Experimental investigation on impact of fuel jet size on performance of gasoline-ethanol blend in a SI engine vehicle

Carbon monoxide (CO) emission

CO which is lighter than air is a colourless, odourless, and tasteless gas. CO is dangerous to animals and human beings if exposed to this gas in higher concentrations. Petroleum fuels with no oxygen in their molecular structure produce CO due to an incomplete combustion process.

The engine rpm is measured by using a tachometer and the % of CO versus engine speed graph is shown in Fig. 2. From Fig. 2, it is shown that gasoline CO emission is higher at lower engine speeds. At 1000 rpm CO emission is 4.4%. At lower engine speed the air-fuel mixture becomes rich. That means the amount of oxygen in the air-fuel mixture is less, so there is not enough oxygen for full combustion and conversion to CO₂. At 1500 rpm the CO emission slightly drops to 3.6%. It shows that at 1500 rpm there is good charge mixing and better combustion which is why the CO emission becomes reduced at this engine speed.

As engine speed increases to about 2000 rpm and above the CO emission becomes increased to a higher percentage as the curve in Fig. 2 shows. This is because as engine rpm increases with full load acceleration under a wide-open throttle valve the carburettor acceleration and power system starts supplying additional fuel to the incoming air this causes the mixture to become richer and the amount of oxygen becomes lower than the fuel supplied by the system. Therefore, as engine speed increases there is not enough oxygen to convert all carbon to CO₂ and because of this, the CO emission becomes increases. In another case as engine speed increases, the duration for intake valve opening becomes decreases which means the intake valve closes before enough oxygen enter the cylinder; hence, there is not enough oxygen to convert all carbon to CO₂. So the amount of CO emission gets increased.

At lower engine speed as in Fig. 2, the curve shows CO emission is high. The CO emission is 2.1%at 1000 rpm and slightly decreases to 1.6% at around 1500 rpm (for larger size jet).When engine speed increases, the CO emission is slightly increased to 2.8% at about 3000 rpm. This is because as engine speed increases as it is tried to explain for gasoline CO emission under higher engine speed, with full load acceleration under wide-open throttle valve the carburettor acceleration and power system starts supplying additional fuel to the incoming air this causes the mixture to become richer and the amount of oxygen becomes lower than the fuel supplied by the system. So even if ethanol is an oxygenated fuel, as engine speed increases there is not enough oxygen to convert all carbon to CO₂, and because of this the E30 CO emission becomes increases slightly.

Even if CO emission is considered in both when the engine is running with gasoline and E30 (70% gasoline and 30% ethanol) as shown in Fig. 2, there is a higher difference in the CO emission. The E30, CO emission is much lower when compared to the amount of CO when the engine runs with pure gasoline fuel at each engine speed. This is because ethanol fuels an oxygenated fuel; it contains oxygen in its molecular structure. Since E30 contains 30% ethanol, it causes the combustion complete as much as possible.

Brake torque (Tb) and brake power (Pb)

The resistance offered to the Engine by the pole/Fly wheel against turn or measure of constrain required to stop a pivoting shaft/fly of range “r’ is named as Brake Torque additionally assigned as Load the units typically utilized for Brake Torque or Load are Nm. We require a measure of Force “N” Newton’s to pivot the pole, Pulley or Fly wheel of Radius “m”. The term Brake shows the estimation technique for Torque utilizing Brake framework. The Brake Torque increments with speed up to a most extreme esteem named as Max Brake Torque then it gets lower as at higher speeds as it gets to be distinctly troublesome for Engine to consume a full Charge of air.

Brake power: – The measure of mechanical work “w” in time “t” accessible at the yield shaft of Diesel Engine is called Brake Power. Ordinarily Given as kW different units is Horse power and kilo Watt hours. Brake Power relies on upon Brake torque and Engine Speed (rpm). Brake is lower at lower speeds where as it gets on higher at speed increments. It gets bring down after the temperate range at rapid of 6000 rpm where the torque diminishes significantly due lesser admission of air/fuel blend.

Engine dynamometers and rolling road or chassis dynamometers are the two varieties of dynamometers. For this project, a Sun Road-a matic-XII chassis dynamometer was utilized. Both the power production and the tractive effort given to the drive wheels can be measured by it. If the drive train gear ratios and transmission losses are known, the power available at the engine crankshaft, also known as brake power, can be computed.

Tractive effort is the force available between there are wheel tyres and the road. It is also tested by a chassis dynamometer. The tractive effort obtained from the chassis dynamometer test for both standard gasoline and ethanol-gasoline blend is presented in Table 4.

When running on gasoline the maximum Pb is 13.5 kW at 3300 rpm. A maximum Pb of 16 kW is obtained at 3600 rpm when running on E30 (with larger size main metering jet) and12.5Kw at 4800 rpm is obtained when running on E30 with smaller main metering jet. At lower engine speed the friction power is relatively low and hence the brake power increases with speed. As engine speed increases, the friction power at continuously greater rate and Therefore Pb reaches a peak and starts reducing. The reason for the decreasing of brake power at higher engine speed is less complete filling of the cylinder^23,24.

