Shorter Combustion Duration Research Articles

Heat release analysis and thermal efficiency of a single cylinder diesel dual fuel engine with gasoline port injection

Cleaner diesel engines have been successively developed to meet a compromised solution for issues concerning performance and emission regulation. Combustion and exhaust gas after-treatment technologies are exhaustively settled to resolve those problems. A key improvement of the emissions is diesel dual fuel combustion that increases operating range of the premixed combustion. The main aim of this work is to explore the heat release, fuel consumption, and thermal efficiency of a single cylinder diesel dual fuel engine. An intake port fuel injection of gasoline with the flow rates between 0 and 0.06 g/s was accomplished to form a premixed charge prior to induction into the combustion chamber and ignition by the main diesel fuel. The engine was operated on medium load at 1700 rpm without exhaust gas recirculation. An engine indicating system composed of a cylinder pressure transducer and a shaft encoder was used to investigate combustion characteristics based on the first law of thermodynamics. The combustion of higher gasoline pre-mixer increased heat release rates, shortened combustion duration, and increased maximum cylinder pressure than neat diesel combustion. Increasing gasoline proportion reduced the diesel fuel and total fuel consumptions. This enhanced the engine thermal efficiency over the diesel baseline combustion.

Investigation on the Potential of High Efficiency for Internal Combustion Engines

The current brake thermal efficiency of advanced internal combustion engines is limited to 50%, and how to further improve the efficiency is a challenge. In this study, a theoretical investigation on engine thermal efficiency was carried out using one-dimension simulations based on the first law of thermodynamics. The energy balance was evaluated by varying parameters such as compression ratio (CR); heat transfer coefficient; intake charge properties; and combustion phasing etc.—their influences on the efficiency limits were demonstrated. Results show that for a given heat transfer coefficient, an optimal CR exists to obtain the peak efficiency. The optimal CR decreases with the increase of heat transfer coefficient, and high CR with a low heat-transfer coefficient can achieve a significantly high efficiency. A higher density and specific heat ratio of intake charge, as well as a shorter combustion duration with a proper CA50 (crank angle at 50% of total heat release), can increase efficiency significantly. Methanol shows an excellent ability in decreasing the peak in-cylinder temperature; and the peak indicated efficiency is relatively higher than other tested fuels. The displacement has few effects on the indicated efficiency, while it shows a strong effect on the energy distribution between heat transfer and exhaust energy. All these strategies with high CR result in high in-cylinder pressure and temperature; which means a breakthrough of material is needed in the future.

Impact of fusel oil moisture reduction on the fuel properties and combustion characteristics of SI engine fueled with gasoline-fusel oil blends

Abstract In this study, statistical analysis was used to reveal the significant relation between fuel properties and the reduction of moisture contents at a various fraction of fusel oil in the blend. In addition to this, it is also aimed to conduct a comparative study on the effect of the fuel properties on the combustion characteristics before and after moisture extraction from fusel oil. The moisture content of fusel oil was extracted by employing rotary extractor method, and the fuels were tested in an SI engine under different open throttle valve position (load) and 4500 rpm speed of the engine. As a result, the heating value and carbon content improved significantly after extracting the moisture content from fusel oil by 13% and 7% respectively. According to the statistical analysis of test fuel properties results, the heating value, oxygen, and carbon content have statistically significant effects on the test fuels as the fraction of fusel oil increased especially after moisture extraction. Furthermore, the brake power and BSFC observed to be improved by extracting the moisture content with shorter combustion durations. Almost all fusel oil-gasoline blends have lower COV IMEP at all engine loads compared to pure gasoline.

