For decades, alternative fuels have been studied to further engine efficiency and lower combustion emissions. Of these fuels, biodiesel, alcohols, and ethers have shown advantageous benefits of improved mixing capability or reduced combustion emissions. Ether fuels consist of a range of C-O-C chain lengths that offer various noteworthy fuel properties such as fuel oxygen content and cetane number. In this work, oxymethylene dimethyl ether (OME 3 ) and diesel are used as neat and blended fuels on a single-cylinder high compression ratio engine. Four test fuels are investigated in this work; baseline diesel, two diesel/OME 3 blends, and neat OME 3 fuel. Engine tests are conducted at an engine load of 6 bar and the intake oxygen concentration is modulated via EGR to realize the resulting engine performance, stability, and exhaust emissions among the test fuels. The results show that blending OME 3 fuels with diesel is an effective technique to reduce soot emissions with minimal effect on NOx emissions. Moreover, neat OME 3 was capable of emitting low NOx and soot emissions with a lower EGR amount than that of diesel-blends, mitigating negative combustion implication of EGR at high levels.

This work investigates the effects of low reactivity fuel (LRF) on reactivity controlled compression ignition (RCCI) engine with fossil diesel. RCCI mode of combustion is a low temperature combustion (LTC) strategy which reduces both oxides of nitrogen (NOx) and soot emissions simultaneously. Syngas and methanol can be obtained from renewable biological resources and conventional coal. LRF (methanol, syngas and gasoline) has been supplied to the engine along with intake air and diesel is injected to initiate the combustion process. Test engine has been operated for different dual fuel modes at constant engine speed (1500 rpm) and load (80%). Closed cycle combustion simulations have been performed to complement the experimental results and in-cylinder dynamics. Particle size mimic (PSM) model has been used to investigate the soot particle number and mass-size distributions and mean particle size. Results confirmed that maximum gross indicated thermal efficiency (38%) has been observed in gasoline/diesel dual fuel mode. Compared to gasoline/diesel dual fuel mode, about 74% and 86%, lower soot and NOx emissions have been observed for methanol/diesel dual fuel mode, while about 46% and 52% lower soot and NOx emissions have been found in syngas/diesel mode. About 53% higher carbon monoxide emission has been observed for syngas/diesel case as compared to gasoline/diesel case. Predictions from soot modelling reveal that condensation mode, surface growth mode and nucleation mode particles are dominant in methanol, syngas and gasoline/diesel dual fuel modes respectively. Bigger primary soot particles (diameter > 35 nm, nanometre) have been observed for methanol/diesel mode and the gasoline/diesel mode shows a smaller size of primary particles.

The natural gas industry has seen a considerable increase in production recently as the world seeks out new sources of economical, reliable, and more environmentally friendly energy. Moving this natural gas requires a complex network of pipelines and compressors, including reciprocating engines, to keep the gas moving. Many of these engines were designed more than 40 years ago and must be retrofit with modern technologies to improve their performance while simultaneously reducing the harmful emissions that they produce. In this study a directed energy ignition system is tested on a two-stroke, single cylinder, natural gas-fired engine. Stability and emissions will be observed throughout a range of spark waveforms for a single speed and load that enables the most fuel-lean operation of the engine. Improving the combustion process of the legacy pipeline engines is a substantial area of opportunity for reducing emissions output. One means of doing so is by improving an engines ability to operate at leaner conditions. To accomplish this, an ignition system needs to be able to send more energy to the spark plug in a controlled manner than a tradition capacitive-discharge ignition system. Controlling the energy is accomplished by optimizing the structure of the waveform or “profile” for each engine design. With this particular directed energy ignition system, spark profiles are able to be configured by changing the duration and amount of current sent to the spark plug. This study investigates a single operating speed and load for 9 different spark energy configurations. Engine operation at these test conditions will allow for emissions and engine performance data, using directed energy, to be analyzed in contrast to capacitive-discharge ignition.

