Maximum Cylinder Pressure Research Articles

Effect of parallel LPG fuelling in a methanol fuelled SI engine under variable compression ratio

In the present experimental study, five LPG fractions from 25% to 45% based on total energy are tested in a methanol fuelled SI engine at compression ratios (CR) varying from 12 to 15. Results are affirmative towards methanol/LPG dual fuel. The brake power, brake thermal efficiency, and volumetric efficiency are found to increase by 51%, 21.2%, and 13% respectively by changing from 25% LPG fraction at CR12 to 45% LPG fraction at CR15. The flame development period is found to decrease with CR and LPG, while the flame propagation period and total combustion duration are found to decrease with CR but increase with LPG. The maximum cylinder pressure and net heat release rate are found to increase by 101% and 27.8% respectively and advanced. CO emissions are found to decrease with CR while increase with LPG fraction. HC is found to decrease with LPG as well as CR. CO2 emissions are found to increase continuously with increasing LPG fractions and CR. The NOx emissions are also found to increase explicitly with LPG and CR, a net 209% increase in it is found 25% LPG at CR 12–45% LPG at CR15.

Comparative evaluation of the combustion process and emissions of a diesel engine operating on the cetane improver 2-Ethylhexyl nitrate doped rapeseed oil and aviation JP-8 fuel

• Diesel engine tested with rapeseed oil (RO) and jet fuel (JF) at 1400 and 2200 rpm. • 2-EHN is more active in reducing the ignition delay of JF rather than RO at both rpm. • MBF 50 and MBF 90 are smaller, but the ITE is a bit lower with the doped JF-24 fuel. • NO x is 49% higher, but smoke 27% lower with doped RO-30 than with JF-24 at 2200 rpm. • The combustion of JF-fuel-sets emits THC less than RO-sets at a speed of 2200 rpm. Rapeseed oil (RO) and JP-8 fuel (JF) as alternatives could be used as diesel fuel supplements in many power sectors however, the low cetane number related drawbacks should be removed to overcome the difficulties in the ignition and to achieve efficient-clean combustion of the fuels. The purpose of the research is to make a comparative evaluation of the cetane enhancer-made effects on the combustion process, cyclic variability, thermal efficiency, smoke, and exhaust emissions. At first, a naturally aspirated engine operated with the undoped RO and JF to identify the baseline parameters for full (100%) loads corresponding to Indicated Mean Effective Pressures (IMEP) of 0.844 and 0.738 MPa at speeds of 1400 and 2200 rpm. Then, the engine operated with the 2-EHN doped fuels 0.10 (RO-10), 0.30 (RO-30) and 10 (JF-10), 24 vol% (JF-24) to get new results needed for comparative evaluation of the benefits and detriments in the combustion process, engine efficiency, smoke, and emissions. The ignition delay was 10.3% and 44.6% shorter, the Indicated Thermal Efficiency (ITE) was 6.1% higher and 1.2% lower, the NO x emissions were a little and 10.3% lower with the doped RO-30 and JF-24 at a speed of 2200 rpm. The coefficients of cyclic variations (COVs) of the IMEP were 9.7% higher and 11.8% lower, the in-cylinder maximum pressure was 22.5% and 29.0% lower, and the increment rate of maximum pressure was 13.5% and 14.9% lower, respectively. Also, RO-30, JF-24 fuels suggested smoke opacity and CO emissions 42.1%, 32.1% and 11.6%, 2.7% higher, THC emissions 1.9 times higher, and 28.6% lower for engine tested conditions.

