Query: engine equivalence ratio

title: Laser Induced Breakdown Spectroscopy for On Line Engine Equivalence Ratio Measurements
abstract: Laser induced breakdown spectroscopy (LIBS) has been used to measure the equivalence ratio of a spark ignited engine in a laboratory setting. Spectral features of C (711.3 nm) O (776.6 nm) N (746.3 and 743.8 nm) and CN (broad emission 707 734 nm) were used to quantify the equivalence ratio over a range from Ph 0.8 to Ph 1.2. The C/N and C/O peak ratios were found to be successful measurement metrics, compared with a standard exhaust gas oxygen analyzer, for averaged measurements. Some variation in the measurements was observed as a function of engine load. Single shot data based on a CN/air peak ratio were evaluated using a separate calibration from averaged measurements, and the average of the single shot data was found to agree well with the exhaust gas oxygen analyzer. The scatter in the single shot data was substantially higher at lower equivalence ratios. The measurements including the CN peak were slightly sensitive to load, possibly due to pressure changes in the sample as the load increases, or possibly due to changes in the particle size distribution in the gas stream.

title: Experimental investigation of equivalence ratio effects on combustion and emissions characteristics of an H2/methanol dual injection engine under different spark timings
abstract: The addition of H2 is an effective way to enhance the speed of propagation of a flame and extend the lean burn limit of spark ignition (SI) engines. An H2 port injection and methanol direct injection dual fuel SI engines were used in this study to investigate the effect of the equivalence ratio on the combustion and emissions characteristics of the engine at low speed using the late injection strategy for methanol. The results show that 3% 6% of H2 enriched methanol can effectively expand the lean burn limit from an equivalence ratio of 0.625 of pure methanol to that of 0.455. The spark timing of H2 addition must be optimized by different equivalence ratios and ratios of H2 addition to implement ideal combustion phasing at 16degCA ATDC and 10degCA ATDC of pmax and HRRmax, respectively. H2 addition can significantly shorten both CA0 10 and CA10 90, and can quickly advance CA50. For 6% of H2 added, when the equivalence ratio was over 0.5, the COVimep was below 3.5% This addition significantly improved the lean burn characteristics of the H2/methanol SI engine. BSHC emissions with the addition of 6% H2 was much lower than that of the pure methanol engine at equivalence ratios of over 0.625. When H2 was added, BSCO emissions increased rapidly in terms of both lean and stoichiometric equivalence ratios, compared with the case when no H2 was added.

title: Effect of biosolar fuels and S. Marginatum algae biofuel on equivalence ratio in diesel engine with EGR
abstract: One type of motor vehicle engine that is very suitable for transportation and heavy equipment vehicles is a diesel engine, because high combustion efficiency, reliability, fuel flexibility, and low fuel consumption make diesel widely used in several countries. A mixture of S. Marginatum algae biodiesel and bio solar fuel is used as an alternative fuel. This test is carried out by using variations in the percentage of the load, with variations of pure diesel fuel (D100) and a mixture of bio solar fuels, and algae biodiesel at t 1500 rpm. In this context, the purpose of this study was to obtain its performance curves from a diesel engine of the brand, using as fuel mixtures diesel oil, bio solar fuel, and S. Marginatum algae biodiesel, in the proportions B20, B20 10% B20 15% and B20 20% the power take off dynamometer test. The results showed that engine performance of equivalence ratio an increase with other models of the same used in the region, showing the best engine output in the region bio solar fuel mixtures with the Hot EGR (Exhaust Gas Recirculation) system.

title: Effect of equivalence ratio on combustion and emissions of a dual fuel natural gas engine ignited with diesel
abstract: China is the world largest natural gas engine market, and the natural gas price has a large fluctuation range, Natural gas diesel dual fuel engine may be one of the options to cope with gas price fluctuations. Effect of equivalence ratio on combustion and emissions with a low compression ratio of 14.2 in a dual fuel 6 cylinder engine was experimentally studied. Comparison between dual fuel and spark ignition engine at stoichiometric combustion and same IMEP was conducted. Results show that the gas consumption rate decreases with the increase of equivalence ratio regardless of the strategy in nozzle parameter, exhaust gas recirculation (EGR) rate, injection parameter. Peak heat release rate and exhaust gas temperature increased, and decrease of combustion duration is obtained due to the high equivalence ratio in dual fuel ignition mode. The gas consumption rate trend of spark ignition mode is similar to that of dual fuel engine with the increase of equivalence ratio. Dual fuel engine with low compression ratio of 14.2 run as spark ignition (SI) gas engine at stoichiometric ratio, but the difference lies in the combustion process. The peak heat release rate of dual fuel engine presents higher value, while the combsution duration of dual fuel engine is shorter, and the gas consumption rate of dual fuel engine is lower than that of SI engine.

