Retarded Injection Timing Research Articles

Screening oxygenates for favorable NOx/smoke trade-off in a DI diesel engine using multi response optimization

This study proposes the use of Grey-Taguchi based multi-response optimization to screen suitable diesel-oxygenate blends for achieving simultaneous reduction of smoke and NOx emissions with maximum performance in a DI diesel engine with minimum number of trials. The effects of factors such as oxygenate type, its blend proportion with diesel and retarded injection timing on emission and performance variables were considered. Three popular oxygenates viz., Diethyl ether (DEE), Dimethyl carbonate (DMC) and Diglyme (DGM) were screened. Response surface models (RSM) were developed using experimental data. Taguchi’s signal-to-noise ratio approach was applied to predict optimal factor settings for all individual responses. RSM and predicted optimum factor levels were later validated by rigorous experimentation. It was found that DEE blends delivered best performance. Lowest smoke opacity was realized with DMC blends. NOx emissions were least for DEE blends. Higher DMC and DGM blends generated low HC emissions while lower DGM blends gave out low HC emissions at lower retarded injection timing. CO emissions were generally low for higher DMC blends. Smoke and NOx reducing capabilities of DGM are in between DEE and DMC. Finally it was experimentally validated that, Grey-Taguchi predicted combination of 10% DGM blend injected at 21°CA, simultaneously reduced smoke opacity(▾29.17%) and NOx emissions(▾17.4%) with best performance(▴7%) when compared to baseline diesel operation. The results indicated that Grey-Taguchi method can be effectively used to screen oxygenates suitable to achieve the set objective with minimum number of trials saving cost and time.

Modification of piston bowl geometry and injection strategy, and investigation of EGR composition for a DME-burning direct injection engine

The amount of pollutant gases in the atmosphere has reached a critical state due to an increase in industrial development and the rapid growth of automobile industries that use fossil fuels. The combustion of fossil fuels produces harmful gases such as carbon dioxide, nitrogen monoxide (NO), soot, particulate matter (PM), etc. The use of Dimethyl Ether (DME) biofuel in diesel engines or other combustion processes have been highly regarded by researchers. Studies show that the use of pure DME in automotive engines will be possible in the near future. The present work evaluated the environmental and performance effects of changing the injection strategy (time and temperature), piston bowl geometry, and exhaust gas recirculation (EGR) composition for a DME-burning engine. The modification of piston bowl parameters and engine simulation were numerically performed by using AVL fire CFD code. For model validation, the calculated mean pressure and rate of heat released (RHR) were compared to the experimental data and the results showed a good agreement (under a 70% load and 1200-rpm engine speed). It was found that retarding injection timing (reduction in in-cylinder temperature, consequently) caused a reduction in NO emissions and increased soot formation, reciprocally; this occurred because of a reduction in temperature and a lower soot oxidation in the combustion chamber. It became clear that 3 deg before top dead center (BTDC) was the appropriate injection timing for the DME-burning heavy duty diesel engine running under 1200 rpm. Also, the parametrical modification of the piston bowl geometry and the simultaneous decrease of Tm (piston bowl depth) and R3 (bowl inner radius) lengths were associated with lower exhaust NO emissions. For the perfect utilization of DME fuel in an HD diesel engine, the suggested proper lengths of Tm and R3 were 0.008 and 0.0079 m, respectively. Furthermore, various EGR compositions for the reduction of exhaust NO were investigated. The simulation results showed that a 0.2 EGR composition led to a reduction in the exhaust NO by 37%.

The effect of injection timing on the performance and emission of direct injection CI engine running on diethyl ether-diesel blends

In diesel engine, fuel injection timing is a major parameter that affects combustion, performance and emission characteristics. Variation in injection timing has a strong effect on BTE, BSFC, BSEC, smoke and NOx emissions because of the change in maximum pressure and temperature in engine cylinder. In this experimental investigation, the optimum performance DEE-diesel blend ratio DE15D (15% DEE and 85% diesel by volume) was tested for variable injection timings to evaluate its effect and determine the optimum fuel injection timing, as the addition of DEE to diesel fuel causes retardation in dynamic injection timing. The engine tests were carried out at 10%, 25%, 50%, 75% and 100% of full load with 3º and 6º advancement, base and 3º and 7º retarded injection timings. The test results show that BSFC and BSEC provide the best result for the base injection timing at full load condition. The 6º advancement in injection timing at full load condition reduced smoke by 12.5% and HC by 15.38%. The retarded injection timing by 7º at full load showed improvement in BTE by 7.96% and in NOx by 3.66%.

