Antiknock Properties Research Articles

HCCI Combustion Engine Fueled with DME and DME-Reformed Gas

Dimethyl ether has been studied as a fuel for homogeneous-charge compression-ignition combustion (HCCI) engine by many researchers. However, there is a difficulty to control the ignition timing in accordance with the engine load. This research newly proposes a DME fueled HCCI combustion engine system with an ignition control by DME-reformed gas (DRG). Authors claim that the DRG that contains hydrogen and carbon monoxide with high anti-knock properties can control the auto-ignition of DME. In the system, the DRG is to be produced by an on board DME-reformer utilizing exhaust heat from the engine. This paper analyzes characteristics of HCCI combustion of DME and two types of DME-reformed gases. One type is by partial oxidation, and the other is by steam reforming. The experiments are conducted by varying the proportion of the fuels and equivalence ratio. The overall thermal efficiency based on DME is also analyzed for ideal reforming conditions.

メタノール改質ガスを用いた排熱回収型HCCI燃焼機関における改質ガス組成の影響(予混合圧縮着火燃焼と新燃焼(2),予混合圧縮着火燃焼と新燃焼)

One of the authors has proposed an HCCI combustion engine system that was fueled with dimethyl ether (DME) with a high cetane number and methanol-reformed gas (MRG) with a high anti-knock property in the previous research. In the system, both DME and MRG are to be produced from methanol by onboard-reformers utilizing the exhaust-heat from the engine. High overall thermal-efficiency has been achieved over a wide operable-range by both the lean HCCI combustion and the waste-heat recovery. While the MRG used in the research was the thermally decomposed methanol, methanol can be reformed to various compositions of hydrogen, carbon monoxide and carbon dioxide. This research aims to find the optimum MRG composition for the system in terms of the ignition control and the overall thermal efficiency.

Synthesis of 1- tert-butoxy-2-propanol (PGTBE) from propylene glycol and isobutene in a packed trickle-bed reactor on acid catalysts

1- tert-Butoxy-2-propanol has been synthesized from propylene glycol and isobutene over two solid acid catalysts, montmorillonite and Amberlyst 15, in a packed trickle-bed reactor operating under different experimental conditions, and its antiknock properties as an oxygenate gasoline additive have been evaluated. The reaction on Amberlyst 15 fitted first-order kinetics for isobutene ( k′=0.37 h −1) for a molar ratio propylene glycol to isobutene of one.

The rise and fall of leaded gasoline

Leaded gasoline has become one of the few “environmentally unsafe” products to be forced out of the market place. The history of lead additives in gasoline is outlined, from the discovery of the antiknock properties of tetraethyllead in 1921 (the first gallon of leaded gasoline was sold on 2 February 1923 to a motorist in Dayton, Ohio), to recent measures to remove lead from the gasoline of the 1980s. This report provides an historical backdrop to the continuing debate on environmental lead pollution.

Selective hydrocracking of raffinates

The most acceptable method for processing raffinates to improve their antiknock properties is selective hydrocracking. As a result of selective cracking of the straight-chain paraffinic hydrocarbons present in raffinates, an octane number gain of 15-20 may be achieved. The authors list certain process indexes for selective hydrocracking of 62-105/sup 0/C cut (benzene-toluene) and 105-140/sup 0/C cut (xylene). It is shown that the improvement of the antiknock properties of raffinates by selective hydrocracking may change the structure of automotive gasoline production quite substantially.