title: Experiments on the effect of engine speed, load, equivalence ratio, spark timing and coolant temperature on the energy balance of a turbocharged hydrogen engine
abstract: Internal combustion engines are used to translate the chemical energy of fuel to the brake power and over two third of energy is wasted in the form of exergy and anergy in this process. An experimental energy balance analysis can make the engine energy flow clear and help to recycle the exergy of exhaust gas to increase brake thermal efficiency. In this paper, the effect of five different parameters on the energy distribution was investigated using heat balance test data from a 2.3 L turbocharged hydrogen engine. The results show that when proportion of exhaust gas energy ranges from 24.1% to 36.4% with various engine speeds, brake thermal efficiency can increase 3.69% at 2000 rpm and 7.67% at 4000 rpm with various load, which means that high engine speed and load are beneficial to increase exergy of total system. Both Engine speed and brake thermal efficiency increase with equivalence ratio ranging from 0.4 to 0.9, while proportion of energy of cooling system decreases, which means that both power and economic ascend with increasing equivalence ratio and anergy of total system decreases at low engine speed and load. Furthermore, proportion of exhaust gas energy can increase by 3% at 75% load and 2.5% at 50% load with spark timing closing to TDC and NOx emission is decreasing. Finally, the variation of the coolant temperature has an almost negligible effect in terms of brake thermal efficiency but it can decrease anergy of total system.

title: Role of global fuel air equivalence ratio and preheating on the behaviour of a biogas driven dual fuel diesel engine
abstract: The practice of the green renewable fuels in diesel engines is increasing concerning the progressive deterioration of the green environment and the scarcity of the fossil fuels. In these aspects, several experiments in dual fuel mode (DFM) at different global fuel air equivalence ratio (Phglobal) intake charge preheating and loads have been carried out considering biogas as the inducted renewable fuel. The Phglobal was varied from 0.30 to 0.89 from part to higher loads with biogas flow rate (BFR) of 0.67 3.99 kg/h. The maximum diesel replacements (DR) and biogas energy share (BES) are found to be 92.49% and 97.55% respectively. However, at higher Phglobal, the brake thermal efficiency (BTE) reduces drastically. Although with preheating, there is an increment of BTE by 5.72% and 2.60% at loads of 4.36 N*m and 21.78 N*m, respectively. At lower Phglobal in DFM and with preheating, the diesel like trends of BTE is achieved. Overall combustion behaviour deteriorates at higher Phglobal. However, it significantly improved with the preheating and at controlled Phglobal. Higher cycle to cycle variation of cylinder peak pressure (CPP) is noticed at higher Phglobal. With preheating, at part and higher loads the reduction of CO of 29.41% and 65.49% are estimated. At higher load (21.78 N*m) and with preheating a reduction of 53.33% of HC is noticed. The drastic reduction of NOx is observed with the increment of Phglobal. The superior performance is achieved at each of the tested loads at the optimum Phglobal and with preheating.

title: Experimental investigation of the equivalence ratio influence on combustion, performance and exhaust emissions of a dual fuel diesel engine operating on synthetic biogas fuel
abstract: In this work, an experimental investigation was conducted to analyze dual fuel (DF) engine operation using synthetic biogas fuel under high load at constant percentage energy substitution rate (PES) The performance, ignition delay, and other combustion characteristics of engines operating in dual fuel mode (biogas/diesel) are compared to the conventional mode. The synthetic biogas, composed of 60% methane and 40% carbon dioxide, is the primary fuel which is blended with the air in the engine inlet manifold, whereas the pilot fuel is diesel. The equivalence ratio (fuel air) (ph) was varied by changing air flow rate while the energy introduced into the engine remained constant for all the examined cases. Combustion analysis showed that with increasing ph, the ignition delay tends to become longer and the peak of heat release rate was increased. Furthermore, as ph increased from 0.35 to 0.7, HC and CO emissions were reduced by 77% and 58% respectively. The NOx emissions decreased at 60% PES by 24% while the BTE was improved by 13%

