IC ENGINES AND POWER PLANTS LAB

Lab Report No.07

(Drawing Engine Performance Curves at Full and
Partial Loads for Two Stroke Engine Dynamometer )

Submitted to: Lab Engineer Usman Ghani

Name CMS Section School Dated
ID

Muhammad 341482 ME- School of Mechanical 04/04/2024

Rizwan 12(A) and Manufacturing (DD/MM/YYYY)
Engineering(SMME)
Table of Contents
Objectives:.................................................................................................................2
Apparatus Used:........................................................................................................2
Theoretical Background:...........................................................................................3
Procedure:..................................................................................................................6
Observations:.............................................................................................................7
Observations:.............................................................................................................8
Conclusions:..............................................................................................................9
Recommendations:....................................................................................................9
Essential Safety Precautions:.....................................................................................9
Objectives:
 Familiarity with two stroke engine dynamometer
 Drawing performance relations
 Studying engineering parameters

Apparatus Used:
 Engine Test Bed
 Stopwatch
 Stationary items
 Excel

H2O Barometer Air Temperatures Load and Torque Oil and Fuel Load Cell
Meter Temp

Load Intensity Safety Switch On/Off Switch Load Controller Fuel Tank

Figure: Dynamometer Controller Two Stroke Engine

 Figure: Two Stroke Internal Combustion
Engine

Theoretical Background:
 Working of Two Stroke Engine:
A profound comprehension of engine functionality can be best elucidated through
the visualization of thermodynamic processes portrayed on a Pressure-Volume
(PV) Diagram. The cycle of a 2-stroke engine embarks with the piston positioned
at the Top Dead Center (TDC), descending towards the Bottom Dead Center
(BDC), thereby expanding the volume (from point A to point B). Simultaneously, a
fuel-air mixture fills the crankcase through an intake port. As the piston approaches
BDC, the intake port seals, prompting compression of the mixture (from point B to
point C). At point C, ignition occurs, triggering combustion and a swift surge in
pressure (from point C to point D). The intensified pressure propels the piston
downward (power stroke), followed promptly by the uncovering of exhaust ports,
permitting the discharge of combusted gases (from point D to a point E).
Immediately after exhaust or concurrently, a transfer port adjacent to the crankcase
opens, propelling the compressed fuel-air mixture into the cylinder, displacing any
lingering exhaust (scavenging). As the piston ascends, both exhaust and transfer
ports close, setting the stage for the cycle's reinitiation at point A. This depiction
simplifies the illustration of a 2-stroke engine's power generation through
combustion and pressure augmentation within a single crankshaft revolution.
  Engine Performance Curves:
Engine performance curves are graphical representations that provide critical
insights into the operational characteristics of an internal combustion engine across
its entire speed range. These curves depict how two key performance parameters,
power output and torque delivery, vary with respect to engine speed, typically
measured in revolutions per minute (RPM). Analyzing these curves is essential for
engineers to optimize engine design, predict performance under various operating
conditions, and ensure proper engine selection for specific applications.
Maximum Output Power Curve (Brake Horsepower Curve):
The maximum output power curve, also known as the brake horsepower (BHP)
curve, portrays the engine’s maximum achievable power output at different engine
speeds. The term “brake horsepower” signifies the actual power available at the
engine’s crankshaft after accounting for frictional losses and other internal power
losses. This curve essentially defines the engine’s power potential under ideal
operating conditions. It typically exhibits a peak value at a specific RPM, referred
to as the peak power RPM.
Significance of the BHP Curve:
Engine Selection: Understanding the BHP curve is crucial for selecting an
appropriate engine for a particular application. By comparing BHP curves of
different engines, engineers can determine which engine can deliver the desired
power output within the anticipated operating speed range. For example, a high-
performance sports car might require an engine with a BHP curve that prioritizes
peak power at higher RPMs, whereas a heavy-duty truck might benefit more from
an engine with a BHP curve emphasizing consistent power delivery across a
broader RPM range for efficient load hauling.
Performance Assessment: The BHP curve provides a valuable tool for evaluating
an engine's overall performance capabilities. By analyzing the shape of the curve,
engineers can assess factors like the engine's responsiveness to changes in throttle
input and its ability to maintain power output at sustained high RPMs.
Torque Curve:
The torque curve depicts the relationship between engine torque and RPM. Torque,
measured in Newton-meters (Nm) or pound-feet (lb-ft), represents the rotational
twisting force generated by the engine’s crankshaft. This force is directly
responsible for overcoming inertia and propelling the vehicle or driving machinery.
Similar to the BHP curve, the torque curve illustrates how torque varies across the
engine’s operating range.
Significance of the Torque Curve:
Importance for Specific Tasks: Torque is often a more critical parameter for tasks
that demand high pulling power, such as towing heavy loads or rapid acceleration.
A higher torque output at lower RPMs translates to greater engine lugging
capability, which is essential for overcoming initial resistance and maintaining
speed when hauling heavy loads.
Transmission Design and Fuel Efficiency: Analyzing the torque curve allows
engineers to design engine and transmission systems that deliver torque efficiently
at different RPMs. By ensuring optimal torque availability within the intended
operating range, engineers can contribute to improved fuel efficiency and overall
performance.
Engine Design Considerations: The shape of the torque curve is influenced by
various engine design factors, including combustion chamber design, intake and
exhaust system configurations, and valve timing strategies. Additionally, fuel types
(gasoline, diesel) and aspiration type (naturally aspirated, turbocharged) can
significantly impact the torque curve’s characteristics.
By comprehensively analyzing both the BHP and torque curves, engineers gain
valuable insights into an engine’s performance characteristics. This information is
crucial for optimizing engine design for specific applications, ensuring efficient
power delivery, maximizing fuel economy, and guaranteeing reliable operation
throughout the engine’s operational range.