Antiknock efficiency of oxygen-containing compounds in various fuels

UDC 621.434.057.3 Extensive research is being conducted today on the possibility of improving the antiknock properties of automative gasolines by the addition of methanol, ethanol, methyl tert-butyl ether (MTBE), and water. Within the framework of this overall research effort, it is particularly important to study the antiknock efficiencies of these additives in fuels with various hydrocarbon compositions, with the aim of optimizing the component composition of gasolines in order to obtain the maximum effect from the use of the additives. Here we are reporting on an investigation of the antiknock efficiencies of methanol, ethanol, MTBE, and water in fuels based on paraffinic or aromatic hydrocarbons, As such fuels we used blends of isooctane with n-heptane (IHB) and toluene with n-heptane (THB), preparing three blends in each series with octane numbers of 50, 64, and 77 (Motor Method). The tests were performed in a UIT-65 unit. The additives were fed to the engine cylinder separately (not blended with the fuel) through a supplementary feed system. The antiknock efficiency of each additive was rated according to the gain in fuel octane number. The results obtained in these tests are presented in Fig. i. A comparison of the data for the IHB and THB with identical octane numbers shows that the susceptibility to methanol is higher for the IHB than for the THB (Fig. la); i.e., methanol, when it is added to the IHB, gives a greater increase in octane number than When it is added to the THE. With increasing octane number of the original fuel (with increasing content of either isooctane or toluene in the blend), this difference in the behavior of methanol is manifested to a greater degree. Analogous results are obtained when ethanol or MTBE was added to the fuels (Figs. ib and c). In contrast, the susceptibility to water is higher for the IHB than for the THB (Fig. id). These results are in good agreement with theoretical concepts of the features of oxidation and flaranability of different classes of hydrocarbons. Most paraffinic hydrocarbons are characterized by two-stage ignition with an intermediate cool-flame stage. In the ignition of aromatic hydrocarbons, the cool-flame stage is either absent or is much less distinct than with paraffinic hydrocarbons. It was shown in [I] that the influence of alcohols and MTBE on the ignition of hydrocarbons consists essentiall Z of a retardation of the appearance of the cool-flame stage and a lowering of the intensity of this stage. In this connection, we should expect less influence of these additives on the ignition of fuels for which the coolflame stage is not distinct. This means that the antiknock efficiency of the additives in such fuels will be lower than in fuels with a well-developed cool-flame stage. The effect of adding water to fuel consists mainly of a lowering of the temperature of the working charge in the engine cylinder. Correspondingly, the effect should depend on the temperature sensitivity of the fuel, i.e., on how much the tendency of the fuel toward detonative ignition changes with changes in the temperature regime of engine operation. The sensitivity of fuels is also determined by thekinetic features of their oxidation. Paraffinic and naphthenic hydrocarbons have low sensitivity to temperature because of their twostage ignition; correspondingly, the ignition lag (and hence the tendency to detonate) will chanse very little over a broad range of temperatures. The ignition lag of aromatic hydrocarbons increases rapidly with decreasing temperature, and hence they have an extremely high temperature sensitivity. For the IHB, the temperature sensitivity, as characterized by the difference between octane numbers determined by the Research and Motor Methods, is equal to 0; for the THB with octane numbers of 50, 64, 77, the respective temperature sensitivities are 6, 8.7, and ii.i. Correspondingly, we should expect that a lowering of the temperature of the working charge due to the addition of water will have a greater effect on the knock resistance of the THB than of the IHB. This difference should be greater in the case of fuels with a higher temperature sensitivity, and this is confirmed by the experimental data.

Blends of isomerizates with methyl tert-butyl ether as components of unleaded automotive gasoline

Experimental samples of unleaded AI-93 gasoline with the additions of methyl tert-butyl ether (MTBE) and isomerizates with octane numbers of 78.5-90.5 were formulated with catalytic reformer naphtha base stocks having octane numbers of 94.9 and 90.5. The physicochemical and anti-knock properties of the components are presented in tables. It is found that the use of MTBE along with isomerizates in the composition of AI-93 gasoline makes it possible to increase the total yield of automotive gasolines relative to the crude oil processed, and to improve the technoeconomic indexes of gasoline production. Of the samples of AI-93 gasoline that were investigated, the best from the standpoint of quality and technoeconomic indeces are samples 8 and 167, containing (respectively) 7% and 5% MTBE and 23% and 30% isomerizate with octance number 78.5 and 83.9.

Sulfur resistance of selective hydrocracking catalyst based on synthetic erionite

Selective hydrocracking is most often used to improve the antiknock properties of reformates, raffinates remaining after extraction of aromatic hydrocarbons from aromatic naphthas, and isomerizates [i]. In a number of cases, however, this process may be applied to raise the octane number of straight-run naphtha cuts. Here, the sulfur resistance of the selective hydrocracking catalysts may become the decisive factor in selecting the processing scheme for these cuts.

A Study of Micro Stratified Combustion Engine : 2nd Report, Combustion Characteristics of Micro Stratified Combustion Engine

An experiment of a single cylinder spark ignition engine was conducted at a constant engine speed, fixed air flow, and using gasoline as a fuel, to demonstrate the effects of micro-stratified combustion, which was verified in the first report, on combustion characteristics. The characteristics of the micro-stratified combustion engine are those of retarded MBT spark timing, shortening of heat release lag duration, and lenghthening of first half of the heat release duration, while the combustion duration shows little change. The cyclic variation (such as standard deviation) in the peak cylinder pressure and so forth are much less for a fully vaporized fuel-air mixture than for the micro-stratification. Also the experimental results show that micro-stratified combustion appears to have a considerable potential for the anti-knock property.

Optimization of component composition and antiknock properties of AI-93 gasoline

Optimization of component composition and antiknock properties of AI-93 gasoline

Manganese pollution in the city environment and its relationship to traffic density.

As lead is phased out of gasoline, other additives with anti-knock properties, particularly organic manganese compounds, are being substituted. Unavoidably, such compounds go through the combustion process, are eliminated in exhaust gases, and become part of the city environment. To obtain some indication of the extent of this new pollution street soils from various locations in a heavily trafficked city (Newark, NJ) were analyzed for manganese and lead by atomic absorption. Highly signigicant inverse relationships were found between the concentrations of both contaminants and distances from major traffic arteries. Strong circumstantial evidence is thus provided that: 1) manganese pollution is occurring, along with lead, in the city environment; 2) this new pollution is related to traffic density; and 3) the most likely sources are automobile exhausts. This suspicion is further strengthened by the significant correlations observed between manganese and lead contents in children's blood, suggesting a common source for both. Substantiation of the safety of this practice of adding manganese to gasoline is needed.

