Higher Peak Cylinder Pressure Research Articles

Analyzing the effect of carbon nanoparticles on the combustion performance and emissions of a DI diesel engine fueled with the diesel-methanol blend

With the energy crisis and worsening environmental pollution, methanol, as a carbon-neutral fuel, has become a research hotspot in the field of internal combustion engines. This study discusses the influence of different kinds (graphite oxide, GO; multilayer graphene, MG; carbon nanotubes, CNT) and concentrations of carbon nanoparticles, which do not introduce any new elements, added to the diesel-methanol blend on combustion performance and exhaust emissions in a direct injection (DI) diesel engine across diverse operating load conditions. The results showed that the nano-fuels with carbon nano-additives had a better combustion process, with higher peak cylinder pressure (Pmax) and peak heat release rate (HRRmax), and lower ignition delay (ID) and combustion duration (CD). Moreover, the presence of carbon nano-additives resulted in an improvement in brake thermal efficiency (BTE) and a decrement in the break-specific fuel consumption (BSFC). The nano-fuels with GO showed the best optimization effect on the combustion process, followed by MG and CNT. As for emission, the nano-fuels had fewer emissions of CO, HC, and smoke opacity. The nano-fuels with CNT achieved the most significant decrease in emissions of CO and HC. While the presence of GO had the best reduction effect in smoke opacity. However, there was a slight increase in NOx emission. The experimental findings demonstrate that the utilization of carbon nanoparticles in nano-fuels can effectively enhance the application of methanol in internal combustion engines.

Performance, combustion and emissions characteristics of palm biodiesel blends in CI engines

Biodiesel is an alternative fuel with the same properties compared with diesel. Biodiesel is one of the renewable resources. After using cooked oil is thrown away and it affects the environment. So, with the help of waste cooked oil is used to produce biodiesel the process is going to be done by the Trans-esterification process the Biodiesel were prepared as B60 and B100. The experiment was carried out in a single cylinder four stroke diesel engine at various crank angles of 19, 23 and 27 for both B60 and B100. Biodiesel has a higher peak cylinder pressure than diesel fuel during retardation of crank angle. It was found that B100 blends have lower net heat release, rate of pressure rise and lower mass fraction due to inferior volatility and higher viscosity. B60 IT23 blend has a higher mechanical efficiency than diesel. The CO2 emissions of biodiesel (B60 IT23) are slightly less than diesel. Hence the replacement of Palm biodiesel blends in the place of diesel gives promising results; which is nearer to diesel.

Initial Results on a New Light-Duty 2.7-L Opposed-Piston Gasoline Compression Ignition Multi-Cylinder Engine

Abstract Gasoline compression ignition (GCI) is a cost-effective approach to achieving diesel-like efficiencies with low emissions. The fundamental architecture of the two-stroke Achates Power Opposed-Piston (OP) Engine enables GCI by decoupling piston motion from cylinder scavenging, allowing for flexible and independent control of cylinder residual fraction and temperature leading to improved low-load combustion. In addition, the high peak cylinder pressure and noise challenges at high-load operation are mitigated by the lower brake mean effective pressure (BMEP) operation and faster heat release for the same pressure rise rate of the OP Engine. These advantages further solidify the performance benefits of the OP Engine and demonstrate the near-term feasibility of advanced combustion technologies, enabled by the opposed-piston architecture. This paper presents initial results from steady-state testing on a brand new 2.7-L OP GCI multi-cylinder engine (MCE) designed for light-duty truck applications. Successful GCI operation calls for a high compression ratio (CR), leading to higher combustion stability at low loads, higher efficiencies, and lower cycle HC + NOX emissions. Initial results show a cycle average brake thermal efficiency (BTE) of 31.7%, which is already greater than 11% conventional engines, after only ten weeks of testing. Emissions results suggest that Tier 3 Bin 160 levels can be achieved using a traditional diesel after-treatment system. Combustion noise was well controlled at or below the United States Council for Automotive Research limits. In addition, initial results on catalyst light-off mode with GCI are also presented.