Procedure:
The following procedure outlines the steps involved in conducting the engine
dynamometer test:
1. Dynamometer Initialization: Power on the dynamometer and record the
initial mass of fuel within the designated fuel system.
2. Engine Start-up and Stabilization: Following established safety protocols,
initiate engine operation and activate a timer to track the test duration.
3. Engine Speed Setting and Stabilization: Employ the dynamometer controls
to set the desired engine speed (rpm) for the test. Utilize the throttle to
achieve and maintain this specific speed until a stable operating condition is
reached.
4. Load Application and Excitation: While maintaining the targeted engine
speed, gradually increase the load on the dynamometer system to the desired
intensity. Subsequently, deactivate the emergency stop function and initiate
the test by pressing the “start excitation” button.
5. Data Acquisition and Calculation: The dynamometer will display the
relevant engine parameters during the test. Carefully record all displayed
values, including engine speed, torque, brake power, and any other pertinent
measurements. Utilize these recorded data points to calculate the desired
engine performance parameters for this specific operating condition.
6. Load Variation and Repetition: To establish trends in power and torque
characteristics, repeat steps 3 through 5 at varying load levels across the
intended operating range.
7. Data Analysis and Presentation: Compile the acquired data points for engine
speed (rpm), power output, and torque. Generate plots or graphs to visualize
the trends in power versus rpm and torque versus rpm, enabling visual
analysis of the engine’s performance characteristics.
Observations:
Engine : Two Stroke Petrol Engine
Fuel Type : Petrol + Mobile Oil
Partial Load :2
Full Load :4
Following is the table of readings:
Speed (RPM) Electric Power (kW) Engine Torque (N m)
Partial Load
1947 0.221 1.822
2051 0.233 1.807
2168 0.21 1.541
2231 0.218 1.554
2382 0.215 1.393
Full Load
1938 0.262 1.751
2099 0.278 1.742
2147 0.287 1.738
2345 0.291 1.708
2629 0.345 1.618