Many research studies have focused on utilizing gasoline in modern compression ignition engines to reduce emissions and improve efficiency. Collectively, this combustion mode has become known as gasoline compression ignition (GCI). One of the biggest challenges with GCI operation is maintaining control over the combustion process through the fuel injection strategy, such that the engine can be controlled on a cycle-by-cycle basis. Research studies have investigated a wide variety of GCI injection strategies (i.e., fuel stratification levels) to maintain control over the heat release rate while achieving low temperature combustion (LTC). This work shows that at loads relevant to light-duty engines, partial fuel stratification (PFS) with gasoline provides very little controllability over the timing of combustion. On the contrary, heavy fuel stratification (HFS) provides very linear and pronounced control over the timing of combustion. However, the HFS strategy has challenges achieving LTC operation due to the air handling burdens associated with the high EGR rates that are required to reduce NOx emissions to near zero levels. In this work, a wide variety of gasoline fuel reactivities (octane numbers ranging from < 40 to 87) were investigated to understand the engine performance and emissions of HFS-GCI operation on a multi-cylinder light-duty engine. The results indicate that over an EGR sweep at 4 bar BMEP, the gasoline fuels can achieve LTC operation with ultra-low NOx and soot emissions, while conventional diesel combustion (CDC) is unable to simultaneously achieve low NOx and soot. At 10 bar BMEP, all the gasoline fuels were compared to diesel, but using mixing controlled combustion and not LTC.

A fuel blend consisting of 10% S8 by mass (a Fischer-Tropsch synthetic kerosene), and 90% ULSD (Ultra Low Sulfur Diesel) was investigated for their combustion characteristics and impact on emissions during RCCI (Reactivity Controlled Compression Ignition) combustion in a single cylinder experimental engine utilizing a 65% by mass n-butanol port fuel injection (PFI). RCCI is a dual fuel combustion strategy achieved with the introduction of a PFI fuel of the low-reactive n-butanol, and a direct injection (DI) of a high-reactivity blend (FT-BLEND) into an experimental diesel engine. The combustion analysis and emissions testing were conducted at 1500 RPM at an engine load of 5 bar IMEP (Indicated Mean Effective Pressure), and CA50 of 9° ATDC (After Top Dead Center); CDC (Conventional Diesel Combustion) and RCCI with 65Bu-35ULSD were utilized as the baseline for AHRR (Apparent Heat Release Rate), ringing and emissions comparisons. It was found during a preliminary investigation with a Constant Volume Combustion Chamber (CVCC) that the introduction of 10% by mass S8 into a mixture with 90% ULSD by mass only increased Derived Cetane Number (DCN) by 0.8, yet it was found to have a significant effect on the combustion characteristics of the fuel blend. This led to the change in injection timing necessary for maintaining 65Bu-35F-T BLEND RCCI at a CA50 of 5° ATDC (After Top Dead Center) to be shifted 3° closer to TDC, thus affecting the Ringing Intensity (RI), Pressure Rise Rate, and heat release of the blend all to decrease. CDC was conducted with a primary injection of 14° BTDC at a rail pressure of 800 bar, all RCCI testing was conducted with 65% PFI of n-butanol by mass and 35% DI, to prevent knock, with a rail pressure of 600 bar and a pilot injection of 60° BTDC for 0.35 ms. 65Bu-35ULSD RCCI was conducted with a primary injection at 6° BTDC with neat ULSD#2, the fuel 65Bu-35F-T BLEND in RCCI had a primary injection at 3° BTDC to maintain CA50 at 9° ATDC. 65Bu-35ULSD RCCI experienced a NO x and soot emissions decrease of 40.8% and 91.44% respectively in comparison to CDC. The fuel 65Bu-35F-T BLEND in RCCI exhibited an additional decrease of NO x and soot of 32.9 and 5.3%, in comparison to 65Bu-35ULSD RCCI for an overall decrease in emissions of 73.7% and 96.71% respectively. Ringing Intensity followed a similar trend with reductions in RI for 65Bu-35ULSD RCCI decreasing only by 6.2% whereas 65Bu-35F-T BLEND had a decrease in RI of 76.6%. Although emissions for both RCCI fuels experienced a decrease in NO x and soot in comparison to CDC, UHC and CO did increase as a result of RCCI. CO emissions for 65Bu-35ULSD RCCI and 65Bu-35F-T BLEND where increased from CDC by a factor of 5 and 4 respectively with UHC emissions rising from CDC by a factor of 3.4. The fuel 65Bu-35F-T BLEND had a higher combustion efficiency than 65Bu-35ULSD in RCCI at 91.2% due to lower CO emissions of the blend.

