Pressure Rise Rate Research Articles

Effects of knock intensity measurement technique and fuel chemical composition on the research octane number (RON) of FACE gasolines: Part 2 – Effects of spark timing

The Research and Motor Octane Number (RON, MON) characterize a fuel’s knock resistance by rating the knock intensity of a sample fuel relative to that of Primary Reference Fuels (PRF) in a Cooperative Fuel Research (CFR) Engine. A fuel’s octane number is regulated to prevent damage from autoignition leading to knocking combustion in spark-ignition engines. The operational differences between the standard RON rating and modern engine operation are explored in a three-part publication series. The previous study focused on the effects of lambda and knock characterization. This second study primarily focuses on the effects of spark timing on RON determination. Following the findings from the first publication, the knock intensity was captured by the knockmeter and by the maximum amplitude of pressure oscillations (MAPO) at the lambda of peak knock intensity and stoichiometry. Knock-limited spark advance tests were conducted for a set of seven Fuels for Advanced Combustion Engines (FACE) from the Coordinating Research Council (CRC) with varying chemical composition, PRFs, and Toluene Standardization Fuels (TSFs). For retarded spark timings, pre-spark low-temperature heat release was found for low RON PRFs. Low RON PRFs also showed knocking characteristics before reaching the center of combustion suggesting that the use of knock-limited spark advance (KLSA) was preferred over the knock-limited combustion phasing. Primarily paraffinic fuels tended towards increased pressure oscillations while dominantly aromatic fuels experienced higher pressure rise rates. A MAPO-based KLSA correlated best to Octane Index at a negative K-factor suggesting beyond RON operation despite being at otherwise RON conditions. At stoichiometry, the MAPO-based KLSA did neither correlate to RON nor Octane Index. Good agreement was found between KLSA-based effective RON from this study to the MAPO-based effective RON from the first study.

Experimental study on CO2/CF3I suppression of methane-air explosion and flame propagation

To explore the inhibitory effects of CF3I and CO2 gas on the explosion pressure and flame propagation characteristics of 9.5% methane, a spherical 20 L experimental explosion device was used to study the effect of the gas explosion suppressants on the maximum explosion pressure, maximum explosion pressure rise rate and flame propagation speed of methane. The results indicated that with a gradual increase in the volume fraction of the gas explosion suppressant, the maximum explosion pressure of methane and maximum explosion pressure rise rate gradually decreased, and the time taken to reach the maximum explosion pressure and maximum explosion pressure rise rate was gradually delayed. At the same time, the flame propagation speed gradually decreased. Additionally, the time taken for the flame to reach the edge of the window and the time taken for a crack as well as a cellular structure to appear on the flame surface was gradually delayed. The fluid dynamics uncertainty was suppressed. The explosion pressure and flame propagation processes were markedly suppressed, but the flame buoyancy instability was gradually enhanced. By comparing the effects of the two gas explosion suppressants on the pressure and flame propagation characteristics, it was found that at the same volume fraction, trifluoroiodomethane was significantly better than carbon dioxide in suppressing the explosion of methane. By comparing the reduction rates of the characteristic methane explosion parameters at a volume fraction of 9.5%, it was observed that the inhibitory effect of 4% trifluoroiodomethane on the maximum explosion pressure was approximately 4.6 times that of the same amount of carbon dioxide, and the inhibitory effect of 4% trifluoroiodomethane on the maximum explosion pressure rise rate and flame propagation speed was approximately 2.7 times that of the same amount of carbon dioxide. The addition of 0.5%–1.5% trifluoromethane to 4% and 8% carbon dioxide can improve the explosion suppression efficiency of carbon dioxide. This enhancing phenomenon is a comprehensive manifestation of the oxygen-decreasing effect of carbon dioxide and the trifluoroiodomethane-related endothermic effect and reduction in key free radicals.