An investigation of multiple spark discharge using multi-coil ignition system for improving thermal efficiency of lean SI engine operation

Lean spark ignition (SI) engine operation can provide improvement of the thermal efficiency relative to that of stoichiometric SI operation. However, the cycle-to-cycle variations of SI combustion increase with increasing air dilution, and become unacceptable. To gain the benefits of lean operation, the ability to ensure stable, complete and fast combustion is required. As a method to enable stable lean operation, this study investigates the effects of multiple spark discharge on lean SI operation using a multi-coil ignition system that features ten spark coils for a single spark plug.First, the effects of multiple spark discharge on the combustion phasing and the combustion duration are examined for lean operation (excess-air ratio (λ) = 1.67) under a constant spark timing. The results show that both the total discharge duration and the total discharge energy increase with the extension of time interval between spark discharges (Δti) for multiple spark discharge. For the multiple spark discharge of substantially extended Δti, a number of restrikes occur after the spark blowouts due to the weak discharge energy release rate. However, both the total discharge duration and the total discharge energy do not contribute directly to the change of initial combustion phase. Instead, the effective spark discharge energy exists within the total discharge energy, which actually contributes to the change of initial combustion phase. When the effective spark discharge energy is high, it leads to the advancement of the initial combustion phase, resulting in the number of knocking cycles increases with the increase of knocking intensity. Second, additional experiments were conducted under ultra-lean conditions in the λ = 1.82–1.97 range since the effects of multiple spark discharge on SI combustion are much more pronounced for the leaner operation. The results show that the net indicated thermal efficiency increases quite linearly with increasing λ for all multiple spark discharges considered. Especially, for the multiple spark discharge of Δti = 0.2 ms, a proper spark discharge energy is generated from the spark timing to a certain timing after the first start of spark discharge, which advances both the spark timing and the initial combustion phase. A combination of the advanced spark timing and the advanced initial combustion phase leads to the advancement of main combustion phase, and eventually shorten the combustion duration. Because of shortened combustion duration, stable ultra-lean operation at around λ = 1.94 can be achieved with the highest net indicated thermal efficiency of 47.0%.

Emission benefits from the use of n-butanol blends in a Euro 6 diesel engine

Tests with diesel/n-butanol blends (up to 20% by volume) were carried out in a Euro 6 engine following the New European Driving Cycle in a test bench. No decrease in engine efficiency was observed when n-butanol is used and fuel consumption increased proportionally to its lower heating value. Regarding emissions, total hydrocarbon and carbon monoxide increased when n-butanol is used. On the other hand, the use of n-butanol reduces the particle emissions down to a minimum value (for around 16% of n-butanol content) and then increases particle emissions again. This was observed in both mass and particle number. This trend occurs as a consequence of the compromise between the increase in oxygen content, which inhibits soot formation, and the increase in hydrocarbon emissions, especially under cold-engine conditions, which promotes liquid nucleation. Finally, NOX emissions remained unchanged as a consequence of the compensation between larger ignition delays and shorter combustion durations.

Combustion and emission characteristics of diesel engine fueled with biodiesel/PODE blends

Polyoxymethylene Dimethyl Ethers (PODE), with excellent volatility and oxygen content of up to 49%, have great potential to improve engine performance and emission characteristics, especially for soot reduction. In this study, experiments were carried out in a single-cylinder engine fueled with diesel, biodiesel and BP15 (15% PODE and 85% biodiesel by volume). The effects of CA50 and EGR rates on the combustion and emission characteristics have been carefully examined. As CA50 was retarded, diesel always had the shortest ignition delay and longest combustion duration, while BP15 had similar ignition delay, but shorter combustion duration in contrast to biodiesel. As EGR rate varied from 20% to 40%, diesel still presented the shortest ignition delay and longest combustion duration, while BP15 had shorter ignition delay and combustion duration than biodiesel. Regarding to the emissions, BP15 showed the lowest soot emissions and can break the trade-off between NOx and soot emissions. Notably, emissions of NOx and soot can reach 0.05g/kWh and 0.0009g/kWh, respectively. In addition, BP15 had the highest thermal efficiency over the test conditions.