Natural gas pipelines form a vital part of the energy infrastructure of the United States. In order to overcome head losses in moving the natural gas from one area of the country to another, large compressors are needed to pressurize the gas. For decades, the most efficient and cost-effective method of compressing the gas has been through the use of integral compressor engines. Pipeline companies have great financial incentive to continue using these engines, but increasingly stringent emissions regulations threaten their continued operation. In this study, the above problem was addressed by developing a zero-dimensional thermodynamic cycle simulation to predict NO x emissions for a large bore, single cylinder, naturally aspirated, 2-stroke, natural gas engine. Excellent agreement was obtained between experimental measurements and simulated predictions of the average exhaust NO x concentration. Once the simulation was validated by experimental data, a sensitivity analysis was conducted to determine the response of NO x emissions to changes in three factors: trapped equivalence ratio (TER), burned gas fraction (x b ), and stuffing box temperature (SBT). This study sought to identify the fundamental thermodynamic reasons that NO x varied with each factor, and to quantify their respective effects. It was found that changes in each factor effected linear changes in the combustion temperatures, which effected linear changes in the rate constant of the first reaction in the extended Zeldovich mechanism, which effected exponential changes in the NO x emissions. TER and SBT were shown to be directly related to NO x , while x b was shown to be inversely related to NO x .

For modern Diesel aftertreatment systems the ratio of nitrogen dioxide (NO 2 ) to nitrogen oxides emissions (NO x ) is of great importance for the conversion of total NO x especially at low loads and low engine out exhaust temperatures. As known from previous studies the relative air-fuel ratio and so the increase of oxygen has a major impact on the in-cylinder formation of NO 2 . As the focus lies mainly on increasing the relative air-fuel ratio by increasing the boost pressure the influence of bounded oxygen in oxygenated fuels is not yet fully understood and is therefore in the focus of this papers. Bounded oxygen offers the potential to release oxygen radicals, which can increase NO 2 formation from nitrogen monoxide (NO) at higher pressures according to the principle of Le Chatelier. At low pressures, however, released oxygen radicals can also lead to a reduction of NO 2 . Additionally, concerning the in-cylinder formation of NO 2 , the formation of formaldehyde (HCHO) is focused in this investigation, too. Especially for the oxygenated fuel like OME 3–5 which can be interpreted as a compound of formaldehyde molecules the HCHO emission might increase. Although HCHO has not yet been regulated for vehicles, its carcinogenic properties require its reduction as far as possible. In this paper, investigations are presented which were carried out on a single-cylinder Diesel engine with different oxygenated fuels such as oxymethylene ether compounds (OME 3–5 ) and 2-ethoxyethyl ether (2-EEE) and blends of these components with conventional Diesel fuel. The relevant exhaust gas components were measured using different analysis method for high accuracy and mutual validation. To analyze the effects of the fuel composition on nitrogen dioxide and formaldehyde formation the fuels are compared with pure Diesel fuel operation. Several operating points were investigated together while varying engine parameters such as relative air-fuel ratio, EGR rate, injection timing and injection pressure in a one-factor-time parameter study. Additionally, at a low load operating point a Design of Experiments (DoE) study was done to see the statistical impact and the main influencing parameters of the formation of NO 2 and HCHO. Furthermore, other typical Diesel emissions like particulates, carbon monoxide and the total nitrogen oxides are investigated and compared. The investigations show an inconsistent behavior at different operating points for NO 2 . In most operating points a decrease of NO 2 is visible, which was attributed to a decrease of the total NO x emission. Especially at higher relative air-fuel ratios and so high charge pressures the potential of oxygenated fuels to increase the NO 2 to NO x ratio becomes apparent. Due to the very low particulates emissions which can be achieved with OME 3–5 fuel, no restriction on low relative air/fuel ratios and higher EGR rates regarding the particulate emissions (smoke limit) exists. The HCHO emissions show different behavior in these restriction zones. At partial load, high EGR rates and low relative air-fuel ratios, HCHO emissions increase. In contrast, when the load is increased and the stoichiometric conditions are reached, the HCHO emissions decrease.

