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Regulations have been established for the monitoring and reporting of greenhouse gas (GHG) emissions and fuel consumption from the transport sector. Low carbon fuels combined with new powertrain technologies have the potential to provide significant reductions in GHG emissions while decreasing the dependence on fossil fuel. In this study, a lean-burn ethanol-diesel dual-fuel combustion strategy has been used as means to improve upon the efficiency and emissions of a conventional diesel engine. Experiments have been performed on a 2.0 dm3 single cylinder heavy-duty engine equipped with port fuel injection of ethanol and a high-pressure common rail diesel injection system. Exhaust emissions and fuel consumption have been measured at a constant engine speed of 1200 rpm and various steady-state loads between 0.3 and 2.4 MPa net indicated mean effective pressure (IMEP).

Engine downsizing of the spark ignition gasoline engine is recognized as one of the most effective approaches to improve the fuel economy of a passenger car. However, further engine downsizing beyond 50% in a 4-stroke gasoline engine is limited by the occurrence of abnormal combustion events as well as much greater thermal and mechanical loads. In order to achieve aggressive engine downsizing, a boosted uniflow scavenged direct injection gasoline (BUSDIG) engine concept has been proposed and researched by means of CFD simulation and demonstration in a single cylinder engine. In this paper, the intake port design on the in-cylinder flow field and gas exchange characteristics of the uniflow 2-stroke cycle was investigated by computational fluid dynamics (CFD). In particular, the port orientation on the in-cylinder swirl, the trapping efficiency, charging efficiency and scavenging efficiency was analyzed in details.

In order to minimize short-circuiting of the intake charge in the poppet-valved 2-stroke engine, measures are taken to generate reversed tumble in the cylinder. In this study, five different types of intake ports and three types of pent-roof geometries were designed and analysed of their ability to generate and maintain reversed tumble flows by means of CFD simulation for their intake processes on a steady flow rig. Their flow characteristics were then assessed and compared to that of the vertical top-entry ports. Results show that the side-entry port designs can achieve comparatively high tumble intensity. The addition of flow deflectors inside the side-entry ports does not have much effect on the reversed tumble ratio. The top-entry ports have the highest flow coefficient among all the intake ports examined as well as producing strong reversed tumble. It is also found that the pent-roof at a wider angle helps to strengthen the tumble intensity due to increased air flow rate.

The work was concerned with visualisation of the charge homogeneity and cyclic variations within the planar fuel field near the spark plug in an optical spark ignition engine fitted with an outwardly opening central direct fuel injector. Specifically, the project examined the effects of fuel type and injection settings, with the overall view to understanding some of the key mechanisms previously identified as leading to particulate formation in such engines. The three fuels studied included a baseline iso-octane, which was directly compared to two gasoline fuels containing 10% and 85% volume of ethanol respectively. The engine was a bespoke single cylinder with Bowditch style optical access through a flat piston crown. Charge stratification was studied over a wide spectrum of injection timings using the Planar Laser Induced Fluorescence (PLIF) technique, with additional variation in charge temperature due to injection also estimated when viable using a two-line PLIF approach.

With the application of valve timing strategy to inlet and exhaust valves, Homogeneous Charge Compression Ignition (HCCI) combustion was achieved by varying the amount of trapped residuals through negative valve overlap on a Ricardo Hydra four-stroke port fuel injection engine fueled with ethanol. The effect of ethanol on HCCI combustion and emission characteristics at different air-fuel ratios, speeds and valve timings was investigated. The results indicate that HCCI ethanol combustion can be achieved through changing inlet and exhaust valve timings. HCCI ethanol combustion range can be expanded to high speeds and lean burn mixture. Meanwhile, the factors influencing ignition timing and combustion duration are valve timing, lambda and speeds. Moreover, NOx emissions are extremely low under HCCI combustion. The emissions-speed and emissions-lambda relationships are obtained and analyzed.

In this paper, an experimental study was performed to investigate characteristics of flame propagation and knocking combustion of hydrous (10% water content) and anhydrous ethanol at different air/fuel ratios in comparison to RON95 gasoline. Experiments were conducted in a full bore overhead optical access single cylinder port-fuel injection spark-ignition engine. High speed images of total chemiluminescence and OH* emission was recorded together with the in-cylinder pressure, from which the heat release data were derived. The results show that under the stoichiometric condition anhydrous ethanol and wet ethanol with 10% water (E90W10) generated higher IMEP with at an ignition timing slightly retarded from MBT than the gasoline fuel for a fixed throttle position. Under rich and stoichiometric conditions, the knock limited spark timing occurred at 35 CA BTDC whereas both ethanol and E90W10 were free from knocking combustion at the same operating condition.

