Diesel Pilot Ignition Research Articles

Ammonia fueled engine with diesel pilot ignition: Approach to achieve ultra-high ammonia substitution

Ammonia is a hydrogen-rich zero-carbon fuel, and is one of the most promising approaches to realize energy decarbonization in the fields of industry and transportation. Efficient operation and emissions control have been the primary obstacle to develop engines with high ammonia energy share. In this study, the combustion and emissions of an ammonia-fueled engine with diesel pilot ignition are investigated, and the target is to achieve ultra-high ammonia substitution with acceptable thermal efficiency. The ammonia energy share is first increased from 30% to 90% at an intermediate load, with a split diesel injection triggering ammonia combustion. It found that the increased ammonia energy share reduces the indicated thermal efficiency from 48.3% to 38.9% with high unburned ammonia emissions. The NOx emissions exhibit a turning point with increased ammonia substitution, which indicates that the NOx emissions transition from the thermal-dominated to the fuel-dominated regime. The diesel pilot injection strategy is then optimized, by advancing the main injection timing and changing the pre-injection amount and the interval between two injection events. Optimized diesel injection controls the ignition timing and combustion process, thereby improving thermal efficiency and emissions at high ammonia energy shares. An ultra-high ammonia energy share of 95% could be finally achieved, and the thermal efficiency is 40.2%. It is also noted that as engine load increases, engine thermal efficiency at an ammonia energy share of 80% could be elevated to 44.2%.

Experimental and computational study on the effects of exhaust gas recirculation on thermodynamics, combustion and emission characteristics of a diesel pilot ignition natural gas engine

This study investigates the impact of diesel pilot ignition (DPI) natural gas (NG) engines on combustion and emission characteristics across various exhaust gas recirculation (EGR) volumes.

Optical Study on the Effects of Methane Equivalence Ratio and Diesel Injection Mass on Diesel-Ignited Methane Combustion Process

Pilot diesel ignition is an effective approach for achieving efficient and clean combustion of natural gas. In this study, a rapid compression and expansion machine (RCEM) was constructed for examining diesel-ignited premixed methane combustion. The effects of the methane equivalence ratio and pilot diesel mass on the combustion process of diesel-ignited premixed methane gas were investigated. The results show that the combustion process can be divided into two stages: diesel dominance and premixed methane combustion. An increase in the methane equivalence ratio inhibits diesel combustion, leading to delayed CA10 and OH radical generation. However, it enhances premixed methane flame propagation and improves the heat release rate, resulting in a shorter combustion duration. An increase in the pilot diesel mass contributes to a larger flame area and higher OH generation intensity in the ignition region; however, too large a diesel mass inhibits methane flame propagation towards the diesel nozzle due to an extended injection duration. In conclusion, a larger pilot diesel mass can achieve better overall combustion performance, but excessive amounts may be counterproductive.

Effects of Wobbe Index on the Combustion and Emission Characteristics of a Natural Gas/Diesel RCCI Engine

Abstract Due to energy shortage and environmental problems, the application of natural gas in internal combustion engine has attracted extensive attention. Therefore, diesel pilot ignition natural gas engine is a promising technology. However, the different sources of natural gas lead to the change in composition, which has a great impact on engine combustion and emission. In this study, the relationship between Wobbe index (WI) and swirl ratio (SR) of six different natural gas mixtures was studied by numerical simulation method. Besides, reactivity controlled compression ignition (RCCI) combustion strategy was evaluated. The results showed that increasing the WI increased the in-cylinder pressure and temperature, increased the ignition delay, and shortened the combustion duration, the gross indicated efficiency (GIE) of the six gases exceeded 50%. In addition, the increase of WI increased the nitrogen oxide (NOx) emissions and reduced the hydrocarbon (HC) and carbon monoxide (CO) emissions. Moreover, the peak pressure rise rate (PPRR) increased with the rise of WI, which may lead to engine knock. The results also showed that the increase of SR increased the in-cylinder pressure and temperature and improved the PPRR. When the SR was 0.7 and the WI was 51.7, the combustion and emission performance of the RCCI engine was relatively better.

