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.

Over the two last decades, gaseous and particle mass emissions of new diesel engines have been reduced effectively and progressively in response to the emissions legislation and due to the applied new technologies. There is, however, increasing concern about whether the engine modifications, while improving combustion and reducing emissions, have increased the number emissions of ultrafine and nanoparticles. So far, emissions regulations have solely been based on particulate matter (PM) mass measurements, not on particle number. Nanoparticles, however, form a major part of the PM emissions, but they do not considerably contribute to the PM mass and can not be seen as a problem, if only PM mass is determined. Therefore, there is increasing interest in expanding the scope of the regulations to also include particle number emissions, e.g. Euro VI for on-road engines. The PM number limit will also be enforced for non-road engines slightly later. Thus, more information is required about the particle number emissions themselves, but also about the effects of the engine technology on them. Wall-flow diesel particulate filters (DPFs) reduce the particle number very effectively within the entire particle size range. Nevertheless, in order to keep the DPF as small as possible and to lessen the need for regeneration, the engine-out PM number should also be minimized. If the DPF could be left out or replaced by a simpler filter, there would be greater freedom of space utilization or cost savings in many non-road applications. This might be realized in installations where the engine is tuned at high raw NO x and an SCR system is adopted for NO x reduction. However, it is not self-evident that new engine technologies would reduce the PM number emissions sufficiently. In this study, particle number emissions were analyzed in several non-road diesel engines representing different engine generations and exploiting different emissions reduction technologies: 4- or 2-valve heads, exhaust gas recirculation (EGR), different injection pressures and strategies, etc. All engines were turbocharged, intercooled, direct-injection non-road diesel engines. Most engines used common-rail fuel injection technology. Comparisons were, however, also performed with engines utilizing either a distributor-type or an in-line fuel injection pump to see the long-term development of the particle number emissions. In this paper, the PM number emissions of nine (9) non-road diesel engines are presented and compared. Gaseous exhaust emissions and fuel consumption figures are also provided.

Diesel low temperature combustion (LTC) is capable of producing diesel-like efficiency while emitting ultra-low nitrogen oxides (NOx) and soot emissions. Previous work indicates that well controlled single-shot injection with exhaust gas recirculation (EGR) is an operative way of achieving diesel LTC from low to mid engine loads. However, as the engine load is increased, demanding intake boost and injection pressure are necessary to suppress high soot emissions during the transition to LTC. The use of volatile fuels such as ethanol are deemed capable of promoting the cylinder charge homogeneity, which helps to overcome the high soot challenge and thus potentially expand the engine LTC load range. In this work, LTC investigations have been carried out on a high compression ratio (18.2:1) engine. The engine was firstly fuelled with diesel, and LTC operation at 8 bar indicated mean effective pressure (IMEP) was enabled by sophisticated control of the injection pressure, injection timing, intake boost and EGR application. The engine performance was characterized as the baseline, and the challenges were identified. Further tests were aimed to improve the engine performance against these baseline results. Experiments were hence conducted on the same engine with secondary ethanol port injection (PI). Single-shot diesel direct injection (DI) was applied close to top dead center (TDC) to ignite the ethanol and control the combustion phasing. The control sensitivity has been studied through injection timing sweeps and EGR sweeps. Additional tests were performed to investigate the ethanol-to-diesel ratio effects on the mixture reactivity and the engine emissions. Engine load was also raised to 10 bar IMEP while keeping the simultaneously low NOx and soot emissions. Significant improvement of engine control and emissions was achieved by the DI+PI strategy.

This study describes the effects of two-stage combustion (TSC) strategy on combustion and emission characteristics in 4 cylinder common-rail direct injection (CRDI) diesel engine fueled with biodiesel blends. In the present work, to investigate the combustion and emission characteristics, the experiments were performed under various injection pressures, first injection quantity and first injection timing of TSC strategy at constant engine speed and engine load. In addition, conventional diesel fuel (ULSD) was used to compare with biodiesel blends. The experimental results show that combustion of biodiesel blends is stable for various test conditions regardless of blending ratio, and indicated specific fuel consumption (ISFC) was increased as biodiesel blending ratio increased. In the emission characteristics, biodiesel blends generated lower indicated specific nitrogen oxides (IS-NOx) and indicated specific soot (IS-Soot) emissions compared to those of ULSD when the first injection quantity increased.

