Methanol Injection Timing Research Articles

Hydrogen enrichment in methanol SI engine at varying injection timing during compression stroke

This study investigates the effect of hydrogen enrichment in a direct-injected methanol-fuelled SI engine, with combustion and emission performance analysed by varying the methanol injection timing from 150° to 60° CA bTDC. A three-dimensional computational fluid dynamic model of the hydrogen-enriched methanol engine was developed to predict the engine performance, in-cylinder, and emission characteristics. The numerical model was solved using three-dimensional Reynolds-Averaged Navier Stokes, the RNG k-epsilon model for turbulence, the O'Rourke and Amsden sub-model for heat transfer, the extended Zeldovich mechanism for nitric oxide emissions, and the Hiroyasu-NSC model for soot emissions. The results indicated that retarding the injection timing resulted in a decrease in the indicated specific CO and soot emissions along with a rise in the indicated specific NOx emissions. Furthermore, hydrogen enrichment with methanol enhanced the hydroxyl radical concentration, reduced the combustion duration, reduced also the indicated specific CO and soot emissions while increasing the indicated specific NOx emissions. The study indicates that hydrogen enrichment could extend the late injection timing limit of methanol by enhancing fuel-air mixing, which improves and controls the combustion process more effectively.

Experimental study on the effects of water addition in methanol on the performance of diesel-methanol diffusion combustion on a high-speed engine

Methanol is regarded as a low-carbon renewable fuel which is friendly to the environment. For purpose of investigating the impact of water introduction in methanol on diesel-methanol diffusion combustion, experimental tests were performed on a refitted dual-fuel high-speed diesel engine test bench. This research compared the differences between diesel-methanol diffusion combustion (DMDC) mode and diesel-hydrous methanol diffusion combustion (DHMDC) mode with a water mass content of 20%. The tests were performed by maintaining the engine speed of 3000 rpm and varying engine load as well as methanol injection timing (MIT). The results indicate that the heat release process in DHMDC mode begins later but is more rapid and concentrated compared to DMDC mode. The addition of 20% water in methanol does not significantly decreases the peak average in-cylinder temperature. However, it decreases the NOx emissions by up to approximately 40%. Water introduction leads to higher CO and THC emissions in DHMDC mode, but the retardation of MIT helps mitigate the increase in CO and THC emissions. The exhaust losses in DHMDC mode decrease by about 5%–8%, while the heat transfer losses increase by over 20%, resulting in a lower indicated thermal efficiency (ITE) in comparison with DMDC mode. The effects of the 20% water addition in methanol are sensitive to changes in engine load and MIT. Higher engine load and appropriately retarded MIT facilitate more efficient and cleaner combustion in DHMDC mode.

Investigation on formaldehyde generation characteristics and influencing factors of PODE/methanol dual-fuel combustion mode.

Polyoxymethylene dimethyl ether (PODE) and methanol are important low-carbon substitutable fuels for reducing carbon emissions in internal combustion engines. In the research, the impacts of methanol ratio, injection timing, and intake temperature on HCHO generation and emission were investigated using both engine tests and numerical simulations. Results suggest that an increase in methanol ratio suppresses auto-ignition tendency of PODE, leading to the increase of ignition delay period, pressure peak, and heat release rate peak inside the cylinder. The decrease in in-cylinder combustion temperature contributes to an increase in HCHO emission due to partial oxidation of methanol in the cylinder and exhaust pipe. While the injection timing is gradually postponed from -10 °CA ATDC to 2 °CA ATDC, in-cylinder high-temperature area decreases, the quantity of unburned methanol increases, but part of HCHO is converted to HCO due to H radical influence, resulting in 72% increased HCHO emission. With the increment of intake temperature, the oxidation and decomposition of in-cylinder methanol accelerate, leading to an improvement in combustion stability, more uniform temperature distribution, and a decrease in unburned methanol, which results in lower HCHO emission. When the intake temperature is rose from 30 to 60 °C, HCHO emission decreases by 11.2%.

