Wide Range Of Engine Loads Research Articles

Widening the operation limits of a SI engine running on neat ammonia

Present study aims to investigate the lean-burn characteristics of ammonia in a pre-mixed SI (Spark Ignition) engine and the influence of spark energy and discharge characteristics on engine performance and emissions. A wide range of engine operation conditions have been explored with particular focus on emission measurement. Engine parameters have been systematically swept to explore engine control strategies that would be operational in real engine application with a wide range of engine loads and tight emission regulations.Most previous studies required more than 5 % addition of hydrogen to the ammonia in order to achieve stable ignition for wide operation conditions. This has been a major obstacle in the application of ammonia for SI engines due to safety and system complexity issues. In present work, a comprehensive effort was made to understand and optimize the spark ignition system in order to mitigate the need for an ignition improver and all experiments have been performed with 100 % neat ammonia.With present engine modifications, emissions of unburned ammonia was measured to be between 5000 and 10000 ppm and with a combustion efficiency above 95 %. The unburned ammonia is believed to originate from crevices, particularly at the ring-pack. The NOx emission was between 4000 and 8000 ppm even at high excess air ratios. The emission of N2O is critical to minimize, as it is a strong greenhouse gas. It was measured to be between 20 and 80 ppm and appear to be related to post oxidation reactions of ammonia released from crevices during expansion.Advancing the ignition timing has proved to be an efficient handle for balancing the emissions of NH3 and NOx. These emissions will be reduced to H2O and N2 in an SCR catalyst if they are correctly balanced. Fortunately, advancing ignition timing also minimizes the formation of N2O.

Combustion and Performance Evaluation of Methanol (M15)-Fueled BS-VI Compliant Light-Duty Spark-Ignition Engine

Abstract This study investigated the effect of the methanol–gasoline blend (M15) on the combustion and performance characteristics of a commercial light-duty Bharat Stage-VI (BS-VI) 2020 spark-ignition (SI) engine. The M15 and baseline gasoline (G100) engine tests were performed at a wide range of engine loads and speeds. For the M15 operation, it was ensured that the lambda values matched with the baseline gasoline operation at each engine operating point by changing fuel quantity manually. The combustion characteristics of M15 were quite similar to gasoline at all operating points. Alcohol addition improves octane number and flame speed, which changes the combustion characteristics of the engine, but in this study, the combustion characteristics of M15 fuel were almost identical. It may be due to blending a small fraction of methanol and the engine's high compression ratio, which improved the combustion kinetics. The coefficient of variance of indicated mean effective pressure was slightly lower for M15 than gasoline, except at 1000 rpm, where the charge mixing might not be adequate at low engine speed for M15 due to lower methanol volatility. Engine's brake thermal efficiency improved with M15 fueling by ∼1%, compared to baseline gasoline, though brake-specific fuel consumption deteriorated by ∼6% due to the lower calorific value of M15. Higher combustion stability and possibly lower heat transfer losses, as observed from slightly higher exhaust gas temperature (EGT), might have improved the engine's performance for M15. This study demonstrated that M15 fueling exhibited identical combustion characteristics and higher thermal efficiency than baseline gasoline fueling at similar lambda values in a commercial light-duty BS-VI SI engine.

Stabilization of Auto-Igniting Flames Within a Gas Turbine Sequential Combustor, Through the Control of Static Temperature Variation—Detailed Numerical Investigation

