There has been an extensive worldwide search for alternate fuels that fit with the existing infrastructure and would thus displace fossil-based resources. In metabolic engineering work at Argonne National Laboratory, strains of fuel have been designed that can be produced in large quantities by photosynthetic bacteria, eventually producing a heavy alcohol called phytol (C 20 H 40 O). Phytol’s physical and chemical properties (cetane number, heat of combustion, heat of vaporization, density, surface tension, vapor pressure, etc.) correspond in magnitude to those of diesel fuel, suggesting that phytol might be a good blending agent in compression ignition (CI) engine applications. The main reason for this study was to investigate the feasibility of using phytol as a blending agent with diesel; this was done by comparing the performance and emission characteristics of different blends of phytol (5%, 10%, 20% by volume) with diesel. The experimental research was performed on a single-cylinder engine under conventional operating conditions. Since phytol’s viscosity is much higher than that of diesel, higher-injection-pressure cases were investigated to ensure the delivery of fuel into the combustion chamber was sufficient. The influence of the fuel’s chemical composition on performance and emission characteristics was captured by doing an injection timing sweep. Combustion characteristics as shown in the cylinder pressure trace were comparable for the diesel and all the blends of phytol at each of the injection timings. The 5% and 10% blends show lower CO and similar NO x values. However, the 20% blend shows higher NO x and CO emissions, indicating that the chemical and physical properties have been altered substantially at this higher percentage. The combustion event was depicted by performing high-speed natural luminosity imaging using endoscopy. This revealed that the higher in-cylinder temperatures for the 20% blend are the cause for its higher NO x emissions. In addition, three-dimensional simulations of transient, turbulent nozzle flow were performed to compare the injection and cavitation characteristics of phytol and its blends. Specifically, area and discharge coefficients and mass flow rates of diesel and phytol blends were compared under corresponding engine operating conditions. The conclusion is that phytol may be a suitable blending agent with diesel fuel for CI applications.

Spark ignition constitutes the most common way of mixture inflammation for gas engines of CHP units (combined heat and power). However, spark plug durability is limited due to spark erosion. High maintenance costs as a result of frequent spark plug replacements are the consequence. Beside the durability aspect, the inflammation of lean mixtures makes high demands on the inflammation process itself. Due to the small reactive mixture volume, the level of air-fuel ratio as well as the efficiency increase is limited. The ignition by means of a hot surface enables an increase of the reactive mixture volume and, as a result, an enhancement of the lean burn limit. A hot surface ignition (HSI) system was developed for stationary lean burn operation in due consideration of low manufacturing costs and electrical characteristics that allow a reliable control of the ignition timing. The main component of the inflammation element is a pin-shaped glow plug, whose temperature can be regulated by adjusting the electrical power. Due to external influences such as fluctuating ambient pressure and gas quality a control unit is essential for securing an optimal combustion phasing of the engine. Several designs of hot surface ignition, including passive prechamber and shielded versions, were tested on a single cylinder test bed engine operating with a homogeneous air-petrol mixture. The engine tests were accompanied by 3D flow simulations. The trials showed that the power consumption, and hence the temperature of the hot surface, as well as the flow conditions around the glow plug have a strong influence on the ignition timing. Furthermore, a strong correlation between the mean combustion chamber temperature and combustion phasing became evident. Based on this coherence, it was possible to develop a closed-loop control that adjusts the combustion phasing by controlling the combustion chamber temperature at a stationary operating point. The shielded inflammation element stood out to be the target-aiming version of hot surface ignition. It is characterised by an accelerated inflammation which allows reducing the cycle-to-cycle variations compared to prechamber spark ignition and, hence, to enhance the lean burn limit. As a result, a significant improvement of the efficiency-NO x trade-off is possible. The obtained results provide the basis for further trials on a gas engine CHP module operating with natural gas.

