High Cetane Fuels Research Articles

Effects of start of injection and exhaust gas recirculation on dual fuel combustion of isobutanol with diesel and waste cooking oil biodiesel in a diesel engine at higher loads

Dual fuel combustion (DFC) is one of the current emission reduction methods adopted widely for diesel engines. In DFC, high-octane fuels (alcohol) are port injected and high cetane fuels (diesel, biodiesel) are directly injected into the cylinder. However, DFC is reported to increase nitrogen oxides (NOx) compared to conventional combustion mode (CCM) at higher loads. Hence, to mitigate NOx emission in DFC of isobutanol (IB) with diesel, B20, and B100 fuels at higher loads (80 and 100%), the influences of start of injection (SOI) and exhaust gas recirculation (EGR) are investigated. The baseline SOI of DFC fixed at 27°CA before top dead center (bTDC) is retarded to 25, 23, and 21°CA bTDC, and varying EGR (10, 15, and 20%) is implemented at the baseline SOI. Significant NOx reductions of 47.11, 52.53, and 54.45% at the SOI of 21°CA bTDC (at 100% load) and 41.74, 46.38, and 47.81% at 20% EGR (at 80% load) are achieved in the DFC of diesel, B20, and B100 respectively, vis-a-vis their CCM. In DFC of D-IB and B20-IB, retarded SOIs and 10% EGR exhibited better NOx/smoke trade-off than their CCM. Overall, all the DFCs with SOI of 25°CA bTDC as well as 10% EGR is suitable operating conditions compared to CCM.

Ignition delay time measurements of diesel and gasoline blends

Blends of diesel and gasoline can be used to achieve certain desired ignition characteristics in advanced compression ignition engine concepts. In this work, ignition delay times were measured for two blends of diesel and gasoline in two shock tubes and in a rapid compression machine. These blends comprised of 50/50 and 25/75 volumetric% of diesel and gasoline, respectively. To ensure complete vaporization of the blends, the prepared samples were analyzed with nuclear magnetic resonance (NMR) and laser absorption. The analyses revealed full evaporation, and negligible decomposition/oxidation occurred during mixture preparation. Ignition delay measurements covered wide ranges of temperatures (710–1349 K), pressures (10 and 20 bar), and equivalence ratios (0.5, 1.0 and 2.0). The measured ignition delay times of the two dieseline blends are compared with experimental data of low- to mid-octane gasoline and low- to high-cetane fuels. The measured data are also compared with the simulated ignition delay times of primary reference fuel (PRF) and toluene primary reference fuels (TPRF) surrogates. Multi-component surrogates are proposed for the dieseline blends, and the measured ignition delays of the multi-component surrogates and the dieseline blends are in very good agreement.

Experimental studies on performance and emission characteristics of reactivity controlled compression ignition (RCCI) engine operated with gasoline and Thevetia Peruviana biodiesel

Abstract Higher fuel economy associated with lower emissions of diesel engines cannot be achieved with conventional low-pressure injection systems. However high-pressure CRDI facilitated diesel engines with electronic control systems can overcome the twin problems of higher emissions of smoke and nitric oxide with acceptable higher brake thermal efficiency as well. Further use of both high-octane fuels like petrol, ethanol as manifold injected fuels along with high pressure CRDI injected high cetane fuels like diesel, biodiesel can successfully overcome the drawbacks of diesel engine emissions. In this direction a newer concept of RCCI operated modified diesel engine was developed in house and was powered with both high octane and high cetane fuels. Comprehensive experiments were conducted on the RCCI engine to obtain its performance, emission characteristics fueled with selected fuel combinations. From the results for B20 and gasoline operation it was concluded that, injection of 10% gasoline drastically reduces the nitric oxide by 6.67% and soot emission by 4.52% compared to diesel mode. However, there was penalty of high hydrocarbon and carbon monoxide emissions by 12.5% and 7.6% respectively.