Effects of hydrogen addition on combustion and flame propagation characteristics of laser ignited methane/air mixtures

In this study, effects of hydrogen addition on combustion and flame propagation characteristics of methane/air mixtures were investigated in a constant volume combustion chamber. Tested gas mixtures are 100% CH4, 05% H2 – 95% CH4, 10% H2 – 90% CH4 and 15% H2 – 85% CH4, and such mixtures were ignited using a passively Q-switched Nd:YAG laser ignitor which has a pulse energy of 12.3 mJ, pulse duration of 2.4 ns and wave length of 1064 nm. A Schlieren setup coupled with a high-speed camera enabled evaluating flame propagation behavior, while pressure curve analysis provided necessary data for characterization of combustion properties. Additionally, lean flammability limits of gas mixtures were also determined at the test conditions. The unique properties of hydrogen (such as low density, high reactivity, high diffusivity etc) widened lean flammability limit. Rate of pressure rise and measured pressure values increased with hydrogen addition, regardless of the air-fuel equivalence ratio (λ). Lastly, hydrogen addition uniformly affected flame propagation characteristics and flame luminosity. Combustion process became more stable with hydrogen addition.

Explosive properties of selected aerosols determined in a spherical 5-L test chamber

Combustible liquids in the form of aerosols are important for many industrial processes. Therefore the problem of explosion hazards posed by the aerosols becomes increasingly more prominent. To correctly assess the explosion risk and fulfil the requirements of the ATEX directive, it is necessary to obtain information regarding the flammable and explosive properties of the aerosols. Unlike in the case of gases and dusts, no standard procedures aimed at obtaining quantitative information of this type exist. Factors that influence the explosion dynamics of aerosols include: concentration, droplet size, temperature etc. Some of these factors are strongly dependent on the aerosol generation methods. A prototype apparatus was designed and constructed to address that dependence. The apparatus was used in an attempt to determine the basic explosion parameters of liquid flammable aerosols. The device consisted of a 5-L spherical vessel equipped with a pump-injection system that generated aerosols as well as a spark ignition source. A wide variety of injection settings were tested to select the most suitable conditions over a broad range of concentrations and fluid properties. A measurement procedure was developed for operating the device. Prototype tests were carried out with fluids commonly used in industry: isopropanol and kerosene. The tests demonstrated the significant influence of the vessel wall temperature on the result accuracy. Correct temperature control made it possible to obtain relationships between the aerosol concentration and the following explosion parameters: maximum explosion pressure and maximum rate of pressure rise.

Effects of hydrogen mixing ratio on combustion and emissions of natural gas‐diesel dual fuel engine with high natural gas substitution rate

AbstractIn order to explore the feasibility of natural gas (NG)/diesel dual‐fuel engine with high NG substitution rate under medium and low load, the effects of hydrogen (H2) on the performance and emissions of the engine are studied numerically. The baseline engine is a four‐cylinder turbocharged diesel engine, which is modified into a diesel‐Natural Gas‐Hydrogen ternary fuels engine with port‐injected H2 and NG fuels and direct‐injected diesel fuel. The simulation is performed using GT‐Power software, and numerical results are validated with the experimental data. The percentage of diesel fuel is set at 10% and 20% (by energy). The engine speed decreases from high speed to medium speed and finally to low speed. The engine load decreases from medium load to low load. The H2 mixing ratio increases from 10% to 50%. The results show that, with the increase of H2 mixing ratio, the peak cylinder pressure (PCP), the peak cylinder temperature (PCT), the heat release rate (HRR) and the maximum pressure rise rate (MPRR) increase, while the indicated thermal efficiency (ITE) decreases under all working conditions. Among them, the MPRR increases by 4%~13% at medium load and 1%~2% at low load, but it does not exceed 0.6 MPa/ (°) CA. The indicated thermal efficiency decreases by 1%~4% at medium and low load. In terms of emissions, the carbon monoxide (CO) and the hydrocarbons (HC) decrease by 34%~43%, but the nitrogen oxide (NOX) increases by 58%~73%.

