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Controlled Auto-Ignition (CAI) combustion can effectively improve the thermal efficiency of conventional spark ignition (SI) gasoline engines, due to shortened combustion processes caused by multi-point auto-ignition. However, its commercial application is limited by the difficulties in controlling ignition timing and violent heat release process at high loads. Stratified flame ignited (SFI) hybrid combustion, a concept in which rich mixture around spark plug is consumed by flame propagation after spark ignition and the unburned lean mixture closing to cylinder wall auto-ignites in the increasing in-cylinder temperature during flame propagation, was proposed to overcome these challenges.

Lean-burn combustion is an effective method for increasing the thermal efficiency of gasoline engines fueled with stoichiometric fuel-air mixture, but leads to an unacceptable level of high cyclic variability before reaching ultra-low nitrogen oxide (NOx) emissions emitted from conventional gasoline engines. Multi-point micro-flame ignited (MFI) hybrid combustion was proposed to overcome this problem, and can be can be grouped into double-peak type, ramp type and trapezoid type with very low frequency of appearance. This research investigates the micro-flame ignition stages of double-peak type and ramp type MFI combustion captured by high speed photography. The results show that large flame is formed by the fast propagation of multi-point flame occurring in the central zone of the cylinder in the double-peak type. However, the multiple flame sites occur around the cylinder, and then gradually propagate and form a large flame accelerated by the independent small flame in the ramp type.

The dual-fuel Reactivity Controlled Compression Ignition (RCCI) combustion could achieve high efficiency and low emissions over a wide range of operating conditions. However, further high load extension is limited by the excessive pressure rise rate and soot emission. Polyoxymethylene dimethyl ethers (PODE), a novel diesel alternative fuel, has the capability to achieve stoichiometric smoke-free RCCI combustion due to its high oxygen content and unique molecule structure. In this study, experimental investigations on high load extension of gasoline/PODE RCCI operation were conducted using late intake valve closing (LIVC) strategy and intake boosting in a single-cylinder, heavy-duty diesel engine. The experimental results show that the upper load can be effectively extended through boosting and LIVC with gasoline/PODE stoichiometric operation.

Lean NOx trap (LNT) is a great potential NOx abatement method for lean-burn gasoline engines in consideration of exhaust aftertreatment cost and installation space. NOx firstly is adsorbed on storage sites during the lean-burn period, then reduced to N2 under catalysis of the catalyst sites in the rich-burn phase. There must be a spillover of NOx species between both types of sites. For a better understanding of this spillover process of NOx species between Pt (as the catalytic center) and BaO sites (as storage components in commercial catalyst), this work focused on the vital first step of spillover, the adsorption of NOx on clean substrate surface (γ-Al2O3 (110) surface) and Ba\Pt cluster supported by the surface. Based on first principles software VASP (Vienna Ab-initio Simulation Package), the most stable adsorption structures of NO with Pt3 clusters and (BaO)3 clusters on carrier γ- Al2O3 (110) surface were confirmed and the adsorption energy of these structures were compared.

Two-stroke engines have to face the problems of insufficient charge for short intake time and the loss of intake air caused by long valve overlap. In order to promote the power of a two-stroke poppet valve diesel engine, measures are taken to help optimize intake port structure. In this work, the scavenging and combustion processes of three common types of intake ports including horizontal intake port (HIP), combined swirl intake port (CSIP) and reversed tumble intake port (RTIP) were studied and their characteristics are summarized based on three-dimensional simulation. Results show that the RTIP has better performance in scavenging process for larger intake air trapped in the cylinder. Its scavenging efficiency reaches 84.7%, which is 1.7% higher than the HIP and the trapping ratio of the RTIP reaches 72.3% due to less short-circuiting loss, 11.2% higher than the HIP.

This work numerically investigates the detailed combustion kinetics of partially premixed combustion (PPC) in a diesel engine under three different premixed ratio fuel conditions. A reduced Primary Reference Fuel (PRF) chemical kinetics mechanism was coupled with CONVERGE-SAGE CFD model to predict PPC combustion under various operating conditions. The experimental results showed that the increase of premixed ratio (PR) fuel resulted in advanced combustion phasing. To provide insight into the effects of PR on ignition delay time and key reaction pathways, a post-process tool was used. The ignition delay time is related to the formation of hydroxyl (OH). Thus, the validated Converge CFD code with the PRF chemistry and the post-process tool was applied to investigate how PR change the formation of OH during the low-to high-temperature reaction transition. The reaction pathway analyses of the formations of OH before ignition time were investigated.