During research on diesel engine EGR cooler fouling a test stand giving visual access to the building deposit layer has been developed. Initial experiments reveal the presence of large particles in the exhaust. While conventional wisdom is that diesel particulates typically have log-normal size distributions ranging approximately 10–200 nm, the tests reported here observe small numbers of particles with sizes on the order of tens of μm. Such particles are not generally reported in the literature because exhaust particle sizing instruments typically have inertial separators to remove particles larger than ∼1 μm in order to avoid fouling of the nanoparticle measurement system. The test stand provides exhaust or heated air flow over a cooled surface with Reynolds number, pressure, and surface temperature typical of an EGR cooler. A window allows observation using a digital microscope camera. Starting from a clean surface, a rapid build of a deposit layer is observed. A few large particles are observed. These may land on the surface and remain for long times, although occasionally a particle blows away. In order to study these particles further, an exhaust sample was passed over a fiberglass filter, and the resulting filtered particles were analyzed. Samples were taken at the engine EGR passage, and also in the test stand tubing just before the visualization fixture. The resulting images indicate that the particles are not artifacts of the test system, but rather are present in engine exhaust. MATLAB routines were developed to analyze the filter images taken on the microscope camera. Particles were identified, counted, and sized by the software. It is not possible to take isokinetic samples and give quantitative measurement of the number and size distribution of the particles because the particles are large enough that inertial and gravitational effects will cause them to at least partially settle out of the flows. Nonetheless, the presence of particles tens of μm is documented. Such particles are probably the result of in-cylinder and exhaust pipe deposits flaking. While these larger particles would be captured by the diesel particulate filter (DPF), they can affect intake and exhaust valve seating, EGR cooler fouling, EGR valve sealing, and other factors.

Inner nozzle flow characteristics (e.g., cavitation, turbulence, injection velocity) are known to affect spray development and hence combustion and emissions. Our previous studies showed that petrodiesel and biodiesel (soybean-based fuels) had very different cavitation and turbulence characteristics, which caused differences in spray breakup, penetration, dispersion, etc. Specifically, the atomization characteristics of biodiesel were worse than those of diesel; they were a direct consequence of biodiesel’s reduced cavitation and turbulence levels at the nozzle exit. In this study, the nozzle flow characteristics of biodiesel (from different feedstocks like tallow, soy, rapeseed, cuphea, and hydrotreated vegetable oil [HVO]) were compared with those of diesel. The first step was to obtain data on the physical properties of these fuels (e.g., their density, viscosity, surface tension, vapor pressure) at different temperatures. At full-needle open position, the cavitation contours scaled with the vapor pressure and viscosity; hence, methyl esters such as soy (SME), rapeseed (RME), and tallow (TME) exhibited less cavitation. The nozzle discharge coefficient, exit velocity, turbulent kinetic energy, and dissipation rate at the orifice exit were also compared for these fuels. Transient effects due to needle movement upon the inception of cavitation were studied. The effects of different needle-lift profiles (pertaining to various load conditions) on the nozzle flow development of these fuels were also characterized. This study also provides data on the critical boundary conditions for spray simulations from using the Kelvin Helmholtz-aerodynamic cavitation turbulence (KH-ACT) model, which accounts for cavitation and turbulence-induced breakup in addition to aerodynamic breakup.

A first-order lumped-parameter model for the prediction of thermal behavior of a single-cylinder gasoline engine for Hybrid Electric Vehicles (HEVs) has been implemented. The model is coupled with a zero-dimension in-cylinder model that evaluates the working cycle of the engine according to the actual operating conditions and calculates the temperature of the exhaust gases, the overall efficiency of the engine and the exhaust gases flow rate. The model takes into account the possibility of using exhaust gas heat recirculation in order to enhance engine warm-up during cold start which improves its efficiency. The supervisory strategy takes into account not only predicted speed and ambient and road conditions along a future time window but also actual battery state of the charge and engine temperature to select the optimal power split between the ICE-generator group and the batteries. The proposed model represents an improvement with respect to a previous investigation of the authors where the temperature of the engine were assumed to increase/decrease of on Celsius degree in each seconds according to the state of the engine (ON/OFF).

Continued interest in kinetically-modulated combustion regimes, such as HCCI and PCCI, poses a significant challenge in controlling the ignition timing due to the lack of direct control of combustion phasing hardware available in traditional SI and CI engines. Chemical kinetic mechanisms, validated based on fundamental data from experiments like rapid compression machines and shock tubes, offer reasonably accurate predictions of ignition timing; however utilizing these requires high computational cost making them impractical for use in engine control schemes. Empirically-derived correlations offer faster control, but are generally not valid beyond the narrow range of conditions over which they were derived. This study discusses initial work in the development of an ignition correlation based on a detailed chemical kinetic mechanism for three component gasoline surrogate, composed of n-heptane, iso-octane and toluene, or toluene reference fuel (TRF). Simulations are conducted over a wide range of conditions including temperature, pressure, equivalence ratio and dilution for a range of tri-component blends in order to produce ignition delay time and investigate trends in ignition as pressure, equivalence ratio, temperature and fuel reactivity are varied. A modified, Arrhenius-based power law formulation will be used in a future study to fit the computed ignition delay times.