A comparative study of combustion and emission characteristics of dual-fuel engine fueled with diesel/methanol and diesel–polyoxymethylene dimethyl ether blend/methanol

In this study, a comparative study of the combustion characteristics and performances of a dual-fuel engine fueled with diesel/methanol and diesel–polyoxymethylene dimethyl ether blend/methanol was conducted. All the experiments were conducted on a heavy-duty common rail diesel engine at an engine speed of 1800 r/min. The engine loads were fixed at low, medium, and heavy loads, with the brake mean effective pressure at 0.42 MPa, 0.7 MPa and 0.9 MPa, respectively. Methanol substitution ratio (MSR) was defined as the torque output contributed by methanol to the total torque output, and in this study, three MSRs (0 %, 20 %, and 40 %) were defined. Diesel–polyoxymethylene dimethyl ether (PODE) blend was defined as P50 (50 % diesel and 50 % PODE by volume) to clarify the effect of PODE addition on engine performance. The results showed that the dual-fuel engine fueled with P50/methanol had a higher peak cylinder pressure, lower first peak heat release rate (HRR), and higher second peak HRR than the dual-fuel engine fueled with diesel/methanol. Both the ignition delay and combustion duration of the dual-fuel engine decreased when the pilot fuel injection changed from diesel to P50. Moreover, both NOx emissions and particulate matter produced by the P50/methanol engine were lower than those produced by the diesel/methanol engine for the specific MSR and engine load.

Influence of the addition of titanium oxide nanoparticles to Fischer-Tropsch diesel synthesised from coal on the combustion characteristics and particulate emission of a diesel engine

The use of Fischer–Tropsch (F–T) diesel synthesised from coal in automobiles can alleviate petroleum shortages and promote clean utilisation of coal. Because F–T diesel does not contain oxygen, in this study, we added TiO2 nanoparticles and n-octanol to the F–T diesel to serve as oxygenated enhancers to increase the oxygen content and reduce the particulate matter emission of F–T diesel. To achieve better combustion characteristics and emission performance, TiO2 nanoparticles with different concentrations (20, 50, and 100 ppm) were dispersed to the fuel blends of F–T diesel and n-octanol to determine the optimum amount of TiO2 nanoparticles. The brake thermal efficiency (BTE), combustion stability, number concentration, and size distribution of the ultrafine particulate (UFP) emission of the three nano-emulsion fuels were investigated on a turbocharged heavy-duty diesel engine. The experimental results indicated that the BTE of the F–T diesel and that of the nano-emulsion fuel T50 increased by 0.75 % and 2.26 %, respectively, compared with petro-diesel. The nano-emulsion fuels had higher peak cylinder pressure and peak heat release rate owing to the faster combustion rate caused by the micro-explosion of fuel droplets and higher thermal conductivity caused by the high surface-to-volume ratio of TiO2 nanoparticles. Moreover, the nano-emulsion fuels exhibited higher cyclic variations of peak cylinder pressures and more dispersed corresponding crank angles with the increase in the concentration of TiO2 nanoparticles. Compared with petro-diesel, the soot emission of the F–T diesel was reduced by an average of 27.32 % at various loads, whereas that of the optimal T50 decreased by an average of 43.61 %. Additionally, the number concentration of UFPs of T50 was reduced by an average of 21.2 % compared to the F–T diesel. At low loads, the three nano-emulsion fuels exhibited greater geometric mean diameters (GMDs) of UFPs and lower ratios of nucleation mode particulates (NMPs) owing to the higher fuel viscosity in the pre-injection stage at a lower in-cylinder temperature. At medium and high loads, the nano-emulsion fuels exhibited smaller GMDs of UFPs and higher ratios of NMPs owing to micro-explosion and secondary atomisation at higher temperatures.

Emission profiling of a common rail direct injection diesel engine fueled with hydrocarbon fuel extracted from waste high density polyethylene as a partial replacement for diesel with some modifications

A hydrocarbon fuel extracted from waste high-density polyethylene (WHDPE) by catalytic pyrolysis in a batch scale reactor is blended with diesel by 30% vol. (called as D70H30) is tested in a variable compression ratio engine equipped with a common rail system. Experiments were conducted at three compression ratios (16:1, 17.5:1, and 19:1) and exhaust gas re-circulation (EGR) rates (0%, 10%, and 20%) at the engine’s rated power to evaluate its combustion, performance and emission characteristics. The results revealed that, increasing the compression ratio resulted in higher peak cylinder pressure (PCP) and heat release rates (HRR). Introduction of EGR diminished both PCP and HRR peaks. The brake thermal efficiency of D70H30 blend was 4% lower than diesel at same operating conditions which got better at higher compression ratio without EGR. NOx emission was highest when injected at compression ratio 19:1 and at 0% EGR rate which was 6% and 3% higher than diesel and D70H30 blend operated at engine stock settings. In comparison with baseline diesel smoke opacity remained lower at all operating conditions, where lowest smoke emission was recorded at CR19 and at 0% EGR rate. UHC and CO emission followed the similar trend of smoke opacity. Whereas CO2 emission increased with compression ratio and reduced with induction of EGR. It can be concluded from the study that at higher compression ratio and low EGR rates D70H30 blend can be effectively utilized in a CRDi engine.