The influence of hydrogen addition on the combustion characteristics of a common-rail CI engine fueled with waste cooking oil biodiesel/diesel blends

In this study, the effect of hydrogen assisted intake air on combustion characteristics of a diesel fuel-waste cooking oil biodiesel (WCOB) blend fueled CI engine has been extensively studied. While the diesel and B25 (75% diesel fuel+25% WCOB) fuels used as the main fuel were sprayed directly into the cylinder, the hydrogen, the secondary fuel was mixed with the intake air at 10, 20, 30 and 40 lpm flow rates and taken into the cylinder. The maximum in-cylinder pressure (CP) values decreased with B25 fuel compared to diesel fuel. But B25‑hydrogen dual-fuel mode operation exhibited higher maxium CP and RoPR value according to diesel fuel. It was seen that hydrogen has a more significant effect on premixed pilot fuel combustion phase compared to the diffusion combustion phase. It was observed that the combustion duration (CD) of neat B25 fuel lower than that of diesel fuel, generally. In case of B25‑hydrogen dual-fuel mode operation, CD increased depending on increasing hydrogen addition rate. It was seen that hydrogen enrichment has no adverse effect on ringing intensity (RI).

Limits of compression ratio in spark-ignition combustion with methanol

A shift toward a circular and [Formula: see text]-neutral world is required, in which rapid defossilization and lower emissions are realized. A promising alternative fuel that has gained traction is methanol, thanks to its favorable and clean-burning fuel properties as well as its ability to be produced in a carbon-neutral process. Especially methanol’s high knock resistance and its combustion stability offer the opportunity to operate an engine at both a high compression ratio and a high excess air dilution. Although methanol has been investigated in series-production engines for passenger car applications, there is a lack of investigations on a dedicated engine that can operate at methanol’s knock limit. In this paper, methanol’s knock limitation is experimentally assessed by applying high compression ratios to a direct injection spark-ignition single-cylinder research engine. To that end, four compression ratios were investigated: 10.8, 15.0, 17.7, and 20.6. With compression ratios of 15.0 and 17.7, the lean-limit was increased to excess air ratios of 2.0 and 2.1, respectively, compared to 1.7 at a compression ratio of 10.8. For the highest compression ratio of 20.6, the maximum lean burn limit was increased to an excess air ratio of 1.9 due to achieving the maximum cylinder pressure limit. Despite the minor increase in lean-limit, a maximum indicated efficiency of 48.7% was achieved with the highest compression ratio of 20.6. However, even at this high compression ratio, methanol did not show a knock limitation. The investigations in this work provide profound knowledge for future engine investigations with methanol.

Development and Experimental Validation of an Adaptive, Piston-Damage-Based Combustion Control System for SI Engines: Part 2—Implementation of Adaptive Strategies

This work focuses on the implementation of innovative adaptive strategies and a closed-loop chain in a piston-damage-based combustion controller. In the previous paper (Part 1), implemented models and the open loop algorithm are described and validated by reproducing some vehicle maneuvers at the engine test cell. Such controller is further improved by implementing self-learning algorithms based on the analytical formulations of knock and the combustion model, to update the fuel Research Octane Number (RON) and the relationship between the combustion phase and the spark timing in real-time. These strategies are based on the availability of an on-board indicating system for the estimation of both the knock intensity and the combustion phase index. The equations used to develop the adaptive strategies are described in detail. A closed-loop chain is then added, and the complete controller is finally implemented in a Rapid Control Prototyping (RCP) device. The controller is validated with specific tests defined to verify the robustness and the accuracy of the adaptive strategies. Results of the online validation process are presented in the last part of the paper and the accuracy of the complete controller is finally demonstrated. Indeed, error between the cyclic and the target combustion phase index is within the range ±0.5 Crank Angle degrees (°CA), while the error between the measured and the calculated maximum in-cylinder pressure is included in the range ±5 bar, even when fuel RON or spark advance map is changing.