Ultra-fast emission measurements can provide important information about the combustion system of an engine, especially during its development phase. The ability to measure NOx as soon as it exits the cylinder provides an insight to engine designers and combustion engineers about the in-cylinder process with regards to formation of NOx emissions. There are mainly two areas where such information can be used. First, the fast measurements can be used for the tuning of CFD models that are used during the development phase of an engine. Secondly, such a method could be useful in the first phases of engine testing during the development of the combustion system where engine tuning could lead to an overall superior compromise between an engine’s fuel economy and emission behaviour. The current research work investigated the potential of performing ultra-fast emission measurements in the exhaust port, immediately downstream of the exhaust valve, of a specified engine cylinder of a two-stroke large engine. A methodology was therefore developed and tested, by which emission measurements with fast temporal response can be conducted for individual engine cylinders. More specifically, an ultra-fast NOx measurement sampling probe was designed and developed to be applied mainly to 2-stroke engines, with the flexibility to also be applicable to 4-stroke engines. The development of the sampling system was done by initially performing NO measurements on the 4-stroke MAN L16/24 research engine, installed at the test bed of the Laboratory of Marine Engineering (LME), at the National Technical University of Athens (NTUA). Once developed, the final fast sampling system was then used for measurements of NO at the exhaust port of the 2-stroke MAN 4T50ME-X engine, at the MAN Diesel & Turbo test-centre in Copenhagen. The employed NO emissions measurement method provided the results on a cycle-by-cycle basis, and also as phase averaged values. The extremely fast response time of the instrument captured important details of the NO concentration in the exhaust gases, as soon as they exit the cylinder.

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.

A two-degree freedom air fuel ratio controller (Model based feed forward transient plus closed loop Proportional-Integral-Derivative (PID) steady state controllers) developed for controlling the air fuel ratio of the charge in a small displacement (125 CC) SI engine is presented. The feed forward controller’s airflow and injector models were developed after conducting extensive experiments on the engine modified for the Port Fuel Injection (PFI) operation. A dynamic air fuel ratio model obtained (air fuel ratio changes measured using an UEGO sensor) by injecting the Pseudo Random Binary Signal (PRBS) signal in addition to base line fuel injection pulse, was used for designing the PID controller. Optimal PID gain values were identified using Nelfer-Mead optimization technique. The control algorithms were implemented and optimized using SIMULINK blocks that are run under dSPACE on the MicroAuto box hardware. The optimized control algorithms were ported on the specially designed, in-house built, low cost engine management system (EMS) developed around an 8-bit microcontroller. The spark timing was also controlled simultaneously for knock free operation. The two-degree freedom air fuel ratio controller could maintain the air fuel ratio under steady and transient conditions closely. High thermal efficiency and low HC & NOx emissions were achieved using the developed EMS. At higher speed elevated NOx emission was observed, due to the use of leaner mixture. The improvements are expected to be higher if a suitable smaller injector is used.

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.

Advanced premixed compression ignition (CI) combustion using fumigation has been shown to yield significant improvements in indicated efficiency over traditional diesel combustion strategies while simultaneously reducing engine-out soot and NO X emissions. To better interpret these findings, a breakdown of the ways in which actual performance deviates from ideal engine cycles is helpful. Non-ideal combustion phasing is one cause of such deviations. In this paper, the centroid of the calculated apparent heat release rate is used to estimate an adjusted maximum possible thermal efficiency based on constant volume combustion using an effective compression ratio concept. Using these metrics, experimental engine data are evaluated from a single cylinder direct-injection diesel engine operating in premixed CI mode enabled by gasoline fumigation and a diesel pilot injection. Indicated gross cycle efficiency was found to be higher for premixed fumigation compared with a conventional diesel condition at the same load. A key finding of the work is that the peak indicated cycle efficiency for fumigated premixed CI combustion occurs with combustion phased very close to TDC. Shorter heat release duration and lower heat losses from the cylinder are thought to be the cause of differences in cycle efficiency between conventional combustion and premixed CI fumigation modes.

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.

Hybrid Electric Vehicles (HEVs) can be considered one of the most promising ways of improving the sustainability of the road transport sector. They are equipped with an Internal Combustion Engine (ICE) coupled to an electro-mechanical system. This study has focused on a parallel-hybrid diesel powertrain featuring a high-voltage Belt Alternator Starter (BAS). This layout allows regenerative braking, Stop&Start, load point shift and electric power assistance to the ICE. However, a dedicated optimization of the operating strategy is required to exploit all the expected advantages of the considered HEV. The project has entailed the implementation of a zero-dimensional model of the hybrid powertrain in GT-Drive and Matlab environments. Genetic Algorithm (GA) based techniques have been used to define a novel benchmark operating strategy and to calibrate a real-time optimizer. The benchmark and real-time optimization approaches have been applied to reduce the total FC and NO x emissions as well as to diminish the local combustion noise peaks. Different mission profiles have been considered, i.e. the New European Driving Cycle (NEDC) and three Artemis driving routes. The results show the effectiveness of the proposed methods and the improvements obtained in fuel economy, NO x emissions and combustion noise.