Coupling combustion simulation and primary evaluation of an asymmetric motion diesel pilot hydrogen engine

The thermal efficiency and combustion of conventional hydrogen engines cannot be optimized and improved by its symmetric reciprocating. This article introduces an asymmetric motion hydrogen engine (AHE) and investigates its combustion characteristics using diesel pilot ignition. A dynamic model is firstly proposed to describe the asymmetric motion of the AHE, and then it is coupled into a multidimensional model for combustion simulation. The effect of asymmetric motion on the AHE combustion is also analyzed by comparing with a corresponding conventional symmetric hydrogen engine (SHE). The results show that the AHE moves slower in compression and faster in expansion than the SHE, which brings about higher hydrogen-air mixing level for combustion. The asymmetric motion delays diesel injection to ignite the AHE and its combustion appears later than the SHE, which leads to lower pressure and temperature for reducing NO formation. However, the AHE faster expansion has a more severe post-combustion effect to reduce isovolumetric heat release level and decrease the energy efficiency.

A coupling dynamics and thermodynamics study of diesel pilot-ignition injection effect on hydrogen combustion of a linear engine

Linear hydrogen engine is a new type of energy conversion device to supports variable compression ratio operation for clean emission. However, the new hydrogen engine using conventional spark ignition shows slow combustion speed and low thermal efficiency. This study makes a preliminary assessment to discuss the application of diesel pilot-ignition technology in linear hydrogen engine aiming to accelerate combustion and improve efficiency. A new coupling model between dynamics and thermodynamics is proposed and then iteratively calculated to give insight the interrelationship of combustion and motion in a diesel pilot-ignited linear hydrogen engine, while the effect of injection position on the hydrogen engine combustion is also investigated to make clear the feasibility of combustion optimization. The results indicate that the linear hydrogen engine is speeded by properly advancing the injection to promote combustion, and it has a positive effect on in-cylinder gas temperature, pressure and pressure rise rate, unless the injection is too early which results in higher NO emissions and aggravate the working intensity of the engine. In addition, the closer the fuel injection is to the top dead center, the incomplete combustion of hydrogen and diesel in the cylinder, the decrease of engine fuel economy and the increase of soot emissions. There is an optimal thermal efficiency of 40.7% for the LHE when it operates in the 0.8 mm injection position condition.

A comparison between low- and high-pressure injection dual-fuel modes of diesel-pilot-ignition ammonia combustion engines

Ammonia, as a carbon-free fuel, is drawing more and more attention due to its potential of decarbonization for marine engines. The dual-fuel mode that can compensate for the poor combustion properties of ammonia has exhibited some prospects for practical application, but more relevant researches are urgent to promote the carbon-free fuel, especially for the high-pressure injection dual-fuel (HPDF) mode. In this paper, the ammonia spray experiments under the diesel-like conditions are conducted using the high-speed photography to calibrate the spray sub-models. Then, the combustion and emission characteristics of the low- and high-pressure injection dual-fuel modes of diesel pilot-ignition ammonia combustion engines are numerically studied and compared. Particularly, the equivalent CO2 considering the global warming potential of CO2 and N2O are evaluated (i.e. CO2 + 300 × N2O). The results show that the maximum ammonia ratio about 80% by energy is recommended for the low-pressure injection dual-fuel (LPDF) mode and further increase the diesel replacement ratio will increase the probability of misfire, while the HPDF mode has the potential to achieve a 97% diesel replacement ratio. Compared with the pure diesel mode, the HPDF mode has similar indicated thermal efficiency, cooling and exhaust loss, while it can significantly reduce the equivalent CO2 with little increase in the NH3 emissions. Owing to the reduced heat transfer loss, the LPDF mode has the potential to achieve a higher indicated thermal efficiency than the pure-diesel mode, but its ability to reduce the equivalent CO2 would be relatively limited because the significant increase of N2O emissions if exhaust after treatments were not employed. The comparison between the LPDF mode and HPDF mode shows that the former case has the potential to achieve a higher indicated thermal efficiency, while the latter case can significantly reduce the engine-out NH3, NOx and greenhouse gas emissions.