Effects of Water Injection Strategies on Oxy-Fuel Combustion Characteristics of a Dual-Injection Spark Ignition Engine

Currently, global warming has been a serious issue, which is closely related to anthropogenic emission of Greenhouse Gas (GHG) in the atmosphere, particularly Carbon Dioxide (CO2). To help achieve carbon neutrality by decreasing CO2 emissions, Oxy-Fuel Combustion (OFC) technology is becoming a hot topic in recent years. However, few findings have been reported about the implementation of OFC in dual-injection Spark Ignition (SI) engines. This work numerically explores the effects of Water Injection (WI) strategies on OFC characteristics in a practical dual-injection engine, including GDI (only using GDI), P50-G50 (50% PFI and 50% GDI) and PFI (only using PFI). The findings will help build a conceptual and theoretical foundation for the implementation of OFC technology in dual-injection SI engines, as well as exploring a solution to increase engine efficiency. The results show that compared to Conventional Air Combustion (CAC), there is a significant increase in BSFC under OFC. Ignition delay (θF) is significantly prolonged, and the spark timing is obviously advanced. Combustion duration (θC) of PFI is a bit shorter than that of GDI and P50-G50. There is a small benefit to BSFC under a low water-fuel mass ratio (Rwf). However, with the further increase of Rwf from 0.2 to 0.9, there is an increment of 4.29%, 3.6% and 3.77% in BSFC for GDI, P50-G50 and PFI, respectively. As WI timing (tWI) postpones to around −30 °CA under the conditions of Rwf ≥ 0.8, BSFC has a sharp decrease of more than 6 g/kWh, and this decline is more evident under GDI injection strategy. The variation of maximum cylinder pressure (Pmax) and combustion phasing is less affected by WI temperature (TWI) compared to the effects of Rwf or tWI. BSFC just has a small decline with the increase of TWI from 298 K to 368 K regardless of the injection strategy. Consequently, appropriate WI strategies are beneficial to OFC combustion in a dual-injection SI engine, but the benefit in fuel economy is limited.

Prediction of emission and performance characteristics of reactivity-controlled compression ignition engine with the intelligent software based on adaptive neural-fuzzy and neural-network

A fuel reactivity-controlled compression ignition concept promises to overcome increasingly stringent emission standards with ultra-low nitrogen oxide and soot emissions and very high fuel efficiency. In the present work, it was developed an intelligent software-based on adaptive neural-fuzzy inference systems in order to predict the emission and performance values of reactivity-controlled compression ignition engine fueled with natural gas and diesel under different operating conditions through an experimentally validated computational fluid dynamics model with the four cases generated in the study for intelligent software-based on neural-fuzzy systems simulation considering different input and output parameters. The engine model was run at input variables as initial pressure (1.67–2.79 bar), total fuel mass (60–130 mg), exhaust gas recirculation ratio (0–20%), the start of injection (32–56° before top dead center) and total 180 different conditions were generated while output responses such as indicated power, maximum in-cylinder pressure, soot, and nitrogen oxide emissions. The main operating parameters of the reactivity-controlled compression ignition engine were determined for different load conditions, enabling the engine to operate in a wide range with high efficiency and low emission. For the neural-fuzzy inference model presented study, the different number Gaussian curve membership functions (5, 6, 7, 8) (gaussmf) have been used considering different adaptive neural-fuzzy cases, and generally, about 13500 training cycles is found to be optimum neural-fuzzy inference parameters and minimum error value. Mean square error, mean error percentage, and the absolute fraction of variance (R2) were used to assess and compare the performance of the adaptive neural-fuzzy and artificial neural network. Results of the adaptive neural-fuzzy confirm that the model successfully predicts the performance and emission of the engine with the R2 value % 99.8, %99.9, and %96.5 for the output parameters indicated power, maximum in-cylinder pressure, and nitrogen oxide, respectively. Moreover, the performance of the neural-fuzzy inference algorithm compared with artificial neural network and consequently, it was observed that neural-fuzzy inference gives more accurate predict value according to the artificial neural network. Moreover, generating a neural-fuzzy inference architecture using the proposed mathematical foundation given the study shows that neural-fuzzy inference is a very effective and helpful technique to predict the reactivity-controlled compression ignition engine performance and emission parameters.

