Diesel Methanol Dual Fuel Research Articles

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.

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.

To extend the operating range of high MSP with ultra-low emissions for DMDF unit pump engine

Experiments were conducted to extend the operation range of Diesel/Methanol Compound Combustion (DMCC), as to further reduce the emissions of Diesel Methanol Dual Fuel (DMDF) engine at full load. The engine was operated under 100% of full engine load at three different speeds of 1660 r/min (speed A), 2090 r/min (speed B), and 2520 r/min (speed C), respectively, as well as 75% of full load at the speed of 1660 r/min. At full load, the results showed that the methanol substitution for diesel proportion (MSP) of DMDF engine could be greatly extended to 80% by using suitable combustion control strategy, which was restricted less than 15% in the previous study. Simultaneously, the knock tendency was reduced into an unobservable magnitude at such a high MSP. Furthermore, the nitrogen oxides (NOx) emission could be significantly reduced, and the lowest NOx emission was down to 1.25 g/kW.h at MSP73 under A75 test point. Meanwhile, the soot emission could be reduced to ultra-low level when the diesel fuel injection duration is shorter than the ignition delay of diesel combustion. The lowest soot emission is decreased to 0.004 g/kW·h at MSP72 under B100 test point, which is lower than the requirement of EURO VI limitation. The results demonstrated that methanol has the advantage of smokeless and flameless while burning, thus soot production could be reduced when the engine fueled with more methanol fuel. The testing results also showed that the total hydrocarbons (THC) and the carbon monoxide (CO) emissions are increased with increasing MSP.

Mechanism analysis on controllable methanol quick combustion

This paper explored the reason that the amount of methanol consumed is much lower than that of its theoretical value in terms of calorific value in diesel methanol dual fuel (DMDF) combustion by the means of engine bench test and modeling analysis. The results from experiments show that, the DMDF has much higher combustion rate than that of the correspondent diesel (D) mode and the accelerating effect caused by methanol changes with engine load, methanol-air mixture concentration and intake air temperature. At low load condition, the ignition delay caused by methanol is dominated while the accelerating effect is weak. However, this situation just turned upside down at high loads, to bring forth great improvement in isochoric degree. When methanol conducts quickly burning, both the combustion efficiency and the conversion efficiency from heat to work are improved, and the replacement ratio SR becomes much lower than its theoretical value 2.16. In order to reveal the mechanism of high efficiency DMDF at various running conditions, a 3-dimensional CFD model to simulate and analysis the process of methanol burning together with diesel was built. By fixing constant operating parameters and boundary conditions, both the putting off and accelerating effects caused by methanol are enhanced with increasing methanol concentration. The putting off effect weakens with rising air temperature, while the accelerating effect becomes more effective in this process. Hence, the isochoric degree for DMDF deteriorates with rising air temperature at lean methanol mixture but improves as the concentration increases. Finally, a relational graph among isochoric degree, heat release concentration degree, methanol-air mixture concentration and temperature are derived, from which we get the understanding of controllable methanol quick combustion (CMQC) to further improve the DMDF thermal efficiency.

Comparison of the conversion efficiency of DOC and DPOC to unregulated emissions from a DMDF engine

The experimental research on reducing unregulated emissions (included unburned methanol, formaldehyde, formic acid, 1,3-butadiene, benzene and toluene) of diesel/methanol dual fuel (DMDF) engine with different after-treatment devices was carried out on a turbocharged inter-cooling diesel engine. The DMDF engine was operated under 25%, 50%, 75% and 100% of full load at the engine speed of 1660rpm and 2090rpm with the same injection parameters for the different methanol substitution ratios (MSR). Unregulated emissions of DMDF engine with and without after-treatment devices single diesel oxidation catalyst (DOC) and DOC coupled with particulate oxidation catalyst (DPOC) were studied in comparison. The results show that compared with pure diesel mode, the unregulated emissions tested in this research are all increased in different degrees when the engine operates on diesel/methanol dual fuel mode, and they are all increased with increasing fumigation methanol. The conversion efficiency of DPOC for unregulated emissions tested in this research is higher than that of single DOC. Single DOC could significantly reduce the unburned methanol, 1,3-butadiene and formic acid emissions from DMDF engine, especially at medium and high load when exhaust gas temperature is relative high, but formaldehyde emissions after DOC are increased at low load. After the catalytic oxidation of DPOC, the unburned methanol, formaldehyde, formic acid, benzene and toluene emissions of diesel/methanol dual fuel mode under all load at the speed of 1660rpm, all except low load at the speed of 2090rpm are not much different from pure diesel mode.