Artificial neural network applied forecast on a parametric study of Calophyllum inophyllum methyl ester-diesel engine out responses

This experimental work presents a parametric investigation of Calophyllum inophyllum methyl ester (CIME)-diesel engine operations and artificial neural network (ANN) applied forecast of the engine out responses. The engine tests were performed for five test fuels from idle to full load conditions with the stipulated increment of 25% of the load for every run at three selected injection timings (21°, 23° and 25° CA bTDC) for 220bar, 260bar and 300bar injection pressures. The experimental outcomes indicated that twenty percentage blend of the biodiesel in neat diesel (CIME20) showed the highest brake thermal efficiency (BTE) among the CIME-diesel operations for 300bar injection pressure at 23° CA bTDC injection timing whereas BTE for the test fuels reduced at advanced and retarded injection timings at full load. CO, UBHC, dry soot and engine out O2 emissions were reduced at the advanced injection timing whereas NO and CO2 emissions increased. Using steady state experimental data, separate ANN models were proposed to forecast performance (BTE, BSEC, EGT) and emission (CO, CO2, UBHC, NO, dry soot and engine out O2) parameters with percentage load, blend percentage, injection pressure and injection timing as selected input control variables. The proposed ANN models indicated an impressive agreement as correlation coefficient (R) and mean absolute percentage error (MAPE) values perceived in the range of 0.99879–0.99993 and 0.87–4.62% respectively with remarkably lower root mean squared errors. Besides, lower values of mean squared relative error (MSRE) and noteworthy Nash-Sutcliffe coefficient of Efficiency (NSE) indices reasonably demonstrated robustness of the proposed models. Moreover, observed values of forecasting uncertainty Theil U2 indicated more effective outcomes for a credible model forecasting ability.

Experimental study of the effect of engine parameters on ultrafine particle in diesel/methanol dual fuel engine

Experimental study was conducted on a compression ignition engine to investigate into the effects of methanol substitution percent (MSP), injection timing, intake air temperature (Ti), exhaust gas recirculation (EGR) and other parameters on the ultrafine particle emitted from the engine. The testing engine was run on the mode of Diesel/methanol dual fuel, which was modified from a turbocharged, inter-cooling diesel engine. The testing results showed that tailpipe length had a significant effect on the nucleation mode particles but limited effect on accumulation mode particles. The effect of MSP on ultrafine particle was distinctly dependent on injection timing. Under retarded injection timing condition, total particle number gradually reduced with the increment of MSP. But it changed little or even increased under early injection timing condition. In addition, the injection timing and Ti had combined effects on ultrafine particle. Under high Ti condition, accumulation mode particles number significantly increased with delaying injection timing, while it increased slightly under low Ti condition. Nucleation mode of particles exhibited opposite trend. And at any rate of given EGR addition, soot and PN remained low in DMDF mode with high MSP and the soot/PN-bump phenomenon will be weakened as methanol increases.

The influence of injection strategy on mixture formation and combustion process in a direct injection natural gas rotary engine

The application of direct injection (DI) technology is considered as an effective way to improve the performance of the rotary engine. This work seeks to numerically dissect the influence of injection strategy on mixture formation and combustion process in a DI natural gas rotary engine. A 3D dynamic simulation model established in our previous work was used to acquire some critical information which was difficult to obtain through experimental investigations. These were the flow field, the fuel distribution, the temperature field and some intermediate concentration fields in the combustion chamber. Simulation results showed that for mixture formation, the motion mechanism of the fuel varies with the injection position. The mass of fuel located at the back of the combustion chamber for injection nozzles A, B and C, was determined by the intensity of vortex I, the coupling function between the value of the impact angle and the intensity of vortex I, and the value of the impact angle respectively. In addition, with retarded injection timing, the accumulation area of fuel for all injection nozzle positions moved from the back to the front of the combustion chamber at ignition timing. For combustion process, the overall combustion rate for the injection strategy (case A4) whose nozzle was 50mm apart along the engine major axis and whose injection timing was 360°CA (BTDC), was the fastest. Compared with the out-cylinder premixed gas-filling method (case premix method), the improved combustion rate of case A4 had a 29.7% increase in peak pressure, but also a certain increase in NO emissions.

