Duty Compression Ignition Engine Research Articles

Impact of engine control variables on low load combustion efficiency and exhaust emissions of a methane-diesel dual fuel engine

A conventional diesel engine when operated in the reactivity-controlled compression ignition (RCCI) combustion strategy faces challenges of high total hydrocarbon (THC) and carbon monoxide (CO) emissions leading to poor combustion efficiency at low engine loads. The oxides of nitrogen (NOx) versus smoke trade-off, encountered in conventional diesel combustion, is replaced by the NOx-THC trade-off in the RCCI operation. This work focuses on addressing the NOx-THC trade-off issue by systematically investigating the effects of engine control variables, such as, fuel injection timing, exhaust gas recirculation (EGR) and intake throttling, on a light duty compression ignition engine running in a methane-diesel dual fuel mode. The engine is operated at a load of 3 bar gross indicated mean effective pressure and at a speed of 1500 rev/min. Based on relationships identified between engine control variables, combustion parameters, emissions and engine performance, a bottom-up approach is used to combine the control variables synergistically to improve the NOx-THC trade-off. A combination of advanced start of injection timing of diesel (−35 degree crank angle (°CA) after top dead centre), 50% premix ratio and 55% EGR levels along with the end of port fuel injection of methane in the middle of the intake stroke (−270°CA), has resulted in a ∼34 percentage points (from 56% to 90%) improvement in combustion efficiency and a ∼9.5 percentage points improvement in thermal efficiency compared to the baseline low load dual fuel operation while maintaining good combustion stability. THC emission is reduced from 105 to ∼25 g/kWh whilst maintaining low levels of NOx (<0.3 g/kWh).

Evaluation of the Effect of Low-Carbon Fuel Blends’ Properties in a Light-Duty CI Engine

<div class="section abstract"><div class="htmlview paragraph">De-fossilization is an increasingly important trend in the energy sector. In the transport sector the de-fossilization efforts have been centered in promoting the electrification of vehicles, nonetheless other pathways, like the use of carbon neutral or carbon-offsetting fuels under current vehicle fleets, are also worth considering. Low-carbon fuels (LCF) can be synthetized from sources that can take advantage of the carbon already present in the atmosphere (either by technologies like direct carbon capture or biological processes like photosynthesis in biofuels) and use energy from renewable sources for the necessary industrial processes. Although, LCFs can be compared to fossil fuels as energy sources for internal combustion engines, their composition is not the same and their properties can modify the engine combustion and emissions. This work evaluates the use of several diesel-like LCFs in a light duty compression ignition engine and correlates the fuel consumption, NOx, soot and CO<sub>2</sub> emissions to the fuel properties. Results indicate that the combined effect of a low density, low aromatic proportion, high energy density and high cetane number Fischer-Tropsch/FAME fuel blend can maintain the fuel consumption and soot emissions close to results with diesel at most engine conditions and reduce NOx emissions 0.5 - 2.5g/kWh. It was also observed that fuels with higher proportions of OMEx (with lower energy density and increased oxygen proportion) can reduce the soot emissions for the same level of NOx emissions with a fuel consumption penalty. Tank-to-wheel CO<sub>2</sub> emissions show little variation between fuels, while the well-to-wheel emissions are proportional to the renewable content.</div></div>

Development and experimental testing of an integrated prototype based on Stirling, ORC and a latent thermal energy storage system for waste heat recovery in naval application

This paper focuses on an advanced energy system, able to increase the overall efficiency of ships by recovering the heat wasted by the propulsion system. A small-scale prototype has been realized, developed, and tested under realistic operating conditions of boat during a winter and summer cruise. The main novelty of the research that has been presented in this paper lies in a significant contribution by developing an integrated dynamic device for electrical production and thermal energy storage. It is based on a 1000 cm3 light duty compression ignition engine coupled with a properly adapted Stirling Engine (SE), an Organic Rankine Cycle group (ORC) and a latent Thermal Energy Storage system (TES). All the components have been managed by means of a specifically developed electronic control, simulating two standard cruise profiles. Scaled engine power data have been imposed to simulate port, manoeuvring and open sea navigation phases. The consumption of hot water has been obtained by considering the typical hourly use profile of a cruise ship.It has been demonstrated that the proposed integrated system allows recovering all the thermal energy needed to satisfy the hot water request during the cruise, avoiding the use of auxiliary boilers. The results indicate a favourable effect because the recovered thermal energy represents the 7.7 % of the total energy consumed by fuel. The net electrical energy generated by ORC and Stirling engine resulted to be about 1 % of the total fuel energy consumption, respectively 0.8 % and 0.2 %. The developed prototype can be a useful tool in viability analysis and can easily be reproduced for several uses. In conclusion, the integration of different systems with an optimal integration and sizing of the thermal energy storage considerably improve the thermodynamic, economic and environmental results for future clean ships.