Experimental Investigation on the Effects of Direct Injection Timing on the Combustion, Performance and Emission Characteristics of Methanol/Gasoline Dual-Fuel Spark Turbocharged Ignition (DFSI) Engine with Different Injection Pressures under High Load

The exceptional properties of methanol, such as its high octane number and latent heat of evaporation, make it an advantageous fuel for efficient utilization in dual-fuel combustion techniques. The aim of this study is to investigate the effect of direct methanol injection timing on the combustion, performance and emission characteristics of a dual-fuel spark ignition engine at different injection pressures. We conducted four different direct injection pressure tests ranging from 360° ahead to 30° CA ahead at 30° CA intervals. The experimental results indicate that regardless of the injection pressure, altering the methanol injection timing from −360° to −30° CA ATDC leads to distinct combustion behavior and changes in the combustion phase. Initially, as the injection timing is delayed, the combustion process accelerates, which is followed by a slower combustion phase. Additionally, the combustion phase itself experiences a delay and then advances. Regarding performance characteristics, both the brake thermal efficiency (BTE) and exhaust gas temperature (EGT) exhibit a consistent pattern of first increasing and then decreasing as the injection timing is delayed. This suggests that there is an optimal injection timing window that can enhance both the engine’s efficiency and its ability to manage exhaust temperature. In terms of emissions, there are different trends in this process due to the different conditions under which the individual emissions are produced, with CO and HC showing a decreasing and then increasing trend, and NOx showing the opposite trend. In conclusion, regardless of the injection pressure employed, adopting a thoughtful and well-designed injection strategy can significantly improve the combustion performance and emission characteristics of the engine. The findings of this study shed light on the potential of methanol dual-fuel combustion and provide valuable insights for optimizing engine operation in terms of efficiency and emissions control.

Effect of direct methanol injection based on low-flow injector on knock of gasoline engine under heavy load condition

Under appropriate strategies, direct methanol injection can suppress the knock effectively. In this paper, methanol was injected as an anti-knock agent by modified low-flow direct injectors into the cylinder of a high-load port injection gasoline engine. The effects of methanol injection timing and methanol ratio on knock suppression were investigated. The knock intensity (KI), knock probability, and auto-ignition timing were used as the primary basis for quantifying the knock. The results show that methanol injection timing has a significant impact on combustion. Maximum knock suppression can be achieved when methanol is injected near the bottom dead center. The too-early and too-late injections will affect the knock suppression. There was an apparent knock phenomenon when methanol was injected near the end of the compression stroke. When the ratio of methanol is meager, methanol will instead increase the intensity of the knock. As the methanol ratio rises, the knock is gradually and effectively suppressed. There is a specific methanol ratio beyond which higher methanol ratios do not significantly increase the knock suppression effect. When methanol was injected late in the compression stroke, low methanol ratios did not seriously increase the knock intensity, but high methanol ratios did not eliminate the knock either.

Co-optimization of injection parameters and injector layouts for a methanol/diesel direct dual-fuel stratification (DDFS) engine

Direct dual fuel stratification (DDFS) is a promising combustion mode to achieve satisfactory engine performance with the effective control of ignition and combustion processes. In this study, a DDFS engine fueled with methanol and diesel was investigated at low loads based on a four-stroke light-duty naturally aspirated engine. Both injection parameters and injector layouts of the two fuels were co-optimized by the fast nondominated sorting genetic algorithm (NSGA-II). The results show that the fractions, injection timings, spray half-included angles, and injector positions of the two fuels all showed significant influences on engine performance. Finally, the high methanol fraction, advanced diesel injection timing, methanol injection timing near the top dead center, and large spray half-included angle of methanol were adopted in the optimal case to achieve both low EISFC and NOx simultaneously. Meanwhile, a centrally-mounted methanol injector was beneficial to shorten combustion duration, and the diesel injector can be arranged in a semicircle area with a radius of approximately 1.14 cm to provide the sufficiently high temperature for the complete combustion of methanol.