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%.

Numerical investigation of the effect of injection strategy on mixture formation and combustion process in a port injection natural gas rotary engine

This work aimed to numerically study the influence of injection strategy on mixture formation and combustion process in a port injection natural gas rotary engine. On the base of a 3D dynamic simulation model which was established in our previous work, some critical information was obtained, which was difficult to obtain through experiment, in terms of the flow field, the fuel distribution, the temperature field and the concentration fields of some intermediates. Simulation results showed that for mixture formation, the movements of fuel in injection stage were mainly controlled by the intensity of the vortex I for injection timing, and the value of jet flux for injection duration respectively. With retarded injection timing, the decreasing intensity of the vortex I resulted in less fuel moving toward the back of the combustion chamber. With the extension in injection duration, the decreasing value of jet flux resulted in more fuel staying at the back of the combustion chamber. For combustion process, the overall combustion rate for injection strategy which had an injection timing of 390°CA (BTDC) and injection duration of 51.5°CA (case ID4) was the fastest. This was mainly due to the fact that the accumulation area of fuel was at the middle and front of the combustion chamber. Meanwhile, fuel concentration near the leading and trailing spark plugs was conducive for the flame kernel formation. Compared with the injection strategy which had an injection timing of 450°CA (BTDC) and an injection duration of 55°CA (case IT1), the improved combustion rate of case ID4 had a 23% increase in the peak pressure, but also a certain increase in NO emissions.

Energy Balance Analysis to Assess Efficiency Improvements with Low Heat Rejection Concepts Applied to Low Temperature Combustion

ABSTRACTSimultaneously decreasing diesel engine emissions while increasing engine efficiency can be a challenge. The results of recent computational and experimental studies, however, have indicated that emissions can be decreased while simultaneously increasing efficiency through the application of low heat rejection (LHR) techniques to low temperature combustion (LTC). One such recent experimental study showed simultaneous decreases in nitrogen oxides and smoke from a light-duty, multi-cylinder diesel engine and serves as motivation to the present study. The major conclusion from that study is that combining LHR with LTC substantially increases LTC brake fuel conversion efficiency through increases in both combustion efficiency (i.e., decreased hydrocarbon and carbon monoxide emissions) and brake thermal efficiency. LTC is realized through high levels of exhaust gas recirculation and retarded injection timings while different degrees of LHR are achieved by means of higher coolant temperatures, which should serve to decrease the temperature gradients across the cylinder walls. It is clear that the increase in brake thermal efficiency is the significant contributor to the increase in brake fuel conversion efficiency; it is not clear, however, what necessarily drove the increase in brake thermal efficiency. Seeking clarity to this issue is the motivation of the current study. This study explores in more detail the increase in brake thermal efficiency in an attempt to understand what influence LHR has on LTC efficiency improvements. This study is satisfied through analysis of the quantification of various efficiencies (i.e., net indicated thermal, net indicated fuel conversion, and brake fuel conversion efficiencies) and the many energy transfer terms (i.e., energy balance analysis). The energy balance analysis specifically reveals insight in how energy transferred through the coolant compares to those changes observed with power and exhaust energy. Specifically, the energy balance confirms important insights offered by the efficiency analysis as related to the operation of LTC at high engine coolant temperature compared to low coolant temperature. It is concluded that the chief reason for efficiency improvement with LTC at high engine coolant temperature (i.e., the LHR condition), compared to low engine coolant temperature, is improved combustion phasing; combustion efficiency is also improved. The results suggest that LTC efficiency improvements can be realized with higher operating engine coolant temperatures under light-load engine conditions.