Research on starting process and control strategy of opposed-piston free-piston engine generator _ Simulation and test results

The operation process of free-piston engine generator (FPEG) can be divided into starting process and power generation process, and each of them faces severe challenges especially for the opposed-piston FPEG. As the first part of the investigation, this paper focuses the starting process of opposed piston FPEG. Two novel general methods to start the opposed-piston FPEG are investigated by the linear electric machine operating as linear motor. Both simulation and test results are presented, and the numerical model is successfully validated. The test results show that the maximum in-cylinder pressure of the engine cylinder is 11.85bar, indicating that the engine is ready for ignition, and the synchronization error of opposed-piston fluctuates within ± 2 mm with the limitation of the synchronization mechanism Further investigations on the opposed-piston scheme performance with the displacement master–slave control strategy and current master–slave control strategy are carried out. The results demonstrate that both control strategies are feasible to start the opposed-piston FPEG. More importantly, the current master–slave control strategy has faster response to external interference and therefore the piston synchronization error is smaller. And the smaller motor force of the current master–slave control strategy makes the peak in-cylinder pressure reach the target value. Further research shows that the mass of moving parts, constant motor force and the synchronization mechanism are crucial factors for such schematic prototype during starting process.

PERFORMANCE ASSESSMENT OF A LARGE INTERNAL COMBUSTION ENGINE DUE TO INLET AIR COOLING AND DEHUMIDIFICATION: GT-POWER SOFTWARE SIMULATION

Large internal combustion engines (ICEs) performance is limited by knocking phenomenon due to harsh ambient conditions such as hot temperature and excessive humidity. The performance of these engines can be enhanced by cooling and dehumidifying the inlet air on turbocharger upstream under safe operation conditions through a cooling coil heat exchanger, hence, increasing the power output as well as reducing the brake specific fuel consumption and pollutant specific emissions. Analysis have been performed in the GT-POWER software through a 1-D thermodynamic modelling of the Wärtsilä W20V34SG engine, making it possible to verify the influence of cooled and dehumidified ambient air, considering a temperature range from 9.5°C (282.7 K) to 15.5°C (288.7 K), while keeping 1 bar for pressure and relative humidity of 100%. Furthermore, the brake mean effective pressure (BMEP) has been set from 20 to 23.45 bar with a step of 1.15 bar. Such simulations are aimed to find the maximum air temperature at the cooling coil outlet in which the average of maximum cylinder pressures does not exceed the safety limit pressure of 186 bar while maintaining control on the wastegate valve. As a result, it was possible to evaluate that the maximum temperature to be chosen, under the conditions already mentioned, should be lower than 13.8°C (287 K).

Experimental study on the cyclic variations of ethanol/diesel reactivity controlled compression ignition (RCCI) combustion in a heavy-duty diesel engine

The current work was performed to study the cyclic variations of ethanol/diesel reactivity controlled compression ignition (RCCI) combustion on a heavy-duty diesel engine. The effects of diesel injection timing and premixed ratio (PR) on the cyclic variations were researched. Several parameters such as the maximum in-cylinder pressure (Pmax), the maximum heat release rate (HRRmax), the maximum pressure rise rate (PRRmax) and the indicated mean effective pressure (IMEP) were employed to evaluate the cyclic variations by using the coefficient of variation (COV) of each parameter. The results show that the cyclic variations of ethanol/diesel RCCI combustion are sensitive to the diesel injection timing and PR. with advance of diesel injection timing, the COVs of all parameters decrease at first and then increase, the frequency distribution of all parameters firstly becomes more concentrated and then gets more dispersed, the distribution ranges of the crank angle of Pmax, HRRmax, PRRmax are narrowed firstly and then widened. With increment of PR, the COVs of all parameters firstly decrease and then increase, the frequency distribution of all parameters firstly becomes more concentrated and then gets more dispersed. The results of this work reveal that diesel injection timing and PR should be optimized to achieve smaller cyclic variation and more smooth operation of ethanol/diesel RCCI engine.

