From the results obtained it is inferred that the VCR engine has maximum performance and minimum emissions at 18 compression ratio, 5% fuel blend and at 9.03 kg of load.
Changes in brake power and torque with speed for the variable compression ratio at constant minimum bsfc are shown in Figure 7.
The method yields a stress tensor defined by three principal stress components, namely, maximum compression (σ1), intermediate compression (σ2), and minimum compression (σ3), with the stress magnitude ratio defined as R = (σ2 - σ1)/(σ3 - σ1).
The main conclusions of this study indicate that varying the compression ratio to achieve minimum bsfc or maximum brake torque for moderate diesel engine under the restriction that the maximum cylinder pressure and temperature do not exceed those of the conventional engine results in saving fuel consumption, higher brake efficiency and power, and reduction in soot emission from the engine.
The effect of the optimal variation of the compression ratio corresponding to the minimum bsfc on soot and NOx emissions is shown in Figure 9.
The method yields a stress tensor defined by the three principal stress components, namely maximum compression, (σ 1), intermediate compression, (σ 2), minimum compression, (σ 3), and the stress magnitude ratio defined as R = (σ 2 − σ 1)/(σ 3 − σ 1).
In addition, for the variable-compression-ratio engine, the bsfc is kept constant at its minimum value of 230 g/kW.h by varying the compression ratio between 16.4 and 17.8.
An optimization analysis is conducted for seeking an optimum variation of compression ratio to achieve pre-set objective targets such as constant minimum brake-specific fuel consumption and constant maximum torque.
The Volt requires premium gasoline with a minimum 91 or octane rating because the higher octane rating fuel permits the 10.5 1 compression ratio engine to utilize more ignition timing advance in order to maximize its fuel efficiency by 5 to 10% as compared to regular gasoline.
The efficiency of a gas engine is limited by (among other things) the compression ratio, the amount that the fuel-air mixture is compressed by the cylinder: the more compression the more efficient the engine.
