Diesel Methanol Dual Fuel Mode Research Articles

Experimental investigation on combustion and emission characteristics of diesel methanol dual fuel (DMDF) engine at various altitudes

In order to reveal the effects of diesel and diesel methanol dual fuel (DMDF) on engine performance at different altitudes, especially on combustion stability. In this study, a comparison of experimental research on characteristics of combustion, economy, and emissions for a turbocharged DMDF at various simulated altitudes (10m, 700m, 1670m, and 2400m) and three working conditions (1200rpm-72 Nm, 1800rpm-158 Nm, and 2200rpm-153 Nm) were conducted and analyzed combustion characteristics, economy and emissions. At 1800rpm and 2200rpm, with the increment of altitude, the peak value of the cylinder pressure, the pressure rise rate, and the brake thermal efficiency (BTE) for DMDF mode were higher than diesel mode, while combustion center (CA50) and combustion duration of diesel mode higher than DMDF mode. At 1200rpm and 1800 rpm, the maximum heat release rate (HRR) of DMDF mode was higher than diesel mode. When the altitude rose from 10m to 2400m, the coefficient of variation of peak pressure (COVPP) of DMDF mode increased while the coefficient of variation of indicated mean effective pressure (COVIMEP) of DMDF mode decreased, which means the combustion of dual-fuel is relatively stable. The exhaust temperature of DMDF mode was lower than that of diesel mode at various altitudes. Compared with diesel mode, NOX and Soot emissions in DMDF model significantly decreased at different altitudes and working conditions.

Multiple combustion modes existing in the engine operating in diesel methanol dual fuel

Four typical combustion modes were found in a diesel methanol dual fuel (DMDF) engine, which subverted the traditional viewpoint that the methanol was only ignited by diesel fuel spray. In this manuscript, the results of different combustion modes from constant volume combustion chamber (CVCC), compression ignition (CI) engine and numerical simulations were presented. In DMDF mode 1, diesel and methanol mixture were ignited simultaneously by compression. The role of diesel was the cetane number improver of methanol. In DMDF mode 2, part of diesel formed the mixture of theoretical equivalent ratio and was firstly ignited. Therefore, the role of the firstly ignited diesel in the combustion process was to ignite methanol. In DMDF mode 3, premixed methanol was auto-ignited before diesel injection, which resulted in two obvious heat release rate (HRR) peaks of methanol combustion and diesel combustion in the cylinder. In DMDF mode 4, the combustion process was slow. Therefore, the duration of combustion increased and a large amount of methanol remained unoxidized at the end of the combustion. The role of diesel in this mode was pilot ignition. The thermal efficiency of the first and second combustion modes was higher among the four combustion modes, and the first one was the highest. The results obtained will provide more clean and high thermal efficient combustion mode for dual fuel engines.

In-depth comparison between pure diesel and diesel methanol dual fuel combustion mode

Diesel Methanol Dual Fuel (DMDF) could achieve high efficiency and low emissions simultaneously at part of engine conditions, but the reason of this has not been clarified. In order to find the reason behind this phenomenon, Pressure-Volume (P-V) map, equivalence ratio (φ)-temperature (T) map and three-dimensional simulation software were used to compare diesel and DMDF mode, and two test conditions were selected to fulfill in-depth comparison of two combustion modes. Based on the analysis of P-V map, the reason of higher thermal efficiency at DMDF mode is as follows: lower cylinder pressure in compression stroke contributes to compression work reduction. Meanwhile, higher combustion rate of DMDF mode could reduce cylinder temperature and pressure in the late power stroke, which would further decrease exhaust loss and heat loss. Based on the analysis of φ-T map, higher methanol substitution percent could reduce the intersection area between cylinder φ-T map and nitric oxide & soot generation region. And after analyzing in-cylinder temperature, hydroxy mole fraction together with the equivalent ratio three-dimensional cloud map, it is found that the inhibitory effect of methanol on diesel low-temperature combustion prolongs diesel ignition delay, which helps to form the homogeneous charge in the cylinder. Under DMDF mode, fuel rich areas are significantly reduced, so is the maximum in-cylinder temperature. This is the key to achieve ultra-low nitrogen oxides and soot emissions for DMDF mode.