Brake specific fuel consumption (BSFC)

Brake specific fuel consumption (BSFC), which measures the amount of gasoline used per unit of braking power produced, is an essential metric for evaluating the efficiency of diesel engines. Due to its direct correlation with fuel efficiency, this component is essential to diesel engine design. Given the current energy management concerns, fuel economy is essential for enhancing engine performance and sustainability. Lower BSFC values indicate greater engine efficiency, which measures how well an engine transforms fuel into useable power. Whereas BSFC explicitly indicates the fuel consumption per unit of braking power, specific fuel consumption is the measurement of fuel utilized over a given period. Manufacturers can increase the overall efficiency of diesel engines and help with energy management and environmental impact reduction by concentrating on lowering BSFC. To create diesel engines that are more inexpensive and efficient, it is essential to comprehend and optimize BSFC²⁵.

Brake torque (Tb)

Brake Torque (Tb) is the torque available at the Flywheel‘. After wheel torque at the wheel is known the brake torque. For torque at the tire surface transmission efficiency is 0.9 at the top gear and 0.8 at other gears can be assumed. The test vehicle uses manual gear box type K40. It is a 4 speed transmission. While gasoline achieves 57 Nm at about 1550 rpm, the maximum engine brake torque for E30 fuel is 57.5 Nm at 1750 rpm. Figures 3 and 4 show that the efficiency decreases as heat dissipation affects performance, highlighting the relationship between engine speed, torque output, and thermal management. Brake torque is lower at lower engine speeds due to increased heat loss, which occurs because more heat is rejected to the engine coolant at lower speeds, resulting in a longer duration for heat conduction to engine components.

Additionally, at lower engine speeds, the engine rejects a large amount of heat to the coolant, which lowers the amount of heat that can be used for work. As a result, the brake torque output is reduced. A more efficient combustion process causes the brake torque to increase initially as engine speed increases, but it subsequently decreases at higher speeds. As the amount of heat rejected to the coolant diminishes, the braking torque increases at moderate speeds. As engine speed increases, more heat can stay in the engine for work since there is less time for heat to condense to the coolant. At extremely high speeds, however, other elements like friction and pumping losses may cause the torque to decrease. In order to maximize performance and efficiency under a variety of operating conditions, this connection emphasizes how crucial it is to balance engine speed and temperature control.

There are a number of reasons why brake torque decreases with increasing engine speed. First, the intake valve is open for a much shorter period of time at higher speeds. This causes incomplete combustion and a subsequent decrease in brake torque because the intake valve closes before the cylinder is completely filled with the air-fuel mixture. Additionally, the exhaust valve opens earlier in the cycle as engine speed rises. More heat is lost as a result of this early opening since more heat can escape with the exhaust fumes. At faster speeds, braking torque decreases due to a combination of a shorter air-fuel intake time and a greater amount of heat loss through the exhaust. The significance of improving valve timing and heat management to improve engine performance under a range of operating circumstances is underscored by these dynamics. Enhancing engine production and efficiency requires an understanding of these relationships.

The E30 brake torque (for smaller and larger main jet).

The E30 Brake power for gasoline.

The E30 Brake power (for smaller and larger main jet).

Gasoline brake specific fuel consumption.

The E30 brake specific fuel consumption (for smaller and larger main jet).

Gasoline brake thermal efficiency.

E30 brake thermal efficiency (for smaller and larger main jet).

Figure 5 shows that when running on gasoline the maximum brake power is 13.5 kW at 3300 rpm. Figure 6 reveals maximum brake power of 16 kW is obtained at 3600 rpm when running on E30 (with larger size main metering jet) and 12.5 kW at 4800 rpm is obtained when running on E30 with smaller main metering jet. The braking power increases with speed because the friction power is comparatively low at lower engine speeds. Pb hits a high and begins to decrease as engine speed rises because friction power grows steadily. The ratio of the engine’s fuel consumption in grams per hour (gm/hr) to its brake power in kW is known as brake specific fuel consumption. For calculating the amount of ethanol gasoline blend (E30), the amount of time it took to consume 10 g of E30 was recorded. By dividing 10 g by the amount of time needed to consume the ethanol fuel, one can determine the mass flow per unit time. At lower engine speed as Figs. 7 and 8 shows, the brake specific fuel consumption is relatively high. This is because at lower engine speed fuel is intentionally made rich. Hence there is not complete combustion and unburned fuel exits with the exhaust gas.

