How does timing affect emissions

On the other hand, it produces less power. To increase the brake power, solution is to use a direct injection with suitable compression ratio to avoid knocking phenomenon. The CNG air fuel ratio is There occurred an ideal fuel injection timing where the maximum cylinder pressure and the maximum rate of heat release obtained their maximum values along with the shortest combustion durations, the shortest heat release duration closing to the top dead center but keeping the low level of HC and CO emissions [ 3 ].

The injection timing is a very important parameter to ensure better combustion, and this depends on valve timing and ignition timing; those are main factors to optimize the heat release which has effects on the performance of the engine [ 4 ].

To obtain the optimum injection timing this engine was tested with different injection timings. In another experiment using a single-cylinder diesel engine fueled by natural-gas, the test results with advanced injection timing showed that each alternative fuel requires injection advanced appropriately to its delay period. It was found that advanced timing tended to incur a minor increase in fuel consumption. There was an important reduction in CO 2 emissions with advanced timing [ 7 ].

By using rapid compression machine the effect of injection timing was tested on natural-gas direct injection. Results have shown that early injection leads to longer duration of the initial combustion.

However, late injection leads to a longer duration of the late combustion. Early injection showed lower CO concentration in the combustion products while late injection gave lower NO x [ 8 ].

In another study using a single cylinder, with compression ratio of 14, natural-gas direct injection was tested. Furthermore, in another study using natural-gas direction injection with late injection timing and lean combustion, results showed indicated mean effective pressure IMEP decrease with the lambda increase [ 10 ].

Additionally, another study used lean combustion stratified direct injection gasoline fueled single cylinder; results showed smoke emission, and incomplete combustion products were increased at the late injection timing due to increased close by rich area of the mixture. On the other side, nitrogen oxides NO x emissions were reduced while indicated mean effective pressure IMEP was increased as the injection timing was retarded [ 11 ].

The results showed that the engine performance e. The empirical part using four-cylinder natural-gas direct injection combustion is tested with a kind of piston crown that could generate homogenous mixture during compression stroke. The objective of this investigation is to study the optimum injection timing by using different points to obtain a higher engine performance with lower emissions.

For ignition timing, it was fixed for all tests. The engine specifications are given in Table 1. CNG was used as fuel. The substantial advantage that CNG has in antiknock quality is related to the higher auto ignition temperature and higher octane number compared to that of gasoline as shown in Table 2. Furthermore, CNG has a high air fuel ratio and heating value with Results were recorded in steady-state condition so ambient pressure, ambient temperature, and humidity were recorded to estimate air inlet density.

The engine was running under full load wide-open throttle. The homogenous piston crown used is shown in Figure 2. The increase of power was due to many reasons which include high pressure and high-heat release. We are excited to announce that FibromyalgiaTreating.

All of the same great people, writers and editors but now with more firepower. We now have access to an enormous amount of additional research information from doctors and scientists. We can now extend to other conditions that may be part of your everyday lives and help you on a broad level if that is what you need.

We are here for you and now, better than ever so sit back and enjoy the new Fibromyalgia Treating by RedOrbit! Comments comments. JavaScript is disabled for your browser. Some features of this site may not work without it. Toggle navigation. Impact of retarded spark timing on engine combustion, hydrocarbon emissions, and fast catalyst light-off Author s Hallgren, Brian E.

Brian Eric , Download Full printable version Best performance will be achieved when the greatest portion of the combustion takes place near top dead center. If the ignition timing is not advanced enough, the piston will already be moving down when much of the combustion takes place. In this case we lose the ability to expand this portion of the gas through the full range, decreasing performance. If the ignition timing is too advanced, too much of the gas will burn while the piston is still rising.

The work that must be done to compress this gas will decrease the net work produced. These competing effects cause there to be a maximum in the IMEP as a function of ignition timing advance. As is evident in Fig. Maximum pressure would be reached if all of gas were burned by the time the piston reached TDC.

The relationship between exhaust temperature and In cylinder peak pressure versus ignition timing-wide open throttle; equivalence ration of one. IMEP represents the work done on the piston. The exhaust gas temperature represents the enthalpy of the exhaust gas for ideal gases.

The enthalpy is a function of temperature only and energy released by combustion of fuel must go into expansion work. The temperatures of the exhaust gas also decrease if energy is to be conserved Fig. The relationship between BMEP and ignition timing. Engine speed of RPM, intake manifold pressure of kPa. The results show that BMEP increased with ignition timing advance. This expected that BMEP decrease with closing ignition time to top dead center.

If the ignition is not advanced enough, the piston will already be moving down when much of the combustion take place. In this case we lose the ability to expend this portion of the gas and decreasing performance. If the ignition is too advance, much portion of gas will burn while the piston is still rising; the work that must be done to compress this gas will decrease the net work produced.

Figure 6 shows O 2 and HC concentration as a function of timing angle. Advance timing angle causes higher in cylinder peak pressure. This higher pressure pushes more of the fuel- air mixture into crevices most significantly the space between the piston crown and cylinder walls where the flame is quenched and mixture is left unburned. Additionally, the temperature late in the cycle, when the mixture comes out of these crevices, is lower at more advance ignition timing.

The later temperature means that the hydrocarbons and oxygen do not react. This increase the concentration of oxygen in the exhaust and unburned hydrocarbons. The relationship between O 2 , CO and HC concentration versus ignition timing intake manifold pressure of kPa and equivalence ratio of unity.

In above figure carbon monoxide, oxygen and carbon dioxide concentration change very little with ignition timing in the range studied Fig. In here, the equivalence ratio was held constant and at ratio of unity, so there was enough oxygen to react most of carbon to CO 2. Some carbon monoxide does appear in the exhaust due to frozen equilibrium concentration of CO, O 2 and CO 2.

The relationship between NO concentrations versus ignition timing. Engine speed at RPM and intake manifold pressure of kPa. Figure shows NO concentration in the exhaust gas versus ignition timing. NO formation is function of temperature. With advancing the ignition timing, the in- cylinder peak pressure increase.

The ideal gas law tells that increase in peak pressure must correspond to an increase in peak temperature, and higher temperature causes the NO concentration to be higher Fig. It is expected that power should increase with spark advance to a point, and then drop off. Best performance will be achieved when the greatest portion of the combustion takes place near top dead centre.

If the spark is not advanced enough, the piston will already be moving down when much of the combustion takes place. In this case, we lose the ability to expand this portion of the gas through the full range, decreasing performance.

If ignition is too advanced, too much of the gas will burn while the piston is still rising. As a result, the work that must be done to compress this gas will decrease the net work produced. These competing effects cause there to be a maximum in the power as a function of spark advance.