Increasing Engine Load Research Articles

Majorization of working parameters for non-thermal plasma reactor and impact on no oxidation of diesel engine

The main target of this work is to realize the function of pre-oxidizing NO from diesel engine’s exhaust by using self-designed double-dielectric Non-thermal Plasma (NTP) reactor. The majorized discharge frequency and discharge peak to peak voltage (Vp-p) range for NTP reactor were obtained through air discharge test. The diesel engine test bench was established to observe the effect of NTP on the volume fraction of NO. The results showed that there were more active substances and fewer by-products in NTP reactor when discharge frequency was 9 kHz and Vp-p was between 9 kV and 23 kV; Exhaust flows had insignificant effect on the performance of NTP pre-oxidizing NO; The ability of NTP to pre-oxidize NO gradually weakened with the increase of engine load, and when the engine load were 0 % and 25 %, the ratio of NO/NO2 could reach 1. In such working conditions, SCR system could improve the conversion rate of the NOx at low-temperature zone through quick reaction combined with NTP.

Achieving clean and efficient engine operation up to full load by combining optimized RCCI and dual-fuel diesel-gasoline combustion strategies

This experimental work investigates the capabilities of the reactivity controlled compression ignition combustion concept to be operated in the whole engine map and discusses its benefits when compared to conventional diesel combustion. The experiments were conducted using a single-cylinder medium-duty diesel engine fueled with regular gasoline and diesel fuels. The main modification on the stock engine architecture was the addition of a port fuel injector in the intake manifold. In addition, with the aim of extending the reactivity controlled compression ignition operating range towards higher loads, the piston bowl volume was increased to reduce the compression ratio of the engine from 17.5:1 (stock) down to 15.3:1.To allow the dual-fuel operation over the whole engine map without exceeding the mechanical limitations of the engine, an optimized dual-fuel combustion strategy is proposed in this research. The combustion strategy changes as the engine load increases, starting from a fully premixed reactivity controlled compression ignition combustion up to around 8bar IMEP, then switching to a highly premixed reactivity controlled compression ignition combustion up to 15bar IMEP, and finally moving to a mainly diffusive dual-fuel combustion to reach the full load operation. The engine mapping results obtained using this combustion strategy show that reactivity controlled compression ignition combustion allows fulfilling the EURO VI NOx limit up to 14bar IMEP. Ultra-low soot emissions are also achieved when the fully premixed combustion is promoted, however, the soot levels rise notably as the combustion strategy moves to a less premixed pattern. Finally, the direct comparison of reactivity controlled compression ignition versus conventional diesel combustion using the nominal engine settings, reveals that reactivity controlled compression ignition can be a potential solution to reduce the selective catalyst reduction and diesel particulate filter aftertreatment necessities with a simultaneous improving of the thermal efficiency.

Effect of diesel-biodiesel-ethanol blend on combustion, performance, and emissions characteristics on a direct injection diesel engine

The paper presents results of co-combustion of diesel-biodiesel-ethanol fuel blend in direct injection Diesel engine. Test was performed at constant rotational speed at three commonly used loads of this engine: 100%, 85%, and 70% of load. During the test hydrated ethanol was used at a concentration of 89% of alcohol. In this study, the ethanol fuel was added to diesel-biodiesel fuel blend with concentrations up to 50% with the increment of 5%. The biodiesel was used as an additive to pre-vent the stratification of ethanol and diesel blends. Thermodynamic parameters of engine were analyzed, and combustion process and exhaust emission were characterized. It turned out that with the increase in engine load is possible to utilize larger ethanol fraction in blend. With the increase of ethanol fuel in blend the in-crease in ignition delay (38.5% for full load) was observed, but burning duration decreased (49% for full load). The ethanol fuel share in blend generally causes the increase in NOx emission (42% for full load) due to higher oxygen content and higher in-cylinder temperatures. It turned out that, at full load the unrepeatability of indicated mean effective pressure was near the same up to 50% of ethanol fuel in blend (about 2%). In case of partial load at higher ethanol fuel fraction the in-crease in indicated mean effective pressure un-repeatability was observed.