Performance optimization of RCCI engines running on landfill gas, propane and hydrogen through the deep neural network and genetic algorithm

The present study is to optimize the performance of the reactivity controlled compression ignition engines taking landfill gas plus propane or hydrogen or a combination of both as low reactivity fuels. A heavy duty, 2.44 L caterpillar 3401E single-cylinder diesel engine is employed for the numerical simulation, and a number of the most effective variables on the engine performance are determined as inputs. The research purposes are to procure the maximum energy efficiency (i.e. the maximum thermodynamics first and second law efficiencies, and the minimum indicated specific fuel consumption), and to fulfill the Euro VI engine emissions standards (i.e. CO, UHC, and NOX maximum emissions 1.5, 0.13, and 0.4 gr/kW-hr, respectively). The maximum peak pressure and peak pressure rise rate are restricted to 150 bar and 10 bar/crank angle deg., respectively. The deep neural networks are utilized to obtain the engine mathematical model and the genetic algorithms are used to attain the intended optimization. Based on the outcomes, injecting a combination of propane and hydrogen to the premixed charge by 3.4 and 6.6 % by volume, respectively, and adopting an engine equivalence ratio of 0.31, an intake pressure of 1.983 bar, and a diesel fuel injection timing of about 75 deg. before the top dead center provide the maximum performance for the considered engine. In the optimized state, a 6.6 % hydrogen by volume takes 2.5 % of the total fuels energy. This research has proven that numerical modeling in combination with deep neural networks and genetic algorithms is an effective methodology to optimize the performance of the reactivity controlled compression ignition engines. Moreover, a dimensional analysis made shows the dimensionless peak pressure is function of the dimensionless engine heat release and the ratio of the engine cumulative heat release to the primary inlet mixture flow work. In the optimized case, the dimensionless ratio of cumulative heat release to the inlet flow work of fluid is 11.5.

Effects of Wobbe Index on the Combustion and Emission Characteristics of a Natural Gas/Diesel RCCI Engine

Abstract Due to energy shortage and environmental problems, the application of natural gas in internal combustion engine has attracted extensive attention. Therefore, diesel pilot ignition natural gas engine is a promising technology. However, the different sources of natural gas lead to the change in composition, which has a great impact on engine combustion and emission. In this study, the relationship between Wobbe index (WI) and swirl ratio (SR) of six different natural gas mixtures was studied by numerical simulation method. Besides, reactivity controlled compression ignition (RCCI) combustion strategy was evaluated. The results showed that increasing the WI increased the in-cylinder pressure and temperature, increased the ignition delay, and shortened the combustion duration, the gross indicated efficiency (GIE) of the six gases exceeded 50%. In addition, the increase of WI increased the nitrogen oxide (NOx) emissions and reduced the hydrocarbon (HC) and carbon monoxide (CO) emissions. Moreover, the peak pressure rise rate (PPRR) increased with the rise of WI, which may lead to engine knock. The results also showed that the increase of SR increased the in-cylinder pressure and temperature and improved the PPRR. When the SR was 0.7 and the WI was 51.7, the combustion and emission performance of the RCCI engine was relatively better.

The study of ignition and emission characteristics of hydrogen-additive hydro-processed renewable diesel

