Ethanol direct injection plus gasoline port injection (EDI + GPI) is a new technology to make the use of ethanol fuel more effective and efficient in spark ignition engines. Multi-dimensional computational fluid dynamics modelling was conducted on an EDI + GPI engine in both single and dual fuelled conditions. The in-cylinder flow field was solved in the realizable − turbulence model with detailed engine geometry. The temporal and spatial distributions of the liquid and vapour fuels were simulated with the spray breakup and evaporation models. The combustion process was modelled with the partially premixed combustion concept in which both mixture fraction and progress variable were solved. The three-dimensional and five-dimensional presumed Probability Density Function (PDF) look-up tables were used to model the single-fraction-mixture and two-fraction-mixture turbulence–chemistry interactions respectively. The model was verified by comparing the numerical and experimental results of spray pattern and cylinder pressure. The simulation results showed that the combustion process of EDI + GPI dual-fuelled condition was partially premixed combustion because of the low evaporation rate of ethanol spray in low temperature environment before combustion. Compared with GPI only, the higher flame speed of ethanol fuel contributed to the greater pressure rise rate and maximum cylinder pressure in EDI + GPI condition, which consequently resulted in higher power output and thermal efficiency. The lower adiabatic flame temperature of ethanol, partially premixed combustion mode and stronger cooling effect of ethanol direct injection in EDI + GPI led to the reduced combustion temperature which contributed to the decrease of NO emission. Among these three factors, the lower adiabatic flame temperature and partially premixed combustion mode were the dominating factors that resulted in the low combustion temperature of EDI + GPI. On the other hand, CO and HC emissions increased because of the ethanol’s low evaporation rate in low temperature environment before combustion, which caused incomplete combustion.
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.
Hydrogen direct injection (HDI) in cylinder is considered as an effective method to improve natural gas engine performance. The present study aims to bridge the gap on the HDI in rotary engine, and to investigate the effect of hydrogen injection timing (IT) and hydrogen injection duration (ID) on mixture formation and combustion process of a hydrogen direct injection plus natural gas port injection (HDI + NGPI) rotary engine. Numerical approach was used in this study for obtaining some critical information, which was difficult to obtain through experiment, such as flow field, fuel distribution and some intermediate concentration fields in cylinder. The research results showed that for mixture formation, the distribution law of the hydrogen and the natural gas at the late stages of the compression stroke (100 CA (BTDC)), was as follows: at a fixed ID of 24 CA, with retarded hydrogen IT, the stratification phenomenon of hydrogen became obvious increasingly, and the hydrogen distribution area moved towards the back of the combustion chamber continuously. At a fixed IT of 210 CA (BTDC), with the extension in ID, the accumulation area of hydrogen reduced significantly, and the hydrogen continued to gather in the middle of the combustion chamber. For combustion process, the overall combustion rate for the hydrogen injection strategy which had an IT of 210 CA (BTDC) and ID of 40 CA (case ID5), was the fastest. This was due to the fact that compared with the leading spark plug (LSP), the combustion condition around the trailing spark plug (TSP) has a great influence on the combustion process. For case ID5 at ignition timing, the hydrogen concentration near the TSP is high enough for the rapid formation of flame kernel. Compared with case IT1 which had an IT of 390 CA (BTDC) and an ID of 24 CA, the improved combustion rate of case ID5 had a 11.7% increase in peak pressure, and a 7% decrease in NO emissions.
Ethanol direct injection plus gasoline port injection (EDI + GPI) is a new technology to utilise ethanol fuel more efficiently and flexibly in spark ignition engines. One issue needs to be addressed in the development of EDI + GPI is the ethanol fuel’s low vapour pressure and large latent heat which slow down the ethanol’s evaporation and result in the mixture unready for combustion by the time of spark ignition and the consequent increase of CO and HC emissions. Heating the ethanol fuel to be directly injected (EDI heating) has been proposed to address this issue. This paper reports the investigation of the effect of EDI heating on the combustion and emissions of a research engine equipped with EDI + GPI. The results showed that EDI heating effectively reduced the CO and HC emissions of the engine due to the increase of evaporation rate and reduced fuel impingement and local over-cooling. The reduction of CO and HC became more significant with the increase of ethanol ratio. When the temperature of the ethanol fuel was increased by 40 °C, the CO and HC were reduced by as much as 43% and 51% respectively in EDI only condition at the original spark timing of 15 CAD BTDC, and 15% and 47% respectively at the minimum spark advance for best torque (MBT) timing of 19 CAD BTDC. On the other hand, the NO emission was slightly increased, but still much smaller than that in GPI only condition due to the strong cooling effect and low combustion temperature of EDI. The IMEP and combustion speed were slightly reduced by EDI heating due to the decrease of injector fuel flow rate and spray collapse of flash-boiling. The largest decrease of IMEP was 5% at the original spark timing and 3% at the MBT timing. Moreover, at the MBT timing, the IMEP increased continuously with the increase of ethanol ratio in the entire range from 0% to 100%. This indicated that the decrease of IMEP in high ethanol ratio conditions at the original spark timing could be avoided by adjusting the spark timing. Therefore EDI heating is effective to address the issues of ethanol’s low evaporation rate in low temperature engine environment and over-cooling effect at high ethanol ratio condition in the development of EDI + GPI engine.