Combustion and emission characteristics of an Acetone-Butanol-Ethanol (ABE) spark ignition engine with hydrogen direct injection

Butanol could reduce emissions and alleviate the energy crisis as a bio-fuel used on engines, but the production cost problem limits the application of butanol. During the butanol production, ABE (Acetone-Butanol-Ethanol) is a critical intermediate product. Many studies researched the direct application of ABE on engines instead of butanol to solve the production cost problem of butanol. ABE has the defects of large ignition energy and vaporization heat. Hydrogen is a gaseous fuel with small ignition energy and high flame temperature. In this research, ABE port injection combines with hydrogen direct injection, forming a stratified state of the hydrogen-rich mixture around the spark plug. The engine speed is 1500 rpm, and λ is 1. Five αH2 (hydrogen blending fractions: 0, 5%, 10%, 15%, 20%) and five spark timings (5°, 10°, 15°, 20°, 25° CA BTDC) are studied to observe the effects of them on combustion and emissions of the test engine. The results show that hydrogen addition increases the maximum cylinder pressure and maximum heat release rate, increases the maximum cylinder temperature and IMEP, but the exhaust temperature decreases. The flame development period and flame propagation period shorten after adding hydrogen. Hydrogen addition improves HC and CO emissions but increases NOx emissions. Particle emissions decrease distinctly after hydrogen addition. Hydrogen changes the combustion properties of ABE and improves the test engine's power and emissions. The combustion in the cylinder becomes better with the increase of αH2, but a further increase in αH2 beyond 5% brings minor improvements on combustion.

Effect of fuel opening injection pressure and injection timing of hydrogen enriched rice bran biodiesel fuelled in CI engine

Fuel opening injection pressure and injection timing are important injection parameters, and they have a significant influence on engine combustion, performance, and emissions. The focus of this work is to improve the performance and emissions of single-cylinder diesel engines by using injection parameters in engines running with rice bran biodiesel 10% blend (RB10+H₂) and 20% blend (RB20+H₂) with a fixed hydrogen flow rate of 7 lpm. In addition, hydrogen and biodiesel are excellent alternatives to conventional fuels, which can reduce energy consumption and strict emission standards. The investigation is conducted for three different opening injection pressure of 220, 240, 260 bar, and four different injection timings of 20°, 22°, 24°, and 26° bTDC. Results indicate that the sample ‘RB10+H₂’ provides 3.32% higher BTE and reduces the fuel consumption by 13% as diesel fuel. The blend RB10+H₂ attributes a maximum cylinder pressure of 68.7 bar and a peak HRR value of 49 J/ºCA. Further, compared to diesel, RB10+H₂ blend emits lower CO, HC, and smoke opacity by 17%, 22%, and 16%, respectively. However, an almost 12% increase of nitrogen oxides for the RB10+H₂ blend is observed. However, with advanced injection timing and higher opening injection pressure, NOx emissions is slightly increased.

Comparative assessment of performance, combustion, and emission of compression ignition engine fuelled with different generations of biodiesel

ABSTRACT In the present research work, the performance, combustion and emission characteristics of compression ignition engine fuelled 22 different biodiesels categorised as (first, second, third generation, waste oil, and animal oil) biodiesel (B100) are evaluated numerically and compared with diesel fuel. Diesel-RK, a full-thermodynamic cycle engine analysis tool was used to carry out the numerical analysis. The engine power, fuel consumption, ignition delay, maximum cylinder pressure, oxides of nitrogen (NOx), and carbon dioxide (CO2) emission were investigated at four different engine operating loads. Power output was observed to be higher for Corn oil biodiesel, while Jatropha oil biodiesel produced lower fuel consumption among all other biodiesel. 9.1% increase in-cylinder peak pressure was found for waste transformer oil biodiesel than diesel, while ignition delay was found to be lowest for Rapeseed oil BD, Rice bran oil BD among all other biodiesel. The NOx emissions were higher for biodiesel by 30–32%, while CO2 emissions were reduced by 10–12% compared to diesel. The physicochemical properties of biodiesel were responsible for the diverse characteristics of the engine.