A comparative study on operating range and combustion characteristics of methanol/diesel dual direct injection engine with different methanol injection timings

Improved combustion and reduction in emissions levels could be achieved with optimization of in-cylinder fuel–air mixing. According to the engine operating condition, the spatial and temporal features of in-cylinder mixture can be flexibly and accurately adjusted by methanol/diesel dual direct injection in real time. Present research investigated the effect of dual direct injection strategy on the operating range, combustion and emissions characteristics of a methanol/diesel dual direct injection engine. The results showed that the limits of the engine operating range could be obtained by observing the unstable and roar combustion in the cylinder when the methanol was injected directly during the intake stroke. The onset of roar combustion provided the upper bound of operating range at the methanol injection timing (SOIM) of − 60 °CA aTDC. High indicated thermal efficiency (ITE) could be achieved accompanied by widening the operating range of the engine. Systematic analysis results of combustion characteristics indicated that the increments of engine load and methanol energy substation ratio (ESR) were conducive to improving the combustion stability of the engine. Because of the reduced diffusion-controlled combustion, the methanol/diesel dual fuel direct injection strategy could realize a relatively low NOx emissions, which were insensitive to the SOIM at low ESR conditions. With the increase of ESR, injecting methanol close to TDC resulted in lower CO and HC emissions, especially at higher engine load conditions. This study confirms that the implementation of dual direct injection strategy has the potential to extend the operating range of a methanol/diesel engine, accompanied with high fuel economy and low emissions.

Optical investigations on ignition and combustion characteristics of polyoxymethylene dimethyl ethers/methanol blends

ABSTRACT Internal combustion engines using carbon-neutral fuels are effective ways to achieve low CO2 emissions. Polyoxymethylene dimethyl ethers (PODE) and methanol are carbon-neutral fuels, both good alternative fuels for engine combustion. Dual-fuel combustion modes have been widely studied, but investigations on the ignition and combustion characteristics of PODE/methanol at blending mode are still lacking, especially in optical engines. In this study, the effects of methanol blending ratios (0, 10, 20%), intake temperatures (45, 85, 120°C), and injection timings (−60, −45, −30, −15 °CA aTDC) on the ignition and combustion behavior of PODE/methanol blends were optically studied. Synchronization measurements of in-cylinder pressure and high-speed photography were performed for combustion analysis. The results show that a reduced methanol blending ratio, increased intake temperature, and intermediate injection timing exhibit positive influences on flame initiation and combustion evolutions. Specifically, an optimized methanol blending ratio, intake temperature, and injection timing can shorten the ignition delay time by 11.2, 6.1, and 39.2 crank angles, respectively. Meanwhile, unlike methanol blending ratio and intake temperature, injection timing can significantly affect early-stage rapid combustion duration. Optical images show that multiple flame kernels are initially induced at local rich regions with shorter ignition delay time, while when ignition delay time becomes longer, flame kernels start to be discretely distributed throughout the combustion chamber. These observations demonstrate the significance of the competition between chemical reactivity and fuel stratification in ignition and combustion characteristics of PODE/methanol blends.

Effects of fuel injection timings and methanol split ratio in M/D/M strategy on a diesel/methanol dual-fuel direct injection engine

• Effects of fuel injection timings and split ratio in M/D/M strategy are investigated. • Too advanced methanol injection leads to wall wetting and too delayed leads to knock. • Delayed diesel injection and large dwell could reduce knock intensity effectively. • Excessive split ratios at high load should be avoided to prevent knock. To improve fuel economy and emissions of a diesel/methanol dual-fuel direct injection engine at high load, a methanol/diesel/methanol (M/D/M) strategy is proposed and investigated. This M/D/M strategy consists of injecting a portion of methanol in the compression stroke to form a certain concentration of premixed charge, then injecting diesel near the TDC to ignite the premixed methanol/air mixture, and finally injecting the rest methanol into the flame to achieve diffusion combustion. In this work, a numerical study is conducted to investigate the effects of fuel injection timings and methanol split ratio (SR) in the M/D/M strategy. The results show that too advanced methanol injection timing (M SOI ) leads to wall wetting while too delayed M SOI easily leads to knock; M SOI -30 is the most suitable setting to avoid these undesirable outcomes. Delayed diesel injection timing (D SOI ) and large dwell can control knock intensity effectively. Moreover, increasing SR properly helps to improve fuel economy, while an excessive SR is prone to knocking. Accounting for engine performance and emissions, a SR of 50:50 paired with a M SOI -30/D SOI -5/M SOI -3 setup is the best overall configuration.