The objective of this study was to investigate combined effects of split injection strategies and intake air humidification on combustion and emissions of a partially premixed charge compression ignition (PCCI) marine diesel engine. In this research, a three-dimensional numerical model was established by a commercial code AVL-Fire to explore in-cylinder combustion process and pollutant formation factors in a four-stoke supercharged intercooled marine diesel engine under partial load at 1350 r/min. The novelty of this study is to combine different water-fuel ratios and fuel injection parameters (pilot injection timing and main injection timing) to find the optimized way to improve engine performance as well as NOx-soot emissions, thus meeting the increasingly stringent emissions restriction.

The combustion and emission characteristics of a diesel engine running on butanol-diesel blends were investigated in this study. The blending ratio of n-butanol to diesel was varied from 0 to 40 vol% using an increment of 10 vol%, and each blend was tested on a 2.7 L V6 common rail direction injection diesel engine equipped with an EGR system. The test was carried out under two engine loads at a constant engine speed, using various combinations of EGR ratios and injection timings. Test results indicate that n-butanol addition to engine fuel is able to substantially decrease soot emission from raw exhaust gas, while the change in NOx emissions varies depending on the n-butanol content and engine operating conditions. Increasing EGR ratio and retarding injection timing are effective approaches to reduce NOx emissions from combustion of n-butanol-diesel blends.

A novel combined power and cooling cycle based on the Organic Rankine Cycle (ORC) and the Compression Refrigeration Cycle (CRC) is proposed. The cycle can be driven by the exhaust heat from a diesel engine. In this combined cycle, ORC will translate the exhaust heat into power, and drive the compressor of CRC. The prime advantage of the combined cycle is that both the ORC and CRC are trans-critical cycles, and using CO₂ as working fluid. Natural, cheap, environmentally friendly, nontoxic and good heat transfer properties are some advantages of CO₂ as working fluid. In this paper, besides the basic combined cycle (ORC-CRC), another three novel cycles: ORC-CRC with an expander (ORC-CRCE), ORC with an internal heat exchanger as heat accumulator combined with CRC (ORCI-CRC), ORCI-CRCE, are analyzed and compared.

As a major power source, diesel engines are being widely used in a variety of fields. However, because of complex structure, some faults which cannot be detected by direct signals would occur on engines and even lead to accidents. Among all kinds of indirect signals, vibration signal is the most common choice for faults detection without disassemble because of its convenience and stability. This paper proposed a novel approach for detecting multiple engine faults based on block vibration signals using variational mode decomposition (VMD) and echo state network (ESN). Since the quadratic penalty has a great influence on adaptable VMD that may make expected component signals cannot be extracted exactly, this paper proposed a dynamic quadratic penalty value, which will change with decomposing level. This paper selected a best dynamic quadratic penalty value by analyzing a large amount of data and results showed that this approach can decompose signals more exactly.

A novel Fast Response Chemiluminescence Detector and a Fast Flame Ionization detector have been used to examine the instantaneous NO and unburnt hydrocarbon concentration in the cylinder and exhaust port of a DI Diesel engine. The in-cylinder results indicate very high levels of NO in the premixed phase of combustion, followed by generally lower levels during the diffusion burning phase. Hydrocarbon signals also indicate significant detail. The in-cylinder uHC signal is consistent with the probe location being between two of the fuel sprays. Both in-cylinder and exhaust results indicate rather high cyclic variability in the NO levels at steady conditions. Variations in the timing and structure of the exhaust uHC signal during the valve open period with load may give insight into the fuel spray/air motion.

The exhaust aftertreatment strategy is one of the most fundamental aspects of spark ignition engine technologies. For various types of engines (e.g., carburetor engine, PFI engine and GDI engine), measuring, purifying, modeling, and control strategies regarding the exhaust aftertreatment systems vary significantly. The primary goal of exhaust aftetreatment systems is to reduce the exhaust emission levels of NOx, HC and CO as well as to lower combustion soot. In general, there is a tradeoff among different engine performance aspects. The exhaust catalytic systems, such as the three way catalyst (TWC) and lean NOx trap (LNT) converters, can be applied together with the development of other engine technologies (e.g., variable valve timing, cold start). With respect to engine soot, some advanced diagnosing techniques are essential to obtain thorough investigation of exhaust emission mechanisms.

The inverse boundary element method (IBEM) is presented to accurately identify the noise sources of a diesel engine in this study. The sound pressures on four near-field planes were measured as inputs for the method. Then, the acoustic model of the full diesel engine was established using the boundary element method, and the acoustic transfer vectors (ATV) between the surface normal velocity and acoustic pressure at field points were calculated over the frequency range of interest. Based on the measured sound pressure and the ATVs, the surface normal velocity distribution of the diesel engine was reconstructed by the IBEM. The reconstructed pressures at two reference field points were compared with the measured ones. Furthermore, the panel contribution of each engine component was analyzed through the reconstructed surface velocity.

