Peak Combustion Pressure Research Articles

Experimental investigation the effects of Miller cycle coupled with asynchronous intake valves on cycle-to-cycle variations and performance of the SI engine

A novelty of the Miller cycle with the asynchronous intake valve (AIVMC) was proposed and used in the test SI engine. In addition, the effects of the AIVMC on the combustion cycle-to-cycle variations and performance of the test SI engine were analyzed, and then compared to the experimental results of the Otto cycle (OC). The results indicated that the transient in-cylinder pressure distributions were discrete, and the peak combustion pressure distribution gradually dispersed with decreasing the intake valve spacing angle. The coefficient of variation of the indicated mean effective pressure (COVIMEP) of the test SI engine equipped with AIVMC were respectively 1.45% and 2.79% with using the spacing 90°CA and 50°CA under the low load, while the COVIMEP of the test SI engine equipped with AIVMC were respectively 0.79% and 3.45% with using the spacing 90°CA and 50°CA under the medium load. The application of AIVMC in the test SI engine effectively reduced the pumping mean effective pressure (PMEP) compared with OC. Under the operating condition of 2600 rpm and 8 bar, the EER of the test SI engine equipped with AIVMC (spacing 90°CA) was 13.0, which respectively increased 26.2% and 36.8% compared to the AIVMC (spacing 50°CA) and OC.

A numerical investigation of injector hole configuration and injection parameters in a dimethyl ether fueled DICI engine

AbstractThe lower calorific value of dimethyl ether (DME) is approximately 65% of that of diesel; therefore, a higher quantity of DME must be supplied per cycle to generate the same magnitude of power. A retrofitted DME‐fueled engine generally uses a longer fuel injection duration to provide the excess fuel mass. The present work seeks to find the most appropriate way to increase the mass flow rate of a DME‐fueled direct‐injected compression ignition engine by varying the number of nozzle holes, nozzle hole diameter, and injection pressure. The results show that increasing mass flow rate increases peak combustion pressure and heat release rate but decreases combustion duration. Increasing the number of injector holes increases indicated specific fuel consumption (ISFC) and exhaust emissions (NOx, HC, and CO) due to mixing between unburned fuel spray and neighboring combustion products. Increasing the nozzle hole diameter or fuel injection pressure increases spray tip penetration and improves fuel‐air mixing before combustion initiates. Increasing the nozzle hole diameter by merely 22 μm than the baseline injector reduces ISFC and exhaust emissions at a slightly retarded start of injection (SOI). However, the lowest ISFC was found at the 30 MPa injection pressure at the most advanced SOI, at the expense of higher NOx.

Experimental investigation on combustion characteristics and influencing factors of PODE/methanol dual-fuel engine

PODE/methanol dual-fuel combustion mode was conducted on a four-cylinder common-rail engine with PODE direct injection and methanol intake fumigation. This study is aimed to investigate the effects of methanol substitution ratio (MSR), injection timing and inlet temperature on in-cylinder combustion, emission characteristics and fuel economy of dual-fuel engine. Results show that with the increase of MSR, the ignition delay of dual-fuel engine is prolonged, and the COV increases. At medium and small loads, the peak combustion pressure decreases, and the combustion phase is delayed. At high load, the peak values of heat release rate and combustion pressure increase, combustion duration is shortened, and slight knock occurs at 40% MSR. Dual-fuel mode has benefits in reduction of NOx and soot, while increases NO2 and HCHO emissions. With the delay of injection timing, combustion duration is first prolonged and then shortened. The excessive delay of injection timing leads to increased fluctuation of combustion pressure, and partial misfire occurs. With the increase of inlet temperature, the peak values of heat release rate and combustion pressure increase significantly, combustion duration is shortened, and the COV increases. At the inlet temperature of 65 °C, methanol spontaneous combustion occurs near TDC, and thermal efficiency increases to 44.6%.