Optical diagnostics of methanol active-thermal atmosphere combustion in compression ignition engine

Methanol has become one of the research hotspots of internal combustion engine in recent years. One method of methanol compression ignition is that create in-cylinder active-thermal atmosphere to ignite direct injection (DI) of methanol. However, the combustion essences and related mechanisms in methanol active-thermal atmosphere combustion (ATAC) have not been comprehended. In current study, the characteristics of methanol ATAC were investigated on a light-duty engine using different optical diagnostics. Polyoxymethylene dimethyl ethers (PODE2) and n-heptane were chosen as port injection (PI) fuel respectively, and methanol was used as DI fuel. The experiment results indicate that methanol ATAC with PI of PODE2 is divided into two combustion processes. One process is the premixed combustion of PODE2 and the partially premixed combustion (PPC) of methanol, which appears that the premixed blue flames of PODE2 and the partially premixed yellow flames of methanol. The other is PODE2 premixed combustion and methanol diffusion combustion, which presents that the premixed blue flames of PODE2 and the yellow spray diffusion flames of methanol. Both the heat release rate and the flame structure of methanol ATAC can be adjusted by changing DI timing. The increase of PI energy proportion advances the timing of premixed blue flames of PODE2. The DI of methanol is driven by spray diffusion flames unless the methanol injection timing is earlier than high temperature heat release of PODE2. The capability of PODE2 to make methanol auto-ignited is higher than that of n-heptane. The methanol energy proportion can achieve 70% in PODE2 case, while achieve merely 30% in n-heptane case. Kinetic analysis reveals that the ignition delay times of PODE2 are lower than that of n-heptane even at lower equivalence ratio. The KL factor of methanol diffusion flame ranges from 0.02 to 0.04, which is remarkable lower than diesel spray flames. The methanol ATAC achieves higher substitution rate of methanol and the flexible combustion process can be obtained using PODE2 as PI fuel.

Experimental investigation on combustion characteristics and influencing factors of PODE/methanol dual-fuel engine

PODE/methanol dual-fuel combustion mode was conducted on a four-cylinder common-rail engine with PODE direct injection and methanol intake fumigation. This study is aimed to investigate the effects of methanol substitution ratio (MSR), injection timing and inlet temperature on in-cylinder combustion, emission characteristics and fuel economy of dual-fuel engine. Results show that with the increase of MSR, the ignition delay of dual-fuel engine is prolonged, and the COV increases. At medium and small loads, the peak combustion pressure decreases, and the combustion phase is delayed. At high load, the peak values of heat release rate and combustion pressure increase, combustion duration is shortened, and slight knock occurs at 40% MSR. Dual-fuel mode has benefits in reduction of NOx and soot, while increases NO2 and HCHO emissions. With the delay of injection timing, combustion duration is first prolonged and then shortened. The excessive delay of injection timing leads to increased fluctuation of combustion pressure, and partial misfire occurs. With the increase of inlet temperature, the peak values of heat release rate and combustion pressure increase significantly, combustion duration is shortened, and the COV increases. At the inlet temperature of 65 °C, methanol spontaneous combustion occurs near TDC, and thermal efficiency increases to 44.6%.

Effect of injection timing on combustion, performance and emissions characteristics of methanol fuelled DISI engine: A numerical study

In this paper, the effect of the start of injection (SOI) on the engine characteristics of a methanol-fuelled direct injection spark ignition (DISI) engine is numerically studied. The simulations are performed using CONVERGE CFD software on a wall-guided, four-stroke gasoline direct injection (GDI) engine. The SOI is swept from −120° CA ATDC (crank angle after top dead centre) to −100° CA ATDC at a constant step of 5° CA. The engine speed of 2000 rpm and a compression ratio (CR) of 11:1 is used. It is observed that there exists an optimum injection timing for a given spark timing at which the best compromise is obtained between the performance and emissions. A maximum indicated thermal efficiency (ITE) of 41.66% is obtained in the case of −115° CA ATDC SOI. Emissions like formaldehyde and soot are also found to be the lowest in this case. Engine's ITE is 36% higher for methanol fuel than gasoline when simulated by supplying the same energy input, keeping all the other parameters the same. The total hydrocarbon (THC), carbon monoxide (CO), and soot emissions are 58.2%, 68%, and 73.9% lower for optimised methanol injection timing as compared to gasoline. The NOX emissions are found to be higher for methanol than gasoline due to higher in-cylinder temperature in the case of methanol engine, which is due to higher heat release and proper combustion than gasoline.