EXPERIMENTAL INVESTIGATION ON PERFORMANCE OF SINGLE CYLINDER FOUR STROKE SPARK IGNITION ENGINE WITH MODIFICATION OF PISTON CROWN

A decent swirl advances the quick burning and enhances the efficiency for engine which is preferably running at low speeds in order to have low mechanical losses and empowering good combustion efficiency. Subsequently to create high turbulence preceding burning inside the cylinder, swirl prompted by the bay channel inside the cylinder head will be useful. The automobile vehicles still satisfying demands for high performance, requires immense efforts to create new engine ideas and deliver less emission. Swirl is used in SI engine to speed up the combustion process in four stroke engines It increases turbulence and accelerates chemical action by intimating mixing of fuel and oxygen there by weak mixtures can be burnt effectively. In Petrol engine, swirl can increase the rate of fuel-air mixing, reducing the combustion duration for re-entrant chambers at retarded injection timings. Swirl interaction with compression induced squish flow increases turbulence levels in the combustion bowl, promoting mixing. In order to achieve the swirl the piston crown of the conventional petrol engine was suitably modified by forming different shaped grooves on it. This facilitates increased intensity of the swirl for proper mixing of air fuel and to examine their effects on the performance of this engine fuelled with petrol and its blends with ethanol. In the present work Experiment was carried out with unmodified and modified piston with different shapes without much changing compression ratio comparative results shows that better combustion in gasoline engine was obtained with single groove hemispherical piston. Brake thermal efficiency increased by 1.39% and Brake specific fuel consumption reduced by 3% for E10P90 blend compared to unmodified piston

Leaner Lifted-Flame Combustion Enabled by the Use of an Oxygenated Fuel in an Optical CI Engine

Leaner lifted-flame combustion (LLFC) is a mixing-controlled combustion strategy for compression-ignition engines that does not produce soot because the equivalence ratio at the lift-off length, Φ(H), is less than or equal to approximately two. In addition to preventing soot formation, LLFC can simultaneously control emissions of nitrogen oxides because it is tolerant to the use of exhaust-gas recirculation for lowering in-cylinder temperatures. LLFC can be achieved through the use of oxygenated fuels and enhanced fuel/charge-gas mixing upstream of the lift-off length. Enhanced mixing can be obtained via higher injection pressures, smaller injector orifice diameters, lower intake-manifold and coolant temperatures, and/or more retarded injection timings. This study focuses on the effects of an oxygenated fuel blend (T50) made up of 50% by volume tri-propylene glycol mono-methyl ether with a #2 ULSD emissions-certification fuel (CFA), compared against baseline testing of the CFA fuel without the oxygenate. Experimental measurements include crank-angle resolved natural luminosity (NL) and chemiluminescence (CL) imaging diagnostics. EGR is simulated by adding nitrogen and carbon dioxide to the intake charge to produce a 16% intake-oxygen mole fraction (XO2), and results are compared against cases with no charge dilution (i.e., 21% XO2). Initial experiments with a two-hole tip achieved soot-free LLFCmore » at low loads with the T50 fuel, 240 MPa injection pressure, 50 °C intake-manifold temperature (IMT), 95 °C coolant temperature, and -5 crank-angle degree (CAD) after top-dead-center (ATDC) start of combustion (SOC) timing. The strategy was extended to more moderate loads by employing a 6-hole injector tip, where lowering the IMT to 30 °C, reducing the coolant temperature to 85 °C, and retarding the SOC timing to +5 CAD ATDC resulted in sustained LLFC at both 21% and 16% XO2 at up to 6.2 bar gross indicated mean effective pressure (gIMEP) with T50. The achievement of LLFC was confirmed by independent soot measurements using a smoke meter, spatially integrated natural luminosity from the NL diagnostics, and laser-induced incandescence for measuring soot volume fraction in the exhaust stream. In contrast to the results with T50, LLFC was not achieved under any of the test conditions with CFA. Combustion was stable under LLFC conditions, with a coefficient of variation of gIMEP less than 1.5%. Nitrogen oxides and hydrocarbon emissions were also lowered by up to 25% each for LLFC with T50 relative to using the same operating conditions with CFA. Combustion noise was similarly reduced by 4-6 dBA, and ringing intensity by 60-80%, for LLFC with T50.« less