The effect of pentanol addition on the particulate emission characteristics of a biodiesel operated diesel engine

In the present study, combustion performance and the physical and chemical characteristics of soot particles from a DI diesel engine were studied. The engine was fueled with n-pentanol mixed with biodiesel at 15% and 30% by volume and operated at 1800rpm under three engine loads (20%, 50% and 80% load). In comparison with pure biodiesel, the pentanol-biodiesel blends lead to delayed start of combustion and shortened combustion duration. The particle number concentrations of all size groups are reduced for biodiesel-pentanol blends in all the tested conditions, due to longer ignition delay time, lower viscosity and boiling point, and higher oxygen content of pentanol. The brake specific elemental carbon (EC) emissions of biodiesel were found to be lower compared to diesel and after adding pentanol in biodiesel, the EC emissions further decrease. While for organic carbon (OC) emissions, biodiesel and diesel are at similar level under the tested engine loads, and the blends show a higher fraction of OC at low and medium engine loads. The blended fuel with higher proportion of pentanol gives lower total particle-phase PAHs emissions and also a lower benzo[a]pyrene equivalent (BaPeq) compared to pure biodiesel under the tested engine loads.

Performance and combustion characteristics of a novel crank-rocker engine

The performance and combustion characteristics of a novel internal combustion engine, called the crank-rocker, have been investigated experimentally. The engine specifications are gasoline-port injection, four-stroke, spark-ignition, and single-curved cylinder. The ignition timing was initially set at 8.60 CA BTDC, 1800 rpm based on a small conventional engine. The equivalence ratio, lambda (λ) was varied at rich, stoichiometric, and lean conditions. The entire tests were performed at six different engine speeds of 1800, 2000, 2200, 2400, 2600 and 2800 rpm, with each one operating at wide open throttle. The performance data such as indicated torque, indicated power, indicated specific fuel consumption, and indicated thermal efficiency were calculated. The combustion characteristics such as cylinder pressure, mass fraction burned, heat release rate, P-V diagram, and indicated mean effective pressure were also determined. The results obtained from the crank-rocker engine were compared with the experimental results obtained from the conventional engine (benchmark engine). The results showed that the indicated torque, power and thermal efficiency of crank-rocker engine is higher than normal slidercrank engine. The indicated torque and power increased by about 6.28 %, while the indicated specific fuel consumption is lower by 4.69 %. In general, the engine has similar indicated performance characteristics to the conventional engine, but the combustion characteristics differ because the peak values of the combustion pressure and heat release occur at higher crank angle ATDC. This was found to be due to the dwelling of piston at TDC. The combustion rate and mixture of the novel crank-rocker engine burned faster, resulting in shorter combustion duration and ignition delay period than the conventional slider-crank engine.

An experimental investigation on thermal efficiency of a compression ignition engine fueled with five gasoline-like fuels

Partially Premixed Compression Ignition (PPCI) and Multiple Premixed Compression Ignition (MPCI) are two high efficiency and clean combustion strategies. This paper presents an experimental investigation on the efficiency of PPCI and MPCI combustion using five gasoline-like fuels: gasoline, gasoline/ethylhexyl-nitrate (EHN) blends, gasoline/diesel blends, gasoline/polyoxymethylene dimethyl ethers (PODEn) blends, gasoline/diesel/PODEn blends, denoted as G, GE, GD, GP, GDP, respectively. The study was conducted using a single cylinder engine that was retrofitted from a production Euro IV diesel engine. The results showed that in PPCI mode, the order of thermal efficiency from the highest to the lowest was GP, G, GDP, GE, and GD, while the order in MPCI mode was GP, GDP, GE, G, and GD. The thermal efficiency of MPCI mode was higher than that of PPCI mode, except for GP, whose thermal efficiency was the highest of about 48.8% for both modes due to the early CA50 and short combustion duration. In PPCI mode, NOx and soot emissions were below 0.4g/kWh and 0.01g/kWh, respectively, satisfying the Euro VI emission standard. NOx emission in MPCI mode can meet the requirement of Euro VI. However, the soot emission exceeded the limit because the second stage combustion was partially diffusion combustion, implying an extra Gasoline Particle Filter (GPF) was needed to meet the Euro VI standard. This study indicates that PPCI injection strategy alone and MPCI injection strategy with GPF are two potential ways of retrofitting a Euro IV engine to meet the Euro VI emission standard. GPF increases manufacturing cost, but higher thermal efficiency in MPCI mode could reduce the total cost of ownership due to the lower fuel consumption.