Clean combustion of n-butanol as a next generation biofuel for diesel engines

This work investigates the applicability of n-butanol as a next generation biofuel to replace diesel in compression ignition engines for efficient operation, pollutant mitigation, and CO2 reduction. A high compression ratio (18.2:1) diesel research engine is configured to run on neat n-butanol. Due to the fuel property departure from diesel, n-butanol combustion exhibits striking combustion characteristics. Alternative combustion strategies, including via partially premixed compression ignition and homogeneous charge compression ignition, are enabled efficiently owing to distinctive fuel properties of n-butanol. The compression ignition of the (partially) premixed n-butanol and air mixture is capable of producing diesel-like engine efficiency and significant nitrogen oxide and smoke reductions. As the engine load increases, however, such neat n-butanol combustion exhibits rapid burning and suffers abrupt pressure rise. Thereby the engine load is generally limited below 50% of the baseline capability. A split-combustion strategy, which employs multiple event fuel injections, is found to be effective to modulate the noise of n-butanol clean combustion, thereby enabling neat n-butanol application across the full engine load range.

Nanostructure analysis of particulate matter emitted from a diesel engine equipped with a NTP reactor

An investigation of the nanostructures of particulate matter (PM) emitted from a diesel engine equipped with a non-thermal plasma (NTP) after-treatment device was conducted. Raw PM, PM escaping from the NTP reactor (PM-NTP), and PM collected on the collection plate (PM aggregation) were sampled at different engine loads. High-resolution transmission electron microscopy (HRTEM) images were used to analyse the nanostructures. Raw PM showed onion like structures with short lattice fringes, however, core-shell like structures were observed for PM sampled at 60% engine load after exhaust flowed through the NTP reactor. The diameter decreased for PM-NTP and PM aggregation compared with raw PM, regardless of the engine loads. The core-shell like structures were evident after PM was partially oxidized. The average fringe separation distance, length, and tortuosity were 0.95–1.26nm, 2.90–3.70nm, and 1.45–1.97 respectively. The fringe separation distance increased with increasing engine load for the same kind of PM. The influence of plasma on the changes of nanostructure parameters was greatly dependent on the engine loads. The fringe length dominated the changes of the instantaneous activation energy during the oxidation process, while it was less important for apparent rate constant.

Influence of PM Size Distribution and Ingredients on DPF Regeneration by Non-thermal Plasma Technology

Experimentation was conducted to analyze the diesel particulate filters (DPF) trap under four different engine loads with particle size analysis and thermo-gravimetric analysis introduced to characterize particulate matter (PM) samples. DPF regeneration was achieved utilizing an oxygen-fed non-thermal plasma (NTP) injection system. Results indicated that accompanying the increase of engine load, the concentration of nucleation mode particles decrease while that of accumulation mode particles and the total concentration number increase at first and then decrease with the total concentration number of PM peaking at 50% load. H2O and soluable organic fraction in PM demonstrate a downward trend while dry soot exhibits an upward trend in mass fraction with the increasing load. NTP may then separate PM into CO and CO2. Size distribution and ingredients of PM trapped by DPF under different loads vary, thus the intensity of reaction between PM and radical gases produced by NTP is different. C1 (C in CO) exhibited a declining trend with the increasing of engine load, while C2 (C in CO2) and C12 (sum of C1 and C2) increase first and decrease after. Mass of PM removal maximizes at 50% load while DPF regeneration effect is the most remarkable.