Performance and emissions of renewable blends with OME3-5 and HVO in heavy duty and light duty compression ignition engines

Interest in poly(oxymethylene)dimethyl ether (OME3-5) as an alternative to fossil fuels in compression ignition engines has increased owing to its potential for soot reduction. The high oxygen content of the polymer and lack of carbon–carbon bonds and aromatic structures can help to reduce engine out soot emissions. However, OME3-5 is potentially damaging to engine components, and thus engine modifications are required when using neat OME3-5.In the present study, OME3-5 was blended with hydrotreated vegetable oil (HVO), rapeseed methyl ester and the C8-alcohol 2-ethylhexanol (an isomer of n-octanol) to ensure miscibility. Three blends were designed with an oxygen content of 6.4, 12.8 and 17.8% by mass. Performance and emissions were compared to the reference fuels fossil diesel and HVO in a single cylinder light duty and heavy duty compression ignition engine at different loads.Evaluation of the combustion in both engines showed similar trends: The indicated thermal efficiency was slightly higher for the oxygenated fuel and the combustion duration shorter compared to diesel. Due to the lower heating value of the blends, the indicated specific fuel combustion increased with increasing share of OME3-5 in the blend.For both engines, engine out soot emissions were decreased strongly, whereas NOx emissions were slightly increased. Analysis of the particle size distribution showed a decrease in the particle number of agglomerated particles (>30 nm) for the blends. For the heavy duty engine, an increase in nucleation mode particles (<30 nm) was measured.

Development of a reduced four-component (toluene/n-heptane/iso-octane/ethanol) gasoline surrogate model

The prospect of blending gasoline fuel with ethanol is being investigated as a potential way to improve the knock residence of the base gasoline. However, one of the drawbacks is a lack of proper understanding of the reason for the non-linear response of blending ethanol and gasoline. This non-linearity could be better understood by an improved knowledge of the interactions of these fuel components at a molecular level. This study proposed a highly reduced four-component (toluene/n-heptane/iso-octane/ethanol) gasoline surrogate model containing 59 species and 270 reactions. The model was reduced using the direct relation graph with expert knowledge (DRG-X) (Lu and Law, 20015; Lu et al., 2011) and isomer lumping method. The computational singular perturbation (CSP) analysis were performed to reduce the potential stiffness issues by accordingly adjusting the Arrhenius coefficients of the proper reactions. The model has been comprehensively validated against wide range of ignition delay times (IDT) and flame speed (FS) measurement data as well as compared against two representative literature models from Liu et al. (2013) and Wang et al. (2015). Overall, good agreements were observed between model predictions and experimental data across the entire research octane number (RON), equivalence ratio, pressure and temperature range. In addition, the model has also been coupled with the computational fluid dynamic (CFD) models to simulate the experimental data of constant volume reacting spray of a low-octane gasoline (Haltermann straight-run naphtha), and in-cylinder pressures and temperatures of a high-octane gasoline (Haltermann Gasoline) combustion in a heavy duty compression ignition engine. The coupled model can qualitatively predict the experimentally obtained data with an improved performance for PRF, TPRF, and TPRF-ethanol surrogates.