On the effect of injection timing on the ignition of lean PRF/air/EGR mixtures under direct dual fuel stratification conditions

The ignition characteristics of lean primary reference fuel (PRF)/air/exhaust gas recirculation (EGR) mixture under reactivity-controlled compression ignition (RCCI) and direct duel fuel stratification (DDFS) conditions are investigated by 2-D direct numerical simulations (DNSs) with a 116-species reduced chemistry of the PRF oxidation. The 2-D DNSs of the DDFS combustion are performed by varying the injection timing of iso-octane (i-C8H18) with a pseudo-iso-octane (PC8H18) model together with a novel compression heating model to account for the compression heating and expansion cooling effects of the piston motion in an engine cylinder. The PC8H18 model is newly developed to mimic the timing, duration, and cooling effects of the direct injection of i-C8H18 onto a premixed background charge of PRF/air/EGR mixture with composition inhomogeneities. It is found that the RCCI combustion exhibits a very high peak heat release rate (HRR) with a short combustion duration due to the predominance of the spontaneous ignition mode of combustion. However, the DDFS combustion has much lower peak HRR and longer combustion duration regardless of the fuel injection timing compared to those of the RCCI combustion, which is primarily attributed to the sequential injection of i-C8H18. It is also found that the ignition delay of the DDFS combustion features a non-monotonic behavior with increasing fuel-injection timing due to the different effect of fuel evaporation on the low-, intermediate-, and high-temperature chemistry of the PRF oxidation. The budget and Damköhler number analyses verify that although a mixed combustion mode of deflagration and spontaneous ignition exists during the early phase of the DDFS combustion, the spontaneous ignition becomes predominant during the main combustion, and hence, the spread-out of heat release rate in the DDFS combustion is mainly governed by the direct injection process of i-C8H18. Finally, a misfire is observed for the DDFS combustion when the direct injection of i-C8H18 occurs during the intermediate-temperature chemistry (ITC) regime between the first- and second-stage ignition. This is because the temperature drop induced by the direct injection of i-C8H18 impedes the main ITC reactions, and hence, the main combustion fails to occur.

Production, analysis and combustion characterization of biomass fast pyrolysis oil – Biodiesel blends for use in diesel engines

In this study, blends of biodiesel and softwood derived fast pyrolysis oil (FPO) were produced, characterized, and evaluated for thermodynamic and emission performance in a single cylinder research engine. FPO was supplied from an in-house fluidized bed reactor as well as a commercial source. Separate FPO-biodiesel blends from both FPO sources were prepared using initial volumetric ratios of 80:20 and 60:40 (biodiesel:FPO, by volume). After blending, mixing, and a 24h settling period, two layers formed and the top, biodiesel-rich layers containing about 5 and 10vol% FPO were decanted and characterized on the basis of a thermogravimetric analysis, viscosity, acid number, water content, elemental analysis, and heating value. Significant decreases in viscosity, acidity, and water content from the original FPO validated blending as means of extracting compounds suitable for use as fuels from pyrolytic liquids in biodiesel. A single cylinder, common rail, direct injection diesel engine was used to analyze the combustion performance of the FPO fuel blends against neat diesel and biodiesel. Fuel performance was characterized on the basis of a thermodynamic combustion analysis, as well as corresponding exhaust emission measurements for CO2, CO, unburned hydrocarbons, particulate matter, and NOx.Engine testing revealed similar indicated efficiencies for biodiesel and diesel at all considered engine operating modes, while blend fuels showed indicated efficiencies between 75 and 95% of diesel values. In general, FPO fuels exhibited increased ignition delays and shorter combustion durations with greater FPO blend concentrations, though this could be partially compensated for using a pilot injection strategy. The longer ignition delays of the blend fuels resulted in overly lean regions of the cylinder, which produced largely premixed combustion events contributing to brake specific CO and uHC emissions up to 1.5 and 3.5 greater than diesel, respectively. Specific PM emissions were 41–62% lower for blend fuels than diesel. Both blends of in-house FPO showed similar PM emission performance, however at higher concentration than low blend commercial fuel.

