This work evaluates experimentally on a comparative basis the effects of using three customary biofuels on the cyclic variability (irregularity) of combustion and emissions balance in a single-cylinder, light-duty, direct-injection diesel engine run at three loads. Blends of fossil diesel with up to 15% (by volume) ethanol and 24% n-butanol or diethyl ether (DEE) are investigated. Related experimental study including heat release diagrams reported by the authors for these blends in the same engine disclosed the differentiation in performance and emissions of these biofuel blends from running the engine with neat fossil diesel. Given that low ignition quality fuels, as the present biofuels, mainly at high blending ratios may give rise to unstable engine functioning and hence detrimental performance, this work examines on a comparative basis the strength of combustion cycle-to-cycle variations as revealed in the measured cylinder pressure diagrams. The latter are analyzed with respect to maximum pre...

This work examines the effects of diesel fuel oxygenation on the combustion and emissions in a direct injection (DI) diesel engine. This is a predominately computational study, where the influence of the fuel oxygen content at various injection timings and loads is addressed by using an in-house, comprehensive, two-zone model of DI diesel engine combustion, which divides the cylinder contents into a nonburning zone of air and another zone in which fuel is continuously supplied from the injector and burned with entrained air from the air zone. The validity of the model results is assessed favorably against pertinent experimental data, such as cylinder pressure and heat release rate (HRR) diagrams and nitric oxide (NO) and soot emissions generated in this laboratory by conducting tests on an experimental, single-cylinder, DI Hydra (Ricardo/Cussons, Manchester, United Kingdom) diesel engine operated at two different loads and injection timings. Various degrees of oxygenation of conventional diesel fuel and various injection timings were undertaken in the theoretical study at each load. The numerical simulation results provide insight into the local combustion and emissions formation conditions. Numerical modeling determined that cylinder pressures, temperatures, and NO emissions increase, whereas soot emissions decrease with the degree of fuel oxygenation at any load, and also that cylinder pressures, temperatures, and NO emissions decrease, whereas soot emissions increase by retarding the injection timing at any load. These results are used for discussing the implications they have on the behavior of biofuels or diesel fuel blends, where the fuel-bound oxygen and ignition delay (embodied here in the injection timing variable) are the main parameters dictating their behavior. At least for the case of some common biofuels in blends with diesel fuel, it is shown that lower injection timings and higher degrees of biofuel blend oxygenation (inside limiting values) can alleviate the notorious NO–smoke trade-off with respect to a point of lower oxygenation degree lying on a higher injection timing NO–smoke curve (at any constant load).

In the present work, the contemporary exhaust gas treatment systems (EGTS) used for SO_x, PM, and NO_x emission mitigation from shipping are reviewed. Specifically, after-treatment technologies such as wet scrubbers with seawater and freshwater solution with NaOH, hybrid wet scrubbers, wet scrubbers integrated in exhaust gas recirculation (EGR) installations, dry scrubbers, inert gas wet scrubbers and selective catalytic reduction (SCR) systems are analyzed. The operational principles and the construction specifications, the performance characteristics and the investment and operation of the reviewed shipping EGTS are thoroughly elaborated. The SCR technology is comparatively evaluated with alternative techniques such as LNG, internal engine modifications (IEM), direct water injection (DWI) and humid air motor (HAM) to assess the individual NO_x emission reduction potential of each technology. Detailed real data for the time several cargo vessels spent in shipyards for seawater scrubber installation, and actual data for the purchase cost and the installation cost of seawater scrubbers in shipyards are demonstrated. From the examination of the constructional, operational, environmental and economic parameters of the examined EGTS, it can be concluded that the most effective SO_x emission abatement system is the closed-loop wet scrubbers with NaOH solution which can practically eliminate ship SO_x emissions, whereas the most effective NO_x emission mitigation system is the SCR which cannot only offer compliance of a vessel with the IMO Tier III limits but can also practically eliminate ship NO_x emissions.

Various solutions have been proposed for reducing the exhaust emissions and improve the well-known soot and nitrogen oxide (NO) trade-off in diesel engines, without making serious modifications to the engine, one of which is the use of natural gas as supplement to liquid diesel fuel. In these types of engines, referred to as fumigated, natural gas–diesel dual-fuel compression ignition (CI) engines, gaseous fuel is fumigated and premixed with the aspirated air during the induction stroke. Natural gas is a clean-burning fuel with a relatively high auto-ignition temperature, which is a serious advantage in dual-fuel combustion. Previous research studies have shown that the natural gas–diesel fuel dual-fuel combustion in a CI engine environment, compared with conventional diesel fuel operation, suffers from high specific fuel consumption and high carbon monoxide (CO) and unburned hydrocarbon (HC) emissions. Compression ratio (CR) and diesel fuel injection timing (IT) are two engine parameters that can...

Much research is ongoing to find suitable alternate fuels in order to reduce the exhaust emission levels without deteriorating the basic performance characteristics of conventional spark-ignited (SI) engines. One of the methods to achieve the above problem is the use of alcohols as full supplement fuels to normal gasoline. At the same time, many related research studies have shown that the use of alcohols has a negative impact on some basic engine performance characteristics, e.g., brake power output, etc. On the other hand, spark timing is one of the critical engine operating parameters that significantly influences the combustion mechanism inside the combustion chamber of a SI engine. Therefore, the primary objective of the present work is to investigate the effect of spark timing on the performance and emissions characteristics of a conventional, four-stroke, SI engine running under three different fuel operating modes, viz. with conventional gasoline or ethanol or butanol. The specific investigation is conducted by using an in-house, comprehensive, two-zone phenomenological model. The predictive ability of the model is tested against pertinent experimental data and it is found that the computed results are in good agreement with the respective experimental ones. For all test cases examined herein, the results concern basic engine performance characteristics, i.e., cylinder pressure, power output, specific fuel consumption etc., as well as NO and CO emissions. The main objectives of the work were to record and evaluate the impact that spark timing has on the performance characteristics and emitted pollutants of a conventional SI engine, operating under either conventional gasoline or ethanol or butanol fuel operating modes. Moreover, it deals with the determination of an optimum combination between the type of fuel used and the spark timing, so that probable undesirable effects on engine performance characteristics would be avoided. By comparing this investigation results, it is revealed that the use of alcohols as a full substitute fuel of gasoline accompanied with an appropriate alteration of the spark timing, could be a promising solution to improving both the efficiency and environmental behavior of a light-duty, spark-ignited (SI) engine, without causing any harmful problems to the engine operational lifetime. The conclusions from the study may prove valuable for the application of this technological solution to existing conventional SI engines.