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

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

Morphology and volatility of particulate matter emitted from a gasoline direct injection engine fuelled on gasoline and ethanol blends

The particulate matter emitted from a turbocharged, four cylinder, wall-guided, gasoline direct injection (GDI) engine fuelled with gasoline and ethanol blends was investigated, and characterized by size distribution, mass-mobility exponent, effective density, and volatility using tandem measurements from differential mobility analysers (DMA) and a centrifugal particle mass analyser (CPMA). Three engine loads were tested at 2250 RPM (4%, 13%, and 26% of maximum load) in addition to an idle condition while the engine was fuelled using gasoline mixed with ethanol fractions of 0% (E0), 10% (E10), and 50% (E50) by volume. An increase in engine load increased particle number concentration, although idle produced approximately as many particles as at 13% load. In the majority of cases, an increase in ethanol fraction decreased number concentration. The fraction of the number of particles comprised of only volatile material to total number of particles (number volatile fraction) both overall and as a function of particle mobility-equivalent diameter was under 10 percent at all engine conditions and fuels (measured after a three-way catalytic converter). The size-segregated ratio of the mass of internally mixed volatile material to total particle mass was similarly low. Volatility measurements were conducted using a thermodenuder set to 300°C. Mass-mobility exponent was seen to range between 2.28 and 2.60. Effective density increased with load, and in general mass-mobility exponent increased as well. Effective density decreased with an increase in ethanol fraction and a slight decrease in mass-mobility exponent was also observed for all conditions except idle. No significant changes in effective density, particle size, or number concentration were observed in GDI soot after denuding particle samples.

Trace metals and ions in particulates emitted by biodiesel fuelled engine

Particulates emitted by a transportation diesel engine fuelled with Karanja biodiesel blend (20% v/v biodiesel blended with 80% v/v mineral diesel) were tested for the trace metal content and inorganic ions. These particulate were analyzed and compared with baseline mineral diesel particulate for 9 commonly present trace metals namely Ca, Fe, Cr, Cu, Mn, Pb, Ni, Ba and Cd and inorganic anions such as nitrates, chlorides, fluorides and sulphates. Trace metals in particulate decreased with increasing engine load. Ions analyzed in particulate from diesel and biodiesel also showed decreasing trend with increasing engine load. Biodiesel origin particulate contained slightly lower amount of trace metals and inorganic ions compared to mineral diesel for similar operating conditions except nitrates. Particulate sampled on the quartz filter paper were also analyzed for their morphology and 1000× magnification images were captured using scanning electron microscopy (SEM) in order to visualize bulk particulate emission from Karanja biodiesel exhaust compared to baseline mineral diesel.

Experimental investigations on a cascaded steam-/organic-Rankine-cycle (RC/ORC) system for waste heat recovery (WHR) from diesel engine

A novel cascaded RC/ORC system that comprises a steam Rankine cycle as the high-temperature loop (H-RC) and an organic Rankine cycle as the low-temperature loop (L-ORC) was constructed and experimentally investigated to recover waste heat from exhaust gas of a heavy-duty diesel engine (DE). By monitoring key parameters of the RC/ORC system against time, good system stability and satisfying thermal states of working fluids were observed. Impacts that the engine operations have on this proposed waste-heat-recovery (WHR) system were studied, indicating that waste heat recovered from the gas increases gradually and greatly as the engine load increases, yet decreases slightly as the speed grows. At full loads at speeds lower than 2050rpm, up to 101.5kW of waste heat can be abstracted from the gas source, showing a promising heat transfer potential. Besides, observations of key exergy states as well as estimations and comparisons of potential output power were carried out stepwise. Results indicated that up to 12.7kW of output power could be obtained by the novel RC/ORC system under practical estimations. Comparing to the basic diesel engine, the power increment reaches up to 5.6% by equipping the cascaded RC/ORC system.

Investigation on the combustion noise of a pilot-ignited direct-injection natural-gas engine

In this paper, the effects of the injection timing, the injection pressure and the engine load on the combustion noise of a pilot-ignited direct-injection natural-gas engine were explored by analysing the separate components of the in-cylinder pressure. The results suggested that retarding the injection timing and reducing the injection pressure are effective ways of controlling the combustion noise. This can be attributed to the promoted burning rate at advanced injection timings and to the increased injection pressure. However, the effect of the engine load seems to be less obvious, although the resonance pressure level appears to increase with increasing engine load; the estimated combustion noise shows a decreasing tendency.