The HCCI combustion process is highly reliant upon a favorable in-cylinder thermal environment in an engine, for a given fuel. Commercial fuels can differ considerably in composition and auto-ignition chemistry, hence strategies intended to bring HCCI to market must account for this fuel variability. To this end, a test matrix consisting of eight gasoline fuels comprised of blends made solely from refinery streams were run in an experimental, single cylinder HCCI engine. All fuels contained 10% ethanol by volume and were representative of a cross-section of fuels one would expect to find at gasoline pumps across the United States. The properties of the fuels were varied according to research octane number (RON), sensitivity (S=RON-MON) and volumetric content of aromatics and olefins. For each fuel, a sweep of load (mass of fuel injected per cycle) was conducted and the intake air temperature was adjusted in order to keep the crank angle of the 50% mass fraction burned point (CA50) constant. By analyzing the amount of temperature compensation required to maintain constant combustion phasing, it was possible to determine the sensitivity of HCCI to changes in load for various fuels. In addition, the deviation of fuel properties brought about variations in important engine performance metrics like specific fuel consumption. Though the injected energy content per cycle was matched at the baseline point across the test fuel matrix, thermodynamic differences resulted in a spread of specific fuel consumption for the fuels tested.

Increasing strict regulation on the sulfur content of diesel fuels results in decreases the lubricity of these fuels. The lubricity of the fuel is an indication of the amount of wear or scarring that occurs between two metal parts covered with the fuel as they come in contact with each other. Low lubricity fuel may cause high wear and scarring and high lubricity fuel may provide reduced wear and longer component life. Previous studies have shown that alkyl esters of triglycerides derived from vegetable oils have increased diesel fuel lubricity at concentration of less than 1%. The major objective of this study was to analyze the effectiveness of indigenous non-edible feedstocks such as jatropha ( Jatropha curcas ) as an additive in petroleum based diesel fuels. Jatropha oil, and its alky esters (methyl and ethyl ester) and oil-ester blends with diesel were tested as an additive to enhance the lubricity of diesel fuels. In case of fuels, the lubricating behavior is associated with boundary film-forming properties. The analysis was carried out by using ASTM 6079-4 test method using High Frequency Reciprocating Rig (HFRR model D1377) as an analytical tool. The coefficient of friction and wear was observed higher for the low lubricity diesel fuel (LLDF) and it decreases with the addition of additive dose of oil, methyl and ethyl ester of jatropha. It may be due to the better lubricating behavior of non-edible based oil and ester compare to LLDF. During the HFRR test 2±0.20 ml of fluid sample under test is placed in reservoir which is maintained at a specified temperature of 60±2 °C. The HFRR test uses a vertically mounted steel ball to apply force to a horizontally mounted stationary steel disk with an applied load (200±1 g). The test ball is oscillated at a fixed frequency (50 ± 1 Hz) with a fixed stroke length (1 ± 0.02 mm) while the disk is fully immersed in the fluid reservoir. The whole test rig was placed in the humidity cabin with transparent enclosure. The test was kept for 75 minutes and the wear scar on the ball was measured by electronic microscope. It is believed that the high concentration of the particular fatty acid in oil and alkyl ester could be responsible for enhancing the lubricity and subsequent lower wear scar.