Experimental Investigation on Effects of Fuel Injection Timings on Dimethyl Ether (DME) Energy Share Improvement and Emission Reduction in a Dual-Fuel CRDI Compression Ignition Engine

The impacts of different fuel injection timings (base (15BTDC) and retarded (12BTDC)) on a single cylinder common rail direct injection (CRDI) compression ignition (CI) engine under dual fuel mode (DME-diesel) was examined at the maximum torque with the engine speed of 2200 rpm. The diesel (liquid) fuel was directly injected into the engine’s cylinder at the end of the compression stroke and Dimethyl ether (gas) fuel was injected into the intake system of the engine during the suction stroke. The maximum DME energy share (DME ES) with base injection timing (15BTDC) under controlled auto-ignition (CAI) is limited to 52%. Delayed injection timing prevents knock occurrence to a certain extent due to the lower peak combustion pressure and temperature. The DME energy share (DME ES) without knocking is extended to 58% with delayed injection timing (12BTDC). Three stages of combustion (low-temperature region, high-temperature region and diffusion combustion region) were observed under DME-diesel mode. The low-temperature region (LTR) occurs at the temperature range from 700–900 K whereas high-temperature region (HTR) was at the temperature beyond 1000 K. The cyclic variations with the coefficient of variation (COV) of the important parameters (peak in-cylinder pressure, peak rate of pressure rise and indicated mean effective pressure) were analyzed. NOx emission decreased along with zero smoke emission. However, the other emissions such as CO, HC increased marginally with retarded timing. The notable point emerged from this study is that the retarded injection timing is a promising strategy for enhancement of DME energy share with reduced emissions.

Effect of MnO2 morphology on the thermal properties and combustion behavior of nano-Al/MnO2 thermite

Al/granular MnO2 and Al/rod MnO2 thermite samples were prepared to investigate the effects of different morphologies of MnO2 on the thermal properties and combustion behavior of nano-Al/MnO2 thermite. The morphology and thermal properties of the thermite were characterized by field emission scanning electron microscopy (FE-SEM), x-ray diffractometry (XRD), and differential scanning calorimetry (DSC). DSC results show that the Al/rod MnO2 releases 1274.39 J·mol−1 heat, which is 292.58 J·mol−1 more than the Al/granular MnO2. The initial reaction temperature of Al/rod MnO2 is 567.39 °C, which is delayed by 17.39 °C versus 550 °C of Al/granular MnO2. Non-isothermal thermodynamic analysis was used to measure the activation energy of Al/rod MnO2 to be 234.36 kJ·mol−1, which is 46.53 kJ·mol−1 higher than that of Al/granular MnO2. This corresponds to an increase in the ignition temperature in the DSC curve and indicating a higher safety profile. In the open burning experiment, the burning time of Al/granular MnO2 was longer and sparks sputtered around the flame. The Al/rod MnO2 has a large combustion flame and a fast combustion rate. The light intensity peaks of the two groups of samples are close in the light intensity test. The light intensity existence time of Al/rod MnO2 is 0.0146 s, which is 0.094 s shorter than Al/granular MnO2. This shows that the combustion rate of Al/rod MnO2 is much faster than that of Al/granular MnO2. The closed-tube combustion experiment shows that the combustion wave velocity of Al/rod MnO2 increases first and then decreases; the maximum wave velocity reaches 339.6 m·s−1, and Al/granular MnO2 cannot self-propagate combustion in the microporous environment. In the constant volume combustion experiment, the peak combustion pressure of Al/rod MnO2 is 0.938 Mpa, and the peak value of Al/granular MnO2 combustion pressure is 0.581 Mpa; the difference is obvious. This shows that the rod MnO2 gas production performance is better. According to the duration of the pressure peak, the burning speed of Al/rod MnO2 in the light intensity test is confirmed again to be much faster than that of Al/granular MnO2. The Al/rod MnO2 is better than Al/granular MnO2 in thermal and combustion performance and is also safer. This provides a basis for future performance and safety research on aluminothermic materials.