Parametric study on dual-fuel ignition characteristics under marine engine-relevant conditions

Dual-fuel (DF) combustion strategies with low-carbon fuels are attractive for the shipping industry because of their better economy and lesser emissions. However, DF ignition process is highly complex and difficult to control due to its strong sensitivities to mixture-states. As such, a comprehensive numerical study was conducted to investigate the influence of thermodynamic states, ambient-fuel reactivity and micro-mixing process on the autoignition characteristics of DF mixtures (methane/n-heptane and methanol/n-heptane) under marine engine-relevant conditions. A novel parameter-sensitivity evaluation method by log–log definition was firstly proposed to quantify the ignition-delay-time (IDT) dependence on thermodynamic trajectory and charge reactivity, based on a newly detailed kinetic model (NUIGMech1.1). It was found that the methanol-addition has a larger impact on IDTs than methane, and also exhibits ignition-promoting behaviors at high temperatures. Besides, the IDT displays a higher sensitivity to temperature under methanol/air atmosphere but a higher sensitivity to pressure under methane/air atmosphere, suggesting that methane/diesel DF engines are prone to occur cycle-to-cycle variations under diesel pilot-ignition (DPI) mode while methanol/diesel DF engines exist the larger cycle variations under reactivity-controlled compression-ignition (RCCI) mode. There are small IDT-changes for methane/n-heptane mixtures with varying ϕCH4 while large variations for methanol/n-heptane as varying ϕCH3OH. Moreover, methanol shows the more significant chemical-effect on ignition. The mixture fraction of methanol-based blends with the shortest IDT, defined as the most-reactive mixture fraction (ZMR), is larger than that of methane at a given temperature. This demonstrates that the mixing degree (the high-reactivity fuel to low-reactivity fuel ratio) plays an important role in controlling the ignition. The mixing-time is also critical for ignition behavior of fuels, and autoignition of methanol/n-heptane blends exhibits higher sensitivity to mixing rates than methane/n-heptane. Therefore, adjusting injection parameters could tailor mixing-trajectories to offset changes in fuel autoignition chemistry. Additional reaction sensitivity analyses demonstrate that the OH radicals play a key role in the whole system reactivity at low temperatures, while HO2 becomes more important at intermediate-temperatures and CH3OH + OH <=> CH2OH + H2O displays the highest ignition-inhibition. Significantly, CH3OH + HO2 <=> CH2OH + H2O2 shows a high promoting effect on IDTs at high temperatures, resulting in the IDT-reduction.

Exploring the potential benefits of high-efficiency dual-fuel combustion on a heavy-duty multi-cylinder engine for SuperTruck I

In support of the Daimler SuperTruck I team’s 55% brake thermal efficiency (BTE) pathway goal, researchers at Oak Ridge National Laboratory performed an experimental investigation of the potential efficiency and emissions benefits of dual-fuel advanced combustion approaches on a modified heavy-duty 15-L Detroit™ DD15 engine. For this work, a natural gas port fuel injection system with an independent injection control for each cylinder was added to the DD15 engine. For the dual-fuel strategies investigated, 65%–90% of the total fuel energy was supplied through the added port fuel injection natural gas (NG) fueling system. The remaining fuel energy was supplied by one or more direct injections of diesel fuel using the production high pressure diesel fueling system. The production DD15 air handling system and combustion geometry were unmodified for this study. Efficiency and emissions with dual-fuel strategies including both low temperature combustion (LTC) and non-LTC approaches such as dual fuel direct-injection were investigated along with control authority over combustion phasing. Parametric studies of dual-fuel NG/diesel advanced combustion were conducted in order to experimentally investigate the potential of high-efficiency, dual-fuel combustion strategies to improve BTE in a multi-cylinder engine, understand the potential reductions in engine-out emissions, and characterize the range of combustion phasing controllability. Characterization of mode transitions from mixing-controlled diesel pilot ignition to kinetically controlled ignition is presented. Key findings from this study included a reproducible demonstration of BTE approaching 48% at up to a 13-bar brake mean effective pressure with significant reductions in engine-out NOx and soot emissions. Additional results from investigating load transients in dual-fuel mode and initial characterization of particle size distribution during dual-fuel operation are presented.

