Combustion parameter evaluation of diesel engine via vibration acceleration signal

Cold-start NOx emissions: Diesel and waste lubricating oil as a fuel additive

Homogeneous charge compression ignition (HCCI) is recognized as an advanced combustion system for internal combustion engines that reduces fuel consumption and exhaust emissions. This work studied a 150 cc air-cooled, four-stroke motorcycle engine employing HCCI combustion. The compression ratio was increased from 10.5 to 12.4 by modifying the cylinder head. Kerosene fuel was used without intake air heating and operated at various excess air ratios (λ), engine speeds, and exhaust gas recirculation (EGR) rates. Combustion characteristics and emissions on the target engine were measured. It was found that keeping the cylinder head temperature at around 120–130°C is important for conducting a stable experiment. Two-stage ignition was observed from the heat release rate curve, which was calculated from cylinder pressure. Higher λ or EGR causes lower peak pressure, lower maximum rate of pressure rise (MRPR), and higher emission of CO. However, EGR is better than λ for decreasing the peak pressure and MRPR without deteriorating the engine output. Advancing the timing of peak pressure causes high peak pressure, and hence increases MRPR. The timing of peak pressure around 10–15 degree of crank angle after top dead center indicates a good appearance for low MRPR.

In this research, the effects of three operating parameters (Diesel injection timing, propane ratio, and exhaust gas recirculation (EGR) rates) in a diesel-propane dual fuel combustion were investigated. The characteristics of dual-fuel combustion were analyzed by engine parameters, such as emission levels (Nitrogen oxides (NOx) and particulate matter (PM)), gross indicated thermal efficiency (GIE) and gross IMEP Coefficient of Variance (CoV). Based on the results, improving operating strategies of the four main operating points were conducted for dual-fuel PCCI combustion with restrictions on the emissions and the maximum pressure rise rate. The NOx emission was restricted to below 0.21 g/kWh in terms of the indicated specific NOx (ISNOx), PM was restricted to under 0.2 FSN, and the maximum pressure rise rate (MPRR) was restricted to 10 bar/deg. Dual-fuel PCI combustion can be available with low NOx, PM emission and the maximum pressure rise rate in relatively low load condition. However, exceeding of PM and MPRR regulation was occurred in high load condition, therefore, design of optimal piston shape for early diesel injection and modification of hardware optimizing for dual-fuel combustion should be taken into consideration.

Effects of methanol blending on combustion characteristics and various emissions of a diesel engine fueled with soybean biodiesel

Gasoline compression ignition (GCI) is a practicable way to obtain low emissions and high thermal efficiency of gasoline-like fuels in internal combustion engines. In this paper, the research octane number (RON) and injection strategy were coordinated to optimize the GCI engine performance and emissions under high loads. The direct injection and port injection were used to achieve two injection strategies: direct injection (DI) and port injection plus direct injection (PIDI), and the primary reference fuels (PRF) with the RON of 60, 70, 80 and 90 were used. The results show that using lower RON fuels under high loads, DI mode can achieve higher efficiency, while PIDI mode can achieve lower combustion noise at an expense of slightly lower fuel economy. When the DI mode is converted to PIDI mode with a pre-injection ratio of 30%, using PRF70 under 12 bar and the exhaust gas recirculation (EGR) rate of 40%, the gross indicated thermal efficiency and the maximum pressure rise rate are reduced by 1% and by 2 bar/°CA, respectively, while the particle emissions also decrease significantly, thus achieving low emissions and high efficiency. However, under the same load and EGR rate, DI mode produces less regulated and unregulated emissions than PIDI mode. In addition, the effect of fuel RON was obvious, the lower RON fuels exhibit obvious three-stage heat release in PIDI mode, however, PRF90 with higher RON only exhibits two-stage heat release, and the peak value of the first-stage heat release rate is also lower than those of other fuels.

Experimental study of the explosion characteristics of isopropyl nitrate aerosol under high-temperature ignition source

Gasoline is volatile and can form a flammable gas mixture with air easily. Researches on the gas explosions still need to be developed so that more effective explosion prevention techniques and measures can be proposed. The maximum overpressure rise rate and deflagration index are two important parameters for measuring gas explosion damage power. The relationship between these two parameters and the initial pressure is controversial. Razus et al. insisted that it was a linear relationship, however, Faghih et al. declared that it was an exponential relationship. In this paper, the relationship between the maximum pressure rise rate (the deflagration index) and the initial pressure is deduced and discussed. The results show that the relationship is still linear. On this basis, the deduced relationship formula is used to estimate the specific heat capacity of gasoline vapor. Results show that the estimated value is reasonable and acceptable.