Effect of injection timing, injector opening pressure, injector nozzle geometry, and swirl on the performance of a direct injection, compression-ignition engine fuelled with honge oil methyl ester (HOME)

Increasing petroleum prices, increasing threat to the environment from exhaust emissions and global warming have generated intense international interest in developing renewable and alternative non-petroleum fuels for engines. Evolving feasible technology and recurring energy crisis necessitated a continued investigation into the search for sustainable and clean-burning renewable fuels. In this investigation, Honge oil methyl ester (HOME) was used in a four stroke, single cylinder diesel engine. Tests were carried out to study the effect of fuel injection timing, fuel injector opening pressure (IOP) and injector nozzle geometry on the performance and combustion of CI engine fuelled with HOME. Injection timing was varied from 19°bTDC (before top dead centre) to 27°bTDC in incremental steps of 4°bTDC; injector opening pressure was varied from 210 bar to 240 bar in steps of 10 bar. Nozzle injectors of 3, 4 and 5 holes, each of 0.2, 0.25 and 0.3 mm size were selected for the study. It was concluded that retarded injection timing of 19°bTDC, increased injector opening pressure of 230 bar and 4 hole nozzle injector of 0.2 mm size resulted in overall better engine performance with increased brake thermal efficiency (BTE) and reduced HC, CO, smoke emissions. Further air-fuel mixing was improved using swirl induced techniques which enhanced the engine performance as well.

Effects of iso-butanol/diesel and n​-pentanol/diesel blends on performance and emissions of a DI diesel engine under premixed LTC (low temperature combustion) mode

This study attempts to achieve simultaneous reduction of smoke and NOx emissions using a combination of low EGR, retarded injection timing and diesel fuel reformulation (with low cetane number alcohols) to enable a partially premixed low temperature combustion (LTC) mode in DI diesel engine. Two higher alcohol/diesel blends, B40 (40% iso-butanol–60% diesel) and P40 (40% n-pentanol–60% diesel) blends were prepared and tested under the combination of three EGR rates (10%, 20% and 30%) and two injection timings (23° and 21° CA bTDC) at high loads and constant engine speed. The performance and emission characteristics of the engine under these conditions are investigated. Results indicate that B40 gives a longer ignition delay, higher peak pressure and higher premixed heat release rate than P40. B40 has superior EGR tolerance and better influence on NOx-smoke trade-off when compared to P40. At retarded injection timing (21° CA bTDC) and 30% EGR, B40 presented simultaneous reduction of NOx (↓ 41.7%) and smoke (↓ 90.8%) emissions with diesel-like performance while P40 presented simultaneous reduction of NOx (↓ 39.3%) and smoke (↓ 15%) emissions with a small drop in performance. It was found that B40 presented better smoke suppression characteristics than P40. Smoke emissions of both blends increased drastically beyond 30% EGR. HC emissions increased and CO emissions remained low for both blends at all EGR rates. The combination of low EGR, late injection and higher alcohol/diesel blends can achieve partially premixed LTC and reduce smoke and NOx emissions simultaneously.

Effect of iso-butanol addition to diesel fuel on performance and emissions of a DI diesel engine with exhaust gas recirculation

Iso-butanol is a second generation biofuel that has the potential to improve energy security and mitigate harmful pollutants in reciprocating engines. The present study investigates the effect of iso-butanol addition to diesel fuel on performance and emissions of a single cylinder direct-injection diesel engine with exhaust gas recirculation (EGR). For this objective, four iso-butanol/diesel blends containing 10%, 20%, 30%, and 40% were prepared by volume basis and tested in the engine under three EGR rates: 10% to 30% (at increments of 10%) with the combination of two injection timings: 23° and 21° crank angle (CA) before top dead center (bTDC). Experimental results showed that the combination of 30% EGR rate, 40% iso-butanol addition (ISB40) and retarded injection timing by 2° CA bTDC simultaneously reduced NOx emissions from 1284 to 749 ppm and smoke opacity from 20.7% to 1.9% with a slight drop in performance. It was found that higher iso-butanol/diesel blends require higher EGR levels to attain optimum levels of smoke and NOx emissions. Both hydrocarbon (HC) and carbon-monoxide (CO) emissions presented an increasing trend at escalating EGR rates. At retarded injection timing, ISB40 blend presented decreased HC emissions, increased CO emissions with a slight drop in performance compared to its injection at original timing.

