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Advanced combustion engines dominate all automotive applications. Future high efficiency clean combustion engines can contribute significantly to sustainable transportation. Effective ignition strategies are studied to enable lean and diluted combustion under considerably high-density mixture and strong turbulences, for improving the efficiency and emissions of future combustion engines. Continuous discharge and multi-site ignition strategies have been proved to be effective to stabilize the combustion process under lean and EGR diluted conditions. Continuous discharge strategy uses a traditional sparkplug with a single spark gap and multiple ignition coil packs. The ignition coil packs operate under a specific time offset to realize a continuous discharge process with a prolonged discharge duration. Multi-site ignition strategy also uses multiple ignition coil packs.

The combustion of dual-fuel engines usually uses a pilot flame to burn out a background fuel inside a cylinder under high compression. The background fuel can be either a gaseous fuel or a volatile liquid fuel, commonly with low reactivity to prevent premature combustion and engine knocking; whereas the pilot flame is normally set off with the direct injection of a liquid fuel with adequate reactivity that is suitable for deterministic auto-ignition with a high compression ratio. In this work, directly injected butanol is used to generate the pilot flame, while intake port injected ethanol or butanol is employed as the background fuel. Compared with the conventional diesel-only combustion, dual-fuel operations not only broaden the fuel applicability, but also enhance the potential for clean combustion, in high efficiency engines. The amount of background fuel and the scheduling of pilot flame are investigated through extensive laboratory experiments.

Corona ignition is a promising technology that has been demonstrated to be capable of improving the reliability of lean combustion. However, arcing is unavoidable during corona discharge. The high current surge during arcing can cause excessive damage to the corona ignition system. In this work, a control framework is proposed to help reduce and prevent arcing from happening in a corona ignition system. Experimental results are demonstrated to show the effectiveness of the proposed methodology.

This empirical work investigates the impacts of thermodynamic parameters, such as pressure and temperature, and fuel properties, such as fuel Cetane number and aromatic contents on ignition delay in diesel engines. Systematic tests are conducted on a single-cylinder research engine to evaluate the ignition delay changes due to the fuel property differences at low, medium and high engine loads under different EGR dilution ratios. The test fuels offer a range of Cetane numbers from 28 to 54.2 and aromatic contents volume ratios from 19.4% to 46.6%. The experimental results of ignition delays are used to derive an ignition delay model modified from Arrhenius’ expression. Following the same format of Arrhenius’ equation, the model incorporates the pressure and temperature effects, and further includes the impacts of intake oxygen concentration, fuel Cetane number and aromatic contents volume ratio on the ignition delay.

This paper reports the results of two parallel investigations: An investigation on the solubility of alcohols in diesel fuels, and the diesel engine performance with the blended fuels. The investigation proposes an empirical formula for the solubility of alcohols in diesel fuels, as a function of temperature, water content, additive concentration and specific gravity of the diesel fuel. The engine performance when using the blended fuels was also investigated. Compared with conventional diesel fuels, the blended fuels show promise of better thermal efficiency, smoke free operation, and reduction of HC, NOx, and CO emissions.

Common-rail fuel systems have been recognized as an effective means to shape the heat release rate. In this paper measured cylinder pressure and fuel injection data for a common-rail diesel engine were analyzed to develop an empirical heat release rate model. A set of discrete Wiebe functions, one to describe the pilot injection combustion and the other to describe the main injection combustion, have been proposed to model the heat release data. The coefficients in the model were adjusted to match the observed heat release diagram. An expression for ignition delay for pilot injection and main injection has also been suggested for test conditions.

To overcome the unfavorable operation conditions caused by lean/diluted charges in modern Spark Ignited (SI) engines, various advanced ignition systems have been proposed in the past. Among them, the dual-coil and multi-coil Transistor Coil Ignition (TCI) systems with offset discharge strategy caused significant attention in literature because they can generate a continuous spark with high spark energy being delivered into the cylinder. Comparing with the dual-coil system, a multi-coil system is capable to apply more flexible control strategies and generate a higher discharge current. However, the spark energy and transfer efficiency of the multi-coil system are still worthy to investigate as they are important performance indicators for a TCI system. In this paper, the discharge characteristics of the dual-coil and triple-coil strategies under both quiescent and flow conditions were studied firstly by experimental methods.