Abstract Axially staged combustion systems offer both enhanced operability and fuel flexibility for gas turbines, allowing stable operation and low emissions across a wide range of engine loads. The sequential combustion concept, where the first combustion stage is supported by a standard lean premixed flame and the second stage relies on an auto-ignition-dominated flame, forms the focus of the present contribution. Within the present state of the art, the still-oxygen-rich exhaust gases from the first stage are mixed with second stage fuel within a sequential burner. Within the presently investigated concept, the flame is anchored by establishing a positive static temperature gradient within the burner. The advantage of such a concept is that it potentially allows for very small combustor residence times and can be easily incorporated into an integrated combustor–nozzle guide vane. The concept does however present significant challenges, which are investigated within then present contribution. A critical challenge is that, in order to setup the static temperature gradient, the flow has to be accelerated to a relatively high Mach number, ca. 0.7, and then decelerated in a diffusing section where the flame is located. Achieving fuel/air premixing and combustion, while achieving acceptable pressure drops is not trivial at the high velocities. Additionally, the dynamic stability of the concept is not clear and needs to be investigated. Within the present work, compressible computational fluid dynamics (CFD) is used to investigate the pressure drop characteristics within the system. It is demonstrated that for the system a total pressure drop of less than 6% can be achieved. To realize this, the premixing section includes multipoint fuel injection coupled with mixing devices. The arrangement is designed to both limit excessive pressure losses by focusing losses within regions of the flow where they contribute effectively to fuel/air mixing as well as locating the flame where Rayleigh losses are acceptable. The dynamic behavior of the system is studied by way of two-dimensional (2D) fully premixed CFD. Investigation of the flame response to harmonic perturbations in inlet temperature shows that the flame transfer function (FTF) is characterized by amplitude growing, in line with the concept of auto-ignition at low Mach number, linearly with frequency. The rate of growth with frequency of the FTF amplitude is rather high reaching up to 60 times the imposed relative fluctuation of inlet temperature at a frequency of 600 Hz. This rapid growth is in line with the behavior of auto-ignition at low Mach number. A substantial difference with the low Mach number concept is given by upstream traveling acoustic waves generated by the flame that going through high Mach number locations, can affect, in respect of the conservation of entropy transported by convection, the upstream temperature distribution and therefore auto-ignition itself.

Performance, Combustion, and Emission Evaluation of Ethanol-Gasoline Blends Ignited by Diesel in Dual-Fuel Intelligent Charge Compression Ignition (ICCI) Engine

Abstract A recent proposed dual-fuel combustion mode, intelligent charge compression ignition (ICCI), realizes the high-efficiency and clean combustion by organizing continuous stratification in a wide range of engine load. The paper investigated the performance of alcohol blended gasoline as low-reactivity fuel (LRF) in ICCI combustion mode. Pure ethanol named E100 was also tested as LRF for comparison. To emphasize the differences of LRF properties and exclude the effect of the heat release phasing, the diesel injection timing was adjusted to maintain the same combustion phasing (CA50) at various LRF ratios under medium load. The results showed that E100 and E85 (ethanol ratio in gasoline-ethanol blend) promoted the degree of homogeneous combustion and eradicated soot emissions despite a slight increase of NOx. The maximum indicated thermal efficiency (ITE) was over 51.1% using E85, followed by 50.5% of E50. The perfect substitution ratio at the maximum ITE decreased from more than 80% to about 65% when increasing the ethanol ratio in LRF from 10% to 100%. The unregulated emissions such as aldehydes, ethylene, and methane, produced from incomplete combustion of ethanol were inhabited by E85, while the formation of toluene attributed to the appropriate carbon chain length of gasoline diminished when using E85 and E100.

Zero-dimensional turbulence modeling of a spark ignition engine in a Miller cycle « Dethrottling » approach using a variable valve timing system

• A complete 0D model with in-cylinder aerodynamic prediction and turbulent combustion is proposed. • Analytical calculation of quantities reduces the cost and time of the predictions. • The effect of a VVT system on the performance of an EIVC Miller cycle engine is investigated. • Reduction in pumping losses results in benefits of up to 1% over a wide range of engine loads. The Miller cycle, using an early inlet valve closing, can significantly improve the overall efficiency of a spark ignition engine during partial load operations. The shorter valve intake event minimizes the need for throttling the air and so reduces the pumping losses. This method is known as “dethrottling”. Indeed, the use of a variable valve lift system makes it possible to combine two different cam profiles in an engine, one for the full load operations and one for the partial loads. The benefits of this strategy, combined with a variable valve timing (VVT) system, will be explored using a new 0D model. This model can take into account the strong changes of in-cylinder turbulence generated by the VVT and their effects on the combustion. Efforts have been made to reduce the model's reliance on external inputs. Therefore, analytical calculations of quantities, such as the flame radius, have been favored. The Miller cycle can lead to indicated efficiencies around 44% and the addition of a VVT system can improve the overall efficiency up to 1% over a wide range of engine loads.