Finite-Time Thermodynamic Modeling and a Comparative Performance Analysis for Irreversible Otto, Miller and Atkinson Cycles.

Finite-time thermodynamic models for an Otto cycle, an Atkinson cycle, an over-expansion Miller cycle (M1), an LIVC Miller cycle through late intake valve closure (M2) and an LIVC Miller cycle with constant compression ratio (M3) have been established. The models for the two LIVC Miller cycles are first developed; and the heat-transfer and friction losses are considered with the effects of real engine parameters. A comparative analysis for the energy losses and performances has been conducted. The optimum compression-ratio ranges for the efficiency and effective power are different. The comparative results of cycle performances are influenced together by the ratios of the energy losses and the cycle types. The Atkinson cycle has the maximum peak power and efficiency, but the minimum power density; and the M1 cycle can achieve the optimum comprehensive performances. The less net fuel amount and the high peak cylinder pressure (M3 cycle) have a significantly adverse effect on the loss ratios of the heat-transfer and friction of the M2 and M3 cycles; and the effective power and energy efficiency are always lower than the M1 and Atkinson cycles. When greatly reducing the weights of the heat-transfer and friction, the M3 cycle has significant advantage in the energy efficiency. The results obtained can provide guidance for selecting the cycle type and optimizing the performances of a real engine.

Assessment of performance, emission and combustion characteristics of palm, jatropha and Calophyllum inophyllum biodiesel blends

Biodiesel is an alternative diesel fuel that is produced from renewable resources. Energy studies conducted over the last two decades focused on solutions to problems of rising fossil fuel price, increasing dependency on foreign energy sources, and environmental concerns. Palm oil biodiesel is mostly used in Malaysia. Engine performance and emission tests were conducted with a single-cylinder diesel engine fueled with palm, jatropha and Calophyllum inophyllum biodiesel blends (PB10, PB20, JB10, JB20, CIB10, and CIB20) and then compared with diesel fuel at a full-load engine speed range of 1000–2400rpm. The average brake specific fuel consumption increased from 7.96% to 10.15% while operating on 10%, and 20%, blends of palm, jatropha and C. inophyllum biodiesel. The average brake power for PB10 and PB20 were 9.31% and 12.93% lower respectively compared with that for diesel fuel. JB10 showed higher amount of brake specific fuel consumption than diesel and other biodiesel blends. PB20 produces comparatively lower CO and HC emissions than diesel and biodiesel blends. JB10 showed 31.09% lower smoke opacity than diesel fuel. Diesel produces lower amount of NOX emission compared to biodiesel blends. The higher peak cylinder pressure and heat release rate were found with CIB blends compared to diesel fuel, palm and jatropha biodiesel blends. Results indicated that PB20 has better engine performance, and lower emission compared with diesel and biodiesel blends. Thus, PB20 is suitable for use in diesel engines without the need for any engine modification.

Effect of Mahua Biodiesel Blends on the Combustion Characteristics of Direct Injection CI Engine at Various Compression Ratios

In the current study, combustion characteristics were evaluated using mahua biodiesel blends at different compression ratios on a direct injection CI engine. Non edible mahua oil was transesterified into biodiesel by two stage technique. Combustion parameters were evaluated for B5, B10 and B20 blends of mahua biodiesel with diesel and they were compared with straight diesel at compression ratios of 16, 17 and 18.Compression ratio was varied without altering the combustion chamber geometry and the static spill timing was set to 23° bTDC. Parameters like In cylinder pressure, heat release rate, rate of pressure rise and cumulative heat release were evaluated in this study at 100% engine loading conditions. Higher peak cylinder pressure and heat release was observed at higher compression ratios. The ignition delay of the blends were slightly higher compared to diesel at all CR tested. Peak cylinder pressure of the blends was slightly higher at CR 18. The ignition delay was also observed to be lower at higher compression ratio. The peak pressure was observed closer to TDC at higher compression ratios for all fuels tested.