Effect of toluene addition to waste cooking oil on combustion characteristics of a ci engine

In recent years, significant emphasis has been placed on biodiesel as a renewable and environmentally friendly fuel. However, biodiesel production costs are still higher than commercial diesel fuel and it requires a lot of time and effort. In this study, the usability of waste cooking oils (WCO) in diesel engine without converting to biodiesel was investigated. We blended WCO with diesel fuel at 25% (in vol. 25% waste oil + 75% diesel fuel) and 50% (in vol. 50% waste oil + 50% diesel fuel) ratios. In addition, 5%, 10% and 15% toluene were added to the waste cooking oil-diesel fuel blends to improve its fuel properties. A single-cylinder, direct injection, air cooled, diesel engine was used for engine experiments. The experiments were conducted with a constant engine speed (1800 rpm) and different engine powers (2 kW and 4 kW). The results show that toluene addition is effective on density, viscosity and calorific value and in-cylinder pressure values. The toluene addition increased the maximum in-cylinder pressure values. The maximum pressure point approached the top dead center (TDC). Improvement in thermal efficiency and BSFC has occurred with the addition of toluene. With the exception of NOx emissions, other emissions were reduced by the toluene addition.

The similarity ratio effects in design of scaled model experiments for marine diesel engines

Marine diesel engines usually span a large range of bore diameters or power. While optimization of spray combustion system based on scaled model experiments would be beneficial to reduce the cost, energy consumption and project cycle of marine engine development, the similarity ratio effects on the design target parameters such as in-cylinder maximum pressure, indicated thermal efficiency, and NOx and soot emissions are rarely investigated. In this study, firstly, the three-dimensional computational fluid dynamics models are calibrated against the experiment data such as in-cylinder pressure and heat release rate evolutions, indicated thermal efficiency and NOx emissions, and the boundaries of similarity ratio determined by the limits of piston speed, engine speed and fuel injection pressure are clarified. Then, the effects of similarity ratio ranging from 0.8 to around 3 are studied under the different engine loads, engine types and scaling laws. The results show that the prediction accuracy of the scaled model experiments decreases with the increase of the bore diameter difference, and the exponential function can well describe the relationship between the design target parameters and similarity ratio. The results also reveal that the scaling laws should be properly selected for different design target parameters. The scaling law based on constant injection pressure exhibits great potential for predicting indicated thermal efficiency and maximum in-cylinder pressure, as the maximum difference of these parameters between the base engine and targeted engine is less than 1.2% with the similarity ratio up to 3.00.

Dual fuel ethanol port injection in a compression ignition diesel engine: Technical analysis, environmental behavior, and economic viability

The increase in prices, dependence on fossil fuels, and concerns about greenhouse gas emissions, and strict emissions regulations have motivated researchers to look for low carbon renewable fuels for internal combustion engines. Ethanol is one of these fuels due to its presence in the energy matrix of several countries. Among the methods applied to use ethanol in compression ignition engines, the primary technique currently studied is port fuel injection (PFI). This research studies the feasibility of using ethanol as a partial fuel in a generator set analyzed beyond the technical and environmental parameters and the economic aspect. The experiments were conducted in a diesel single-cylinder engine, with its original diesel fuel direct injection system, and added an auxiliary PFI system for the ethanol supply. The research gap is based on the lack of studies that include, in addition to the analysis of performance parameters and gaseous emissions, the economic viability assessment for the studied engine, which is also a fundamental factor in an actual application. The engine was tested under different conditions of six progressive replacements of diesel fuel by ethanol, starting only with diesel fuel (baseline test) and increasing ethanol mass fraction up to 0.634. The measured data showed that ethanol effectively increased ignition delay and reduced combustion duration, which did not lead to increased efficiency and reduced fuel consumption. The maximum in-cylinder pressure was 71.3 bar in the baseline test and dropped progressively to 51.6 bar when in the most significant substitution. The rate of heat release increased by about 92.5% with ethanol concerning the baseline test. When ethanol was used, the CO emissions decreased by up to 43%, resulting in about 2.4 g/kWh, while NOx emissions reduced by up to 20% compared to the baseline test, achieving 0.69 g/kWh. The economic analysis made it clear that the operational cost increased when the engine worked with ethanol replacing partially diesel fuel. However, with a slight increase in operational cost, especially in São Paulo (SP) state, it is possible to reduce pollutant emissions. For the baseline test, the operating cost was 0.354 U$/kWh. The specific fuel cost reaches a maximum of 0.441 U$/kWh, 25% higher than the respective baseline test, increasing ethanol fraction.