Experimental study of the active and passive regeneration procedures of a diesel particulate filter in a diesel methanol dual fuel engine

The diesel methanol dual fuel (DMDF) technology has been used in diesel engines to reduce the nitrogen oxides (NOX) and particulate matter (PM) emissions in past years. A combination of a diesel oxidation catalyst (DOC) and a diesel particulate filter (DPF) is applied on DMDF engines to meet severer emission standards in this study. The DOC was modified to produce adequate nitrogen dioxide (NO2) in the presence of the high hydrocarbon and carbon monoxide emissions formed by DMDF mode. During tests, the effect of methanol substitution ratio (MSR) and DOC inlet temperature on DOC performance was studied. Moreover, the effect of MSR on the active and passive regeneration of DPF was investigated. Results show that at high DOC inlet temperatures (>190 °C), the DMDF mode combined with DOC achieves the high DPF inlet temperatures and the high NO2/PM ratio, which is benefit for passive regeneration. During active regeneration, the initial regeneration temperature, the fuel penalty and the emissions of PM, particulate number (PN), NO2 and carbon dioxide (CO2) after the DPF at MSR40 are lower than those at MSR0. The emissions of methanol (CH3OH) and formaldehyde (HCHO) after the DPF at MSR40 are higher than those at MSR0. During passive regeneration, the regeneration rate at MSR40 is higher than that at MSR0, as well as the emissions of PN, CH3OH and HCHO after the DPF. While the NO2 and CO2 emissions after the DPF at MSR40 are lower than those at MSR0.

Strategy of improving fuel consumption and reducing emission at low load in a diesel methanol dual fuel engine

The experiments were performed to achieve a significant reduction in nitrogen oxides (NOx) and soot emissions while achieving no reduction in Brake Thermal Efficiency (BTE) for Diesel Methanol Dual Fuel (DMDF) engine at low load condition. The optimization strategies mainly include internal exhaust gas recirculation (EGR), external EGR, intake air heating and diesel injection timing retarded. NOx and soot emissions, BTE, and combustion characteristics were discussed. Experiments were conducted at 1660 r/min with the output torque 220 N·m, corresponding to 50% of full engine load. The main parameters for evaluating the optimization results include NOx emissions, soot emissions, BTE, Pressure Rising Rate (PRR) and fuel cost. The optimized result of DMDF mode is obviously better than those of diesel mode. The optimization process for DMDF mode weakens the trade-off relationship between key parameters which includes NOx emissions, soot emissions, BTE, PRR and fuel cost. Meanwhile, NOx emissions are significantly lower than those from the baseline diesel mode, which decreases from 9.76 to 1.53 g/kW.h. Soot emissions are almost maintained at the level of the baseline diesel mode. The optimized fuel cost of DMDF mode is greatly improved, and the BTE is slightly higher than that of baseline diesel mode.

Experimental study on energy balance of different parameters in diesel methanol dual fuel engine

Based on the first law of thermodynamics, this paper presents the experimental results of parameter study on energy balance of a diesel methanol dual fuel (DMDF) engine including load characteristic tests for both pure diesel (D) mode and DMDF mode and comparison of energy flow conversion under different load ratios. The results show that replacement ratio keeps decreasing with load increases. In addition, operating parameters, including cooling water temperature, intake air temperature and methanol temperature, were investigated to explore their effects on energy flow distribution in DMDF engine. The results show that increasing intake air temperature has the most important effect on reducing DMDF engine’ s replacement ratio. Besides that, higher cooling water temperature and methanol temperature also contribute to improving DMDF engine’s thermodynamics performance. All these phenomena can be explained by the energy flow transformation when switching to DMDF combustion. On the basis of the above analysis results, some feasible measurements are proposed to further improve DMDF engine’s thermodynamic behavior.