A predictive zero-dimensional low-throughput combustion model that was previously developed by the authors has been refined and applied to a EURO V diesel automotive engine. The model is capable of simulating, in real time, the time-histories of the HRR (Heat Release Rate), in-cylinder pressure, in-cylinder temperatures and NO x (nitrogen oxides) concentrations, on the basis of a few quantities estimated by the ECU (Engine Control Unit), such as the injection parameters, the trapped air mass, the intake manifold pressure and temperature. It has been developed for model-based feedforward control purposes in DI (Direct Injection) diesel engines featuring an advanced combustion system or new combustion-mode concepts, such as LTC/PCCI (Low Temperature Combustion/Premixed Charge Compression Ignition) engines. In the present work, the model has been assessed in detail by analyzing a wide set of experimental engine data that were acquired during the engine calibration phase. The experimental data set has been defined according to the DoE (Design of Experiment) methodology currently used for engine calibration purposes, and applied to six ‘key-points’ that are representative of engine working operations during an NEDC (New European Driving Cycle) for a D-class passenger car. Different injection strategies (pilot-main, double pilot-main; pilot-main-after; double pilot-main-after) have been considered for each key point, and all the main engine operating parameters (rail pressure, injected quantities, boost level, intake temperature, EGR rate,…) have been included in the DoE variation list. Therefore, about 1000 steady-state engine operating conditions have been investigated. In addition, several NEDC driving cycles have been realized with the engine installed on a dynamic test rig, and the combustion parameters and emission levels have continuously been measured during the transient operations. The model has been applied to all the investigated conditions. It has shown excellent accuracy in estimating the values of the main combustion parameters, and a good matching between the calculated and predicted NO x concentrations was found, for both steady-state and transient operations.

Over a significant period of time, efforts have been made towards a valid and accurate estimation of DI diesel engine NO x emissions. Considering the fact that experiments have a high cost in both time and money, modelling approaches have been developed in an effort to overcome these issues. It is well known that accuracy in the prediction of NO x emissions lies specifically on the accurate estimation of local temperature and O 2 histories inside the combustion chamber that govern NO x formation, fulfilled by an accurate estimation of the combustion mechanism. To account for the actual effect of parameters that control NO x formation and overcome inefficiencies introduced from existing purely empirical models or artificial neural networks, valid only on the combustion systems for which they were developed [1], an alternative solution is the introduction of physically based semi-empirical models. Towards this direction, in the present work is presented and evaluated a new modelling approach, based on the combustion rate obtained from the measured cylinder pressure trace using Heat Release Rate Analysis. The model used is a semi-empirical two-zone one which makes use of the estimated elementary fuel mass burnt at each crank angle interval. The combustion process is considered to be adiabatic, while chemical dissociation is also considered. With this approach, temperature distribution throughout the combustion chamber is considered for, together with its evolution during the engine cycle. In addition, O 2 availability is also considered for through the calculated charge composition. The result is an extremely fast computational model, combining the advantages of both empirical and physically based ones. In the present work is given a detailed validation of the model, from its application on two different types of diesel engines: a heavy-duty DI diesel engine and a light-duty DI diesel engine with pilot fuel injection. A significant number of cases where tested for both engine configurations, considering different operation points and variation of operating parameters, such as rail pressure and EGR. The twelve points of the European Stationary Cycle (ESC) were covered for the case of the heavy duty DI diesel engine, whilst for the light-duty DI engine a total number of forty-six operating points was studied. For both engine configurations the model reveals a very good predictive ability, considering for the effect of all operating parameters examined on NO x emissions. However, there is potential for improvement and development on its physical base for even more accurate predictions. The merits of good accuracy in prediction trends with varying engine operating parameters — even without calibration — and low computational time establish a potential for model use in engine development, optimization studies and model based control applications.

Variable displacement lubricant pumps allow oil flow to be matched to engine requirements over the whole operating range, reducing energy losses through excessive pumping work. An experimental investigation has been performed on-engine to understand the effects of such devices. Significant instrumentation was fitted to the production, EURO IV specification, 2.4L Diesel engine to assess the impacts of lubricant flow on thermal state. The reduced oil flow was measured as a reduction in engine oil pressure with the production pump supplying 4–6bar whereas the variable flow device provided pressures as low as 1–2bar. The reduction in oil flow significantly reduced the oil pump energy consumption, measured as a change in indicated work, resulting in a 4% benefit in fuel economy over both hot and cold start NEDC. The reduced oil flow also impacted oil and metal temperatures: during engine warm-up, oil temperatures were approximately 4°C colder with the lower flow as a result of less work input from the oil pump. Conversely, cylinder liner temperatures were 2–6°C hotter both during warm-up and fully warm conditions as a result of reduced piston cooling from piston cooling jets. The changes in thermal state were reflected by changes in emissions with a 3% increase in NO x and a 3–5% reduction in HC and CO. The calibration of the variable flow device follows a fuel consumption/NO x trade-off that is more favourable to fuel economy than conventional control parameters. However, these benefits are strongly linked to engine duty cycle with larger benefits at higher engine speeds.