Poppet-valve two-stroke gasoline engines can increase the specific power of their four-stroke counterparts with the same displacement and hence decrease fuel consumption. However, knock may occur at high loads. Therefore, the combustion with stratified lean mixture was proposed to decrease knock tendency and improve combustion stability in a poppet-valve two-stroke direct injection gasoline engine. The effect of intake pressure and split injection on fuel distribution, combustion and knock intensity in lean mixture conditions at high loads was simulated with a three-dimensional computational fluid dynamic software. Simulation results show that with the increase of intake pressure, the average fuel-air equivalent ratio in the cylinder decreases when the second injection ratio was fixed at 70% at a given amount of fuel in a cycle.

SI-CAI hybrid combustion, also known as spark-assisted compression ignition (SACI), is a promising concept to extend the operating range of CAI (Controlled Auto-Ignition) and achieve the smooth transition between spark ignition (SI) and CAI in the gasoline engine. In order to stabilize the hybrid combustion process, the port fuel injection (PFI) combined with gasoline direct injection (GDI) strategy is proposed in this study to form the in-cylinder fuel stratification to enhance the early flame propagation process and control the auto-ignition combustion process. The effect of bowl piston shapes and fuel injection strategies on the fuel stratification characteristics is investigated in detail using three-dimensional computational fluid dynamics (3-D CFD) simulations. Three bowl piston shapes with different bowl diameters and depths were designed and analyzed as well as the original flat piston in a single cylinder PFI/GDI gasoline engine.

The outward-opening piezoelectric injector can achieve stable fuel/air mixture distribution and multiple injections in a single cycle, having attracted great attentions in direct injection gasoline engines. In order to realise accurate predictions of the gasoline spray with the outward-opening piezoelectric injector, the computational fluid dynamic (CFD) simulations of the gasoline spray with different droplet breakup models were performed in the commercial CFD software STAR-CD and validated by the corresponding measurements. The injection pressure was fixed at 180 bar, while two different backpressures (1 and 10 bar) were used to evaluate the robustness of the breakup models. The effects of the mesh quality, simulation timestep, breakup model parameters were investigated to clarify the overall performance of different breakup model in modeling the gasoline sprays.

Low combustion efficiency and high hydrocarbon emissions at low loads are key issues of natural gas and diesel (NG-diesel) dual fuel engines. For better engine performance, two diesel-spray-orientated (DSO) bowls were developed based on the existing diesel injector of a heavy-duty diesel engine with the purpose of placing more combustible natural gas/air mixture around the diesel spray jets. A protrusion-ring was designed at the rim of the piston bowl to enhance the in-cylinder flame propagation. Numerical simulations were conducted for a whole engine cycle at engine speed of 1200 r/min and indicated mean effective pressure (IMEP) of 0.6 MPa. Extended coherent flame model 3 zones (ECFM-3Z) combustion model with built-in soot emissions model was employed. Simulation results of the original piston bowl agreed well with the experimental data, including in-cylinder pressure and heat released rate (HRR), as well as soot and methane emissions.

In order to optimize the 2-stroke uniflow engine performance on vehicle applications, numerical analysis has been introduced, 3D CFD model has been built for the optimization of intake charge organization. The scavenging process was investigated and the intake port design details were improved. Then the output data from 3D CFD calculation were applied to a 1D engine model to process the analysis on engine performance. The boost system optimization of the engine has been carried out also. Furthermore, a vehicle model was also set up to investigate the engine in-vehicle performance.

This study evaluates the performance of an ethanol fueled spark ignited engine running with high levels of hydration. Ethanol is a renewable fuel and has been considered a promising alternative to counteract global warming and to reduce pollutant emissions. Its use is well established in ICE as the main fuel or blended with gasoline. However, due to its lower calorific value, it shows increased fuel consumption when compared to gasoline, rendering its use sometimes less attractive. The energy demand to produce ethanol, especially at the distillation phase, increases exponentially as the concentration of ethanol-in-water goes from 80% onwards. Thus, mixtures with less than 80% of ethanol-in-water would reduce the energy consumption during production, yielding a less expensive fuel. In previous studies, to evaluate the feasibility of wet ethanol as a fuel for spark-ignited engines, results have shown that it was possible to use mixtures of up to 40% of water-in-ethanol.

The prediction of ignition delay times is very useful during the development phase of internal combustion engines. When it comes to biofuels such as ethanol and its blends with gasoline, its importance is enhanced, especially when it comes to flex-fuel engines and the need to address current and future emissions legislations and efficiency goals. The ignition delay time measured as the angular difference between the spark discharge time, as commanded by the ECU and a relevant fraction of fuel mass burned (usually, 2, 5 or 10%). Experimental tests were performed on a downsized state-of-the-art internal combustion engine. Engine speed of 2500 rpm, with load of 6 and 13 bar IMEP were set for investigation. Stoichiometric operation and MBT or knock-limited spark timings were used, while valve overlap was varied, in order to address the effects of scavenging and residuals on ignition delay times.