Experimental investigation on methanol auto-ignition in a compression ignition engine under DMDF mode

At high loads, Diesel-Methanol Dual Fuel (DMDF) engines strongly rely on high methanol substitution for diesel proportion (MSP) to achieve high efficiency combustion and reduce nitrogen oxides (NOx) and soot emissions. However, high MSP is limited by the probability of methanol auto-ignition. The experimental study was conducted to investigate into the influence factors of methanol auto-ignition under diesel engine conditions at 50% of full load. Meanwhile the testing results concerning combustion characteristics and emissions have been analyzed. Experimental results showed that if there was apparent heat release before TDC, which was earlier than diesel fuel injection, it indicated that methanol auto-ignition occurred. In order to avoid methanol auto-ignition which is very easily to cause knock or rapid pressure rise, the in-cylinder mean temperature should be less than 990 K (at this case, the intake temperature was 338 K) before diesel injection timing. As intake temperature increased, methanol heat release timing was advanced and the heat release rate (HRR) was gradually accelerated. If the injection timing of diesel was later than that of methanol auto-ignition, almost all diesel fuel would be burned in the form of diffusion combustion in the methanol flame, leading to the increase of soot emissions. Methanol auto-ignition would be inhibited by EGR gas. The EGR and MSP had a great impact on both the ignition timing and the peak HRR of methanol auto-ignition. As EGR ratio increased, so did the incomplete combustion loss of methanol. As long as methanol auto-ignition occurred, the increase of MSP would result in a decrease in NOx emissions, but soot emissions were increased instead.

An investigation on the characteristics of and influence factors for NO2 formation in diesel/methanol dual fuel engine

It had been found in previous experimental studies that the compression ignition engine with Diesel/Methanol Compound Combustion (DMCC) could significantly increase nitrogen dioxide (NO2) emission, compared with conventional diesel mode. However, the detailed formation process and influence factors of NO2 in Diesel/Methanol Dual Fuel (DMDF) engine have not been reported previously. In order to investigate the mechanism of increased NO2 and effect factors of NO2 emission, following works were conducted: Firstly, in light of the literature researches, a hypothesis concerning the NO2 formation procession in DMDF engine was presented, whose demonstration was realized by using numerical simulation; Secondly, the experiments about the effect of methanol substitute proportion (MSP), exhaust gas recirculation (EGR) and exhaust backpressure on the NO2 emission were conducted, whose results were analyzed by using the proved hypothesis. The results of simulation justified that compared with diesel case, the existence of methanol premixed region in DMDF mode was the main cause of increased NO2, and the impact of temperature on the NO2 emission mainly lay in that of temperature on hydroperoxyl (HO2) radicals. The experiments showed that along with the increase of MSP, NO2 emission increased firstly and then decreases. The addition of EGR could lead to the reduction of NO2, while the slight increase of exhaust backpressure would increase total nitrogen oxides (NOX) emission.

Effects of pilot injection strategy of diesel fuel on combustion characteristics in a premixed methanol-air mixture atmosphere in a CVCC

The experimental research on effects of diesel pilot injection strategy, including pilot injection timing (t2) and mass (mdp), on the combustion of diesel in a premixed methanol-air mixture atmosphere were conducted in a newly developed constant volume combustion chamber (CVCC), where both methanol and diesel fuel were injected directly into the chamber. Results showed that pilot injection makes the ignition of main injection advance; ignition position move towards the nozzle tip; and the natural flame luminosity become stronger. In diesel/methanol dual fuel mode (DM), the wrinkles on the flame surface are more complicated and the area of natural flame luminosity is larger, especially in earlier t2 or more mdp conditions. Pilot injection shortens ignition delay and ignition delay in DM is longer than that in diesel fuel mode (D). But when the interval between pilot and main injection (Δt2) is longer than 2 ms or mdp is more than 3.28 mg, ignition delay in DM becomes shorter instead. In D the changes of Δt2 and mdp have no significant effects on flame lift-off length (FLoL). But FLoL shortens gradually with the advance of t2 and the increase of mdp in DM. After adding pilot injection, the start of spatially integrated natural luminosity (SINL) rising advances and SINL peak increases. TINL in DM is lower than that in D. But when Δt2 is longer than 2 ms or mdp is more than 3.28 mg, TINL in DM becomes higher instead. Pilot injection can change heat release rate (HRR) from bimodal to unimodal and reduce the HRR peak of main combustion simultaneously.