This study was conducted to understand the effects of hydrogen (H2) addition on the combustion and emission characteristics of hydro-processed renewable diesel. Experiments were performed in a constant volume combustion chamber (CVCC) at varying H2 concentrations (0%, 5%, and 10% (by vol.)) relative to air (100%, 95%, and 90% (by vol.)), initial temperatures (Tini) of 600, 650 and 700 K, equivalence ratios (φ) of 0.5, 1.0, and 1.5 and a fixed initial pressure (Pini) of 10 bar. Overall, HRD has lower ignition delay (ID) and total ID. However, H2 addition to HRD delayed the fuel's auto-ignition due to excess H2 oxidation (H2+OHH2O + H) reaction taking place, which turns the chain reactions from branching to propagation, resulting from increasing in ID. Moreover, increasing of H2 concentrations enhanced the maximum pressure rise (Pmax) and heat release rate (HRR), whereas carbon dioxide (CO2) and unburned hydrocarbon (HC) were decreased due to the higher magnitude of the lower heating value of H2 than that of pure HRD. Since H2 itself is a carbon-free molecule, the carbon content of the fuel is reduced. H2 has the characteristics of fast combustion, resulting in a more flammable and complete mixture, which also makes HC emissions to become lower. However, the higher energy density of H2 significantly raises the combustion temperature, and subsequent nitrogen oxides (NOx) were increased. The kinetic modeling predictions revealed that the IDs for HRD-H2 were elongated due to the increased hydroperoxyl (HO2) and hydrogen peroxide (H2O2) mole fractions which led to improved stability.

Combined effect of multi‐injection scheme, injector nozzle bore, and biodiesel blends on combustion and performance characteristics of diesel engine

AbstractMany researchers have conducted extensive experimental and numerical studies to explore the influences of multiple types of fuels. The high demand of energy in the world has led to the growing crisis and depletion of fossil fuels. Therefore, the researchers have focused on investigating renewable energy sources like biodiesel with the aim of suggesting, which energy is more friendly to the environment. Biodiesel has specifications for using it as an alternative fuel to traditional fossil fuels. Whereas, the use of biodiesel fuel in the original design of Diesel engine can emit a higher percentage of nitrogen oxides (NOx). Therefore, to reduce the harmful emissions of the fuel, the injection schemes and injector nozzle bore (INB) of the engine were modified. The present research combines the effect of the nozzle hole diameters and split injection scheme on the performance and combustion parameters of compression ignition (CI) engine was investigated. The engine was fueled with diesel blended of different proportions (Sp20, Sp40, Sp60, and Sp100) of spirulina biodiesel to prove the suitability of this blend as an alternative fuel. The injector nozzle has three injection holes, and the diameter of the three modified holes of the nozzle is changing (from 0.20 to 0.28 mm, step 0.02 mm) along with two types of scheme injection (double and triple). Furthermore, the influence of the direct injection Diesel‐RK model, single‐cylinder, four‐stroke engine; constant compression ratio (17.5:1), engine speed (1500 rpm), and naturally aspired engine at full load condition are studied. A comparison of the present simulation is compared with published results to validate the present simulation model for conventional baseline Diesel for validation. The simulation was done to investigate and present a comparative study with the conventional baseline Diesel engine. The double injection scheme shows a decrease by 1.8%, 1.7%, and 1.9% for parameters of peak cylinder pressure (PCP), peak cylinder temperature (PCT), and maximum rate of pressure rise, respectively. Whereas, the specific fuel consumption (SFC) and break thermal efficiency are increased by 8.7% and 9.33%, respectively. The results showed a reduction by 2.1%, 20.5%, 22.1%, and 3.2% in PCP, PCT, maximum rate of pressure rise, and break thermal efficiency, respectively. Moreover, the SFC is increased by 3.1% with the modified INB 0.28 (mm).

Correlation between concentration, droplet size, turbulent intensity and explosion parameters of gas-liquid two-phase mixture

