Gas Fuelled Spark Ignition Engine Research Articles

Experimental Examination of Recovery by a Thermoelectric Generator of Heat Energy Lost to Engine Coolant in a SI Engine

In this study, the recovery of heat energy lost to the engine coolant (Ec) in a liquid-cooled, gas-fueled (propane), spark ignition (SI) engine using a thermoelectric generator (TEG) is experimentally researched. A two-layer rectangular geometry TEG is designed, consisting of a propane heat exchanger (P_hex) located on the surface of an engine coolant heat exchanger (Ec_hex). 20 items of thermoelectric modules (TEMs), each 30x30 mm in dimensions, are placed between the Ec_hex and P_hex. In the TEG design, engine cooling fluid is used on the hot surface of the TEMs, and propane gas fed to the engine is used on the cold surface. In addition, with the use of the designed TEG, there is no need to use an additional evaporator for propane gas. Experiments are carried out with the designed TEG at 8 engine speeds ranging from 1500 to 5000 rpm. As a result, TEG produces 1.25–3.01 W of DC electrical power in the engine's 1500–5000 rpm range, while TEG efficiency fluctuates between 2.7 and 3.1%. However, the maximum TEG_power is 3.01 W at 5000 rpm, while the maximum TEG_efficiency is 3.1% at 1500 rpm. On the other hand, the electrical power of TEG between 1500 – 5000 rpm of the engine is approximately 1.1–1.26% of the engine charging system power. However, TEG's contribution to the charging system again decreases with the engine speed.

Computational analysis of performances for a hydrogen enriched compressed natural gas engine’ by advanced machine learning algorithms

The support vector machine along with particle swarm optimization and artificial neural network have already been implemented for the regression study of a hydrogen enriched compressed natural gas (HCNG) fueled spark ignition engine. The main issues were that the support vector machine along with particle swarm optimization requires more computational time while the artificial neural network is sensitive to the hidden layers. Therefore, these algorithms are not effectively suitable for online control of the electronic control unit. The theme of this study is to evaluate the multiple mathematical engine’ models with respect to swiftness and accuracy. The experiments have been conducted under a wide range of operating conditions in a heavy-duty SI engine to obtain the data sets. The brake specific fuel consumption, engine torque and NOx emissions have been trained and analyzed by eight different machine learning algorithms along with nineteen sub-models. The effectiveness of these algorithms has been evaluated with respect to the root mean squared error and prediction time. The analysis indicate that the gaussian process regression (GPR) is optimal with respect to the computational efficiency (i.e., RMSE = 0.3823 g/kWh) and time (t < 16.019 sec). Furthermore, it operates without the iteration of the hidden layers. The mean simulation time for the gaussian process regression is 20,192 times lower as compared to the support vector machine along with particle swarm optimization algorithm. Since the gaussian process regression (GPR) is fast, optimal and insensitive to the hidden layers, so it is an ideal tool for online calibration of the electronic control unit.

Experimental investigation of a novel thermoelectric generator design for exhaust waste heat recovery in a gas-fueled SI engine

In this paper, a series of tests are performed on the exhaust waste heat recovery using a thermoelectric generator (TEG) in a propane-fueled spark-ignition (SI) engine. A three-layer TEG is designed, consisting of two engine coolant exchangers (Ec_hex) positioned on both surfaces of the rectangle exhaust heat exchanger (Ex_hex). Unlike the literature papers, a novel design is created by placing copper serpentine pipes in each Ec_hex to allow propane to pass through the TEG. The reason for this is both to ensure the evaporation of propane and to increase the ΔT temperature differences by increasing the cold surface activity of TEG. A total of 12 pieces of thermoelectric modules (TEMs), 56x56 mm in size, are positioned between the rectangular Ex_hex and each Ec_hex, and a total of 24 pieces of TEMs are used in TEG. Experimental studies were performed for eight different engine speeds in the range of 1500–5000 rpm for TEGs with and without a propane inlet. In addition, computational fluid dynamic (CFD) analyses are performed to visualize both the cold and hot surface temperature contours of the TEMs. The results of the paper illustrate that the DC electrical power of the TEG with propane is higher in the range of 11.5–12.1% compared to the TEG without propane in the 1500–5000 rpm range of the engine. At 4500 rpm engine speed, the propane input TEG produced a maximum of 90.2 W of DC electrical power and a 3.02% energy conversion efficiency. In addition, there is a good correlation between the experimental and numerical findings, varying between 3% and 15% with the engine speed.