Evaluation of toxic potential of particulates emitted from Jatropha biodiesel fuelled engine

This study involved a comparative experimental characterization of trace metals and relative toxicity evaluation of particulates emitted by a medium-duty transportation diesel engine using diesel and 20% (v/v) Jatropha biodiesel blend (B20). The engine was operated at 1800 rpm and particulate samples were collected on a filter paper at five loads (0%, 25%, 50%, 75% and 100% rated load) at steady state using a partial flow dilution tunnel, for both diesel and B20. Samples were then analyzed for trace metals, particulate morphology, total organic carbon and benzene soluble organic fraction (BSOF), which is a marker of toxicity. Concentrations of crust elements (Al, Ca, Fe and Mg) in the particulates were relatively higher than that of anthropogenic elements (Cd, Cr, Cu, and Zn) for both test fuels. B20 emitted relatively lower trace metal concentrations in particulates compared to baseline mineral diesel and these concentrations decreased with increasing engine load. Concentrations of gaseous emissions namely CO and THC in biodiesel exhaust were relatively lower than mineral diesel however NOx was relatively higher. Scanning electron microscopy of the particulate samples collected on the filter papers was done along with EDAX analysis for comparison.

바이오디젤-CNG 혼소엔진에서 파일럿 분사량이 연소 및 배기 특성에 미치는 영향

The effect of pilot injection quantity on the combustion and emissions characteristics of a compression ignition engine with a biodiesel-compressed natural gas (CNG) dual fuel combustion (DFC) system is studied in this work. Biodiesel is used as a pilot injection fuel to ignite the main fuel, CNG of DFC. The pilot injection quantity is controlled to investigate the characteristics of combustion and exhaust emissions in a single cylinder diesel engine. The injection pressure and injection timing of pilot fuel are maintained at approximately 120 MPa and BTDC 17 crank angle, respectively. Results show that the indicated mean effective pressure (IMEP) of biodiesel-CNG DFC mode is similar to that of diesel-CNG DFC mode at all load conditions. Combustion stability of biodiesel-CNG DFC mode decreased with increase of engine load, but no notable trend of cycle-to-cycle variations with increase of pilot injection quantity is discovered. The combustion of biodiesel-CNG begins at a retarded crank angle compared to that of diesel-CNG at low load, but it is advanced at high loads. Smoke and NOx of biodiesel-CNG are simultaneously increased with the increase of pilot fuel quantity. Compared to the diesel-CNG DFC, however, smoke and NOx emissions are slightly reduced over all operating conditions. Biodiesel-CNG DFC yields higher <TEX>$CO_2$</TEX> emissions compared to diesel-CNG DFC over all engine conditions. CO and HC emissions for biodiesel-CNG DFC is decreased with the increase of pilot injection quantity.

Effect of varying compression ratio on combustion, performance, and emissions of a hydrogen enriched compressed natural gas fuelled engine

Compressed natural gas (CNG) and hydrogen are potential alternate fuels for internal combustion (IC) engines, which are capable of sustaining large part of global transportation system in future. However these fuels suffer from some combustion related issues. A blend of CNG and hydrogen cancels their negative individual properties, mutually. As a consequence, hydrogen enriched compressed natural gas (HCNG) is emerging as an acceptable alternative fuel for spark ignition (SI) engines. HCNG resists knocking hence it delivers superior engine performance. Therefore it is usable at higher compression ratios (CRs). Effect of CR on HCNG fuelled engine's performance, combustion and emission characteristics is experimentally evaluated in this study. Experiments were performed at three CRs (10, 11 and 12) under identical conditions, in order to assess their effect on two different HCNG compositions (20HCNG and 30 HCNG) for comparison. Brake specific energy consumption (BSEC) was lower at higher CRs which decreased with increasing engine load/ brake mean effective pressure (BMEP). Brake thermal efficiency (BTE) was higher at higher CRs for both HCNG mixtures. 30HCNG showed relatively higher BTE and lower BSEC compared to 20HCNG. Higher peak cylinder pressures were obtained for higher CRs. Combustion parameters such as rate of pressure rise (RoPR), heat release rate (HRR) and cumulative heat release (CHR) improved at higher CRs for both HCNG mixtures however 30HCNG performed slightly better amongst the two HCNG compositions. Regulated emissions such as HC, CO and NOx were relatively higher at higher CRs, but CO2 emission was relatively lower.