In this study, concentration and droplet size of aerosol and turbulence distribution in the 20 L vessel over time under pneumatic pressure of 1 MPa–2MPa were observed and correlation between actual concentration, droplet size, turbulent intensity of the ethanol aerosol and pneumatic pressure were analyzed. The effect of concentration, droplet size, and turbulent intensity on aerosol explosion parameters of the ethanol aerosol were examined. The actual concentration of ethanol aerosol in the vessel is much lower than the design concentration. The ratio between the actual concentration and the designed concentration is about 65%–90% at the pneumatic pressure from 1.0 MPa to 2.0 MPa. The concentration of ethanol aerosol in the vessel increases with time from 0 ms to 50 ms, maintains a stead state from 50 ms to 100 ms and decreases gradually after 100 ms. In the initial stage of injecting, the size of aerosol droplets in the vessel changes with time sharply and tends to constant at 50 ms. The turbulence intensity from 10sm to 50 ms is higher and decreases rapidly from 50 ms to 100 ms. The effect of the pneumatic pressure on the maximum rate of explosion pressure rise of ethanol aerosol is much higher than that on the peak explosion pressure. The maximum rate of explosion pressure rise of the ethanol aerosol is lower than that of ethanol vapor/air. The explosion index of ethanol vapor/air is higher than that of ethanol aerosol. Ethanol vapor/air has a higher explosion hazard, compared with ethanol aerosol with the same concentration.

Numerical Optimization of Spray-Guided Spark Assistance for Cold Idle Operation in a Heavy-Duty Gasoline Compression Ignition Engine

This article describes the results of a response surface model (RSM)-based numerical optimization campaign for spray-guided spark assistance at cold operations in a heavy-duty gasoline compression ignition (GCI) engine. On the basis of an earlier work on spark-assisted GCI cold combustion, a space-filling design of experiments (DoE) method was first undertaken to investigate a multitude of hardware design variables and engine operating parameters. The main design variables included the number of injector nozzles, fuel split quantities and injection timings, and spark timing. The objective variables were engine combustion efficiency (ŋc), maximum pressure rise rate (MPRR), and engine-out nitrogen oxide (NOx) emissions. A total of 150 design candidates were automatically generated using the Sobol sequence method provided by the commercial software package, CAESES. Then, closed-cycle computational fluid dynamic (CFD) spark-assisted GCI simulations under cold idling operations were performed. The outcomes from the CFD-DoE design campaign were utilized to construct high-fidelity RSMs that allowed for further design optimization of the spark plug- and fuel injector-related design variables, along with fuel injection strategy parameters. A merit function with respect to objective variables was formulated with an appropriate weight assignment on each objective variable. Finally, the best design candidate was identified from the RSM-based optimization process and further validated in the CFD analysis. The best design candidate showed the potential to significantly improve combustion efficiency (ŋc > 90%) over the baseline at cold idle while satisfying MPRR and NOx emissions constraints (MPRR < 5 bar/CAD and NOx < 4.5 g/kWh).

Investigation of the explosion characteristics of ethylene-air premixed gas in flameproof enclosures by using numerical simulations

Flameproof enclosures are widely installed as safety equipment at dangerous industrial sites to reduce ignition risks. However, electrical components typical?ly installed in such flameproof enclosures for the production process can cause ignition and compromise the safety of the enclosures. Thus, in such cases, the explosive characteristics of the flameproof enclosures is severely affected. Acci?dental gas explosions in industrial sites rarely occur under standard operating conditions. Premixed gas explosions in flameproof shells are complex processes. A 560 mm ? 400 mm ? 280 mm flameproof enclosure commonly used in industrial sites was used to investigate the phenomenon. The explosion characteristics of eth?ylene-air premixed gas in the flameproof enclosure was simulated using FLUENT software to investigate the influences of ignition source location, ignition source energy, ambient temperature, and obstacles on the maximum explosion pressure, maximum explosion pressure rise rate, and maximum explosion index of the flame?proof enclosure. The results revealed that the surface area of heat exchange con?siderably influences the maximum explosion pressure of the flameproof enclosure. The larger the ignition energy is, the larger the maximum explosion pressure value, the maximum rate of explosion pressure rise, and the maximum explosion index of the flameproof enclosure are. With the increase in the ambient temperature, the maximum explosion pressure decreased, whereas the maximum rate of explosion pressure rise and the maximum explosion index exhibited limited change. The re?sults of this study provide theoretical guidance for the design and suppression of flameproof enclosures.