The present study investigated the effect of coolant temperature, injection pressure, and injection timing on emissions in a gasoline direct injection (GDI) engine. Two coolant temperatures of 40 °C and 80 °C, and wide range of injection timings from before top dead center (BTDC) 360° to BTDC 210° were tested under injection pressures in the range of 5 MPa–50 MPa. Particle number (PN), soot, total hydrocarbon (THC), and nitrogen oxides (NOx) were measured under the various experimental conditions. In addition, the spray and flame images were used to observe the spray-wall interaction and to identify the existence of a fuel film. Experimental results showed that the increase in injection pressure significantly reduced the particulate emissions, especially for the wall wetting condition (BTDC 330°). The PN emissions from the wall wetting condition was reduced by about 90% by increasing injection pressure from 10 MPa to 50 MPa. Furthermore, increasing the coolant temperature was an effective way to reduce the PN, soot, and THC. In particular, the THC was reduced by about 30%, while the change in injection pressure and injection timing varied by only 10%.
In this study, an increase in injection pressure was proposed as a solution to the problem of exhaust emissions, such as soot, NOx, CO, HC, in direct-injection spark-ignition gasoline engines. Mixture formation and combustion process were analyzed with KIVA-3V release 2 code. Combustion pressure and emission data were also measured experimentally. To validate the models used in simulation, spray tip penetration for various injection pressures, and combustion pressure for various injection timing and injection pressure combinations were compared with experimental data. The simulation using a constant-tuned models showed reliable results and simulations were carried out using validated models. When the fuel is injected while the intake flow is developing, the mixture homogeneity was reduced and combustion speed decreased. When the fuel is injected after the intake flow has fully developed and injection pressure was high, the combustion speed increased. High injection pressure was effective in increasing the mixture homogeneity in case of late injection timing. Therefore, increasing thermal efficiency without deteriorating exhaust emissions is possible when an injection pressure up to 50 MPa is used with late injection timing.
Earthquakes in unusual locations have become an important topic of discussion in both North America and Europe, owing to the concern that industrial activity could cause damaging earthquakes. It has long been understood that earthquakes can be induced by impoundment of reservoirs, surface and underground mining, withdrawal of fluids and gas from the subsurface, and injection of fluids into underground formations. Injection-induced earthquakes have, in particular, become a focus of discussion as the application of hydraulic fracturing to tight shale formations is enabling the production of oil and gas from previously unproductive formations. Earthquakes can be induced as part of the process to stimulate the production from tight shale formations, or by disposal of wastewater associated with stimulation and production. Here, I review recent seismic activity that may be associated with industrial activity, with a focus on the disposal of wastewater by injection in deep wells; assess the scientific understanding of induced earthquakes; and discuss the key scientific challenges to be met for assessing this hazard.
In this paper, effect of varying fuel injection pressures and injection timings on particulate size number distribution and spray characteristics was investigated in a single cylinder, common rail direct injection (CRDI) compression ignition (CI) engine fueled with Karanja biodiesel blends vis-à-vis baseline mineral diesel. The investigation results of spray tip penetration and spray area of biodiesel blends and diesel showed that higher fuel injection pressure result in a longer spray tip penetration and larger spray area than that at lower injection pressures at same elapsed time after the start of injection (SOI). In order to compare the effect of fuel injection parameters, 10, 20 and 50% Karanja biodiesel blends at 1500 rpm engine speed were compared with baseline data from mineral diesel. It was observed that average particulate size increased with retarding the SOI timings. Particulate number concentration was lowest for 10% biodiesel blend, which increased with further increase in biodiesel content in the blended test fuel. Addition of even very small quantity of biodiesel in the test fuel helped in reducing particulate emissions.
This paper presents a fast and autonomous injection frequency tracking and locking technique. In the present injection-locking system, a quadrature injection-locked oscillator (QILO) is third harmonically locked to a quadrature voltage-controlled oscillator (QVCO). In the frequency tracking loop, the frequency difference between QVCO and QILO is extracted using the QILO's amplitude modulated (AM) envelope waveform. The AM frequency of the envelope signal bears frequency difference between the two oscillators. The envelope signal is further converted to pulse signal which subsequently drives digital feedback control circuitry to update the QILO's output frequency so that it can track the third harmonic of the injection QVCO. The frequency calibration process is purely autonomous, self-initiating whenever the AM modulated envelope waveform is generated. The feedback signal is primarily processed in the digital domain, resulting in a compact, fast, and power-efficient injection frequency-locked loop (IFLL). By incorporating a phase noise (PN) calibration routine after completing the frequency calibration, the presented IFLL resolves the intractable issue of PN degradation at the edge of the slave oscillator's injection locking range. This results in a large injection frequency tracking range of 26.5-29.7 GHz which is only limited by the QILO's LC tank tuning range. The IFLL realized in 0.13-μm CMOS consumes 2.4 mW with a negligible area penalty. Overall chip size including QVCO, QILO, and IFLL is 1 × 1 mm 2 .
This study was performed to analyze the wall impingement and fuel film formation in a DISI engine with injection strategies using image-based analysis and CFD. The direct injection engine uses a high-pressure injection strategy to improve the homogeneity of the air-fuel mixture, so the spray behavior was analyzed by spray visualization for various injection pressures, and the wall impingement was predicted for various engine operating conditions based on the acquired images. The mass distribution of the injected fuel was calculated using the injection profiles and the spray image, and the amount of fuel that impinges on the piston and wall (i.e., the geometric boundaries of the cylinder) was calculated using data from the spray behavior for various engine operation conditions such as load and engine speed. The image-based analysis was limited to understanding the influence of the injection strategy on the droplet behavior after wall impingement of the fuel spray. Therefore, CFD using KIVA 3 V code was additionally conducted to analyze the effects of the injection strategies on wall film formation and droplet rebounding reflecting in-cylinder conditions. In the early- and late-injection conditions, the initial piston position is high, and most of the injected fuel impinges on the piston. As the injection pressure increases, the injection timing at which wall impingement occurs is advanced because of the rapid spray development. The results of the 3D analysis for the temperature and the intake flow in the engine cylinder showed that both the wall impingement and the fuel film were reduced as the injection pressure increased because the fuel evaporation increased due to improved atomization.