Evaluating the effect of variable methanol injection timings in a novel co-axial fuel injection system equipped locomotive engine

Methanol has been identified as a potential substitute for conventional fuels (diesel, petrol) from scalability, sustainability, and an economic viewpoint. Economically, methanol could be cheaper than conventional fuels based on the price per MJ energy. This study evaluated the possibility of displacing the diesel (90% on an energy basis) by methanol in the locomotive engine using a novel co-axial injection concept while evaluating the different methanol injection timings. Pilot diesel injection (10% on an energy basis) ensured the combustion of injected methanol. A 1-D model of a 16-cylinder locomotive engine was developed for the parametric study to identify a suitable methanol injection strategy corresponding to co-axial injector configuration. Three different parameters were selected to investigate the effect of the new co-axial injection system on the engine performance, combustion, and emissions. These were (i) methanol injection timing, (ii) nozzle design parameters (hole diameters and the number of holes) for methanol injection, and (iii) nozzle design for diesel injection. Three different methanol injection strategies (ITM1, ITM2, ITM3) were evaluated at eight different notches of the locomotive engine for identical diesel injection timings of the validated base model. ITM1 emerged as the best strategy to inject methanol into the engine cylinder because of relatively higher in-cylinder pressure and comparable heat release rate (HRR). The maximum in-cylinder pressure (Pmax), the crank angle at maximum pressure (°CA Pmax), the start of combustion (SoC) duration, combustion duration (CD), and torque were comparable to the baseline diesel-only fuelling. For this strategy, co-axial injector design parameters [diesel's nozzle diameters (HDD) = 0.2 mm, number of nozzles for diesel (NHD) = 4, methanol nozzle diameters (HDM) = 0.35, number of nozzles for methanol (NHM) = 9)] exhibited promising results. Overall, the first injection strategy emerged as the best for direct methanol injection in the locomotive engine at all engine loads. The main finding of this study was that since methanol had a higher latent heat of vaporization, it should not be injected too late after the diesel pilot injection. This means that methanol must be injected in a sufficiently hot environment to easily vaporize it to ensure its participation in combustion without struggling for evaporation due to the colder in-cylinder environment. The methanol showed relatively lower environmental impact in all three strategies by significantly reducing the NOx emissions. NOx control is a major challenge for the surface transport industry. It could be resolved using methanol, which may expedite its use in internal combustion engines (ICEs), cleaning up the combustion engine based transportation. This simulation study demonstrated that petroleum usage and its negative environmental impact could be reduced by using cleaner/greener methanol.

Numerical simulation and experimental investigation on pollutant emissions characteristics of PODE/methanol dual-fuel combustion

The current study focuses on the effects of methanol ratio, injection timing and intake temperature on emission performance of a common-rail engine with polyoxymethylene dimethyl ethers (PODE)/methanol dual-fuel combustion mode. Then, the numerical model of dual-fuel combustion is established using CFD software CONVERGE coupled with PODE/methanol chemical kinetic mechanism, and the distribution and evolution characteristics of important radicals, methanol and temperature fields inside cylinder are calculated and analyzed. The results show that the NOx and soot emissions of dual-fuel mode decrease by 12.4% and 26.0% compared with pure PODE at 50% load, but CO and HC emissions increase. With the methanol ratio increasing, the NO and N2O emissions decrease, while the methanol, NO2, HCHO, C2H4, CH4 and C2H6 emissions increase, and the peak HO2 mass of dual-fuel increases by 156.2% compared with pure PODE. With the advance of injection timing and the increase of intake temperature, the generation rate of H and OH radicals in dual-fuel combustion raise, the emissions of NO and NO2 increase, while the emissions of methanol, HCHO, C2H4, CH4 and C2H6 decrease. Therefore, compared with traditional diesel engine, more attention should be paid to the unregulated emissions of NO2, methanol and HCHO for PODE/methanol dual-fuel engine.