Lean combustion has proven to be an effective way to improve the efficiency and emissions of the direct injection spark ignition (DISI) engine. However, one of the main problems at the lean stability limit is the major decrease in flame temperature due to dilution, resulting in a low laminar flame speed, especially under low-speed engine operating conditions. The split injection is a potential technology to realize proper air-fuel mixing and achieve different spray distribution that can help in solving such problems. In this study, split injections with different secondary injection timings were tested to achieve homogeneous and homogeneous-stratified modes in a DISI optical engine under lean-burn mode. The split ratio of each strategy was 1:1. The engine was operated at 800 rpm, and a high-energy ignition system was utilized to realize lean combustion at a lambda of 1.55. Engine combustion performance and emissions were tested while performing high-speed color recording to study the characteristics of flame chemiluminescence through a quartz piston combined with a 45-degree mirror installed below. Flame structure during various combustion phases was compared under different selected conditions based on a digital image processing technique. The results show that the pressure and emissions vary with the second injection timing. Proper control of the split injection timing can improve lean combustion performance, including faster flame speed, increased indicated mean effective pressure (IMEP), and lower harmful emissions. Poor fuel evaporation and soot generation from spatial hot spots in the combustion process of split injection are the major challenges for further improvement.

In the medium and long term, cogeneration plants in Germany will play an important role in the transition towards a cleaner and more efficient electricity and heat generation, compared to the conventional uncoupled power plants. For most of the currently used CHP (Combined Heat and Power) units, which operate with a lean-burn process, the NO x emissions limit represents an obstacle to increasing the electrical efficiency. Therefore, the lean burn process has become less attractive because of stricter future NO x emissions limit. In this context, the stoichiometric combustion process with a three-way catalytic converter provides a solution. However, the present study shows that lean burn operation still has potential due to direct water injection into the combustion chamber. This work includes an experimental investigation of the impact of different injection parameters (beginning of injection timing, injection pressure difference and water-to-fuel ratio) on the effectiveness of direct water injection regarding the improvement of the trade-off between engine efficiency and NO x emissions. For the execution of the experimental investigations, a series-production CHP-engine was equipped with a direct injection system consisting of a high-pressure unit, a high-pressure pipe and a GDI-injector. For the injector integration, the cylinder head was machined sidewise (close to the exhaust gas valve). Furthermore, 3D CFD simulations of the injection process allowed gaining a deeper insight into the complex spray-flow interaction, wall film formation and evaporation at different injection timings. For the 3D CFD simulations, the spray model used was tuned with help of spray pictures, taken on the spray test bed. Water injection at the beginning of the intake stroke (330 °CA BFTDC) reduces NO x emissions most effectively. Moreover, it causes the least engine efficiency loss. The increase of the injection pressure difference (between 20 and 80 bar) leads to a significant increase of the engine efficiency. However, it has a secondary effect on the NO x emissions reduction. The lowest NO x emissions are reached with an injection pressure difference of 60 bar. The combination of direct water injection (at the beginning of the intake stroke, injection pressure difference of 60 bar) with earlier combustion phasings enables an increase in the engine efficiency and a simultaneous decrease in NO x emissions without loss in engine performance. Main drawbacks of water injection are longer combustion duration and higher CO and HC emissions. In addition, the lower exhaust gas temperature causes a deterioration of the conversion of the HC molecules in the oxidation catalyst and reduces the heat recovery efficiency of the CHP-system.

The main concerns of utilizing jojoba biodiesel in CI engines is that it has a high viscosity and high NO x formation. Therefore, this article purposes in endeavoring to improve the combustion and emission parameters of a CI engine working with diesel/jojoba biodiesel blend and higher alcohols under various engine loads. The higher alcohols typically are n-butanol, n-heptanol, and n-octanol, which are combined with 50% diesel, 40% of jojoba biodiesel at a volume portion of 10%, and they are designated as DJB, DJH, and DJO respectively. The jojoba biodiesel is manufactured via a transesterification process with facilitating mechanical dispersion. The findings display that there is a drop in p max and HRR for DJB, DJH, and DJO blends compared to pure diesel fuel, whereas the combustion duration and ignition delay are extended. The brake specific fuel consumption is enlarged. Concerning engine emissions, the NO x formation is reduced while the CO, UHC, and soot emissions are increased for DJB, DJH, and DJO mixtures. It can be deduced that combining high fractions of jojoba biodiesel with C 4 , C 7 , and C 8 alcohols have the feasible to accomplish low NO x formation in the interim having high thermal efficiency level.