The concept of a hybrid braking energy recoupment system was defined for coaches of diesel-hauled regional commuter trains. Functional specifications were developed having the goal of increasing by 25 percent the acceleration rate of a commuter train consisting of 10 bi-level coaches hauled by a 3,000 hp diesel locomotive, typical of the rolling stock now in service in Canada and the U.S.A. Because increasing train acceleration was the primary aim, the concept was named the Hybrid Augmented Traction System (HATS). Analyses of HATS simulations showed that in addition to augmenting acceleration and reducing trip time, braking energy recoupment reduced fuel consumption and corresponding diesel emissions. Examined were three alternate hybrid systems for train retardation by recoupment of braking energy, its storage and then regeneration based, respectively, on Hydrostatic, Battery and Ultracapacitor energy storage. The Ultracapacitor Hybrid system appeared the most promising due to the capability of ultracapacitors to repeatedly and rapidly accept large charges, be temperature insensitive and flexible in the placement of modules in the limited space available. The study foresees that HATS technology development could be expedited via the procurement process if railway operators specified braking energy recoupment requirements in calls-for-proposals for new capital equipment.

Naturally occurring thermal stratification significantly impacts the characteristics of HCCI combustion. The in-cylinder gas temperature distributions prior to combustion dictate the ignition phasing, burn rates, combustion efficiency, and unburned hydrocarbon and CO emissions associated with HCCI operation. Characterizing the gas temperature fields in an HCCI engine and correlating them to HCCI burn rates is a prerequisite for developing strategies to expand the HCCI operating range. To study the development of thermal stratification in more detail, a new analysis methodology for post-processing experimental HCCI engine data is proposed. This analysis tool uses the autoignition integral in the context of the mass fraction burned curve to infer information about the distribution of temperature that exists in the cylinder prior to combustion. An assumption is made about the shape of the charge temperature profiles of the unburned gas during compression and after combustion starts elsewhere in the cylinder. Secondly, it is assumed that chemical reaction rates proceed very rapidly in comparison to the staggering of ignition phasing from thermal stratification. The autoignition integral is then coupled to the mass fraction burned curve to produce temperature-mass distributions that are representative of a particular combustion event. Due to the computational efficiency associated with this zero-dimensional calculation, a large number of zones can be simulated at very little computational expense. The temperature-mass distributions are then studied over a coolant temperature sweep. The results show that very small changes to compression heat transfer can shift the distribution of mass and temperature in the cylinder enough to significantly affect HCCI burn rates and emissions.

An experimental investigation and a burning-rate analysis have been performed on a production 1.4 liter CNG (compressed natural gas) engine fueled with methane-hydrogen blends. The engine features a pent-roof combustion chamber, four valves per cylinder and a centrally located spark plug. The experimental tests have been carried out in order to quantify the cycle-to-cycle and the cylinder-to-cylinder combustion variation. Therefore, the engine has been equipped with four dedicated piezoelectric pressure transducers placed on each cylinder and located by the spark plug. At each test point, in-cylinder pressure, fuel consumption, induced air mass flow rate, pressure and temperature at different locations on the engine intake and exhaust systems as well as ‘engine-out’ pollutant emissions have been measured. The signals correlated to the engine operation have been acquired by means of a National Instruments PXI-DAQ system and a home developed software. The acquired data have then been processed through a combustion diagnostic tool resulting from the integration of an original multizone thermodynamic model with a CAD procedure for the evaluation of the burned-gas front geometry. The diagnostic tool allows the burning velocities to be computed. The tests have been performed over a wide range of engine speeds, loads and relative air-fuel ratios (up to the lean operation). For stoichiometric operation, the addition of hydrogen to CNG has produced a bsfc reduction ranging between 2 to 7% and a bsTHC decrease up to the 40%. These benefits have appeared to be even higher for lean mixtures. Moreover, hydrogen has shown to significantly enhance the combustion process, thus leading to a sensibly lower cycle-to-cycle variability. As a matter of fact, hydrogen addition has generally resulted into extended operation up to RAFR = 1.8. Still, a discrepancy in the abovementioned conclusions was observed depending on the engine cylinder considered.