Effects of Ignition Timing on Combustion Characteristics of a Gasoline Direct Injection Engine with Added Compressed Natural Gas under Partial Load Conditions

The gasoline/natural gas dual-fuel combustion mode has been found to have unique advantages in combustion. The ignition timing has a significant impact on the combustion characteristics of gasoline engines. Thus, here we study the combustion characteristics of gasoline/natural gas dual-fuel combustion mode to determine the details of their respective advantages under cooperative combustion. A direct-injection turbocharged gasoline engine was modified, and an engine experimental platform was built for the coordinated control of gasoline direct-injection and natural gas port injection. A low-speed and low-load operating point was selected, and the in-cylinder pressure, heat release rate, pressure rise rate, combustion temperature, ignition delay, and combustion duration under the coordinated combustion of gasoline and natural gas dual fuel at the ignition moment were studied through bench tests among other typical combustion parameters. The results show that with the increase of the ignition advance angle, the maximum cylinder pressure, heat release rate, pressure rise rate, and maximum combustion temperature increase. The ignition advance angle is 28°CA-BTDC, and PES40 has the best fuel synergy effect and the best power performance improvement. The effect of the advance of the ignition advance angle on the ignition delay and the combustion duration reaches the peak at 20°CA-BTDC–22°CA-BTDC, and the improvement of the two periods is more significant at PES60.

Effect of H2 addition to methanol-gasoline blend on an SI engine at various lambda values and engine loads: A case of performance, combustion, and emission characteristics

The main purpose of this study was to investigate the effects of hydrogen and methanol addition on the engine performance, combustion, and emission characteristics of a spark-ignition engine. The experiments were performed with pure gasoline, methanol-gasoline, and hydrogen-methanol-gasoline fuel blend under various engine loads (25Nm, 50Nm, 75Nm, and 100Nm, 100%), different lambda values (0.8, 1, and 1.2), and a constant engine speed (2000 rpm). The hydrogen energy substitute rate method was applied for hydrogen enrichment that was constituted by 5% of the total input fuel energy. The experimental results indicated that the average values of brake specific fuel consumption were increased by 11.98% with the methanol-gasoline test fuel, while decreased 4.07% with the hydrogen-methanol-gasoline fuel blend. The average values of brake thermal efficiency were slightly increased by 0.07% and 0.61% with the methanol-gasoline and hydrogen-methanol-gasoline fuel blends, respectively. The combustion characteristics were improved after adding the methanol and hydrogen. In this respect, the average ignition delay values decreased by 6.45% with the addition of the methanol in gasoline, while the combustion duration, maximum cylinder pressure, and maximum heat release rate values increased by 0.85%, 1.66%, and 2.32%, respectively. Furthermore, the ignition delay and combustion duration values were substantially affected by the addition of the hydrogen and observed to be at rates of 21.10% and 6.93% reduction, respectively. In addition, the maximum cylinder pressure and maximum heat release rate values were increased by 2.02% and 4.13%. The combustion characteristics improved after the addition of hydrogen and methanol, which also considerably affected the engine performance and emission characteristics. The average values of exhaust gas temperature, hydrocarbon, carbon dioxide were increased by 0.92%, 2.26%, and 0.156% with methanol and the values of carbon monoxide and nitrogen monoxide were decreased by 1.09% and 11.82%, respectively. However, the hydrocarbon, carbon dioxide values were decreased by 13.06%, 3.90% with the hydrogen, while the carbon monoxide, exhaust gas temperature, and nitrogen monoxide were increased by 1.84%, 1.38%, and 31.68%, respectively. Although nitrogen monoxide was considerably decreased by the methanol, a drastic increase was observed with the hydrogen. The optimum brake specific fuel consumption and nitrogen monoxide values occurred between 68.61 Nm and 74.55 Nm of the engine loads for the methanol-gasoline and hydrogen-methanol-gasoline test fuels at λ = 1 and 1.2. Overall, the engine performance, combustion, and emission characteristics were improved by the addition of hydrogen and methanol in the test fuels due to their superior fuel properties compared to gasoline.