Growing environmental concerns and demand for better fuel economy are driving forces that motivate the research for more advanced engines. Multi-mode combustion strategies have gained attention for their potential to provide high thermal efficiency and low emissions for light-duty applications. These strategies target optimizing the engine performance by correlating different combustion modes to load operating conditions. The extension from boosted SI mode at high loads to advanced compression ignition (ACI) mode at low loads can be achieved by increasing compression ratio and utilizing intake air heating. Further, in order to enable an accurate control of intake charge condition for ACI mode and rapid mode-switches, it is essential to gain fundamental insights into the autoignition process. Within the scope of ACI, homogeneous charge compression ignition (HCCI) mode is of significant interest. It is known for its potential benefits, operation at low fuel consumption, low NO x and PM emissions. In the present work, a virtual Cooperative Fuel Research (CFR) engine model is used to analyze fuel effects on ACI combustion. In particular, the effect of fuel Octane Sensitivity (S) (at constant RON) on autoignition propensity is assessed under beyond-RON (BRON) and beyond-MON (BMON) ACI conditions. The 3D CFR engine computational fluid dynamics (CFD) model employs finite-rate chemistry approach with multi-zone binning strategy to capture autoignition. Two binary blends with Research Octane Number (RON) of 90 are chosen for this study: Primary reference fuel (PRF) with S = 0, and toluene-heptane (TH) blend with S = 10.8, representing paraffinic and aromatic gasoline surrogates. Reduced mechanisms for these blends are generated from a detailed gasoline surrogate kinetic mechanism. Simulation results with the reduced mechanisms are validated against experimental data from an in-house CFR engine, with respect to in-cylinder pressure, heat release rate and combustion phasing. Thereafter, the sensitivity of combustion behavior to ACI operating condition (BRON vs BMON), air-fuel ratio (λ = 2 and 3), and engine speed (600 and 900rpm) is analyzed for both fuels. It is shown that the sensitivity of a fuel’s autoignition characteristics to λ and engine speed significantly differs at BRON and BMON conditions. Moreover, this sensitivity is found to vary among fuels, despite the same RON. This study also indicates that the octane index (OI) fails to capture the trend in the variation of autoignition propensity with S under BMON conditions.

Canada’s remote communities experience harsh weather much of the year and run diesel generators 24 hours a day to provide heat and power. These generators utilize diesel fuel that is transported at great expense and generate greenhouse gas (GHG) and pollutant emissions. Meanwhile, remote communities produce organic wastes, such as wastewater and food wastes. Appropriate treatment of these wastes not only improves the community health and environment, but also generates certain amount of renewable fuels, such as biogas and/or syngas. Replacing diesel fuel by the renewable fuels generated from the waste treatment in the diesel generators can offset the use of diesel and also reduce GHG and pollutant emissions in remote communities. This paper reports an application of biogas generated from wastewater treatment to replace diesel in a small diesel generator by dual fuel engine technology. With simple modification, the biogas containing 50–95% of methane was introduced into the engine intake manifold. Tests were conducted to evaluate the effects of biogas flow rate and composition on average diesel fuel consumption and emissions of carbon dioxide (CO 2 ), carbon monoxide (CO), nitrogen oxides (NOx) and unburned hydrocarbons (HC). The results reveal that the introduction of biogas into the engine reduced the average diesel consumption. However, the reduction of average diesel consumption with increasing biogas flow rate was not linear, possibly due to the increase in HC emissions. The introduction of biogas reduced NOx emissions but increased CO emissions. A change in the composition of biogas (methane to CO 2 ratio) did not significantly affect the average diesel consumption and emissions.