Theoretical and experimental study on the performance of a diesel engine fueled with diesel–biodiesel blends

This study reports the effects of engine load and biodiesel percentage on the performance of a diesel engine fueled with diesel–biodiesel blends by experiments and a new theoretical model based on the finite-time thermodynamics (FTT). In recent years, biodiesel utilization in diesel engines has been popular due to depletion of petroleum-based diesel fuel. In this study, performance of a single cylinder, four-stroke, direct injection (DI) diesel engine fueled with diesel–biodiesel mixtures has been experimentally and theoretically investigated. The simulation results agree with the experimental data. After model validation, the effects of engine load and biodiesel percentage on engine performance have been parametrically investigated. The results showed that, effective power increases constantly, effective efficiency increases to a specified value and then starts to decrease with increasing engine load at constant biodiesel percentage and compression ratio. However, effective efficiency increases, effective power decreases to a certain value and then begins to increase with increasing biodiesel percentage at constant equivalence ratio and compression ratio.

Effect of an emission-reducing soluble hybrid nanocatalyst in diesel/biodiesel blends on exergetic performance of a DI diesel engine

The present study was set to explore the effect of a novel soluble hybrid nanocatalyst in diesel/biodiesel fuel blends on exergetic performance parameters of a DI diesel engine. Experiments were carried out using two types of diesel/biodiesel blends (i.e., B5 and B20) at four concentrations (0, 30, 60 and 90 ppm) of the hybrid nanocatalyst, i.e., cerium oxide immobilized on amide-functionalized multiwall carbon nanotubes (MWCNT). Furthermore, the exergy analysis was performed at five different loads and two engine speeds. The results obtained revealed that the exergetic parameters were profoundly influenced by engine speed and load. In general, increasing engine speed and load increased the magnitude of the destructed exergy. Moreover, the exergy efficiency increased by increasing engine load, while it decreased by elevating engine speed. However, the applied fuel blends had approximately similar exergetic efficiency and sustainability index. Interestingly, a remarkable reduction in emissions was obtained by incorporating the soluble catalyst nanoparticles to the diesel/biodiesel blends. Thus, it could be concluded that the diesel/biodiesel blends containing amide-functionalized MWCNTs-CeO2 catalyst might substitute the use of pure diesel fuel without any unfavorable change in the exergetic performance parameters of the DI engines.

Passive SCR for lean gasoline NOX control: Engine-based strategies to minimize fuel penalty associated with catalytic NH3 generation

Lean gasoline engines offer greater fuel economy than common stoichiometric gasoline engines. However, excess oxygen prevents the use of the current three-way catalyst (TWC) to control nitrogen oxide (NOX) emissions in lean exhaust. A passive SCR concept, introduced by General Motors Global R&D, makes use of a TWC that is already onboard to generate NH3 under slightly rich conditions, which is stored on the downstream SCR. The stored NH3 is then used to reduce NOX emissions when the engine switches to lean operation. In this work, the effect of engine parameters, such as air-fuel equivalence ratio and spark timing, on NH3 generation over a commercial Pd-only TWC with no dedicated oxygen storage component was evaluated on a 2.0-liter BMW lean burn gasoline direct injection engine. NOX reduction, NH3 formation, and reductant utilization processes were evaluated, and fuel efficiency was assessed and compared to the stoichiometric engine operation case. Air-fuel equivalence ratio was found to be one of the most important parameters in controlling the NH3 production; however, the rich operation necessary for NH3 production results in a fuel consumption penalty. The fuel penalty can be minimized by adjusting spark timing to increase rich-phase engine out NOX emissions and, thereby, NH3 levels. Additionally, higher engine out NOX during engine load increase to simulate acceleration resulted in additional fuel savings. A 10% fuel consumption benefit was achieved with the passive SCR approach by optimizing rich air-fuel equivalence ratio and spark timing while also utilizing acceleration load conditions.