Study of methane enrichment in a biogas fuelled HCCI engine

Biogas has been a promising alternative fuel for IC engines. However, its CO2 content reduces calorific value and ignitability. The CO2 fraction of raw biogas can be separated out by various techniques, which are collectively called methane enrichment. The present study explores the effect of methane enrichment on the output parameters of a Homogeneous Charge Compression Ignition (HCCI) engine. A single cylinder CI engine is altered for this purpose. Biogas (CH4 + CO2) is supplied along with air. Diethyl Ether (DEE) is used as the secondary fuel to initiate auto-ignition. The effects of injecting DEE at the inlet port and upstream in the intake manifold are also compared. Performance, emission and combustion characteristics such as brake thermal efficiency, equivalence ratio, HC, CO, CO2, NOx and smoke emissions, start and duration of combustion, in-cylinder pressure and maximum heat release rate are compared for operation with raw biogas (50% methane) and methane enriched biogas (100% methane) for various biogas flow rates and engine torques. Results show that methane enrichment enhances brake thermal efficiency by up to 2% compared to raw biogas. Methane enrichment advances and speeds up combustion. HC, CO and CO2 emissions, maximum cylinder pressure and maximum heat release rate are also improved with methane enrichment. Ultra-low NOx and smoke emissions can be obtained using raw biogas as well as methane enriched biogas. Low biogas flow rates provide better brake thermal efficiency and HC emissions. Manifold injection of DEE enhances brake thermal efficiency by up to 2% compared to port injection by virtue of greater mixture homogeneity.

Effect of nitrogen and hydrogen addition on performance and emissions in reactivity controlled compression ignition

Compression ignition engines have always been attractive due to high thermal efficiency. Advanced combustion modes have been developed for internal combustion engines to reduce both harmful emissions and fuel consumption. One of these technologies is the reactivity controlled compression ignition (RCCI) mode. Mixture formation in the RCCI engine is provided by a low reactivity fuel injection (port fuel injection) during the intake stroke and stratified high reactivity fuel injection into the cylinder (direct injection) during the compression stroke. In the present study, the effect of reforming gases on RCCI combustion was investigated numerically. The RCCI experimental data were obtained from a previous study performed on a 1.9-liter GM brand gasoline engine fueled with gasoline/diesel fuels. The simulation was performed via Converge Computational Fluid Dynamics (CFD) code, and numerical results were validated with the experimental data. The maximum in-cylinder pressure was recorded as 6.84 MPa with nitrogen addition. It is reached up to 15.12 MPa in case of using hydrogen and nitrogen together. Soot production reached a maximum level of 8.5×10-3g/kg-fuel with 72% nitrogen addition. However, soot pollutants were reduced via 4% hydrogen substitution and recorded as 2.3×10-5g/kg-fuel. While the in-cylinder gas temperature was 1295 K with 72% nitrogen, it reached 3578.5 K with hydrogen addition.