Modelling of combustion and nitrogen oxide formation in hydrogen-fuelled internal combustion engines within a 3D CFD code

Hong

2016

Energy

Ethanol direct injection plus gasoline port injection (EDI+GPI) is a new technology to utilise ethanol fuel more effectively and efficiently in spark-ignition engines by taking the advantages of ethanol fuel and direct injection, such as the cooling effect and anti-knock ability. A full cycle numerical modelling including both port and direct injection sprays was performed to understand the mechanisms behind the experimental results of the EDI+GPI engine. The turbulence-chemistry interaction of the two-fraction-mixture partially premixed combustion was solved by a five-dimensional presumed Probability Density Function table.Effects of direct injection timing on fuel evaporation, mixing, wall-wetting, combustion and emission processes were investigated. The results showed that when the direct injection timing was retarded, the mixture around the spark plug became leaner and the distribution of equivalence ratio became more uneven.Moreover, late direct injection resulted in severe fuel impingement and caused local over-cooling effect and over-rich mixture. Consequently, the combustion speed and temperature were decreased by retarded direct injection timing, leading to reduced NO emission and increased HC and CO emissions. Finally, numerical modelling was performed to investigate the strategy of injecting small amount of ethanol fuel on reducing the fuel impingement and incomplete combustion caused by late direct injection.

Section: D Engine Modelmentioning

confidence: 99%

Effect of injection timing on mixture formation and combustion in an ethanol direct injection plus gasoline port injection (EDI+GPI) engine

Hong

2016

Energy

“…Nitric oxide emission is about 30% lower than presented by Rudkowski et al [10] for two stroke gas engine GMVH-8 with EGR, but still four to five times higher than emission limits for new engines [7]. The gas analyzers for THC were calibrated using a mixture of CH 4 and N 2 as span gas, thus the displayed results for high hydrocarbons emission refer to molar fraction of methane in flue gases. The maximum value of THC (0.82%) was obtained for the rotational speed equal to 290 rpm which is about 7.8% of the total amount of fuel delivered to the engine.…”

Section: Study Of One Cylinder Workmentioning

confidence: 98%

Analysis of Combustion Process in Industrial Gas Engine with Prechamber-Based Ignition System

et al. 2018

Application of a pre-combustion chamber (PCC) ignition system is one of the methods to improve combustion stability and reduce toxic compounds emission, especially NO x . Using PCC allows the operation of the engine at lean combustion conditions or the utilization of low calorific gaseous fuels such as syngas or biogas. The paper presents the results of an experimental study of the combustion process in two stroke, large bore, stationary gas engine GMVH 12 equipped with two spark plugs (2-SP) and a PCC ignition system. The experimental research has been performed during the normal operation of the engine in an industrial compression station. It was observed that application of PCC provides less cycle-to-cycle combustion variation (more than 10%) and nitric oxide and carbon monoxide emissions decreased to 60% and 26% respectively. The total hydrocarbon (THC) emission rate is 25% higher for the engine equipped with PCC, which results in roughly two percent engine efficiency decrease. Another important criterion of engine retrofitting was the PCC location in the engine head. The experimental results show that improvement of engine operating parameters was recorded only for a configuration with one port offset by 45 • from the axis of the main chamber. The study of the ignition delay angle and equivalence ratio in PCC did not demonstrate explicit influence on engine performance.

SAE Technical Paper Series

“…It has a wide range of flammability [3,4] that allows engines to operate very lean and at high efficiency. This can also lead to greatly reduced NO X emissions at equivalence ratios lower than about 0.5 [5][6][7]. In order to eliminate hydrogen abnormal combustion modes such as pre-ignition and backfiring [8][9][10], injecting hydrogen directly into the combustion chamber (DI) after intake valves closure (IVC) has been proposed as a more suitable strategy in comparison to port fuel injection (PFI).…”

Section: Introductionmentioning

confidence: 99%

Computational Study of Hydrogen Direct Injection for Internal Combustion Engines

Hamzehloo¹,

Aleiferis²

2013

Hydrogen has been largely proposed as a possible fuel for internal combustion engines. The main advantage of burning hydrogen is the absence of carbon-based tailpipe emissions. Hydrogen's wide flammability also offers the advantage of very lean combustion and higher engine efficiency than conventional carbon-based fuels. In order to avoid abnormal combustion modes like pre-ignition and backfiring, as well as air displacement from hydrogen's large injected volume per cycle, direct injection of hydrogen after intake valve closure is the preferred mixture preparation method for hydrogen engines. The current work focused on computational studies of hydrogen injection and mixture formation for direct-injection spark-ignition engines. Hydrogen conditions at the injector's nozzle exit are typically sonic. Initially the characteristics of under-expanded sonic hydrogen jets were investigated in a quiescent environment using both Reynolds-Averaged NavierStokes (RANS) and Large-Eddy Simulation (LES) techniques. Various injection conditions were studied, including a reference case from the literature. Different nozzle geometries were investigated, including a straight nozzle with fixed cross section and a stepped nozzle design. LES captured details of the expansion shocks better than RANS and demonstrated several aspects of hydrogen's injection and mixing. Incylinder simulations were also performed with a side 6-hole injector using 70 and 100 bar injection pressure. Injection timing was set to just after inlet valve closure with duration of 6 μs and 8 μs, leading to global air-to-fuel equivalence ratios  typically in the region of 0.2-0.4. The engine intake air pressure was set to 1.5 bar absolute to mimic boosted operation. It was observed that hydrogen jet wall impingement was always prominent. Comparison with non-fuelled engine conditions demonstrated the degree of momentum exchange between in-cylinder hydrogen injection and air motion. LES highlighted details of hydrogen's spatial distribution throughout the injection duration and up to ignition timing. Higher peak velocities were predicted by LES, especially on the tumble plane. With the employed injection strategy, the areas closer to the cylinder wall were richer in fuel than the centre of the chamber close to the end of compression.