Parametric Optimization of Producer Gas fuelled Spark Ignition Engine through Thermodynamic Modelling

Development of alternative fuel has become a necessity to quench the current/rising future energy demands and alarming environmental pollution. Producer gas/syngas has potential to be most favorite alternative fuel substitution whose performance characteristics are lower whereas emission characteristics of carbon monoxide (CO), carbon dioxide (CO 2 ) and hydrocarbons are better than petrol/diesel. Looking at these facts, the present work focuses on thermodynamic modelling and parametric studies on a real-life engine using producer gas as fuel to study its performance and emission characteristics. Simulated program is validated with published literature and results are found within ± 9% in terms of power and efficiency. The model is then used to study the effect of Spark advance (10°–30°), valve timing and combustion duration (40°–80°), fuel-air ratio, stroke to bore ratio and connecting rod length to crank radius to study their impact on emission and performance of real-life engine. The optimum engine performance parameters while also considering emission of nitric oxide (NO) and CO operated at stoichiometric fuel-air ratio turns out to be L/D as 1.0, Spark advance as 20° BTDC (before top dead center), combustion duration as 50°, inlet valve closing as 30° ATDC and exhaust valve opening as 10° BBDC (before bottom dead center). The efficiency, specific fuel consumption, power, CO and NO with these optimal parameters are of the order of 19.58%, 1.23 kg/kWh, 67.0 kW, 0.65 ppm and 0.017 ppb, respectively. It is believed that present work offers optimal design and operating parameters through actual thermodynamic cycle analysis which may be used as a reference for design and development of producer gas-fuelled Spark Ignition (SI) engines.

Improvement of performance and emission in a lean‐burn gas fueled spark ignition engine by using a new pre‐chamber

AbstractLean burn combustion of natural gas in spark‐ignited engines is a promising approach to improving engine performance and efficiency by reducing pollutant emissions and better fuel consumption. However, inducing excessive lean mixture to the engine makes the combustion unstable, and misfire happens in a significant number of cycles. The pre‐chamber ignition technology is a useful solution that can make spark‐ignition engines more efficient. In this study, the lean mixture's combustion was empirically investigated with a new pre‐chamber spark plug in a one‐cylinder engine fueled with natural gas. Tests were performed at 11.5, 13.5, and 16 compression ratios and a wide range of air‐fuel ratios. With the pre‐chamber spark plug usage, the lean operating limit is enlarged by 10%–45% and gives 4% and 3% the average lower in‐cylinder pressure and exhaust gas temperature than the conventional spark ignition system. The brake‐specific fuel consumption was improved by 4%–11% using the pre‐chamber spark ignition. The HC, CO, and NOx formation is about 11%, 16.3%, and 10% lower than the conventional spark ignition usage. Outcomes confirmed that the new design pre‐chamber plug gives 1% improved COVIMEP than the standard spark plug. The use of pre‐chamber due to the lean‐burn combustion causes larger ignition delay and increases brake thermal efficiency by up to 9%. It can be concluded that the pre‐chamber increases the ignition ability, and the lean mixture limit is extended.