Empirical and analytical investigations are conducted to evaluate the thermal response of exhaust pipe plenums at different levels of exhaust gas recirculation and through a variety of fuel delivery strategies. The effectiveness of different combustion control techniques is evaluated for moderating the engine-out exhaust temperature. Comparison of the external fuel injection with in-cylinder post injection for enabling aftertreatment is provided which indicates the stronger temperature raising potential of the external fuel injection. This research attempts to quantify the thermal response of the exhaust pipe plenums and its effects on the gas temperature at the inlet of the aftertreatment devices. The measurement and modeling of the dynamic thermal response in this research intend to improve the performance of diesel aftertreatment devices.

This report describes the possibility of quantitative analysis of Schlieren photographs as an internal combustion engine diagnostic. Using a recently developed photographic analysis system, it was attempted to analyze Schlieren photographs. Results showed simple integration calculations produced significant distortion in the analyzed results. To eliminate the distortion, some correction techniques were developed in this research. Accuracy of the analyzed results were evaluated roughly with uncertainty analysis. The results showed that this analysis technique can be one of the approximate diagnostics for the measurement of fuel vapor and density distribution in internal combustion engine research. SCHLIEREN photography is one of the most popular visualization techniques in the research of internal combustion engines. Although the photographs have density information in themselves, they are used mainly for the purpose of qualitative visualization.

The ever-growing demand to meet the stringent exhaust emission regulations have driven the development of modern gasoline engines towards lean combustion strategies and downsizing to achieve the reduction of exhaust emission and fuel consumption. Currently, the inductive ignition system is still the dominant ignition system applied in Spark Ignited (SI) engines. It is popular due to its simple design, low cost and robust performance. The new development in spark ignition engines demands higher spark energy to be delivered by the inductive ignition system to overcome the unfavorable ignition conditions caused by the increased and diluted in-cylinder charge. To meet this challenge, better understanding of the inductive ignition system is required. The development of a first principle model for simulation can help in understanding the working mechanism of the system in a better way.

In the present work, an attempt was made to predict engine noise from the shape of the burning rate curve. Thus, the influence of the shape of the burning rate curve on engine noise, especially on combustion noise was studied in detail and clarification of the relationship was successfully made. At first, an approximation of burning rate curve using a function was attempted. And in second, the transfer rate from cylinder pressure to combustion noise was obtained. Then, the relation between the deciding parameters of burning rate curve and noise and performance of engine were studied.

Advanced combustion engines, as power sources, dominate all aspects of the transportation sector. Stringent emission and fuel efficiency standards have promoted the research interest in advanced combustion strategies and alternative fuels. Owing to the comparable energy density to the existing fossil fuels and renewable production, alcohol and ether fuels may be a suitable replacement, or an additive to the gasoline/diesel fuels to meet the future emission standards with minimal modification to current engine geometry. Furthermore, lean and diluted combustion are well-researched pathways for efficiency improvement and reduction of engine-out emissions of modern engines. However, lean-burn or EGR dilution can introduce combustion inefficiencies in the form of excessive hydrocarbon, carbonyl species and carbon monoxide emissions.

Multi-spark discharge (MSD) ignition is widely used in high-speed internal combustion engines such as racing cars, motorcycles and outboard motors in attempts to achieve multiple sparks during each ignition. In contrast to transistor coil ignition (TCI) system, MSD system can be greatly shortened the charging time in a very short time. However, when the engine speed becomes higher, the ignition will be faster, electrical energy stored in the ignition system will certainly become less, especially for MSD system. Once the energy released into the spark plug gap can’t be guaranteed sufficiently, ignition will become more difficult, and it will get worse in some harsh environment such as strong turbulence or lean fuel conditions. With these circumstances, the risks of misfire and partial combustion will increase, which can deteriorate the power outputs and exhaust emissions of internal combustion engine.

Lean-burn engines now being developed employ in-cylinder injection which requires high pressures and so necessitates expensive injection equipment. The injection system proposed here is an air assisted in-cylinder injection system which is injecting a mixture of air and fuel in the cylinder during the intake stroke and allowing atomization at lower injection pressures than those necessary in compressing fuel with a usual solid injection. This time, the experiments used a testing engine of a 4 stroke gasoline OHV type replacing the Side Valve type. Performance with a small depression in the main combustion chamber was investigated with a spark plug and reed valve installed in the depression. The engine was operated then following the same method as last year (SAE 982698). As a result, the lean burn method employed here was possible over a wide range of engine speeds and loads. Moreover, it was also shown that this operation was possible with a fully opened throttle valve.

