While performing the calculations for exhaust heat content at IC engine outlet, I used engine speed as the main parameter to estimate exhaust temperature. Do I need to incorporate engine load as well? If yes, please provide a research reference that comments on the relationship between these parameters.
Engine load is the parameter, if you keep increasing then the thermal efficiency will be increased, same time the combustion will be the batter in case of higher load. Then ultimately the exhaust temperature will increase. Again you may go for to control the exhaust temperature for adding some additives in fuels and other relevant techniques.
You can of course keep loading an engine at a fixed speed by simply burning more fuel through increasing the injection duration to balance the load at the same speed . In this case the exhaust temperature will definitely increase due to the release of more energy from the fuel. Any standard book on I C Engines will show you how to perform engine testing.
The influence is very small since the combustion is complete without issue only the time is changing. Exhaust parts mean to noise and emission more.
I did some research on intake and exhaust system, checkout my results from articles you can find good answers.
Regards
The increase in engine load results in more fuel combustion and increased torque and power. More exhaust gases will be produced and with complete combustion at all time the combustion temperature and exhaust gas temperature should remain the same. However, since more of the exhaust gas is produced, it's temperature will remain uniform and higher than for a low load engine because of greater mass.
The criteria is Energy per time in Jules/sec. More energy = higher temperature.
Rpm is the reverse. Higher speed equal higher exhaust volume at same volumetric efficiency. More volume at same energy = lower temperature.
Dear Saif Memon,
Exhaust temperature is effective at the temperature that is able to function at its highest efficiency. However, the exhaust gases themselves may be at a temperature anywhere between 400 to 900 degrees Celsius for SI engines and 200 to 500 degrees Celsius for CI engines. Temperature of engine exhaust is generally between 300 to 500 degrees. The exhaust pipe muffler temperature is usually between 300 to 500 degrees, but they are also known to handle higher temperatures of up to 1200 degrees. Extreme exhaust temperatures can destroy the catalytic converter.
At rich air-fuel ratio, the exhaust gas temperature either increases or decreases depending on the fuel. High temperatures (typically above 1,600 °F or 900 °C) can be an indicator of dangerous conditions that can lead to catastrophic engine failure. Most emissions are increased by increasing the exhaust temperature, but hydrocarbons (HCs) on an average decreased by 30% on increasing the exhaust temperature. it is seen that air-fuel ratio, exhaust temperature, effective power and brake thermal efficiency decreased and brake specific fuel consumption (BSFC) increased with isobutanol addition to conventional diesel fuel. At fixed engine speed and load, exhaust gas recirculation rates can be adjusted to keep NOx emission at 2.0 g/kWh.
Ashish
Saif Memon : Increase in Engine load, increases the fuel consumption thus leading to higher in-cylinder temperature. Which will eventually have a impact on the EGT.
But it depends whether you need to include engine load in your calculations or not. Like if you measuring EGT with changes in the engine speed and at a constant engine load, then you might not want to include it in your calculations.
@Olumide: I am wondering how more exhaust gases will be produced with the increase in engine load !!!! Could you tell me how??
When an an ic engine is placed under load depending on its design configuration some paranters maybe advanced like ignition timing, injection timing, air and fuel may be increased and if fitted with a compressor, manifold pressures will increase. All the aforementioned will result in increased heat, and in increased work. Friction will also be increased. Therefore it is safe to infere that the exhaust temperature will increase, additionally this is in fact desirable due to after treatment elements.
The rate of this increase will depend on throttle position (which is infinitely variable), load (which is infinity variable. Engine design and size etc,. altitude, ambient temperature and humidity and fuel type etc.
Ultimately and obviously if kept under load there will be a terminal heat achieved.
On the engine map, the engine can operate at the same speed under different loads according to the map region (full engine load, high, intermediate and low). This influences the temperature of the combustion chamber and consequently the exhaust emissions.
Both parameters have impact over the exhaust heat. When the engine speed rises the time for heat transfer from in-cylinder gases to the cooling system reduces and by this way the exhaust gases temperature is higher. When the engine load rises the temperature in the cylinder raises because of the higher amount of fuel which burn. So at highest engine speed and highest engine load the exhaust gases temperature is highest.
I would suggest you to see the following book:
Heywood. Internal Combustion Engines Fundamentals.
when the load on the engine is low, the fuel consumption is also low, that is low heat energy is generated and the exhaust is also noticed to be lower. When the load on the engine increases, the engine needs more fuel to generate more power in order to carry the load. When higher fuel is supplied to the engine results in rapid combustion results in release of higher exhaust temperature. Finally, when the load on the engine increases, the exhaust temperature also increases from the engine.
As mentioned in previous answers, based on the speed-torque map of the engine, adding more load might lead to an increase in engine speed. However, if engine speed is kept constant via a speed governor controller, then increase in load will lead to increased fuel consumption which will lead to an increase in exhaust port temperatures. The change in temperature can be estimated through the energy equations, however, I would also recommend factoring in the fuel quality. A change in fuel quality (different MN value) will cause different rates of increase in exhaust port temperatures. Finally, the combustion recipe will decide if you're burning too rich or too lean, which will also affect the EGTs.
Hope this helps.
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