Numerical study of cold-start performances of a medium compression ratio direct-injection twin-spark plug synchronous ignition engine fueled with methanol

The cold-start mixture preparation, combustion and emissions behaviors of a medium compression ratio direct-injection twin-spark plug synchronous ignition engine fueled with methanol were numerically simulated. Simulation results display that the methanol injection timing, ignition timing and the global equivalence ratio had an important influence on the concentration distribution of methanol-air mixture, the flow velocity, and the density of the flame surface during cold start. Ignition delay period reached the shortest at injection timing 70°CA BTDC. Ignition delay period for injection timing 130°CA BTDC and 50°CA BTDC increased 209% and 45.5% compared to injection timing 70°CA BTDC, respectively. Ignition delay period reached the shortest at ignition timing 21°CA BTDC. Ignition delay period of twin-spark plug was shorter than that of single-spark plug at the same equivalence ratio. There existed the maximum in-cylinder pressure, maximum heat release rate, maximum in-cylinder temperature, lowest unburned methanol and soot emissions, and highest NOX emissions at injection timing 70°CA BTDC. The maximum in-cylinder pressure, maximum heat release rate, and maximum in-cylinder temperature gradually increased with the advance of ignition timing. Injection timing 70°CA BTDC, ignition timing 21°CA BTDC, and equivalence ratio 0.9 could obtain the best cold start performance compromise using twin-spark plug ignition mode. At equivalence ratio 1.0, twin-spark plug ignition had better combustion performances, lower unburned methanol and soot emissions, and higher NOX emissions compared with single-spark plug ignition. Twin-spark plug synchronous ignition had more advantageous to cold starting ignition compared with single-spark plug ignition for a medium compression ratio direct-injection spark-ignition methanol engine.

Parametric study on effects of methanol injection timing and methanol substitution percentage on combustion and emissions of methanol/diesel dual-fuel direct injection engine at full load

The effects of methanol injection timing (MIT) and methanol substitution percentage (MSP) on the combustion and emissions of a methanol/diesel dual-fuel direct injection engine were investigated, followed by a comparative analysis with the conventional methanol/diesel dual-fuel mode. A single-cylinder, air-cooled, naturally aspirated common rail diesel engine was modified into a dual-fuel direct injection engine with a methanol direct injection system. The engine was operated at a maximum torque speed of 2500 rpm and a mean effective pressure of 0.75 MPa. The engine performance was analyzed for different methanol/diesel fuel mixtures using four MSPs: 10%, 20%, 30%, and 40%. Meanwhile, the MIT was adjusted from −60 to −300 °CA after top dead center (ATDC). The results indicated that methanol addition and retarded MIT allowed the diesel injection timing to be properly advanced. A higher MSP increased the ignition delay (CA0-10) and decreased the combustion duration (CA10-90), leading to increases in the brake thermal efficiency (BTE), coefficient of variation of the indicated mean effective pressure (IMEP) (COVIMEP), and knock intensity (KI), along with increases in the total hydrocarbon (THC) and nitrogen oxide (NOX) emissions and decreases in the carbon monoxide (CO) and soot emissions. Additionally, for a specific MSP, the retarded MIT increased the peak cylinder pressure and decreased the maximum heat release rate. Concurrently, it decreased the CA0-10 and increased the CA10-90. Moreover, increases in the BTE, COVIMEP, and KI; decreases in the THC and CO emissions; and increases in the NOX and soot emissions were achieved using the retarded MIT.

Parametric study on effects of excess air/fuel ratio, spark timing, and methanol injection timing on combustion characteristics and performance of natural gas/methanol dual-fuel engine at low loads

A parametric investigation of the effects of excess air/fuel ratio (λ), spark timing (ST), and methanol injection timing (MIT) on the combustion characteristics and performance of a natural gas/methanol dual-fuel engine was conducted. The operation was carried out at 1600 rpm and a low load. λ was varied from 1.2 to 1.6, in increments of 0.1. The ST was kept close to the optimized value of brake thermal efficiency (ηet) and varied from advanced by an 8° crank angle (8 °CA) to retarded by 8 °CA. The results indicated that the flame development period (CA0-10) and the flame propagation period (CA10-90) were prolonged when λ increased from 1.2 to 1.6. The prolonged CA0-10 and CA10-90 could be shortened via the addition of methanol. ηet increased with an increase in λ and the methanol energy substitution ratio (MSR). The ST corresponding to the maximum value of ηet was delayed with an increase in the MSR. When the MIT is changed from −720 to 0 °CA BTDC, two types of air–fuel mixtures can be formed: a stratified-like mixture (when the MIT is set at the timing of intake only) and a homogeneous mixture (when the MIT is set at the timing of the intake valve closing). The most suitable MIT proved to be approximately 60 °CA after the intake valve closed. When the MIT was set at this point, CA0-10 and CA10-90 were shortened, and the coefficient of variation in the indicated mean effective pressure was reduced.