A new Diesel Particulate Generator (DPG) has been developed and commercialized for the automated testing of full-size, light duty Diesel Particulate Filters (DPFs). The system was optimized for filter development testing with a wide parameter range of relevant functional tests, and quality assurance testing where repeatability and rapid testing is important. A carefully designed Diesel-fuelled burner is combined with blowers to produce flows, temperatures and particulate matter (PM) that are representative of Diesel engines. The burner operates with continuous combustion of a Diesel fuel spray, with three-stage introduction of controlled airflows. Variation of these flows allows control of particulate generation independently of total gas flow and temperature (over a temperature and flow range). The system can generate stable PM at more than 20 g/h, or operate without PM formation so permitting preheating of a test filter.

Diesel engines have to reduce emissions to satisfy future emission legislations. The purpose of this paper is to investigate the effect of multiple injections and the combined effects of multi-injection and EGR on HD diesel engine emissions and performance. A common rail fuel injection system and high pressure EGR system based on variable geometry turbocharger (VGT) were used. Injection parameters (injection dwell and mass) were adjusted with different injection strategies (pilot-main, pilot-pilot-main, main-post and pilot-main-post) to find out the influence of these parameters on combustion and emissions. Secondly the coupling effects of multi-injection and EGR were evaluated at both high and low loads. Finally, while keeping NOx at 2.0 g/kW.h by adjusting EGR rate, the influence of injection parameters and EGR were tested to highlight their influence on smoke and BSFC.

The control of transient emissions from turbocharged diesel engines remains an important objective to manufacturers, since newly produced engines must meet the stringent criteria concerning exhaust emissions levels as dictated by the legislated Transient Cycles. In the present work, experimental tests are conducted on a medium-duty, turbocharged and after-cooled diesel engine in order to investigate the behavior and formation mechanism of nitric oxide (NO), smoke and combustion noise emissions under various transient operating schedules including acceleration, load change and starting. To this aim, a fully instrumented test bed was set up in order to record and research key engine and turbocharger variables during the transient events. The main parameters measured were nitric oxide concentration and smoke opacity (both using ultra-fast response analyzers) as well as combustion noise.

Particulate emissions from IC engines associated with transient engine conditions are very important (similar to the legislated gaseous emissions). This is true both during real-world and test cycle driving. This paper describes an instrument for measuring the number of particles, and their spectral weighting, in the 5nm to 1000nm size range, with a time response of 200ms. This is achieved via an electrostatic classification technique, consisting of a diffusion charger followed by a multi-element, constant voltage, classifier. Conversion of the data to other metrics, such as mass, is also described. Results are presented from artificial test aerosols and from light and heavy duty diesel engines on standard test cycles.

The emission capability of an exhaust system tuned for improved engine performance from an in-line four-cylinder engine has been investigated. The exhaust system comprises two close-coupled catalysts; each located in separate exhaust streams and has been termed the 4-2 close-coupled catalysts (CCC) -1 system. It has been shown that, given equivalent total catalyst volume, this system configuration results in compromised high exhaust flow rate emissions performance compared with a single catalyst (4-1semi-CCC) system. This emissions performance deficit has been attributed to the effect of engine frequency flow pulsations, which result in relatively high peak space velocities in the 4-2CCC-1 system despite the mean space velocity being consistent. Engine-based AFR Bias Sweep tests suggest that hydrocarbon emissions are most strongly affected by this phenomenon. At lower exhaust flow rates, the difference in performance between the two systems is negligible.

Wall temperature in GDI engine is influenced by both water jacket and gas heat source. In turn, wall temperature affects evaporation and mixing characteristics of impingement spray as well as combustion process and emissions. Therefore, in order to accurately simulate combustion process, accurate wall temperature is essential, which can be obtained by conjugate heat transfer (CHT) and piston heat transfer (PHT) models based on mapping combustion results. This CHT model considers temporal interaction between solid parts and cooling water. This paper presents an integrated methodology to reliably predict in-cylinder combustion process and temperature field of a 2.0L GDI engine which includes engine head/block/gasket and water jacket components. A two-way coupling numerical procedure on the basis of this integrated methodology is as follows.

The combustion in low-speed two-stroke marine diesel engines can be characterized as large spatial and temporal scales combustion. One of the most effective measures to reduce NOx emissions is to reduce the local maximum combustion temperature. In the current study, multi-dimensional numerical simulations have been conducted to explore the potential of Miller cycle, high compression ratio coupled with EGR (Exhaust Gas Recirculation) and WEF (water emulsified fuel) to improve the trade-off relationship of NOx-ISFC (indicated specific fuel consumption) in a low-speed two-stroke marine engine. The results show that the EGR ratio could be reduced combined with WEF to meet the Tier III emission regulation. The penalty on fuel consumption with EGR and WEF could be offset by Miller cycle and high geometric compression ratio.