Brake specific fuel consumption of both gasoline and gasoline-ethanol blend E30 are decreasing as engine speed Therefore we conclude that brake specific fuel consumption rate is higher at low speed increases a little for medium speeds and increases more at high speeds. This is because at low and high speeds a rich mixture is required. Increases to some extent, and then increasing at high speed, In Figs. 7 and 8 the minimum fuel consumption for gasoline is 324gm/kWh at 2800 rpm and for E30 (with larger main jet) is 576gm/kWh at 2800 rpm and the minimum brake specific fuel consumption ofE30 with small size jet is 500gm/kWhr at 3000 rpm. At higher engine speeds the consumption rises, because the frictional loses of the engine rapidly and so the energy of combustion is again Bing wasted. There as on that bsfc is lowest at middle rpm, because the engine stand to develop best cylinder filling at middle speed, the engine‘s breathings at highest efficiency at these speeds.

The time it took to consume 10 g of fuel was recorded in order to measure gasoline consumption. By dividing 10 g by the amount of time needed to consume it, one can determine the mass flow rate of gasoline consumed per unit of time. The time it took to eat 10 g of the ethanol-gasoline blend (E30) was recorded in order to measure its consumption. By dividing 10 g by the amount of time needed to consume it, one can determine the mass flow rate of ethanol-gasoline consumed. E30 bsfc (for smaller and larger main jet) at lower engine speed, the bsfc is relatively high. This is because at lower engine speed fuel is intentionally made rich. Hence there is no complete combustion and unburned fuel exits with the exhaust gas. Bsfc of both gasoline and gasoline-ethanol blend E30 are decreasing as engine speed increases to some extent, and then increases at high speed.

Brake thermal efficiency

Brake thermal efficiency shows how efficiently fuel is used in the engine. The lower calorific value of both E30 and gasoline fuel is taken from the literature, 42.5 MJ/kg for gasoline and 41.47 MJ/kg for E30. The brake thermal efficiency of gasoline and E30 are given the maximum brake thermal efficiency for small size jet before modification, the maximum brake thermal efficiency is16% at 3800 rpm and the minimum thermal efficiency is 11% at 5600 rpm (Fig. 9). When the engine run son gasoline is 27% at 3200 rpm and the minimum brake thermal efficiency is 14% at 5600 rpm (Fig. 10). The maximum brake thermal efficiency, when the engine runs onE30 (after modification) is 18% at 3600 rpm and the minimum brake thermal efficiency is 10% at 5600 rpm. It is that at lower speeds the brake thermal efficiency is low because of thermal loss. At lower engine speed, there is sufficient time for the heat to dissipate to engine parts. This causes the brake thermal efficiency to decrease at lower engine speed. The brake thermal efficiency is also decreasing at maximum engine speed this is because; at maximum engine speed the exhaust valve opens and closes rapidly, this causes thermal loss. Hence brake thermal efficiency is reduced at higher engine speed. The maximum brake thermal efficiency, when the engine runs on gasoline is 27% at 3200 rpm and the minimum brake thermal efficiencyis14%at 5600 rpm. For small size jet before modification the maximum brake thermal efficiency is 16% at 3800 rpm and the minimum thermal efficiency is 11% at 5600 rpm. The maximum brake thermal efficiency, when engine runs on E30 (after modification) is18% at 3600 rpm.

Minimum brake thermal efficiency is 10% at 5600 rpm. From Figs. 9 and 10 it is shown that at lower speeds the brake thermal efficiency is low because of thermal loss. At lower engine speed the longer hot air spends in the cylinder, the more time it has to heat the engine parts. This causes the brake thermal efficiency to decrease at lower engine speed. The brake thermal efficiency is also decreasing at maximum engine speed this is because at maximum engine speed the exhaust valve open and close rapidly, this causes thermal loss. Hence brake thermal efficiency reduced at higher engine speed.

The E30 performance with smaller main jet.

E30 Performance with the larger main jet.

CO Emission Vs Engine speed.

Gasoline brake torque vs. Engine speed (RPM).

Brake Torque (Nm) vs. Engine speed(RPM).

Brake power(kW) vs. Engine Speed(RPM).

Brake Power(kW) vs. Engine speed(RPM).

The BSFC(g/kW h) vs. Engine Speed(RPM).

The BSFC(g/kWh) vs. Engine speed(RPM).

Brake Thermal Efficiency vs. RPM (Gasoline).

Brake Thermal Efficiency (%) vs. Engine speed (RPM).

Figures 14, 15, 16, 17, 18, 19, 20, 21 and 22 present a comprehensive comparison of engine performance metrics across gasoline and E30 fuel blends (with both small and large main jets), each plotted against engine speed (RPM) and accompanied by error bars to represent experimental uncertainty: Fig. 14 shows CO emissions with ± 0.2% uncertainty; Figs. 15 and 16 compare brake torque (± 1.5 Nm) for gasoline and E30 blends; Figs. 17 and 18 display brake power (± 0.5 kW); Figs. 19 and 20 illustrate brake-specific fuel consumption (± 15 g/kWh); and Figs. 21 and 22 depict brake thermal efficiency (± 1%), highlighting measurement precision across all conditions.