title: Effects of equivalence ratio variations on turbulent flame speed in lean methane/air mixtures under lean burn natural gas engine operating conditions
abstract: Direct numerical simulations (DNS) of turbulent premixed methane/air flames are carried out to investigate the effects of equivalence ratio on the turbulent flame speed in lean mixtures. Turbulent flames are simulated as statistically stationary following a Lagrangian framework using an inflow outflow configuration. The inflow velocity is dynamically adjusted at run time to stabilize the flame brush location within the computational domain. Linear forcing is applied inside the unburned mixtures to maintain the turbulent intensities at desired levels. For the same turbulence properties, several equivalence ratios near the lean limit are selected and it is shown that the normalized turbulent flame speed is a function of the equivalence ratio. Velocity and length scales of the imposed turbulence are then selected in such a way that the Karlovitz and Damkohler numbers remain constant for flames of different equivalence ratios. Simulations are run for more than 80 eddy turnover times and the turbulent flame speed is derived by averaging the inflow velocity. The results show that equivalence ratio does not have an explicit effect on the normalized turbulent flame speed above the lean limit. Analysis of flame surface area shows that surface wrinkling generated by eddies of different scales is not affected by variation in equivalence ratios when the Karlovitz and Damkohler numbers are fixed. Furthermore, flame surface generated by large scale eddies is independent of the Karlovitz and Damkohler numbers. Examining the flame surface statistics, it is shown that the flame surface normal is preferentially parallel to the most compressive strain rate direction for all equivalence ratios.

title: Experimental and theoretical analysis of effects of equivalence ratio on mixture properties, combustion, thermal efficiency and exhaust emissions of a pilot ignited NG engine at low loads
abstract: This paper presents the effects of equivalence ratio Ph on mixture properties, combustion, thermal efficiency and exhaust emissions of a pilot ignited natural gas (NG) engine using diesel as an ignition source at low loads. Ph was changed in a wide range (0.4 0.9) by changing throttle opening with other combustion boundaries being unchanged with different NG percentage energy substitutions (PES) at 1335 rpm and 25% load. The experiments were arranged based on an electronically controlled heavy duty, turbocharged, intercooler, 6 cylinder and four stroke pilot ignited NG engine. Thermodynamic properties of the NG air mixture with decreasing air were analyzed theoretically using thermodynamic relations and ideal gas equations. In addition, the time sequenced characteristic and the heat release rate (HRR) imbalanced characteristic were found in the engine combustion process, with their quantitative indicators being defined. The results show that as Ph increases, the density, the specific heat ratio and the heat capacity of the NG air mixture decrease, but the gas constant and the specific heat capacity increase. CA10 moves far away from top dead centre (TDC) CA50 moves near TDC first and then far away with increasing Ph Three kinds of profiles of HRR curves with different time sequenced and HRR imbalanced characteristics appear as Ph increases. The engine thermal efficiency increases first and then decreases with increasing Ph In addition, as Ph increases, total hydrocarbons (THC) emissions decrease significantly (decrease by 97% as Ph increases from 0.45 to 0.91 with 90% PES) and nitrogen oxides (NOx) emissions increase first and then decrease.

title: The impact of equivalence ratio on performance and emissions of a hydrogen diesel dual fuel engine with cooled exhaust gas recirculation
abstract: The employment of hydrogen as a fuel in a diesel engine or dual fuel engine researched since mid 70's of the last century. As an alternative fuel, many researchers suggested hydrogen for two aspects: fuel economy and emission. In this study, the influence of cooled EGR on the engine performance and emissions of 4 cylinder duel fuel engine fueled with hydrogen and diesel investigated. The effect of the air fuel ratio (AFR) at constant engine speed (1500rpm) and optimum injection timing is presented. The acquired results show that the engine performance and emissions strongly influenced by air fuel ratio and optimum injection timing. Also, using cooled EGR has a significant effect on performance and emissions. The results indicate a trade off between hydrogen and EGR addition. Adding hydrogen increased NOx concentrations and reduced PM, while adding cooled EGR reduced NOx and increased PM concentrations. The resulted NOx and PM concentrations were the product of these two parameters.