Knocking behavior and emission characteristics of a port fuel injected hydrogen enriched compressed natural gas fueled spark ignition engine

Natural gas has highest hydrogen-to-carbon ratio among hydrocarbon fuels, which helps in reducing greenhouse gas emissions. Blending natural gas with hydrogen decreases emissions even further because of superior combustion characteristics of hydrogen enriched compressed natural gas (HCNG) mixtures. This study focuses on measurement of carbon dioxide, nitrogen oxides, hydrocarbons, carbon monoxide and particulate emissions from HCNG mixtures and compare them with that of baseline compressed natural gas. Hydrogen enriched fuels are prone to higher knocking therefore, experiments were conducted on a single cylinder port fuel injected spark ignition engine prototype using variety of test fuels such as compressed natural gas, 10, 20, 30, 50, 70% HCNG mixtures and hydrogen for in-depth understanding of relative particulates and gaseous emissions, in addition to determining the engine’s knocking characteristics. Experimental results showed that hydrogen enrichment of natural gas reduced emissions of carbon dioxide, hydrocarbons, and carbon monoxide however emissions of nitrogen oxides increased. Lowest knock intensity was observed for 30HCNG mixture. HCNG mixtures improved the engine out emissions and reduced the knocking tendency experienced with hydrogen fueling in internal combustion (IC) engines. Hydrogen enrichment of natural gas also reduced the carbon intensity of fuels, which in-turn reduced greenhouse gas emissions.

Influence of exhaust residuals on combustion phases, exhaust toxic emission and fuel consumption from a natural gas fueled spark-ignition engine

Exhaust gases remaining inside the engine cylinder after the exhaust stroke premix with fresh air-fuel combustible mixture and affect combustion process in the engine cylinder. Due to significantly higher temperature of these exhaust residuals (ExR) compared to the external exhaust gases recirculation (EGR), their impact on the in-cylinder combustion process is also different from impact of EGR. To control amounts of ExR independent of engine working parameters, the variable valve timing was introduced. It is known that variable valve timing affects not only volumetric efficiency and performance of the internal combustion reciprocating engine but also influences the amount of exhaust residuals remaining in the engine cylinder. These exhaust residuals impact combustion rates, combustion stability, knock and also play crucial role on exhaust toxic emissions. In this manuscript, the effect of variable valve overlap was studied on A. exhaust toxic emission (NOx, CO and THC), and B. combustion phasing and engine performance on a spark ignited natural gas fueled engine.The investigation was carried out in a single cylinder research engine at constant load. The engine was equipped with high authority dual independent cam phasors for both intake and exhaust values, but for the purpose of this study, the exhaust valve timing was fixed and intake valve timing was changed to vary the amount of exhaust residuals remaining in the engine cylinder. The correlation between valve overlap and exhaust residuals were determined. It was observed that correlation in the positive overlap range between 55 and 85 deg was almost positive linear. Regarding toxic exhaust emission, increase in exhaust residuals from 9.6 to 12.3% (change by 28%) caused reduction in NOx by 67% and increase in both CO and THC by approximately 75%. Additionally, it did not significantly affect the engine’s specific fuel consumption. Summarizing, strong correlation between in-cylinder exhaust residuals and toxic emissions, and combustion phases exists in the methane fueled spark ignited engine equipped with VVT.

Influence of high compression ratio and excess air ratio on performance and emissions of natural gas fuelled spark ignition engine

Compressed natural gas is in automotive industry recognized as one of the ?cleanest? fossil fuels which can be used in internal combustion engines with a number of benefits. Since natural gas has much higher octane rating than gasoline it is expected that higher compression ratios can be used. The goal of the research is to determine the change of performance of spark ignited engine with the increase of compression ratio to values similar to compression ignited engine while keeping the exhaust emissions on the acceptable level and avoiding knock combustion. Measurements are performed at compression ratios 12, 16, and 18 at three different values of air excess ratio. Methane with known composition from a pressure cylinder is used instead of natural gas and the results are comprised of indicating results (in-cylinder and intake pressure in a crank angle space), emissions, temperatures, and mass-flows on various intake and exhaust positions. Analysis of results shows high influence of compression ratio and excess air ratio on combustion, performance, and exhaust gas emissions.