Influence of injection timing on DI diesel engine characteristics fueled with waste transformer oil

This research work targets on the effective utilization of WTO (waste transformer oil) in a diesel engine, which would rather reduce environmental problems caused by disposing of it in the open land. The waste transformer oil was compared with the conventional diesel fuel and found that it can also be used as fuel in compression ignition engines since the WTO is also a derivative of crude oil. In this present work, the WTO has been subjected to traditional base-catalyzed trans-esterification process in order to reduce the high viscosity of the WTO which helps to effectively utilize WTO as a fuel in DI diesel engine. The objective of the work is to study the influence of injection timing on the performance, emission and combustion characteristics of a single cylinder, four stroke, direct injection diesel engine using TWTO (trans-esterified waste transformer oil) as a fuel. Experiments were performed at four injection timings (23°, 22°, 21°, and 20° bTDC). The results indicate that the retarded injection timing of 20° bTDC resulted in decreased oxides of nitrogen, carbon monoxide and unburned hydrocarbon by 11.57%, 17.24%, and 10% respectively while the brake thermal efficiency and smoke increased under all the load conditions when compared to that of standard injection timing.

Efficiency improvements with low heat rejection concepts applied to diesel low temperature combustion

There is a strong motivation to decrease the production and release of harmful substances such as oxides of nitrogen (NOX) and particulate matter from internal combustion engines. Simultaneously, there are on-going efforts to increase fuel efficiency to curb usage of natural resources and emission of carbon. In general, improvements in one of these areas come at the cost of the other; however, the results of a previous computational study have indicated that emissions can be decreased while simultaneously increasing efficiency through the application of low heat rejection techniques to low temperature combustion. The goal of this study is to experimentally confirm these findings using a light-duty, multi-cylinder diesel engine. Low temperature combustion is realized through high levels of exhaust gas recirculation and retarded injection timings while different degrees of low heat rejection are achieved by means of higher coolant temperatures which should serve to decrease the temperature gradients across the cylinder walls. By applying low heat rejection techniques to diesel low temperature combustion operation, the undesirable side effects of low temperature combustion such as lower combustion and energy conversion efficiencies were found to be mitigated. Specifically, the emissions of carbon monoxide and unburned hydrocarbons were reduced and the loss in fuel conversion efficiency was also diminished. NOX and smoke (an indicator of particulate matter) emissions did increase but they remained at acceptably low levels and below those of conventional combustion. While the full potential of improvements in low temperature combustion was not explored, these results point to the viability of further research into low heat rejection–low temperature combustion concepts.

Experimental investigation on performance and heat release analysis of a pilot ignited direct injection natural gas engine

Pilot ignited direct injection natural gas engines undertake significant advantages over conventional diesel engine with specific combustion mode. In this paper, extensive experiments have been carried out to provide further understanding of performance and heat release rate under different operating conditions. Through the experimental investigations and detailed analysis, it is demonstrated that shortened injection interval and diesel injection pulse width as well as increased injection pressure lead to an increase in maximum in-cylinder pressure and deteriorated combustion noise. The maximum heat release rate is raised by retarding injection timing, reducing injection interval, shortening diesel injection pulse width and increasing injection pressure. The stability of combustion shows uncertain trends with the variation of injection timing and pilot diesel injection quantity, while can be generally improved by the adoption of shorter injection interval and lower injection pressure. It is also revealed that fuel economy can benefit from the application of advanced injection timing, smaller diesel injection pulse width, shorter injection interval and higher injection pressure.