Performance and emissions of diesel-biodiesel-ethanol blends in a light duty compression ignition engine

An approach to reduce CO2 emissions while simultaneously keeping the soot emissions down from compression ignition (CI) engines is to blend in short chained oxygenates into the fuel. In this work, two oxygenated fuel blends consisting of diesel, biodiesel and EtOH in the ratio of 68:17:15 and 58:14:30 has been utilized and studied in a single cylinder light duty (LD) CI engine in terms of efficiency and emissions. The reasons of utilizing biodiesel in the fuel blend is due to the emulsifying properties it has while the origin of the fuel is biomass. When performing the experiments, the control parameters were set as close as possible to the original equipment manufacturer (OEM) EU5 calibration of the multi-cylinder engine to study the possibility of using such blends in close to stock LD CI engines. The oxygenates, in particular the fuel with the higher concentration of EtOH, showed an net indicated efficiency of ∼52% at high load in comparison to diesel which never exceeded ∼48%. Regarding the emissions, several trends were observed; the soot-NOX trade-off diminished significantly when utilizing the fuel with the highest concentration of EtOH. The charge cooling effect reduces the NOX emissions while the exhaust particles are reduced both in terms of mean diameter and quantity. At lower loads, the THC and CO emissions were higher for the oxygenated blends than for the diesel due to the earlier mentioned charge cooling negatively affecting the combustion process. However, this trend seized at the higher loads when the in-cylinder temperature is higher and oxidation of the fuel is enhanced.

Development of valve stem seals for turbocharged heavy duty compression ignition engine of armoured fighting vehicles

Valve stem seals (VSS) restrict the amount of oil flowing from the area above the valve guide to the valve port area. Ideally a thin film of oil should exist between the valve guide and valve stem with no transfer of oil into the port area or combustion chamber. Too much oil flowing past the valve guide leads to excessive oil consumption. On other hand too little oil could cause excessive guide wear. In this paper the design of valve stem seals for heavy duty diesel engine working against harsh environment and severe duty cycle are discussed.

Performance and emissions of diesel-gasoline-ethanol blends in a light duty compression ignition engine

An approach to reduce CO2 emissions while simultaneously keeping the soot emissions down from compression ignition (CI) engines is to blend in short chained oxygenates into the fuel. In this work, two oxygenated fuel blends consisting of diesel, gasoline and ethanol (EtOH) in the ratio of 68:17:15 and 58:14:30 have been utilized and studied in a single cylinder light duty (LD) CI engine in terms of efficiency and emissions. The reasons of utilizing gasoline in the fuel blend is due to the emulsifying properties it has while increasing the total octane rating of the fuel to be able to run the engine with a higher fraction of premixed flame. When performing the experiments, the control parameters were set as close as possible to the original equipment manufacturer (OEM) EU5 calibration of the multi-cylinder engine to study the possibility of using such blends in close to stock LD CI engines. With the oxygenates, in particular the fuel with the higher concentration of EtOH achieved an indicated net efficiency of ∼51% inf comparison to ∼47% for diesel at 8 bar BMEP. The NOX emissions increased slightly for the double injection strategy at 13 bar BMEP from ∼13.5 g/kW h to ∼14.5 g/kW h when going from diesel fuel to the higher ethanol blend. However utilizing single injection strategy at lower loads reduces the NOX. Highest soot mass measured for diesel was ∼0.46 g/kW h in contrast to ∼0.1 g/kW h for the oxygenates. Also, soot production when running the engine on the ethanol containing fuels was not significantly affected by EGR utilization as in the case of diesel. Considering particle size distribution, the particles are reduced both in terms of mean diameter and quantity. At 1500 rpm and 2 bar BMEP an increase of over ∼300% in THC and CO was measured, however, increasing the speed and load to above 2000 rpm and 8 bar BMEP respectively, made the difference negligible due to high in-cylinder temperatures contributing to better fuel oxidation. Despite having lower cetane numbers, higher combustion stability was observed for the oxygenates fuels.

Influence of spatial and temporal distribution of Turbulent Kinetic Energy on heat transfer coefficient in a light duty CI engine operating with Partially Premixed Combustion