Closed-loop Control of SI←→RCCI Mode Transitions in a Multi-Mode Combustion Engine

The primary barrier to implementing the RCCI mode in on-road vehicles is its limited operating range due to excessive pressure rise rates and complexity of combustion control during mode switching. The feasible operating range of the RCCI mode is only a subset of the speed-load range of conventional spark ignition (SI) engines. Therefore, a multi-mode engine concept operating in RCCI and SI modes can cover required engine operating range and can improve engine performance in terms of thermal efficiency and emissions. The goal of this study is to develop a model-based closed loop control of an SI-RCCI multi-mode engine. To this end, a gain scheduled model predictive controller (MPC) is developed for SI-RCCI-SI mode switching. A Kalman filter is designed for state estimations. The control architecture includes; a supervisory controller that determines the optimal operating mode based on the requested engine load and speed, and gain scheduled MPC and a Kalman filter. The controller performance is validated on a 2-liter multi-mode engine for SI-RCCI-SI mode switching at different engine loads (NMEP) and combustion phasings (CA50). The controller is capable of tracking NMEP and CA50 in both modes and during mode transitions while maintaining air-fuel ratio near stoichiometry in SI mode and constraining the maximum pressure rise rate (MPRR) below 8 bar/CAD in the RCCI mode.

Исследование особенностей зажигания и горения высокоплотных зарядов в условиях постоянного объема

The study of combustion and ignition of charges with promising propellants or powder compositions in terms of initial conditions is an urgent problem of modern ballistics. Generally, combustion and ignition of charges are tested in a manometric closed vessel. The charge ignition conditions may affect the subsequent reactions. When designing a shot with a new charge, it is necessary to know what determines the moment of ignition (gas pressure, time, pressure rise rate, type of igniter, etc.) and which factor has a greater effect on the ignition. This paper presents a study of some features of high-density charge ignition under constant volume conditions. A brief description of the manometric setup is given. The effect of mass and type of igniter and combustion surface area on the high-density charge ignition and subsequent combustion is studied. The pressure-time dependences corresponding to high-density charge combustion in a textolite container with different diameters are presented and analyzed. The ignition of the paste high-density charge is revealed to be affected by the geometric dimensions of the container. The parametric experimental study results show that the ignition conditions of a model high-density propellant (MHDP) strongly depend on the method of initiation, namely the number of burning particles and ambient pressure; however, these factors do not affect the dependence of the MHDP combustion rate on pressure. The ignition momentum is obtained as a function of the ratio of the container burning surface circumference to the burning surface area.

S-37-1: PROGNOSTIC UTILITY OF MORNING BLOOD PRESSURE SURGE

Morning blood pressure surge (MBPS), defined as the difference between morning systolic blood pressure and the lowest nighttime systolic blood pressure, is a normal physiological phenomenon of diurnal blood pressure variability (BPV). Exaggerated MBPS is associated with morning hypertension and has been associated with adverse cardiovascular and cerebrovascular events, especially hemorrhagic stroke. However, MBPS has low reproducibility and there is an ethnic difference in the amplitude of MBPS and its prognostic value. More evidence is needed to prove its clinical usefulness in the management of hypertension. Since the risk of MBPS is mainly attributable to the elevated morning blood pressure, the focus therefore has shifted from MBPS to the control of morning hypertension. Because MBPS focuses only on the amplitude rather than the rate of blood pressure rise, we calculated the MBPS rate as the slope of linear regression of sequential systolic blood pressure measures on the time intervals within the MBPS period. We found the reproducibility for the MBPS rate was better than the MBPS amplitude. The MBPS rate was a more sensitive and reliable prognostic factor of long term mortality than the MBPS amplitude. The prognostic values of MBPS rate were comparable in subjects with or without morning and nocturnal hypertension. Because the MBPS rate can easily be calculated from the ambulatory blood pressure monitoring data, it could become a routine parameter in daily practice in conjunction with other routinely derived parameters including MBPS amplitude.