Effects of ethane addition on diesel-methane dual-fuel combustion in a heavy-duty engine

The present study is a continuation of the previous work by Ahmad et al. (2020), in which ethane (C2H6) enriched diesel-methane (CH4) dual-fuel (DF) combustion was experimentally investigated in a single-cylinder heavy-duty engine. Here, the experiments of ethane enriched DF combustion are carried out with new details together with supporting zero-dimensional (0D) and one-dimensional (1D) chemical kinetics simulations. Three port-fuel injected (PFI) gaseous blends of pure methane with varying ethane concentrations of 0%, 10%, and 20% are used as the main fuels. The PFI gaseous blend provides 97% of the total-fuel energy (TFE), which is ignited by a small 3% (TFE based) pilot diesel. Experiments are performed under lean condition (∅gas = 0.52) for two engine speeds while keeping the TFE and other operating conditions constant. Calculated results from 0D and 1D simulations under engine relevant conditions including theoretical combustion mode analysis (β-curve) are used to deepen the phenomenological understanding of the experimental results. The results reveal that adding ethane into pure methane has minor effects on the pilot-diesel ignition timing. However, ethane addition greatly enhances the ignitability of methane after the start of combustion. Ethane enriched gaseous blends yield higher thermal efficiency and reduce combustion duration compared to pure methane. According to combustion mode analysis, ethane tendency to promote spontaneous autoignition may be one of the reasons for improving overall combustion performance. It is observed that ethane enriched gaseous blends produce lower unburned methane (UB-CH4) and unburned hydrocarbons (THC) accompanied with higher nitrogen oxides (NOx) because of the higher combustion efficiency. Furthermore, ethane addition considerably helps to reduce cycle-to-cycle variations under lean conditions compared to pure methane.

Soot Emission Reduction in a Biogas-DME Hybrid Dual-Fuel Engine

Combustion characteristics and harmful emissions with emphasized soot emission in the new concept of a biogas-dimethyl ether (DME) hybrid dual-fuel engine were analyzed. The effects of DME content, biogas compositions and diesel injection were examined. At any biogas composition, a rise in DME content in the fuel mixture leads to an increase in indicative engine cycle work (Wi) and NOx but a decrease in CO and soot volume fraction (fv). The effects of DME on Wi and soot volume fraction are more significant for poor biogas than for rich biogas, contrary to its effect tendency on CO and NOx concentrations. With a given operating condition and DME content, the biogas compositions slightly affect the performance and emission of a biogas-DME hybrid dual-fuel engine. At a fixed global equivalence ratio, the reduction of diesel injection leads to an increase in Wi and NOx concentration but a decrease in CO and soot volume fraction. The lower the diesel injection is, the more significant the effects of DME content on the combustion properties and pollutant emissions are. At a given operating condition and the same global equivalence ratio, the biogas-DME PCCI combustion mode is more advantageous than biogas-DME dual-fuel combustion mode. The substitution of diesel pilot ignition by DME pilot ignition in a biogas-DME hybrid dual engine is the optimal solution for both performance improvement and pollution emissions reduction.