Effect of Utilizing a Novel Intake Manifold Design on Smoke Emissions and Particulate Size Distributions of a Gas-to-Liquid (GTL) Diesel Engine

Abstract Smoke emissions and particulate matter (PM) size distributions were investigated on a direct-injection single-cylinder diesel engine running on both gas-to-liquid (GTL) and diesel fuels utilizing a novel spiral-helical intake manifold design. Smoke opacity was measured at a wide range of engine loads and speeds with both fuels to examine the effect of using the new manifold on smoke emissions. In addition, total PM numbers of fine particles (PM diameter = 1.0 µm) and coarse particles (>1.0 µm) were quantified with both fuels. Moreover, high-resolution transmission electron microscopy (HRTEM) images were taken with different resolutions to observe the PM sizes produced from each fuel when using the new and normal manifolds. The results showed that using the novel manifold reduced smoke emissions for both GTL and diesel fuels with about 36% at low loads and 7% at high loads. However, using the new manifold with GTL fuel showed superior performance to reduce smoke with about 60% at low loads and 10% at high loads. For the PM size distribution, the new manifold reduced total PM emissions in general. However, significant reductions were obtained with fine PM sizes (0.3 – 1.0 µm) when GTL fuel was used with about 30% for constant load tests, and about 40% for constant speed tests. On the other hand, the new manifold tended to increase slightly the coarse PM sizes. The HRTEM images of the PM structure for both manifolds and fuels have confirmed the above results.

Experimental study on wide load operation of gasoline compression ignition engine: Real distillate gasoline versus primary reference fuel

This paper aims to achieve high efficiency, low emissions and stable gasoline compression ignition (GCI) combustion over a wide range of engine loads. The real distillate gasoline fuels with research octane number (RON) of 83 and 72, denoted as G80 and G70, were applied to investigate the GCI combustion and emissions. To break through the limitation of injection pressure on engine load, the port injection combined with direct injection (PIDI) mode was studied for indicated mean effective pressure (IMEP) from 10 bar to 13 bar. The combustion and emission characteristics of primary reference fuels (PRF) with RON of 80 and 70 were also tested for comparison. The results indicate that high net indicated thermal efficiency (ITEnet) are obtained in a wide range of engine loads for GCI modes, especially the ITEnet of G70 is up to 51%. Compared with the PRFs, the low-RON gasoline fuels possess lower fuel consumption as well as lower THC and CO emissions, but higher NOx emissions. The low-RON gasoline fuels also produce more particle emissions than the PRFs under medium–high loads. Compared with DI mode, the PRRmax, particle emissions are improved in PIDI mode. However, the ITEnet, CO and THC emissions are deteriorated.

Statistical and experimental investigation of single fuel reactivity controlled compression ignition combustion on a non-road diesel engine

In the present work, an attempt is made to implement the single fuel RCCI combustion on a non-road diesel engine using oxygenated renewable non-fossil fuel. In this study, isobutanol (high octane fuel − low reactivity fuel)/isobutanol-polyoxymethylene dimethyl ether blend (medium Cetane fuel − medium reactivity fuel) based reactivity controlled compression ignition combustion has been investigated on a modified single cylinder non-road diesel engine to control its engine out emissions and to improve the brake thermal efficiency. Various operating parameters have been optimized for a wide range of engine loads (i.e. from 1.3 bar BMEP to 3.9 bar BMEP) using response surface methodology and statistical significance of the used models have been recognized by analysis of variance. Then, numerical optimization has been performed using the desirability approach of response surface methodology. The predicted solutions are validated by engine experiments. Design of experiments approach saved many experimental trials and helped in understanding the effects of various operating parameters such as PODE energy ratio, the start of injection of a pilot and main fuel, fuel injection pressure of medium reactivity fuel, pilot injection mass, intake air temperature, and EGR on combustion, performance and emission characteristics. The predicted and actual experimental results show that a maximum 97% reduction in soot emission and 83% reduction in NO emission was achieved in single fuel RCCI combustion compared to conventional diesel combustion along with a 10.4% percentage increase in brake thermal efficiency.

Comparison of four butanol isomers blended with diesel on particulate matter emissions in a common rail diesel engine

As a renewable fuel, butanol has a higher energy density than short-chain alcohols, and can be mixed with diesel in any proportion. To analyze the particulate matter emissions of butanol isomer in compression ignition engines, in this paper, the four butanol isomers were blended with diesel (25 vol%) named as n-butanol/diesel, s-butanol/diesel, i-butanol/diesel and t-butanol/diesel. The characteristics of particulate matter emissions were studied under a wide range of engine loads (3bar–9bar) and exhaust gas recirculation (EGR) rates (0%–60%). The results revealed that for all tested fuels as indicated mean effective pressure (IMEP) increased, particulate matter emissions first decreased and then increased. Compared to diesel under low load condition (IMEP = 3bar), the blending of butanol isomers had limited effect on particulate matter emissions. Among them, t-butanol increased the peak of particulate size distribution. When the engine load is higher than IMEP of 6 bar, the blending of butanol isomer significantly improved the particulate matter emissions. For IMEP fixed at 8bar, increasing the EGR rate made the particulate matter increase, especially for direct injection diesel. Butanol isomer/diesel blends can achieve low NOx and significantly improves particulate matter emissions in low temperature combustion mode (EGR = 60%). When EGR rates higher than 30%, the butanol isomer/diesel blends had a much smaller GMD than neat diesel. A comprehensive investigation of the four butanol isomer/diesel blends showed that t-butanol always had the highest particles than other butanol isomers under different EGR rates.