Effect of diesel late-injection on combustion and emissions characteristics of diesel/methanol dual fuel engine

The late-injection strategy (close after main-injection) of common-rail diesel engine is capable of enhancing combustion turbulence and reducing particulate matter (PM) emissions. In this work, experimental study was performed to investigate the effect of diesel late-injection on combustion and emissions characteristics of diesel/methanol dual fuel (DMDF) engine. The experiments were carried out at a constant engine speed of 1340 rpm and a medium load of 1.0 MPa brake mean effective pressure (BMEP) with various methanol substitution ratio (MSR) on a common rail DMDF engine. The results reveal that higher MSR caused simultaneous decrease of nitric oxides (NOx) and accumulation mode PM emissions in spite of late-injection strategy. In particular, an augment of up to 12.8% in nucleation mode particle number (PN) was observed as MSR increased from 15% to 50%. A small late-injection of diesel (<7.5 mg/cycle) had little impact on in-cylinder pressure and heat release rate (HRR). However, enhanced or retarded late-injection led to a decline in peak gas mean temperature (GMT) but an increase in later combustion temperature. With late-injection quantity (LIQ) increased from 1.5 mg/cycle to 7.5 mg/cycle, both NOx and accumulation mode PM decreased. Meanwhile, nucleation mode PM was almost unchanged and even rebounded slightly with overmuch LIQ (7.5 mg/cycle) in DMDF mode. Retarded late-injection led to a continuous reduction of 12.9% at most in NOx emissions in DMDF operation. As the interval between main-late injections (MLII) increased from 800 μs to 1200 μs, a trade-off relation appeared between nucleation mode and accumulation mode particles due to the mutual transformation of them. Furthermore, too delayed late-injection (MLII > 1200 μs) induced a simultaneous increase of particles with different size.

Effects of co‐combustion ratio on rapid combustion, cyclical variation, and emissions of a heavy‐duty diesel engine fueled with diesel‐methanol dual‐fuel

Diesel‐methanol dual‐fuel (DMDF) combustion was achieved on a 6‐cylinder, heavy‐duty, turbocharged and common‐rail diesel engine. In DMDF mode, the coal‐produced methanol is induced to the upstream of the intake manifold and premixed with the fresh air to form a homogeneous methanol‐air mixture and then ignited by direct‐injected pilot diesel in cylinder. The purpose of this study is to investigate the effects of co‐combustion ratio (CCR) on the rapid combustion, cyclical variation and emissions of the DMDF engine. The experimental results show that CCR affect the rapid combustion (α) and knock tendency (β) greatly. With CCR increasing, both α and β increase significantly. The β exhibits an obviously large value under heavy load although CCR and α are small. At larger CCR, DMDF mode may generate a seriously cyclical variation and the coefficient of variation for indicated mean effective pressure (COVIMEP) exhibits a relatively large value. However, with engine load increasing, the cyclical variation can be obviously decreased. It is also shown that both NOx and smoke emissions in DMDF mode present an obviously decrease trend, while CO and HC emissions exhibits an increase trend. A further reduction of NOx and smoke emissions can be obtained by increasing CCR, but CO and HC emissions are increased in this case. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1528–1536, 2017

Effects of diesel injection parameters on the rapid combustion and emissions of an HD common-rail diesel engine fueled with diesel-methanol dual-fuel