Optical Characterization of the Combustion Process inside a Large-Bore Dual-Fuel Two-Stroke Marine Engine by Using Multiple High-Speed Cameras

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;Dual-fuel engines for marine propulsion are gaining in importance due to operational and environmental benefits. Here the combustion in a dual-fuel marine engine operating on diesel and natural gas, is studied using a multiple high-speed camera arrangement. By recording the natural flame emission from three different directions the flame position inside the engine cylinder can be spatially mapped and tracked in time. Through space carving a rough estimate of the three-dimensional (3D) flame contour can be obtained. From this contour, properties like flame length and height, as well as ignition locations can be extracted. The multi-camera imaging is applied to a dual-fuel marine two-stroke engine, with a bore diameter of 0.5 m and a stroke of 2.2 m. Both liquid and gaseous fuels are directly injected at high pressure, using separate injection systems. Optical access is obtained using borescope inserts, resulting in a minimum disturbance to the cylinder geometry. In this type of engine, with fuel injection from positions at the rim of the cylinder, the flame morphology becomes asymmetric. The optical spatial mapping and tracking method is demonstrated to be well suited for the study of such an asymmetric combustion system. Spatial mapping and tracking of flame position is applied to both engine operating modes; normal diesel operation and dual-fuel operation with diesel pilot ignition of the gas. Similarities and differences between diesel and gas flame shape and development can thus be visualised directly. The effects of changing charge density, gas injection pressure and injection nozzle geometry on the flame geometry and development are also studied.&lt;/div&gt;&lt;/div&gt;

Influences of natural gas energy fraction on combustion and emission characteristics of a diesel pilot ignition natural gas engine based on a reduced chemical kinetic model

In this research, a reduced chemical kinetic mechanism was coupled in computational fluid dynamics (CFD) model to study the detailed influence mechanism of natural gas (NG) energy fraction on the diesel pilot ignition (DPI) NG engines. Based on the CFD model calibrated by experimental data, the impacts of NG energy fraction on the combustion and emission generation processes in DPI NG engine were investigated. The results show that, the start of combustion (SOC) in DPI NG engine is advanced as the NG energy fraction declines and the maximum advance comes up to 4.1°CA at 1000 rpm and 100% load. The deep analysis reveals that the positive influence of R342 on the temperature is the main reason for the shorter ignition delay. The 10–90% combustion duration increases first as the NG energy fraction changes from 50% to 60%, and then decreases if the NG energy fraction further increases. Furthermore, the combustion mode is changed from premixed combustion to non-premixed combustion with the NG energy fraction decreasing. For the emissions, the NOx emission drops with the decline of NG energy fraction, and the maximum decrease of NOx emission comes up to 0.96 mg/kJ at 1000 rpm and 100% load. The CO emission increases first and then decreases as the NG energy fraction rises from 50% to 90%.

Effects of reformed fuel on dual-fuel combustion particulate morphology

Advancements in catalytic reforming have demonstrated the ability to generate syngas (a mixture of CO and hydrogen) from a single hydrocarbon stream. This syngas mixture can then be used to replace diesel fuel and enable dual-fuel combustion strategies. The role of port-fuel injected syngas, composed of equal parts hydrogen and carbon monoxide by volume, was investigated experimentally for soot reduction benefits under diesel pilot ignition and reactivity controlled compression ignition strategies. Particle size distribution measurements were made with a scanning mobility particle sizer and condensation particle counter for different levels of syngas substitution. To explain the experimental results, computational fluid dynamics simulations utilizing a detailed stochastic soot model were used to validate and initialize additional simulations that isolate mixing and chemistry effects. Based on these simulations, the influence of adding syngas on soot particle size and quantity is discussed.

Influences of excess air coefficient on combustion and emission performance of diesel pilot ignition natural gas engine by coupling computational fluid dynamics with reduced chemical kinetic model

In the presented study, the influence of lean-burn on combustion and emission performance of diesel pilot ignition natural gas engine was investigated by using the method of computational fluid dynamics coupling with the reduced chemical kinetic model. Based on bench tested results, the computational fluid dynamics model was validated in four typical conditions, and then it was used for the simulation at different excess air coefficient. Due to the visibility of computational fluid dynamics results, the combustion medium process and emissions medium products were obtained, which then were used to explain the influence mechanism of excess air coefficient. The simulated results show that, under 50% load, the maximum cylinder pressure becomes larger and the start of combustion is advanced when the excess air coefficient increases from 1.0 to 1.5, and the maximum advance of the start of combustion reaches 9.5 °CA. Nevertheless, under 100% load, the start of combustion is advanced first and then retarded. Meanwhile, the higher the excess air coefficient is, the earlier the heat release rate shoots up. When the excess air coefficient increases from 1.2, the 10–50%, 50–90% and 10–90% combustion duration become longer. The nitrogen oxide emission increases as the excess air coefficient rises from 1.0 to 1.1 but decreases if it continues to increase. The unburned methane emission decreases first and then increases with the increase of the excess air coefficient. Nevertheless, at 1500 rpm and full load, the unburned methane emission shoots up as the excess air coefficient changes from 1.3 to 1.5 and the maximum difference of unburned methane emission reaches 3233 ppm.