Effects of diesel and methanol injection timing on combustion, performance, and emissions of a diesel engine fueled with directly injected methanol and pilot diesel

A three-dimensional simulation model coupled with detailed chemical kinetics mechanism is applied to investigate a diesel engine fueled with directly injected methanol and pilot diesel. The diesel is injected before top dead center (TDC) to act as a pilot, and then methanol is also directly injected afterwards diesel injection as the main fuel. The effects of diesel and methanol injection timing on the combustion, performance, and emissions are investigated. The results show that: advanced diesel and methanol injections have higher in-cylinder pressure peak; and the in-cylinder pressure peak decreases with the increase of dwell. The ignition delay reduces first and then remains unchanged with the increase of dwell. 50% burn point (CA50) increases in a nearly linear way with the increase of dwell. There are four different combustion phenomena with varied dwell. Too small dwell leads to misfire or roar combustion, and too large dwell is detrimental to fuel economy. Advanced diesel and methanol injections contribute to lower equivalent indicated specific fuel consumption (EISFC) and soot emission, but lead to higher ringing intensity (RI) and nitrogen oxides (NOx) emission.

Detection and analysis of formaldehyde and unburned methanol emissions from a direct-injection spark-ignition methanol engine

A sampling system to collect exhaust emissions of a methanol engine by means of a sampling bag and an absorber was designed to absorb formaldehyde and unburned methanol emissions with deionized pure water. Three novel measurement methods that combine gas chromatography and liquid chromatography (GCLC), gas chromatography and the light spectrum (GCLS), and liquid chromatography and light spectrum (LCLS) were used to separate and measure formaldehyde and unburned methanol emissions. The three measurement methods of GCLC, GCLS and LCLS proved suitable and reliable to separate and measure the formaldehyde and unburned methanol emissions from a direct-injection spark-ignition methanol engine. The effects of methanol injection timing, spark timing, and excess air ratio on formaldehyde and unburned methanol emissions were analyzed experimentally by measurement method of GCLS. The formaldehyde and methanol detection limits are 0.16 μg/mL and 0.18 μg/mL for gas chromatography (GC), respectively, the detection limit for methanol is 0.15 μg/mL for liquid chromatography (LC), and the detection limit for formaldehyde is 0.21 μg/mL for light spectrum (LS). Retarding the spark timing increases the formaldehyde emission and decreases the unburned methanol emissions. The formaldehyde emission decreases rapidly and the unburned methanol emission increases significantly with an increasing excess air ratio.

Optimal factors estimation for diesel/methanol engines changing methanol injection timing and inlet air temperature

Abstract Methanol has been injected at the intake port with heated inlet air in a diesel engine. In the meantime, the Taguchi methodology was adopted to estimate the optimal methanol-energy-share ratio, methanol injection timing, and inlet air temperature. The injection timing and the quantity of methanol were controlled by an ECU (electronic control unit) on an electronic injector. The inlet air temperature was raised by an electric heater. The authors estimate the optimal combination of factors for larger brake thermal efficiency ( η b ), smaller smoke, NOX, HC and CO pollutant emissions for different loads. In addition, net heat release rate is obtained by the measured in-cylinder pressure data. Comparison of between the optimal combination of factors and original conventional diesel engine is made by η b , smoke, NOX, HC, CO and net heat release rate. Carrying out the confirmation tests can show that the predictions of the Taguchi methodology agree with the confirmation tests in the 95% confidence level. For the optimum combinations of factors, the maximum decrease percentage is 41.5% for smoke emission, 61.7% for NOX, 8.6% for HC emission, and 32.4% for CO emission.