Influence of Palm Oil Biodiesel Blend Preheating on Performance Parameters, Emissions and Combustion Characteristics in a Stationary Diesel Engine

This research evaluates the effect of preheating in different blends of palm oil biodiesel in a stationary diesel engine. For the research development, the characteristics of performance, emissions (CO, CO2, NOx, HC, and smoke opacity), combustion chamber pressure, and heat release rates are evaluated. Experimental tests were conducted at three load conditions (50%, 75%, and 100%) and three biodiesel blends (BP5%, BP10%, and BP15%). To study the effect of preheating, a fuel injection temperature of 30 °C to 70 °C was set. The results obtained show a 6.40% increase in BSFC and a 4.41% reduction in engine BTE when running with biodiesel blends. However, preheating in biodiesel blends led to lower BSFC and higher BTE by 2.08% and 2.12%. The preheating of palm oil biodiesel (BP5%, BP10%, and BP15%) favored the decrease in CO, HC, and engine smoke opacity emission levels by 29%, 37.31%, and 7.84%. The additional presence of oxygen molecules and the increase in fuel injection temperature contribute to the formation of NOx emissions. The increase in injection temperature causes an increase in peak combustion pressure levels and heat release rate by 2.53% and 2.41%. In general, preheating palm oil biodiesel is a promising strategy to minimize the negative effects caused by the high density and viscosity of this type of fuel.

Effects of Multiple Injection Strategies on Heavy-Duty Diesel Energy Distributions and Emissions Under High Peak Combustion Pressures

Peak combustion pressures (PCP) are increased in heavy-duty diesel engines to obtain higher thermal efficiency. Fuel injection strategy has been a major measure to improve the combustion and emissions of diesel engines. But most existing work of multi-injection strategies was not limited by PCP or was conducted under lower PCP (∼15 MPa). In this study, an experimental study is conducted to further improve the understanding of injection strategies on engine performance under a relative higher peak combustion pressure at 20 MPa. The four tested injection strategies are single main injection, pilot-main injection, main-post injection, and pilot-main-post injection. The effects of PCP on brake thermal efficiency (BTE) and other engine performances are also investigated under the same NOx emissions conditions. Results indicate that more advanced injection timing can obtain higher BTE, while the injection pressure has less effects on BTE as it is higher than 120 MPa. For double-injection, the smaller interval on pilot-main or main-post and the less pilot or post mass improves BTE and emissions. The PCPs are linearly correlated to the BTE, peak average temperature, and peak pressure rise rate (PRR), and the increment of BTE, peak average temperature, and peak PRR are about 0.3%, 30 K, and 0.1 MPa/CA for every 1 MPa increase in PCP, respectively. This also means that the improvement on BTE by the increase of PCP imparts greater thermal and mechanical loads on engine materials and components. At 20 MPa PCP, based on the optimized injection strategies, the BTE of all four strategies is about 42.8%, and the peak PRR of all four strategies is about 0.8 MPa/CA. At a given NOx emission of 17.4 g/kWh and approximate 20 MPa PCP, all four injection strategies have minor effects on distribution of fuel energy and emissions. Therefore, it can be concluded that the injection strategies have fewer effects on BTE and emissions at the higher peak combustion pressure of 20 MPa; the main purpose of injection strategies is to reduce the peak PRR or reach the potentially required temperature for aftertreatment devices.

Experimental study on the effects of ethanol blends on the combustion process, power performance and emission reduction of a motorcycle spark-ignition engine

This work investigates the effects of ethanol-blended gasoline fuels on a motorcycle engine's power performance and emission reduction compared with conventional gasoline fuel. Experiments were conducted on different ethanol-blended fuels E0, E30, E50, E85, and E100 for a spark-ignition motorcycle engine at various engine speeds and loads. The brake power increased with the ethanol blending ratio; E100 fuel produced the highest brake power, and E0 fuel made the lowest. The rise of ethanol in blends contributed to the retarding of ignition and reducing the peak combustion pressure and maximum heat release. The CO emission for E100 and its blends was less than gasoline fuel. The HC emissions decreased with the increase in ethanol blending ratio, and the difference was more considerable for E0 and E100 fuels at low engine speed than at higher engine speeds. Compared with E0 fuel, ethanol blends had lower NOx emissions and greater reduction levels.