Diesel engines are almost exclusively used for propulsion of marine vessels. They are also used for power generation either on vessels or power stations because of their superior efficiency, high power concentration, stability and reliability compared to other alternative power systems. However, a significant drawback of these engines is the production of exhaust gases some of which are toxic and thus can be a threat to the environment. The most important toxic gaseous pollutants found in the exhaust gas of a marine diesel engine are NOx (NO, NO 2 etc), CO and SOx. Particulate matter is also a major pollutant of diesel. Currently CO 2 is considered to be also a “pollutant”, even though not being directly toxic, due to its impact on global warming. In the Marine sector there exists legislation for marine diesel engine NOx emissions which is getting stricter as we move on towards Tier III. This brings new challenges for the engine makers as far as NOx control and its reduction is concerned. Towards this effort of NOx reduction, modelling has an important role which will become even more important in the future. This is mainly attributed to the large size of marine engines which makes the use of experimental techniques extremely expensive and time consuming. Modelling can greatly assist NOx reduction efforts at least at the early stages of development leading to cost reduction. As known NOx emissions are strongly related to engine performance and thus efforts for their reduction usually have a negative impact on efficiency and particulate matter. Modelling can play an important role towards this direction because optimization techniques can be applied to determine the optimum design for NOx reduction with the lowest impact on efficiency. At present an effort is made to apply an existing well validated multi-zone combustion model for DI diesel engines on a 2-stroke marine diesel engine used to power a tanker vessel. The model is used to determine both engine performance and NOx emissions at various operating conditions. To validate model’s ability to predict performance and NOx emissions, a comparison is given against data obtained from the vessel official NOx file and from on board measurements conducted by the present research group. On board performance measurements were conducted using an in-house engine diagnostic system while emissions were recorded using a portable exhaust gas analyzer. From the comparison of measured against predicted data, the ability of the model to adequately predict performance and NOx emissions of the slow speed 2-stroke marine diesel engine examined is demonstrated. Furthermore, from the application are revealed specific problems related to the application of such models on large slow speed two-stroke engines which is significantly important for their further development.

Pipeline natural gas composition is monitored and controlled in order to deliver high quality, relatively consistent gas quality in terms of heating value and detonation characteristics to end users. The consistency of this fuel means gas-fired engines designed for electrical power generation (EPG) applications can be highly optimized. As new sources of high quality natural gas are found, the demand for these engines is growing. At the same time there is also an increasing need for EPG engines that can handle fuels that have wide swings in composition over a relatively short period of time. The application presented in this paper is an engine paired with an anaerobic digester that accepts an unpredictable and varying feedstock. As is typical in biogas applications, there are exhaust stream contaminants that preclude the use of an oxygen or NO x sensor for emissions feedback control. The difficulty with such a scenario is the ability to hold a given exhaust gas emission level as the fuel composition varies. One challenge is the design of the combustion system hardware. This design effort includes the proper selection of compression ratio, valve events, ignition timing, turbomachinery, etc. Often times simulation tools, such as a crank-angle resolved engine model, are used in the development of such systems in order to predict performance and reduce development time and hardware testing. The second challenge is the control system and how to implement a robust control capable of optimizing engine performance while maintaining emissions compliance. Currently there are limited options for an OEM control system capable of dealing with fuels that have wide swings in composition. Often times the solution for the engine packager is to adopt an aftermarket control system and apply this in place of the control system delivered on the engine. The disadvantage to this approach is that the aftermarket controller is not calibrated and so the packager is faced with the task of developing an entire engine calibration at a customer site. The controller must function well enough that it will run reliably during plant start-up and then eventually prove capable of holding emissions under typical operating conditions. This paper will describe the novel use of a crank-angle resolved four-stroke engine cycle model to develop an initial set of calibration values for an aftermarket control system. The paper will describe the plant operation, implementation of the aftermarket controller, the model-based calibration methodology and the commissioning of the engine.

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.

