Calculation of an engine power

In summary, the conversation discusses the calculation of power losses for a prototype car and whether an engine of 1.3 hp can be used in the car. The power losses were calculated for road gradient, rolling resistance, and drag, and a net power loss of 1.234 hp was determined. The use of a generator to charge the battery was also mentioned. The conversation also discusses the importance of considering factors such as safety, acceleration, friction, and conversion losses in the power calculation. Finally, the procedure for calculating power losses through transmission is explained, which involves assuming an efficiency for each gear or belt drive set.
  • #1
Carvinos
7
0
Hello!
Actually i want to find the required power of an a single cylinder air cooled 4 stroke OHV engine. i have calculated three power losses, power loss against road gradient (Pg), rolling resistance (Pr) and drag (Pd) using the following formulae:
Pg=M*g*v*grad=1.095 hp
M(mass of the prototype car)=120kg, g=9.8 m/s^2, v(prototype car velocity)=13.88 m/s, road gradient= 5% (0.05)
Pr=RRC*M*g*v=0.109 hp
RRC (rolling resistance coefficient)=0.005 for a bicycle tire we are using in our prototype car
Pd=0.5*rho*v^3*Cd*A = 0.030 hp
rho=1.099 kg/m^3, Cd (Coefficient of drag)=0.04 in case of our prototype car, A=0.384 m^2
Net power losses=Pg+Pr+Pd=1.234 hp.
Now please tell me can i use an engine of 1.3 hp of 35cc volumetric capacity in our prototype three wheeled car. Generator is the only accessory that will be connected with the engine to charge the battery.13.88 m/s will be the max. speed of our prototype car, 120 kg is the mass of the prototype with driver. reply soon please
 
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  • #2
Did you calculate the rolling resistance for all wheels?
Have you applied a safety factor, and an allowance for acceleration (and not just travel at a constant speed)?
Have you considered friction in your drivetrain?
Have you considered conversion losses through the powertrain (including your 'generator'?)
Is your engine going to be operating at optimum conditions for 1.3hp?
 
  • #3
ok.thnx.tell me please the procedure of how to calculate the power losses of engine through transmission.
 
  • #4
Carvinos said:
ok.thnx.tell me please the procedure of how to calculate the power losses of engine through transmission.

For every gear set or belt drive set, assume 95% efficiency. For every chain drive set, assume 92% efficiency. Multiply all of them for overall efficiency.

Ex.:

if the power of your engine goes through 3 gear sets before reaching the wheels, your overall efficiency would be 0.95*0.95*0.95 = 0.857. So if you need 1.234 hp at the wheel, you need 1.234 / 0.857 = 1.44 hp at the engine.
 

Related to Calculation of an engine power

1. How is engine power calculated?

Engine power is typically calculated by multiplying the engine's torque and rotational speed. This is typically measured using a dynamometer, which allows for accurate measurements of both torque and rotational speed.

2. What factors affect engine power?

There are several factors that can affect engine power, including the size and design of the engine, the quality of fuel and air intake, and the efficiency of the engine's combustion process. Other factors such as friction, temperature, and altitude can also have an impact on engine power.

3. Can engine power be increased?

Yes, engine power can be increased through various methods such as adding forced induction (turbo or supercharger), tuning the engine's fuel and air mixture, and upgrading engine components such as the exhaust system and intake manifold. However, it is important to note that increasing engine power can also put additional stress on the engine and may require additional maintenance.

4. How is engine power measured and what unit is used?

Engine power is typically measured in horsepower (hp) or kilowatts (kW). These units are used to measure the amount of work an engine can do in a given amount of time. In the United States, horsepower is the most commonly used unit, while kilowatts are more commonly used in other parts of the world.

5. What is the difference between engine power and torque?

Engine power and torque are often used interchangeably, but they are actually two different measurements. Engine power is a measure of how much work an engine can do in a given amount of time, while torque is a measure of the engine's rotational force. In simpler terms, power is how fast the engine can do work, while torque is the force that makes the engine do the work.

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