Cycle-to-cycle combustion analysis in hydrogen fumigated common-rail diesel engine

An experimental cycle-to-cycle analysis in multi-cylinder automotive common-rail compression ignition engine was performed to understand better the combustion in the hydrogen fuelled diesel engine. Hydrogen was fumigated in intake line at a wide-ranging from 0 lpm to 50 lpm in steps of 10 lpm. Test engine was operated at three different loads for a constant engine speed. The relative air–fuel ratios were between 1.55 and 3.31. The combustion occurred with an excess of air in all tests. Combustion data of 120 cycles were used to analyse the cyclic variations, determined by standard deviation of the cylinder pressure. Cyclic variations, coefficient of variance (CoV), standard deviation, frequency, and average value of peak combustion pressure (Pmax), maximum pressure rise rate (PRRmax), indicated mean effective pressure (IMEP), mass fraction burned (MFB), and MFB10-90 duration were analysed. Results showed that for all hydrogen addition levels, CoVs of Pmax, IMEP and MFB10-90 were always found below 3% at all loads, and PRRmax values with hydrogen operations in each cycle were under the limit of knocking combustion. Engine load was the most important factor to affect to CoV, standard deviation, and frequency of the combustion parameters. Minor cyclic variations in MFB traces were found at all engine loads and hydrogen addition levels, which agreed well with the cylinder pressure traces. Frequencies of Pmax and IMEP were moderate in low and medium loads, but reduced in high load, and also the values of Pmax and IMEP in high load were distributed in a wider range compared to low and medium loads. MFB10-90 duration increased for dual-fuel modes, its frequency was decreased, and its distribution was extended with hydrogen addition. Trend of standard deviation was mostly similar to that of CoV for the studied combustion parameters. Furthermore, variations of correlation coefficient (R) among Pmax, PRRmax, IMEP, and MFB10-90 were discussed in this paper, and the highest R value was found between IMEP and Pmax.

A Simulation of Four Stroke Marine Diesel Engines to Predict Internal Cylinder Characteristics

This paper introduces a simulation of four-stroke marine diesel engines. The submodel of a particular cylinder was carried out, based on the first law of thermodynamics, programmed by Matlab/Simulink program, which describes the relations among internal characteristics, including cylinder performance parameters, heat release, heat loss, and pressure. The heat release is based on the Wiebe function and the heat loss is based on the Woschni function to build submodels. From the result of the model, the indicated pressure of a single cylinder was taken, the brake power of the engine could be estimated through this pressure. The object of the simulation is a new engine, hence the technical documents and test records provided by the manufacturer are sufficient. The model got the input parameters from this and the key outputs of the model (for example the brake power, peak combustion pressure, specific fuel consumption) were compared with the test records to adjust and make it more accurate. These gaps were not over 5%, therefore, this model can be used to predict key complicated internal cylinder characteristics, for example, the pressure, temperature, and thermal efficiency of engines.

Hydrogen-diesel co-combustion characteristics, vibro-acoustics and unregulated emissions in EGR assisted dual fuel engine