Predicting the performance and emission characteristics of a Mahua oil-hydrogen dual fuel engine using artificial neural networks

ABSTRACT The current research work aims at developing the Artificial Neural Network (ANN) model to predict the performance and emission behavior of diesel-powered engine. Conventional diesel engine was converted into dual fuel mode using high octane and high cetane fuels. Several experiments were performed with varying high-octane fuel flow rate and constant flow of high cetane fuel. These data were used for training and testing the ANN model. Feed forward back propagation algorithm was used to predict the performance and emission behavior of dual fuel engine. Engine load, high octane fuel flow rate, fuel injection pressure and fuel injection timing were used as input parameters of ANN model whereas BTE, EGT, HC, CO, NO, and smoke were used as output prediction parameters. The accuracy of the predicted values was determined by means of MSE and Regression coefficient. Finally, the study concludes that there is a credible behavior between ANN predicted values and experimental values for performance and emission behavior of dual fuel engine.

Effect of Late Inlet Valve Closing on NG-Diesel RCCI Combustion in a Heavy Duty Engine

The reactivity controlled compression ignition (RCCI) concept has the potential to make combustion cleaner and more efficient. This paper describes studies on RCCI combustion using natural gas (NG) and diesel as high-octane and high-cetane fuels, respectively. The purpose of this study is to investigate the influence of late inlet valve closing on NG-diesel RCCI combustion. Experimental results reveal that indicated thermal efficiencies over 50% were achieved for most NG-diesel RCCI combustion cases at various inlet valve closing (IVC) timings. RCCI combustion also achieved ultra-low NOx and soot emissions, albeit at the cost of high UHC and CO emissions. Numerical work was also conducted to explore NG-diesel RCCI combustion details.

Experimental Investigation of Natural Gas-Diesel Dual-Fuel RCCI in a Heavy-Duty Engine

Studies have shown that premixed combustion concepts such as PCCI and RCCI can achieve high efficiencies while maintaining low NO x and soot emissions. The RCCI (Reactivity Controlled Compression Ignition) concept use blending port-injected high-octane fuel with early direct injected high-cetane fuel to control auto-ignition. This paper describes studies on RCCI combustion using CNG and diesel as the high-octane and high-cetane fuels, respectively. The test was conducted on a heavy-duty single cylinder engine. The influence of injection timing and duration of the diesel injections was examined at 9 bar BMEP and1200 rpm. In addition, experiments were conducted using two different compression ratios, (14 and 17) with different loads and engine speeds. Results show both low NOx and almost zero soot emissions can be achieved but at the expense of increasing of unburned hydrocarbon emissions which could potentially be removed by catalytic after-treatment. CA50 generally occurred before TDC when using a compression ratio of 17. While the CA50 could be shifted to slightly after TDC by increasing the amount of EGR, this would lead to excessive HC emissions. A lower compression ratio of 14 was therefore used to retard the CA50 while maintaining acceptable UHC emissions.

Computational Analysis of Combustion of High and Low Cetane Fuels in a Compression Ignition Engine

Past research has shown that the combustion of low cetane fuels in compression ignition (CI) engines results in higher fuel conversion efficiencies. However, when high-cetane fuels such as diesel are substituted with low-cetane fuels such as gasoline, the engine operation tends to suffer from high carbon monoxide (CO) emissions at low loads and combustion noise at high loads. In this paper, we present a computational analysis of a light-duty CI engine operating on diesel, kerosene and gasoline. These three fuels cover a range of cetane numbers (CNs) from 46 for diesel to 25 for gasoline. Similar to experiments, the model predicted higher CO emissions at low load operation with gasoline. Predictions of in-cylinder details were utilized to understand differences in combustion characteristics of the three fuels. The in-cylinder mass contours and the evolution of model predicted in-cylinder mixture in Φ–T coordinates were then used to explain the emission trends. From the analysis, overmixing due to early single injection was identified as the reason for high CO emissions with low load gasoline low temperature combustion (LTC). Additional simulations were performed by introducing techniques like cetane enhancement, adding hot exhaust gas recirculation (EGR), and variation of the injection scheme. Their effects on low load gasoline LTC were studied. Finally, it is shown that use of a dual pulse injection scheme with hot EGR helped to reduce the CO emissions for low load gasoline LTC while maintaining low NOx emissions.

Influence of diesel fuel cetane number on operating indices of engine

1. An increase in the cetane number of winter and arctic diesel fuels from 40 (GOST 4749-49) to 45 (GOST 4749-73) leads to a decrease in the dynamic stress of the operating cycle in automotive/tractor engines amounting to at least 30%, so that the time between overhauls can be increased. 2. The use of high-cetane fuels (50 and up) brings about a progressive increase in specific fuel comsumption and in exhaust smoke.