Effects of compression ratio and hydrogen addition on lean combustion characteristics and emission formation in a Compressed Natural Gas fuelled spark ignition engine

A single cylinder diesel engine was modified to operate as a Compressed Natural Gas (CNG) fuelled lean burn Spark Ignition (SI) engine. The engine was tested at 1500rpm under wide open throttle condition at different compression ratios over varying equivalence ratios. The optimized compression ratio for CNG operation was found to be 12.5:1 which was further investigated for hydrogen substitution at 5% and 10% on energy basis to study and compare the performance, emission and combustion behavior of CNG fuelled lean burn SI engine. The brake thermal efficiency and brake power output increases with rise in compression ratio and achieved a peak brake thermal efficiency of 30.2% with 12.5:1 compression ratio and above a critical value of 12.5:1, the improvement was small when compared to the increase in emissions. Wide flammability limits of hydrogen enable ultra-lean combustion thereby extends the lean limit of operation to an equivalence ratio of 0.42 with 10% hydrogen addition as compared to 0.50 with neat CNG operation and its anti-knock enhancement makes it advantageous compared to increasing the compression ratio under low load conditions. Hydrogen addition also enhanced the combustion rate, heat release rate and reduced cyclic variations. On the emissions front, hydrogen addition showed reduction in hydrocarbon emissions from 65g/kWh to 6.9g/kWh at an equivalence ratio of 0.5 alongside carbon monoxide and carbon dioxide reduction. Due to retarded ignition timing to avoid knock, the Oxides of Nitrogen (NOx) emission increase was not significant.

A detailed kinetic investigation on the effects of hydrogen enrichment on the performance of gas-fueled SI engine

ABSTRACTThis study investigates the effects of hydrogen enrichment on formation of pollutants and greenhouse gases in gas-fueled spark ignition engines. To this end, a previously validated detailed mechanism is embedded with a comprehensive one-dimensional engine model and the results are verified with experimental observations at different compression ratios and engine loads. The simulations are then performed for different mixtures of hydrogen and natural gas. The results indicate that adding hydrogen increases the cylinder peak pressure at different loads and compression ratios, despite the fact that reduces the amount of carbon monoxide, carbon dioxide, and methane in all the conditions.

A computational study of operating range extension in a natural gas SI engine with the use of hydrogen

The performance of a natural gas fueled spark ignition engine was studied to investigate the effect of hydrogen enrichment on the engine operating range and combustion characteristics. A validated multi-dimensional CFD model coupled with detailed chemical kinetics mechanism was used to study the combustion process in Hydrogen/CNG engine. Results indicated that misfiring occurs in equivalence ratios of about 0.61, 0.48 and 0.42 for hydrogen fractions of 0%, 30% and 50% respectively. Also, combustion durations were 70, 47 and 45° crank angle for hydrogen fractions of 0%, 30% and 50% respectively with same equivalence ratio (Ф = 0.625). Regarding the emission, the maximum amount of break specific NOx was detected around Ф = 0.83 (λ = 1.2), and this point is almost independent of the hydrogen fraction. It was found that hydrogen fraction decreases the emissions of CO, and HC and CO2. Adding 30% hydrogen reduced CO2 emission by10.2% while 50% hydrogen fraction led to 22.7% CO2 reduction.

Experimental investigation of an improved exhaust recovery system for liquid petroleum gas fueled spark ignition engine