This study investigates how injection timing affects combustion, NO x , PM mass and composition from a 2-stroke turbocharged locomotive diesel engine fitted with an early-development Tier 0+ emissions kit. The objective of the work is to gain insight into how injection timing affects combustion and emissions in this family of engines, modified to meet the newly implemented Tier 0+ emissions requirements, and to identify areas of potential future emissions reduction. For a range of injection timings at a medium load (notch 5) operating condition, the majority of PM mass is comprised of insolubles (81–89%), while the soluble component of PM (SOF) accounts for a smaller fraction (11–19%) of total PM mass. The SOF is 66–80% oil-like C 22 –C 30+ hydrocarbons, with the remainder being fuel-like C 9 –C 21 hydrocarbons. A heat release analysis is used to elucidate how injection timing affects combustion by calculating mass fraction burn curves. It is observed that retarding injection timing retards combustion phasing, decreases peak cylinder pressure and temperature, and increases expansion pressure and temperature. Results show that insolubles and fuel-like hydrocarbons increase and oil-like hydrocarbons decrease with later injection timing. Analysis suggests that insolubles and fuel-like HC increase due to lower peak combustion temperature, while oil-like HC, which are distributed more widely throughout the cylinder, decrease due to higher expansion temperatures. The net result is that total PM mass increases with retarded combustion phasing, mostly due to increased insolubles. Considering the high fraction of insoluble PM (81–89%) at all injection timings tested at notch 5, steps taken to reduce PM elemental carbon should be the most effective path for future reductions in PM emissions. Further reductions in oil consumption may also reduce PM, but to a smaller extent.

This article presents a summary of some experimental results obtained on a 1.4 MW CHP engine. Tests concern the effect of H 2 and CO addition to the natural gas at the engine inlet. Hydrogen and CO were obtained through the partial oxidation of methane. A honey-comb Platinum based catalyst was used for the partial oxidisation of methane. Part of the natural gas main stream was deviated and mixed with air to supply the catalyst. Catalyst output (mixture of H 2 , CO, H 2 O, CO 2 , N 2 and methane) are then mixed with the main stream of natural gas supplying the engine. Two different tests were conducted, the first one is an operation under a constant average combustion chamber temperature and the other one is an operation at a constant NO X level in the exhaust gases. Results showed a decrease of about 10% in NO X emissions when operating under constant combustion chamber temperature (this temperature is the average temperature of the four strokes inside the cylinders); and a slight increase of engine efficiency for a constant NO X emissions level.

The thermal efficiency of gas engines have been improved considerably in the last decade and now some of gas engines has achieved higher efficiency than diesel engines by introducing the state of the arts technologies. But at the same time, the abnormal combustion with the high peak firing pressure has been seen in recent years especially on high BMEP engines. This combustion has the unique characteristics such that it occurs temporally with the limited crank angle of advanced timing and the retarded spark ignition timing makes it worse. As the results of researches including the visualization tests on the single cylinder engine, this combustion was confirmed to be the kind of pre-ignition caused by the auto ignition of in-cylinder lubricating oil. And it was found to be one of the causes of the cyclic variation of peak firing pressure on premixed combustion gas engine. The lubricating oil can be ignited in the cylinder near the end of compression stroke where the temperature in cylinder is high enough for fuel oil to ignite. This is a natural phenomenon because the auto ignition temperature of lubricating oil is same level as that of fuel oil. But this phenomenon has not been considered so deeply so far because it has not caused serious combustion problems. But from now, more careful design by adding the view of the abnormal combustion caused by lubricating oil will be required for the future engines having the higher BEMP and thermal efficiency. Especially in case of gas engine ignited by fuel oil, such as Micro Pilot and Dual Fuel engine, the stable combustion window where combustion can be initiated and controlled not by lubricating oil but by fuel oil will become narrow. In this paper, the characteristics of this abnormal combustion on production engines and the visualization data of combustions measured on a test engine are introduced and then the consideration about the mechanism and the analysis of this phenomenon are described in detail.