Antiknock properties of AI-93 gasoline containing tetramethyllead (TML)

Antiknock properties of AI-93 gasoline containing tetramethyllead (TML)

Antiknock characteristics of liquefied petroleum gases

1. The antiknock characteristic curve of propane, which is a basic component of LPG, is opposite to that of AI-93 gasoline. 2. The antiknock characteristic curves of n-butane and AI-93 gasoline are very similar to each other. 3. Studies of the antiknock properties of gaseous fuels have shown that (a) the octane numbers of gaseous fuels as determined by the research and motor methods do not provide any grounds for a conclusive determination of the allowable compression ratio for an engine; and (b) when an automotive vehicle is converted from gasoline to LPG, a change is required in the performance characteristics of the correction devices in the electrical ignition system.

Investigation of antiknock properties of liquefied petroleum gas in a ZIL-375 engine

1. The octane numbers of various LPG's as determined by the motor and research methods reflect quite accurately the actual knock resistance of these fuels in the engine. 2. In using LPG as motor fuel, the engine air intake should be located outside, not under the hood, since this will give stable operating indices of the engine. 3. For fuel with high knock sensitivity, as the compression ratio is increased, the appearance of knocking combustion is shifted toward higher engine rpm, so that the maximum requirement of the engine for knock resistance of LPG should be determined at these higher engine speeds. 4. Selection of the compression ratio for gas engines must take into account the octane number of the LPG as determined by the motor and research methods, with subsequent selection of the operating characteristics of automatic spark advance devices by the procedure of GOST 10373-63. The use of LPG in universal engines reduces the engine power and antiknock indices.

New dyes for ethyl fluid and leaded gasolines

1. The use of the dye Oil-Soluble Yellow “K” does not harm the antiknock properties of ethyl fluid. 2. The addition of the new dyes Oil-Soluble Yellow “K” and Dark-Red “Zh” to aviation and automotive gasolines does not affect the antiknock, physicochemical, or service properties of the gasolines. 3. The new dyes have good solubility characteristics in gasolines.

The Effects of Operating Conditions of the Engine on Antiknock Properties of Gasolines (6)

The Effects of Operating Conditions of the Engine on Antiknock Properties of Gasolines (6)

The Effects of Operating Conditions of the Engine on Antiknock Properties of Gasolines (3)

Antiknock qualities of clear catalytically reformed naphtha and with tetraethyl lead (TEL) and tetramethyl lead (TML) were studied under various operating conditions of the CFR engine. The operating variables investigated were engine speeds of 600, 900 and 1, 200rpm, ignition timing of 5° to 35° BTDC, air-fuel ratio between 10 and 16, and inlet mixture temperatatures of 50° to 150°C. The lead response was evaluated from increase of incipient knock limited compression ratio.The effect of TEL or TML varied with engine operating conditions, but generally, lead response in catalytically reformed naphtha was greater at richer mixture and at retarded timing of ignition.Because the relative effectiveness of TML to TEL varied considerably, depending on operating conditions and lead concentrations, it was difficult to state absolutely which was more effective than the other. It was found that the relationship between the incipient knock limited compression ratio and lead concentration was expressed by the same type of empirical equation as found on octane number and lead concentration.

The Effects of Operating Conditions of the Engine on Antiknock Properties of Gasolines (5)

The effect of inlet-mixture temperature on antiknock qualities of some stock components of gasoline and 80 ON primary reference fuel, both clear and with antiknock compounds, were studied on the CFR engine.The engine was operated at inlet-mixture temperatures ranging from 40 to 150°C, engine speed of 900rpm, with the best power ignition timing except in the case of straight-run light naphtha, and with air-fuel ratios from 12 to 15.The leaded catalytically reformed naphtha and leaded 80 ON primary reference fuel showed peculiar knocking characteristics different from that of clear fuels. The results were analyzed using the calculated values of compression temperature and compression density, and it was found that tetraethyl lead was most effective in the compression temperature range from 680 to 700°K, which was in favor of the result obtained by B.R. Siegel.It was shown that the knock limited compression density ρ could be expressed with inlet-mixture temperature Ti by the equation; ρ=AeC/Ti. This relationship was explained by assuming that the ignition delay of the end gas would coincide with the time required for consuming the whole mixture by the travel of the normal flame front.

The Effects of Operating Conditions of the Engine on Antiknock Properties of Gasolines (4)

The Effects of Operating Conditions of the Engine on Antiknock Properties of Gasolines (4)

The Effects of Operating Conditions of the Engine on Antiknock Properties of Gasolines (2)

(1) The relationships between spark advance and power of the CFR engine under various conditions were studied. The maximum power spark advances at engine speed of 600rpm and 900rpm were compared with those specified for octane rating by Research and Motor method.(2) The comparison is made between the knock limited compression ratios by incipient knock and standard knock intensity of Research and Motor method. The possibility of estimating the Research octane number from the incipient knock limited compression ratio is deduced.(3) It is shown that spark advance and mixture ratio have more effects on antiknock properties as higher octane number fuels are used.