Double Compression Expansion Engine Concepts: A Path to High Efficiency

Internal combustion engine (ICE) fuel efficiency is a balance between good indicated efficiency and mechanical efficiency. High indicated efficiency is reached with a very diluted air/fuel-mixture and high load resulting in high peak cylinder pressure (PCP). On the other hand, high mechanical efficiency is obtained with very low peak cylinder pressure as the piston rings and bearings can be made with less friction. This paper presents studies of a combustion engine which consists of a two stage compression and expansion cycle. By splitting the engine into two different cycles, high-pressure (HP) and low-pressure (LP) cycles respectively, it is possible to reach high levels of both indicated and mechanical efficiency simultaneously. The HP cycle is designed similar to today's turbo-charged diesel engine but with an even higher boost pressure, resulting in high PCP. To cope with high PCP, the engine needs to be rigid. The usage of higher piston ring tension and larger bearings are examples of measures to cope with higher PCP. These measures will cost in terms of friction. Hence, mechanical efficiency is not as good as other engine concepts with lower PCP. The low-pressure cycle on the other hand, uses a design more similar to current naturally aspirated (NA) spark ignited (SI) engines, but designed for even lower PCP. Because of this, the engine does not need to be as rigidly designed and the overall friction levels will be much lower. By combining these two engine philosophies, a total engine concept with both high indicated and mechanical efficiencies can be achieved. Simulations show net indicated efficiency above 60% and a brake efficiency of 56%. (Less)

Optimisation of boosting strategy for controlled auto-ignition combustion in a four-valve camless gasoline direct injection engine running in two-stroke cycle

Due to their ability to simultaneously reduce fuel consumption and NOx emissions, controlled autoignition or homogeneous charge compression ignition combustion processes have been extensively researched over the last decade and adopted on prototype gasoline engines. Despite the fact that they were initially achieved on conventional two-stroke ported gasoline engines, there have been much fewer studies carried out on controlled autoignition combustion in two-stroke engines because of the inherent problems associated with the conventional two-stroke engine with intake and exhaust ports. In the meantime, engine downsizing has been actively researched and developed as an effective means to improve the vehicle’s fuel economy by operating the engine at higher load and more efficient regions and by reducing the number of cylinders. But the aggressive engine downsizing of the current four-stroke gasoline engine is limited by the knocking combustion and high peak cylinder pressure. As an alternative approach to engine downsizing, the boosted two-stroke cycle in a poppet valve engine is proposed and researched. It has been shown that the controlled autoignition combustion in the two-stroke cycle could be readily achieved and it led to significant reduction in carbon monoxide and unburned hydrocarbon emissions than the spark ignition combustion. In this study, extensive engine experiments have been performed to determine the optimum boosting for minimum fuel consumption in a single-cylinder gasoline direct injection camless engine operating in the two-stroke cycle. In order to minimise the air short-circuiting rate, the intake and exhaust valve timings were adjusted. Lean boost was applied to the engine operation, which was found to extend the range of controlled autoignition combustion, result in higher combustion and thermal efficiencies and significantly lower carbon monoxide and hydrocarbon emissions. By means of the cycle-resolved in-cylinder measurements and heat release analysis, the improvement in combustion and thermal efficiencies was attributed to the improved in-cylinder mixture, optimised autoignition and combustion phases.

Experimental investigation on a diesel engine fueled with bio-oil derived from waste wood–biodiesel emulsions

This paper describes the use of bio-oil derived from the pyrolysis of waste wood in a single cylinder, air cooled, direct injection (DI), diesel engine developing power of 4.4 kW at 1500 rpm used in agricultural and standby applications. The combustion, performance and emission characteristics of the diesel engine fueled with three different emulsions made from wood pyrolysis oil (WPO) and Jatropha methyl ester (JME) are compared with those of JME and diesel operations. The WPO of 5%, 10% and 15% by volume is emulsified with 95%, 90% and 85% by volume of JME, denoted as X1JOE5, X1JOE10 and X1JOE15 respectively. The combustion of JME, X1JOE5, X1JOE10 and X1JOE15 starts earlier by 2.6 °CA, 2.3 °CA, 2.8 °CA and 2 °CA respectively compared to that of diesel at load. Shorter ignition delay and higher peak cylinder pressure are observed with JME and its emulsions with WPO. There is a significant reduction in the nitric oxide (NO) emissions by 2.5% when fueled with X1JOE15. The smoke opacity decreases by 25%, 26.7%, 22.1% and 18.2% for JME and its emulsions with WPO respectively, in comparison with diesel at full load.