Conventional combustion techniques struggle to meet the current emissions’ regulations while retaining high engine efficiency. Specifically in automotive diesel engines, oxides of nitrogen (NO x ) and particulate matter (PM) emissions have limited the utilization of diesel fuel in compression ignition engines. By comparison, throttled, knock-limited conventional gasoline operated SI engines tend not to be fuel efficient. Advanced combustion systems that simultaneously address PM and NO x while retaining the high efficiency of modern diesel engines, are being developed around the globe [1]. One of the most difficult problems in the area of advanced combustion technology development is the control of combustion initiation [2] and retaining power density [3]. During the past several years, significant progress has been accomplished in reducing emissions of NO x and PM through strategies such as LTC/HCCI/PCCI/PPCI and other advanced combustion processes; however control of ignition and improving power density has suffered to some degree — advanced combustion engines tend to be limited to the 10 bar BMEP range and under [4]. Experimental investigations have been carried out on a light duty, DI, multi cylinder, diesel automotive engine. The engine is operated in low temperature combustion technology with 87 RON (Research Octane Number) fuel [7]. Using an Ignition Quality Test (IQT) device, the equivalent Cetane Number (CN) was measured to be 25. In the present work, various EGR rates are examined to determine the effect on the combustion, emissions and performance. Experiments were conducted at three different engine load/speed combinations that are part of General Motors’ reference points for vehicle operation. To reduce the complexity, boost pressure and injection pressure and timing were kept constant while EGR percentage and intake temperature were used as parameters in this study. The intake temperature was not truly independent, as it trended with EGR level, but based upon the boost level and the available EGR cooling, Intake Air Temperature (IAT) was kept in the range of 40–80 deg C. Additional cooling capacity will be added in future work in an effort to keep IAT more consistent. EGR rates have a detrimental effect on engine efficiencies at lower load while it appears to have little effect on efficiency at higher loads. A more significant effect at very low load appears to be higher intake temperatures (hot EGR) as opposed to the very slight decrease in oxygen concentration.

A 2009 Volkswagen Jetta was tested using a Portable Emissions Measurement System (PEMS) SemtechD emissions analyzer to determine when the emissions and fuel consumption will be the smallest in regards to startup vs. idle emissions. An idle time equivalent was calculated to determine when idle emissions became equal to startup emissions at four different ambient temperatures for a cold start. The mass of Total Hydrocarbons (THC) emitted limited the idle time equivalent to less than the startup time for all ambient temperatures. The temperature of the Catalytic Converter (CC) was monitored to determine how quickly the car cools down and therefore, how beneficial it is to turn the car off after a certain time period. For the temperature range tested, it was more beneficial for reduced emissions to turn off the car compared to idling by a factor of at least four. The data suggests a trend that idling would never be the best option; however, more testing needs to be done with a greater range of CC cool down temperatures to confirm this initial assessment.

Homogeneous charge compression ignition (HCCI) has the potential to reduce both fuel consumption and NO x emissons compared to normal spark-ignited (SI) combustion. For a relatively low compression ratio engine, high unburned temperatures are needed to initiate HCCI combustion, which is achieved with large amounts of internal residual or by heating the intake charge. The amount of residual in the combustion chamber is controlled by a recompression valve strategy, which relies on negative valve overlap (NVO) to trap residual gases in the cylinder. A single-cylinder research engine with fully-flexible valve actuation is used to explore the limits of HCCI combustion phasing at a constant load of ∼3 bar IMEP g . This is done by performing two individual sweeps of a) internal residual fraction (via NVO) and b) intake air temperature to control combustion phasing. It is found that increasing both variables advances the phasing of HCCI combustion, which leads to increased NO x emissions and a higher ringing intensity. On the other hand, a reduction in these variables leads to greater emissions of CO and HC, as well as a decrease in combustion stability. A direct comparison of the two sweeps suggests that the points with elevated intake temperatures are more prone to ringing as combustion is advanced and less prone to instability and misfire as combustion is retarded. This behavior can be explained by compositional differences (air vs. EGR dilution) which lead to variations in burn rate and peak temperature. As a final study, two additional NVO sweeps are performed while holding intake temperature constant at 30°C and 90°C. Again, it is seen that at higher intake temperatures, combustion is more susceptible to ringing at advanced timings and more resistant to instability/misfire at retarded timings.