Dimethyl ether (DME) can be converted easily from methanol in a catalytic reactor, and it has very good compression ignition characteristics. This paper presents experimental results on a compression ignition methanol engine with DME as an ignition improver. The results show that engine operation is sufficiently smooth with high efficiency without spark or glow plugs. In the experiments, two methods for DME introduction were investigated: an aspiration and a torch ignition method. The aspiration method introduces DME into the intake manifold, and is structurally simple but suffers from poor emission characteristics at partial loads, and a large amount of DME is required for ignition. With the torch ignition method, DME is introduced into a torch ignition chamber during the intake stroke, and significant reductions in both the necessary DME quantity and emissions were obtained. Engine operation was also attempted with DME-dissolved methanol fuel without ignition aids.

Small two stroke SI engines supplied with natural gas in the intake port are advantageous for low maintenance and low cost when used in co-generation systems for residential use. However in the engines with port injection systems, the unburned HC emissions are higher and thermal efficiency is lower than with 4 stroke engines. To overcome these disadvantages, an in-cylinder injection with a special low pressure injection nozzle system was attempted. The results showed that improvements in unburned HC emissions and thermal efficiency are possible due to the remarkable reduction in scavenging loss and the lean combustion.

One-dimensional transient modeling techniques are adapted to analyze the thermal behavior of lean-burn after-treatment systems when active flow control schemes are applied. The active control schemes include parallel alternating flow, partial restricting flow, and periodic flow reversal (FR) that are found to be especially effective to treat engine exhausts that are difficult to cope with conventional passive flow converters. To diesel particulate filters (DPF), lean NOx traps (LNT), and oxidation converters (OC), the combined use of active flow control schemes are identified to be capable of shifting the exhaust gas temperature, flow rate, and oxygen concentration to more favorable windows for the filtration, conversion, and regeneration processes. Comparison analyses are made between active flow control and passive flow control schemes in investigating the influences of gas flow, heat transfer, chemical reaction, oxygen concentration, and converter properties.

Diesel fueling and exhaust flow strategies are investigated to control the substrate temperatures of diesel aftertreatment systems. The fueling control includes the common-rail post injection and the external supplemental fuel injection. The post injection pulses are further specified at the early, mid, or late stages of the engine expansion stroke. In comparison, the external fueling rates are moderated under various engine loads to evaluate the thermal impact. Additionally, the active-flow control schemes are implemented to improve the overall energy efficiency of the system. In parallel with the empirical work, the dynamic temperature characteristics of the exhaust system are simulated one-dimensionally with in-house and external codes. The dynamic thermal control, measurement, and modeling of this research intend to improve the performance of diesel particulate filters and diesel NOx absorbers.

Spark-assisted diesel engines operated with alcohol fuels usually display misfiring or knocking problems. This paper presents an analysis of the factors influencing the ignition characteristics of ethanol in a swirl chamber diesel engine with a multi-spark ignitor. In the experiments, cycle-to-cycle combustion variations and the degree of knocking were investigated by changing engine parameters over a wide operating range. The results of the investigations showed that stable ignition and smooth combustion is achieved when a flammable mixture is formed in the vicinity of the spark plug when only a small amount of the injected fuel has evaporated. By optimizing the design factors, operation with high efficiency and low exhaust emissions was achieved.

In this work, an active injection control strategy is developed for enabling clean and efficient combustion on an ethanol-diesel dual-fuel engine. The essence of this active injection control is the minimization of the diffusion burning and resultant emissions associated with the diesel injection while maintaining controllability over the ignition and combustion processes. A stand-alone injection bench is employed to characterize the rate of injection for the diesel injection events, and a regression model is established to describe the injection timings and injector delays. A new combustion control parameter is proposed to characterize the extent of diffusion burning on a cycle-to-cycle basis by comparing the modelled rate of diesel injection with the rate of heat release in real time. The test results show that the proposed parameter, compared with the traditional ignition delay, better correlates to the enabling of low NOx and low smoke combustion.