Performance, emission and combustion characteristics of an indirect injection (IDI) multi-cylinder compression ignition (CI) engine operating on neat jatropha and karanj oils preheated by jacket water

Renewable non-edible plant oils such as jatropha and karanj have potential to substitute fossil diesel fuels in CI engines. A multi-cylinder water cooled IDI type CI engine has been tested with jatropha and karanj oils and comparisons made against fossil diesel. The physical and chemical properties of the three fuels were measured to investigate the suitability of jatropha and karanj oils as fuels for CI engines. The engine cooling water circuit and fuel supply systems were modified such that hot jacket water preheated the neat plant oil prior to injection. Between jatropha and karanj there was little difference in the performance, emission and combustion results. Compared to fossil diesel, the brake specific fuel consumption on volume basis was around 3% higher for the plant oils and the brake thermal efficiency was almost similar. Jatropha and karanj operation resulted in higher CO2 and NOx emissions by 7% and 8% respectively, as compared to diesel. The cylinder gas pressure diagram showed stable engine operation with both plant oils. At full load, the plant oils gave around 3% higher peak cylinder pressure than fossil diesel. With the plant oils, cumulative heat release was smaller at low load and almost similar at full load, compared to diesel. At full load, the plant oils exhibited 5% shorter combustion duration. The study concludes that the IDI type CI engine can be efficiently operated with neat jatropha (or karanj) oil preheated by jacket water, after small modifications of the engine cooling and fuel supply circuits.

Experimental study on the performance of and emissions from a low-speed light-duty diesel engine fueled with n-butanol–diesel and isobutanol–diesel blends

The effects of isobutanol- and n-butanol-enriched diesel fuel on the diesel engine performance and emissions are investigated. Neat diesel, 15% isobutanol–85% diesel, 30% isobutanol–70% diesel, 15% n-butanol–85% diesel, and 30% n-butanol–70% diesel blends are investigated in this study. The tests were carried out at light and medium loads and a fixed low engine speed, and by using various combinations of the exhaust gas recirculation rate and the injection timing to investigate the effect of the molecular structure difference on soot formation. The results show that n-butanol–diesel blends give a longer ignition delay than isobutanol–diesel blends do. Hence isobutanol has a higher peak cylinder pressure and a higher premixed heat release rate than n-butanol does. Adding butanol (isobutanol and/or n-butanol) to diesel fuel is able to decrease the soot emissions substantially, while the change in the nitrogen oxide emissions varies slightly. Soot emissions from n-butanol–diesel blends are lower than those from isobutanol–diesel blends. Introducing exhaust gas recirculation and retarding the injection timing are effective approaches to decrease the nitrogen oxide emissions. However, a high exhaust gas recirculation rate leads to a loss in the fuel efficiency. The combination of a low exhaust gas recirculation rate, later injection and butanol blends can achieve low-temperature combustion and simultaneously decrease the nitrogen oxide and soot emissions.

Experimental Investigations of Preheated Jatropha Oil Fuelled Direct Injection Compression Ignition Engine—Part 1: Performance, Emission, and Combustion Characteristics

Abstract Vegetable oils demonstrate several problems as fuel for compression ignition engines due to their high viscosity and low volatility characteristics. Viscosity can be brought down by heating or blending them with mineral diesel. In the first part of the present investigations, a novel method of preheating straight vegetable oils with the waste heat of the engine exhaust is presented. Experimental investigations were carried out for combustion, performance, and emission properties of preheated and unhealed jatropha oil in a direct injection engine at different loads at constant engine speed (1500 r/min). Brake specific fuel consumption and exhaust gas temperatures for preheated jatropha oil were found to be higher compared to mineral diesel. Thermal efficiency was lower for preheated jatropha oil compared to mineral diesel. The vegetable oil preheating reduced the CO2, CO, and HC emissions but increased the NOx emissions. Analysis of cylinder pressure rise, heat release rate, and cumulative heat release was carried out. Preheated jatropha oil shows lower combustion delay but slower heat release rate compared to mineral diesel. Combustion duration for both preheated and unheated jatropha oils is higher than mineral diesel, but heating was found to increase the combustion duration of jatropha oil. Maximum in-cylinder pressure was observed for mineral diesel for higher load conditions, but at lower load, relatively higher peak cylinder pressure was obtained with preheated jatropha oil. Detailed combustion analysis suggests that preheated jatropha oil gives identical combustion as that of mineral diesel. Hence, waste heat of exhaust gas can be effectively utilized to preheat the jatropha oil for improving its combustion properties as a diesel engine fuel.