Application of an enhanced Taguchi method for simultaneous reduction of smoke and NOx emissions using oxygenated additives and retarded injection timing in a stationary diesel engine

The present work employs an enhanced Weighted Signal-to-Noise (WSN) ratio method in conventional Taguchi design to determine an optimum combination of a diesel-oxygenate blend and injection timing in a stationary diesel engine with an objective to reduce NOx and smoke emissions simultaneously with best possible performance. An experimental design matrix based on Taguchi’s L 9 orthogonal array was planned and experiments were conducted accordingly. Three parameters, namely oxygenate type, its blend composition with diesel and fuel injection timing with three levels, were chosen. NOx emissions, Smoke opacity, Brake thermal efficiency and Brake specific fuel consumption were taken as response variables. Diethyl ether (DEE), Dimethyl carbonate (DMC) and Diglyme (DGM) were chosen as oxygenates. The individual effects of each parameter in emissions and performance were investigated using analysis of variance. Confirmation experiments were conducted with the suggested optimum combination levels and the results were compared with baseline diesel engine. It was found that diesel with 10 % DGM blend injected at 21° crank angle (CA) is optimum for reducing smoke and NOx emissions simultaneously with best performance. Further, optimum parameter combination for lowest smoke opacity was predicted and confirmed to be 10 % DMC with diesel, injected at 21° CA. The lowest NOx emissions were obtained from 15 % DEE with diesel, injected at 17° CA and best performance from 10 % DEE with diesel, injected at 21° CA. The proposed WSN-based Taguchi method was experimentally verified and found to be effective in predicting an optimum blend for a chosen objective with 67 % reduction in experimentation time.

An effort to enhance hydrogen energy share in a compression ignition engine under dual-fuel mode using low temperature combustion strategies

Abstract A limited hydrogen (H2) energy share due to knocking is the major hurdle for effective utilization of H2 in compression ignition (CI) engines under dual-fuel operation. The present study aims at improvement of H2 energy share in a 7.4 kW direct injection CI engine under dual-fuel mode with two low temperature combustion (LTC) strategies; (i) retarded pilot fuel injection timing and (ii) water injection. Experiments were carried out under conventional strategies of diesel dual-fuel mode (DDM) and B20 dual-fuel mode (BDM); and LTC strategies of retarded injection timing dual-fuel mode (RDM) and water injected dual-fuel mode (WDM). The results explored that the H2 energy share increased significantly from 18% with conventional DDM to 24, and 36% with RDM, and WDM respectively. The energy efficiency increased with increasing H2 energy share under dual-fuel operation; however, for a particular energy share of 18% H2, it decreased from 34.8% with DDM to 33.7% with BDM, 32.7% with WDM and 29.9% with RDM. At 18% H2 energy share, oxides of nitrogen emission decreased by 37% with RDM and 32% with WDM as compared to conventional DDM due to reduction of in-cylinder temperature, while it increased slightly about 5% with BDM. It is emerged from the study that water injection technique is the viable option among all other strategies to enhance the H2 energy share in the engine with a slight penalty of increase in smoke, hydrocarbon, and carbon monoxide emissions.

Performance evaluation of common rail direct injection (CRDI) engine fuelled with Uppage Oil Methyl Ester (UOME)

For economic and social development of any country energy is one of the most essential requirements. Continuously increasing price of crude petroleum fuels in the present days coupled with alarming emissions and stringent emission regulations has led to growing attention towards use of alternative fuels like vegetable oils, alcoholic and gaseous fuels for diesel engine applications. Use of such fuels can ease the burden on the economy by curtailing the fuel imports. Diesel engines are highly efficient and the main problems associated with them is their high smoke and NOx emissions. Hence there is an urgent need to promote the use of alternative fuels in place of high speed diesel (HSD) as substitute. India has a large agriculture base that can be used as a feed stock to obtain newer fuel which is renewable and sustainable. Accordingly Uppage oil methyl ester (UOME) biodiesel was selected as an alternative fuel. Use of biodiesels in diesel engines fitted with mechanical fuel injection systems has limitation on the injector opening pressure (300 bar). CRDI system can overcome this drawback by injecting fuel at very high pressures (1500-2500 bar) and is most suitable for biodiesel fuels which are high viscous. This paper presents the performance and emission characteristics of a CRDI diesel engine fuelled with UOME biodiesel at different injection timings and injection pressures. From the experimental evidence it was revealed that UOME biodiesel yielded overall better performance with reduced emissions at retarded injection timing of -10° BTDC in CRDI mode of engine operation.