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

The impact of methanol injecting position on cylinder-to-cylinder variation in a diesel methanol dual fuel engine

Methanol fumigation strategy in multi-cylinder diesel engine has received great attentions in recent years. Experimental work was conducted in a turbocharged inline 4-cylinder diesel engine fueled with diesel methanol dual fuel (DMDF). Three different methanol injection positions were chosen to investigate into their effect on cylinder-to-cylinder variation. The results indicate that the unevenness degree of each cylinder reduces as injection timing of diesel (ITd) retarded. The unevenness degree of engine is better when methanol injectors are fixed at intake manifold (Case 1) and at distal end of inlet duct (Case 2) than fixed at near end of inlet duct (Case 3). The cylinder-to-cylinder variation has a tendency to increase with an increase in methanol substitution percent (MSP). With the increasing engine load, the COVIMEP of 4 cylinders reduces. In addition, the COVIMEP rises with an increasing MSP under 50% and 75% engine loads, while it has no significant change under 100% engine load. The COVpmax first increases and then decreases with the increase in engine load, and it has the maximum value under 75% engine load. Although there is a linear increase in the THC and CO emissions with the increase in MSP, the difference of THC and CO emissions between the three cases is very small under various engine loads. Under 50% and 75% engine loads, the soot emission in all three cases decreases slowly with the increase in MSP, and the difference of soot emission in three cases is small. Under 100% engine load, the soot emission in three cases first increases and then decreases with the increase in MSP, and the emission gaps fall apart further with the increase in MSP.

Experimental investigations of the effects of pilot injection on combustion and gaseous emission characteristics of diesel/methanol dual fuel engine

A diesel engine with 6-cylinder, turbocharged intercooling and common rail system was modified to operate on diesel/methanol dual fuel (DMDF). To optimize combustion process at high methanol substitution ratio (MSR) and further decrease exhaust emissions of DMDF engine at low load condition, pilot injection strategy was applied on it and the combustion, regulated and unregulated gaseous emission (included NOx, CO, THC, carbon dioxide (CO2), nitrous oxide (N2O), unburned methanol (CH3OH), formaldehyde (HCHO), formic acid (HCOOH), 1,3-butadiene (1,3-C4H6), benzene (C6H6) and toluene (C7H8)) characteristics were experimentally investigated. Experimental results reveal that the application of pilot injection could improve combustion stability and fuel economy at high MSR, and it can also reduce regulated emissions CO, THC except NOx, and unregulated emissions tested in this study except CO2 on M0 and M10 mode and toluene on M50 mode when compared with single injection cases. Increase pilot injection quantity and advance pilot injection timing both cause an increase in in-cylinder temperature and pressure before main combustion. The variations of pilot injection quantity and timing have less effect on regulated and unregulated gaseous emissions except NOx on M0 and M10 mode than higher MSR mode. With the rise of pilot quantity and the advance of pilot injection timing, HC and CO emissions decrease gradually but NOx emissions ascend; almost all unregulated emissions tested in this study on M30 mode reduce gradually; but when the MSR continues to rise to 50%, increasing emissions in unburned methanol, 1,3-butadiene and benzene are observed.

Mechanistic Study of Ignition Characteristics of Diesel/Methanol and Diesel/Methane Dual Fuel Engine

Diesel/natural gas dual fuel (DNDF) and diesel/methanol dual fuel (DMDF) both have very good potential for use in alternative energy technologies for internal combustion engine. In this work, a comparative study was done to better understand the ignition characteristics of dual fuel combustion. First, their apparent ignition characteristics were studied experimentally on a constant volume chamber and apparent ignition delay correlations of DNDF and DMDF were built; second, chemical kinetic analysis was used to explain the phenomenon observed; lastly, an improved KIVA-3 V code was applied to study the importance of the chemical interaction between diesel and methane or methanol on diesel ignition timing in an engine. Experimental results showed that both methanol and methane addition retarded the ignition of diesel and methane retarded less, which was due to the dehydrogenation of methanol and methane, reaction CH3 + HO2 = CH3O + OH and the formation of H2O2. CFD numerical results showed that, in the DMDF engine, the chemical interaction by methanol addition was the most important factor for the retarding of diesel ignition timing compared to other factors, such as the reduction of the amount of diesel, lower oxygen concentration, and the higher specific heat in the intake charge; in the DNDF engine, the effects of the chemical interaction and the reduction of the amount of diesel were comparable.

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.

