Effect Of Direct Water Injection Research Articles

Effects of Direct Water Injection on the Nitrogen Oxide Emission Characteristics of Marine Diesel Engines

Effects of Direct Water Injection on the Nitrogen Oxide Emission Characteristics of Marine Diesel Engines

Infrared Experimental Investigations of the Effects of Direct Water Injection in an Optical Engine

Abstract The effects of water injection (WI) on combustion characteristics were investigated in an optically accessible light-duty engine retrofitted with a side-mounted water injector. The main objective was to study the effect of water injection on autoignition and subsequent combustion process in compression ignition (CI) engines. Numerical zero-dimensional simulations were first performed to separate the thermal from the kinetic effects of water on the ignition delay and maximum temperature reached by a reacting mixture. Then, experimental investigations were performed at different intake temperatures and levels of thermal stratification achieved via direct water injection. Combustion analysis was performed on cylinder pressure data to study the effect of water injection on the overall combustion process. Infrared (IR) imaging was performed to provide insight to how water injection and the resulting water distributions affect thermal stratification, autoignition, and combustion characteristics. A new method in quantifying the water distributions is suggested. The results show that the overall level of stratification is sensitive to water injection timing and pressure, where increased water injection pressures and advanced injection timings result in more homogenous distributions. Moreover, water injection was found to affect the location of ignition kernels and the local presence of water suppressed ignition. The level of water stratification was also observed to affect the combustion process, where more homogenous distributions lost their ability to influence ignition locations. Finally, the infrared images showed high levels of residual water left over from prior water-injected cycles, suggesting that hardware configurations and injection strategies must be optimized to avoid wall wetting for stable engine operation.

Direct water injection and combustion time in SI engines

Over time, internal combustion engines were profoundly developed becoming more reliable, more economical and less polluting. Even if the current trend is headed towards hybrid and electric vehicles, the development of these engines continues by optimizing its operation with alternative fuels and innovative technologies. Water injection in internal combustion engines is one important way towards engine optimization. This study aims to experimentally determine the effects of direct water injection on the combustion duration of spark-ignition engines. As the thermal processes in internal combustion engines are very complex, the shape of the combustion chamber and other factors, such as the direct water injection timing has a direct influence on the results. This paper explores the potential for such a system in terms of combustion duration showing that the water injection can be beneficial. The concept was applied to a side-valve engine, as this design has a broader potential for injector location and aim.

Effect of direct water injection on combustion and emissions characteristics of marine diesel engines

In this study, the effect of direct water injection (DWI) was investigated on the performance of marine diesel engine based on the three-dimensional simulation model. The water injection quantity, temperature and timing were researched on the in-cylinder pressure and temperature, indicated power and NOx emissions. Then, the DWI strategies were compared with the exhaust gas recirculation (EGR). The results showed that the in-cylinder pressure, temperature, indicated power and NOx emissions decrease with increasing of water quantity. Reductions in NOx emissions up to 55.6% were obtained after applying DWI to the engine at the compression stroke. The water injection temperature has a little effect on the combustion and emissions of marine engine. The indicated power decreased when the water injection timing in the compression stroke. However, the indicated power increased when the water injection timing in the late combustion phase. The water injection timing in the compression stroke has more potential in reduction NOx emissions. The NOx emissions with water injection in the compression stroke decreased by 40% compared to the value with water injection in the later combustion phase. The ability of DWI and EGR were researched on the solve the trade-off between power and NOx emissions. The results showed that the DWI strategy can reduce NOx emissions at the higher indicated power compared with the results of EGR.

The effect of direct water injection on the combustion stability of a downsized boost engine under high compression ratios and load conditions

Studying the combustion stability of engines equipped with a direct water injection system, especially under high compression ratios and load conditions, is important for realizing the stable operation of downsized boost engines with high thermal efficiency. This study implements a downsized single-cylinder engine with a direct water injection system to systematically investigate the combustion stability under a high compression ratio (CR = 17) and load (IMEP = 9 bar). According to the study results, when the water mass increases, the increase in combustion duration and retardation of the combustion phase at a fixed spark timing lead to more severe fluctuations of cycle-to-cycle variations in the indicated mean effective pressure. This research also indicates that water direct injection advances spark timing to increase power capability while maintaining better combustion stability. It can extend the knock limit spark advance to varying degrees when the water/fuel ratio increases from 0.1 to 0.5. In addition, the coefficient of variation in the indicated mean effective pressure drops to 1.15% with knock limit spark advance when the water/fuel mass ratio is up to 0.5.