This work investigates the co-combustion characteristics of the hydrogen-diesel dual fuel with exhaust gas recirculation (EGR). The experiments were performed on a retrofitted duel fuel compression ignition engine for the entire engine load spectra, while the maximum hydrogen energy share in the study was 30%. Further, EGR was varied up to 10% to examine its effect on the hydrogen-diesel co-combustion and other relevant characteristics. It was found that although, hydrogen exhibit contrasting effects on the combustion at low and high loads, EGR continually degraded the peak combustion pressure. However, interestingly, the combustion’s variability improved on addition of EGR at higher loads, despite EGR’s detrimental effect on variability at lower loads. In addition, combustion noise and engine vibration were also studied with the aim to understand the effect of fuels and their combustion stability on such parameters. The relatively lower participation of hydrogen tends to reduce the vibrations, however, EGR leads to higher vibrations in the engine. The combustion noise however reduced with addition of hydrogen and EGR at lower loads. Further, the cumulative effect of EGR- hydrogen on the much unattended but harmful unregulated emissions was also investigated, and a synergy between the hydrogen addition and EGR was observed in this study. The present study showcases the key concerns as well as advantages in the EGR assisted hydrogen diesel combustion.

Study on the Influence of EGR on the Combustion Performance of Biofuel Diesel at Different Ambient Simulated Pressures

In order to explore the influence of EGR at different altitudes on the performance of biofuel diesel engines, a comparative experimental study is conducted with the biodiesel–ethanol–diesel B15E5 (biodiesel with 15% volume fraction, ethanol with 5% volume fraction and diesel with 80% volume fraction) mixed fuel at different EGR rate and different atmospheric pressure. The experimental results show that diesel engine power performance and economy goes up with the increase of atmospheric pressure, and it decreases with the increase of EGR rate. At 2200 rpm, the improvement range of medium and high diesel engine load is 1.5–6.8%, and that of 1800 rpm is 2.8–11.7%. At the same atmospheric pressure, with the increase of EGR rate, the power and economy turn worse. The peak combustion pressure and heat release rate both increased with the increase of the atmospheric pressure at full load. At the same atmospheric pressure, peak combustion pressure and peak heat release rate fall with the increase of EGR rate. At part load, firstly, smoke emissions fall with the increase of the load and then rise. As the atmospheric pressure goes up, the smoke emissions show a downward trend, with a decline of 6.6–40%, while the NOx emissions show a rising trend, with an increase of 1.2–8.5%. At the same atmospheric pressure, the smoke emission increase with the increase of EGR rate by 9–12.5%, and the NOx emissions increase with the decrease of EGR rate by 2.5–6.8%. The HC and CO Emissions decrease with the increase of atmospheric pressure. HC emission decreases by 9.3–19.1%, and CO emission decreases by 2.9–16.6%. At the same atmospheric pressure, the HC emission decreases with the increase of the EGR rate by 3.3–4.5% at medium and high loads, and the CO emission increases with the EGR rate by 3.1–4.5%.

Effects of Fe2O3 and Al2O3 nanoparticle-diesel fuel blends on the combustion, performance and emission characteristics of a diesel engine

This research investigates the effects of the addition of Fe2O3 and Al2O3 nanoparticles (30, 60 and 90 ppm) and Fe2O3–Al2O3 hybrid nanoparticles to pure diesel fuel on the combustion, performance and emission characteristics of a diesel engine. The results indicated that fuel blends improved the combustion (in-cylinder pressure and heat release rate), performance (power, fuel consumption and thermal and exergy efficiency) and emission characteristics of the engine. The results showed that the peak combustion pressure increased by 4% and the heat release rate was improved by 15% in comparison with pure diesel with the addition of the nanoparticles. Moreover, the rate of pressure rise increased by 18% compared to pure diesel with nanoparticle additives. Based on the results, the effects of Fe2O3 fuel blends on brake power, BTE and CO emission were more than Al2O3 fuel blends, such that it increased power and thermal efficiency by 7.40 and 14%, respectively, and reduced CO emissions by 21.2%; moreover, the blends with Al2O3 nanoparticle additives in comparison with Fe2O3 nanoparticle blends showed a better performance in reducing BSFC (9%), NOx (23.9%) and SO2 (23.4%) emissions. Overall, the Fe2O3–Al2O3 hybrid fuel blend is the best alternative if the performance and emission characteristics of the engine are both considered.

