Readiness Level (TRL) technologies including Rich-Burn Quick-quench Lean-burn (RQL), Double Annular Combustor (DAC), Twin Annular Premixing Swirler combustors (TAPS), Lean Direct Injection (LDI). It further reviews some of the advanced technologies at lower TRL. These include NASA multi-point LDI, Lean Premixed Prevaporised (LPP), Axially Staged Combustors (ASC) and Variable Geometry Combustors (VGC). The focus of the review is placed on working principles, a review of the key technologies (includes the key technology features, methods of realising the technology, associated technology advantages and design challenges, progress in development), technology application and emissions mitigation potential. The article concludes the technology review by providing a technology evaluation matrix based on a number of combustion performance criteria including altitude relight auto-ignition flashback, combustion stability, combustion efficiency, pressure loss, size and weight, liner life and exit temperature distribution

Design and simulation of high-performance hybrid electric vehicle powertrains

The intent of this study was the design, modeling, and simulation of several high-performance light-duty hybrid electric vehicle powertrains. The design requirements of each proposed configuration are to meet or exceed a set of performance baselines based on a composite set of particular high-performance conventional vehicles presently available, while demonstrating increased fuel efficiency over regulated government cycles.;Several hybrid powertrain configurations were studied; however, the most promising and feasible for production designs were selected for further modeling. All of the proposed designs are post-transmission parallel hybrids for primarily performance reasons, with the auxiliary motive power coming after the transmission, utilizing a modeled spark-ignited, Variable Valve Timing (VVT) equipped internal combustion engine. A control strategy has been developed for the operation of these powertrains for virtually any driving condition---the strategy was not optimized for any particular government regulated cycle. Computer simulations were performed to simulate both the performance and the fuel economy of the proposed vehicle designs.;The simulation results show that the fuel economy of the modeled hybrid vehicles exceeds that of the comparable conventional vehicles, as well as meeting or exceeding the performance requirements of the baseline vehicles by 12--23%. In addition the exhaust gas emissions may be reduced, compared to a conventional vehicle due to hybridization. All modeled components were selected from available off-the-shelf applications, and the selected designs were chosen to be readily mass-produced

Measured and Modeled Performance of a Spring Dominant Free Piston Engine Generator

Free Piston Engine Generators (FPEG) directly convert the reciprocating piston motion into electricity by using a linear alternator. Unlike conventional engines with piston motion restricted by a crankshaft mechanism, the FPEG piston motion is constrained by the energy available in the system. When stiff springs are considered in the design, the FPEG system attains high frequency with high power and efficiency. The main objective of this research was to model stiff spring-assisted FPEG system dynamics and performance accurately, and to apply the modeling results to the development of a 1kW, spark ignited, natural gas fueled, FPEG experimental prototype. The experimental data was further utilized to refine and improve the existing model. First, a MATLAB®/Simulink based multi-cycle numerical model was developed for single and dual cylinder FPEG systems to study the effects of major design parameters on FPEG dynamics and performance. When stiff springs were added, the dynamics became more sinusoidal and symmetric with respect to the initial starting position. For a total displacement of 34 cc, trapped compression ratio of 8.25, and assumed combustion efficiency of 95%, the modeled frequency and electric power varied from 72.3 Hz to 80.8 Hz and 0.81 kW to 0.88 kW for a single cylinder FPEG as the spring stiffness changed from 372 kN/m to 744 kN/m. For a dual cylinder FPEG with the same conditions, these modeled values changed from 76.8 Hz to 84.1 Hz and 1.7 kW to 1.8 kW with increasing spring stiffness. The numerical model was then expanded for sensitivity studies of major design parameters. When FPEG operating conditions were considered, the effective stroke length was found to have a dominant effect on efficiency followed by compression ratio, cylinder bore, and spring stiffness respectively. The experimental FPEG prototype generating 550 W of electricity with indicated efficiencies exceeding 13.8% was used for model validation. Finally, the stable FPEG system requires a control strategy to match the power generated by the engine to the power demanded by the alternator. A model-based control strategy was developed in Stateflow® for alternator mode switching, calibration maps, energy management, ignition and fuel injection timings. With the proposed control strategy and stiff spring dominance, the modeled and experimental FPEG system maintained stable operation with cycle-to-cycle variations less than 5%