Experimental Investigation of the Effect of Direct Water Injection on Combustion, Knock, and Emissions for LPG-Diesel Dual-Fuel Engine

Liquefied petroleum gas (LPG) fuel has a high octane number and high heating value. These features make LPG a rather convenient alternative fuel for spark-ignition engines. On the other hand, using only LPG in diesel engines is not possible due to its low cetane number. However, LPG and diesel can be used in dual-fuel mode, a method that does not require significant modifications in diesel engines. In LPG-diesel dual-fuel mode, nitrogen oxide (NOx) emissions and knock intensity increase due to the rises in cylinder pressure and temperature, depending on LPG combustion and heat release characteristics under high load conditions. In this study, direct water injection with an electronic control method was utilized to reduce NOx and knock intensity in an engine running on LPG-diesel dual-fuel mode under full load conditions. For using LPG in a dual-fuel engine operating under full load without causing any damage, it is determined that the most convenient LPG ratio is 30% at the maximum. The test results obtained using neat diesel fuel are referred to as the standard engine data and are used in the comparisons for better understanding the results obtained. Direct water injection was applied into the engine cylinder at various ratios. During experiments, the ratio of injected water mass to fuel mass consumed in a cycle is set to 60%, 80%, and 100%, respectively. Increases in pressure, temperature, knock intensity, hydrocarbon (HC), and NOx emissions were observed in dual-fuel mode and are presented in comparison with the standard engine data. Consequently, specific fuel consumption, smoke opacity, and CO2 values were significantly reduced. By applying direct water injection and using diesel-LPG dual fuel of 30% LPG, significant improvements in engine performance parameters resulted, and NOx emissions in the dual-fuel condition reduced to lower levels than the standard engine data. Moreover, using direct water injection in dual-fuel mode reduced the increase in the combustion rate of fuel, but this increased the knock intensity.

Effect of Direct Water Injection on Combustion and Performance of Homogeneous Charge Compression Ignition Engine—A Computational Fluid Dynamics Analysis

Effect of Direct Water Injection on Combustion and Performance of Homogeneous Charge Compression Ignition Engine—A Computational Fluid Dynamics Analysis

The effect of direct water injection on a diesel-gasoline reactivity controlled compression ignition engine

Reactivity Controlled Compression Ignition (RCCI) combustion is a promising method to achieve ultra-low nitrogen oxide and soot emissions. However, the main problem of this strategy is the limited operating range, which is mainly caused by high pressure rise rate. In this study, the possibility of using direct water injection as an approach to decrease pressure rise rate is appraised. To that end, a Lagrangian-Eulerian approach is used to simulate a gasoline-diesel RCCI engine with the use of OpenFOAM. The effects of water injection timing and the mass ratio of injected water to diesel fuel on the engine performance are investigated. The study also includes the injection of water into a Homogenous Charge Compression Ignition (HCCI) engine to compare the effect of direct water injection on RCCI and HCCI methods. According to the results, the optimal case with the water injection timing of −10°ATDC and mass ratio of 3 achieves a 29% reduction in maximum pressure rise rate at the cost of a 1.4% decrease in engine power and a 1% increase in overall emissions. Sensitivity analysis shows that direct water injection has the most impact on maximum pressure rise rate and the lowest impact on gross indicated efficiency. A trade-off between maximum pressure rise rate and emissions can be achieved by adjusting spray angle or water injection timing in the RCCI concept. However, in the HCCI strategy, direct water injection invariably results in significantly increasing overall emissions regardless of the spray angle and water injection timing.