Experimental investigation and Artificial Neural Network modelling of combustion pressure parameters of dual spark plug SI engine

Shortages of petroleum-based fuels due to their rapid consumption rate and their environmental degradation motivates researchers to develop new technologies for the efficient use of petroleum-based fuels as well as the use of environmentally friendly alternate biofuels. Ethanol is one of the promising alternative biofuels for spark ignition (SI) engines. Currently, the Indian union Government aims to mix 20% ethanol by 2030. Therefore, extensive research studies are needed to determine the combustion stability of E20 blend. The purpose of this study was to investigate the combustion pressure fluctuations is dual plug SI engine using ethanol-gasoline blends and to develop Artificial neural network model using back propagation algorithm for the prediction of these fluctuations. The fluctuations of Indicated mean effective pressure (IMEP), maximum cylinder pressure and maximum rate of pressure rise has been measured by conducting experiment in a dual spark plug SI engine under different compression ratios and spark ignition timings using E5, E10, E15 and E20. Then, these experimental data’s have been used for training and testing of BP model to predict the combustion pressure parameters. The % load, blend ratio, compression ratio and spark timings were used as the input parameters whereas IMEP, maximum cylinder pressure and maximum rate of pressure rise were used as the output parameters of the model. The experimental results showed that E20 achieved maximum average IMEP and minimum COVIMEP at a compression ratio of 10:1 and ignition timings of 24° bTDC. The modelling results showed that BP model is capable of predicting the combustion pressure fluctuations with good accuracy.

Cyclic Combustion Variability of Dimethyl-Ether-Fueled Agricultural Tractor Engine

Abstract Combustion in dimethyl-ether (DME)-fueled engines needs to be assessed carefully for its widespread acceptability from a drivability viewpoint. Since the test engine used in an off-highway segment, it was tested in a steady-state cycle for engine performance, combustion, emissions, and their cyclic variations, which were the only parameters to assess the drivability. This study investigated and analyzed the cyclic variations of a 100% DME-fueled engine equipped with modified mechanical fuel injection equipment. It was compared with baseline diesel to understand its positive and negative aspects. Experiments were conducted at different engine speeds (1200,1600, and 2000 rpm) and loads (No Load, 1.29, 2.59, 3.88, 5.18, and 6.47 bar brake mean effective pressure (BMEP)) . In-cylinder pressure was recorded for 250 consecutive engine cycles, and many combustion parameters were comparatively analyzed for diesel and DME fuelings. The coefficient of variation (COV) of maximum in-cylinder pressure (Pmax) was lower for DME than diesel at 1600 rpm and comparable at the other remaining engine speeds (1200 and 2000 rpm). Variations in COV of Pmax were higher at low loads and negligible at high loads for both test fuels. At 2000 rpm, the crank angle positions at which Pmax occurred were distributed in a narrow range for DME, representing higher combustion stability than baseline diesel. Variations in the maximum rate of pressure rise (RoPRmax) were lower for DME at 3.88 and 6.47 bar BMEP, while these were higher at 1.29 bar BMEP than baseline diesel. COV of indicated mean effective pressure (COVIMEP) decreased from lower to higher loads for diesel and DME fueling at 1600 and 2000 rpm engine speeds. The differences in COVIMEP between diesel and DME were negligible at higher loads, representing engine stability similar to baseline diesel. Combustion parameters assessed indicated that DME fueling led to lower cyclic variations than baseline diesel as the engine operated from lower to higher loads. At lower loads, DME fueling showed higher cyclic variations than baseline diesel.

