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The present work discusses the influence of injection schedules in hydrogen diesel homogeneous charge compression ignition (HDHCCI) mode, the experiments were carried out in three distinct diesel injection schedules like single pulse, double pulse and multi-pulse at low load operation. The maximum reachable hydrogen energy shares (HES) are 27.46%, 26.97% and 39.96% for a single pulse, double pulse and multi-pulse respectively. For almost all HES levels, the single pulse and double pulse HDHCCI mode provided ultra-low NO emission when compared with hydrogen diesel dual fuel (HDDF) mode. The multi-pulse injection increased the brake thermal efficiency (BTE) compared with single pulse and double pulse injection, since the timing of injection pulse 3 (IP3) in multi-pulse significantly altered the combustion characteristics of HDHCCI mode. Locating the IP3 in the window of 30–40 °BTDC (before cool flame) enhanced the BTE and reduced the brake specific energy consumption (BSEC) of the engine. Image 1 • Injection schedule influence the hydrogen diesel HCCI (HDHCCI) mode. • Single pulse HDHCCI mode provides ultra-low NO emission for entire HES levels. • No significant change in performance of HDHCCI with double pulse injection. • Multi-pulse HDHCCI mode recovers the combustion and increases the HES level. • Multi-pulse enhances the performance of HDHCCI mode and reach near to HDDF mode. [ABSTRACT FROM AUTHOR]

In the present paper, laboratory produced, animal origin biofuels (swine lard and turkey lard had been used as raw material for biofuel production) were evaluated in terms of physicochemical parameters and compared with commercial mineral diesel fuel and its mixture with rapeseed oil methyl esters. Basing on the results of physicochemical parameters assessment, mixtures containing 75% share of bio-component were preselected for further engine tests. The engine tests were performed on a medium-duty, turbocharged, Common Rail, Direct Injection (CRDI) diesel engine, using factory control maps. The scope of experiments included steady state measurements for two rotational speeds (1500 and 3000 RPM), for which full load sweep had been performed. Two injection strategies were utilized: single pulse (for 3000 RPM) and multi-pulse injection (1500 RPM). The research covered evaluation of engine performance parameters and full exhaust emissions. Furthermore, detailed combustion analysis was performed. The study confirmed that high quality fuel can obtained from waste fatty material. The mixtures containing up to 75% of bio-component are suitable for modern CRDI combustion engines, though slight deterioration of engine performance parameters can be expected. An average brake specific fuel consumption increased by 13% compared to reference, for biodiesel mixtures derived from animal fatty material. At the same time a 3% increase against rapeseed oil/diesel mixture was recorded. This was correlated with a minor reduction of brake fuel conversion efficiency, but the average drop didn’t exceed 2% for all examined biodiesels. A significant reduction in exhaust gas emissions was observed, when comparing biofuel operation to reference diesel. The use of swine lard methyl ester/diesel mixture caused average reduction of hydrocarbon concentration (THC) by 13%, carbon monoxide (CO) by 22% and carbon dioxide (CO 2 ) by 7%. The turkey biodiesel emission results were respectively: 9%, 20% and 6% reduced. NOx emission increased on average by 7% for both animal origin biofuels. [ABSTRACT FROM AUTHOR]

The distributions of fuel concentration and temperature have significant effect on the ignition processes of diesel premixed charge compression ignition (PCCI) combustion. It was found in this study that the ignition process of PCCI combustion organized by multi-pulse injection was strongly inuenced by conditions of fuel stratification. The start of low temperature reactions occurred in the leaner area of the combustion chamber in the test engine because the temperature here first reached the point of low temperature reactions. Ignition always occurred in the position where the mixture featured with equivalence ratios close to the mean equivalence ratio of the overall mixture, while the neighboring area of the initial ignition area accumulate heat with a finite speed until finally autoigniting. Moreover, the appearance of highest combustion temperature occurred in the same area at the combustion chamber. For more homogeneous mixture, a higher amount of mixture reached ignition simultaneously, resulting in a larger initial ignition area and a higher temperature at the ignition area. Furthermore, V-type distribution of equivalence ratio was found to be beneficial to retarding high temperature reaction. [ABSTRACT FROM AUTHOR]

• High CN of HVO provides tolerance to heavy exhaust gas recirculation. • PPCI air-path control can be optimised without impacting combustion phasing. • HVO has 1.5 percentage points higher indicated efficiency (43.5 %) than diesel. • Air-path parameters-optimised HVO cuts all emissions with ultra-low particulates. Hydrotreated vegetable oil (HVO) has potential to emerge as an alternative fuel to mineral diesel due to its favourable properties. The present study investigated HVO under partially premixed compression ignition combustion mode with boost-exhaust gas recirculation (EGR) and also in conventional combustion mode. Single-cylinder engine tests focused on optimising a single representative operating point in the middle of the engine operating envelope. The optimisation focused on the trade-off between NO X and particulate matter, as the adopted multi-pulse strategy provides stable combustion onset independently of the cylinder mixture conditions. Sensitivity in emissions comes from large differences in the early, premixed combustion phase. Air-path optimized HVO combustion favours higher EGR rates (25 % vs. 20 %) and lower boost pressures than diesel (130 kPa vs 165 kPa). At such conditions HVO has 1.5 percentage points higher indicated thermal efficiency (43.5 %) than diesel. At the same time, HVO yields an ultra-low particulate level (0.055 g/kWh) and engine-out NO X emissions are 46 % better than optimised diesel combustion. Together with a 37 % reduction in total hydrocarbon emissions, the elimination of aromatics also provides an additional incentive for HVO. [ABSTRACT FROM AUTHOR]