Combustion and emission characteristics of diesel engine fueled with diesel-like fuel from waste lubrication oil

Waste lubricant oil (WLO) is one of the most important types of the energy sources. WLO cannot be burned directly in diesel engines, but can be processed to be used as diesel-like fuel (DLF) to minimize its harmful effect and maximize its useful values. Moreover, there are some differences in physicochemical properties between WLO and diesel fuel. In order to identify the differences in combustion and emission performance of diesel engine fueled with the two fuels, a bench test of a single-cylinder direct injection diesel engine without any engine modification was investigated at four engine speeds and five engine loads. The effects of the fuels on fuel economic performance, combustion characteristics, and emissions of hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx) and smoke were discussed. The DLF exhibits longer ignition delay period and shorter combustion duration than diesel fuel. The test results indicate that the higher distillation temperatures of the DLF attribute to the increase of combustion pressure, temperature and heat release rate. The brake specific fuel consumption (BSFC) of the DLF compared to diesel is reduced by about 3% at 3000rpm under light and medium loads. The DLF produces slightly higher NOx emissions at middle and heavy loads, somewhat more smoke emissions at middle loads, and notably higher HC and CO emissions at most measured points than diesel fuel. It is concluded that the DLF can be used as potential available fuel in high-speed diesel engines without any problems.

An Experimental Study on Combustion and Emission Analysis of Four Cylinder 4-Stroke Gasoline Engine Using Pure Hydrogen and LPG at Idle Condition

Abstract Fluctuation in oil prices and stricter exhaust emission norms were the main reasons wakening every researcher to search for suitable and feasible alternative fuels for automotive use. Among the available option gaseous fuels find their best position because of their compatible physical-chemical properties and ecofriendly nature than present fossil fuels. Hydrogen's combustion properties like high energy content, high heating value, wide range of flammability and low ignition energy with almost least toxic emissions are favorable to use in an IC engine as an alternative fuel. Liquid petroleum gas (LPG) has lower carbon content, higher calorific value, octane number and flame propagation speed will improve the emission results compared to gasoline fuel. This paper describes an experimental results carried out to evaluate the combustion and emission performance of a Maruti Suzuki make, spark ignited four cylinders, four stroke engines at idle condition by using pure hydrogen, LPG and gasoline. The engine was adjoined with Electronic Control Unit (ECU) assisting hydrogen and LPG injector system keeping gasoline line unchanged. Tests were carried out by using compressed hydrogen gas regulated by two stage pressure reduction from cylinder to atmospheric value and by using vaporizer pressure for LPG. For comparison engine was run first by gasoline and then by pure hydrogen and LPG. Study revealed that there was increment of 13% cylinder pressure for pure hydrogen and decrement of 4.5% cylinder pressure for LPG when compared to gasoline. The burn duration for pure hydrogen, LPG and gasoline were found to be increasing respectively which infers that hydrogen has very short combustion duration and gasoline higher. It was observed that toxic emissions like Carbon monoxide (CO), Hydrocarbons (HC) and Oxides of Nitrogen (NO x ) were improved for pure hydrogen than LPG and gasoline.

Effect of the addition of ethanol on the combustion and emission characteristics of a common-rail dimethyl ether engine

The effect of the addition of ethanol on the combustion and emission characteristics of dimethyl ether combustion were investigated in this study using an electronically controlled common-rail dimethyl ether engine. The ignition delay, the crank angle for 50% mass fraction burned, the combustion duration, the nitrogen oxide emissions, the hydrocarbon emissions and the carbon monoxide emissions of the fuel blends with the addition of different percentages of ethanol were analysed for different loads and for different injection timings separately. The results suggest that the effect of ethanol on the dimethyl ether combustion mainly prolongs the ignition delay and inhibits the combustion rate. The ignition delay is prolonged significantly with increasing percentage of ethanol added for low loads or retarded injection timings. A reduction in the combustion rate and an increase in the combustion duration are associated with a higher percentage of ethanol added for high loads or advanced injection timings, leading to lower nitrogen oxide emissions. On the addition of 15% ethanol, the nitrogen oxide emissions are reduced by about 17% for a brake mean effective pressure of 1.2 MPa, and by 32% when the start of injection is at −7° crank angle after top dead centre. Premixed combustion with a sharply prolonged ignition delay and a shortened combustion duration can be achieved by the addition of 15% ethanol when the start of injection is at 5° crank angle after top dead centre. The carbon monoxide emissions show a tendency to increase with increasing amount of ethanol added, whereas the hydrocarbon emissions remain nearly the same until the percentage of ethanol reaches 15%.