The Impact of a Place for the Measurement of Cylinder Pressure of Marine Piston Engine on the Indicator Diagrams and Indicator Parameters

Abstract The article discusses one of the most popular methods of diagnosing selected damages of marine piston engines, which is the indication or measurement of pressure changes in the engine’s combustion chamber. Improving the quality of indicator diagrams may contribute to the increase in the efficiency of using the parameters indicated in the diagnostics of marine piston engines. Measurement errors during engine indication are primarily caused by measuring channels that connect the combustion chamber to the pressure sensor. One way to avoid these errors is to install the pressure sensor directly in the combustion chamber. It seems that it is possible to eliminate these errors. However, there is a risk that the pressure sensor will be damaged by the effect of high temperature on it during combustion of the fuel-air mixture in the engine’s combustion chamber. The article presents the results of tests that indicate that the measured temperatures in the place where the sensor was installed (in the combustion chamber) did not exceed the critical value specified by the pressure sensor manufacturer. The article also presents the results of cylinder pressure measurement not only in the combustion chamber but also in two other points - on the thread of the indicator cock and in the measuring channel between the indicator cock and the cylinder head. The tests were carried out in a wide range of engine load technically efficient and with simulated damage in the fuel injection system. The article presents a comparative analysis of the parameters read out of the indicator diagram for the three above-mentioned pressure measurement locations. It was shown that the pressure measurements carried out directly in the combustion chamber are free from errors resulting from the influence of measuring channels and indicator cock.

Design of a decision support methodology using response surface for torque comparison: An empirical study on an engine fueled with waste plastic pyrolysis oil

Current energy and environmental situations have been driving the development of new alternative energies, especially in transportation sector. The objective of this research is to present a decision support methodology to compare engine torques between using the average value and the new approach called response surface. This research investigates the engine torques from neat diesel fuel (WPO (waste plastic pyrolysis oil) 0%) and blend 25% of waste plastic pyrolysis oil by volume in diesel (WPO 25%) at wide range of engine load (20%, 40%, 60%, and 100%) and speed (800 rpm, 1200 rpm, 1500 rpm, 1800 rpm, and 2000 rpm). A heavy-duty multi-cylinder diesel engine was installed on an engine dynamometer and the torque data were recorded. The contribution of this research is to present a more accurate methodology to perform an engine torque comparison. The value of this research lies in the development of a new approach, which is applicable to decision makers in obtaining an engine torque comparison. Consequently, the benefit of the research is that the empirical data from a heavy-duty diesel engine fueled with waste plastic oil blends are revealed. The number of experimentations can be reduced and this leads to lower costs and less time usage for future research.

RESEARCH ON INFLUENCE OF SELECTED CONTROL PARAMETERS OF THE INJECTION SYSTEM MARINE DIESEL ENGINE ON ITS EXHAUST GAS TOXICITY

This paper devoted to pollution of the atmosphere due marine diesel engines in operation. In the paper presented are results of the investigations carried out in the Gdynia Maritime Academy laboratory with the use of a ship diesel engine, one-cylinder, two-stroke, crosshead of longitudinal scavenging, which was loaded by means of the water brake. This diesel engine combusting heavy fuel oil IF 40. The test-involved effect of two selected control parameters of fuel injection system ship diesel engine: fuel injection pressure and injection advance angle. Both selected control parameters were changed during the experiment separately, each of them three times. And so: changing the fuel injection pressure – for three selected values: 18, 22 and 26 MPa; changing the fuel injection advance angle – for three selected values: –10°, –13° and –16° before the piston’s top dead centre (BTDC). The measurements were performed within the wide range of engine load at the permanent rotational speed of 220 rpm. For each of the above selected values six measurements were performed at the following engine loads: 25%, 40%, 50%, 60%, 70% and 80% nominal loads. Control parameters to change the injection pump and injector engine, during operation of the engine, by means of a supplementary-scaled instrumentation of the injector and injection pump. Owing to this is was not necessary to stop the engine before each successive test cycle. This way of realization of the measurements guaranteed running them in steady conditions. The elimination of influence of possible disturbances witch could arise from multiple starting and stopping the engine improved accuracy and reliability of the obtained results.