Emission regulations together with the need of more fuel-efficient engines have driven the development of promising combustion concepts in compression ignition (CI) engines. Most of these combustion concepts, lead towards a lean and low temperature combustion potentially suitable to achieve lower emission and fuel consumption levels compared to conventional diesel combustion. In this framework, Partially Premixed Combustion (PPC) using gasoline as fuel is one of the most accepted concepts. There are numerous studies focused on studying concepts such as PPC from the emissions point of view. Nonetheless, there is a lack of knowledge regarding changes in heat transfer introduced by the use of these combustion concepts. It is worth noting that heat transfer can be considered as a key aspect behind possible engine performance improvements. Thus, the reliable estimation of this parameter is of considerable importance. Additionally, a better understanding of how events such as injection and combustion might affect heat transfer is also relevant.To gain insight into gasoline PPC heat transfer coefficient, its evolution during late compression and early expansion were studied. In particular, this work aims to analyze Turbulent Kinetic Energy (TKE) spatial and temporal evolution influence on heat transfer coefficient. The analysis is based on experimental TKE maps derived from Particle Image Velocimetry (PIV) data. For the heat transfer coefficient estimation a modified Woschni correlation has been used. Results from several injection strategies and a reference motored case have been analyzed. It has been found that injection strategy has a considerable influence on the TKE field and hence on heat transfer coefficient evolution.

A RCCI operational limits assessment in a medium duty compression ignition engine using an adapted compression ratio

Reactivity Controlled Compression Ignition concept offers an ultra-low nitrogen oxide and soot emissions with a high thermal efficiency. This work investigates the capabilities of this low temperature combustion concept to work on the whole map of a medium duty engine proposing strategies to solve its main challenges. In this sense, an extension to high loads of the concept without exceeding mechanical stress as well as a mitigation of carbon oxide and unburned hydrocarbons emissions at low load together with a fuel consumption penalty have been identified as main Reactivity Controlled Compression Ignition drawbacks. For this purpose, a single cylinder engine derived from commercial four cylinders medium-duty engine with an adapted compression ratio of 12.75 is used. Commercial 95 octane gasoline was used as a low reactivity fuel and commercial diesel as a high reactivity fuel. Thus, the study consists of two different parts. Firstly, the work is focused on the development and evaluation of an engine map trying to achieve the maximum possible load without exceeding a pressure rise rate of 15bar/CAD. The second part holds on improving fuel consumption and carbon oxide and unburned hydrocarbons emissions at low load. Results suggest that it is possible to achieve up to 80% of nominal conventional diesel combustion engine load without overpassing the constraints of pressure rise rate (below 15bar/CAD) and maximum pressure peak (below 190bar) while obtaining ultra-low levels of nitrogen oxide and soot emissions. Regarding low load challenges, it has developed a particular methodology sweeping the gasoline-diesel blend together with intake temperature or exhaust gas recirculation maintaining constant the combustion phasing and ultra-low nitrogen oxide and soot emissions. As a result a drastic decrease carbon oxide and unburned hydrocarbons emissions is obtained with a slight fuel consumption improvement.

Numerical simulations of dual fuel combustion in a heavy duty compression ignition engine

In this study dual fuel direct injection was studied in terms of utilizing in compression ignition engines gaseous fuels with high octane number which are stored in liquid form, specifically liquid propane. Due to the fact that propane is not as much knock-resistant as natural gas, instead of conventional dual fuel system a system based on simultaneous direct injection of two fuel was selected as the most promissing one. Dual fuel operation was compared with pure diesel operation. The performed simulations showed huge potential of dual fuel system for burning light hydrocarbons in heavy duty compression ignition engines. However, further secondary fuel injection system optimization is required in order to improve atomization and lower the emissions.

Effects of Fuel Physical Properties on Auto-Ignition Characteristics in a Heavy Duty Compression Ignition Engine

Effects of Fuel Physical Properties on Auto-Ignition Characteristics in a Heavy Duty Compression Ignition Engine

Predicting the Performance and Emissions Characteristics of a Medium Duty Engine Retrofitted with Compressed Natural Gas System Using 1-Dimensional Software