Study on Effect and Mechanism of Pressure Rise Rate on the Bursting Pressure of Conventional Domed Bursting Disc

Study on Effect and Mechanism of Pressure Rise Rate on the Bursting Pressure of Conventional Domed Bursting Disc

Understanding the performance, emissions, and combustion behaviors of a DI diesel engine using alcohol/hemp seed oil biodiesel/diesel fuel ternary blends: Influence of long-chain alcohol type and concentration

In this study, it was aimed to examine the influences of biodiesel–diesel-higher alcohol (1-pentanol, 1-hexanol, and 1-heptanol) blends on the performance, emission and combustion behaviors of a single-cylinder diesel engine. The tests were performed at a fixed speed of 1500 rpm and variable loads (25%, 50%, 75%, and 100%). For the tests, 80% diesel and 20% hemp seed oil biodiesel were blended and called as B20. Biodiesel fuel was produced by transesterification from hemp seed oil in the presence of methanol and potassium hydroxide for the preparation of B20 binary test fuel and other ternary fuels. Furthermore, nine ternary blend fuels [20% HSOB + 70%, 60% and 50% diesel, respectively + 10%, 20% and 30% higher alcohol (pentanol, hexanol and heptanol) respectively] were prepared. The calculations made with the experimental data revealed that the minimum brake specific energy consumption values were 12,48 MJ/kW h, 13,06 MJ/kW h, 13,27 MJ/kW h, 13,35 MJ/kW h, 13,47 MJ/kW h, and 13,59 MJ/kW h, respectively, for diesel fuel at full load, for fuels B20, B20Hx10, B20Hp10, B20Hx20 and B20Pe10, the maximum brake thermal efficiency values were obtained as 28.85%, 27.56%, 27.14%, 26.97%, 26.73% and 26.49%, respectively, for the same fuels at the same load. The increment in higher alcohol concentration in the blend delayed start of combustion and therefore the ignition delay period was prolonged. In the fuel line pressure data, changes were observed depending on the amount, viscosity and density of the fuel. Furthermore, B20Hx10 and B20Hp10 fuels gave the maximum in-cylinder pressure, heat release rate, average gas temperature and pressure rise rate values after diesel and biodiesel. The addition of biodiesel and higher alcohol to diesel fuel resulted in a decrease in NOX, CO and unburned HC and smoke emissions and an increase in CO2. NOX, CO and unburned HC values of higher alcohol blended fuels at full load showed lower results, between 3.04–22.24%, 22.85–56.35% and 5.44–22.83%, respectively, compared to diesel fuel. It can be concluded that the use of hemp seed oil biodiesel and higher alcohol in the diesel engine will make a significant contribution to the reduction of NOX emissions.

Recent Studies on Alternative Fuel of Dimethyl Ether

With the development of industrialization, a large number of non-renewable fuels (such as coal and crude oil) are consumed, and the harmful substances produced in the combustion process of a large number of fossil fuels have caused serious pollution to the atmosphere, and the harmful gases produced by combustion have caused disastrous damage to the ecological balance. Therefore, finding clean energy and exploring alternative fuels are very important in today's society. This paper mainly reviews the studies on the alternative fuels of dimethyl ether (DME). Firstly, the types of alternative fuels currently researched by society and their respective advantages and disadvantages are analyzed, and the preparation of dimethyl ether and its advantages and disadvantages are analyzed in detail. In addition, the physicochemical properties, combustion and emission characteristics of dimethyl ether and diesel are compared and analyzed. The conclusion is that the injection delay angle of dimethyl ether is larger than that of diesel, the ignition delay period is shorter than that of diesel, and the maximum explosion pressure, maximum pressure rise rate and combustion noise of dimethyl ether are lower than that of diesel. The diffusion combustion speed of DME is faster than that of diesel, and the combustion duration is shorter than that of diesel. At the same time, as an alternative energy, dimethyl ether engine has a significant reduction in NOx emission, a very low level of HC and CO emission, and zero soot emission. In conclusion, the DME engine has good performance and emission characteristics.