Electronically controlled viscous cooling fan clutch in the vehicle

This paper presents on the development of an electronically controlled viscous cooling fan clutch actuator. Improvement in energy efficiency has been achieved by automation of the engine control system and enhancement of engine cooling systems. The engine cooling system uses On/Off viscous cooling fans that are applicable to wide range of engine loads with efficient energy consumptions. Depending on the temperature of the engine and the PWM signals, the power input and speed of the cooling fan automatically controlled by engine management system (EMS). Test results on the fan speed control according to the engine temperature are given in this paper.

Fuel reactivity controlled compression ignition (RCCI): a pathway to controlled high-efficiency clean combustion

A fuel reactivity controlled compression ignition (RCCI) concept is demonstrated as a promising method to achieve high efficiency – clean combustion. Engine experiments were performed in a heavy-duty test engine over a range of loads. Additionally, RCCI engine experiments were compared to conventional diesel engine experiments. Detailed computational fluid dynamics modelling was then used to explain the experimentally observed trends. Specifically, it was found that RCCI combustion is capable of operating over a wide range of engine loads with near zero levels of NO x and soot, acceptable pressure rise rate and ringing intensity, and very high indicated efficiency. For example, a peak gross indicated efficiency of 56 per cent was observed at 9.3 bar indicated mean effective pressure and 1300 rev/min. The comparison between RCCI and conventional diesel showed a reduction in NO x by three orders of magnitude, a reduction in soot by a factor of six, and an increase in gross indicated efficiency of 16.4 per cent (i.e. 7.9 per cent more of the fuel energy was converted to useful work). The simulation results showed that the improvement in fuel conversion efficiency was due both to reductions in heat transfer losses and improved control over the start- and end-of-combustion.

Performance and emission characteristics of a CI engine operated with n-Butane blended DME fuel

In this study, a compression ignition (CI) engine operated with n-Butane blended di-methyl ether (DME) fuel was experimentally investigated. Specifically, the performance, emissions characteristics, and combustion stability of a CI engine fueled with n-Butane blended DME fuel were examined at 1500 rpm. All the experimental results were compared to the results of diesel fuel with the same experimental conditions. The percentage of n-Butane in the fuel blend ranged from 0 to 40% by mass. The results showed that stable engine operation was possible for a wide range of engine loads up to 30% n-Butane by mass. The engine power output and fuel consumption were improved with the blended fuel since the energy content of n-Butane is much higher than that of DME. Exhaust emission measurements showed that when the blended fuels at low engine loads were used, hydrocarbon and CO emissions increased due to partial burn from over-mixing. Soot and NOx emissions were comparable for all blends. Our results on engine power output and exhaust emissions demonstrate that blended fuels up to 30% n-Butane by mass can be used as an alternative to diesel in a CI engine, and n-Butane blended DME fuel has the potential to enlarge the DME market.

Effect of n-Butane and propane on performance and emission characteristics of an SI engine operated with DME-blended LPG fuel

In this study, a spark ignition engine operated with DME-blended LPG fuel was studied experimentally. In particular, the effect of n-Butane and propane on performance, emissions characteristics (including hydrocarbon, CO, and NOx), and the combustion stability of an SI engine fuelled with DME-blended LPG fuel were examined. Four kinds of test fuel with different blend ratios of n-Butane, propane, and DME were used. The percentage of DME in the fuel blend was 20% by mass.The results showed that stable engine operation was possible for a wide range of engine loads with propane containing LPG/DME-blended fuel rather than n-Butane containing LPG/DME-blended fuel since the octane number of propane is higher than that of n-Butane. Also, engine power output, break specific fuel consumption (BSFC), and combustion stability when operating with propane containing DME-blended fuel were comparable to those values in case of pure LPG fuel operation. Engine power output was decreased and BSFC was increased with n-Butane containing DME-blended fuel due to the lower energy density of DME. To examine the effect of n-Butane and propane on emissions and fuel economy in an actual vehicle, a vehicle was tested during an FTP-75 cycle. Through the emission and fuel economy test in the FTP-75 cycle, we conclude that the differences in emission level and fuel economy were not significant according to the blend of n-Butane, propane, and DME.Considering the experimental results from the engine bench and the actual vehicle, the 20% content of DME-blended fuel, regardless of LPG type, can be used as an alternative fuel for LPG.