The rise of crude oil price and the implications of exhaust emissions to the environment from combustion application call for a new reliable alternative fuel. A potential alternative fuel for compression ignition (C.I.) engine is the compressed natural gas (CNG). For C.I. engines to operate using CNG, or to be converted as a retrofitted CNG engine, further modifications are required. Previous works reported loss in brake power (BP) and increase in hydrocarbon (HC) emission for C.I. engine retrofitted with CNG fuelling. Verification of performance characteristics for CNG retrofitted engine through experimental analysis requires high cost and is very time consuming. Thus, a 1-Dimensional simulation software, GT-Power, was introduced in this study to reduce the experimental process and setup. A 4-cylinder medium duty C.I. engine (DE) and CNG retrofitted engine (RE) GT-Power models were used in this simulation work over various operational conditions: low, medium and high load conditions. As compared with DE model, results from RE model showed that RE model achieved an average 4.9% improvement for brake specific fuel consumption (BSFC) and loss in BP by 37.3%. For nitrogen oxides (NOX) and carbon dioxides (CO2) RE model predicted reduction of 48.1% (engine mode 1-9) and 33.4% (all engine modes), respectively. Moreover, RE produced 72.4% more carbon monoxide (CO) and 90.3% more HC emission.

Predicting the Performance and Emissions Characteristics of a Medium Duty Engine Retrofitted with Compressed Natural Gas System Using 1-Dimensional Software

The rise of crude oil price and the implications of exhaust emissions to the environment from combustion application call for a new reliable alternative fuel. A potential alternative fuel for compression ignition (C.I.) engine is the compressed natural gas (CNG). For C.I. engines to operate using CNG, or to be converted as a retrofitted CNG engine, further modifications are required. Previous works reported loss in brake power (BP) and increase in hydrocarbon (HC) emission for C.I. engine retrofitted with CNG fuelling. Verification of performance characteristics for CNG retrofitted engine through experimental analysis requires high cost and is very time consuming. Thus, a 1-Dimensional simulation software, GT-Power, was introduced in this study to reduce the experimental process and setup. A 4-cylinder medium duty C.I. engine (DE) and CNG retrofitted engine (RE) GT-Power models were used in this simulation work over various operational conditions: low, medium and high load conditions. As compared with DE model, results from RE model showed that RE model achieved an average 4.9% improvement for brake specific fuel consumption (BSFC) and loss in BP by 37.3%. For nitrogen oxides (NOX) and carbon dioxides (CO2) RE model predicted reduction of 48.1% (engine mode 1-9) and 33.4% (all engine modes), respectively. Moreover, RE produced 72.4% more carbon monoxide (CO) and 90.3% more HC emission.

Effect of Premixed Diesel Fuel on Partial HCCI Combustion Characteristics

This study investigated the effects of premixed diesel fuel on the auto-ignition characteristics in a light duty compression ignition engine. A partial homogeneous chargecompression ignition (HCCI) engine was modified from a single cylinder, four-stroke, direct injection compression ignition engine. The partial HCCI is achieved by injecting diesel fuel into the intake port of the engine, while maintaining diesel fuel injected in cylinder for combustion triggering. The auto-ignition of diesel fuel has been studied at various premixed ratios from 0 to 0.60, under engine speed of 1600 rpm and 20Nm load. The results for performance, emissions and combustion were compared with those achieved without premixed fuel. From the heat release rate (HRR) profile which was calculated from in-cylinder pressure, it is clearly observed that two-stage and three-stage ignition were occurred in some of the cases. Besides, the increases of premixed ratio to some extent have significantly reduced in NO emission.

Mono-Gas Fuelled Engine Performance and Emissions Simulation Using GT-Power

The scarcity of oil resources and the rise of crude oil price had driven the whole world to seek for an alternative fuel for automotive industry. One of the prospective alternative fuels for compression ignition (C.I.) engine is compressed natural gas (CNG). In order to operate CNG in a C.I. engine as mono-gas engine (RE), several modifications are required. The modifications that involves are compression ratio, fuel injection type, addition of spark plug and fuel itself. So as to reduce the time in preparing the experimental test bed and high cost analytical study a 1-dimensional simulation software GT-Power was introduce. The GT-Power simulation model for a 4 cylinder medium duty C.I. engine (DE) and RE has been built to study the effects of conversion process to the performance and emissions of the engine at various operational conditions: low, medium and high load conditions. As compared with DE model, results from RE model showed loss in brake power (BP) and brake thermal efficiency (BTE) by 37.3% and 19% respectively. Meanwhile, for brake specific air consumption (BSAC) RE predicted to undergo an average of 19412.6 g/kW-h and increment in volumetric efficiency by percentage of difference 22%. In other side, oxides of nitrogen (NOx) RE engine model predicted reduction of 48.1% (engine mode 1-9) and increased in hydrocarbons (HC) by 90.3.