Flame propagation characteristics of mixed pulverized coal at the atmosphere of gasification

The leakage of pulverized coal easily results in fire and explosion accidents during coal gasification process. A vertical pipeline was built with the high-speed camera, micro-thermocouple and pressure sensor to obtain the characteristics of flame propagation. Based on the atmosphere of coal gasification, the effects of the spraying time, particle conditions, and rank of the pulverized coal were studied. The results show that the peak temperature, combustion pressure and velocity increase first and then decrease with the increasing of spraying time. When the particle size pulverized coal is 200 mesh, the peak pressure reaches the highest value. The flame propagation characteristics are similar at different concentrations of pulverized coal and the maximum appears at 333 g/m3. In addition, the peak temperature of the pulverized coal flame increases with the increasing of the proportion of long-flame coal in the mixed coal. The optimum characteristics of flame propagation appear at different ratios of mixed coal due to the effect of coal rank.

Experimental study on the combustion characteristics of premixed methane-hydrogen-air mixtures in a spherical closed chamber

In this study, we conduct premixed combustion experiments on methane-hydrogen-air mixtures based on an experimental platform of a closed spherical chamber. The flame images, combustion pressure, and ion current signal of premixed combustion under different hydrogen fractions and different initial conditions are analyzed. The flame front is affected by turbulence to form cellular structures. As the hydrogen content increases, the crack and cellular structures of the flame front increase, and the scale decreases. The Markstein length decreases, and the flame stability decreases because of the addition of hydrogen. For dilute hydrogen conditions, the stretch flame speed increases linearly with the addition of hydrogen, and the concentration of hydrogen has a significant influence on the moment when the ion current signal appears. Under rich hydrogen conditions, the stretch flame speed increases exponentially with the addition of hydrogen, and the ion current signal curve is hardly affected by the hydrogen content. The peak combustion pressure in a turbulent environment is slightly higher (less than 0.5 bar) than that in a laminar environment. Turbulence accelerates the combustion velocity, and the peak combustion pressure occurs significantly earlier. However, with the addition of hydrogen, the difference between the time of peak combustion pressure in the laminar and turbulent environments decreases gradually.

Scale effect of porous mesh on the inhibition mechanism of wheat dust flame

The combustible features of wheat dust easily induce a potential hazard in its processing and application. To clearly reveal the effects of porous mesh parameters on the flame propagation of wheat dust, a vertical combustion pipeline together with the data collecting by the high-speed photography and fine thermocouple was built. Results indicate that with the increase in the mesh scale, the dust combustion and peak temperature are intensified first and then decreased with a darker luminescence. The increasing mesh number shows an inhibition effect on both peak temperature and combustion pressure, but an accelerating first and then weakening effect on flame velocity. A smaller particle size contributes to a more complete combustion, causing a higher peak temperature and flame velocity. At the particle mass of 2.5 g, the maximum value of peak temperature, flame velocity and combustion pressure were obtained during the flame propagation.

Application of Response Surface Methodology for Optimization of Fuel Injection Parameters of a Dual Fuel Engine Fuelled with Producer Gas-Biodiesel blends

ABSTRACT The present work reports the development of a mathematical model to establish a correlation between controllable engine input parameters and their dependent responses over a varied range of engine loadings. Brake thermal efficiency (BTE), peak combustion pressure, and exhaust gas temperature (EGT) are chosen as a response while engine load, pilot fuel injection timing (FIT), and pilot fuel injection pressure (FIP) are taken as controllable input. The response surface methodology (RSM) has been used for the model development based on multilinear regression analysis and the design of experiments techniques. The experimental data for model development was collected through lab-based experiments carried out using diesel engines in dual-fuel mode. The dual-fuel engine was powered with producer gas as the main fuel and waste cooking oil biodiesel as pilot fuel. The best possible combination of input parameters optimized by RSM helps in the improved and stable operation of the dual-fuel engine. Furthermore, the developed model can predict the output responses very close to experimental results. The model robustness is verified with high values of correlation coefficients R2 for all three response variables.