Effects of direct water injection on engine performance in a hydrogen (H2)-fueled engine at varied amounts of injected water and water injection timing

In this paper, the effects of direct water injection (WI) on characteristics of combustion and emission for a hydrogen (H2)-fueled spark ignition (SI) engine were experimentally investigated. The experiments conducted under different amounts of water injection (AWI) and varied water injection timing (WIT). The experimental results showed that in-cylinder pressure decreased, indicated thermal efficiency (ITE) increased, and the flame development (CA0-10) and propagation (CA10-90) periods prolonged when AWI raised. When AIW grew to 4.5 mg/cycle, Nitrogen oxides (NOx) expelled from the original engine decreased by 53.7% when excess air ratio (λ) was 1.15. Early WIT had positive effects on the reduction of NOx emissions. When WIT retarded, in-cylinder pressure increased, ITE decreased and CA0-10 and CA10-90 shortened, NOx emissions rapidly increased.

Effects of direct water injection on engine performance in engine fueled with hydrogen at varied excess air ratios and spark timing

In this paper, the effects of direct water injection (WI) on characteristics of combustion and emissions for a hydrogen (H2)-fueled spark ignition (SI) engine were experimentally investigated. The experiments were conducted under different excess air ratios (λ) and ignition timing (IT). In each test, the water to air ratio (α) was varied, and the results were compared with baseline data without WI. The experimental results showed that in-cylinder pressure decreased, indicated thermal efficiency increased, and the flame development and propagation periods prolonged when WI was used. When α increased to 1.87%, NOx emissions expelled from the original engine separately decreased by 36.9% and 55.4% when IT were 5°CA BTDC and 15°CA BTDC at λ of 1.15.

New application to reduce NOx emissions of diesel engines: Electronically controlled direct water injection at compression stroke

In this study, the effect of Direct Water Injection (DWI) on the performance, emissions and combustion was experimentally investigated on a light-duty water-cooled direct injection, diesel engine. Water was injected into the combustion chamber under full load conditions with a dedicated water injector placed on the cylinder head at 10%, 20%, 40%, 60%, 80% and 100% of the fuel by mass, namely W10, W20, W40, W60, W80, W100, respectively. The injection quantity and start of injection in degrees crank angle (°CA) for water injector were controlled by an electronic control unit. Initially, standard engine values were obtained by fueling the engine with diesel fuel for full load condition, and then experiments were repeated at different DWI ratios. Reductions in NOx emissions up to 61% were obtained after applying DWI to the engine during the compression stroke. In addition, considerable improvements were observed in engine performance parameters. It was found out that, engine power increased by 3.7% and specific fuel consumption (SFC) decreased by 4.1%. There were not significant changes in exhaust gas emissions, CO and smoke, while hydrocarbon (HC) emissions increased. Considering all parameters, the optimum condition was obtained forW60-DWI ratio. It was determined that, the water injection performed during compression stroke decreased negative compression and increased cumulative heat release.

Effects of direct water injection and injector configurations on performance and emission characteristics of a gasoline direct injection engine: A computational fluid dynamics analysis

In-cylinder water injection is a promising approach for reducing NOx and soot emissions from internal combustion engines. It allows one to use a higher compression ratio by reducing engine knock; hence, higher fuel economy and power output can be achieved. However, water injection can also affect engine combustion and emission characteristics if water injection and injector parameters are not properly set. Majority of the previous studies on the water injection are done through experiments. Therefore, subtle aspects of water injection such as in-cylinder interaction of water sprays, spatial distribution of water vapor, and effect on flame propagation are not clearly understood and rarely reported in literature due to experimental limitations. Thus, in the present article, a computational fluid dynamics investigation is carried out to analyze the effects of direct water injection under various injector configurations on water evaporation, combustion, performance, and emission characteristics of a gasoline direct injection engine. The emphasis is given to analyze in-cylinder water spray interactions, flame propagation, water spray droplet size distribution, and water vapor spatial distribution inside the engine cylinder. For the study, the water-to-fuel ratio is varied from 0 to 1. Various water injector configurations using nozzle hole diameters of 0.14, 0.179, and 0.205 mm, along with nozzle holes of 4, 5, 6, and 7, are considered for comparison in addition to the case of no_water. Computational fluid dynamics models used in this study are validated with the available data in literature. From the results, it is found that the emission and performance characteristics of the engine are highly dependent on water evaporation characteristics. Also, the water-to-fuel ratio of 0.6 with 6 number of nozzle holes and the nozzle diameter of 0.14 mm results in the highest indicated mean effective pressure and the lowest NOx, soot, and CO emissions compared to other cases considered.