Biofuels for internal combustion engines have been explored worldwide to reduce fossil fuel usage and mitigate greenhouse gas emissions. Additionally, increased spark ignition (SI) engine part load efficiency has been demanded by recent emission legislation for the same purposes. Considering theses aspects, this study investigates the use of non-conventional valve timing strategies in a 0.35 L four valve single cylinder test engine operating with anhydrous ethanol. The engine was equipped with a fully variable valve train system enabling independent valve timing and lift control. Conventional spark ignition operation with throttle load control (tSI) was tested as baseline. A second valve strategy using dethrottling via early intake valve closure (EIVC) was tested to access the possible pumping loss reduction. Two other strategies, negative valve overlap (NVO) and exhaust rebreathing (ER), were investigated as hot residual gas trapping strategies using EIVC as dethrottling technique.

Over the last decade, the high speed direct injection (HSDI) diesel engine has made dramatic progress in both its performance and market share in the light duty vehicle market. However, with ever more stringent emission legislation to be introduced over coming years, the simultaneous reduction of NOx and Particulate Matter (PM) from the HSDI diesel engine is being intensively researched. As part of a European Union (EU) NICE integrated project, research has been carried out to investigate the fuel injection and combustion from a narrow cone fuel injector in a high speed direct injection single cylinder engine with optical access utilising a multiple injection strategy and various alternate fuels. The fuel injection process was visualised using a high speed imaging system comprising a copper vapour laser and a high speed video camera. The auto-ignition and combustion process was analysed through the chemiluminescence images of CHO and OH using an intensified CCD camera.

A numerical study has been performed to investigate the soot emission from a high-speed single-cylinder direct injection diesel engine. It was shown that the current KIVA CFD code with the standard evaporation model could predict the experimental trend, where at a low speed running condition a higher smoke reading is reached when increasing the injector protrusion into the piston chamber and conversely a lower smoke reading was recorded for the same change in injector protrusion at a high running speed condition. Evidence of inappropriate air/fuel mixing was seen via rates of heat release analyses, especially in the high-speed conditions. Efforts to reduce this discrepancy by way of improvements to the KIVA breakup and evaporation models were made. Results of the modified models showed improvements in the vapor dispersion of the atomizing liquid jet, thus affecting the mixing rates and predicted smoke emissions.

The environmental and sustainable energy concerns in transport are being addressed through the decarbonisation path and the potential of hydrogen as a zero-carbon alternative fuel. Using hydrogen to replace fossil fuels in various internal combustion engines shows promise in enhancing efficiency and achieving carbon-neutral outcomes. This study presents an experimental investigation of hydrogen (H2) combustion and engine performance in a boosted spark ignition (SI) engine. The H2 engine incorporates both port fuel injection (PFI) and direct injection (DI) hydrogen fuel systems, capable of injecting hydrogen at pressures of up to 4000 kPa in the DI system and 1000 kPa in the PFI operations. This setup enables a direct comparison of the performance and emissions of the PFI and DI operations. The study involves varying the relative air-to-hydrogen ratio (λ) at different speeds to explore combustion and engine limits for categorising and optimising operational regions.

Zero-dimensional zonal models are seen as interesting tools for engine simulation due to their simplicity and yet accuracy in fitting or predicting experimental data. For combustion, a common model is a dual zone model, in which two-zones, spatially homogeneous, are set during the combustion process. Such model take into account an interface of infinitesimal thickness for the separation between zones. The success of this simulation approach depends on the accuracy of the heat transfer model. These models aim to obtain the heat transfer coefficient from the combustion gases in contact with the cylinder walls. Several heat transfer correlations from the literature can be used to obtain the heat transfer coefficient.

In order to investigate feasibility of DME (Di-methyl ether) assisted gasoline CAI (controlled-auto ignition) combustion, direct DME injection is employed to act as the ignition source to trigger the auto-ignition combustion of premixed gasoline/air mixture with high temperature exhaust gas. Intake re-breathing valve strategy is adopted to obtain internal exhaust recirculation (EGR) that regulates heat release rate and ignitability of the premixed gasoline and air mixture. The effects of intake re-breathing valve timing and 2nd DME injection timing of different split injection ratios were investigated and discussed in terms of combustion characteristics, emission and efficiencies. The analyses showed that re-breathing intake valve timing had a large effect on the operation range of CAI combustion due to EGR and intake temperature variation.

The effects of load, speed, exhaust gas recirculation (EGR) level and hydrogen addition level on the emissions from a diesel engine have been investigated. The experiments were performed on a 2.0 litre, 4 cylinder, direct injection engine with a high pressure common-rail injection system. Injection timing was varied between 14° BTDC and TDC and injection pressures were varied from 800 bar to 1400 bar to find a suitable base point. EGR levels were then varied from 0% to 40%. Hydrogen induction was varied between 0 and 6% vol. of the inlet charge. In the case of using hydrogen and EGR, the hydrogen replaced air. The load was varied from 0 to 5.4 bar BMEP at two engine speeds, 1500 rpm and 2500 rpm. For this investigation the carbon monoxide (CO), total unburnt hydrocarbons (THC), nitrogen oxides (NOx) and the filter smoke number (FSN) were all measured.