Experimental study the impacts of the key operating and design parameters on the cycle-to-cycle variations of the natural gas SI engine

High cycle-to-cycle variations (CCV) in the spark ignition (SI) engine will not only lead to incomplete combustion and even misfire, but also affect the fuel economy and even influence the drivability and conformability of a vehicle, particularly at the lean-burn condition. However, the detail information about the root causes of CCV are still relatively limited, particularly the natural gas SI engine. In this paper, the impacts of the key operating and design parameters were investigated on the CCV of the high compression ratio SI natural gas engine under lean mixture condition. The results indicated that the in-cylinder pressure distribution tended to be concentrated, the number of partial burning or incomplete combustion cycles also reduced with increasing the engine speed. With increasing the load, the in-cylinder pressure distribution, peak combustion pressure and its location were tended to be concentrated. Furthermore, the number of the partial combustion or post combustion cycles declined from low-load to medium- and high-load zones. Moreover, the relationship between the peak combustion pressure and its location was almost linear with increasing the engine load. Unfortunately, with further increasing engine load, in-cylinder pressure traces started to disperse slightly. Under the low-load condition, in-cylinder pressure traces were tended to be concentrated with increasing compression ratio (CR). As CR continually increased, its influence on the in-cylinder pressure distribution decreased. In addition, the number of the partial combustion or post combustion cycles decreased with increasing CR. However, under the high-load condition, increasing the CR has slightly effects on the in-cylinder pressure distribution.

Forecasting of a boosted locomotive gas diesel engine parameters with one- and two-stage charging systems

Conversion of locomotive engines for operation on natural gas lowers considerably expenses for fuel and reduces exhaust emissions which makes it possible to omit large and expensive aftertreatment systems. The permanent need to raise the engine power requires a considerable increase of the boost pressure. This can be realized by using a high pressure turbocharger or a two-stage charging system. In the research, parameters of a high boosted D200 6-cylinder locomotive engine having D/S=200/280 mm are forecasted using a one-zone model developed in MADI. An analysis was carried out to explain why the 1st stage compressor of the two-stage charging system should be specially profiled to have its map tilted to the right. Calculations were performed for the gas diesel engine having a break mean effective pressure (BMEP) 2.7 MPa with one and two-stage charging systems. In both cases, close fuel efficiency was obtained, though for the two-stage charging system, the boost air pressure was higher. The engine with one turbocharger had no reserves for further power augmentation while the two-stage charging system enabled to increase the boost air pressure further. Therefore, parameters of the engine having a higher BMEP 3.2 MPa were calculated. In that case, not to exceed the peak combustion pressure, a retarded fuel injection was used which resulted in fuel efficiency drop by approximately 1.5%.

Investigation on combustion characteristics of cyclopentanol/diesel fuel blends in an optical engine

Cyclopentanol is a promising alternative biofuel for automobiles. In this study, an optical engine was employed to investigate the effects of cyclopentanol blending ratios on combustion characteristics. Cyclopentanol was blended with diesel by 10% and 20% volume, denoted as CP10 and CP20, respectively. Comparison tests between blends and diesel (denoted as D100) were performed under three injection pressures (100, 120, and 140 MPa) and four injection timings (−6°, −9°, −12° and −15° crank angle after top dead center (°CA ATDC)). The experimental results indicated that the addition of cyclopentanol prolongs the ignition delay, shortens the combustion duration and improves the indicated thermal efficiency. As the injection pressure increases or the injection timing advances, the peak combustion pressures (PCPs) and peak heat release rates (PHRRs) increase. Compared to D100, the PCPs and PHRRs of cyclopentanol/diesel fuel blends are lower and decrease with the increase of cyclopentanol ratio. Blending cyclopentanol in diesel is effective in reducing soot emission, and the reduction effect weakens as the injection pressure increases or the injection timing advances. CP10 is superior to CP20 according to the comprehensive evaluation of combustion and emission, especially at the injection timing of −12°CA ATDC under the injection pressure of 140 MPa.