To satisfy the Tier-4 requirements EMD as well as other large engine manufacturers are investigating the emission reduction potentials of different technologies whether they are application ready or in concept stage. One of the recent trends is to use dedicated cylinders as EGR gas suppliers. In this study the NOx reduction potential of dedicated cylinders for the two-cycle EMD 16-710 engine is evaluated analytically. The performance of the well known and documented 16-710 T-2 engine is chosen as the base case. An analytical model is developed to simulate the engine operation by using the commercially available GT-Power code. Model parameters are adjusted to fit predictions to test data. The base model is then modified for a high pressure cooled EGR system. The system parameters are changed to optimize the system for selected criteria. Predicted performance of the system is compared against the base case. The system model with EGR is further modified to accommodate the use of dedicated cylinders as the gas supplier to the EGR loop. The following dedicated cylinder variables are changed to optimize the system performance for NOx reductions; (a). Number of dedicated cylinders, (b). Location of dedicated cylinders, (c). Dedicated cylinder’s flow rate (EGR rate), (d). Compression ratio, (e). Injection timing, (f). Valve timing, (g). Valve lift profile, (h). Valve opening and closing times. Predicted results are compared against cases with and without EGR. The study demonstrates that a 3-cylinder dedicated system, supplying the EGR gases, has the potential to reduce the tailpipe BSNOx below Tier-4 emissions level at Notch 8 operation condition of the engine. The study also suggests that designing the dedicated cylinders as if they are a different engine, for BHP while designing the normal cylinders to reduce BSNOx can be a successful strategy. During this study the basic mechanisms of EGR in reducing the engine NOx is classified into three groups. It is shown that the Flow Diversion Effect of EGR can be above 40% of total BSNOx reduction.

The PR30C-LE is a repowered six-axle, 2,240 kW (3,005 hp), line-haul locomotive that was introduced to the rail industry in 2009. The Caterpillar 3516C-HD Tier 2 engine is equipped with an exhaust aftertreatment module containing selective catalyst reduction (SCR) and diesel oxidation catalyst (DOC) technology. PR30C-LE exhaust emission testing was performed on test locomotive PRLX3004. Phase-1 of the test program included the following tasks: engine-out baseline emissions testing without the aftertreatment module installed, aftertreatment module installation, commissioning and degreening, and emissions testing with the aftertreatment. Emission results from testing without the aftertreatment module, referred to as the baseline configuration, indicated that PRLX3004 emissions were below Tier 2 EPA locomotive limits without aftertreatment. Emission test results with the DOC and SCR aftertreatment module showed a reduction in nitrogen oxides (NO x ) of 80 percent over the line-haul cycle, and 59 percent over the switcher cycle. Particulate matter (PM) was reduced by 43 percent over the line-haul cycle and 64 percent over the switcher cycle. Line-haul cycle composite emissions of Hydrocarbon (HC) and carbon monoxide (CO) were reduced by 93 and 72 percent, respectively. The PR30C-LE locomotive achieved Tier 4 line-haul NO x , CO, HC, as well as Tier 3 PM levels. There are currently five PR30C-LE locomotives in operation in California and Arizona, and the total hour accumulation of the five PR30C-LE locomotives as of October 2011 was 20,000 hours.

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.

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.

Dual fuel pilot ignited natural gas engines are identified as an efficient and viable alternative to conventional diesel engines. This paper examines cyclic combustion fluctuations in conventional dual fuel and in dual fuel partially premixed low temperature combustion (LTC) at 1700 rev/min and 6 bar brake mean effective pressure (bmep). Conventional dual fueling with 95% (energy basis) natural gas (NG) substitution reduces NOx emissions by almost 90%t relative to straight diesel operation; however, this is accompanied by 98% increase in HC emissions, 10 percentage points reduction in fuel conversion efficiency (FCE) and 12 percentage points increase in COVimep. Dual fuel LTC is achieved by injection of a small amount of diesel fuel (2–3 percent on an energy basis) to ignite a premixed natural gas–air mixture to attain very low NOx emissions (less than 0.2 g/kWh). Cyclic variations in both combustion modes were analyzed by observing the cyclic fluctuations in start of combustion (SOC), peak cylinder pressures (Pmax), combustion phasing (Ca50), and the separation between the diesel injection event and Ca50 (termed “relative combustion phasing”). For conventional dual fueling, as % NG increases, Pmax decreases, SOC and Ca50 are delayed, and cyclic variations increase. For dual fuel LTC, as diesel injection timing is advanced from 20° to 60°BTDC, the relative combustion phasing is identified as an important combustion parameter along with SoC, Pmax, and CaPmax. For both combustion modes, cyclic variations were characterized by alternating slow and fast burn cycles, especially at high %NG and advanced injection timings. Finally, heat release return maps were analyzed to demonstrate thermal management strategies as an effective tool to mitigate cyclic combustion variations, especially in dual fuel LTC.