The progress in wave energy conversion in Europe during the past ten years is reviewed and current activities and initiatives in the wave energy sector at National and Union level are described. Other important activities worldwide are summarized. The technical and econ

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Wave energy in Europe: current status and perspectives

Soot processes in compression ignition engines

Biofuels have grabbed the attention of engine researchers ever since the oil-crisis and escalating costs of petro-chemicals cropped up in the ׳70s. Ethanol and methanol were the most widely researched alcohols in IC engines. However, the last decade has witnessed significant amount of research in higher alcohols due to the development of modern fermentation processes using engineered micro-organisms that improved yield. Higher alcohols are attractive second/third generation biofuels that can be produced from sugary, starchy and ligno-cellulosic biomass feedstocks using sustainable pathways. The present work reviews the current literature concerning the effects of using higher alcohols ranging from 3-carbon propanol to 20-carbon phytol on combustion, performance and emission characteristics of a wide range of diesel engines under various test conditions. The literature is abound with evidence that higher alcohols reduce carcinogenic particulate emissions that are prevalent in diesel engines. NOx emissions either increased or decreased based on the domination of either cetane number or heat of evaporation. Brake specific fuel consumption (BSFC) of the engine usually suffered due to low energy content of alcohols. A notable feature is that the combination of higher alcohols (like butanol or pentanol), high exhaust gas recirculation (EGR) rates and late injection timing enabled low temperature combustion (LTC) in diesel engines that can simultaneously reduce smoke and NOx emissions with improved engine efficiency. It can be concluded that higher alcohols reduce smoke emissions with their fuel-borne oxygen; enhance air/fuel mixing by offering long ignition delay and eventually replace fossil diesel (partially or wholly) to enable a clean and efficient combustion in compression-ignition engines. The chief thrust areas include developing mutant strains with higher yield, higher tolerance to toxic inhibition and low-cost substrates for fermentation. Further work is required in stipulating optimum blend-fuel characteristics and ensuring the long-term durability of the engines using these fuels.

Use of higher alcohol biofuels in diesel engines: A review

Challenges and opportunities in improving the production of bio-ethanol

Emission characteristics of high speed, dual fuel, compression ignition engine operating in a wide range of natural gas/diesel fuel proportions

Remarkable improvement of NOx–PM trade-off in a diesel engine by means of bioethanol and EGR

Prediction of NOx Reduction Rate Due to Port Water Injection in a DI Diesel Engine

For reducing the exhaust emissions and improving the ignition characteristics, the effect of pilot injection was investigated experimentally in a turbocharged direct injection diesel engine. The pilot injection quantity was varied by changing the seat diameter of the Doge plunger installed in the newly developed pilot injector while the separation period between the beginning of pilot injection and that of main injection was fixed at a short interval in the present experiment. The pilot injection effect on combustion was compared with the case of normal injection in two fuel oils with the cetane indexes of 53 and 40-respectively. The pilot injection showed some significant effects on improving the ignition characteristics and fuel consumption as follows: (1) The pilot ignition delay and the main ignition delay were about half of the ignition delay of the normal injection respectively. (2) The lower fuel consumption and NOx could be attained by the pilot injection at the retarded injection timing, especially under the lower load condition. (3) The trade-off relationship between the specific fuel consumption and NOx was significantly improved by the pilot injection. (4) In the present short pilot-main interval, a small amount of pilot quantity was recommended to reduce NOx and fuelmore » consumption without deteriorating smoke density. 12 refs., 16 figs., 1 tab.« less

The Effect of Pilot Injection on Combustion in a Turbocharged D. I. Diesel Engine

In order to reduce NOx and smoke simultaneously and also to improve markedly the trade-off between smoke and NOx without deteriorating fuel consumption, natural gas was charged homogeneously into the intake air and was burned igniting by a small amount of gas oil injection in a four cylinder naturally-aspirated DI diesel engine. Combustion tests were carried out by changing the ratio of the amount of natural gas and the amount of gas oil first, secondarily the intake preheating temperature, and thirdly the EGR rate respectively. Effects of the respective parameter on the ignition and the burning rate of natural gas, exhaust emissions and specific fuel consumption were clarified experimentally. It is found that significant improvement of smoke-NOx trade-off can be obtained without deteriorating fuel consumption by the suitable combination between the natural gas charge rate, the intake preheating temperature and the EGR rate for each engine load condition.

Effect of EGR and Preheating on Natural Gas Combustion Assisted with Gas-Oil in a Diesel Engine

By positioning the completely rough wall locally on the hub side diffuser wall alone in the vaneless diffuser, the flow rate of rotating stall inception was decreased by 42 percent at a small pressure drop of less than 1 percent. This is based on the fact that the local reverse flow occurs first in the hub side in most centrifugal blowers with a backswept blade impeller. The three-dimensional boundary layer calculation shows that the increase in wall shear component normal to the main-flow direction markedly decreases the skewed angle of the three-dimensional boundary layer, and results in suppression of the three-dimensional separation. It is also clarified theoretically that the diffuser pressure recovery is hardly deteriorated by the rough wall positioned downstream of R = l.2 because the increase in the radial momentum change, resulting from reduction in the skewed angle of the three-dimensional boundary layer, supports the adverse pressure gradient.

Hironobu Ueki

Papers

Remarkable improvement of NOx–PM trade-off in a diesel engine by means of bioethanol and EGR

Prediction of NOx Reduction Rate Due to Port Water Injection in a DI Diesel Engine

The Effect of Pilot Injection on Combustion in a Turbocharged D. I. Diesel Engine

Effect of EGR and Preheating on Natural Gas Combustion Assisted with Gas-Oil in a Diesel Engine

Suppression of Rotating Stall by Wall Roughness Control in Vaneless Diffusers of Centrifugal Blowers