Converting existing compression ignition (CI) engines to spark ignition (SI) operation can increase the use of natural gas (NG) in heavy-duty engine applications and reduce the reliance on petroleum fuels. Gas fumigation upstream of the intake manifold and the addition of a spark plug in place of the diesel injector to initiate and control the combustion process is a convenient approach for converting existing diesel engines to dedicated NG operation. Stoichiometric operation and a three-way catalytic converter can help the engine to comply with increasingly strict emission regulations. However, as the CI-to-SI conversion usually maintains the conventional geometry of a CI engine (i.e., maintains the flat cylinder head and the bowl-in piston), the goal of this study was to observe some of the effects that the diesel conversion to stoichiometric NG SI operation will have on the engine’s performance and emissions. Dynamometer tests were performed at a constant engine speed at 1300 rpm but various spark timings. The experimental results for a net indicated mean effective pressure ∼ 6.7 bar showed that ignition timing did not affect the end of combustion due to the slow-burn inside the squish. Moreover, the less-optimal conditions inside the squish led to increased carbon monoxide (CO) and unburned hydrocarbon (UHC) emissions. While the combustion event was stable with no signs of knocking at the medium load conditions investigated here, the results suggest that the engine control needs to optimize the mass fraction trapped inside the squish region for a higher efficiency and lower emissions.

Converting existing compression ignition engines to spark ignition approach is a promising approach to increase the application of natural gas in the heavy-duty transportation sector. However, the diesel-like environment dramatically affects the engine performance and emissions. As a result, experimental tests are needed to investigate the characteristics of such converted engines. A machine learning model based on bagged decision trees algorithm was established in this study to reduce the experimental cost and identify the operating conditions of special interest for analysis. Preliminary engine tests that changed spark timing, mixture equivalence ratio, and engine speed (three key engine operation variables) but maintained intake and boundary conditions were applied as model input to train such a correlative model. The model output was the indicated mean effective pressure, which is an engine parameter generally used to assist in locating high engine efficiency regions at constant engine speed and fuel/air ratio. After training, the correlative model can provide acceptable prediction performance except few outliers. Subsequently, boosting ensemble learning approach was applied in this study to help improve the model performance. Furthermore, the results showed that the boosted decision trees algorithm better described the combustion process inside the cylinder, as least for the operating conditions investigated in this study.

Knowledge of the NO:NO 2 ratio emitted from a diesel engine is particularly important for ensuring the highest performance of SCR NO x aftertreatment systems. As real driving emissions from vehicles increase in importance, the need to understand the NO:NO 2 ratio emitted from a diesel engine during transient operation similarly increases. Previous work by the authors identified significant differences in NO:NO 2 ratio throughout the exhaust period of a single engine cycle, with proportionally more NO 2 being emitted during the blowdown period compared to the rest of the exhaust stroke. At the time it was not known what caused this effect. In this study, crank-angle resolved NO and NO 2 measurements using fast response CLD (for NO) and a new fast LIF instrument (for NO 2 ) have been taken from a single cylinder high-speed light duty diesel engine at three different speed and load points including a point with and without EGR. In addition, crank-angle resolved unburned hydrocarbon (UHC) measurements have been taken simultaneously using a fast FID. The NO x emitted per cycle and the peak cylinder pressure of that cycle have showed high correlation coefficients (R 2 < 0.97 at all test points) in this work. In addition, a variation of the NO:NO 2 ratio through the engine’s exhaust stroke is also observed indicative of in-cylinder stratification of NO and NO 2 . A new link between the NO:NO 2 ratio and the UHC emissions from an individual engine cycle is observed — the results show that where there are higher levels of UHC emissions in the first part of the exhaust stroke (blowdown), perhaps caused by injector dribble or release from crevices, the proportion of NO 2 emitted from that cycle is increased. This effect is observed and analysed across all test points and with and without EGR. The performance of the new fast LIF analyser has also been evaluated, in comparison with the previous state-of-the-art and standard “slow” emissions measurement apparatus showing a reduction in the noise of the measurement by an order of magnitude.