The diesel-methanol dual-fuel (DMDF) combustion mode is performed on a 6-cylinder, heavy duty (HD), common-rail diesel engine. In DMDF mode, the methanol is premixed with air in the intake pipe and afterwards ignited by the direct-injected diesel in cylinder. This study is aimed to investigate the effects of diesel injection parameters on the rapid combustion and emissions of the DMDF engine. The experimental results show that the diesel injection parameters affect rapid combustion fraction (α) greatly, which increases as the diesel injection pressure rises while decreases as the diesel injection timing advanced or diesel injection quantity increases. The roar-combustion level of the DMDF engine is mainly controlled by the heat release rate (HRR) of rapid combustion phase. Both increasing the diesel injection pressure and advancing the diesel injection timing are beneficial to intensify roar-combustion level, but it can be weakened by increasing diesel injection quantity. Compared with original diesel combustion mode (D mode), NOx and smoke emissions in DMDF mode are all reduced, while CO and HC emissions increased obviously. Smoke emission can be further reduced by coupling the high diesel injection pressure and the advanced diesel injection timing. However, NOx emission may be increased in this case.

Effects of rapid burning characteristics on the vibration of a common-rail diesel engine fueled with diesel–methanol dual-fuel

The diesel–methanol dual-fuel (DMDF) combustion mode is conducted on a six-cylinder, turbo-charged, inter-cooled diesel engine. In DMDF mode, methanol is injected into the intake pipe to premix methanol and air, and then ignited by the direct-injected diesel in cylinder. This study is aimed to investigate the effects of rapid burning characteristics on the vibration performance of the DMDF engine. The experimental results show that the combustion process of the DMDF engine can be divided into two phases. The rapid burning characteristics, the centroid angle of rapid burning (α) and the rapid burning fraction (β) have important influence on the vibration characteristics of the DMDF engine. The co-combustion rate (CCR) and engine load affect β greatly, and diesel injection timing also affects α and β greatly. However, the diesel injection pressure has little effect on rapid burning characteristics. By means of optimized diesel injection timing and pressure, the vibration can be reduced and the peak value of CCR can be increased.

Theoretical and experimental investigations on energy balance on DMDF engine

This paper presented the analytical results for the energy balance of a diesel methanol dual-fuel (DMDF) engine. A methanol injection system was fixed on a diesel engine and let the engine to alternate to run in either the pure diesel (D) mode or DMDF mode. Primary application of the thermal balance analysis was to investigate the cause of methanol replacement ratio SR changing with engine loads. Calculations were conducted within the control volume by comparing each of the energy terms. The results show that the reduction in cooling loss in DMDF mode is the dominant factor for low SR at high loads. While, a substantial increase in incomplete combustion loss in DMDF mode is the most important reason for high SR at low loads. Another application of the thermal balance analysis was to research the cooling loss in DMDF mode which implied unique characteristics. Therefore, the changing methanol replacement rate SP experiments were carried out in various engine loads, giving the results that the cooling loss in DMDF mode is always lower than that in D mode, and it goes even lower as SP rises. Finally, the effect of methanol temperature on SR was also investigated from the thermal balance point of view. The results reveal that the incomplete combustion loss decreasing in higher methanol temperature conditions will lead to a certain extent of SR drop. All these results are related to the energy flow distribution within the engine.

Numerical Study of Combustion and Emission Characteristics of a Diesel/Methanol Dual Fuel (DMDF) Engine

In comparison to the extensive experimental studies, numerical studies of a diesel/methanol dual fuel (DMDF) engine are very limited. In this work, an improved KIVA-3V code was coupled with the CHEMKIN solver to model combustion and emission of a DMDF engine. First, a chemical reaction mechanism including 65 reactions and 43 species was developed and validated with premixed flame species profiles. Second, new engine experiments at varied loads in both diesel and DMDF modes were performed to further validate the present model. Results show that the model predicts the engine combustion and emission in two modes well. At last, parameter studies on diesel injection timings and exhaust gas recirculation (EGR) rates were performed. Results show that the ignition delay time in DMDF mode is longer than that in diesel mode. Methanol supplied through the intake port significantly reduces soot emissions and slightly increases NOx emissions at different injection timings. In two modes, soot emissions are both formed ...