Comprehensive study of biodiesel fuel for HSDI engines in conventional and low temperature combustion conditions

In this research, an experimental investigation has been performed to give insight into the potential of biodiesel as an alternative fuel for High Speed Direct Injection (HSDI) diesel engines. The scope of this work has been broadened by comparing the combustion characteristics of diesel and biodiesel fuels in a wide range of engine loads and EGR conditions, including the high EGR rates expected for future diesel engines operating in the low temperature combustion (LTC) regime. The experimental work has been carried out in a single-cylinder engine running alternatively with diesel and biodiesel fuels. Conventional diesel fuel and neat biodiesel have been compared in terms of their combustion performance through a new methodology designed for isolating the actual effects of each fuel on diesel combustion, aside from their intrinsic differences in chemical composition. The analysis of the results has been sequentially divided into two progressive and complementary steps. Initially, the overall combustion performance of each fuel has been critically evaluated based on a set of parameters used as tracers of the combustion quality, such as the combustion duration or the indicated efficiency. With the knowledge obtained from this previous overview, the analysis focuses on the detailed influence of biodiesel on the different diesel combustion stages known ignition delay, premixed combustion and mixing controlled combustion, considering also the impact on CO and UHC pollutant emissions. The results of this research explain why the biodiesel fuel accelerates the diesel combustion process in all engine loads and EGR rates, even in those corresponding with LTC conditions, increasing its possibilities as alternative fuel for future DI diesel engines.

Performance and emission characteristics of an SI engine operated with DME blended LPG fuel

In this study, a spark ignition engine operated with DME blended LPG fuel was experimentally investigated. In particular, performance, emissions characteristics (including hydrocarbon, CO, and NO x emissions), and combustion stability of an SI engine fuelled with DME blended LPG fuel were examined at 1800 and 3600 rpm. Results showed that stable engine operation was possible for a wide range of engine loads up to 20% by mass DME fuel. Further, we demonstrated that, up to 10% DME, output engine power was comparable to that of pure LPG fuel. Exhaust emissions measurements showed that hydrocarbon and NO x emissions were slightly increased when using the blended fuel at low engine speeds. However, engine power output was decreased and break specific fuel consumption (BSFC) severely deteriorated with the blended fuel since the energy content of DME is much lower than that of LPG. Furthermore, due to the high cetane number of DME fuel, knocking was significantly increased with DME. Considering the results of the engine power output and exhaust emissions, blended fuel up to 10% DME by mass can be used as an alternative to LPG, and DME blended LPG fuel is expected to have potential for enlarging the DME market.

An experimental study of Pongamia pinnata L. oil as a diesel substitute

Present work deals with testing a performance of a compression ignition (CI) engine with different blends of non-edible oil as well as their methylesters with petrodiesel. Various blends of a non-edible vegetable oil, commonly known as honge ( Pongamia pinnata L.) in India, were prepared and tested over a wide range of engine load. Results obtained from the study showed that 15–20 per cent pongamia methylester-diesel blend (B15 and B20) could be a better fuel in terms of fuel efficiency and power developed. Further, the blend can be used in any existing CI engine without modification and preheating. The pongamia oil is transesterified by using base catalysed transesterification process in a batch type transesterification reactor. Transesterification shows improvement in fuel properties of pongamia oil. Results obtained with B15 and B20 show improvement in brake thermal efficiency and reduction in brake specific fuel consumption, especially at higher load. Emission results show significant reduction in percentage of CO and HC for B15 and B20 at medium and higher power output.

Two-photon nitric oxide laser-induced fluorescence measurements in a diesel engine

A two-photon nitric oxide (NO) laser-induced fluorescence (LIF) technique was developed and applied to study in-cylinder diesel combustion. The technique prevents many problems associated with in-cylinder, single-photon NO planar-laser-induced fluorescence measurements, including fluorescence interference from the Schumann-Runge bands of hot O2, absorption of a UV excitation beam by in-cylinder gases, and difficulty in rejecting scattered laser light while simultaneously attempting to maximize fluorescence signal collection. Verification that the signal resulted from NO was provided by tuning of the laser to a vibrational off-resonance wavelength that showed near-zero signal levels, which resulted from either fluorescence or interference at in-cylinder pressures of as much as 20 bar. The two-photon NO LIF signal showed good qualitative agreement with NO exhaust-gas measurements obtained over a wide range of engine loads.