Effect of direct water injection at different crank angles on diesel engine emission and performance

It is well known that in DI diesel engines the formation of NOx is chiefly due to the prevailing high pressure and temperature in the combustion chamber. The methods used for lowering NOx is by induction of water which is blended with diesel oil, which leads to longer delay period, improper combustion and lowered release of thermal energy of fuel thus lowering the efficiency of the engine. In overcoming above problems, a novel approach is proposed in this work in which water is directly injected into the combustion chamber just when the temperature and pressure of gases inside the combustion is about to rise to a peak value. This lowers the formation of NOx very effectively. Adding to this aspect, the water sprayed absorbs heat from the hot gases as well as from the hot metallic surfaces of the combustion chamber and becomes super-heated steam, which augments the pressure built up at a lower temperature. This will help in increasing the power output of the engine. Experiments have been conducted spraying water at different injection timings such as; at 0 degree and at 8 degrees before and after TDC. The quantity of water injected is varied in the ratio of diesel to water from 1:1 to 1:4. The study shows that injection of water before TDC has yielded better results. NOx has reduced by 85 % at 1:4 diesel to water ratio and also injection at 24 degree BTDC. Drop in brake thermal efficiency by 10% to 20% is observed when water ratio is increased from 1:1 to 1:4.

Computational fluid dynamics investigations of the effect of water injection timing on thermal stratification and heat release in thermally stratified compression ignition combustion

Advanced combustion concepts, like homogeneous charge compression ignition, are limited by their narrow operating range, which stems from a lack of control over the heat release process. This study explores a new advanced combustion mode, called thermally stratified compression ignition, which uses a direct water injection event to control the heat release process in low-temperature combustion. A three-dimensional computational fluid dynamics model coupled with detailed chemical kinetics is used to better understand the effects of direct water injection on thermal stratification in the cylinder and the resulting heat release process. Previous results showed that increasing the injection pressure results in a significantly broader temperature distribution due to increased evaporative cooling. In this way, direct water injection can control low-temperature combustion heat release and extend significantly the operable load range. In this study, simulations were performed over a range of start of injection timings in order to determine its effect on thermal stratification and heat release. The results show that for both low and high injection pressures advancing the start of water injection results in increased thermal stratification and reduced peak pressure and heat release rate for injections occurring after −60 °CAD. Before −60 °CAD, advancing the water injection has a varied effect on thermal stratification and heat release depending on the injection pressure and mass of the injected water.

Effect of direct water injection during compression stroke on thermal efficiency optimization of common rail diesel engine

The increasingly strict emissions regulations put forward higher request of NOx emissions control to diesel engines. Water addition is considered to be an effective way to reduce NOx emissions. However, most studies around the world concerned mainly about the effect of water addition on NOx reduction. The effect of water addition on diesel engine efficiency was not paid as much attention as on emissions. A series of experiments were carried out on test bench based on a two cylinder diesel engine with the modifications of adding common rail system and direct water injection system. The effects of direct water injection on diesel combustion and indicated thermal efficiency optimization were studied and the mechanism of thermal efficiency improvement due to compression stroke water injection was revealed. The influences of water injection duration and water injection timing are also studied. Results showed that, compression stroke direct water injection is beneficial to thermal efficiency. Under test conditions up to 4.08% indicated thermal efficiency enhancement is achieved. The thermal efficiency enhancement is mainly attributed to the reduction of negative compression stroke’s work due to the heat absorption of water evaporation and the increment of positive power stroke’s work due to the addition of working fluid. For small water injection duration, earlier injection timing in the compression stroke leads to higher thermal efficiency, while injection at late stage in the compression stroke is more suitable for larger water addition quantity. Thermal efficiency rises at first until reaches its peak value, and then drops with increasing water injection duration. Further increasing water injection duration deteriorates combustion and has negative impact on thermal efficiency. The highest thermal efficiency enhancement is achieved under 0.4ms water injection duration and 180°CA BTDC water injection timing condition.