As internal combustion engines (ICEs) produce serious emissions and a big part of greenhouse gases from fuel combustion. Due to the universal concerns about degradation in the ambient environment, limitations on exhaust emissions, depletion of petroleum reserves, and global warming, many strict regulations have been launched on the standard emissions released from engines. These challenges oblige engine researchers worldwide to develop a new strategic balance between engine performance and emissions. Premixed charge compression ignition (PCCI) is a promising technique to overcome these challenges in recent years which can simultaneously reduce NOx and soot emissions and substantially improve thermal efficiency. The PCCI combustion concept has the advantages of both SI and CI engines, like SI engines as the charge is premixed which produces low emissions and like CI engines the fuel-air mixture is auto-ignited as a result of compression which leads to high thermal efficiency. Normally, PCCI combustion is a single-stage combustion process achieved by employing early injection timing to increase the time available for mixing fuel and air by using single-fuel and split fuel (pilot/main) injection tactics, in which a large fraction of fuel burns in premixed combustion phase resulting in relatively lower in-cylinder temperatures compared to compression ignition (CI) combustion. Thus, the objective of this paper is to provide an inclusive review of the effects of fuel injection timings, ratios, pressure, and fuel properties on the PCCI engine combustion performance improvement and emission reduction, this review has been analyzed extensively based on the published studies to provide and discuss different strategies for the control of PCCI technique of combustion at a wide range of speed and load.

Recently the world has a very important need for replacement fossil fuel with renewable sources of energy. Greenhouse effect is considered one of bad effects of fossil fuels, which causes increase of global temperature. Biodiesel is one of fossil fuel alternatives, which can be produced from many organic sources. Scientists are searching for adding nanomaterials to fueling system, which can modify fuel characteristic in compression champers. In this study diesel fuel will be replaced with blends of diesel and biodiesel produced from waste cooking oil (WCO) is created using a catalytic transesterification reaction (CTR). With the addition of a low concentration of alcohol over the period of an hour at a reaction temperature of 65 °C, (CTR) converts (WCO) to methyl esters. Blends consisting of (40 % diesel, 60 % biodiesel and CuO nano-martial with different concentration) will be prepared for fueling direct injection engine four-stroke. The engine will be run at 1400 rpm with natural aspiration under various loads. Using blends of (pure diesel, B40 [consist of 60 % biodiesel and 40 % diesel], 50b40 [consist of 60 % biodiesel, 40 % diesel and 50 mg CuO], 100B40 [consist of 60 % biodiesel, 40 % diesel and 100 mg CuO], 150 [consist of 60 % biodiesel, 40 % diesel and 150 mg CuO] and pure diesel). On engine performance and emissions, the impact of using copper oxide has been studied. The results of the experiment demonstrate that diesel engines can run on various mixtures of fuel, biodiesel, and CuO nano-material under the same operating conditions. The obtained data indicates that a 10% increase in brake thermal efficiency was noted, decrease in exhaust temperature with 11.6 % and decrease in brake specific fuel consumption with 6.66 %.

The shortage of fossil fuels is a significant political and economic issue that occurred due to global reliance on fossil fuels. The fuel characteristics of the produced diesel and biofuel (viscosity, density, cloud point, flash point, acid number, lower heating values, and pour point) are then determined. It is anticipated that using biofuel will result in higher fuel usage than using diesel fuel. This scenario also has an impact on the emissions. Biofuel has a higher density than diesel fuel, which has a detrimental impact on emissions and engine performance. It may be inferred that, while using the identical diesel engine for comparison, the effects of waste oil-derived biofuel are distinct from those of diesel fuel. Therefore, in order to achieve the best outcomes, it is crucial to develop new forms of biofuels. Nanomaterials (NMs), like copper oxides, titanium oxides, and aluminium oxides have been developed to be the most promising fuel additives for diesel engines in recent years. A significant amount of laboratory testing has been conducted up to this point to investigate the impact of using nano fuels on several aspects of diesel engine characteristics, particularly on hazardous emissions and engine performance (BSFC, effective power, BTE). This study provides an overview of the findings so far and the current situation regarding the use of nano fuels in diesel engines. Additionally, among the group of the most tested fuel additive nanoparticles, the best NMs/base fuel combinations are found based on two criteria that either involves all diesel engine parameters or simply diesel emissions. There are numerous techniques for improving engine performance. Nanoparticles can be used as catalysts in chemical reactions and feedstock retreatment processes to produce biofuels. According to the overall findings, adding nanoparticles significantly reduced the amount of fuel used for brakes by 20% to 23% when compared to biodiesel-diesel blends with and without the addition of alcohol. In addition to improving the combustion process and boosting the brake power by 2.5% to 4%, nanoparticles have a high thermal conductivity. Emission data revealed that while HC, CO, and PM emissions all dramatically decreased in most reviews, NO emissions increased by up to 55%.

One of the major issues, the energy crisis, makes the globe dangerous and violent [1]. Every day, there is an increase in energy demand. Resources of energy are running out swiftly, and all indicators point to their impending demise. In such cases, renewable energy sources must be given more consideration. The widespread use of fossil fuels renders them unsustainable because they increase CO2 levels and emit greenhouse gases that harm the environment [2]. With several trials of usage of HHO gas or compressed natural gas as a fuel performance improver on both internal combustion engines powered by gasoline or diesel up until this point, many advancements have been made in this field[3]. This paper comprises a survey of the numerous advancements that have occurred in this area. There was a net lead to an amplified in brake power from 2.1% to 5.8% and an increase in brake thermal efficiency from 10.27% to 35% with the addition of HHO gas. The usage of traditional fuels decreased by 20% to 30%, and HC and CO exhaust emissions decreased by an average of 14% and 18%, respectively.

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