Effects of piston bowl geometry on Reactivity Controlled Compression Ignition heat transfer and combustion losses at different engine loads

This work investigates the effects of the piston bowl geometry on RCCI (Reactivity Controlled Compression Ignition) heat transfer and combustion losses and its repercussion on the engine efficiency. For this purpose, three piston geometries with compression ratio 14.4:1 have been studied and compared by means of computational modeling. In addition, the engine operating conditions proposed at low, medium and high load were also validated experimentally in a heavy-duty single-cylinder engine adapted for dual fuel operation. The engine speed was kept constant at 1200 rev/min during the research.Results suggest that heat flux through the piston surface represent the major portion of the heat transfer energy. Thus, the comparison of the three geometries demonstrates that reduced piston surface area and reduced charge motion, are the key factors to improve the gross indicated efficiency over the different engine loads. Moreover, it is found that a shallow piston geometry with a smooth transition from the center to the squish region, with a 16% reduced surface area, strongly improves the gross work at low load. However, this gain diminishes due to increased combustion losses as engine load increases. Finally, an intermediate geometry was confirmed as the best balanced piston geometry for RCCI operation over the three different loads.

Effect of the piston top contour on the tumble flow and combustion features of a GDI engine with a CMCV: a CFD study

ABSTRACTIn spite of much progress in the development of gasoline direct injection (GDI) engines, choosing an appropriate piston top contour to obtain desirable combustion efficiency is still an arduous process for engineers. This study investigates the combined effects of piston bowl geometry and a charge motion control valve (CMCV) on tumble flow and combustion features in GDI engines. Based on the model validation, the processes of intake, spray, mixture formation and combustion at different engine speeds are simulated and analyzed for different piston shapes for the two cases of opening and closing the CMCV. The results show that the bowl on the top of piston is beneficial for the formation and development of tumble flow. The flat top piston with the CMCV closed is able to achieve acceptable combustion pressure. However, with the increase of engine speed and load, the advantages of the flat top pistons gradually disappear; the dual offset bowl piston has a minimum tumble ratio and turbulence kinetic energy (TKE) at the end of the compression stroke because of the projection in the middle of the piston top surface which leads to a lower pressure rise rate and a reduced flame propagation speed at high load. The closed CMCV contributes to a faster evaporation rate and a more uniform mixture at lower speeds. It is not recommended for use at high speeds due to lower intake air mass and reduced combustion pressure. The research provides an effective way for engineers to choose an appropriate piston top contour combined with a CMCV to obtain desirable combustion efficiency.

Emissions Study and Estimation of Carbon Dioxide Production from Jatropha Curcas Oil Biodiesel

ABSTRACTThe goal of this study was to analyse the combustion characteristics and emissions of Jatropha curcas biodiesel (JCB) when run in a diesel engine. Jatropha curcas oil was used to produce Jatropha curcas biodiesel (JCB) through a transesterification process. The major fuel properties of JCB, including the acid value, kinematic viscosity, flash point, gross heating value, and iodine value, were determined and compared with that of soybean biodiesel (SBM), sunflower seed biodiesel (SFM), mackerel fish oil biodiesel (MB), and premium diesel (D). JCB had a higher density, acid value, kinematic viscosity, iodine value and flash point, but a lower gross heating value, than D. JCB was then used to analyze combustion characteristics, CO, CO2, NO, NOx, SO2, and particulate matter (PM), under varied engine speeds and varied engine loads. The experimental results show CO2 concentration increased with increasing engine loads for all fuels. Engine trials on D exhibited better combustion efficiency at lower engine loads (0 kW–4 kW) but engine trials on JCB exhibited better combustion efficiency for higher engine loads (5 kW– 8 kW). JCB emitted more NO and NOx on a loaded engine. Engine trials on JCB emitted higher PM concentration when the engine was not loaded, while engine trials on MB produced higher PM concentration when the engine was loaded. The estimated CO2 emissions for JCB, MB, and D are 9221.3, 9617.2, and 10185.0 g (gal fuel)–1, respectively.