The mixing of fuel and air in the combustion chamber of an IC engine is crucial to emissions formation. Therefore, developing effective diagnostic techniques for measuring mixing is critical for progressing IC engines. Existing methodologies for the optical measurement of air-fuel mixing, including Rayleigh scattering and Laser Induced Fluorescence (LIF), have demonstrated various diagnostic-implementation challenges, high uncertainties under engine-relevant environments, and strong interferences from the liquid spray which prevents their use in near-spray measurements. This work presents the use of an alternative approach based on a laser-absorption/scattering technique called Ultraviolet-Visible Diffuse Back-Illumination (UV-Vis DBI) to quantify local equivalence ratio in a vaporizing diesel spray. Ultraviolet and visible light are generated using a ND:YAG pumped frequency-doubled tunable dye laser operating at 9.9 kHz. The simultaneous UV-Visible illumination is used to back-illuminate a vaporizing diesel spray, and the resulting extinction of each signal is recorded by a pair of high-speed cameras. Using an aromatic tracer (naphthalene, BP = 218 °C) in a base fuel of dodecane (BP = 215–217 °C), the UV illumination (280 nm) is absorbed along the illumination path through the spray, yielding a projected image of line-of-sight optical depth that is proportional to the path-average fuel vapor concentration in the vapor region of the spray. The visible illumination is chosen at a non-absorbing wavelength (560 nm), such that the light extinction is only due to liquid scattering, yielding a projected image of the liquid spray. A key advantage of the method is that the absorption coefficient of the selected tracer is relatively independent of temperature and pressure for 280-nm illumination, reducing measurement uncertainties at engine-relevant conditions. Measurements are also achievable in near-spray vapor regions since there is no mie-scattering interference from the liquid spray. The diagnostic is applied to measure the fuel-air mixing field of a diesel spray produced by a Bosch CRI3-20 ks1.5 single-orifice injector (90 μm diameter) similar to ECN Spray A. Measurements are conducted in a non-reacting high-pressure and temperature nitrogen environment using a constant-flow, optically-accessible spray chamber operating at 60 bar and 900 K. The results are evaluated against existing ECN mixing measurements based on Rayleigh scattering. The diagnostic yields centerline and radial mixture fraction measurements that match the ECN Rayleigh measurements within uncertainty bounds.

To comply with future emission regulations for internal combustion engines, system-related cold-start conditions in short-distance traffic constitute a particular challenge. Under these conditions, pollutant emissions are seriously increased due to internal engine effects and unfavorable operating conditions of the exhaust aftertreatment systems. As a secondary effect, the composition of the exhaust gases has a considerable influence on the deposition of aerosols via different deposition mechanisms and on fouling processes of exhaust gas-carrying components. Also, the performance of exhaust gas aftertreatment systems may be affected disadvantageously. In this study, the exhaust gas and deposit composition of a turbocharged three-cylinder gasoline engine is examined in-situ upstream of the catalytic converter at ambient and engine starting temperatures of −22 °C to 23 °C using a Fourier-transform infrared spectrometer and a particle spectrometer. For the cold start investigation, a modern gasoline engine with series engine periphery is used. In particular, the investigation of the behavior of deposits in the exhaust system of gasoline engines during cold start under dynamic driving conditions represents an extraordinary challenge due to an average lower soot concentration in the exhaust gas compared to diesel engines and so far, has not been examined in this form. A novel sampling method allows ex-situ analysis of formed deposits during a single driving cycle. Both, particle number concentration and the deposition rate are higher in the testing procedure of Real Driving Emissions (RDE) than in the inner-city part of the Worldwide harmonized Light vehicles Test Cycle (WLTC). In addition, reduced ambient temperatures increase the amount of deposits, which consist predominantly of soot and to a minor fraction of volatile compounds. Although the primary particle size distributions of the deposited soot particles do not change when boundary conditions change, the degree of graphitization within the particles increases with increasing exhaust gas temperature.

The influence of fuel properties on particulate matter (PM) emissions from a catalytic gasoline particulate filter (GPF) equipped gasoline direct injection (GDI) engine were investigated using novel “virtual drivetrain” software and an engine mated to an engine dynamometer. The virtual drivetrain software was developed in LabVIEW to operate the engine on an engine dynamometer as if it were in a vehicle undergoing a driving cycle. The software uses a physics-based approach to determine vehicle acceleration and speed based on engine load and a programed “shift” schedule to control engine speed. The software uses a control algorithm to modulate engine load and braking to match a calculated vehicle speed with the prescribed speed trace of the driving cycle of choice. The first 200 seconds of the WLTP driving cycle was tested using 6 different fuel formulations of varying volatility, aromaticity, and ethanol concentration. The first 200 seconds of the WLTP was chosen as the test condition because it is the most problematic section of the driving cycle for controlling PM emissions due to the cold start and cold drive-off. It was found that there was a strong correlation between aromaticity of the fuel and the engine-out PM emissions, with the highest emitting fuel producing more than double the mass emissions of the low PM production fuel. However, the post-GPF PM emissions depended greatly on the soot loading state of the GPF. The fuel with the highest engine-out PM emissions produced comparable post-GPF emissions to the lowest PM producing fuel over the driving cycle when the GPF was loaded over three cycles with the respective fuels. These results demonstrate the importance of GPF loading state when aftertreatment systems are used for PM reduction. It also shows that GPF control may be more important than fuel properties, and that regulatory compliance for PM can be achieved with proper GPF control calibration irrespective of fuel type.

