Engine Performance Lab Report

Summary

The test engine used in this laboratory is a single-cylinder four-stroke engine attached to an AC dynamometer. This engine, manufactured by AVL GmbH in Austria, has typical passenger car engine dimensions. In this lab report, we will analyze the data and calculations obtained from the engine test to gain a better understanding of its performance.

Various test parameters were investigated during the lab, including baseline, high load, high speed, early ignition, late ignition, rich mixture, and lean mixture. To assess the engine's performance, we examined variables such as engine speed, lambda (air-fuel ratio), AFR (Air Fuel Ratio), Indicated Mean Effective Pressure (IMEP), Indicated Specific Fuel Consumption (ISFC), exhaust temperature, ignition changes, and engine emissions.

By comparing these variables to the baseline of the experiment, we can analyze the results and understand how different parameters affect the engine's efficiency and performance. The collected data and calculations will be included in the appendix of this report.

Formulas

Several formulas are crucial for understanding the engine's performance:

1. Indicated Power (ip): Indicated power is the power developed within the cylinder and can be calculated using the formula:

   ip = Pmi * A * L * n

   Where:

   • Pmi = Mean Effective Pressure (N/m^2)
   • A = Piston Area (m^2)
   • L = Stroke Length (m)
   • n = Number of Power Strokes per Second
2. Air Fuel Ratio (AFR): AFR represents the ratio of air to fuel consumed and is calculated by dividing the mass of air by the mass of fuel used.
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3. Mass Flow Rate: Mass flow rate is essential for fuel injection calibration and helps determine the timing of injection events, ensuring efficient combustion.
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4. Volumetric Efficiency: Volumetric efficiency measures the ratio of actual cylinder volume to ideal mass of air during the intake process, indicating how effectively the engine breathes.
5. Indicated Specific Fuel Consumption (ISFC): ISFC measures the fuel consumption in terms of mass flow rate per unit time and evaluates the efficiency of fuel supply for engine operation.
6. Indicated Thermal Efficiency: This ratio compares the indicated power to the power produced by burning fuel in the chamber, considering fuel supplied and its calorific value.
7. Coefficient of Variation (COV): COV measures the duration taken for pressure to increase noticeably in an internal combustion engine.

Discussion & Results

Comparison of High Load and High Speed to Baseline Parameters

When comparing the results of high load and high speed to the baseline parameters, we observe the following:

When comparing these results, it is evident that high load conditions result in higher indicated power due to increased fuel consumption. This increased fuel consumption leads to higher in-cylinder pressure, as shown in the PV diagram for high load. High-speed conditions also exhibit higher indicated power, possibly due to more efficient combustion resulting from higher indicated power.

Furthermore, engine emissions vary between high load and high-speed conditions, with high load conditions producing higher levels of NOx, THC, and CO due to increased fuel consumption. High-speed conditions, on the other hand, result in lower emissions. Exhaust temperature also varies significantly, with high-speed conditions leading to higher temperatures.

These comparisons provide valuable insights into how different operating parameters affect engine performance.

Comparison of Early Ignition and Late Ignition to Baseline Parameters

When comparing the results of early ignition and late ignition to baseline parameters, we observe the following:

Comparing early ignition and late ignition to baseline parameters, we find that ignition timing significantly affects indicated power, ignition changes, and ISFC. Early ignition results in lower indicated power, higher ignition changes, and slightly higher ISFC. Late ignition, on the other hand, shows similar trends with lower indicated power and ignition changes but higher ISFC.

Engine emissions also exhibit significant differences between baseline, early ignition, and late ignition conditions. Early ignition results in higher NOx emissions, while late ignition has lower NOx emissions compared to baseline.

Comparison of Rich Mixture and Lean Mixture to Baseline Parameters

When comparing rich mixture and lean mixture to baseline parameters, we observe the following:

Comparing rich mixture and lean mixture to baseline parameters, we find significant differences in lambda values, indicated power, indicated thermal efficiency, AFR, and engine emissions. Rich mixture conditions exhibit lower lambda values, resulting in decreased indicated power and thermal efficiency but higher emissions of CO2, NOx, and lower O2 levels. In contrast, lean mixture conditions show higher lambda values, increased indicated power and thermal efficiency, but higher emissions of NOx and CO2 and lower O2 levels.

These comparisons highlight the impact of fuel-air mixture on engine performance and emissions. Striking a balance between rich and lean conditions is essential for optimizing engine performance while meeting environmental regulations.

Conclusion

This comprehensive engine performance lab report has examined various test parameters and their effects on engine performance, emissions, and efficiency. It is clear from the analysis that different operating conditions significantly impact the engine's behavior.

High load and high-speed conditions result in higher indicated power but also lead to increased emissions. Early ignition and late ignition have distinct effects on performance and emissions, with early ignition causing higher NOx emissions. Rich mixture conditions reduce power and increase emissions, while lean mixture conditions improve power but also lead to higher emissions.

Optimizing engine performance while minimizing emissions remains a challenge for the automotive industry. Further research and development are necessary to strike a balance between performance and environmental considerations.