New Trends on the Combustion Processes in Spark Ignition Engines

This Special Issue on "New Trends on the Combustion Processes in Spark Ignition Engines" contains nine papers on new developments on Internal Combustion (IC) engines aiming to enhance their efficiency, leading to the reduction of fossil CO2 and other gaseous pollutants. It is divided into two parts. In the initial part, the focus in on fuels, with four papers discussing the use of biofuels and other alternative fuels that can be used in different types of IC Engines. Additionally, conventional fuels are tested in order to evaluate their optimal use in new downsizing high-boost engines. A revision paper on alternative fuels is also included. The second part involves the study and improvement of engine combustion diagnostics as well as the presentation of an alternative type of propulsion system

Internal Combustion Engines and Powertrain Systems for future Transport 2019

Internal Combustion Engines and Powertrain Systems for Future Transport 2019 provides a forum for IC engine, fuels and powertrain experts, and looks closely at developments in powertrain technology required to meet the demands of the low carbon economy and global competition in all sectors of the transportation, off-highway and stationary power industries

A study of flame development with isooctane alcohol blended fuels in a optical spark ignition engine

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel UniversityThe work was concerned with experimental study of the turbulent flame development process of alcohol fuels, namely ethanol and butanol, in an optically accessed spark ignition research engine. The fuels were evaluated in a single cylinder engine equipped with full-bore overhead optical access operated at typical stoichiometric part-load conditions with images captured using high-speed natural light imaging techniques (or chemiluminescence). The differences in flame development between the fuels was analysed to understand better the impact of high and low alcohol content fuels on combustion. Advanced image analysis, in conjunction with Ricardo WAVE simulation, allowed for the conclusion that the faster burning exhibited by ethanol was the result of the marginally higher laminar burning velocity providing a faster laminar burn phase and accelerating the flame into the turbulent spectrum thus reducing bulk flame distortion and better in-cylinder pressure development. Such physical reactions are often over-looked in the face of chemical differences between fuels. A further study into the variation of maximum in-cylinder pressure values was conducted focussing on iso-octane and ethanol. This study identified two phenomena, namely “saw-toothing” and “creep” in which cluster of cycles feed into one another. From this it became clear that the presence of high pressure during the exhaust process had a large influence on the following cycles. This is another often overlooked phenomenon of direct cycle-to-cycle variation whereby incylinder pressures during blowdown can dictate the duration, load or stability output of the following cycle. Finally the work investigated the impact on flame development of alcohol fuels when the overlap duration was altered. While the engine produced counterintuitive figures of residual gas, ethanol was confirmed as having greater synergy with EGR by displaying less impacted combustion durations c.f. iso-octane. Care should be taken however when analysing these results due to the unique valve configuration of the engine.Thomas Gerald Gray Charitable Trust Scholarship Scheme and from the School of Engineering and Desig

The Scaling of Loss Pathways and Heat Transfer in Small Scale Internal Combustion Engines

Prior literature indicates fuel conversion efficiency and normalized power deteriorate increasingly rapidly with decreasing displacement, but does not fully reveal the driving losses. The literature also suggested that increasing losses relax the required fuel anti-knock index (AKI), but offered conflicting conclusions on the performance impact. This comprehensive experimental study of three, 28 cm3 to 85 cm3 displacement, commercial-off-the-shelf (COTS), two-stroke ICEs identified short-circuiting as having the most deleterious impact on COTS engine performance in this size range. Heat transfer losses were comparable to larger engines for displaced volumes greater than 10 cm3. An engine friction model was developed that uses the surface area to volume ratio, speed, and throttle to predict friction losses; a heat transfer model was also validated. The impact of reducing fuel AKI on performance was systematically investigated. The results showed a dependence on engine size; the fuel AKI requirement decreased 20 octane number between 85 cm3 and 28 cm3 displacement. Switching from 98 ON (manufacturer recommended) to 20 ON (JP-8, diesel equivalent) fuel increased power 2 -3 and fuel conversion efficiency by 0.5 -1 at non knock-limited conditions