For turbocharged diesel engine systems, emission reduction is the most significant challenge that manufacturers should overcome. In response to the emission reduction challenge most turbocharged diesel engine systems have adopted complex exhaust aftertreatment systems. Due to the current stringent emission regulation, exhaust aftertreatment system nowadays needs to discover new methods to increase its efficiency of pollution conversion. Increasing the inlet temperature of aftertreatment systems can help reduce the light-off time. Whilst most methods to do this involve increases in fuel consumption (retarded injection, engine throttling), insulating the turbocharger turbine to reduce heat loss does not have this drawback. This paper presents a simulation and experimental study the performance of a turbocharger with inner insulated turbine housing, compared with the standard turbocharger (same turbine wheel without inner insulation). Both turbochargers were tested on an engine gas stand test rig with a 2.2L prototype engine acting as an exhaust gas generator. In a steady state condition, the insulated turbocharger can achieve 5 to 14K higher turbine outlet temperature depending on the engine speed and load conditions. Three types of transient tests were implemented to investigate turbocharger turbine heat transfer performance. The test plan was designed to the engine warm up, step load transient, WLTC cycle and simplified RDE cycle. In the engine warm up test result, the temperature drops between the turbine inlet and outlet was reduced by 4K with the insulated turbine housing. In the results of step load transient test, the turbine with insulated turbine housing was observed to get only 4K temperature benefit but with 2kRPM higher turbocharger speed under the same turbocharger inlet and outlet boundary conditions. In the WLTC cycle test result, turbocharger average speed was increased by 0.8kRPM due to the increased enthalpy of the turbine with insulation, the turbine outlet temperature has an average 1.7K improvement. The experimental results were used to parameterise a simple, 1D, lumped capacitance model which could predict similar aerodynamic behaviour of the two turbines (turbine housing insulated and non-insulated). However, current model has less accuracy in highly transient process as the heat transfer coefficients are unchangeable in each process. The turbine outlet temperature got at most 10K error for the turbine with non-insulated housing and 13K error for the insulated one. The model was shown to over-estimate the benefits of the inner insulation for 1K in turbine outlet temperature.

Vehicle type approval drive cycles have become a mainstay for benchmarking performance of engines in the development cycle. However, they are typically long and costly to test, with questions of repeatability and real-world relevance. With the move to Real Driving Emission (RDE) style testing, complete foreknowledge of the cycle is no longer guaranteed. This paper presents a methodology for identifying key behaviours (or information rich regions) from the current worldwide harmonised light-duty test cycle (WLTC) type approval test using a moving 2-minute window approach. Three techniques for pattern recognition are presented and applied to data collected from a modern Gasoline Turbocharged Direct Injection (GTDI) engine, run through the WLTC. The techniques examine different points in the process, with the first examining response data, and working backwards to the original vehicle speed cycle specification. The first two techniques, Intensity Ratio (IR) for cumulative responses and Energy Residency (ER) for engine inputs, are newly developed in this paper. The final technique, Dynamic Time Warping (DTW) is a new application of an existing tool to the subject of vehicle drive cycles. The techniques are examined in isolation and discussed, before being brought together to identify commonly agreed information rich sub-cycle candidates that best represent the parent cycle. The techniques make use of a combination of time windowing, signal derivative and peak analysis methods. The two-minute window is chosen based on the length of an existing sub-cycle that was identified as part of earlier work, and this method is also described and validated in this paper. One sub-cycle identified by the approach represents a duration reduction of 93% to a containable 2-minute transient. This segment accounts for 15% of the overall WLTC fuel used. A discussion of the techniques and their applications is presented to motivate future work in this area.