In this study, we have investigated the recovery of energy lost as waste heat from exhaust gas and engine coolant, using an improved thermoelectric generator (TEG) in a LPG fueled SI engine. For this purpose, we have designed and manufactured a 5-layer heat exchanger from aluminum sheet. Electrical energy generated by the TEG was then used to produce hydrogen in a PEM water electrolyzer. The experiment was conducted at a stoichiometric mixture ratio, 1/2 throttle position and six different engine speeds at 1800-4000 rpm. The results of this study show that the configuration of 5-layer counterflow produce a higher TEG output power than 5-layer parallel flow and 3-layer counterflow. The TEG produced a maximum power of 63.18 W when used in a 5-layer counter flow configuration. This resulted in an improved engine performance, reduced exhaust emission as well as an increased engine speed when LPG fueled SI engine is enriched with hydrogen produced by the PEM electrolyser supported by TEG. Also, the need to use an extra evaporator for the LPG fueled SI engine is eliminated as LPG heat exchangers are added to the fuel line. It can be concluded that an improved exhaust recovery system for automobiles can be developed by incorporating a PEM electrolyser, however at the expense of increasing costs.

Evaluating carbon emissions reduction by use of natural gas as engine fuel

The exhaust emissions of carbon monoxide (CO) and carbon dioxide (CO 2) from a natural gas fuelled spark ignition engine have been evaluated. A production, four-cylinder, eight-valve, 1.4-l, flexible fuel engine equipped with a commercial natural gas kit was tested in a bench dynamometer. The tests were carried out simulating the standard emission test cycle U.S. FTP-75. The results demonstrate that natural gas substantially reduces exhaust CO emissions in comparison with gasoline, falling below current regulated limit even without use of catalytic converter. Use of natural gas also reduced CO 2 emissions to a level below the average of European fleet.

Combustion and emission characteristics of a lean burn natural gas engine

Lean burn is an effective way to improve spark ignition engine fuel economy. In this paper, the combustion and emission characteristics of a lean burn natural gas fuelled spark ignition engine were investigated at various throttle positions, fuel injection timings, spark timings and air fuel ratios. The results show that ignition timings, the combustion duration, the coefficient of variation (COV) of the indicated mean effective pressure (IMEP) and engine-out emissions are dependent on the overall air fuel ratio, spark timings, throttle positions and fuel injection timings. With the increase of the air fuel ratio, the ignition delays and combustion duration increases. Fuel injection timings affect ignition timings, combustion duration, IMEP, and the COV of the IMEP. Late fuel injection timings can decrease the COV of the IMEP. Moreover, the change in the fuel injection timings reduces the engine-out CO, total hydrocarbon (THC) emissions. Lean burn can significantly reduce NOx emissions, but it results in high cyclic variations.

Fuzzy neural ignition timing control for a natural gas fuelled spark ignition engine

One of the important inputs to a spark ignition engine which affects nearly all engine outputs is ignition timing. It is well known that the optimum ignition timing which gives the maximum brake torque for a given engine design varies with the rate of flame development and propagation in the cylinder. Modern engines show ignition timing being generally controlled by fixed open-loop schedules as functions of engine speed and load. It is desirable that this ignition timing can be adjusted to the optimum level which produces the best torque to obtain minimum fuel consumption and maximum available power. This paper presents an ignition timing control system based on fuzzy logic and neural network theories. A fibre optical sensor system was developed for measurement of the intensity of the luminous emission which correlates the combustion pressure and ignition timing control on a Ford 1600 cm3 four-cylinder spark ignition engine fuelled with natural gas. Several engine tests were carried out in optimizing the combustion intensity detection system. The results obtained provide important information compatible with intelligent control of the engine using fuzzy neural control technology. Moreover, tests carried out with data using this technology show good results that fit quite well with the original engine output torque characteristics.

An experimental and analytical examination of the combustion period for gas-fuelled spark ignition engine applications

A predictive procedure is described for determining the effective time period needed to complete the energy release by combustion from the moment of flame initiation by a spark to the completion of flame propagation in a spark ignition engine while using a number of gaseous fuels and some of their mixtures. These predicted values of the combustion period when used in a relatively simple modelling procedure can produce predicted values of key engine performance parameters that compare well with the corresponding experimentally obtained values.