<div class="section abstract"><div class="htmlview paragraph">To make an HCCI engine as a useful commercial product, the engine has to be capable of performing quick transients in a large operating range, especially in vehicle applications. HCCI combustion is kinetically controlled and has to be operated properly between two limits: misfire and knock. To achieve the correct state, the right amount of fuel/air/EGR has to be inducted into the cylinder. The amounts and ratios of the three components are highly dependent on other variables as operating conditions change. It is unrealistic and unreliable to predict the right combination of these variables without principal component analysis. Thus, the optimal response control path has to be based on the quality of the previous combustion event as well as the direction and the rate of transition.</div><div class="htmlview paragraph">The MRPR (Maximum Rate of Pressure Rise), when used between misfire and knock limit, is the key measure which carries, qualitatively and quantitatively, the most valuable information about an HCCI combustion event. While MRPR is directly proportional to the fueling rate on a cycle to cycle basis, the sensitivity of MRPR to fueling change is indicative of whether the ratio of fuel/air/EGR is proper at a given engine operating condition. Including MRPR in the control state matrix helps to define and extend healthy combustion state space and thus achieve optimal transient controllability. Since cylinder pressure can be measured and thus MRPR calculated, it can be used as feedback to provide corrective action for the next cycle both in direction and quantity.</div><div class="htmlview paragraph">In this paper, the theory behind this concept will be explored. Experimental validation of using MRPR for reliable transient control with an actual vehicle will be presented, including driving cycle tests and road tests. Methods for building MRPR physical effect observers to control HCCI transient operation are also studied. Using proxies of MRPR from extra-cylinder signal sources such as knock sensors and crankshaft dynamics would improve reliability and reduce cost thus aiding in bringing HCCI applications to market.</div></div>

Gasoline compression ignition combustion has demonstrated the potential of getting high fuel efficiency. In this work, two engine models are established in the commercial software Converge 2.3 based on the experimental results of an optical engine and a modified metal engine. The effect mechanism of mixture stratification and the influence of compound control strategy on gasoline compression ignition (GCI) combustion and soot emissions under high load condition are investigated. Results show that synergistic effect of physics and chemistry is the dominant control mechanism of GCI combustion. Stronger mixture stratification can effectively reduce the maximum pressure rise rate (MPRR) and improve the indicated thermal efficiency (ITE) and emissions; applying high EGR will significantly reduce OH radical in the cylinder and subsequently weaken the soot oxidation process, resulting in high soot emission; under the premise of reasonable NOx emission and MPRR, the soot emission can be effectively reduced with a proper advanced main injection timing. The effect of temperature on the soot oxidation process is the primary mechanism for the ultimate soot emission at different main injection timings; properly increasing the interval between the pre‐ and main injection can reduce NOx and soot emissions under the premise of ensuring that the MPRR is within the upper limit. However, the effect is not significant because of the small proportion of preinjection fuel.

In-cylinder pressure profiling for CNG/ethanol enriched biodiesel combustion

Investigations on the effect of methanol blend on the combustion parameters of dual fuel diesel engine

Gasoline compression ignition (GCI) has shown the potential to produce diesel equivalent efficiency while achieving ultra-low oxides of nitrogen (NOx) and soot emissions. Nonetheless, mechanical constraints under high load conditions have limited its implementation. A partially premixed compression ignition (PPCI) - diffusion combustion strategy has been developed to satisfactorily enable high efficiency and clean high-load GCI operation. By utilizing the PPCI-diffusion combustion strategy, this investigation assessed GCI performance experimentally on a heavy-duty diesel engine. Fuel injection strategy (start of injection, split ratio, and injection pressure) and air-handling system boundary conditions were systematically studied as key parameters under medium-to-full load engine operation. Across different engine operating points, GCI optimized using a one-factor-at-a-time approach demonstrated diesel-like fuel efficiency and emissions compared to the diesel baseline over an engine-out NOx range of 2–7 g/kWh. A design of experiments (DoE) based injection strategy optimization was also conducted at the highest fuel efficiency point, targeting 2.8 g/kWh engine-out NOx. The sensitivity of GCI performance to the fuel injection strategy was thoroughly characterized. The optimized fuel injection strategy showed equivalent diesel efficiency with an enhanced NOx-smoke trade-off without exceeding the mechanical constraints on maximum pressure rise rate (MPPR) and peak cylinder pressure (PCP).

Cylinder pressure reconstruction based on complex radial basis function networks from vibration and speed signals

Application of methanol and optimization of mixture design over the full operating map in an intelligent charge compression ignition (ICCI) engine

Design, development and testing a hybrid control model for RCCI engine using double Wiebe function and random forest machine learning