Identification of ringing operation for low temperature combustion engines

High-efficiency and low-emission low temperature combustion modes including homogeneous charge compression ignition (HCCI) are limited at high load conditions due to rapid pressure rise rate, short combustion duration and ringing operation. This study uses two different HCCI engines to investigate combustion-generated ringing at a number of HCCI engine operating points between misfire and ringing zones for ethanol and n-heptane fuels. Ringing intensity (RI) is investigated along with main HCCI combustion parameters and engine-out emissions. The results show the RI generally increases by advancing crank angle of 50% fuel burnt (CA50) and also decreasing burn duration (BD). It is found that adjusting CA50 can provide a control knob for the RI since all the extreme noisy data points have CA50<9 CAD aTDC. In-cylinder pressure at 5, 10, 15 CAD aTDC (P5,P10 and P15) and maximum in-cylinder pressure (Pmax) show strong correlation with RI. To this end, P5,P10 and P15 and Pmax are used to develop an artificial neural network (ANN) model to predict RI. Experimental data at 155 steady-state points are used to evaluate the ANN model for two totally different HCCI engines running with high and low octane fuels. The validation results indicate that the ANN model can predict RI with less than 4.2% error. The ANN model can be used to identify HCCI ringing operation for combustion control applications.

Towards a comprehensive understanding of the influence of fuel properties on the combustion characteristics of a RCCI (reactivity controlled compression ignition) engine

The influence of fuel chemical properties on combustion characteristics of a RCCI (reactivity controlled compression ignition) engine was investigated using multi-dimensional simulations. The operating ranges of combustion phasing (CA50) for gasoline/diesel and methanol/diesel RCCI combustion were determined with respect to limited boundaries of fuel efficiency, RI (ringing intensity), and NOx (nitrogen oxide) emissions. The results indicated that a more retarded CA50 was necessary for methanol/diesel RCCI to avoid excessive RI due to its fast combustion rate. Because of the shortened combustion duration, reduced incomplete combustion, and lower heat transfer losses, improved fuel efficiency was achieved by methanol/diesel RCCI than gasoline/diesel RCCI. The trade-off relationship between RI and EISFC (equivalent indicated specific fuel consumption) could be defeated by increasing premixed fuel ratio (methanol or gasoline). For methanol/diesel RCCI, the more retarded CA50 was the primary reason for the higher sensitivity of CA50 to the variation of in–cylinder initial temperature (TIVC), which consequently could lead to higher cyclic variations. In addition, the weakened low temperature heat release of methanol/diesel also deteriorated the stability of CA50 with the variation of TIVC. Overall, with optimized premixed fuel ratio, RCCI combustion demonstrated more advantages in EISFC, RI, controllability, and stable operation over HCCI (homogeneous charge compression ignition) combustion for a wide load range.

Combustion performance and emissions of 2-methylfuran diesel blends in a diesel engine

As an important renewable engine fuel, 2-methylfuran (MF) has drawn intense attention due to the breakthroughs in its production methods. In the present study, combustion characteristics and emissions of a four cylinder direct-injection compression-ignition (DICI) engine fueled with diesel–MF blends (DM) and pure diesel are investigated. The tests were performed at constant speed of 1800rpm and varying loads from 0.13 to 1.13MPa brake mean effective pressure (BMEP). Results show that diesel–MF blends have different combustion performance from pure diesel. The combustion phase of fuel blends is retarded with the increase of MF fraction. Diesel–MF blends are characterized with longer ignition delay and shorter combustion duration. Meanwhile, diesel–MF blends show higher brake thermal efficiency (BTE) than pure diesel. However, diesel–MF blends lead to higher NOx emissions than pure diesel and the NOx emissions are increased with the increase of MF fraction. The soot emissions from diesel–MF blends are significantly reduced compared to pure diesel. The CO and HC emissions from tested fuels are nearly the same at medium and high engine loads. Pure diesel produces lower CO emissions and higher HC emissions than that of diesel–MF blends at low loads of 0.13–0.38MPa BMEP.