Influence of Injection Parameters and Operating Conditions on Ignition and Combustion in Dual-Fuel Engines

Dual-fuel (DF) engines offer great fuel flexibility since they can either run on gaseous or liquid fuels. In the case of diesel pilot-ignited DF engines, the main source of energy is provided by gaseous fuel, whereas the diesel fuel acts only as an ignition source. Therefore, a proper auto-ignition of the pilot fuel is of utmost importance for combustion in DF engines. However, auto-ignition of the pilot fuel suffers from lower compression temperatures of Miller or Atkinson valve timings. These valve timings are applied to increase efficiency and lower nitrogen oxide (NOx) engine emissions. In order to improve the ignition, it is necessary to understand which parameters influence the ignition in DF engines. For this purpose, experiments were conducted and the influence of parameters, such as injection pressure, pilot fuel quantity, compression temperature, and air–fuel (A/F) equivalence ratio of the homogenous natural gas–air mixture were investigated. The experiments were performed on a periodically chargeable combustion cell using optical high-speed recordings and thermodynamic measurement techniques for pressure and temperature. The study reveals that the quality of the diesel pilot ignition in terms of short ignition delay and a high number of ignited sprays significantly depends on the injection parameters and operating conditions. In most cases, the pilot fuel suffers from too high dilution due to its small quantity and long ignition delays. This results in a small number of ignited sprays and consequently leads to longer combustion durations. Furthermore, the experiments confirm that the natural gas of the background mixture influences the auto-ignition of the diesel pilot oil.

A kinetic study on the effects of methane substitution on the ignition of n-heptane/air mixture

In the operation of natural gas engines using diesel pilot ignition (DPI), the ignition delay is longer than that in the operation of a comparable diesel engine. The cause of such effect is more complicated than reducing the concentration of oxidizer. In this research, the chemical kinetics of the ignition process is studied using a homogeneous model containing n-heptane, methane and air. The base fluid is the mixture of methane and air. The equivalence ratio of methane is varied to study the sensitivity of the ratio on the concentration of methane. The dependency on temperature is studied by varying the base fluid temperature. The base fluid is then mixed with the diesel surrogate fuel, n-heptane. The mole fraction of n-heptane, ZC7, covers a wide range to represent the local mixture in different locations of engine combustion chamber. To obtain a complete understanding of the ignition process, different ignition delay times are defined based on temperature increment, n-heptane conversion, and methane conversion. The effects of methane on the ignition reaction paths are analyzed for selected cases. The fundamental causes of the methane's effects are explained based on the reaction path analysis and sensitivity analysis.

Numerical evaluation of the effect of methane number on natural gas and diesel dual-fuel combustion