Effect of DMDF on the PM emission from a turbo-charged diesel engine with DDOC and DPOC

This study is aimed to investigate the combined application of diesel methanol dual fuel (DMDF) and a simple after-treatment for reducing particulate matter (PM) emissions of a diesel engine. The effects of DMDF, a double diesel oxidation catalyst (DDOC) and a DOC closely coupled with a particulate oxidation catalyst (POC) in series (DPOC) on smoke emissions, particulate mass and number concentrations and size distributions were analyzed. Tests were conducted on a 4-cylinder turbo-charged, inter-cooling, mechanical in-line fuel injection pump diesel engine modified to DMDF combustion mode. Testing results showed that, before the DDOC and the DPOC, the dry-soot and smoke opacity efficiency decreases with the increase of substitution ratio of methanol at high engine load. There is a significant decrease of smoke opacity in DMDF mode after the DDOC, while the DPOC has a significant effect on the reduction in dry-soot emission. There is an average reduction in dry-soot by 25% in pure diesel fuel mode after the DDOC, while in DMDF mode, the average reduction is more than 60%, and the maximum reduction in dry-soot is up to 96%. There is a slightly reduction in PM emissions at low substitution ratio of methanol, while the high substitution ratio of methanol leads to more reduction in PM emissions. After the DDOC and the DPOC, particulate number and mass concentrations, especially nuclear particles, can be significantly reduced when the exhaust gas temperature is enough high.

Effects of diesel injection pressure on the performance and emissions of a HD common-rail diesel engine fueled with diesel/methanol dual fuel

The diesel/methanol dual fuel (DMDF) combustion mode was conducted on a turbo-charged, inter-cooling diesel engine with 6-cylinder for the heavy duty (HD) vehicle. In DMDF mode, methanol is injected into the intake port to form lean air/methanol premixed mixture, and then ignited by the direct-injected diesel fuel in cylinder. This study is aimed to investigate the effect of diesel injection pressure on the characteristics of performance and exhaust emissions from the engine with common-rail fuel system. The experimental results show that at low injection pressure, the IMEP of DMDF mode is lower than that of pure diesel combustion (D) mode. COVIEMP of DMDF mode firstly decreases and then increases with increasing injection pressure, and it remains under 2.1% for all the tests. It is found that the combustion duration in DMDF mode becomes shorter, the maximum cylinder pressure and the peak heat release rate increase, and CA50 gets close to the top dead center as the injection pressure increases. BSFC of DMDF mode decreases with the increase of injection pressure, and is lower than that of D mode for injection pressure over 115MPa. Both of NOX and smoke emissions are reduced in DMDF mode. But smoke decreases and NOX increases as the diesel injection pressure increases in DMDF mode. DMDF generates lower NO and CO2 emissions, while produces higher HC, CO, andNO2 emissions compared to D mode. As the diesel injection pressure increases, CO and HC emissions are decreased, however, CO2 and NO2 emissions are slightly increased.

Reduction of PM emissions from a heavy-duty diesel engine with diesel/methanol dual fuel

The effects of diesel/methanol dual fuel (DMDF) combustion, diesel oxidation catalyst (DOC) and intake air temperature on dry-soot and PM (particulate matter) emissions were investigated. Experiments were conducted on a 6-cylinder turbo-charged, inter-cooling HD (heavy duty) diesel engine modified to diesel/methanol dual fuel combustion mode. The pressurized methanol was induced into the intake manifold with six injectors and mixed with boost fresh air to form homogeneous mixtures and then ignited by pilot diesel in the cylinder. The amount of injected methanol was varied in accordance with engine power output while the amount of diesel fuel was remained constant under different operation conditions. Experimental results show that at low and medium loads, there is a significant decrease in the dry-soot emission in DMDF mode before the DOC, but a little increase at high load. An important phenomenon was observed that the mass and number concentrations of particulate matter significantly decrease at low and medium loads, due to the increase in fuel burned in the premixed mode and a reduction in diesel fuel involved, while they increase when the tested engine operates on the high engine condition, due to the spontaneous combustion of methanol and a reduction in oxygen for diesel in cylinder. After the DOC, the particulate mass and number concentrations are significantly reduced at all engine loads. Moreover, the temperature of intake air decreases with the increase of methanol injection, and the particulate number and mass concentrations in DMDF mode decrease with the decrease of the intake air temperature.