Test stand and experimental results using weak mixtures gasoline-hydrogen at SI engine.

Fodor, Dinu ; Mitran, Tudor ; Pater, Sorin 等

1. INTRODUCTION

The device on fig. 1 is working as a block diagram. The measuring device (see fig. 2), allowes some researches to be achieved in order to verify the possibility of raising the energetically and economical performances as well as the degree of reducing the polluting exhaust gases at a s.i. engine, by combusting weak mixtures with an addition of hydrogen produced on board of the car. (Furama 1979). The experimental researches also permitted to obtain data concerning the parameters of the duty cycle and those of the combustion process in the test engine, by verifying the possibility to improve the combustion kinetics of the lean mixtures with the proposed solution in the spark-ignition engines. (Matete, & Wolf 1972)

With that it has been studied the engine characteristic comparatively under standard condition and with lean mixtures and hydrogen addition under different operating conditions of the engine, respectively. (Bradford et al. 1984). The envisaged research program has been carried out by recording the following parameter required by the investigation: (xxx, 1979).

--parameters concerning the specific effective charcteristics of the engine;

--parameters concerning the specific indicated charcteristics of the engine;

--coefficient concerning the parameters of the combustion process;

--characteristics concerning the level of the emissions in the exhaust gases;

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2. TESTING BENCH

The tests have been performed on the engine in several stages. The first stage envisages the determination (9, 10, 11) of the engine effective and indicated parameters on the testing bench by means of a braking device endowed with suitable metering equipments as well as with an electronic recorder of the indicated diagram in the engine cylinder, in (p-[alpha]) coordinates, concomitantly with the cyclical dispersion both by direct plotting and by photography on the oscilloscope.

The data obtained on these devices enabled us to process the indicated diagram in p-V coordinates and to determine the parameters of the combustion process. (Lewis & ELBE 1961)

The correlation of the measured pressure depending on the rotation angle of the crankshaft as well as the opening of the inductive transducers type A.V.L. (Fig. 3) firmly mounted on the cylinder block, those transducers taking over the impulses from two coaxial disks mounted on the crankshaft.

The denticulate disk obtained through milling-work marking the angle has been made with a 20[degrees] division, and near the upper dead centre has been made symmetrically every 5[degrees] in order to accurately pursuit the detachment points. The inductive transducer (5) to indicate the point of ignition (Fig.2) was mounted on the cylinder high-tension lead (1) where the pressure transducer was mounted, too.

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The electrical signals obtained from the piezoelectric transducer (1) (Fig.4) are introduced in the load amplifier AVL-3059 (11) which is coupled to the calibration unit AVL-3054 (13). The two inductive transducers AVL (2) are coupled to the time base control unit AVL-4004 (12). The inductive transducer (5) to indicate the point of ignition, together with the two units (11-12) are connected to the Tektronix oscilloscope type 5113(8) that has several calibration positions dependent on the graduation of scale. This oscilloscope is provided with an obscure tube which allows for an EXATTA VAREX camera to be mounted on it, which has allowed the images to be recorded on the scale, dependent on the pressure and the angle of rotation of the crankshaft together with the point of releasing the electric spark, as well as for the cycle of dispersion to be photographed under ill the operating conditions (Fig.5).

In order to obtain more accurate measurements of the pressure change in the cylinder and to determine the parameters of the combustion process, the device has been completed with a NICOLET digital oscilloscope (9) which allows all the elements to be accurately plotted through graphic transposition by means of the X-Y Riken recorder (10). This also permits on the same scale for the pressure curve to be recorded without any combustion under the entire load and speed operating conditions.

The loggings of the indicated diagrams developed with several loads and speeds comparatively for the standard fuel-fed engine and the hydrogen addition fed engine have been made on the A4 sizes, and the pressure unique scale has been chosen 10 bars = 37,5 mm.

[FIGURE 5 OMITTED]

From these loggings one can notice that the pressure change has been maintained lineal dependent on the height of the logging.

In order to obtain the zero pressure line, the pressure of the outset of the compression has been approximated, the error being not bigger than 1%.

The accidental deviations could be rectified by estimating the mean pressure of the mechanical losses that presents a constant value when the engine speed and load are constant.

In this way for the three load operating conditions with the division of 500 rot/min there have been determined the most probable mean values of the medium pressure of the mechanical loss to which there have been compared all the other pressure diagrams under the respective operating condition of the engine.

Another stage has been the testing of the engine on the car at stabilized speeds on the track as well as in highway traffic. Soat the average speed of 72 km/h, on a 250 km distance, in street traffic it was obtained a fuel consumption of 5,3 l/100 km, at a loading of 50% from the maximum permitted load. The dynamic parameters have also been improved. Thus from 0-100 km/h we got to a 18,3" timing compared to the 22" obtained without our device.

The last testing was made on the roll stand in accordance with the norms 15 CEE as well as the polluting emissions standards.

3. CONCLUSION

By using gasoline-hydrogen mixtures on SI engines with carburetor allows (Fig.6) a substantial reduction of the fuel consumption with 10-15% and At speeds of 40-50 km/h allowed by the urban traffic norms one can see a reduction of the CO between 0,8-1,2%,

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As a result of the tests performed there arises the necessity for modifying the advance characteristics.

Better results can be obtained on engines with fuel injection systems.

Further reaserches for using fuel-hydrogen mixtures can be extended on diesel engines.

4. REFERENCES

Bradford, W.B.; FINCH, J.G. & PRlOR, Mc.A. (1984), The Ignition of Some Explosive Mixtures by Modified Oil Discharges. Journal of the Chemical Society

Furama, S. (1979). Two-Stroke Hydrogen Injection Engine, H.E.4, 6

Lewis, B. & ELBE, G.(1961) Combustion, Flames and Explosions of Gases. Academic Press

Matete, & Wolf (1972). Hydrogen and the Big Energy Options. H.E.4, 2

xxx, (1979). Hydrogen Update. In: Hydrogen Progress, nr.9,