Study of cylinder-to-cylinder variation in a diesel engine fueled with diesel/methanol dual fuel

The methanol fuel used in diesel engine can reduce the emissions effectively, while the performance of engine keeps unchanged or even improved, the study of methanol used in diesel engine is paid more and more attention. Experiments were conducted in a 4-cylinder, turbocharged direct injection diesel engine fueled with diesel/methanol dual fuel (DMDF). In the experiment, methanol was injected into inlet duct by two low-pressure injectors, and directly mixed with intake air before entering the engine. The diesel fuel was directly injected in cylinder. The methanol substitution percent (MSP), intake air temperature and engine speed were changed to investigate the unevenness degree (UED) cylinder-to-cylinder. The experimental results show that the UED of engine increases with the increase of MSP under various engine loads, the COVpp increases with MSP under low engine load, and the COVpp curves vary very little under low MSP under 75% and 100% engine load, but a significantly rise appeared when MSP further increases. The UED gradually increases with the increase of intake air temperature, and it is usually less than 8% when intake air temperatures lower than 80°C under 40% MSP. It suggests it is helpful to decrease the UED when the intake air temperature is in the range of 35–80°C as MSP less than 40%. In addition, the difference of pressure between cylinder-to-cylinder decreases with the increase of engine speed, it can be considered raising MSP at high engine speed in order to gain better engine economy.

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.

Study on cyclic variability of dual fuel combustion in a methanol fumigated diesel engine

An experimental study was conducted to investigate into the cyclic variations of diesel methanol dual fuel (DMDF) combustion on a methanol fumigated diesel engine. The effects of engine load, methanol substitution percent (MSP), injection timing and intake temperature on cyclic combustion variation were studied experimentally. In-cylinder pressure of 100 consecutive combustion cycles were recorded for each test case. The coefficient of variation (COV) of maximum in-cylinder pressure (pmax), maximum mass-averaged temperature (Tmax) and the indicated mean effective pressure (IMEP) were used to evaluate the cyclic variations of DMDF combustion. The results showed that the stability of DMDF combustion at high loads is comparable with that of neat diesel combustion. But the magnitude of cyclic DMDF combustion variations increases at light loads and more sensitive to the quantity of fumigated methanol. At light loads, COVpmax and COVTmax increase significantly and the crank angles corresponding to pmax and Tmax scatter more around with the increment of MSP. IMEP values show obvious fluctuations and are distributed in a wider range with an increase in MSP. DMDF combustion stability is very sensitive to intake temperature. At light loads the COVs of all combustion parameters decrease with the increment of intake temperature. In contrast, at high loads, the effect of intake temperature on the cyclic variations is quite small while there is a significant increase in the COVs when the intake temperature exceeds over 75°C. Overall, injection timings does no effect on cyclic variations of DMDF combustion.

Effect of intake pre-heating and injection timing on combustion and emission characteristics of a methanol fumigated diesel engine at part load

Diesel–methanol dual fuel (DMDF) engines at light loads suffer from low thermal efficiency and high unburned percentages of fuel. Pilot fuel injection timing and intake temperature are two important parameters which affect the combustion process in DMDF engines. In present experimental work, the combined effects of intake temperature and injection timing on the performance of a DMDF engine have been studied. The experiments were conducted on a methanol-fumigated diesel engine at 25% of full load and the results concerning performance, combustion characteristics and emissions were analyzed. Results show that the low efficiency at light loads can be improved significantly by raising the intake temperature and advancing the injection timing of direct-injected diesel. Increasing the intake temperature also significantly decreases the heat release rate of premixed combustion and increases the combustion rate of methanol burned by flame propagation. Flame propagation of the methanol–air mixture disappears gradually and DMDF combustion transforms into single stage combustion as the injection timing is retarded. When injection timing is retarded after 4.6° crank angle, misfire occurs at higher methanol substitute percent (MSP) and lower intake temperature, while the auto-ignition of methanol occurs at lower MSP and higher intake temperature. Under DMDF operation, soot and nitrogen oxides trade-off dilemma is completely broken at lower intake temperature and higher MSP.

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.

Investigation of operating range in a methanol fumigated diesel engine

An experimental study was conducted to investigate the operating range and combustion characteristics in a methanol fumigated diesel engine. The test engine was a six-cylinder, turbocharged direct injection engine with methanol injected into the intake manifold of each cylinder. The experimental results showed that the viable diesel methanol dual fuel (DMDF) operating range in terms of load and methanol substitution percent (MSP) was achieved over a load range from 6% to 100%. The operating range was restricted by four bounds: partial burning, misfire, roar combustion and knock. The lower bound of the operating range was the partial burn bound, which occurred under very low load conditions with high MSP. As the load increased to medium load, MSP reached its maximum value of about 76%, and the onset of misfire provided the right bound for normal operation. At medium to high load, maximum MSP began to decrease. DMDF combustion with excessive MSP was extremely loud with high pressure rise rate, which defined the roar combustion bound. As it increased to nearly full load, measured pressure traces in-cylinder showed strong acoustic oscillations. The appearance of knock provided the upper bound of the operating range. In general, as the load increased, the characters of the combustion changed from partial burn to misfire to roar combustion and to knocking. The range between these four bounds and the neat diesel combustion bound constituted the viable operating range. Over the viable operating range, DMDF combustion worsened the brake thermal efficiency (BTE) at light load while boosted it at medium and high load.