Natural gas and diesel dual-fuel combustion is a promising technology for efficiently utilizing natural gas in a compression ignition engine. Natural gas composition varies depending on the geographical source, which affects engine performance. The methane number is an indicator of natural gas fuel quality to assess the variation in composition. In this study, the influences of methane number on natural gas/diesel dual-fuel combustion were numerically examined using computational fluid dynamic simulations. The differences between natural gases with the same methane number but different components were also compared. Two dual-fuel combustion strategies, diesel pilot ignition, and reactivity controlled compression ignition were evaluated. The results show that for both diesel pilot ignition and reactivity controlled compression ignition, the ignition delay increases and the combustion duration decreases as the methane number is increased. The retarded trend of ignition of reactivity controlled compression ignition is more significant than that of diesel pilot ignition, while the decreased trend in combustion duration is less significant. To understand this trend, a chemical kinetics study of ignition delay characteristic of natural gas and n-heptane mixture was conducted. The result reveals that introducing ethane, propane, or an ethane–propane mixture into pure methane shortens the ignition delay in the entire temperature range. However, for the methane and n-heptane mixture, adding ethane, or propane, or an ethane–propane mixture shortens the ignition delay in the high temperature range, while increases the ignition delay in the low temperature range. These observations in combination with the analysis of air–fuel mixture formation and combustion provide the evidence to interpret the different ignition and combustion behaviors between diesel pilot ignition and reactivity controlled compression ignition combustion. In addition, a temperature A-factor sensitivity study was carried out to explain the result of the chemical kinetics study. Furthermore, the responses of emissions to methane number were also investigated. The results show that for diesel pilot ignition, the hydrocarbon and carbon monoxide emissions decrease with the decreased methane number. However, for reactivity controlled compression ignition, the variations of hydrocarbon and carbon monoxide emissions with the methane number are not so obvious as for diesel pilot ignition combustion. For both diesel pilot ignition and reactivity controlled compression ignition combustion, the nitrogen oxides emissions show a strong dependence on combustion phasing rather than natural gas composition. Overall, to control diesel pilot ignition combustion, the methane number should be considered together with other parameters. However, attention should be paid to other control parameters for the reactivity controlled compression ignition combustion. The engine performance of reactivity controlled compression ignition is not sensitive to the variation of natural gas composition, so it can adapt to the natural gas from different sources.

Numerical and optical analysis of heterogeneous gas combustion with diesel pilot ignition in a commercial vehicle engine

A new optical measurement technology and a simulation methodology for supporting the combustion system development of a high-pressure gas-diesel combustion system are presented for the first time. With this combustion system, natural gas is directly injected with high pressure into the combustion chamber near top dead center. The simulation methodology is being validated by comparison with a commercial vehicle single-cylinder metal engine and combustion imaging on a commercial vehicle optical engine with full optical access to the combustion chamber through a contoured piston window. For the optical analysis of the gas-diesel combustion system, a measurement setup for the combined two-dimensional imaging of the OH* chemiluminescence and the soot luminescence is being developed. These images allow the ignition characterization and the cyclic stability of combustion to be analyzed. With the support of the simulation methodology, the nozzle-bowl configuration can be designed with regard to optimum mixture formation and low emissions. A thermodynamic validation of the simulation results shows good agreement of the ignition timing and the following combustion phases with heat release rate data obtained from measurements. Furthermore, the end of engine soot concentrations are captured quantitatively well. A local comparison of optical images and simulation data demonstrates that the simulation is able to capture the gas ignition zones well. The combustion intensity and thus the local soot formation are slightly underpredicted in the center of the gas jets. However, the mixture formation and the overall regions of soot formation are in good agreement with the optical images.

Innovative Survey on Dual Fuel Engine with Fuel Essences

Alternative fuels have been getting more attention as concerns escalate over exhaust pollutant emissions produced by internal combustion engines, higher fuel costs, and the depletion of crude oil. Various solutions have been proposed, including utilizing alternative fuels as a dedicated fuel in spark ignited engines, diesel pilot ignition engines, gas turbines, and dual fuel and bi-fuel engines. Among these applications, one of the most promising options is the diesel derivative dual fuel engine with natural gas as the supplement fuel. This study aims to evaluate diesel and dual fuel combustion in a di ethyl eater-diesel dual fuel engine. More dual fuel engines are being utilized due to stricter emission standards, increasing costs of diesel fuel and decreasing costs of di ethyl eater. Originally sold as diesel engines, these units are converted to di ethyl eater-diesel fuel engines using an aftermarket dual fuel kit. As di ethyl eater is mixed with diesel, the amount of diesel used is reduced. The maximum di ethyl eater substitution is limited by knock or emissions of carbon monoxide and total hydrocarbons.