Search Results

The present study helps to understand the local combustion characteristics of PREmixed Mixture Ignition in the End-gas Region (PREMIER) combustion mode while using increasing amount of natural gas as a diesel substitute in conventional CI engine. In order to reduce NOx emission and diesel fuel consumption micro-pilot diesel injection in premixed natural gas-air mixture is a promising technique. New strategy has been employed to simulate dual fuel combustion which uses well established combustion models. Main focus of the simulation is at detection of an end gas ignition, and creating an unified modeling approach for dual fuel combustion. In this study G-equation flame propagation model is used with detailed chemistry in order to detect end-gas ignition in overall low temperature combustion. This combustion simulation model is validated using comparison with experimental data for dual fuel engine.

An applicable and comprehensive control strategy of a natural gas/diesel dual fuel engine is presented in this paper. The dual fuel engine is converted from a conventional mechanical pump, turbo charged, heavy duty diesel engine. In the dual fuel mode, the pedal position is explained as demanded total fuel quantity, the quantity of pilot diesel and natural gas are calculated in order to provide the equal energy with the original diesel engine at the same operation condition, the proportion of the natural gas is primarily determined by the load rate and the speed of the engine. When the engine is working under light or moderate load, the intake air is throttled in order to improve the brake mean effective pressure and reduce the hydrocarbon emissions of the dual fuel engine, according to target excess air ratio and the quantities of the two fuels, the desired air mass per cycle can be obtained.

With increasing interest to reduce the dependency on gasoline and diesel, alternative energy source like compressed natural gas (CNG) is a viable option for internal combustion engines. Spark-ignited (SI) CNG engine is the simplest way to utilize CNG in engines, but direct injection (DI) Diesel-CNG dual-fuel engine is known to offer improvement in combustion efficiency and reduction in exhaust gases. Dual-fuel engine has characteristics similar to both SI engine and diesel engine which makes the combustion process more complex. This paper reports the computational fluid dynamics simulation of both DI dual-fuel compression ignition (CI) and SI CNG engines. In diesel-CNG dual-fuel engine simulations and comparison to experiments, attention was on ignition delay, transition from auto-ignition to flame propagation and heat released from the combustion of diesel and gaseous fuel, as well as relevant pollutants emissions.

Natural gas has been considered to be one of the most promising alternative fuels due to its lower NOx and soot emissions, less carbon footprint as well as attractive price. Furthermore, higher octane number makes it suitable for high compression ratio application compared with other gaseous fuels. For better economical and lower emissions, a turbocharged, four strokes, direct injection, high pressure common rail diesel engine has been converted into a diesel/natural gas dual-fuel engine. For dual-fuel engine operation, natural gas as the main fuel is sequentially injected into intake manifold, and a very small amount of diesel is directly injected into cylinder as the ignition source. In this paper, a dual-fuel electronic control unit (ECU) based on the PowerPC 32-bit microprocessor was developed. It cooperates with the original diesel ECU to control the fuel injection of the diesel/natural gas dual-fuel engine.

Natural gas has become an attractive alternative for diesel fuel due to its higher octane number, richer reserves and lower price. It has been utilized in compression ignition engines to obtain a higher thermal efficiency compared with spark ignition engines. However, its relatively higher auto-ignition temperature increases the difficulty of compression-ignition based on present hardware devices. One optimal ignition method is that a very small quantity of diesel fuel as the only ignition resource pilot-ignites the lean natural gas-air mixture. This micro diesel pilot-ignited natural gas premixed charge compression ignition (DPING-PCCI) combustion strategy is easy to implement without major hardware modifications, and can significantly reduce the NOx and particle mass emissions from diesel engines. Although the DPING-PCCI has so many advantages, it suffers from poor engine stability and high ultrafine particles emissions at part loads.

This study presents a detailed experimental investigation on the cycle-by-cycle variations in a natural gas/diesel dual fuel engine with EGR. The experiment used a single-cylinder, four-stroke, water-cooled, DI diesel engine. The EGR ratio, diesel injection timing and pilot diesel quantity were varied respectively while all the other parameters were held constant. The parameters of cylinder pressure are used to investigate the cyclic variations. The results show that the cylinder peak pressure, the maximum rate of pressure rise and the indicated mean effective pressure decrease. COVimep increases to 18.9% with 25% EGR ratio. The interdependency between the pressure parameters and their corresponding crank angles become weak with the increasing EGR ratio. The increasing EGR ratio increases the ignition delay. The cylinder peak pressure and the maximum rate of pressure rise increase dramatically with the advance of the pilot diesel injection timing.

When the global energy consumption continues to increase, the research hotspot in the field of internal combustion engine (ICE) is how to improve the fuel utilization efficiency to achieve the energy saving. But as far as the engine efficiency is concerned, it has been very difficult to improve the fuel utilization efficiency after the Gasoline Direct-Injection (GDI) and Homogeneous Charge Compression Ignition (HCCI) technology were adopted. In this study, the exothermic distribution of fuel was studied detailedly when a TOYOTA 8A-FE gasoline engine operated at different working conditions through conducting steady-state experiment. Only one third of fuel's chemical energy is converted into effective work by engine, the rest is released to the environment in the form of waste heat generated from cooling and exhaust gas. But except the waste heat that has to be released to the environment according to the second law of thermodynamics, the rest can be theoretically utilized.