EFFECTS OF AIR INTAKE TEMPERATURE ON THE FUEL CONSUMPTION AND EXHAUST EMISSIONS OF NATURAL ASPIRATED GASOLINE ENGINE

Improving fuel consumption with lower exhaust emissions give more focused to all car manufactures. A higher engine performance with lower exhaust emissions requires a complete mixing process resulted in ultra-lean high combustion efficiency. Air intake temperature is one of the alternative strategies to improve fuel consumption and reduced exhaust emissions. This is due to the cold air is denser and contain higher oxygen availability. Air intake temperature will affect to the oxygen concentration in the charged air that influence the combustion process through ignition delay and fuel burning rate. The objective of this experiment is to investigate the effects of air intake temperature to the fuel consumption and exhaust emission at variation of engine speeds and constant load by using 1.6L gasoline engine. Air intake temperature was changed from 20 °C to 30 °C. The DaTAQ Pro V2 software was used to measure the engine fuel consumption while gas analyzer (MRU Gas Analyzer) was used to measure the exhaust emission such as Unburned hydrocarbons (UHCs) and carbon monoxide (CO). The results showed that fuel consumption, UHCs and CO emissions increased with the increase of air intake temperature. The increase of air intake temperature resulted in advanced and shorter combustion duration. Higher oxygen concentration at lower air intake temperature leads to the complete mixing process and complete combustion. Therefore, the experimental results can be concluded that the lower air intake temperature resulted in improved fuel consumption and reduced UHCs and CO emissions.

Comparative study on the explosion characteristics of pentanol isomer–air mixtures

A comparative study was experimentally performed on the explosion characteristics of four pentanol isomer–air mixtures (n-pentanol, 3-methyl-1-butanol, 2-methyl-1-butanol, 2-methyl-2-butanol), at various initial temperatures and initial pressures. The explosion parameters of explosion pressure, maximum rate of pressure rise, combustion duration and combustion development period were measured. The influence of initial conditions on the explosion characteristics were discussed. Results show that the peak explosion pressure is linear function of the reciprocal of initial temperature, but the maximum rate of pressure rise is insensitive to the temperature variation. With the initial pressure elevated from 0.1 to 0.25MPa, the peak explosion pressure increases significantly, but the increase rate is decelerated when the pressure is further increased. Among the four pentanol isomer–air mixtures, in the order of n-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol and 2-methyl-2-butanol, the peak explosion pressure and maximum rate of pressure rise decrease while the combustion duration and flame development period increase, reflecting the decreasing flame speed. Difference among the isomers tends to be decreased for the peak explosion pressure while increased for the maximum rate of pressure rise with the increase of initial pressure. Pressure oscillation occurs at the rich mixture and high pressure, resulting in short combustion duration, but influencing the flame development period little.

Effect of hydrogen addition on the performance and emission parameters of an SI engine fueled with butanol blends at stoichiometric conditions

Hydrogen is considered as the best fuel due to its excellent combustion properties. But its use as a fuel is confined by its low energy density. In the present investigation an attempt has been made to utilize some of the benefits of hydrogen by using it as an additive in a butanol fueled engine. The experimental study has been carried out on a 4 stroke, single cylinder, manifold electronic fuel injected (EFI) engine mapped to run at stoichiometric conditions. Butanol blends were chosen as the base fuel due to their higher energy density compared to ethanol. A small fraction of hydrogen was injected into the air stream. The engine was run at 3000 RPM at full load condition. The performance, emission and combustion parameters are compared for four concentrations of butanol (10%, 20%, 30%, and 100% by volume of fuel) and two concentrations of hydrogen (5%, and 10% by volume of air) with gasoline. The results indicated that the efficiency of the engine improved upon hydrogen enrichment. An average of 60% reduction was observed in HC and CO emissions with 10% enrichment of hydrogen, whereas the NO emissions almost doubled itself. The combustion analysis showed reduced delay periods, shorter combustion durations, higher cylinder pressures, higher temperatures and improved combustion.