An investigation on RCCI combustion in a heavy duty diesel engine using in-cylinder blending of diesel and gasoline fuels

An experimental and numerical study has been carried out to understand mixing and auto-ignition processes in RCCI combustion conditions, using gasoline and diesel as low and high reactivity fuels, respectively.Three parametrical studies have been developed using a heavy duty compression ignition engine equipped with a direct injector and a port fuel injector, to be able to vary the in-cylinder fuel blending ratio. Besides, a detailed analysis in terms of air/fuel mixing process has also been performed by means of a 1-D spray model.It is found that combustion starts with the auto-ignition of the diesel injection and the air and gasoline entrained. Then, the temperature and pressure raise starts the flame propagation across the lean diesel and gasoline zones of the combustion chamber. As the Diesel/Gasoline fuel ratio is reduced, the ignition delay increases extending the mixing time and the first combustion stage gets lowered while the second one is enhanced. The advance of the diesel injection timing enlarges the mentioned effects over the combustion process. With respect to conventional neat diesel combustion, a slight reduction in terms of NOx and a very important reduction in terms of soot were achieved with the RCCI combustion.

The influence of fatty acid methyl ester profiles on inter-cycle variability in a heavy duty compression ignition engine

With the advent of alternative fuels, such as biodiesels and related blends, it is important to develop an understanding of their effects on inter-cycle variability which, in turn, influences engine performance as well as its emission. Using four methanol trans-esterified biomass fuels of differing carbon chain length and degree of unsaturation, this paper provides insight into the effect that alternative fuels have on inter-cycle variability. The experiments were conducted with a heavy-duty Cummins, turbo-charged, common-rail compression ignition engine. Combustion performance is reported in terms of the following key in-cylinder parameters: indicated mean effective pressure (IMEP), net heat release rate (NHRR), standard deviation of variability (StDev), coefficient of variation (CoV), peak pressure, peak pressure timing and maximum rate of pressure rise. A link is also established between the cyclic variability and oxygen ratio, which is a good indicator of stoichiometry.The results show that the fatty acid structures did not have a significant effect on injection timing, injection duration, injection pressure, StDev of IMEP, or the timing of peak motoring and combustion pressures. However, a significant effect was noted on the premixed and diffusion combustion proportions, combustion peak pressure and maximum rate of pressure rise. Additionally, the boost pressure, IMEP and combustion peak pressure were found to be directly correlated to the oxygen ratio. The emission of particles positively correlates with oxygen content in the fuel as well as in the air–fuel mixture resulting in a higher total number of particles per unit of mass.

Effect of biodiesel on particulate numbers and composition emitted from turbocharged diesel engine

In present study a turbocharged, medium duty compression ignition engine was alternatively fuelled with biodiesel to investigate the changes in particulate matter composition, relative to that taken with diesel fuel. The engine was operated on an AC electrical dynamometer in accordance with an 8-mode, steady-state cycle. The numbers of particles were estimated through electrical low pressure impactor, while sulfates and trace metals were analyzed by ion chromatography and inductively coupled plasma-atomic emission spectroscopy, respectively. Nitric oxides and nitrogen dioxides were measured separately using SEMTECH-DS. Experimental results revealed that, on account of elevated ratios of nitrogen dioxide to nitrogen oxides, mean accumulation mode particles were 42 % lower with biodiesel. On the other hand, nuclei mode particles were higher with biodiesel, owing to heterogeneous nucleation and accounting for an increase in sulfate emissions up to 8 % with biodiesel as compared to diesel. On the average, trace metal emissions were significantly reduced showing 65–85.4 % reduction rates with biodiesel, relative to its counterpart. Further to this, individual congeners such as iron, calcium, and sodium were the predominant elements of the trace metals emitted from engine. The mean relative decrease in iron and calcium was 89–97.8 and 77.6–87 %, respectively, while the relative rise in sodium was in the range of 29–46 % with biodiesel. Further, elements such as zinc, chromium, and aluminum showed substantial abatement, whereas potassium, magnesium, and manganese exhibited irregular trends on account of variable engine loads and speeds during the various modes of cycle.