Speciated hydrocarbon emissions from a gas-fuelled spark-ignition engine with various operating parameters

For natural gas and liquefied petroleum gas (LPG), measurements of the concentrations of individual exhaust hydrocarbon (HC) species have been made under various engine operating conditions in a 2 litre four-cylinder engine using gas chromatography. Non-methane hydrocarbon (NMHC) in addition to the species of HC and other emissions such as CO2, CO and NOx were examined for natural gas and LPG at 1800 r/min for two compression ratios (8.6 and 10.6), various brake mean effective pressure (b.m.e.p.) values (250-800 kPa), spark timings (before top dead centre 10°-55°) and exhaust gas recirculation ratios up to 7 per cent. Fuel conversion efficiencies were also investigated together with emissions to study the effect of engine parameters on the combustion performance in gas engines, especially under the lean burn conditions. It was found that CO2 emission decreased with smaller C value of fuel, leaner mixture strength, higher compression ratio, higher b.m.e.p. and the ignition near the maximum brake torque spark timing. HC emissions from the LPG engine consisted primarily of propane (C3 H8) (more than 60 per cent), ethylene and propylene (C3 H6), while the main emissions from natural gas were methane (more than 60 per cent), ethane, ethylene and propane. Natural gas was shown to have less of a tendency to form ozone than LPG. This was accomplished by reducing the emissions of propylene, which has a relatively high maximum incremental reactivity factor, and propane, which forms a large portion of LPG. In addition, natural gas shows a benefit in the other emissions (i.e. NMHC, NOx and CO2), specific reactivity and brake specific reactivity values except fuel conversion efficiency.

713 天然ガスエンジン燃焼室内燃料濃度分布に及ぼすスロットル開度の影響(OS-6 反応流動の解析および運転制御)

713 天然ガスエンジン燃焼室内燃料濃度分布に及ぼすスロットル開度の影響(OS-6 反応流動の解析および運転制御)

混合気流動を利用した火花点火式天然ガス希薄燃焼機関の燃焼改善に関する基礎的研究

For the final goal of developing the natural gas-fueled spark-ignition engines with high thermal efficiency and low pollutant emission, the effects of the fluid flow inside a combustion chamber on the combustion process of a homogeneous lean methane/air mixture were examined using a rapid compression combustor. The rapid compression combustor was designed to simulate the combustion process in a spark-ignition engine involving the rapid compression of a mixture and the heat release during the flame propagation. The main advantage of using this combustor is that experiments can be made under the idealized and well-controlled conditions. The time history of pressure in the combustion chamber was measured with a pressure transducer. The fluid flow in the combustion chamber was varied as follows; the mixture was injected into the combustion cylinder before the compression stroke, and the direction of the injection and the time interval between the end of mixture charge and the start of compression stroke were varied. The position of spark ignition was also varied. And the flame propagation was photographically observed. Moreover, the two-dimensional velocity distribution of the swirl flow was measured with particle image velocimetry. As expected, the combustion duration decreased with increases in the mean velocity and the turbulence intensity of the fluid flow. When the intense swirl flow existed in the combustion chamber, the combustion duration was minimized with spark ignition at the eccentric location.

Hydrogen as an additive to methane for spark ignition engine applications

The performance of a gas fuelled spark ignition engine is enhanced when relatively small amounts of hydrogen are present with methane. This improvement in performance, which is especially pronounced at operational equivalence ratios that are much leaner than the stoichiometric value, can be attributed largely to the faster and cleaner burning characteristics of hydrogen in comparison to methane. Through analytical simulation of engine performance, the addition of hydrogen is considered through its production in situ on board the engine by electrolysis of water with the necessary energy supplied from engine power. It is shown that when the work energy required for the production of hydrogen by electrolysis is taken into account, the range of viable operation of such an engine is very narrow. This would render the whole concept of in situ hydrogen production through water electrolysis uneconomical in conjunction with engine operation, even though the presence of additional oxygen produced with the hydrogen tends, in principle, to improve engine performance beyond that observed with hydrogen addition. © 1999 International Association for Hydrogen Energy.