ENGINE PERFORMANCE CURVES (Partial

Loads)
0.235 2
0.23 1.8
1.6
0.225
1.4
0.22 1.2
0.215 1
0.21 0.8
0.6
0.205
0.4
0.2 0.2
0.195 0
1900 2000 2100 2200 2300 2400 2500

Power (kW) Torque (N m)

 ENGINE PARAMETER CURVES (Full Loads)
0.4 1.8

0.35
1.75
0.3

0.25 1.7
0.2

0.15 1.65

0.1
1.6
0.05

0 1.55
1900 2000 2100 2200 2300 2400 2500 2600 2700

Power (kW) Torque (N m)

Observations:
 Partial Load:
Trend: As engine speed (RPM) increased under partial load, a decrease in torque
was observed, while power output exhibited an increase. This trend aligns with
typical engine behavior.
Anomaly: During the experiment with varying RPM and partial load, instances of
engine misbehavior were encountered. These anomalies manifested as sudden
spikes in both electrical power and engine torque, resulting in a corresponding
peak in the power curve. It’s important to investigate these anomalies further to
understand the underlying cause, such as potential issues with fuel delivery,
ignition timing, or air intake.
 Full Load:
Trend: Under full load conditions, the experiment yielded an ideal curve,
showcasing the expected behavior. As engine speed increased, torque decreased,
and power output increased. This aligns with the theoretical understanding of
engine performance at full load.
Conclusions:
The experiment successfully demonstrates the relationship between load intensity
and engine performance parameters. The observed trends under full load align with
expected engine behavior. However, the anomalies encountered during partial load
operation warrant further investigation to ensure consistent and reliable engine
performance.

Recommendations:
To gain a more comprehensive understanding of the engine’s behavior under
partial load, it’s recommended to repeat the experiment at the regulator setting of 2
while implementing strategies to mitigate the observed anomalies. This might
involve analyzing and optimizing fuel delivery, ignition timing, or air intake
systems.
Analyzing additional engine parameters, such as fuel consumption and exhaust gas
emissions, could provide further insights into the engine’s performance and
efficiency under varying load conditions.

Essential Safety Precautions:

For the safe and successful operation of the engine dynamometer test, adhering to
the following safety precautions is paramount:
1. Engine Shutdown Before Refueling: Always ensure the engine is completely
stopped before initiating any refueling procedures. This eliminates the risk
of fire or explosion from accidental sparks or hot engine components coming
into contact with fuel.
2. Stable and Level Operating Surface: Operate the engine on a sturdy, level
platform free of debris such as small rocks or loose gravel. This minimizes
the potential for engine instability or tipping, which could lead to injuries or
equipment damage.
3. Fuel System Integrity Checks: Conduct a thorough inspection of all fuel
lines and connection points for signs of wear, looseness, or leaks. A
compromised fuel system can lead to fuel spills, fires, and inhalation
hazards. Address any identified issues before proceeding with the
experiment.
4. Engine Speed Limitations: Strictly adhere to the engine’s operational speed
range as specified in the manufacturer’s manual. In this case, the maximum
 permissible RPM is 4000. Exceeding this limit can cause excessive wear and
tear on engine components, potentially leading to breakdowns or safety
hazards.
5. Engine Oil Maintenance: Regularly check the engine oil level and top it up
as necessary using the recommended oil grade and viscosity. Proper
lubrication is critical for minimizing friction, heat generation, and wear on
engine components.
6. Fuel Level Monitoring and Refueling: Maintain adequate fuel levels in the
engine’s tank. Avoid overfilling, as this can lead to fuel spills and potential
fire hazards. Refuel only when the engine is cool and completely stopped.
7. Full Load Regulator Setting: During full load operation, ensure the
dynamometer load regulator is set to a maximum of 4. Exceeding this setting
can overload the engine, potentially causing damage or compromising its
safe operation.